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Materials, Volume 16, Issue 19 (October-1 2023) – 271 articles

Cover Story (view full-size image): In this review, we focus on a small section of the literature that deals with the materials containing pristine defective carbon nanostructures (CNs) and those incorporated into the larger systems containing carbon atoms, heteroatoms, and inorganic components, and we focus mainly on the method using microwave (MW) irradiation, which is a powerful tool for synthesizing and modifying carbon-based solid materials due to its simplicity, the possibility of conducting the reaction in solvents and solid phases, and the presence of components of different chemical natures. Herein, we will emphasize the advantages of synthesis using MW-assisted heating and indicate the influence of the structure of the obtained materials on their physical and chemical properties. View this paper
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10 pages, 4088 KiB  
Article
Influence of Oil Viscosity on the Tribological Behavior of a Laser-Textured Ti6Al4V Alloy
by Marjetka Conradi, Aleksandra Kocijan and Bojan Podgornik
Materials 2023, 16(19), 6615; https://doi.org/10.3390/ma16196615 - 9 Oct 2023
Cited by 1 | Viewed by 1321
Abstract
Laser texturing with a dimple pattern was applied to modify a Ti6Al4V alloy at the micro level, aiming to improve its friction and wear resistance in combination with oil lubrication to optimize the performance in demanding industrial environments. The tribological analysis was performed [...] Read more.
Laser texturing with a dimple pattern was applied to modify a Ti6Al4V alloy at the micro level, aiming to improve its friction and wear resistance in combination with oil lubrication to optimize the performance in demanding industrial environments. The tribological analysis was performed on four different dimple-textured surfaces with varying dimple size and dimple-to-dimple distance and under lubrication with three different oils, i.e., T9, VG46, and VG100, to reflect the oil viscosity’s influence on the friction/wear of the laser-textured Ti6Al4V alloy. The results show that the surfaces with the highest texture density showed the most significant COF reduction of around 10% in a low-viscosity oil (T9). However, in high-viscosity oils (VG46 and VG100), the influence of the laser texturing on the COF was less pronounced. A wear analysis revealed that the laser texturing intensified the abrasive wear, especially on surfaces with a higher texture density. For low-texturing-density surfaces, less wear was observed for low- and medium-viscosity oils (T9 and VG46). For medium-to-high-texturing densities, the high-viscosity oil (VG100) provided the best contact conditions and wear results. Overall, reduced wear, even below the non-texturing case, was observed for sample 50–200 in VG100 lubrication, indicating the combined effect of oil reservoirs and increased oil-film thickness within the dimples due to the high viscosity. Full article
(This article belongs to the Section Materials Physics)
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Figure 1
<p>Sliding direction marked by an arrow.</p> Full article ">Figure 2
<p>SEM images (15.0 V, X200, WD 36.2) of analyzed dimple-laser-textured Ti6Al4V surfaces, 50–100, 50–200, 100–200, and 100–400; and below, the corresponding light microscopy images. The first number labels the dimple width, while the second number indicates the dimple-to-dimple distance. The inset in each SEM image shows the depth profile of the dimples.</p> Full article ">Figure 3
<p>SEM micrograph of a dimple on a 100–400 dimple-textured surface. The inset shows the details of the laser remelted layer.</p> Full article ">Figure 4
<p>Coefficient-of-friction curves for non-textured and all laser-textured Ti6Al4V samples (50–100, 50–200, 100–200, and 100–400) under T9 (<b>a</b>), VG46 (<b>b</b>), and VG100 (<b>c</b>) oil lubrication.</p> Full article ">Figure 5
<p>Steady-state coefficient of friction (COF) for non-textured and laser-textured Ti6Al4V surface under T9/VG46/VG100 oil lubrication.</p> Full article ">Figure 6
<p>SEM images (15.0V, X100, WD 32.2) of wear scars of non-textured (<b>a</b>,<b>f</b>,<b>k</b>) and laser-textured Ti6Al4V surfaces under T9 (<b>b</b>–<b>e</b>), VG46 (<b>g</b>–<b>j</b>) and VG100 (<b>l</b>–<b>o</b>) oil lubrication.</p> Full article ">Figure 7
<p>Wear volumes of non-textured and laser-textured Ti6Al4V surfaces under T9/VG46/VG100 oil lubrication.</p> Full article ">
20 pages, 4310 KiB  
Article
Composite Resins Impregnated by Phosphorus Organic Extractants for Separation of Rare Earth Elements from Nitrate-Based Leachate of Permanent Magnets
by Olga V. Kovalenko, Vladimir E. Baulin, Yuri M. Shulga, Dmitriy V. Baulin, Gennady L. Gutsev and Aslan Yu. Tsivadze
Materials 2023, 16(19), 6614; https://doi.org/10.3390/ma16196614 - 9 Oct 2023
Cited by 2 | Viewed by 1569
Abstract
Composite resins impregnated by different organophosphorus extractants were developed and used for the extraction chromatography recovery of rare earth elements from nitrate-based leachate of NdFeB permanent magnets. The influence of different factors on recovery of Nd(III) and Fe(III), as the most difficult to [...] Read more.
Composite resins impregnated by different organophosphorus extractants were developed and used for the extraction chromatography recovery of rare earth elements from nitrate-based leachate of NdFeB permanent magnets. The influence of different factors on recovery of Nd(III) and Fe(III), as the most difficult to separate elements, by developed resins was studied. The influence of extractant structure, the composition of feed solutions, and concentrations of HNO3 and NH4NO3 on the recovery of Fe(III) and Nd(III) by prepared resins were considered. The best recovery of Nd(III) was shown by resin impregnated with N,N-dioctyl (diphenylphosphoryl) acetamide. For this material, sorption characteristics (values of the distribution coefficient, capacity, and the Nd(III)/Fe(III) separation factor) were obtained, and the reproducibility of the loading–stripping process was evaluated. This resin and its precursors were characterized by IR spectroscopy. It was found that the developed resin is more efficient for Nd(III) recovery than resin impregnated with TODGA. An effective approach to the Nd(III)/Fe(III) separation with developed resin in nitrate solution was proposed. This approach was used for recovery of Pr(III), Nd(III), and Dy(III) from the nitrate-based leachate of NdFeB magnets by the developed resin. The final product contained 99.6% of rare earths. Full article
(This article belongs to the Collection Manufacturing Engineering and Mechanical Properties of Composite Materials)
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<p>The structures of extractants used in this research.</p> Full article ">Figure 2
<p>The calculated values of metal distribution coefficients using frontal loading curves; C/C<sub>0</sub> is the ratio of metal concentrations in eluate and feed solutions [<a href="#B40-materials-16-06614" class="html-bibr">40</a>]. 1 and 2 are frontal curves for two different metals.</p> Full article ">Figure 3
<p>Frontal loading curves of Nd(III), obtained with the following resins: 1 is for SIR 1; 2 is for SIR 2; 3 is for SIR 3; 4 is for SIR 4; 5 is for SIR 5. The SIR content is 600 ± 3 mg; the concentration of Nd(III) in the feed solution is 260.5 ± 0.3 mg/L; the flow rate is 1.0 mL/L.</p> Full article ">Figure 4
<p>The IR-spectrum of LPS-500.</p> Full article ">Figure 5
<p>IR spectra of compound <b>V</b> (red line) and SIR 5 (black line).</p> Full article ">Figure 6
<p>IR spectra of Nd(NO<sub>3</sub>)<sub>3</sub>∙6H<sub>2</sub>O (<b>A</b>) and SIR 5 saturated with Nd(III) (<b>B</b>).</p> Full article ">Figure 7
<p>IR spectra of SIR 5 saturated with Nd(III) (1), and initial SIR 5 (2). * mean peaks corresponding to P=O and C=O groups.</p> Full article ">Figure 8
<p>The influence of HNO<sub>3</sub> concentration on values of Fe(III) and Nd(III) distribution coefficients: 1 is for Nd(III) and 2 is for Fe(III) for SIR 5. The SIR content is 600 ± 3 mg; the concentration of Nd(III) in feed solution is 260.5 ± 0.3 mg/L; the flow rate is 1.0 mL/L.</p> Full article ">Figure 9
<p>Frontal loading curves of Fe(III) and Nd(III) in solutions of HNO<sub>3</sub> and NH<sub>4</sub>NO<sub>3</sub> for SIR 5; 1 is for Fe(III) in HNO<sub>3</sub>; 2 is for Fe(III) in NH<sub>4</sub>NO<sub>3</sub>; 3 is for Nd(III) in HNO<sub>3</sub>; 4 is for Nd(III) in NH<sub>4</sub>NO<sub>3</sub>. The SIR content is 600 ± 3 mg; the concentration of Nd(III) in feed solution is 260.5 ± 0.3 mg/L; the flow rate is 1.0 mL/L.</p> Full article ">Figure 10
<p>Dependence of values Kd of Fe(III) and Nd(III) on NH<sub>4</sub>NO<sub>3</sub> concentration for SIR 5: 1 is for Nd(III) and 2 is for Fe(III). The SIR content is 600±3 mg; the concentration of Nd(III) in feed solution is 260.5 ± 0.3 mg/L; the flow rate is 1.0 mL/L.</p> Full article ">Figure 11
<p>Dependence of distribution coefficient (D) on concentration of compound <b>V</b> (L): 1 is for Pr(III), 2 is for Nd(III), and 3 is for Dy(III).</p> Full article ">Figure 12
<p>Frontal loading curves of Nd(III) in NH<sub>4</sub>NO<sub>3</sub> of 1.0 mol/L: 1 is for SIR 5 and 2 is for SIR 6. The SIR content is 600 ± 3 mg; the concentration of Nd(III) in feed solution is 260.5 ± 0.3 mg/L; the flow rate is 1.0 mL/L.</p> Full article ">Figure 13
<p>Recovery of Fe(III) and Nd(III) from NH<sub>4</sub>NO<sub>3</sub> of 1.0 mol/L with resin impregnated by TODGA (SIR 6). The SIR content is 600 ± 3 mg; the concentration of Nd(III) in feed solution is 260.5 ± 0.3 mg/L; the flow rate is 1.0 mL/L.</p> Full article ">Figure 14
<p>Separation of Fe(III) (1) and Nd(III) (2) using resin SIR 5. The SIR content is 600 ± 3 mg; the concentration of Nd(III) in feed solution is 260.5 ± 0.3 mg/L; the flow rate is 1.0 mL/L.</p> Full article ">
18 pages, 5785 KiB  
Article
Development of a Novel High-Temperature Microemulsion for Enhanced Oil Recovery in Tight Oil Reservoirs
by Lixiao Xiao, Jirui Hou, Weiju Wang and Infant Raj
Materials 2023, 16(19), 6613; https://doi.org/10.3390/ma16196613 - 9 Oct 2023
Cited by 1 | Viewed by 1343
Abstract
This work focuses on the development of a novel high-temperature microemulsion for enhanced oil recovery in tight oil reservoirs. Microemulsions are a type of mixture that has properties of both liquids and solids; they have shown significant potential for improving oil recovery through [...] Read more.
This work focuses on the development of a novel high-temperature microemulsion for enhanced oil recovery in tight oil reservoirs. Microemulsions are a type of mixture that has properties of both liquids and solids; they have shown significant potential for improving oil recovery through spontaneous imbibition. Herein, a high-temperature-tolerant lower-phase microemulsion using a microemulsion dilution method was developed. The properties and morphological characteristics of the microemulsion were evaluated and proposed a mechanism for enhanced spontaneous imbibition oil recovery using imbibition tests and CT scanning technology. The results of the study showed that the optimum concentration of the microemulsion was 0.2 wt% and that it had good thermal stability, small droplet size, lower interfacial tension, good wettability alteration ability, and minimum adsorption loss. The imbibition and CT experiments demonstrated that the reduction in oil/solid adhesion was due to the synergistic effect of IFT reduction and wettability alteration and the ability to increase the imbibition distance through a larger self-driving force. The study concludes that the solubilization coefficient and self-driving force were defined and calculated to quantitatively analyze the imbibition mechanisms and the results showed that the reduction in oil/solid adhesion was due to the synergistic effect of IFT reduction and wettability alteration and the ability to increase the imbibition distance through a larger self-driving force. Full article
(This article belongs to the Special Issue Nano Technology Assistance in Operating and Enhancing Oil Recovery)
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Figure 1
<p>The process of preparing HTLP-ME.</p> Full article ">Figure 2
<p>(<b>a</b>) The microscopic morphology; (<b>b</b>) The count of the size distribution of HTLP-ME.</p> Full article ">Figure 3
<p>The turbidity of HTLP-ME variation with temperature.</p> Full article ">Figure 4
<p>The variation in the water-phase contact angle on quartz flakes with concentrations of HTLP-ME.</p> Full article ">Figure 5
<p>Effect of different HTLP-ME concentrations on the (<b>a</b>) dynamic IFT as a function of time and (<b>b</b>) the variation in equilibrium IFT.</p> Full article ">Figure 6
<p>Effect of HTLP-ME at different concentrations on W<sub>a</sub>.</p> Full article ">Figure 7
<p>Standard absorbance–concentration curve of HTLP-ME.</p> Full article ">Figure 8
<p>The static adsorption of HTLP-ME on the oil sand surface at different concentrations is about the (<b>a</b>) adsorption rate and (<b>b</b>) adsorption capacity.</p> Full article ">Figure 9
<p>Morphology characteristics of the oil–water mixture under a 10× microscope.</p> Full article ">Figure 10
<p>The changes in HTLP-ME’s droplet size (<b>a</b>) before and (<b>b</b>) after solubilizing the kerosene.</p> Full article ">Figure 11
<p>The schematic diagram of emulsification and solubilization of kerosene by HTLP-ME.</p> Full article ">Figure 12
<p>(<b>a</b>) The relationship of SIOR and Di with imbibition time; (<b>b</b>) The relationship between SIOR and Di.</p> Full article ">
13 pages, 8361 KiB  
Article
Study on Porosity of Thermal-Sprayed Commercially Pure Aluminum Coating
by Bo Li, Lei Fan, Jie Bai, Jinhang He, Jianfeng Su, Song Wang, Chao Deng, Shifeng Liu and Zhiqing Zhang
Materials 2023, 16(19), 6612; https://doi.org/10.3390/ma16196612 - 9 Oct 2023
Cited by 3 | Viewed by 1471
Abstract
Porosity is closely related to the corrosion and wear properties of a coating processed by thermal-spraying technology, and the quantitative characterization of porosity is a crucial part of the research on coating structures. The current image analysis method often uses the mechanical polishing [...] Read more.
Porosity is closely related to the corrosion and wear properties of a coating processed by thermal-spraying technology, and the quantitative characterization of porosity is a crucial part of the research on coating structures. The current image analysis method often uses the mechanical polishing method recommended by ISO to measure a coating porosity. This method has been proved to be an effective method for the characterization of oxide coatings. However, due to the significant differences in the physical and chemical properties between aluminum and oxides, this method may not be suitable for aluminum coatings, and a more appropriate approach needs to be explored. In this paper, the effects of three polishing technologies (mechanical polishing, argon-ion-beam polishing, and electrolytic polishing) on the porosity measurement of pure aluminum coatings were compared and studied. The research results showed that the commonly used mechanical polishing method and more advanced argon-ion-beam polishing method could not completely reveal the pore structure because SiC particles would be embedded in the pure aluminum coatings during mechanical polishing, filling large pores. Although electrolytic polishing technology had advantages in revealing the macroporous structure, it would introduce a microporous structure and oxides, which would affect the measurement of the coating porosity. The composite polishing technology (electrolytic polishing + argon-ion-beam polishing) could perfectly reveal the pore structure in the pure-aluminum coating, and the porosity of arc-sprayed aluminum coating was 9.9%, which was close to the macroscopic true value measured using the weighing method of 10.2%. Full article
(This article belongs to the Special Issue Research on Heat Treatment of Advanced Metallic Materials (2nd Volume))
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<p>Schematic diagrams of (<b>a</b>) the argon-ion-beam polishing and (<b>b</b>) the electrolytic polishing.</p> Full article ">Figure 2
<p>Surface morphology of the commercially pure aluminum coating after being mechanically ground and the resultant surface distribution of the corresponding elements.</p> Full article ">Figure 3
<p>Surface morphology of the commercially pure aluminum coating after fine polishing and the surface distribution of the corresponding elements.</p> Full article ">Figure 4
<p>Surface morphology of commercially pure aluminum coating after argon-ion-beam polishing and the surface distribution of the corresponding elements.</p> Full article ">Figure 5
<p>Surface morphology of commercially pure aluminum coating after electrolytic polishing (<b>a</b>) and enlarged surface morphology, and the corresponding surface distribution of the elements (<b>b</b>).</p> Full article ">Figure 6
<p>Enlarged surface morphology of commercially pure aluminum coating after electrolytic polishing.</p> Full article ">Figure 7
<p>Surface morphology of SiC particles in the commercially pure aluminum coating after argon-ion-beam polishing and the corresponding distribution of elements surface.</p> Full article ">Figure 8
<p>Surface morphology of the commercially pure aluminum coating after the composite polishing method and the corresponding distribution of surface elements (<b>a</b>), and the SEM image used for pore statistical analysis (<b>b</b>).</p> Full article ">
14 pages, 2830 KiB  
Article
Improved Interlaminar Properties of Glass Fiber/Epoxy Laminates by the Synergic Modification of Soft and Rigid Particles
by Jingwei Liu, Shenghui Tian, Jiaqi Ren, Jin Huang, Lin Luo, Bing Du and Tianyong Zhang
Materials 2023, 16(19), 6611; https://doi.org/10.3390/ma16196611 - 9 Oct 2023
Cited by 6 | Viewed by 1506
Abstract
Poor interlaminar fracture toughness has been a major issue in glass fiber-reinforced epoxy resin (GF/EP) laminate composites. In this paper, soft carboxy-terminated nitrile (CTBN) rubber particles and rigid nano-SiO2 are used to toughen the epoxy resin (EP) matrix to improve the interlayer [...] Read more.
Poor interlaminar fracture toughness has been a major issue in glass fiber-reinforced epoxy resin (GF/EP) laminate composites. In this paper, soft carboxy-terminated nitrile (CTBN) rubber particles and rigid nano-SiO2 are used to toughen the epoxy resin (EP) matrix to improve the interlayer properties of GF/EP laminate composites. The effects of adding two toughening agents on the mechanical and interlayer properties of GF/EP laminates were studied. The results showed that adding the two kinds of particles improved the mechanical properties of the epoxy matrix. When the additional amount of flexible CTBN rubber particles was 8 wt%, and the rigid nano-SiO2 was 0.5 wt%, the fracture toughness of the matrix resin was increased by 215.8%, and the tensile strength was only decreased by 2.3% compared with the pure epoxy resin. On this basis, the effects of two kinds of particles on the interlayer properties of GF/EP composites were studied. Compared with the unmodified GF/EP laminates, the interlayer shear strength and mode I interlayer fracture toughness is significantly improved by a toughening agent, and the energy release rate GIC of interlayer shear strength and interlayer fracture toughness is increased by 109.2%, and 86.8%, respectively. The flexible CTBN rubber particles and rigid nano-SiO2 improve the interfacial adhesion between GF and EP. The cavitation of the two particles and the plastic deformation of the matrix is the toughening mechanism of the interlayer properties of the composite. Such excellent interlaminar mechanical properties make it possible for GF/EP laminates to be widely used as engineering materials in various industries (e.g., aerospace, hydrogen energy, marine). Full article
(This article belongs to the Special Issue Lightweight and High-Strength Sandwich Panel)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic for the fabrication of GF/EP laminates (<b>a</b>) and CTBN- (<b>b</b>) or CTBN + SiO<sub>2</sub>- (<b>c</b>) modified GF/EP laminates.</p> Full article ">Figure 2
<p>Critical stress intensity factor (<span class="html-italic">K<sub>IC</sub></span>) (<b>a</b>) and tensile strength (<b>b</b>) of CTBN-modified epoxy resin matrix.</p> Full article ">Figure 3
<p>Critical stress intensity factor (<span class="html-italic">K<sub>IC</sub></span>) (<b>a</b>) and tensile strength (<b>b</b>) of epoxy resin matrix co-modified by CTBN and nano-SiO<sub>2</sub>.</p> Full article ">Figure 4
<p>SEM image of epoxy resin matrix I toughness test section with unmodified (<b>a</b>), 8 wt% CTBN (<b>b</b>), and 8 wt% CTBN + 0.5 wt% nanoSiO<sub>2</sub> (<b>c</b>).</p> Full article ">Figure 5
<p>Typical load–displacement curves (<b>a</b>) of GF/EP-laminated composites with or without CTBN or SiO<sub>2</sub> in the mode I interlayer stripping experiment and the average value of the calculated <span class="html-italic">G<sub>IC</sub></span><sub>,<span class="html-italic">Pro</span></sub> value (<b>b</b>).</p> Full article ">Figure 6
<p>Typical load–displacement curves (<b>left</b>) of GF/EP-laminated composites with or without CTBN or SiO<sub>2</sub> in the shear strength experiment and the saverage value (<b>right</b>) of the calculated shear strength of GF/EP-laminated composite toughened by SiO<sub>2</sub> and CTBN.</p> Full article ">Figure 7
<p>SEM image of mode I fracture toughness test (DCB specimen) of GF/EP-laminated composite material, which is not modified (<b>a</b>–<b>c</b>), modified (<b>d</b>–<b>f</b>) by 8 wt% CTBN, and co-modified (<b>g</b>–<b>i</b>) by 0.5 wt% nano-SiO<sub>2</sub> + 8 wt% CTBN.</p> Full article ">
16 pages, 9228 KiB  
Article
Residual Stress Control Using Process Optimization in Directed Energy Deposition
by Manping Cheng, Xi Zou, Yang Pan, Yan Zhou, Wenyang Liu and Lijun Song
Materials 2023, 16(19), 6610; https://doi.org/10.3390/ma16196610 - 9 Oct 2023
Cited by 2 | Viewed by 1460
Abstract
This paper mainly analyzes the typical thermodynamic response (thermal history, thermal strain and residual stress) in a conventional continuous-wave (CW) laser during Directed Energy Deposition (DED). The influence of process parameters (laser power and scanning speed) on the temperature gradient in the heat-affected [...] Read more.
This paper mainly analyzes the typical thermodynamic response (thermal history, thermal strain and residual stress) in a conventional continuous-wave (CW) laser during Directed Energy Deposition (DED). The influence of process parameters (laser power and scanning speed) on the temperature gradient in the heat-affected zone, thermal strain and residual stress are studied, and the corresponding relationship are established. The results show that a reduction in residual stress can be obtained by decreasing the temperature gradient. However, the method of reducing the temperature gradient by changing process parameters leads to low forming quality and low density. A pulse-wave laser (PW) is proposed to actively control the residual stress of the deposited sample. This laser mode can reduce not only the temperature gradient in the process of DED but also the in situ release of thermal stress, correspondingly greatly reducing the residual stress. Full article
(This article belongs to the Section Metals and Alloys)
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Figure 1
<p>(<b>a</b>) Schematic diagram of DED processing. (<b>b</b>) SEM image of 316L stainless steel powder.</p> Full article ">Figure 2
<p>(<b>a</b>) Sample size and scanning path. (<b>b</b>) Schematic diagram of continuous-wave (CW) laser and pulsed-wave (PW) laser.</p> Full article ">Figure 3
<p>Time-dependent temperature nephogram of S3 sample during deposition.</p> Full article ">Figure 4
<p>Time-dependent fitting temperature curve and temperature gradient of S3 sample during deposition.</p> Full article ">Figure 5
<p>Time-dependent temperature gradient under different laser process parameters. (<b>a</b>,<b>b</b>) the law of time-dependent temperature gradient in solid region under different laser power and scanning speed; (<b>c</b>,<b>d</b>) maximum temperature gradient in solid region under different laser power and scanning speed at 0.5 s.</p> Full article ">Figure 6
<p>Thermal strain nephogram of S3 sample during deposition: (<b>a</b>) 0.5 s; (<b>b</b>) 1.5 s; (<b>c</b>) 3.0 s.</p> Full article ">Figure 7
<p>Influence of process parameters on accumulated thermal strain: (<b>a</b>) laser power; (<b>b</b>) scanning speed.</p> Full article ">Figure 8
<p>Cloud diagram of residual stress distribution of S3 sample: (<b>a</b>) longitudinal residual stress; (<b>b</b>) transverse residual stress.</p> Full article ">Figure 9
<p>Influence of process parameters on maximum longitudinal residual stress of substrate: (<b>a</b>) laser power; (<b>b</b>) scanning speed.</p> Full article ">Figure 10
<p>Influence of laser power on longitudinal residual stress of the deposited sample: (<b>a</b>) S2 sample; (<b>b</b>) S3 sample; (<b>c</b>) S4 sample; (<b>d</b>) S9 sample.</p> Full article ">Figure 11
<p>Longitudinal residual stress along the height of the deposited sample.</p> Full article ">Figure 12
<p>Schematic diagram of changes in thermal strain during the DED process.</p> Full article ">Figure 13
<p>Relationship between temperature gradient, longitudinal strain (red square and arrow), residual stress (blue circle and arrow) in solid region.</p> Full article ">Figure 14
<p>Time-dependent temperature gradient in solid region during deposition of S3 and S9 samples.</p> Full article ">Figure 15
<p>Temperature history during deposition of S3 and S9 samples.</p> Full article ">Figure 16
<p>(<b>a</b>) Time-dependent thermal stress. (<b>b</b>) Schematic diagrams of thermal stress state during deposition of S3 and S9 samples.</p> Full article ">
16 pages, 11294 KiB  
Article
Insight into the Micro Evolution of Backfill Paste Prepared with Modified Gangue as Supplementary Cementitious Material: Dissolution and Hydration Mechanisms
by Binbin Huo, Jixiong Zhang, Meng Li and Qiang Guo
Materials 2023, 16(19), 6609; https://doi.org/10.3390/ma16196609 - 9 Oct 2023
Viewed by 1039
Abstract
Gangue-based backfill cementitious materials (BCM) are widely applied due to their low CO2 footprint, while the application is restricted by gangue’s low reactivity. In this study, dry chemical modification was developed to modify the gangue, and multiple characterized approaches were used to [...] Read more.
Gangue-based backfill cementitious materials (BCM) are widely applied due to their low CO2 footprint, while the application is restricted by gangue’s low reactivity. In this study, dry chemical modification was developed to modify the gangue, and multiple characterized approaches were used to characterize the dissolution property, mineral composition, and particle size distribution of modified gangue (MCG), as well as the compressive strength and microstructure of BCM. The findings show that the residue weight of MCG stabilized at 2 wt.% of formic acid, and the modification reduces the kaolinite and calcite, resulting in smaller particles. Additionally, the three days compressive strength of the BCM made with MCG was improved from 0.3 MPa to 0.6 MPa. Attributed to the increased reactivity of MCG, it was found that the dissolution weight increased by 2.13%. This study offers a novel method for activating gangue and a new kind of MCG-prepared BCM, which makes a significant contribution towards achieving the UN Sustainable Development Goals. Full article
(This article belongs to the Section Construction and Building Materials)
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<p>Flow chart of the research.</p> Full article ">Figure 2
<p>Particle size distribution of PC and CG.</p> Full article ">Figure 3
<p>XRD patterns of PC and CG.</p> Full article ">Figure 4
<p>Flow chart of the chemical modification process.</p> Full article ">Figure 5
<p>Flow chart of the dissolution process.</p> Full article ">Figure 6
<p>Dissolution property of CG at different (<b>a</b>) NaOH concentration, (<b>b</b>) dissolution time, and (<b>c</b>) temperature.</p> Full article ">Figure 7
<p>Dissolution property of MCG with different FC additions.</p> Full article ">Figure 8
<p>(<b>a</b>) XRD and (<b>b</b>) FTIR patterns of MCG with different FC additions.</p> Full article ">Figure 9
<p>SEM of MCG with different modifier additions.</p> Full article ">Figure 10
<p>(<b>a</b>) Particle size distribution and (<b>b</b>) BET result of MCG.</p> Full article ">Figure 11
<p>Compressive strength of BCM.</p> Full article ">Figure 12
<p>(<b>a</b>) XRD patterns of BCM at different ages and (<b>b</b>) mineral composition of BCM with CG reacted.</p> Full article ">Figure 13
<p>Microstructure of BCM.</p> Full article ">Figure 14
<p>Schematic diagram of modification CG and hydration of BCM.</p> Full article ">
13 pages, 2949 KiB  
Article
Fabrication and Characterization of a Multifunctional Coating to Promote the Osteogenic Properties of Orthopedic Implants
by Serap (Gungor) Koc, Tuba Baygar, Selma Özarslan, Nurdan Sarac and Aysel Ugur
Materials 2023, 16(19), 6608; https://doi.org/10.3390/ma16196608 - 9 Oct 2023
Cited by 1 | Viewed by 1565
Abstract
Titanium-based alloys are used in orthopedic applications as fixation elements, hard tissue replacements in artificial bones, and dental implants. Despite their wide range of applications, metallic implant defects and failures arise due to inadequate mechanical bonding, postoperative clotting problems, aseptic loosening, and infections. [...] Read more.
Titanium-based alloys are used in orthopedic applications as fixation elements, hard tissue replacements in artificial bones, and dental implants. Despite their wide range of applications, metallic implant defects and failures arise due to inadequate mechanical bonding, postoperative clotting problems, aseptic loosening, and infections. To improve the surface bioactivity and reduce the corrosion rate of the Ti6Al4V alloy, multi-layered coatings (HAp, BG, Cs, and Hep) were applied via electrophoretic deposition (EPD). XRD images showed the presence of HAp within the coating. In vitro investigation: cell line NIH-3T3 fibroblasts were seeded on the non-coated and coated Ti6Al4V substrates, and their cellular behavior was evaluated. The results indicated that the HApBGCsHep coating could enhance the adhesion and proliferation of NIH 3T3 cells. In addition, the potentiodynamic polarization results are compatible with the in vitro outcome. Full article
(This article belongs to the Special Issue Development of Bioactive Materials and Coatings for Biomedical Applications)
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<p>Flow chart showing the process of synthesizing of HAp and HApBG powder.</p> Full article ">Figure 2
<p>XRD pattern of S<sub>4</sub> (HApBGCsHep) coating.</p> Full article ">Figure 3
<p>SEM and SEM-EDX spectrum of (<b>a</b>) S<sub>2</sub>: HA+bioglass powder, (<b>a1</b>) S<sub>2</sub>: HA+bioglass powder EDX (<b>b</b>) S<sub>3</sub>: chitosan+heparin coating, (<b>b1</b>) S<sub>3</sub>: chitosan+heparin coating EDX (<b>c</b>) S<sub>4</sub>: HA+bioglass+chitosan+heparin powder, (<b>c1</b>) S<sub>4</sub>: HA+bioglass+chitosan+heparin powder EDX.</p> Full article ">Figure 4
<p>FTIR spectra of (<b>a</b>) S<sub>2</sub>: HA+bioglass, (<b>b</b>) S<sub>3</sub>: chitosan+heparin, (<b>c</b>) S<sub>4</sub>: HA+bioglass+chitosan+heparin coatings.</p> Full article ">Figure 5
<p>Cell viability of coated discs ((S<sub>1</sub> (uncoated), S<sub>2</sub> (HAp+bioglass), S<sub>3</sub> (chitosan+heparin), S<sub>4</sub> (HAp+bioglass+chitosan+heparin)). Values were expressed as the mean of five replicates (<span class="html-italic">n</span> = 5).</p> Full article ">Figure 6
<p>SEM morphologies of the 3T3 cells seeded on discs: (<b>a</b>) S<sub>1</sub> (uncoated), (<b>b</b>) S<sub>2</sub> (HAp+bioglass), (<b>c</b>) S<sub>3</sub> (chitosan+heparin) and (<b>d</b>) S<sub>4</sub> (HAp+bioglass+chitosan+heparin). Magnification is ×500 for large images and ×2500 form small images on top of each.</p> Full article ">Figure 7
<p>Potentiodynamic polarization curves for HAp, BG, Cs and Hep coatings. (S<sub>1</sub> (uncoated), S<sub>2</sub> (HAp+bioglass), S<sub>3</sub> (chitosan+heparin) and S<sub>4.</sub> (HAp+bioglass+chitosan+heparin)).</p> Full article ">
13 pages, 3891 KiB  
Article
Performance Improvement and Microstructure Characterization of Cement-Stabilized Roadbase Materials Containing Phosphogypsum/Recycled Concrete Aggregate
by Yang Wu, Xiaoya Bian, Jie Liu, Ruan Chi and Xuyong Chen
Materials 2023, 16(19), 6607; https://doi.org/10.3390/ma16196607 - 9 Oct 2023
Cited by 4 | Viewed by 1249
Abstract
The proper reutilization of the phosphogypsum (PG) by-product derived from the production of phosphoric acid and recycled concrete aggregate (RCA) from waste concrete in roadbase materials is of great necessity and importance. This investigation tried seeking a new approach to reuse them to [...] Read more.
The proper reutilization of the phosphogypsum (PG) by-product derived from the production of phosphoric acid and recycled concrete aggregate (RCA) from waste concrete in roadbase materials is of great necessity and importance. This investigation tried seeking a new approach to reuse them to high quality, including turning PG into calcinated PG (CPG) via washing and calcination, as well as adopting sodium metasilicate nonahydrate (SMN) to strengthen the roadbase materials of cement-stabilized CPG and RCA. Upon the mix design, with a series of experiments including unconfined compressive strength, the wet–dry cycle, freeze–thaw cycle, and scanning electron microscopy, the comprehensive effects of PG treatment, the CPG to RCA mix ratio, SMN dosage, wet–dry cycle and freeze–thaw cycle on the road performance of roadbase materials were well evaluated, and the traffic bearing capacity and microstructure characteristics were also analyzed. The results demonstrate that the 7 d unconfined compressive strength of CPG/RCA roadbase materials can reach 5.34 MPa as the CPG and SMN dosage are 20% and 11%, respectively, which meets the requirements of an extremely and very heavy traffic grade. After five wet–dry cycles and freeze–thaw cycles, the resistance of the CPG/RCA roadbase materials to moisture and frost was significantly improved as 11% SMN was added. Meanwhile, SMN contributes to the reduction in crack width and densifies the microstructure of CPG/RCA roadbase materials. The research results can be used to provide new guidance for building more durable roadbase materials. Full article
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<p>PG and CPG surface appearance.</p> Full article ">Figure 2
<p>Surface appearance of RCA.</p> Full article ">Figure 3
<p>The unconfined compressive strength test of samples.</p> Full article ">Figure 4
<p>The research flow chart of this study.</p> Full article ">Figure 5
<p>The 7 d and 28 d unconfined compressive strength of different CPG/RCA roadbase materials.</p> Full article ">Figure 6
<p>Effect of SMN contents on 7 d unconfined compressive strength for 20CPG-45RCA roadbase material.</p> Full article ">Figure 7
<p>Unconfined compressive strength of different PG/RCA roadbase materials.</p> Full article ">Figure 8
<p>Effect of wet–dry cycle on the 7 d unconfined compressive strength of PG/RCA roadbase material.</p> Full article ">Figure 9
<p>The effect of freeze–thaw cycles on the unconfined compressive strength of different PG/RCA roadbase materials cured for 28 d.</p> Full article ">Figure 10
<p>Effect of freeze–thaw cycles on residual compressive strength ratios of different PG/RCA roadbase materials.</p> Full article ">Figure 11
<p>Microstructural images of different PG/RCA roadbase materials. (<b>a</b>) 0CPG-57RCA; (<b>b</b>) 20PG-45RCA; (<b>c</b>) 20CPG-45RCA; (<b>d</b>) 20CPG-45RCA-11SMN).</p> Full article ">
23 pages, 5632 KiB  
Article
A Comparative Investigation of Machine Learning Algorithms for Pore-Influenced Fatigue Life Prediction of Additively Manufactured Inconel 718 Based on a Small Dataset
by Bing-Li Hu, Yan-Wen Luo, Bin Zhang and Guang-Ping Zhang
Materials 2023, 16(19), 6606; https://doi.org/10.3390/ma16196606 - 9 Oct 2023
Cited by 4 | Viewed by 1412
Abstract
Fatigue life prediction of Inconel 718 fabricated by laser powder bed fusion was investigated using a miniature specimen tests method and machine learning algorithms. A small dataset-based machine learning framework integrating thirteen kinds of algorithms was constructed to predict the pore-influenced fatigue life. [...] Read more.
Fatigue life prediction of Inconel 718 fabricated by laser powder bed fusion was investigated using a miniature specimen tests method and machine learning algorithms. A small dataset-based machine learning framework integrating thirteen kinds of algorithms was constructed to predict the pore-influenced fatigue life. The method of selecting random seeds was employed to evaluate the performance of the algorithms, and then the ranking of various machine learning algorithms for predicting pore-influenced fatigue life on small datasets was obtained by verifying the prediction model twenty or thirty times. The results showed that among the thirteen popular machine learning algorithms investigated, the adaptive boosting algorithm from the boosting category exhibited the best fitting accuracy for fatigue life prediction of the additively manufactured Inconel 718 using the small dataset, followed by the decision tree algorithm in the nonlinear category. The investigation also found that DT, RF, GBDT, and XGBOOST algorithms could effectively predict the fatigue life of the additively manufactured Inconel 718 within the range of 1 × 105 cycles on a small dataset compared to others. These results not only demonstrate the capability of using small dataset-based machine learning techniques to predict fatigue life but also may guide the selection of algorithms that minimize performance evaluation costs when predicting fatigue life. Full article
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<p>Schematic illustrations of (<b>a</b>) the scanning strategy with a 90° rotation between layers; (<b>b</b>) orientations, grouping, and dimensions of specimens extracted from LPBF-fabricated Inconel 718 block; (<b>c</b>) different pore features, including diameter, location, and number of pores; (<b>d</b>) symmetrical bending fatigue of cantilever beam specimen.</p> Full article ">Figure 2
<p>Strategy flowchart for ML techniques that use a small dataset to predict the pore-affected fatigue life of the AM-fabricated materials.</p> Full article ">Figure 3
<p>CDF diagrams of (<b>a</b>) strain amplitude (<span class="html-italic">ε</span>), (<b>b</b>) pore diameter (<span class="html-italic">d</span>), (<b>c</b>) pore amount (<span class="html-italic">m</span>), (<b>d</b>) pore location (<span class="html-italic">l</span>), and (<b>e</b>) fatigue life (<span class="html-italic">N</span>). The Y-axis represents the cumulative distribution values (CDV), and the X-axis represents the different pore features.</p> Full article ">Figure 4
<p>Gaussian distribution histograms and kernel density curves of the (<b>a</b>) strain amplitude (%), (<b>b</b>) pore diameter (µm), (<b>c</b>) pore amount (piece), (<b>d</b>) pore location (µm), and (<b>e</b>) fatigue life (cycles). The Q-Q plots of the (<b>f</b>) strain amplitude (%), (<b>g</b>) pore diameter (µm), (<b>h</b>) pore amount (piece), (<b>i</b>) pore location (µm), and (<b>j</b>) fatigue life (cycles), the circle points indicate the sample data.</p> Full article ">Figure 5
<p>Bland-Altman plot. (<b>a</b>) The <span class="html-italic">R</span><sup>2</sup> values of the training set and test set after normalization and/or Box-Cox transformation; (<b>b</b>) the <span class="html-italic">R</span><sup>2</sup> values after transformation and antitransformation on the test dataset. Mean represents the average value of the difference (Mean<sub>a</sub> = 0.0346, Mean<sub>b</sub> = 0.0152), and SD represents the standard deviation of the difference (SD<sub>a</sub> = 0.0684, SD<sub>b</sub> = 0.0556).</p> Full article ">Figure 6
<p>The normal stress distribution of as-built specimens with (<b>a</b>) smooth surfaces, (<b>b</b>) rough surfaces (Ra = 0.2 µm), and (<b>c</b>) rough surfaces (Ra = 0.4 µm), simulated by FEA (deflection = 0.65 mm).</p> Full article ">Figure 7
<p>The comparison results of the maximum normal stress distribution in the fixed end of the specimen with different surface roughness values.</p> Full article ">Figure 8
<p>The normal stress distribution of as-built specimens with different features of pores along cantilever specimens was simulated through FEA (deflection = 0.65 mm). Specimens with (<b>a</b>–<b>f</b>) 4 µm pore diameter, (<b>g</b>–<b>l</b>) 8 µm pore diameter, and (<b>m</b>–<b>r</b>) 16 µm pore diameter. l = x represents the distance (x) from the center of the pore to the surface along the thickness direction, such that l = 15 μm means the pore is located at the place with a distance to the surface at the fixed end of the specimen along the thickness direction. All the circular insets in the figures indicate the maximum normal stress on the cross section of the specimen with the pore.</p> Full article ">Figure 9
<p>Variation of the maximum stress in the beam specimens containing pores with locations (distance to the specimen surface) and sizes of the pores.</p> Full article ">Figure 10
<p>Evaluation performance of each ML algorithm on the test set.</p> Full article ">Figure 11
<p>The comparison between the experimental and predicted values. (<b>a</b>–<b>e</b>) Linear category, (<b>f</b>–<b>h</b>) nonlinear category, (<b>i</b>,<b>j</b>) bagging category, (<b>k</b>–<b>m</b>) boosting category.</p> Full article ">Figure 12
<p>Performance verification of each algorithm under different random seeds and evaluation indicators. (<b>a</b>,<b>b</b>) Linear regression category; (<b>c</b>,<b>d</b>) nonlinear regression category; (<b>e</b>,<b>f</b>) bagging algorithm category; (<b>g</b>,<b>h</b>) boosted algorithm category. Here, the random seeds of (<b>a</b>–<b>d</b>) are 5, 15, 25, 35, 45, 55, 65, 75, 85, and 95, and those of (<b>e</b>–<b>h</b>) are 5, 15, 25, 35, 45, 55, 65, 75, 85, 95,100, 500, 1000, 1500, and 2000.</p> Full article ">Figure 13
<p>The ranking results of different algorithms.</p> Full article ">
26 pages, 12118 KiB  
Article
Crashworthiness of Foam-Filled Cylindrical Sandwich Shells with Corrugated Cores
by Pengbo Su, Bin Han, Yiming Wang, Hui Wang, Bo Gao and Tian Jian Lu
Materials 2023, 16(19), 6605; https://doi.org/10.3390/ma16196605 - 9 Oct 2023
Viewed by 1180
Abstract
Inspired by material hybrid design, novel hybrid sandwich shells were developed by filling a corrugated cylindrical structure with aluminum foam to achieve higher energy absorption performance. The crushing behavior of the foam-filled corrugated sandwich cylindrical shells (FFCSCSs) was investigated using theoretical and numerical [...] Read more.
Inspired by material hybrid design, novel hybrid sandwich shells were developed by filling a corrugated cylindrical structure with aluminum foam to achieve higher energy absorption performance. The crushing behavior of the foam-filled corrugated sandwich cylindrical shells (FFCSCSs) was investigated using theoretical and numerical methods. Numerical results revealed a significant enhancement in the energy absorption of FFCSCSs under axial compression, showcasing a maximum specific energy absorption of 60 kJ/kg. The coupling strengthening effect is highly pronounced, with a maximum value of F¯c/F¯ reaching up to 40%. The mechanism underlying this phenomenon can be approached from two perspectives. Firstly, the intrusion of folds into the foam insertions allows for more effective foam compression, maximizing its energy absorption capacity. Secondly, foam causes the folds to bend upwards, intensifying the mutual compression between the folds. This coupling mechanism was further investigated with a focus on analyzing the influence of parameters such as the relative density of the foam, the wall thickness of the sandwich shell, and the material properties. Moreover, a theoretical model was developed to accurately predict the mean crushing force of the FFCSCSs. Based on this model, the influence of various variables on the crushing behavior of the structure was thoroughly investigated through parametric studies. Full article
(This article belongs to the Special Issue Characterizations, Mechanical Properties and Constitutive Modeling of Advanced Materials)
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<p>The FFCSCS is under crushing process.</p> Full article ">Figure 2
<p>Geometric schematic of foam-filled corrugated sandwich cylindrical shells.</p> Full article ">Figure 3
<p>The finite element model of the FFCSCS under axial compression condition.</p> Full article ">Figure 4
<p>Material properties and corresponding power-hardening model of parent materials for corrugated cores and face sheets: (<b>a</b>) 6063 Al [<a href="#B54-materials-16-06605" class="html-bibr">54</a>]; (<b>b</b>) 6061Al [<a href="#B54-materials-16-06605" class="html-bibr">54</a>]; (<b>c</b>) 304L stainless steel [<a href="#B67-materials-16-06605" class="html-bibr">67</a>].</p> Full article ">Figure 5
<p>Material properties of the filled foams with different relative densities (<math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math>).</p> Full article ">Figure 6
<p>Comparison between experiments [<a href="#B53-materials-16-06605" class="html-bibr">53</a>] and FE results of PMI foam-filled 1060 Al sandwich cylindrical shell: (<b>a</b>) force–displacement curves; (<b>b</b>) final collapse mode.</p> Full article ">Figure 7
<p>Crushing process and energy absorption of FFCSCS 6063-08-01: (<b>a</b>) force–displacement curves; (<b>b</b>) energy absorption–displacement curves; (<b>c</b>) collapse configurations with labels corresponding to those marked in the force–displacement curves.</p> Full article ">Figure 8
<p>Coupling enhancement effect in FFCSCS 6063-08-01: (<b>a</b>) force–displacement; (<b>b</b>) mean crushing force–displacement curves.</p> Full article ">Figure 9
<p>Collapse configuration of the FFCSCS 6063-08-01.</p> Full article ">Figure 10
<p>The formation process of folds (enclosed by the red dash circle) in FFCSCS (6063-08-01): (<b>a</b>) initial stage; (<b>b</b>) beginning of formation; (<b>c</b>) bending upwards; (<b>d</b>) compressing each other; (<b>e</b>) partially enlarged view of (<b>c</b>); (<b>f</b>) partially enlarged view of (<b>d</b>).</p> Full article ">Figure 11
<p>Crushing response of FFSCSCs with different relative foam density <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math>: (<b>a</b>) force–displacement curves for <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math> = 0.06~0.14; (<b>b</b>) force–displacement curves for <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math> = 0.16~0.19; (<b>c</b>) mean crushing force–displacement curves for <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math> = 0.06~0.14; (<b>d</b>) mean crushing force–displacement curves for <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math> = 0.16~0.19.</p> Full article ">Figure 12
<p>Collapse configuration of FFSCSCs with <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math> values ranging from 0.08 to 0.19: (<b>a</b>) 0.08; (<b>b</b>) 0.10; (<b>c</b>) 0.12; (<b>d</b>) 0.14; (<b>e</b>) 0.16; (<b>f</b>) 0.19.</p> Full article ">Figure 13
<p>Composition of the mean crushing force (<math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math>) for FFCSCSs with <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math> = 0.06~0.19: (<b>a</b>) absolute value; (<b>b</b>) proportion in <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math>.</p> Full article ">Figure 14
<p>Influence of wall thickness and relative density of foam on the crushing properties of FFCSCSs: (<b>a</b>) mean crushing force, <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math> (<b>b</b>) coupling mean crushing force, <math display="inline"><semantics> <mrow> <msub> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> <mrow> <mi mathvariant="normal">c</mi> </mrow> </msub> </mrow> </semantics></math>; (<b>c</b>) crushing force efficiency, <span class="html-italic">A</span><sub>E</sub>; (<b>d</b>) specific energy absorption, SEA.</p> Full article ">Figure 15
<p>Composition of the mean crushing force for FFSCSCs with different wall thicknesses and relative densities of foam: (<b>a</b>) absolute value; (<b>b</b>) proportion in <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math>.</p> Full article ">Figure 16
<p>Influence of wall material and relative density of foam on the crushing properties of FFCSCs: (<b>a</b>) mean crushing force, <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math>; (<b>b</b>) coupling mean crushing force, <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math>; (<b>c</b>) crushing force efficiency, <span class="html-italic">A</span><sub>E</sub>; (<b>d</b>) specific energy absorption, SEA.</p> Full article ">Figure 17
<p>Composition of the mean crushing force for FFSCSCs with different wall materials and relative densities of foam: (<b>a</b>) absolute value; (<b>b</b>) proportion in <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math>.</p> Full article ">Figure 18
<p>Comparison of theoretical predicated and finite element results: (<b>a</b>) coupling mean crushing force, <math display="inline"><semantics> <mrow> <msub> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> <mrow> <mi mathvariant="normal">c</mi> </mrow> </msub> </mrow> </semantics></math>; (<b>b</b>) mean crushing force, <math display="inline"><semantics> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> </semantics></math>.</p> Full article ">Figure 19
<p>Theoretical predictions of mean crushing force of FFCSCSs with equal mass: (<b>a</b>) 1060 Al face sheets with different <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math>; (<b>b</b>) 6063 Al face sheets with different <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math>; (<b>c</b>) 6061 Al face sheets with different <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math>; (<b>d</b>) 304L stainless steel face sheets with different <math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>ρ</mi> <mo>¯</mo> </mover> <mi mathvariant="normal">f</mi> </msub> </mrow> </semantics></math>.</p> Full article ">Figure 20
<p>Proportion of mean crushing force of FFSCSCs: (<b>a</b>) <math display="inline"><semantics> <mrow> <msub> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> <mrow> <mi mathvariant="normal">s</mi> </mrow> </msub> </mrow> </semantics></math>; (<b>b</b>) <math display="inline"><semantics> <mrow> <msub> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> <mrow> <mi mathvariant="normal">f</mi> </mrow> </msub> </mrow> </semantics></math>; (<b>c</b>) <math display="inline"><semantics> <mrow> <msub> <mrow> <mover accent="true"> <mrow> <mi>F</mi> </mrow> <mo>¯</mo> </mover> </mrow> <mrow> <mi mathvariant="normal">c</mi> </mrow> </msub> </mrow> </semantics></math>.</p> Full article ">
23 pages, 8913 KiB  
Article
Eco-Friendly Sustainable Concrete and Mortar Using Coal Dust Waste
by Evgenii M. Shcherban’, Sergey A. Stel’makh, Alexey N. Beskopylny, Levon R. Mailyan, Besarion Meskhi, Diana Elshaeva, Andrei Chernil’nik, Alexander L. Mailyan and Oxana Ananova
Materials 2023, 16(19), 6604; https://doi.org/10.3390/ma16196604 - 9 Oct 2023
Cited by 7 | Viewed by 2229
Abstract
Finding the solution to the problem of the accumulating waste from the mining and processing industries, as well as reducing their carbon footprint, is among the most important tasks today. Within the construction industry, in the field of the production of building materials [...] Read more.
Finding the solution to the problem of the accumulating waste from the mining and processing industries, as well as reducing their carbon footprint, is among the most important tasks today. Within the construction industry, in the field of the production of building materials such as concrete, these problems may be solved through the use of waste and by saving the binder component. The purpose of this study is to substantiate the feasibility of using waste coal dust (CD) in concrete and cement–sand mortars as a partial replacement for cement. Test samples were made by partially replacing cement with CD in an amount from 0% to 10% in increments of 2% by weight. The following main characteristics were studied: mobility and density of mixtures, as well as density, compressive strength, bending strength and water absorption of concrete and mortars. X-ray diffraction and microscopic analysis methods were used in this work. The introduction of CD to replace part of the cement, up to 10%, did not have a significant effect on the density of concrete and mortar mixtures but reduced their workability. The best values of physical and mechanical characteristics were recorded for concrete and mortar with 4% CD. The increases in the compressive strength of concrete and mortars were 6.6% and 5.7%, and in flexural strength 6.1% and 5.6%, respectively. Water absorption decreased by 9.7% for concrete and by 9.3% for mortar. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (3rd Edition))
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<p>Distribution curve of coal dust particles.</p> Full article ">Figure 2
<p>X-ray pattern of coal dust.</p> Full article ">Figure 3
<p>Experimental program.</p> Full article ">Figure 4
<p>Dependence of the density of the concrete mixture on the CD content (the dashed line shows confidence limits with a level of 0.95).</p> Full article ">Figure 5
<p>Dependence of mobility of concrete mixture on CD content.</p> Full article ">Figure 6
<p>Change in mortar density depending on CD content (the dashed line shows confidence limits with a level of 0.95).</p> Full article ">Figure 7
<p>Change in mortar mobility depending on CD content (the dashed line shows confidence limits with a level of 0.95).</p> Full article ">Figure 8
<p>Dependence of concrete density on CD content (the dashed line shows confidence limits with a level of 0.95).</p> Full article ">Figure 9
<p>Change in mortar density depending on CD content (the dashed line shows confidence limits with a level of 0.95).</p> Full article ">Figure 10
<p>Change in compressive strength (R) of concrete depending on CD content.</p> Full article ">Figure 11
<p>Change in compressive strength (R) of the mortar depending on the CD content.</p> Full article ">Figure 12
<p>Dependence of concrete flexural strength (R<sub>tb</sub>) on CD content.</p> Full article ">Figure 13
<p>Change in the flexural strength of the mortar depending on the CD content.</p> Full article ">Figure 14
<p>Change in water absorption of concrete depending on CD content.</p> Full article ">Figure 15
<p>Change in water absorption of the mortar depending on the CD content.</p> Full article ">Figure 16
<p>X-ray image of concrete of the control composition.</p> Full article ">Figure 17
<p>X-ray diffraction pattern of concrete with a CD content of 4%.</p> Full article ">
14 pages, 7949 KiB  
Article
A Numerical and Experimental Analysis of the Mechanical Behavior of the Aluminum Beverage Can with Internal Varnish Layers during Axial Load Force Testing
by Przemysław Wędrychowicz, Piotr Kustra and Andrij Milenin
Materials 2023, 16(19), 6603; https://doi.org/10.3390/ma16196603 - 9 Oct 2023
Cited by 1 | Viewed by 1711
Abstract
This article presents a numerical and experimental investigation into the impact of can wall thickness and the internal varnish layer thickness on the results of an axial load force test. This study also shows the levels of thermal stresses that emerge after the [...] Read more.
This article presents a numerical and experimental investigation into the impact of can wall thickness and the internal varnish layer thickness on the results of an axial load force test. This study also shows the levels of thermal stresses that emerge after the drying of varnish coating, and how they affect the results of the axial load force test. This research involves the development of suitable numerical models and the experimental acquisition of stress–deformation relationships for the both can material, aluminum, and the varnish. The numerical simulation of the axial load force test has been verified through experimental tests, with a resulting difference of 8.9% between the two sets of results. The findings highlight that changes in the can wall thickness have a more pronounced effect on test outcomes compared to variations in the varnish thickness. Specifically, an increase in the can wall thickness from 90 µm to 100 µm results in a substantial 116 N increase in the force required for a can to collapse. Nevertheless, the presence of a 5 µm varnish layer also contributes measurably, increasing the can’s collapse force by 21 N. These results offer valuable practical insights for manufacturers, enabling them to effectively optimize can strength characteristics. Full article
(This article belongs to the Special Issue Mechanical Properties and Characterization of Metallic Materials for Lightweight Structures)
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<p>Internal spray application nozzles.</p> Full article ">Figure 2
<p>Internal varnish: (<b>a</b>) sample for the uniaxial compression test; (<b>b</b>) results from seven uniaxial compression test.</p> Full article ">Figure 3
<p>Sample according to PN-EN 10002-1 + AC1 used in the uniaxial tensile test of aluminum alloy 3104 H19.</p> Full article ">Figure 4
<p>Tensile specimen edge picture after: (<b>a</b>) water jet cut; (<b>b</b>) milling.</p> Full article ">Figure 5
<p>Surface parameters according to ISO 25178 for: (<b>a</b>) water jet cut specimen; (<b>b</b>) milling specimen.</p> Full article ">Figure 6
<p>Tensile test results of aluminum alloy 3104 H19 (PN-EN 10002-1 + AC1 standard sample).</p> Full article ">Figure 7
<p>Axial load force test boundary condition visualization.</p> Full article ">Figure 8
<p>Fragment of cross-sectional views of the numerical model for the can: (<b>a</b>) without the internal varnish layer; (<b>b</b>) with the internal 5 μm varnish layer.</p> Full article ">Figure 9
<p>Results of the cooling simulation from 200 °C to 20 °C; (<b>a</b>) whole can body picture; (<b>b</b>) aluminum—max principal stress values in MPa; (<b>c</b>) varnish—max principal stress values in MPa, (<b>d</b>) aluminum—min principal stress values in MPa; (<b>e</b>) varnish—min principal stress values in MPa.</p> Full article ">Figure 10
<p>Comparison of simulation and experiment results in the axial load force test for a can with a 95 μm aluminum wall and a 5 μm internal varnish layer.</p> Full article ">Figure 11
<p>Failure mode of a beverage can for the ALF test comparison; (<b>a</b>) simulation; (<b>b</b>) experiment.</p> Full article ">Figure 12
<p>Comparison of the can body behavior under axial loading force for a can with a 5 μm varnish layer and a can without varnish (can models without flange).</p> Full article ">Figure 13
<p>Von Mises stress distribution on the can: (<b>a</b>–<b>c</b>) model without varnish; (<b>d</b>–<b>f</b>) model with a 5 μm varnish layer; (<b>a</b>,<b>d</b>) before can sidewall buckling; (<b>b</b>,<b>e</b>) after can sidewall buckling; (<b>c</b>,<b>f</b>) after some time of can sidewall buckling.</p> Full article ">Figure 14
<p>Can flange deformation region during the axial load force test.</p> Full article ">Figure 15
<p>Simulation results of can body behavior under axial loading force for models with and without a flange.</p> Full article ">
9 pages, 2113 KiB  
Communication
Lone-Pair-Enabled Polymorphism and Photostructural Changes in Chalcogenide Glasses
by Alexander V. Kolobov, Vladimir G. Kuznetsov, Milos Krbal and Stanislav V. Zabotnov
Materials 2023, 16(19), 6602; https://doi.org/10.3390/ma16196602 - 9 Oct 2023
Cited by 1 | Viewed by 1309
Abstract
S- and Se-based chalcogenide glasses are intrinsically metastable and exhibit a number of photo-induced effects unique to this class of materials, reversible photostructural changes and photo-induced anisotropy being major examples. These effects are usually interpreted in terms of the formation of valence alternation [...] Read more.
S- and Se-based chalcogenide glasses are intrinsically metastable and exhibit a number of photo-induced effects unique to this class of materials, reversible photostructural changes and photo-induced anisotropy being major examples. These effects are usually interpreted in terms of the formation of valence alternation pairs and ‘wrong’ bonds. In this work, using density functional theory simulations, we demonstrate for the case example of As2S3 that a strong decrease in the optical band gap can be achieved if a polymorphic transformation of the local structure from orpiment to that of tetradymite takes place. For the formation of the latter, the presence of lone-pair electrons in near-linear atomic configurations is crucial. Our results represent a novel approach to understanding the photo-induced structural changes in chalcogenide glasses as being due to the presence of polymorphism, and will lead to their wider use in various photonic devices. Full article
(This article belongs to the Special Issue Advances in Optoelectronic Functional Thin Films)
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<p>The orpiment (<b>a</b>) and tetradymite (<b>b</b>) structures of <math display="inline"><semantics> <mrow> <msubsup> <mi mathvariant="normal">A</mi> <mn>2</mn> <mi mathvariant="normal">V</mi> </msubsup> <msubsup> <mi mathvariant="normal">B</mi> <mn>3</mn> <mi>VI</mi> </msubsup> </mrow> </semantics></math>. Pnictogen atoms are shown in violet and chalcogen atoms are yellow.</p> Full article ">Figure 2
<p>In silico melt-quenched amorphous <math display="inline"><semantics> <mrow> <msub> <mi>As</mi> <mn>2</mn> </msub> <msub> <mi mathvariant="normal">S</mi> <mn>3</mn> </msub> </mrow> </semantics></math>. In addition to fragments satisfying the 8–N rule, linear fragments marked by brighter colours and As-S-As-S squares are clearly visible.</p> Full article ">Figure 3
<p>Phonon dispersion spectra calculated for the tetradymite phase of <math display="inline"><semantics> <mrow> <msub> <mi>As</mi> <mn>2</mn> </msub> <msub> <mi mathvariant="normal">S</mi> <mn>3</mn> </msub> </mrow> </semantics></math>. The presence of imaginary modes (shown as negative in the plot) is an indication of the phase instability.</p> Full article ">Figure 4
<p>Calculated densities of states around the Fermi level for the orpiment and tetradymite phases demonstrate a significantly smaller band gap for the tetradymite phase. The inset shows the simulated absorption edges for the two phases with that for the tetradymite phase shifted to smaller energies, which corresponds to darkening.</p> Full article ">Figure 5
<p>Schematics of the photo-induced structural change in the <math display="inline"><semantics> <mrow> <msub> <mi>As</mi> <mn>2</mn> </msub> <msub> <mi mathvariant="normal">S</mi> <mn>3</mn> </msub> </mrow> </semantics></math> glass. Arsenic atoms are shown in violet and S atoms are yellow. (<b>a</b>)—ground state, (<b>b</b>)—photodarkened state.</p> Full article ">
17 pages, 10857 KiB  
Article
Comparison of Microstructure and Mechanical Properties of Ultra-Narrow Gap Metal Active Gas Arc Welded and Narrow Gap Submerged Arc Welded Q235A Low Carbon Steel
by Shang Wu, Wenkai Xiao, Lingfei Gong and Fuju Zhang
Materials 2023, 16(19), 6601; https://doi.org/10.3390/ma16196601 - 9 Oct 2023
Viewed by 1557
Abstract
The 18 mm thick Q235A low carbon steel plates were welded via the ultra-narrow gap metal active gas arc welding (ultra-NGMAGW) and narrow gap submerged arc welding (NGSAW), and the microstructure and mechanical properties of the welded joints’ area were characterized. The results [...] Read more.
The 18 mm thick Q235A low carbon steel plates were welded via the ultra-narrow gap metal active gas arc welding (ultra-NGMAGW) and narrow gap submerged arc welding (NGSAW), and the microstructure and mechanical properties of the welded joints’ area were characterized. The results showed that there is acicular ferrite (AF) in the weld zone of the joint obtained via the ultra-NGMAGW. The AF grains are fine and have a great difference in growth direction, resulting in high local dislocation density. However, there is no AF in the welded joint obtained via the NGSAW. Using numerical simulation analysis of the temperature field distribution and the thermal cycle curve in the welding process of the ultra-NGMAGW, it was found that the mechanism of microstructure evolution is that during the welding process of the ultra-NGMAGW, the heat input is low, the cooling rate is quick, and the residence time in the high temperature region is short. Therefore, pearlite with coarse grains is basically not formed. AF nucleates in different directions with inclusions as the core. The tensile strength of the weld joint obtained via the ultra-NGMAGW is 643 MPa, which corresponds to 139% of that of the base metal, and 132% of that obtained via the NGSAW. The ultra-NGMAGW joints exhibited better tensile strength and higher microhardness than the NGSAW joints, which is mainly due to the existence of AF. Full article
(This article belongs to the Special Issue Welding and Joining Processes of Metallic Materials)
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<p>Microstructure of Q235A base metal.</p> Full article ">Figure 2
<p>Schematic diagram of the ultra-NGMAGW device.</p> Full article ">Figure 3
<p>Schematic diagram of the ultra-NGMAGW welding groove.</p> Full article ">Figure 4
<p>Cut position and size of tensile specimen: (<b>a</b>) sampling position of the ultra-NGMAGW; (<b>b</b>) sampling position of the NGSAW; and (<b>c</b>) sample size (mm).</p> Full article ">Figure 5
<p>Q235A thick plate joint finite element model. (<b>a</b>) weld cross-section; (<b>b</b>) weld surface.</p> Full article ">Figure 6
<p>Cross-section profiles and its 50× enlarged view of Q235A welded joints: (<b>a</b>) cross-section profiles of Ultra-NGMAGW; (<b>b</b>) cross-section profiles of NGSAW; (<b>c</b>) enlarged view of Ultra-NGMAGW; and (<b>d</b>) enlarged view of NGSAW.</p> Full article ">Figure 7
<p>Microstructure of Q235A weld zone: (<b>a</b>) OM of ultra-NGMAGW; (<b>b</b>) SEM of ultra-NGMAGW; (<b>c</b>) OM of NGSAW; and (<b>d</b>) SEM of NGSAW.</p> Full article ">Figure 8
<p>Microstructure of Q235A HAZ: (<b>a</b>) OM of ultra-NGMAGW; (<b>b</b>) SEM of ultra-NGMAGW; (<b>c</b>) OM of NGSAW; and (<b>d</b>) SEM of NGSAW.</p> Full article ">Figure 9
<p>Microhardness measurements on the welded joint (WZ: weld center; HAZ: heat-affected zone; BM: base material): (<b>a</b>) ultra-NGMAGW, and (<b>b</b>) NGSAW.</p> Full article ">Figure 10
<p>Tensile specimen after fracture.</p> Full article ">Figure 11
<p>Representative engineering stress versus engineering strain curves for BM, and Ultra-NGMAGW and NGSAW Q235A joints.</p> Full article ">Figure 12
<p>SEM micrographs of the tensile fracture surfaces of (<b>a</b>) BM; (<b>b</b>) ultra-NGMAGW; and (<b>c</b>) NGSAW.</p> Full article ">Figure 13
<p>Inverse pole figure and grain size distribution diagram at the WZ: (<b>a</b>) inverse pole figure of the ultra-NGMAGW joint; (<b>b</b>) inverse pole figure of the NGSAW joint; (<b>c</b>) grain size distribution diagram of the ultra-NGMAGW joint; and (<b>d</b>) grain size distribution diagram of the NGSAW joint.</p> Full article ">Figure 13 Cont.
<p>Inverse pole figure and grain size distribution diagram at the WZ: (<b>a</b>) inverse pole figure of the ultra-NGMAGW joint; (<b>b</b>) inverse pole figure of the NGSAW joint; (<b>c</b>) grain size distribution diagram of the ultra-NGMAGW joint; and (<b>d</b>) grain size distribution diagram of the NGSAW joint.</p> Full article ">Figure 14
<p>Adjacent grain boundary misorientation distribution map and angle statistical map at the WZ: (<b>a</b>) adjacent grain boundary misorientation distribution map of ultra-NGMAGW joint; (<b>b</b>) adjacent grain boundary misorientation distribution map of the NGSAW; (<b>c</b>) angle statistical map of the ultra-NGMAGW; and (<b>d</b>) angle statistical map of the NGSAW.</p> Full article ">Figure 15
<p>The distribution diagram of the KAM and statistical diagram of dislocation density in the WZ: (<b>a</b>) the KAM of the ultra-NGMAGW; (<b>b</b>) the KAM of the NGSAW; and (<b>c</b>) the statistical diagram of dislocation density in the ultra-NGMAGW and NGSAW.</p> Full article ">Figure 16
<p>(<b>a</b>) EDS spectrum for the ultra-NGMAGW welded joints, and (<b>b</b>) EDS spectrum for the NGSAW welded joints.</p> Full article ">Figure 16 Cont.
<p>(<b>a</b>) EDS spectrum for the ultra-NGMAGW welded joints, and (<b>b</b>) EDS spectrum for the NGSAW welded joints.</p> Full article ">Figure 17
<p>Temperature distribution of welded joint: (<b>a</b>) first weld; (<b>b</b>) second weld; and (<b>c</b>) third weld.</p> Full article ">Figure 18
<p>Welding thermal simulation of thermal cycle curve in the weld zone: (<b>a</b>) the first weld; (<b>b</b>) second weld; and (<b>c</b>) third weld.</p> Full article ">
20 pages, 10567 KiB  
Article
Mesoscopic Analysis of Rounded and Hybrid Aggregates in Recycled Rubber Concrete
by Mahmoud M. A. Kamel, Yu Fu, Xiaowei Feng and Yijiang Peng
Materials 2023, 16(19), 6600; https://doi.org/10.3390/ma16196600 - 8 Oct 2023
Viewed by 1341
Abstract
Recycled rubber concrete (RRC), a sustainable building material, provides a solution to the environmental issues posed by rubber waste. This research introduces a sophisticated hybrid random aggregate model for RRC. The model is established by combining convex polygon aggregates and rounded rubber co-casting [...] Read more.
Recycled rubber concrete (RRC), a sustainable building material, provides a solution to the environmental issues posed by rubber waste. This research introduces a sophisticated hybrid random aggregate model for RRC. The model is established by combining convex polygon aggregates and rounded rubber co-casting schemes with supplemental tools developed in MATLAB and Fortran for processing. Numerical analyses, based on the base force element method (BFEM) of the complementary energy principle, are performed on RRC’s uniaxial tensile and compressive behaviors using the proposed aggregate models. This study identified the interfacial transition zone (ITZ) around the rubber as RRC’s weakest area. Here, cracks originate and progress to the aggregate, leading to widespread cracking. Primary cracks form perpendicular to the load under tension, whereas bifurcated cracks result from compression, echoing conventional concrete’s failure mechanisms. Additionally, the hybrid aggregate model outperformed the rounded aggregate model, exhibiting closer peak strengths and more accurate aggregate shapes. The method’s validity is supported by experimental findings, resulting In detailed stress–strain curves and damage contour diagrams. Full article
(This article belongs to the Special Issue Mechanical Behavior of Concrete Materials and Structures: Experimental Evidence and Analytical Models (Volume II))
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<p>Planar four-node element.</p> Full article ">Figure 2
<p>The main program flow chart of the BFEM.</p> Full article ">Figure 3
<p>Mesostructure of recycled rubber concrete rounded aggregate.</p> Full article ">Figure 4
<p>Random round aggregate model of recycled rubber concrete.</p> Full article ">Figure 5
<p>Mesostructure of recycled rubber concrete convex aggregate.</p> Full article ">Figure 6
<p>Polygonal aggregate generation process.</p> Full article ">Figure 7
<p>Hybrid random aggregate model of recycled rubber concrete.</p> Full article ">Figure 8
<p>Recycled rubber concrete projection mesh model.</p> Full article ">Figure 9
<p>Bilinear damage model.</p> Full article ">Figure 10
<p>Multi-linear mechanical constitutive model of materials.</p> Full article ">Figure 11
<p>Model diagram: (<b>a</b>) rounded aggregate model; (<b>b</b>) hybrid aggregate model.</p> Full article ">Figure 12
<p>Tensile loading model.</p> Full article ">Figure 13
<p>Compressive loading model.</p> Full article ">Figure 14
<p>Normalized stress–strain curve of recycled rubber concrete under uniaxial tension.</p> Full article ">Figure 15
<p>Uniaxial tensile damage diagram depicting mortar, aggregate, and rubber in grey, red, and blue, respectively: (<b>a</b>) 80% peak stress; (<b>b</b>) peak stress; (<b>c</b>) 60% peak stress (post peak); (<b>d</b>) 10% peak stress (post peak).</p> Full article ">Figure 16
<p>Uniaxial tensile maximum principal stress contour map: (<b>a</b>) 80% peak stress; (<b>b</b>) peak stress; (<b>c</b>) 60% peak stress (post peak); (<b>d</b>) 10% peak stress (post peak).</p> Full article ">Figure 17
<p>Uniaxial tensile maximum principal strain contour map: (<b>a</b>) 80% peak stress; (<b>b</b>) peak stress; (<b>c</b>) 60% peak stress (post peak); (<b>d</b>) 10% peak stress (post peak).</p> Full article ">Figure 18
<p>Normalized stress–strain curve of recycled rubber concrete under uniaxial compression.</p> Full article ">Figure 19
<p>Uniaxial compressive damage diagram depicting mortar, aggregate, and rubber in grey, red, and blue, respectively: (<b>a</b>) 35% peak stress; (<b>b</b>) 80% peak stress; (<b>c</b>) peak stress; (<b>d</b>) 40% peak stress (post peak).</p> Full article ">Figure 20
<p>Uniaxial compressive maximum principal stress contour map: (<b>a</b>) 35% peak stress; (<b>b</b>) 80% peak stress; (<b>c</b>) peak stress; (<b>d</b>) 40% peak stress (post peak).</p> Full article ">Figure 21
<p>Uniaxial compressive maximum principal strain contour map: (<b>a</b>) 35% peak stress; (<b>b</b>) 80% peak stress; (<b>c</b>) peak stress; (<b>d</b>) 40% peak stress (post peak).</p> Full article ">
15 pages, 2639 KiB  
Article
An Orthogonal Test Study on the Preparation of Self-Compacting Underwater Non-Dispersible Concrete
by Haibin Geng, Huijuan Wang, Xiaoke Li, Lin Wang, Hao Zhong and Changyong Li
Materials 2023, 16(19), 6599; https://doi.org/10.3390/ma16196599 - 8 Oct 2023
Cited by 3 | Viewed by 1303
Abstract
To ensure a limited washout loss rate and the self-compaction of underwater concrete, the mix proportion design of underwater non-dispersible concrete is a key technology that has not been completely mastered. In view of this aspect, an orthogonal test study was carried out [...] Read more.
To ensure a limited washout loss rate and the self-compaction of underwater concrete, the mix proportion design of underwater non-dispersible concrete is a key technology that has not been completely mastered. In view of this aspect, an orthogonal test study was carried out in this paper on the workability, washout resistance, and compressive strength of underwater non-dispersible concrete. Six factors with five levels were considered, which included the water/binder ratio, the sand ratio, the maximum particle size of the coarse aggregate, the content of the dispersion resistance agent, the content of superplasticizer, and the dosage of fly ash. Using a range and variance analysis, the sensitivity and significance of these factors were analyzed on the slump and slump-flow, the flow time, the washout loss rate, the pH value, and the compressive strength at the curing ages of 7 days and 28 days. The results indicated that the water/binder ratio and the content of the dispersion resistance agent were strong in terms of their sensitivity and significance on the workability and washout resistance, and the water/binder ratio and the dosage of fly ash were strong in terms of their sensitivity and significance on the compressive strength. With the joint fitness of the test results, formulas for predicting the slump-flow, washout loss rate, and compressive strength of underwater non-dispersible concrete were proposed considering the main impact factors. Full article
(This article belongs to the Special Issue Advance in Sustainable Construction and Building Materials (2nd Edition))
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<p>Devise for washout loss test of UNC.</p> Full article ">Figure 2
<p>Relationships of flow time with slump flow of fresh UNC.</p> Full article ">Figure 3
<p>Relationships of performance indicators of UNC: (<b>a</b>) slump flow and washout loss; and (<b>b</b>) pH value and washout loss.</p> Full article ">Figure 4
<p>Relationships of the compressive strength of UNC at 7 d and 28 d.</p> Full article ">Figure 5
<p>Various trends in the mean values <span class="html-italic">k</span><sub>i</sub> of properties at different factor levels: (<b>a</b>) slump; (<b>b</b>) slump flow; and (<b>c</b>) <span class="html-italic">T</span><sub>400</sub>.</p> Full article ">Figure 6
<p>Various trends in the mean values <span class="html-italic">k</span><sub>i</sub> of anti-dispersion at different factor levels: (<b>a</b>) <span class="html-italic">M</span><sub>loss</sub>; and (<b>b</b>) pH value.</p> Full article ">Figure 7
<p>Various trends in the mean values <span class="html-italic">k</span><sub>i</sub> of compressive strength at different factor levels: (<b>a</b>) <span class="html-italic">f</span><sub>cu,7</sub>; and (<b>b</b>) <span class="html-italic">f</span><sub>cu,28</sub>.</p> Full article ">Figure 8
<p>Comprehensive impact of test factors on workability and anti-dispersion performance: (<b>a</b>) effect of <span class="html-italic">w/b</span> and <span class="html-italic">P</span><sub>ADA</sub> on <span class="html-italic">SF</span>; and (<b>b</b>) effect of <span class="html-italic">w/b</span> and <span class="html-italic">P</span><sub>ADA</sub> on <span class="html-italic">M</span><sub>loss</sub>.</p> Full article ">Figure 9
<p>Coupling effect of <span class="html-italic">w/b</span> and <span class="html-italic">P</span><sub>ADA</sub> on <span class="html-italic">SF</span> and <span class="html-italic">M</span><sub>loss</sub>.</p> Full article ">Figure 10
<p>Comprehensive impact of <span class="html-italic">w/b</span> and <span class="html-italic">P</span><sub>FA</sub> on <span class="html-italic">f</span><sub>cu,28</sub>.</p> Full article ">
14 pages, 4102 KiB  
Article
Facile Synthesis of Mesoporous Nanohybrid Two-Dimensional Layered Ni-Cr-S and Reduced Graphene Oxide for High-Performance Hybrid Supercapacitors
by Ravindra N. Bulakhe, Anh Phan Nguyen, Changyoung Ryu, Ji Man Kim and Jung Bin In
Materials 2023, 16(19), 6598; https://doi.org/10.3390/ma16196598 - 8 Oct 2023
Cited by 6 | Viewed by 1477
Abstract
This study describes the single-step synthesis of a mesoporous layered nickel-chromium-sulfide (NCS) and its hybridization with single-layered graphene oxide (GO) using a facile, inexpensive chemical method. The conductive GO plays a critical role in improving the physicochemical and electrochemical properties of hybridized NCS/reduced [...] Read more.
This study describes the single-step synthesis of a mesoporous layered nickel-chromium-sulfide (NCS) and its hybridization with single-layered graphene oxide (GO) using a facile, inexpensive chemical method. The conductive GO plays a critical role in improving the physicochemical and electrochemical properties of hybridized NCS/reduced GO (NCSG) materials. The optimized mesoporous nanohybrid NCSG is obtained when hybridized with 20% GO, and this material exhibits a very high specific surface area of 685.84 m2/g compared to 149.37 m2/g for bare NCS, and the pore diameters are 15.81 and 13.85 nm, respectively. The three-fold superior specific capacity of this optimal NCSG (1932 C/g) is demonstrated over NCS (676 C/g) at a current density of 2 A/g. A fabricated hybrid supercapacitor (HSC) reveals a maximum specific capacity of 224 C/g at a 5 A/g current density. The HSC reached an outstanding energy density of 105 Wh/kg with a maximum power density of 11,250 W/kg. A 4% decrement was observed during the cyclic stability study of the HSC over 5000 successive charge–discharge cycles at a 10 A/g current density. These results suggest that the prepared nanohybrid NCSG is an excellent cathode material for gaining a high energy density in an HSC. Full article
(This article belongs to the Special Issue Novel Nanomaterials for Energy Storage and Catalysis)
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<p>(<b>a</b>) X-ray powder diffraction spectra for NCS and all NCSG samples; high-resolution X-ray photoelectron spectroscopy spectra of (<b>a′</b>) C, (<b>b</b>,<b>b′</b>) Ni, (<b>c</b>,<b>c′</b>) Cr, and (<b>d</b>,<b>d′</b>) S elements of NCS and NCSG-2 samples, respectively.</p> Full article ">Figure 2
<p>(<b>a</b>) Field-emission scanning electron microscopy images of bare NiCr<sub>2</sub>S<sub>4</sub> (NCS), (<b>b</b>) nanohybrid NCS with 20% graphene oxide (NCSG-2), (<b>c</b>,<b>d</b>) transmission electron microscopy (TEM) images, (<b>e</b>) high-resolution TEM image, (<b>f</b>,<b>g</b>) additional high-resolution TEM images corresponding to the areas shown in <a href="#materials-16-06598-f002" class="html-fig">Figure 2</a>e marked in red and yellow, respectively, and (<b>h</b>) selected area electron diffraction pattern of the NCSG-2 nanohybrid sample.</p> Full article ">Figure 3
<p>(<b>a</b>) Adsorption-desorption isotherm plot and (<b>b</b>) Barret–Joyner–Halenda (BJH) desorption pore-size distribution plot for NiCr<sub>2</sub>S<sub>4</sub> (NCS) and NCS with 20% graphene oxide (NCSG-2).</p> Full article ">Figure 4
<p>(<b>a</b>) Combined cyclic voltammetry (CV) graphs of NiCr<sub>2</sub>S<sub>4</sub> (NCS) and NCS with 10%, 20%, and 30% graphene oxide (NCSG-1, NCSG-2, and NCSG-3) at a 20 mV/s scan rate; (<b>b</b>) CV graph of the NCS electrode (2–20 mV/s); (<b>c</b>) CV graphs of the NCSG-2 electrode (2–20 mV/s); (<b>d</b>) charge–discharge (CD) curves of the NCS electrode (2–6 A/g); (<b>e</b>) CD curves of the NCSG-2 electrode (2–6 A/g); and (<b>f</b>) graph of the current density vs. specific capacity of the NCS, NCSG-1, NCSG-2, and NCSG-3 electrodes, respectively.</p> Full article ">Figure 5
<p>Complete hybrid supercapacitor (HSC) study: (<b>a</b>) combined cyclic voltammetry (CV) graphs from 0.8 to 1.6 V potential windows with a 100 mV/s scan rate; (<b>b</b>) combined charge–discharge (CD) curves from 0.8 to 1.6 V potential window with a 6 A/g current density; (<b>c</b>) graph of potential variation with specific capacity (black color) and energy density (red color); (<b>d</b>) CV curves from 5 to 100 mV/s of the scan rate; (<b>e</b>) CD curves from 5 to 10 A/g of the current density; (<b>f</b>) graph of the current density vs. specific capacity; (<b>g</b>) Ragone plot; (<b>h</b>) Nyquist plot; and (<b>i</b>) Capacity retention obtained from continuous 5000 CD cycles for HSC cell.</p> Full article ">Scheme 1
<p>Synthesis process of Ni-Cr-S/reduced graphene oxide (NCSG).</p> Full article ">
15 pages, 2473 KiB  
Review
Review of the Influence of Acrylate Lotion on the Properties of Cement-Based Materials
by Fuyun Su, Haiyan Wang, Xiaodong Ma, Tingshu He and Yike Lin
Materials 2023, 16(19), 6597; https://doi.org/10.3390/ma16196597 - 8 Oct 2023
Cited by 2 | Viewed by 1503
Abstract
Polymer-modified cement-based materials have been widely used in the construction field. Acrylate lotion significantly improves durability, toughness, and bending resistance, especially durability, because the porosity of cement-based materials is reduced, preventing the entry of harmful ions and water. When acrylate lotion was at [...] Read more.
Polymer-modified cement-based materials have been widely used in the construction field. Acrylate lotion significantly improves durability, toughness, and bending resistance, especially durability, because the porosity of cement-based materials is reduced, preventing the entry of harmful ions and water. When acrylate lotion was at 20%, the resistance of cement-based materials to chloride ion penetration increased by 40%. At the same time, the fracture toughness of cement-based materials modified with acrylate lotion and carbon nanotubes increased by 10–15%. The flexural strength of cement-based materials modified by acrylate lotion and fiber increased by 29%. Additives such as TiO2 have a unique impact on the modification of cement-based materials, which has attracted the interest of researchers. This paper reviewed the performance of acrylate lotion-modified cement-based materials and the application of acrylate lotion in the field, which systematically increased the durability, mechanical properties, and waterproof properties of cement-based materials when acrylate lotion was modified, acrylate lotion was modified with nanomaterials, acrylate lotion was modified with other polymers, acrylate lotion was modified with fiber, and when acrylate lotion was modified with other additives. The shortcomings of acrylate lotion modification with different materials were reviewed and evaluated, and the comprehensive performance of cement-based materials modified by acrylate lotion was expected to achieve maximum strength improvement under the synergistic effect of various modifications. Full article
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<p>Scanning electron microscopy (SEM) image of cement paste sample. (<b>a</b>) Inorganic cement paste; (<b>b</b>) polymer lotion cement paste [<a href="#B59-materials-16-06597" class="html-bibr">59</a>].</p> Full article ">Figure 2
<p>Schematic diagram of the effect of nano SiO<sub>2</sub> on the microstructure of cement [<a href="#B64-materials-16-06597" class="html-bibr">64</a>].</p> Full article ">Figure 3
<p>Schematic diagram of SAE-modified mortar and SAE composite-modified mortar. (<b>a</b>) SAE-5; (<b>b</b>) SAE 5-SO1; (<b>c</b>) SAE-15; (<b>d</b>) SAE15-SO1 [<a href="#B53-materials-16-06597" class="html-bibr">53</a>].</p> Full article ">Figure 4
<p>Reinforced composite materials (R-FRC) prepared with different regenerated fibers [<a href="#B100-materials-16-06597" class="html-bibr">100</a>].</p> Full article ">Figure 5
<p>SEM image of cement slurry. (<b>a</b>) Cement paste; (<b>b</b>) cement paste after coating with composite lotion [<a href="#B103-materials-16-06597" class="html-bibr">103</a>].</p> Full article ">
14 pages, 3689 KiB  
Article
Contribution of Various Loads to the Convex Shape of Rock Wool Insulation Slabs during Production
by Jurij Hladnik and Boris Jerman
Materials 2023, 16(19), 6596; https://doi.org/10.3390/ma16196596 - 8 Oct 2023
Viewed by 952
Abstract
Rock wool insulation slabs are produced in special curing ovens, where molten rock wool fibres coated with binder are compressed between two slat conveyors and blown with hot air for vitrification. Often, the cross-section of the final slabs is slightly convex, which is [...] Read more.
Rock wool insulation slabs are produced in special curing ovens, where molten rock wool fibres coated with binder are compressed between two slat conveyors and blown with hot air for vitrification. Often, the cross-section of the final slabs is slightly convex, which is undesirable. The degree of convexity depends on the deformation of the steel crossbars of the slat conveyors, which are subjected to combined pressure and nonlinear temperature loadings. Due to this complex loading state, it is difficult to determine the contribution of individual load to the total deformation. The main aim of the study was to determine these contributions. Temperature and stress measurements of the crossbars were performed during rock wool production. Upon collecting these measurements, a finite element (FE) model of a crossbar was established for the identification of the pressure loading acting on the crossbars, and finally for determination of their deformations. As a main result of the study, an inverse problem-based methodology for the identification of the deflection of a structure due to unknown temperature and pressure loadings was established and applied on the specific case. The deviations between the deformations of the FE crossbars and the final shape of the rock wool slabs were below 10%, which validates the novel methodology. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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<p>(<b>a</b>) Upper and lower slat conveyor inside the curing oven with designated <span class="html-italic">L</span> coordinate along the lower conveyor and local coordinate system XYZ (Crossbar CS) of an arbitrary crossbar. The grey dotted arrows represent the hot air blowing directions (I., II., III. and IV.), point A represents the position where the measuring instrument was stopped, and the sensors were reconnected. (<b>b</b>) Exaggerated deformation of the crossbars leading to the convex shape of the rock wool. (<b>c</b>) A crossbar with annotated main parts and its corresponding local coordinate system XYZ.</p> Full article ">Figure 2
<p>Preparation of the crossbars in the laboratory. (<b>a</b>) The stress crossbar equipped with strain gauges. (<b>b</b>) Close view of a full-bridge strain gauge sensor on the stress crossbar. (<b>c</b>) Processed crossbar for insertion of the data acquisition measuring instrument. (<b>d</b>) The data acquisition measuring instrument embedded in the insulation box.</p> Full article ">Figure 3
<p>FE model of a crossbar loaded with uniform pressure <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>q</mi> </mrow> <mrow> <mi>x</mi> </mrow> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>q</mi> </mrow> <mrow> <mi>y</mi> </mrow> </msub> </mrow> </semantics></math>, and with a non-uniform temperature filed. The temperature loading presented in °C was established upon the average temperature differences measured in the deeper observed area.</p> Full article ">Figure 4
<p>Normalized temperatures in the temperature crossbar along part of the lower conveyor (2nd measurement turn). MP—measuring point; DOA—deeply observed area. The dotted grey arrows designate the hot air blowing directions (I., II., III. and IV.). The distance along the conveyor is expressed as a portion of the total conveyor’s length <span class="html-italic">L<sub>tot</sub></span> (see <a href="#materials-16-06596-f001" class="html-fig">Figure 1</a>a).</p> Full article ">Figure 5
<p>Dependence of the average normalized temperatures along the <span class="html-italic">z</span>-direction of the crossbar (2nd lamella) at two different <span class="html-italic">x</span> locations in the deeper observed area. The <span class="html-italic">x</span> and <span class="html-italic">z</span> dimension are presented as portion of <span class="html-italic">H</span> and <span class="html-italic">B</span>, respectively (see <a href="#materials-16-06596-f001" class="html-fig">Figure 1</a>c).</p> Full article ">Figure 6
<p>Average temperature difference in the middle of the 2nd lamella (z = 0) depending on the <span class="html-italic">x</span>-direction of the crossbar in the deeper observed area. The <span class="html-italic">x</span> dimension is presented as a portion of <span class="html-italic">H</span> (see <a href="#materials-16-06596-f001" class="html-fig">Figure 1</a>c).</p> Full article ">Figure 7
<p>Normalized longitudinal stresses <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>σ</mi> </mrow> <mrow> <mi>z</mi> <mi>z</mi> </mrow> </msub> </mrow> </semantics></math> in the stress crossbar along part of the lower conveyor (2nd measurement turn). MP—measuring point, DOA—deeply observed area. The dotted grey arrows designate the hot air blowing directions (I., II., III. and IV.). The distance along the conveyor is expressed as a portion of the total conveyor’s length <span class="html-italic">L<sub>tot</sub></span> (see <a href="#materials-16-06596-f001" class="html-fig">Figure 1</a>a).</p> Full article ">Figure 8
<p>The average thickness difference of the final rock wool slabs along their transverse direction and the vertical deformation of the crossbar FE model due to temperature and pressure loading separately, combined, and duplicated.</p> Full article ">
22 pages, 8858 KiB  
Article
Delamination Behavior of CFRP Laminated Plates under the Combination of Tensile Preloading and Impact Loading
by Kaiwei Lan, Haodong Wang and Cunxian Wang
Materials 2023, 16(19), 6595; https://doi.org/10.3390/ma16196595 - 8 Oct 2023
Cited by 1 | Viewed by 1265
Abstract
When subjected to impact loading, aircraft composite structures are usually in a specific preloading condition (such as tension and compression). In this study, ballistic tests were conducted using a high-speed gas gun system to investigate the effect of biaxial in-plane tensile preload on [...] Read more.
When subjected to impact loading, aircraft composite structures are usually in a specific preloading condition (such as tension and compression). In this study, ballistic tests were conducted using a high-speed gas gun system to investigate the effect of biaxial in-plane tensile preload on the delamination of CFRP laminates during high-speed impact. These tests covered central and near-edge locations for both unloaded and preloaded targets, with the test speeds including 50 m/s, 70 m/s, and 90 m/s. The delamination areas, when impacting the center location under 1000 με, show a 14.2~36.7% decrease. However, the cases when impacting the near-edge location show no more than a 19.3% decrease, and even more delamination areas were observed. In addition, in order to enhance the understanding of experimental phenomena, numerical simulations were conducted using the ABAQUS/Explicit solver, combined with the user subroutine VUMAT with modified Hou criteria. The experimental and simulation results were in good agreement, and the maximum error was approximately 12.9%. The results showed that not only the preloading value but also the impact velocity have significant influences on the delamination behavior of preloaded CFRP laminated plates. Combining detailed discussions, the biaxial tensile preload enhanced the resistance to out-of-plane displacement and caused laminate interface stiffness degradation. By analyzing the influence of the preloading value and impact velocity on competing mechanisms between the stress-stiffening effect and interface stiffness degradation effect, the complex delamination behaviors of laminates under various preloading degrees and impact velocities at different impact locations were reasonably explained. Full article
(This article belongs to the Special Issue Dynamic Behavior of Advanced Materials and Structures)
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<p>Configuration of preloading fixture and strain measurement scheme.</p> Full article ">Figure 2
<p>Schematic representation of a single-stage compressed gas gun system.</p> Full article ">Figure 3
<p>Typical high-speed photographs of CFRP laminated plates impacted by sphere steel projectile under the speed of 50 m/s; (<b>a</b>) impact on point 1 (center location); (<b>b</b>) impact on point 2 (near-edge location).</p> Full article ">Figure 4
<p>Delamination areas of CFRP laminated plates under various biaxial tensile preloads at impact speeds of 50 m/s, 70 m/s, and 90 m/s; (<b>a</b>,<b>b</b>) delamination areas of [0/90]<sub>8</sub> plates and [0/90/+45/−45]<sub>2S</sub> plates under 50 m/s; (<b>c</b>,<b>d</b>) delamination areas of [0/90]<sub>8</sub> plates and [0/90/+45/−45]<sub>2S</sub> plates under 70 m/s; (<b>e</b>,<b>f</b>) delamination areas of [0/90]<sub>8</sub> plates and [0/90/+45/−45]<sub>2S</sub> plates under 90 m/s.</p> Full article ">Figure 5
<p>In-plane strain histories and strain amplitudes of CFRP laminated plates under various biaxial tensile preloads; (<b>a</b>–<b>c</b>) typical in-plane strain histories at impact speeds of 50 m/s, 70 m/s, and 90 m/s; (<b>d</b>–<b>f</b>) strain amplitudes calculated from in-plane strain histories at impact speeds of 50 m/s, 70 m/s, and 90 m/s.</p> Full article ">Figure 6
<p>Enhancement mechanism of resistance to out-of-plane displacement for CFRP laminated plates when applying in-plane tensile preloads; (<b>a</b>,<b>b</b>) “V” shape caused by longitudinal wave and transverse wave with and without tensile preloads; (<b>c</b>,<b>d</b>) bending degree of plates with and without tensile preloads.</p> Full article ">Figure 7
<p>Typical photographs, taken with the high-speed camera, of the impact process and rebound process of the projectile.</p> Full article ">Figure 8
<p>Energy absorption rates of CFRP laminated plates under various biaxial tensile preloads at impact speeds of 50 m/s, 70 m/s, and 90 m/s; (<b>a</b>) energy absorption rates when impacting point 1; (<b>b</b>) energy absorption rates when impacting point 2.</p> Full article ">Figure 9
<p>Mesh for L × W = (300 × 300) mm<sup>2</sup> laminated plate; (<b>a</b>) impact on point 1 (center location); (<b>b</b>) impact on point 2 (near-edge location).</p> Full article ">Figure 10
<p>In-plane strain distributions along the horizontal and vertical direction of preloaded [0/90]<sub>8</sub> laminated plates.</p> Full article ">Figure 11
<p>Comparison of typical strain histories between experiments and simulations; (<b>a</b>) strain gauge 4 on [0/90]<sub>8</sub> plate; (<b>b</b>) strain gauge 2 on [0/90/+45/−45]<sub>2S</sub> plate; (<b>c</b>) strain gauge 1 on [0/90/+45/−45]<sub>2S</sub> plate; (<b>d</b>) strain gauge 3 on [0/90]<sub>8</sub> plate.</p> Full article ">Figure 12
<p>Comparison of typical delamination between experiments and simulations; (<b>a</b>) impact on point 1 of 1000 με preloaded [0/90]<sub>8</sub> plates at speeds of 50 m/s; (<b>b</b>) impact on point 2 of 1000 με preloaded [0/90/+45/−45]<sub>2S</sub> plates at speeds of 50 m/s; (<b>c</b>) impact on point 1 of 1000 με preloaded [0/90]<sub>8</sub> plates at speeds of 70 m/s; (<b>d</b>) impact on point 2 of 500 με preloaded [0/90/+45/−45]<sub>2S</sub> plates at speeds of 70 m/s; (<b>e</b>) impact on point 1 of 1000 με preloaded [0/90/+45/−45]<sub>2S</sub> plates at speeds of 70 m/s; (<b>f</b>) impact on point 1 of unloaded [0/90]<sub>8</sub> plates at speeds of 90 m/s.</p> Full article ">Figure 13
<p>Numerical delamination areas of CFRP laminated plates under various biaxial tensile preloads when impacting different positions. (<b>a</b>,<b>b</b>) delamination areas of [0/90]<sub>8</sub> plates and [0/90/+45/−45]<sub>2S</sub> plates under 50 m/s; (<b>c</b>,<b>d</b>) delamination areas of [0/90]<sub>8</sub> plates and [0/90/+45/−45]<sub>2S</sub> plates under 70 m/s; (<b>e</b>,<b>f</b>) delamination areas of [0/90]<sub>8</sub> plates and [0/90/+45/−45]<sub>2S</sub> plates under 90 m/s.</p> Full article ">Figure 14
<p>Stiffness degradation of [0/90]<sub>8</sub> CFRP laminated plates under various biaxial tensile preloads.</p> Full article ">Figure 15
<p>Schematic diagram of stiffness degradation for interface layer based on bilinear constitutive model; (<b>a</b>) bilinear constitutive model; (<b>b</b>) stiffness degradation for the interface layer.</p> Full article ">Figure 16
<p>Stiffness degradations output by Python software based on simulations; (<b>a</b>) [0/90]<sub>8</sub> plates; (<b>b</b>) [0/90/+45/−45]<sub>2S</sub> plates.</p> Full article ">Figure 17
<p>Numerical delamination areas and stress-stiffening effect mechanism under different impact velocities; (<b>a</b>) numerical delamination areas when impacting different positions of [0/90]<sub>8</sub> plates under different impact velocities; (<b>b</b>) stress-stiffening effect mechanism under different impact velocities.</p> Full article ">
33 pages, 7212 KiB  
Article
Numerical Analysis of the Freezing Behavior of Saturated Cementitious Materials with Different Amounts of Chloride
by Sekandar Zadran, Joško Ožbolt and Serena Gambarelli
Materials 2023, 16(19), 6594; https://doi.org/10.3390/ma16196594 - 8 Oct 2023
Cited by 1 | Viewed by 1400
Abstract
The freezing behavior of cement paste saturated with different chloride concentrations is investigated numerically with a coupled 3D hygro-thermo-mechanical FE analysis. The mathematical formulation of the freezing processes in the context of poromechanics takes into account the water (hydraulic) and ice pore pressures, [...] Read more.
The freezing behavior of cement paste saturated with different chloride concentrations is investigated numerically with a coupled 3D hygro-thermo-mechanical FE analysis. The mathematical formulation of the freezing processes in the context of poromechanics takes into account the water (hydraulic) and ice pore pressures, as well as the distribution of heat (temperature) and strains. These quantities are calculated numerically based on three coupled differential equations, namely the static equilibrium equation and the equations for the transport of water and heat. The coupling between the mechanical (loading) and the non-mechanical processes (freezing) is performed using a staggered solution scheme. The proposed numerical approach is first validated using numerical and experimental studies from the literature dealing with two different cement pastes saturated with different amounts of chloride. The validated model is then used to investigate the effects of liquid water permeability, total porosity and pore size distribution on the freezing behavior of hardened cement paste. The results show that liquid water permeability has a strong effect on the pore pressure and deformation of the hardened cement paste. It is also shown that by decreasing the total porosity, the material becomes denser and contracts more as the temperature decreases, leading to a decrease in freezing strain. The results of this paper will provide important findings for the development of a simplified engineering model to investigate the mechanism that leads to freeze–thaw salt-induced damage to concrete structures in the framework of the DFG-funded research project. Full article
(This article belongs to the Special Issue Durability Studies on the Concrete and Related Composites)
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<p>Effect of chloride concentration on the equilibrium pore radius: (<b>a</b>) relationship between chloride concentration and contact angle by Lide [<a href="#B36-materials-16-06594" class="html-bibr">36</a>]; (<b>b</b>) relationship between chloride concentration and activity of water by Lin [<a href="#B37-materials-16-06594" class="html-bibr">37</a>].</p> Full article ">Figure 2
<p>Evolution of equilibrium pore radius with varying chloride concentrations and temperatures.</p> Full article ">Figure 3
<p>FE model: (<b>a</b>) mechanical boundary condition; (<b>b</b>) environmental boundary condition.</p> Full article ">Figure 4
<p>Temperature–time variation for the first cooling phase.</p> Full article ">Figure 5
<p>Pore size distribution of PI and PII cement pastes.</p> Full article ">Figure 6
<p>The comparison between the freezing strains of the current study and experimental and numerical results from Zeng [<a href="#B9-materials-16-06594" class="html-bibr">9</a>] for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 1.5% NaCl; (<b>c</b>) 3% NaCl; (<b>d</b>) 6% NaCl; (<b>e</b>) 10% NaCl; (<b>f</b>) 15% NaCl.</p> Full article ">Figure 7
<p>Arbitrary nodes for freezing-induced liquid, ice and pore pressure.</p> Full article ">Figure 8
<p>The comparison between the pore pressure of four selected nodes for PI cement paste during the first cooling phase with respect to temperature variation: (<b>a</b>) pure water; (<b>b</b>) 1.5% NaCl; (<b>c</b>) 3% NaCl; (<b>d</b>) 6% NaCl; (<b>e</b>) 10% NaCl; (<b>f</b>) 15% NaCl.</p> Full article ">Figure 9
<p>The comparison between the pore pressure of the seven selected nodes in terms of distance and time step for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 1.5% NaCl; (<b>c</b>) 3% NaCl; (<b>d</b>) 6% NaCl; (<b>e</b>) 10% NaCl; (<b>f</b>) 15% NaCl.</p> Full article ">Figure 9 Cont.
<p>The comparison between the pore pressure of the seven selected nodes in terms of distance and time step for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 1.5% NaCl; (<b>c</b>) 3% NaCl; (<b>d</b>) 6% NaCl; (<b>e</b>) 10% NaCl; (<b>f</b>) 15% NaCl.</p> Full article ">Figure 10
<p>The comparison between the ice pressure of four selected nodes for PI cement paste during the first cooling phase with respect to temperature variation: (<b>a</b>) pure; (<b>b</b>) 15% NaCl.</p> Full article ">Figure 11
<p>The comparison between the ice pressure of the seven selected nodes in terms of distance and time step for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 15% NaCl.</p> Full article ">Figure 12
<p>The comparison between the liquid pressure of four selected nodes for PI cement paste during the first cooling phase with respect to temperature variation: (<b>a</b>) pure; (<b>b</b>) 15% NaCl.</p> Full article ">Figure 13
<p>The comparison between the liquid pressure of the seven selected nodes in terms of distance and time step for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 15% NaCl.</p> Full article ">Figure 14
<p>The comparison between the average axial strain of the modified and original freezing points of the present model and the numerical and experimental results from Zeng [<a href="#B9-materials-16-06594" class="html-bibr">9</a>] in terms of freezing temperature for PI cement paste during the first cooling phase: (<b>a</b>) 0% NaCl; (<b>b</b>) 3% NaCl.</p> Full article ">Figure 15
<p>The comparison between the pore pressure of the modified and original freezing points of the present model in terms of freezing temperature for PI cement paste during the first cooling phase: (<b>a</b>) freezing point −9 °C and (<b>b</b>) freezing point −0.1 °C.</p> Full article ">Figure 16
<p>The comparison between the pore pressure results of the modified and original freezing points of the present model in terms of distance for PI cement paste during the first cooling phase: (<b>a</b>) freezing point −9 °C and (<b>b</b>) freezing point −0.1 °C.</p> Full article ">Figure 17
<p>Pore size distribution for different porosity cases.</p> Full article ">Figure 18
<p>The comparison between the freezing strains of the reference liquid water permeability and six selected values based on <a href="#materials-16-06594-t005" class="html-table">Table 5</a> for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 3% NaCl; (<b>c</b>) 6% NaCl; (<b>d</b>) 15% NaCl.</p> Full article ">Figure 19
<p>The comparison of the pore and ice pressure of seven selected nodes in terms of distance and time step between the reference and the two extreme liquid water permeability values for PI cement paste with 0% chloride concentration during the first cooling phase: (<b>a</b>–<b>c</b>) pore pressure; (<b>d</b>–<b>f</b>) ice pressure.</p> Full article ">Figure 20
<p>The comparison between the freezing strains of the reference porosity and liquid water permeability and three selected values based on <a href="#materials-16-06594-t005" class="html-table">Table 5</a> for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 3% NaCl; (<b>c</b>) 6% NaCl; (<b>d</b>) 15% NaCl.</p> Full article ">Figure 20 Cont.
<p>The comparison between the freezing strains of the reference porosity and liquid water permeability and three selected values based on <a href="#materials-16-06594-t005" class="html-table">Table 5</a> for PI cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 3% NaCl; (<b>c</b>) 6% NaCl; (<b>d</b>) 15% NaCl.</p> Full article ">Figure 21
<p>The comparison between the liquid pressure of the reference porosity and liquid water permeability and three selected values based on <a href="#materials-16-06594-t005" class="html-table">Table 5</a> for PI cement paste during the first cooling phase: (<b>a</b>) 26% porosity; (<b>b</b>) 22% porosity; (<b>c</b>) 18% porosity; (<b>d</b>) 14% porosity.</p> Full article ">Figure 22
<p>The comparison between the ice pressure of the reference porosity and liquid water permeability and three selected values based on <a href="#materials-16-06594-t005" class="html-table">Table 5</a> for PI cement paste during the first cooling phase: (<b>a</b>) 26% porosity; (<b>b</b>) 22% porosity; (<b>c</b>) 18% porosity; (<b>d</b>) 14% porosity.</p> Full article ">Figure A1
<p>The comparison between the freezing strains of the current study and experimental and numerical results from Zeng [<a href="#B9-materials-16-06594" class="html-bibr">9</a>] for PII cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 1.5% NaCl; (<b>c</b>) 3% NaCl; (<b>d</b>) 6% NaCl; (<b>e</b>) 10% NaCl; (<b>f</b>) 15% NaCl.</p> Full article ">Figure A1 Cont.
<p>The comparison between the freezing strains of the current study and experimental and numerical results from Zeng [<a href="#B9-materials-16-06594" class="html-bibr">9</a>] for PII cement paste during the first cooling phase: (<b>a</b>) pure water; (<b>b</b>) 1.5% NaCl; (<b>c</b>) 3% NaCl; (<b>d</b>) 6% NaCl; (<b>e</b>) 10% NaCl; (<b>f</b>) 15% NaCl.</p> Full article ">
15 pages, 4412 KiB  
Article
Effect of the Equal Channel Angular Pressing on the Microstructure and Phase Composition of a 7xxx Series Al-Zn-Mg-Zr Alloy
by Anwar Qasim Ahmed, Dániel Olasz, Elena V. Bobruk, Ruslan Z. Valiev and Nguyen Q. Chinh
Materials 2023, 16(19), 6593; https://doi.org/10.3390/ma16196593 - 7 Oct 2023
Cited by 1 | Viewed by 1385
Abstract
A supersaturated Al-4.8%Zn-1.2%Mg-0.14%Zr (wt%) alloy was processed by the equal-channel angular pressing (ECAP) technique at room temperature in order to obtain an ultrafine-grained (UFG) microstructure having an average grain size of about 260 nm. The hardness and microstructural characteristics, such as the phase [...] Read more.
A supersaturated Al-4.8%Zn-1.2%Mg-0.14%Zr (wt%) alloy was processed by the equal-channel angular pressing (ECAP) technique at room temperature in order to obtain an ultrafine-grained (UFG) microstructure having an average grain size of about 260 nm. The hardness and microstructural characteristics, such as the phase composition and precipitations of this UFG microstructure were studied using depth-sensing indentation (DSI), transmission electron microscopy (TEM), as well as non-isothermal scanning of differential scanning calorimetry (DSC), and compared to the properties of the un-deformed sample. Emphasis was placed on the effect of the UFG microstructure on the subsequent thermal processes in DSC measurements. It has been shown that the ECAP process resulted in not only an ultrafine-grained but also a strongly precipitated microstructure, leading to a hardness (2115 MPa) two and a half times higher than the initial hardness of the freshly quenched sample. Because of the significant changes in microstructure, ECAP has also a strong effect on the dissolution (endothermic) and precipitation (exothermic) processes during DSC measurements, where the dissolution and precipitation processes were quantitatively characterized by using experimentally determined specific enthalpies, ΔH and activation energies, Q. Full article
(This article belongs to the Special Issue Microstructure, Mechanical Properties, and Deformation Characteristics of Metals and Alloys)
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<p>Mechanical strength of the investigated un-deformed and ECAP-processed samples as (<b>a</b>) the Vickers hardness and (<b>b</b>) the characteristic change of the indentation curves in the function of the aging time at RT.</p> Full article ">Figure 2
<p>STEM HAADF micrograph of the microstructure of Al-4.8Zn-1.2Mg-0.14Zr sample after quenching and storing at room temperature for a long time (more than 1 year), showing the presence of Al<sub>3</sub>Zr particles and finely-distributed GP-zones.</p> Full article ">Figure 3
<p>Ultrafine-grained microstructure of the investigated ECAP-processed AlZnMgZr sample taken as (<b>a</b>,<b>b</b>) HAADF STEM images in low and higher magnifications showing grains and precipitates, respectively, and (<b>c</b>–<b>f</b>) EDS elemental maps for Al, Zn, Mg, and Zr obtained on the area shown in (<b>b</b>). The white and black arrows in the image (<b>b</b>) indicate Mg/Zn- and Zr-rich large precipitates. Reproduced from Ref. [<a href="#B13-materials-16-06593" class="html-bibr">13</a>]. Copyright 2019, Springer.</p> Full article ">Figure 4
<p>Typical DSC thermograms taken (<b>a</b>) on the un-deformed sample, and (<b>b</b>) on ECAP-processed samples at different heating rates.</p> Full article ">Figure 5
<p>Specific enthalpy values, ∆<span class="html-italic">H<sub>d</sub></span> and ∆<span class="html-italic">H<sub>p</sub></span> as a function of heating rate for (<b>a</b>) dissolution (at the first endothermic peak) and (<b>b</b>) precipitation (at the exothermic peak), respectively, in both un-deformed and ECAP-processed samples.</p> Full article ">Figure 6
<p>Plots of Y-T functions obtained at different heating rates, characterizing (<b>a</b>) dissolution (endothermic reaction) and (<b>b</b>) precipitation (exothermic reaction) in the un-deformed sample, as well as (<b>c</b>) dissolution and (<b>d</b>) precipitation in the ECAP-processed sample.</p> Full article ">Figure 7
<p>Plots of <span class="html-italic">dY</span>/<span class="html-italic">dt</span>-T functions obtained at different heating rates, characterizing (<b>a</b>) dissolution (endothermic reaction) and (<b>b</b>) precipitation (exothermic reaction) in the un-deformed sample, as well as (<b>c</b>) dissolution and (<b>d</b>) precipitation in the ECAP-processed sample.</p> Full article ">Figure 8
<p>Kissinger plots for the first dissolution (endothermic) and precipitation (exothermic) processes in (<b>a</b>) un-deformed and (<b>b</b>) ECAP-processed Al-Zn-Mg-Zr samples. The relative error of calculation is lower than 5%.</p> Full article ">
17 pages, 11311 KiB  
Article
Research on the Performance of Superhydrophobic Cement-Based Materials Based on Composite Hydrophobic Agents
by Jie Luo, Yi Xu, Hongqiang Chu, Lu Yang, Zijian Song, Weizhun Jin, Xiaowen Wang and Yuan Xue
Materials 2023, 16(19), 6592; https://doi.org/10.3390/ma16196592 - 7 Oct 2023
Cited by 5 | Viewed by 1405
Abstract
The utilization of a novel monolithic superhydrophobic cement material effectively prevents water infiltration and enhances the longevity of the material. A method for improving superhydrophobic concrete was investigated with the aim of increasing its strength and reducing its cost by compounding superhydrophobic substances [...] Read more.
The utilization of a novel monolithic superhydrophobic cement material effectively prevents water infiltration and enhances the longevity of the material. A method for improving superhydrophobic concrete was investigated with the aim of increasing its strength and reducing its cost by compounding superhydrophobic substances with water repellents. The experimental tests encompassed the assessment of the compressive strength, contact angle, and water absorption of the superhydrophobic cementitious materials. The findings demonstrate that an increase in the dosage of isobutyltriethoxysilane (IBTES) progressively enhances the contact angle of the specimen, but significantly diminishes its compressive strength. The contact angle of SIKS mirrors that of SIS3, with a superior compressive strength that is 68% higher. Moreover, superhydrophobicity directly influences the water absorption of cementitious materials, with a more pronounced superhydrophobic effect leading to a lower water absorption rate. The water absorption of cementitious materials is influenced by the combined effect of porosity and superhydrophobicity. Furthermore, FT−IR tests unveil functional mappings, such as -CH3 which can reduce the surface energy of materials, signifying successful modification with hydrophobic substances. Full article
(This article belongs to the Topic Advanced Self-Cleaning Surfaces)
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<p>The schematic diagram of the fabrication process of superhydrophobic mortar.</p> Full article ">Figure 2
<p>Morphology of the water droplet on superhydrophobic surfaces.</p> Full article ">Figure 3
<p>Effect of different hydrophobic agents on (<b>a</b>) contact angle and (<b>b</b>) contact angle hysteresis.</p> Full article ">Figure 4
<p>Water droplet wetting diagram on specimen surface: (<b>a</b>–<b>c</b>) superhydrophobic; (<b>d</b>–<b>f</b>) hydrophobic; (<b>g</b>–<b>i</b>) hydrophilic.</p> Full article ">Figure 5
<p>Dynamic bouncing processes of different groups.</p> Full article ">Figure 6
<p>Water droplets touching different surfaces.</p> Full article ">Figure 7
<p>Effect of different hydrophobic agents on compressive strength.</p> Full article ">Figure 8
<p>Variation of water absorption rate of each group with time.</p> Full article ">Figure 9
<p>Micro morphology of different groups.</p> Full article ">Figure 9 Cont.
<p>Micro morphology of different groups.</p> Full article ">Figure 10
<p>EDS spectrum of (<b>a</b>) SIKS and (<b>b</b>) SKS.</p> Full article ">Figure 11
<p>XRD patterns of superhydrophobic concrete prepared with different hydrophobic agent types.</p> Full article ">Figure 12
<p>FT−IR patterns of superhydrophobic concrete prepared with different hydrophobic agent types.</p> Full article ">Figure 13
<p>Superhydrophobic modification mechanism of hydrophobic agents.</p> Full article ">Figure 14
<p>MIP test for pore size distribution: (<b>a</b>) cumulative pore volume; (<b>b</b>) pore structure distribution; (<b>c</b>) pore diameter distribution.</p> Full article ">Figure 14 Cont.
<p>MIP test for pore size distribution: (<b>a</b>) cumulative pore volume; (<b>b</b>) pore structure distribution; (<b>c</b>) pore diameter distribution.</p> Full article ">
18 pages, 7139 KiB  
Article
Study on the Dynamic Mechanical Properties of Ultrahigh-Performance Concrete under Triaxial Constraints
by Wei Zhang, Jize Mao, Xiao Yu, Bukui Zhou and Limei Wang
Materials 2023, 16(19), 6591; https://doi.org/10.3390/ma16196591 - 7 Oct 2023
Cited by 1 | Viewed by 1258
Abstract
To confirm the effect of confining pressure on the dynamic mechanical behavior of ultrahigh-performance concrete (UHPC), this study used a true triaxial split Hopkinson pressure bar test system to perform dynamic compression tests on UHPC under triaxial constraints. The confining pressure range considered [...] Read more.
To confirm the effect of confining pressure on the dynamic mechanical behavior of ultrahigh-performance concrete (UHPC), this study used a true triaxial split Hopkinson pressure bar test system to perform dynamic compression tests on UHPC under triaxial constraints. The confining pressure range considered was 5~10 MPa, the strain rate range was 35~80 s−1, and the steel fiber contents were 0.5%, 1% and 2%. The three-dimensional dynamic engineering stress-strain relationship and equivalent stress-strain relationship of UHPC under different confining pressures and different strain rates were obtained and analyzed in detail. The results show that under the confinement condition, the dynamic peak axial stress–strain and dynamic peak lateral stress–strain of UHPC have strong sensitivity to the strain rate. In addition, the dynamic peak lateral stress–strain is more sensitive to the confining pressure than the dynamic axial stress. An empirical strength enhancement factor (DIFc) that considers the strain rate effect and confining pressure was derived, and the impact of the coupling between the enhancement caused by the confining pressure and the strain rate effect on the dynamic strength of the UHPC under triaxial confinement was discussed. A dynamic strength failure criterion for UHPC under triaxial constraint conditions was established. Full article
(This article belongs to the Special Issue Mechanical Research of Reinforced Concrete Materials)
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<p>Trial mold and test specimen.</p> Full article ">Figure 2
<p>The true triaxial split Hopkinson pressure bar loading system.</p> Full article ">Figure 3
<p>Standard cubic specimen placed between the bars of the loading element.</p> Full article ">Figure 4
<p>Stress equilibrium.</p> Full article ">Figure 4 Cont.
<p>Stress equilibrium.</p> Full article ">Figure 5
<p>Typical curve in x-direction.</p> Full article ">Figure 6
<p>Stress-strain curve.</p> Full article ">Figure 7
<p>Equivalent stress-strain curves of U1 under different strain rates.</p> Full article ">Figure 8
<p>Equivalent stress-strain curve of U1 when the strain rate was 60 s<sup>−1</sup>.</p> Full article ">Figure 9
<p>DIF (DIF<sub>c</sub>) for the compressive strength of UHPC [<a href="#B22-materials-16-06591" class="html-bibr">22</a>,<a href="#B26-materials-16-06591" class="html-bibr">26</a>,<a href="#B33-materials-16-06591" class="html-bibr">33</a>,<a href="#B34-materials-16-06591" class="html-bibr">34</a>,<a href="#B35-materials-16-06591" class="html-bibr">35</a>].</p> Full article ">Figure 10
<p>Weakening of the Stefan effect induced by confinement.</p> Full article ">Figure 11
<p>Mechanism of confining pressure and strain rate effects of concrete.</p> Full article ">Figure 12
<p>True triaxial dynamic failure criterion in octahedral stress space.</p> Full article ">
14 pages, 10430 KiB  
Article
Effect of Melt-Spinning Parameters on the Structure and Properties of Ni55.5Mn18.8Ga24Si1.7 Heusler Alloy Ribbons
by Pranav Bhale, Pnina Ari-Gur, Ronald D. Noebe, Yang Ren, Amila Madiligama, Ranjith Devaraj and Matthew S. Cook
Materials 2023, 16(19), 6590; https://doi.org/10.3390/ma16196590 - 7 Oct 2023
Cited by 1 | Viewed by 1526
Abstract
Ni–Mn-based Heusler alloys are known to demonstrate magnetic shape memory and giant magnetocaloric effect (MCE). These effects depend on the phases, crystallographic and magnetic phase transitions, and the crystallographic texture characteristics. These structural characteristics, in turn, are a function of the processing parameters. [...] Read more.
Ni–Mn-based Heusler alloys are known to demonstrate magnetic shape memory and giant magnetocaloric effect (MCE). These effects depend on the phases, crystallographic and magnetic phase transitions, and the crystallographic texture characteristics. These structural characteristics, in turn, are a function of the processing parameters. In the current work, Ni55.5Mn18.8Ga24Si1.7 Heusler alloy was processed by melt-spinning under a helium atmosphere. This process results in a fine microstructure. The ribbon that was produced with a narrower nozzle width, faster wheel speed, and higher cast temperature, indicating a faster cooling rate, had double the magnetic entropy change close to room temperature. However, the other ribbon demonstrated a large entropy change over a broader temperature range, extending its usability. The effect of the melt-spinning process parameters on the developing microstructure, crystallographic structure and texture, transformation temperatures, and the magnetic entropy change were studied to explain the difference in magnetocaloric behavior. Full article
(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)
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<p>Schematic diagram for synchrotron X-ray diffraction (adapted from [<a href="#B23-materials-16-06590" class="html-bibr">23</a>]). The X-ray beam incident to the sample diffracts at an angle 2θ. The diffracted Debye rings are captured by the 2D area detector, and the results are saved as 2D images.</p> Full article ">Figure 2
<p>SEM images of cross-sections of BMS220 and BMS222 as-melt-spun ribbon. (<b>a</b>,<b>b</b>) Cross-sections of BMS220 and BMS222, respectively. (<b>c</b>,<b>d</b>) Higher resolution images of (<b>a</b>,<b>b</b>), respectively. The right side of each image is the wheel-side of the ribbon, and the left side is the free-side.</p> Full article ">Figure 3
<p>Synchrotron results were presented as calibrated 2D images for BMS220 (<b>a</b>) and BMS222 (<b>c</b>). The refined, integrated pattern for austenite and martensite is shown for BMS220 (<b>b</b>) and BMS220 (<b>d</b>).</p> Full article ">Figure 4
<p>Ambient XRD patterns for free- and wheel-side of BMS220 (<b>a</b>) and BMS 222 (<b>b</b>) melt-spun ribbon. Peaks are indexed for austenite (A) and martensite (M) phases.</p> Full article ">Figure 5
<p>400, 220, and 422 pole figures of austenite in BMS220 melt-spun ribbon.</p> Full article ">Figure 6
<p>200 and 101 pole figures of martensite in BMS220 melt-spun ribbon.</p> Full article ">Figure 7
<p>220, 400, and 422 pole figures of austenite planes in BMS222 melt-spun ribbons.</p> Full article ">Figure 8
<p>200 and 101 pole figures of martensite planes in BMS222 melt-spun ribbons.</p> Full article ">Figure 9
<p>Isothermal magnetization curves for (<b>a</b>) BMS220 and (<b>b</b>) BMS222 melt-spun ribbon.</p> Full article ">Figure 10
<p>Mass magnetization vs. temperature of BMS220 (<b>a</b>) and BMS222 (<b>b</b>) at selected applied fields.</p> Full article ">Figure 11
<p>Temperature dependence of the resistivity under applied magnetic fields in the range of 0 to 11 T for BMS220 (<b>a</b>) and BMS222 (<b>b</b>). Martensitic transformation temperature as a function of the magnetic field, obtained from the resistivity curves for BMS220 and BMS222, as depicted in (<b>c</b>) and (<b>d</b>), respectively.</p> Full article ">Figure 11 Cont.
<p>Temperature dependence of the resistivity under applied magnetic fields in the range of 0 to 11 T for BMS220 (<b>a</b>) and BMS222 (<b>b</b>). Martensitic transformation temperature as a function of the magnetic field, obtained from the resistivity curves for BMS220 and BMS222, as depicted in (<b>c</b>) and (<b>d</b>), respectively.</p> Full article ">Figure 12
<p>Temperature dependence of the magnetic entropy change for BMS220 (<b>a</b>) and BMS222 (<b>b</b>) melt-spun ribbons under magnetic fields H = 0.5 to 14 T.</p> Full article ">
15 pages, 5830 KiB  
Article
Large-Area Mapping of Voids and Dislocations in Basal-Faceted Sapphire Ribbons by Synchrotron Radiation Imaging
by Tatiana S. Argunova, Victor G. Kohn, Jae-Hong Lim, Vladimir M. Krymov and Mikhail Yu. Gutkin
Materials 2023, 16(19), 6589; https://doi.org/10.3390/ma16196589 - 7 Oct 2023
Cited by 2 | Viewed by 1092
Abstract
The understanding of structural defects in basal-faceted sapphire ribbons was improved through X-ray imaging at a synchrotron source. The combination of phase contrast and X-ray diffraction makes it possible to visualize and characterize both gas voids and dislocations in the bulk of the [...] Read more.
The understanding of structural defects in basal-faceted sapphire ribbons was improved through X-ray imaging at a synchrotron source. The combination of phase contrast and X-ray diffraction makes it possible to visualize and characterize both gas voids and dislocations in the bulk of the ribbons grown by the Stepanov–LaBelle technology. Dislocations were directly related to gas voids. X-ray diffraction topography was employed to investigate the distribution, configurations, and character of the dislocations. The formation of voids of irregular shapes was detected by large-area mapping with spatial resolution in the μm range. Computer simulations of the experimental phase contrast images of microvoids were performed. The sizes of the spherical microvoids were determined. The results are discussed with reference to the available data on the emission of dislocations from the voids. The evolution of the shape, size, and arrangement of the voids during growth provides clues on the formation of block structure in basal-faceted sapphire ribbons. Full article
(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) Sketch of a sapphire specimen. The circle and the box show the areas imaged by XRT and PCI techniques, respectively. The arrow is the growth direction. (<b>b</b>) A high-speed topograph in back reflection taken with SR radiation (<span class="html-italic">λ</span> = 0.827 Å) on imaging detector VHR CCD, <b>g</b> = <math display="inline"><semantics> <mrow> <mn>3</mn> <mover accent="true"> <mn>3</mn> <mo stretchy="true">¯</mo> </mover> <mn>018</mn> </mrow> </semantics></math>. (<b>c</b>) The topograph in transmission taken with Kodak M100 film. <b>g</b> = <math display="inline"><semantics> <mrow> <mn>1</mn> <mover accent="true"> <mn>2</mn> <mo stretchy="true">¯</mo> </mover> <mn>10</mn> </mrow> </semantics></math>. (<b>d</b>) <b>g</b> = <math display="inline"><semantics> <mrow> <mn>3</mn> <mover accent="true"> <mn>3</mn> <mo stretchy="true">¯</mo> </mover> <mn>018</mn> </mrow> </semantics></math>; Kodak M100.</p> Full article ">Figure 2
<p>(<b>a</b>) Schematic relationship between the (<math display="inline"><semantics> <mrow> <mover accent="true"> <mn>3</mn> <mo stretchy="true">¯</mo> </mover> <mn>3018</mn> </mrow> </semantics></math>) diffracting plane and dislocation semiloops emitted by the source on the basal plane. The Burgers vectors are parallel to 1/3 [<math display="inline"><semantics> <mrow> <mn>11</mn> <mover accent="true"> <mn>2</mn> <mo stretchy="true">¯</mo> </mover> <mn>0</mn> </mrow> </semantics></math>]. (<b>b</b>) Magnified images of semiloops in the B region of <a href="#materials-16-06589-f001" class="html-fig">Figure 1</a>c. The inset shows the same region where the semiloop images are extinct in the <math display="inline"><semantics> <mrow> <mn>3</mn> <mover accent="true"> <mn>3</mn> <mo stretchy="true">¯</mo> </mover> <mn>018</mn> </mrow> </semantics></math> reflection. The solid circles denote the same spot on both of the topographs.</p> Full article ">Figure 3
<p>(<b>a</b>) General view of dislocations at the beginning of ribbon growth. The arrangement is revealed at the upper boundary of the box in <a href="#materials-16-06589-f001" class="html-fig">Figure 1</a>a. Lang topography; Ag<span class="html-italic">K</span><sub>α</sub> radiation, <math display="inline"><semantics> <mrow> <mover accent="true"> <mn>3</mn> <mo stretchy="true">¯</mo> </mover> <mn>300</mn> </mrow> </semantics></math> reflection of sapphire. (<b>b</b>) Phase contrast image of gas voids located in the same area with dislocations. The dashed lines cross each image at the same distance from the seed.</p> Full article ">Figure 4
<p>Gas voids in the part of the specimen later to grow as compared with the part in <a href="#materials-16-06589-f003" class="html-fig">Figure 3</a>b. The two parts match each other along the dashed arrow. The inset shows magnified images of voids farther away from the seed.</p> Full article ">Figure 5
<p>Experimental phase contrast images of some gas voids recoded at sample-to-detector distance <span class="html-italic">z</span><sub>1</sub> = 1.5 cm (<b>a</b>) and <span class="html-italic">z</span><sub>2</sub> = 20 cm (<b>b</b>).</p> Full article ">Figure 6
<p>Theoretical phase contrast images of two spheres with 20 μm diameter calculated for the distances <span class="html-italic">z</span><sub>1</sub> = 1.5 cm (<b>left</b>) and <span class="html-italic">z</span><sub>2</sub> = 20 cm (<b>right</b>).</p> Full article ">Figure 7
<p>Phase contrast images calculated for the distance <span class="html-italic">z</span><sub>2</sub> = 20 cm and averaged using convolution with Gaussian of FWHM = 3 μm (<b>left</b>) and 4 μm (<b>right</b>).</p> Full article ">Figure 8
<p>Phase contrast images calculated for the distance <span class="html-italic">z</span><sub>1</sub> = 1.5 cm and averaged using the Gaussian of FWHM = 0.26 μm (<b>left</b>) and 1 μm (<b>right</b>).</p> Full article ">
6 pages, 1263 KiB  
Communication
Superconducting In Situ/Post In Situ MgB2 Joints
by Bartlomiej Andrzej Glowacki
Materials 2023, 16(19), 6588; https://doi.org/10.3390/ma16196588 - 7 Oct 2023
Viewed by 1095
Abstract
The superconducting joints of superconducting in situ MgB2 wires have been of great interest since the first MgB2 wires were manufactured. The necessity of joining fully reacted wires in applications such as NMR brings complexity to the methodology of connecting already [...] Read more.
The superconducting joints of superconducting in situ MgB2 wires have been of great interest since the first MgB2 wires were manufactured. The necessity of joining fully reacted wires in applications such as NMR brings complexity to the methodology of connecting already reacted wires sintered under optimised conditions via a mixture of Mg + 2B and subsequential second heat treatment to establish fully superconducting MgB2 joints. Some of the data in the literature resolved such a procedure by applying high cold pressure and sintering at a low temperature. A topical review publication did not address in depth the question of whether cold sintering is a potential solution, suggesting that hot pressing is the way forward. In this paper, we discuss the potential joint interfacial requirements, suggesting a thermo-mechanical procedure to successfully form a superconductive connection of two in situ reacted wires in the presence of Mg + 2B flux. The critical current at 25 K of the researched junction achieved 50% Ic for an individual in situ wire. Full article
(This article belongs to the Special Issue Superconductors: Materials and Technology)
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<p>Schematic of the adopted joint architecture: (<b>a</b>) assembled in situ reacted MgB<sub>2</sub> wires inside a capsule filled with pre-compressed Mg+2B mixture of the same composition used for the manufacture of the wires [<a href="#B13-materials-16-06588" class="html-bibr">13</a>]; (<b>b</b>) junction from <a href="#materials-16-06588-f001" class="html-fig">Figure 1</a>a after 0.5 GPa uniaxial compression in the joining area and sintering at 900 °C for 30 min, followed by cooling, as described in the text.</p> Full article ">Figure 2
<p>Mg–B binary phase diagram from [<a href="#B15-materials-16-06588" class="html-bibr">15</a>]. The shaded area represents the availability of Mg and B for the filler reaction process after junction compression to 0.5 GPa. The horizontal “reversible” arrow represents discussion of MgB<sub>2</sub> and MgB<sub>4</sub> interformation presented in <a href="#sec3dot1-materials-16-06588" class="html-sec">Section 3.1</a>. The vertical “reversible” arrow represents an excess of Mg at the initial stage of sintering of the joints and solid-state diffusion of the joints during cooling presented in <a href="#sec3dot2-materials-16-06588" class="html-sec">Section 3.2</a>.</p> Full article ">Figure 3
<p>SEM image of the cross-sectional interface between the wire and filler in the joining capsule. (<b>a</b>) EDAX current work; the OD of the wire was 0.7 mm. The different morphology of the wire core and the filling material can be observed at the actual joining interface. The fibre-like structure of the original wire induced by cold deformation of the powder is pronounced, whereas the filler matrix looks very uniform. A deep green colour represents MgB<sub>2</sub>. (<b>b</b>) For comparison, the cross-sectional microstructure of the initial fully in situ joint formation is presented [<a href="#B1-materials-16-06588" class="html-bibr">1</a>], where electromagnetic compaction created a distinctive buckling effect on the interfacial region between the wire and the filler, which is not observed in <a href="#materials-16-06588-f003" class="html-fig">Figure 3</a>a. The above comparison of morphological differences of the fibre-like ex situ wire in a rigid in situ capsule and the in situ wire in contact with in situ filler powder reveals the complexity of the deformation processes taking place in various joints. An important fact is that the I<sub>c</sub> value for the joint presented in <a href="#materials-16-06588-f001" class="html-fig">Figure 1</a>b was only 15% that for the wire (at 25 K self-field).</p> Full article ">
14 pages, 3598 KiB  
Article
A Route to Understanding the Ethane Adsorption Selectivity of the Zeolitic Imidazolate Framework-8 in Ethane–Ethylene Mixtures
by Jaquebet Vargas-Bustamante, Roberto Salcedo and Jorge Balmaseda
Materials 2023, 16(19), 6587; https://doi.org/10.3390/ma16196587 - 7 Oct 2023
Cited by 1 | Viewed by 1332
Abstract
Ethylene production has a negative environmental impact, with its separation step being one of the major contributors of pollution. This has encouraged the search for energy-efficient alternatives, among which the adsorptive separation of ethane and ethylene stands out. ZIF-8 is a molecular sieve [...] Read more.
Ethylene production has a negative environmental impact, with its separation step being one of the major contributors of pollution. This has encouraged the search for energy-efficient alternatives, among which the adsorptive separation of ethane and ethylene stands out. ZIF-8 is a molecular sieve that is potentially useful for this purpose. It is selective to ethane, an exceptional property that remains unexplained. Furthermore, the adsorption of ethane and ethylene above room temperature, such as at steam cracking process outlet temperatures, has not been addressed either. This work aims to fill this knowledge gap by combining experiments at very low volumetric fillings with density–functional theory modelling methods. Adsorption isotherms of ethane and ethylene on ZIF-8 at pressures below 0.3 bar and 311 K, 333 K, and 363 K were measured using zero-length column chromatography. The low-pressure domain of the isotherms contains information on the interactions between the adsorbate molecules and the adsorbent. This favors the understanding of their macroscopic behavior from simulations at the atomic level. The isosteric enthalpy of adsorption of ethane remained constant at approximately −10 kJ/mol. In contrast, the isosteric enthalpy of adsorption of ethylene decreased from −4 kJ/mol to values akin to those of ethane as temperature increased. ZIF-8 selectivity to ethane, estimated from ideal adsorbed solution theory, decreased from 2.8 to 2.0 with increasing pressure up to 0.19 bar. Quantum mechanical modelling suggested that ethylene had minimal interactions with ZIF-8, while ethane formed hydrogen bonds with nitrogen atoms within its structure. The findings of this research are a platform for designing new systems for the adsorptive separation of ethane and ethylene and thus, reducing the environmental impact of ethylene production. Full article
(This article belongs to the Section Porous Materials)
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<p>Fourier−transform infrared (FT-IR) spectra of (<b>a</b>) the 4000–460 cm<sup>−1</sup> region and (<b>b</b>) the 1850–500 cm<sup>−1</sup> region of synthesized ZIF-8.</p> Full article ">Figure 2
<p>Powder diffraction patterns of synthesized and simulated ZIF-8.</p> Full article ">Figure 3
<p>Thermogravimetric (green), derivative thermogravimetric (blue), and calorimetric (maroon) curves for ZIF−8.</p> Full article ">Figure 4
<p>SEM micrograph of (<b>a</b>) ZIF-8 powder and its (<b>b</b>) particle size distribution.</p> Full article ">Figure 5
<p>Adsorption isotherms derived from the integration of the ZLC response curves of ethane and ethylene on ZIF-8 at various temperatures.</p> Full article ">Figure 6
<p>Isosteric enthalpy of adsorption of ethane and ethylene on ZIF-8. The enthalpies were calculated from the Clausius–Clapeyron equation and isotherms at 311 K, 333 K, and 363 K.</p> Full article ">Figure 7
<p>IAST-predicted selectivity for a 0.5:0.5 mixture composition of ethane over ethylene on ZIF-8 at different temperatures.</p> Full article ">Figure 8
<p>Single cell from the ZIF-8 MOF. The gray, strong blue, white, and light blue spheres represent C, N, H, and Zn atoms, respectively.</p> Full article ">Figure 9
<p>Hydrogen bonds among ethane terminal hydrogens and the MOF’s cell. The gray, strong blue, white, and light blue spheres represent C, N, H, and Zn atoms, respectively.</p> Full article ">Figure 10
<p>Molecular electrostatic potential mapped onto electron density from the cell of ZIF-8.</p> Full article ">
16 pages, 5661 KiB  
Article
A Study on the 3D Deformation Behavior of Porous PDMS Flexible Electronic Composite Films Stretched under Different Temperatures
by Cheng Chen, Ziyun Li, Yanlai Wang, Ze Zhang and Chunhua Ren
Materials 2023, 16(19), 6586; https://doi.org/10.3390/ma16196586 - 6 Oct 2023
Cited by 1 | Viewed by 1421
Abstract
Flexible electronic films need to be applied in different ambient temperatures. The porous substrate of the composite film enhances air permeability. The lifespan of these composite films is significantly affected by variations in temperature and substrate porosity. To explore the impact of temperature [...] Read more.
Flexible electronic films need to be applied in different ambient temperatures. The porous substrate of the composite film enhances air permeability. The lifespan of these composite films is significantly affected by variations in temperature and substrate porosity. To explore the impact of temperature and porosity on the performance of composite films, we developed a 3D deformation detection system utilizing the advanced three-dimensional digital image correlation (3D-DIC) method. This system enabled us to observe and analyze the 3D deformation behaviors of porous polydimethylsiloxane (PDMS) flexible composite films when they are subjected to uniaxial stretching at different temperatures. We proposed employing two parameters, namely the strain fluctuation coefficient (M) and off-plane displacement (w), to characterize the 3D deformation of the films. This holistic characterization of deformation through the combined utilization of parameters M and w held greater significance for composite films compared to the conventional practice of solely measuring mechanical properties like the elastic modulus. Through experimental analysis, we discovered that as the temperature increased, the M value of the film decreased while the w value increased for the same stretching distance. Furthermore, the porosity of the composite film depended on the doping mass ratio of PDMS to deionized water during the fabrication process. Specifically, when the ratio was set at 6:1, the composite film exhibited the smallest M value and w value, and the highest air permeability. Additionally, the 3D deformation behavior remained stable across different temperatures for this specific ratio. Moreover, our findings unveiled a remarkable association between the parameter w and the resistance value of the device. These findings provide valuable insights for optimizing the fabrication process of porous PDMS flexible electronic composite films. Full article
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Figure 1

Figure 1
<p>(<b>a</b>) Photograph of porous PDMS flexible electronic composite film. (<b>b</b>) Fabrication process for porous PDMS flexible electronic composite film. (<b>c</b>) Three-dimensional deformation detection system for flexible electronic composite film. (<b>d</b>) Picture of composite film mounted on stretching table.</p> Full article ">Figure 2
<p>(<b>a</b>) Principle of binocular stereo vision. (<b>b</b>) System for testing the air permeability of films. (<b>c</b>) Mass of distilled water reduced by boiling in five sets of conical flasks. (<b>d</b>) SEM images of Groups A–D.</p> Full article ">Figure 3
<p>(<b>a</b>) Von Mises strain field of Group C devices stretched by 3 mm at 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C. (<b>b</b>) Three−dimensional off−plane displacement field of Group C devices stretched by 3 mm at 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C.</p> Full article ">Figure 4
<p>Von Mises strain curve on line <span class="html-italic">L</span> at 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C when the Group C devices are stretched by 1−5 mm.</p> Full article ">Figure 5
<p>Line graph of strain fluctuation index <span class="html-italic">M</span> for five groups of devices A–E stretched 1–5 mm at 0–50 °C.</p> Full article ">Figure 6
<p>Line graph of the average off-surface displacement <span class="html-italic">w<sub>m</sub></span> of line <span class="html-italic">L</span><sub>1</sub> for five groups of devices A–E when stretched 1–5 mm at 0–50 °C.</p> Full article ">Figure 7
<p>Graphs of the average off-plane displacement (<span class="html-italic">w<sub>m</sub></span>) during cyclic stretching (0–5 mm) at 20 °C for five groups of devices labeled A–E.</p> Full article ">Figure 8
<p>The resistance values of five device groups (A–E) when stretched between 1 and 5 mm at temperatures ranging from 0 to 50 °C.</p> Full article ">
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