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Materials, Volume 15, Issue 6 (March-2 2022) – 357 articles

Cover Story (view full-size image): This work reports on TiN-Ag antimicrobial coatings deposited by DC magnetron sputtering on leather for insoles on the footwear industry and studies involving the antimicrobial properties of these coatings. The XRD results suggested the presence of a crystalline fcc-TiN phase and a fcc-Ag phase in the samples containing silver. SEM analysis shows that coatings were homogeneous, and dispersed Ag clusters were found on samples with silver content above 8 at.%. ICP-OES spectrometry analysis showed that the ionization of silver over time depends on the morphology of coatings. The samples did not present cytotoxicity and only samples with silver presented antibacterial and antifungal activity, highlighting the potential of the TiN-Ag insole coatings for diseases such as diabetic foot. View this paper
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13 pages, 2279 KiB  
Article
Study of Compatibility and Flame Retardancy of TPU/PLA Composites
by Zusheng Hang, Zichun Lv, Liu Feng and Ben Liu
Materials 2022, 15(6), 2339; https://doi.org/10.3390/ma15062339 - 21 Mar 2022
Cited by 5 | Viewed by 3411
Abstract
In order to apply the rigid biodegradable PLA material for flexible toothbrush bristle products, in this paper, Poly(lactic acid) (PLA) and thermoplastic polyurethane elastomer (TPU) blends (TPU/PLA composites), with a mass ratio of 80:20, were prepared by the melt-blending method to achieve toughening [...] Read more.
In order to apply the rigid biodegradable PLA material for flexible toothbrush bristle products, in this paper, Poly(lactic acid) (PLA) and thermoplastic polyurethane elastomer (TPU) blends (TPU/PLA composites), with a mass ratio of 80:20, were prepared by the melt-blending method to achieve toughening modification. Infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and low-field nuclear magnetic resonance were used to investigate the effect of the compatibilizer, Maleic anhydride grafted polypropylene (PP-g-MAH), on the compatibility of the blends, and the effect of melamine on the flame retardant properties of the blends was further investigated. The results demonstrated that 3% PP-g-MAH had the best compatibility effect on PLA and TPU; the TPU/PLA composites have a better macromolecular motility and higher crystallization capacity in the amorphous regions through the physical and chemical action by using PP-g-MAH as a compatibilizer. By adding melamine as a flame retardant, the scorch wire ignition temperature of TPU/PLA composites can reach 830 °C, which was elevated by 80 °C compared with pure PLA; however, the flame retardant effect of melamine in a single system was not significant. Melamine acts as a flame retardant by absorbing heat through decomposition and diluting the combustible material by producing an inert gas. Full article
(This article belongs to the Section Polymeric Materials)
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<p>The shape of the finished product.</p> Full article ">Figure 2
<p>SEM photos of different compatibilizer contents. (<b>a</b>) is the morphology of the material amplified to 40 μm at 1% compatibilizer, (<b>b</b>) is the morphology of the material amplified to 40 μm at 3% compatibilizer, (<b>c</b>) is the cracks and holes in section when compatibilizer is 1%, (<b>d</b>) is the morphology of the material amplified to 40 μm at 5% compatibilizer, (<b>e</b>) is the morphology of the material amplified to 40 μm at 7% compatibilizer.</p> Full article ">Figure 3
<p>Infrared spectra of TPU/PLA composites with different compatibilizer contents.</p> Full article ">Figure 4
<p>Infrared spectrum of PP-<span class="html-italic">g</span>-MAH and the composite.</p> Full article ">Figure 5
<p>Structural representation. (<b>a</b>) Molecular structure of PLA and PP-<span class="html-italic">g</span>-MAH. (<b>b</b>) Structure diagram of TPU. (<b>c</b>) Compatibility mechanism of PP-<span class="html-italic">g</span>-MAH compatibilizer.</p> Full article ">Figure 6
<p>DSC curves of TPU/PLA composites with different compatibilizer contents.</p> Full article ">Figure 7
<p>Low-field NMR spectra of TPU/PLA composites with different compatibilizer contents.</p> Full article ">Figure 8
<p>DSC curves of TPU/PLA composites with different flame-retardant contents.</p> Full article ">Figure 9
<p>Low-field NMR spectra of TPU/PLA composites with different flame-retardant contents.</p> Full article ">Figure 10
<p>Non-combustion and extinguishing after combustion in the hot wire test.</p> Full article ">
13 pages, 58178 KiB  
Article
Design, Fabrication, and Mechanical Properties of T-700TM Multiaxial-Warp-Knitting–Needled–C/SiC Composite and Pin
by Xiao Luo, Jiangyi He, Xiaochong Liu, Youliang Xu, Jian Li, Xiaojun Guo, Qianru Wang and Longbiao Li
Materials 2022, 15(6), 2338; https://doi.org/10.3390/ma15062338 - 21 Mar 2022
Cited by 5 | Viewed by 2373
Abstract
In this paper, the 12k T-700TM Multiaxial-Warp-Knitting–Needle (MWK–N) C/SiC composite and pin were designed and fabricated using the isothermal chemical vapor infiltration (ICVI) method. The composite’s microstructure and mechanical properties were examined by subjection to tensile and interlaminar shear tests. Three types [...] Read more.
In this paper, the 12k T-700TM Multiaxial-Warp-Knitting–Needle (MWK–N) C/SiC composite and pin were designed and fabricated using the isothermal chemical vapor infiltration (ICVI) method. The composite’s microstructure and mechanical properties were examined by subjection to tensile and interlaminar shear tests. Three types of double-shear tests were conducted for C/SiC pins, including shear loading perpendicularly, along, and at 45° off-axial to the lamination. The fracture surface of the tensile and shear failure specimens was observed under scanning electronic microscope (SEM). The relationships between the composite’s microstructure, mechanical properties, and damage mechanisms were established. The composite’s average tensile strength was σuts = 68.3 MPa and the average interlaminar shear strength was τu = 38.7 MPa. For MWK–N–C/SiC pins, the double-shear strength was τu = 76.5 MPa, 99.7 MPa, and 79.6 MPa for test types I, II, and III, respectively. Compared with MWK–C/SiC pins, the double-shear strength of MWK–N–C/SiC pins all decreased, i.e., 26.7%, 50.8%, and 8% for test types I, II, and III, respectively. The MWK–N–C/SiC composite and pins possessed high interlaminar shear strength and double-shear strength, due to the needled fiber in the thickness direction, low porosity (10–15%), and high composite density (2.0 g/cm3). Full article
(This article belongs to the Special Issue Damage, Fracture and Fatigue of Ceramic Matrix Composites (CMCs))
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<p>Mechanical tests of C/SiC composite and pins. (<b>a</b>) Tensile; (<b>b</b>) interlaminar shear; and (<b>c</b>) double-shear.</p> Full article ">Figure 2
<p>Schematic of three types of double-shear tests for the C/SiC pin.</p> Full article ">Figure 3
<p>Monotonic tensile stress–strain curves of the 12k T-700<sup>TM</sup> MWK–N–C/SiC composite.</p> Full article ">Figure 4
<p>Tensile fracture surface of the 12k T-700<sup>TM</sup> MWK–N–C/SiC specimen observed under SEM. (<b>a</b>) fibers pullout in the 0° and 45° plies; (<b>b</b>) fiber pullout in the 0° plies; (<b>c</b>) 0° and 45° fiber pullout; (<b>d</b>) fiber pullout in the 0° plies.</p> Full article ">Figure 5
<p>Interlaminar shear fracture surface of the 12k T-700<sup>TM</sup> MWK–N–C/SiC specimen observed under SEM. (<b>a</b>) fracture surface of MWK–C/SiC specimen; (<b>b</b>) fracture fiber of MWK–C/SiC specimen; (<b>c</b>) needled fiber fracture in MWK–N–C/SiC specimen; (<b>d</b>) needled fiber pullout in MWK–N–C/SiC specimen.</p> Full article ">Figure 6
<p>Double-shear load-displacement curves of the 12k T-700<sup>TM</sup> MWK–N–C/SiC pins: (<b>a</b>) type I; (<b>b</b>) type II; and (<b>c</b>) type III.</p> Full article ">Figure 7
<p>Double-shear strength of the 12k T-700<sup>TM</sup> MWK–N–C/SiC pins.</p> Full article ">Figure 8
<p>Type I double-shear fracture surface of the 12k T-700<sup>TM</sup> MWK–N–C/SiC pin observed under SEM. (<b>a</b>) fracture surface; (<b>b</b>) fiber pullout in different plies; (<b>c</b>) fiber pullout; (<b>d</b>) fiber fracture and pullout.</p> Full article ">Figure 9
<p>Type II double-shear fracture surface of the 12k T-700<sup>TM</sup> MWK–N–C/SiC pin observed under SEM. (<b>a</b>) fracture surface; (<b>b</b>) fiber pullout in different plies; (<b>c</b>) fiber fracture and pullout.</p> Full article ">Figure 10
<p>Type III double-shear fracture surface of the 12k T-700<sup>TM</sup> MWK–N–C/SiC pin observed under SEM. (<b>a</b>) fracture surface; (<b>b</b>) fractured fibers; (<b>c</b>) fiber pullout; (<b>d</b>) fiber fracture and pullout.</p> Full article ">Figure 11
<p>Type I double-shear fracture surface of 2D plain-woven C/SiC pin observed under SEM. (<b>a</b>) fracture surface; (<b>b</b>) fiber pullout in different plies; (<b>c</b>) fiber fracture and pullout; (<b>d</b>) fiber fracture and pullout.</p> Full article ">
10 pages, 1648 KiB  
Article
Effect of the P/Al Molar Ratio and Heating Rate on the Composi-Tion of Alumino-Phosphate Binders
by Grégory Tricot, Hanyu Hu, Amélie Beaussart, Ismérie Fernandes and Clément Perrot
Materials 2022, 15(6), 2337; https://doi.org/10.3390/ma15062337 - 21 Mar 2022
Cited by 5 | Viewed by 2015
Abstract
New insights into the chemistry of alumino-phosphate solutions are provided in this contribution. In a first part, a solution with a P/Al molar ratio of 3.2 was prepared for the first time. The binders obtained at 500 and 700 °C were compared to [...] Read more.
New insights into the chemistry of alumino-phosphate solutions are provided in this contribution. In a first part, a solution with a P/Al molar ratio of 3.2 was prepared for the first time. The binders obtained at 500 and 700 °C were compared to those obtained with the 3 and 3.5 P/Al molar ratio solutions in order to determine the impact of moderate P2O5 excess on the final phosphate ceramic nature. In a second part, the widely used P/Al = 3 solution was heat-treated at 500 °C using different heating rates (0.2, 1, and 10 °C/min) to determine how this parameter modifies the final phosphate ceramic composition. Our data show that moderate P2O5 excess is sufficient to obtain binders with a high amount of stable cubic aluminium metaphosphate compound at 700 °C but not at 500 °C, where significant P2O5 excess is mandatory. We also show that slow heating favors the formation of cubic aluminium metaphosphate compound at 500 °C. Full article
(This article belongs to the Special Issue Advances in Phosphate Materials: Structural, Technological and Biomedical Applications)
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<p>Density versus the P/Al molar ratio of the three solutions.</p> Full article ">Figure 2
<p><sup>27</sup>Al (<b>a</b>) and <sup>31</sup>P (<b>b</b>) MAS-NMR spectra obtained at 700 °C on Al/P = 3 (bottom), 3.2 (middle), and 3.5 (top) solutions.</p> Full article ">Figure 3
<p><sup>27</sup>Al (<b>a</b>) and <sup>31</sup>P (<b>b</b>) MAS-NMR spectra obtained at 500 °C on Al/P = 3 (bottom), 3.2 (middle), and 3.5 (top) solutions.</p> Full article ">Figure 4
<p><sup>27</sup>Al (<b>a</b>) and <sup>31</sup>P (<b>b</b>) MAS-NMR spectra obtained at 500 °C on the P/Al = 3 solution with 10 °C (bottom), 1 °C (middle), and 0.2 °C (top)/min heating rate. The dwell time is similar for the three experiments (1 h), leading to different total treatment times.</p> Full article ">Figure 5
<p>1D 27Al(31P) D-HMQC (<b>a</b>) and 27Al (<b>b</b>) MAS-NMR spectra obtained at 500 °C on the P/Al = 3 solution with 10 °C/min.</p> Full article ">Figure 6
<p><sup>27</sup>Al (<b>a</b>) and <sup>31</sup>P (<b>b</b>) MAS-NMR spectra obtained at 500 °C on the P/Al = 3 solution with 10 °C/(bottom), 1 °C (middle), and 0.2 °C (top)/min heating rate. The dwell times are different and lead to a similar total treatment time of 41 h for the three samples.</p> Full article ">Figure 7
<p>Binders compositions in mol% derived from the <sup>31</sup>P MAS-NMR spectra decompositions. Only compounds with relative proportion higher than 1% were taken into account, and only binders prepared with a dwell time of 1 h are reported. Errors on the mol% are estimated to +/−3%.</p> Full article ">
12 pages, 32547 KiB  
Article
Fabrication of MnCuNiFe–CuAlNiFeMn Gradient Alloy by Laser Engineering Net Shaping System
by Kuo Yan, Zaiwen Lin, Meng Chen, Yuren Wang, Jun Wang and Heng Jiang
Materials 2022, 15(6), 2336; https://doi.org/10.3390/ma15062336 - 21 Mar 2022
Cited by 4 | Viewed by 2525
Abstract
Marine noise pollution generated by propellers is of wide concern. Traditional propeller materials (nickel–aluminum bronze (NAB) alloys) can no longer meet the requirements for reducing shaft vibration. However, the Mn–Cu alloy developed to solve the problem of propeller vibration is affected by seawater [...] Read more.
Marine noise pollution generated by propellers is of wide concern. Traditional propeller materials (nickel–aluminum bronze (NAB) alloys) can no longer meet the requirements for reducing shaft vibration. However, the Mn–Cu alloy developed to solve the problem of propeller vibration is affected by seawater corrosion, which greatly limits the application of the alloy in the field of marine materials. In this study, the M2052–NAB gradient alloy was developed for the first time using LENS technology to improve the corrosion resistance while retaining the damping properties of the M2052 alloy. We hope this alloy can provide a material research basis for the development of low-noise propellers. This study shows that, after solution-aging of M2052 alloy as the matrix, the martensitic transformation temperature increased to approach the antiferromagnetic transformation temperature, which promoted twinning and martensitic transformation. The aging process also eliminated dendrite segregation, promoted the equiaxed γ-MnCu phase, and increased the crystal size to reduce the number of dislocations, resulting in obvious modulus softening of the alloy. NAB after deposition had higher hardness and good corrosion resistance than the as-cast alloy, which offers good corrosion protection for the M2052 alloy. This research provides new material options for the field of shipbuilding. Full article
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<p>Particle morphologies of (<b>a</b>) M2052 and (<b>b</b>) NAB.</p> Full article ">Figure 2
<p>Relationship between tan δ, Young’s modulus, and temperature of the M2052 alloy (<b>a</b>) as-deposited and (<b>b</b>) after aging. Relationship between d<span class="html-italic">E</span>/d<span class="html-italic">T</span> and temperature of M2052 alloy (<b>c</b>) as-deposited and (<b>d</b>) after aging.</p> Full article ">Figure 3
<p>Microstructures of M2052 (<b>a</b>) as-deposited and (<b>b</b>) after aging.</p> Full article ">Figure 4
<p>Microstructures of (<b>a</b>) M2052–NAB gradient alloy, (<b>b</b>) transition zone, (<b>c</b>) NAB alloy, and (<b>d</b>) NAB alloy surface pore defects, (<b>e</b>) Grain size distribution of M2052–NAB alloy.</p> Full article ">Figure 5
<p>X-ray diffraction patterns of NAB, M2052, and M2052–NAB gradient alloy.</p> Full article ">Figure 6
<p>Changes in element concentrations from M2052 to NAB across the interface, as measured by energy-dispersive spectroscopy.</p> Full article ">Figure 7
<p>Microhardness of graded material from M2052 to NAB.</p> Full article ">Figure 8
<p>(<b>a</b>) Stable open circuit potential of NAB deposited by LENS in 3.5% NaCl. (<b>b</b>) Dynamic polarization curve of electrochemical corrosion of NAB.</p> Full article ">
14 pages, 4575 KiB  
Article
Immobilization of Hexavalent Chromium Using Self-Compacting Soil Technology
by Zymantas Rudzionis, Arunas Aleksandras Navickas, Gediminas Stelmokaitis and Remigijus Ivanauskas
Materials 2022, 15(6), 2335; https://doi.org/10.3390/ma15062335 - 21 Mar 2022
Cited by 4 | Viewed by 2040
Abstract
A study of immobilization of hexavalent chromium in the form of Na2CrO4 salt by self-compacting soils (SCS) is presented. Carbofill E additive was used as SCS binder. The efficiency of immobilization of Cr (VI) was evaluated by washing out chromium [...] Read more.
A study of immobilization of hexavalent chromium in the form of Na2CrO4 salt by self-compacting soils (SCS) is presented. Carbofill E additive was used as SCS binder. The efficiency of immobilization of Cr (VI) was evaluated by washing out chromium compounds from SCS samples. The influence of the nature of the soil and the content of Carbofill E and Na2CrO4 in the SCS samples on the efficiency of Cr (VI) immobilization was studied. It was found that the nature of the soil and the content of Carbofill E in the SCS samples affect the immobilization of Cr (VI). Moreover, increasing the Carbofill E content in SCS samples further increases Cr (VI) immobilization. X-ray diffraction studies of the samples with immobilized hexavalent chromium showed that part of the sample transforms from a readily soluble form of salt into oxide forms of chromium and calcium-chromium, which are practically insoluble in water. Full article
(This article belongs to the Special Issue Research on Novel Sustainable Binders, Concretes and Composites)
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<p>Scheme for washing out Cr (VI) compounds from self-compacting soils (SCS) samples: 1—polyethylene container; 2—circulating water pump to create a flow of flushing water; 3—SCS supporting structure; 4—sample SCS; 5—thermostat for maintaining constant temperature; 6—cover; M1—sample wash water, M2—sample.</p> Full article ">Figure 2
<p>Compressive strength (samples of SCS with sandy soil and 10%, 15%, 20% Carbofill E binder) development with time.</p> Full article ">Figure 3
<p>Compressive strength (samples of SCS with clay soil and 10%, 15%, 20% Carbofill E binder) development with time.</p> Full article ">Figure 4
<p>Density of SCS with sandy and clay soils corresponding to the amount of Carbofill E binder.</p> Full article ">Figure 5
<p>Water permeability of SCS with sandy and clay soil corresponding to the amount of Carbofill E binder.</p> Full article ">Figure 6
<p>Washing out of chromium compounds from SCS sandy samples with immobilized Cr (VI) 3000 mg/kg and various amounts of Carbofill E. Samples: uncrushed—(<b>a</b>); crushed—(<b>b</b>).</p> Full article ">Figure 7
<p>Washing out of chromium compounds from SCS clay samples with immobilized Cr (VI) 3000 mg/kg and various amounts of Carbofill E. Samples: uncrushed—(<b>a</b>); crushed—(<b>b</b>).</p> Full article ">Figure 8
<p>Washing out of chromium compounds from SCS sandy samples with immobilized various amounts of Cr (VI) and 10% Carbofill E. Samples: uncrushed—(<b>a</b>); crushed—(<b>b</b>).</p> Full article ">Figure 9
<p>X-ray diffractograms of sandy SCS samples with different amounts of additives: 1–10% Carbofill E and Cr (VI) 3000 mg/kg; 2–20% Carbofill E and Cr (VI) 3000 mg/kg; 3–10% Carbofill E and Cr(VI) 30,000 mg/kg. The peaks were identified and assigned as follows: (○) quartz SiO<sub>2</sub> 83–539; (▲) wollastonite 2M (<span class="html-italic">monoclinic</span>) CaSiO<sub>3</sub> 84–655; (△) wollastonite 2M (<span class="html-italic">monoclinic</span>) Ca<sub>3</sub>(Si<sub>3</sub>O<sub>9</sub>) 76–1846; (●) calcium chromium oxide (<span class="html-italic">hexagonal</span>) Ca<sub>5</sub>(CrO<sub>4</sub>)<sub>3</sub>O<sub>0.5</sub> 38–294; (<b>✳</b>) chromium oxide (<span class="html-italic">rhombohedral</span>) Cr<sub>2</sub>O<sub>3</sub> 84-315.</p> Full article ">Figure 10
<p>X-ray diffractograms of clay SCS samples with Cr (VI) 3000 mg/kg and different amounts of Carbofill E: 1–10% 2–20%. The peaks were identified and assigned as follows: (○) quartz (<span class="html-italic">hexagonal</span>) SiO<sub>2</sub> 83–539; (▲) wollastonite 2M (<span class="html-italic">monoclinic</span>) CaSiO<sub>3</sub> 84–655; (△) wollastonite 2M (<span class="html-italic">monoclinic</span>) Ca<sub>3</sub>(Si<sub>3</sub>O<sub>9</sub>) 76–1846; (●) calcium chromium oxide (<span class="html-italic">hexagonal</span>) Ca<sub>5</sub>(CrO<sub>4</sub>)<sub>3</sub>O<sub>0.5</sub> 38–294.</p> Full article ">
18 pages, 50179 KiB  
Article
Assessment of the Impact of Wear of the Working Surface of Rolls on the Reduction of Energy and Environmental Demand for the Production of Flat Products: Methodological Approach
by Mariusz Niekurzak and Ewa Kubińska-Jabcoń
Materials 2022, 15(6), 2334; https://doi.org/10.3390/ma15062334 - 21 Mar 2022
Cited by 5 | Viewed by 2678
Abstract
An important element in the correct operation of the rolling mill is appropriate planning of the condition of the rolls because this factor constitutes a limiting element in the production process. In this work, with the aim of indicating the method of proper [...] Read more.
An important element in the correct operation of the rolling mill is appropriate planning of the condition of the rolls because this factor constitutes a limiting element in the production process. In this work, with the aim of indicating the method of proper use of production tools–metallurgical rollers during their operation in a Polish rolling mill, the wear and tear of particular kinds of rollers built in the whole rolling set was determined. For this purpose, data were collected at the strip mill from grinding processes, production reports and roll files, while our statistical analysis, laboratory calculations and measurements were used. These data were used to perform computer calculations on the service life of metallurgical rollers installed in the rolling line. Wear mechanisms were identified in industrial practice. The characteristic features of roller wear were investigated using non-destructive tests, including eddy currents. The laboratory tests reproduced the wear mechanisms in very hot rolling rolls. The statistical method for determining the service life of working rolls indicated that their reconstruction is determined both by natural physical phenomena and inappropriate use in about 30% of cases, mainly in the F5 and F6 cages of the finishing unit. Calculations indicated the possibility of replacing the working rolls made of high chromium cast iron Hi-Cr with those made of HSS in the F5 and F6 cages, which will contribute to an increase in the durability of the rolls, a reduction in production costs and a decrease in the number of roll rebuildings. The service life of HSS rolls is 14,000–20,000 Mg of rolled material per 1 mm of wear on its surface in the radial direction, compared to 2000 Mg for rolls made of high chromium cast iron Hi-Cr. The constructed model may be a source of information for further analyses and decision-making processes supporting the management of metallurgical enterprises. On the basis of the constructed model, it was shown that the analyzed projects, depending on their type and technical specification, will bring measurable economic benefits in the form of reduced annual energy consumption and environmental benefits in the form of reduced carbon dioxide emissions into the atmosphere. The constructed model of the roll consumption, verified in the real conditions of the rolling mills, will contribute to the fulfillment of energy and emission obligations with the EU. Full article
(This article belongs to the Special Issue Surface Engineering in Materials)
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<p>The sequence of phenomena while detecting inconsistency in a material. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 2
<p>Diagram of high chromium cast rolls local tear and wear levels. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 3
<p>Roller indentation defect mapped in 3D. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 4
<p>Diagram of faults level generated based on the map of faults for the high chromium Hi-Cr cast roll. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 5
<p>Diagram of defects of rolls made of high chromium cast iron Hi-Cr: (<b>a</b>) irregularities, (<b>b</b>) run-out. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 6
<p>Graph volume of local consumption for HSS rolling type. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 7
<p>Graph-level defects generated on the basis of faults map of type HSS. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 8
<p>Diagram of defects of rolls made of HSS high-speed steel: (<b>a</b>) out of roundness, (<b>b</b>) run-out. Source: own, based on [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 9
<p>Cross-section through a hardened cast iron cylinder after a campaign: (<b>a</b>) without etching, (<b>b</b>) with etching (2% Nital) [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">Figure 10
<p>Cross-section through a high-speed steel cylinder after a campaign: (<b>a</b>) without etching, (<b>b</b>) with etching (2% Nital) [<a href="#B38-materials-15-02334" class="html-bibr">38</a>].</p> Full article ">
15 pages, 3719 KiB  
Article
Binarization Mechanism Evaluation for Water Ingress Detectability in Honeycomb Sandwich Structure Using Lock-In Thermography
by Yoonjae Chung, Ranjit Shrestha, Seungju Lee and Wontae Kim
Materials 2022, 15(6), 2333; https://doi.org/10.3390/ma15062333 - 21 Mar 2022
Cited by 9 | Viewed by 2627
Abstract
The growing use of composite honeycomb structures in several industries including aircraft has demonstrated the need to develop effective and efficient non-destructive evaluation methods. In recent years, active thermography has attracted great interest as a reliable technology for non-destructive testing and evaluation of [...] Read more.
The growing use of composite honeycomb structures in several industries including aircraft has demonstrated the need to develop effective and efficient non-destructive evaluation methods. In recent years, active thermography has attracted great interest as a reliable technology for non-destructive testing and evaluation of composite materials due to its advantages of non-contact, non-destructive, full-area coverage, high speed, qualitative, and quantitative testing. However, non-uniform heating, low spatial resolution, and ambient environmental noise make the detection and characterization of defects challenging. Therefore, in this study, lock-in thermography (LIT) was used to detect water ingress into an aircraft composite honeycomb sandwich structure, and the phase signals were binarized through the Otsu algorithm. A square composite honeycomb with dimensions of 210 mm × 210 mm along with 16 different defective areas of various sizes in groups filled with water by 25%, 50%, 75%, and 100% of the cell volume was considered. The sample was excited at multiple modulation frequencies (i.e., 1 Hz to 0.01 Hz). The results were compared in terms of phase contrast and CNR according to the modulation frequency. In addition, the detectability was analyzed by comparing the number of pixels of water ingress in the binarized image and the theoretical calculation. Full article
(This article belongs to the Special Issue Non-Destructive Evaluation of Composite Materials)
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<p>Principle of the four-point method in lock-in thermography.</p> Full article ">Figure 2
<p>Schematic of the honeycomb-cored sandwich panel considering various water ingress conditions.</p> Full article ">Figure 3
<p>Aramid honeycomb-cored sandwich panel as a test sample. (<b>a</b>) The front face skin with CFRP and (<b>b</b>) the rear face skin with GFRP.</p> Full article ">Figure 4
<p>Experimental configuration of a lock-in thermography inspection system.</p> Full article ">Figure 5
<p>Phase images by the four-point method: (<b>a</b>) 1 Hz, (<b>b</b>) 0.5 Hz, (<b>c</b>) 0.2 Hz, (<b>d</b>) 0.1 Hz, (<b>e</b>) 0.07 Hz, (<b>f</b>) 0.05 Hz, (<b>g</b>) 0.03 Hz, (<b>h</b>) 0.01 Hz.</p> Full article ">Figure 6
<p>Representation of selected areas for contrast and CNR computation. The black dashed line enclosed area represents the water ingress areas and the red solid line enclosed area represents the sound areas.</p> Full article ">Figure 7
<p>Phase contrast with the four-point method as a function of modulation frequency.</p> Full article ">Figure 8
<p>Phase-contrast with four-point method as a function of modulation frequency.</p> Full article ">Figure 9
<p>Results of binarized images through Otsu algorithm processing: (<b>a</b>) 0.05 Hz, (<b>b</b>) 0.1 Hz, (<b>c</b>) 0.2 Hz.</p> Full article ">Figure 10
<p>A binarized image at a modulation frequency of 0.1 Hz to calculate the number of pixels in a region.</p> Full article ">Figure 11
<p>Error changes according to water ingress rate.</p> Full article ">
13 pages, 1466 KiB  
Article
Mortar Bond Strength: A Brief Literature Review, Tests for Analysis, New Research Needs and Initial Experiments
by Janaina Salustio, Sandro M. Torres, Anne C. Melo, Ângelo J. Costa e Silva, António C. Azevedo, Jennef C. Tavares, Matheus S. Leal and João M. P. Q. Delgado
Materials 2022, 15(6), 2332; https://doi.org/10.3390/ma15062332 - 21 Mar 2022
Cited by 12 | Viewed by 3297
Abstract
Despite technological advances in the production processes of the materials for ceramic façade coatings, the problems of detachments are still frequent. Therefore, this work aims to investigate, through a literature review, the existing gaps related to the adhesion ability of adhesive mortars, identifying [...] Read more.
Despite technological advances in the production processes of the materials for ceramic façade coatings, the problems of detachments are still frequent. Therefore, this work aims to investigate, through a literature review, the existing gaps related to the adhesion ability of adhesive mortars, identifying new research needs that can better explain the behavior of the material. In addition, an experimental procedure was developed to evaluate the mechanical capacity of adhesive mortars when subjected to cyclic stresses. Dynamic stress measurements are presented for several blocks of mortar and on similar blocks but with a slot drilled prior to measurements (intended to represent failure). From these data we calculated values of stress energy, elastic energy, and dissipated energy. The experimental results showed that the energy involved in the test process accompanied the load values and current stress values. The mortar samples with the previous failure absorbed and dissipated less energy than mortars without failure, showing that materials that have less energy to dissipate, are materials that have developed less capacity to adhere, that is, to keep their parts together. Full article
(This article belongs to the Special Issue Developments in Fiber-Reinforced Cement)
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<p>Prismatic sticky mortar samples: (<b>A</b>) detail of the slot with 9 mm height and (<b>B</b>) example of a sample fitted for the tests and the equipment used.</p> Full article ">Figure 2
<p>Hysteresis curves of the bending tensile strength test with cyclic loads of Solid-B samples: (<b>A</b>) 1000 cycles, (<b>B</b>) 2000 cycles, (<b>C</b>) 3000 cycles, and (<b>D</b>) 4000 cycles.</p> Full article ">Figure 3
<p>The central section of the hysteresis curves of the bending tensile strength test with cyclic loads of the Solid-B samples: (<b>A</b>) all 6000 cycles, (<b>B</b>) 1000 cycles, (<b>C</b>) 2000 cycles, (<b>D</b>) 3000 cycles, and (<b>E</b>) 4000 cycles.</p> Full article ">Figure 4
<p>Single crack formed during the test: (<b>A</b>) sample after test; and (<b>B</b>) detail of the slot formed in the central axis of the previous failure.</p> Full article ">
23 pages, 101382 KiB  
Article
Functioning of Heat Accumulating Composites of Carbon Recyclate and Phase Change Material
by Michał Musiał and Agnieszka Pękala
Materials 2022, 15(6), 2331; https://doi.org/10.3390/ma15062331 - 21 Mar 2022
Cited by 6 | Viewed by 2208
Abstract
The article presents the results of experimental research together with the development of a response function presenting the thermal functioning of a new composite of a phase change material with carbon recyclate. The empirical research proved the improvement of the thermal functioning of [...] Read more.
The article presents the results of experimental research together with the development of a response function presenting the thermal functioning of a new composite of a phase change material with carbon recyclate. The empirical research proved the improvement of the thermal functioning of the phase change material as a result of modifying its structure with carbon-based recycling material. The conducted experimental tests and statistical analysis proved that the obtained innovative composite is characterized by a more effective distribution of stored heat than the pure phase change material, which resulted in reduction of the heating and cooling time of the package by 10 min. The obtained innovative composite can improve the thermal efficiency of short-term heat storage systems, both in building components and in elements of heating and cooling systems, and translates into their increase in thermal efficiency. Full article
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<p>Scheme of the research approach.</p> Full article ">Figure 2
<p>(<b>a</b>) Raw recyclate; (<b>b</b>) Preparation of experimental samples.</p> Full article ">Figure 3
<p>Graphical diagram of the stellar ray of an incomplete, polyselective, orthogonal plan experiment plan.</p> Full article ">Figure 4
<p>List of experiments necessary to perform, according to the incomplete experiment plan of the Statistica program.</p> Full article ">Figure 5
<p>Summary of the effects of input variables and their correlations analyzed in the experiment plan in the Statistica program.</p> Full article ">Figure 6
<p>(<b>a</b>) A photograph of the Espec climatic chamber during the research; (<b>b</b>) Scheme of the test stand, where: 1, recorder; 2, interior of the climate chamber; 3, research samples of the PCM composite with recyclate; 4, pure PCM test samples; 5, temperature sensors; 6, heat flux density sensors.</p> Full article ">Figure 7
<p>(<b>a</b>) Experimental samples containing pure PCM; (<b>b</b>) test samples containing PCM with carbon recyclate.</p> Full article ">Figure 8
<p>The nature of the microstructural surfaces of the waste material. SEM image: (<b>a</b>) semicircular shell fracture, (<b>b</b>) surfaces with a spiked, uneven fracture, (<b>c</b>) oval, unfilled pores.</p> Full article ">Figure 8 Cont.
<p>The nature of the microstructural surfaces of the waste material. SEM image: (<b>a</b>) semicircular shell fracture, (<b>b</b>) surfaces with a spiked, uneven fracture, (<b>c</b>) oval, unfilled pores.</p> Full article ">Figure 9
<p>Chemical analysis from the point of analyzed waste. EDS.</p> Full article ">Figure 10
<p>Surface distribution of the identified elements.</p> Full article ">Figure 11
<p>Distribution of individual elements identified on the microstructural surface; (<b>a</b>) carbon; (<b>b</b>) calcium; (<b>c</b>) cupper; (<b>d</b>) sulfur; (<b>e</b>) silicon.</p> Full article ">Figure 12
<p>Chart of recorded temperature changes of pure PCM packets and packets with PCM composite with carbon recyclate during their heating and cooling according to the assumptions of experiment No. 6.</p> Full article ">Figure 13
<p>Thermograms of heating and cooling samples with pure PCM and with composite PCM and coke recyclate. (<b>a</b>) steady state before heating, (<b>b</b>) initial heating phase, (<b>c</b>) steady state after sample heating, (<b>d</b>) start of sample cooling, (<b>e</b>) start of sample cooling, (<b>f</b>) the final stage of cooling the samples.</p> Full article ">Figure 13 Cont.
<p>Thermograms of heating and cooling samples with pure PCM and with composite PCM and coke recyclate. (<b>a</b>) steady state before heating, (<b>b</b>) initial heating phase, (<b>c</b>) steady state after sample heating, (<b>d</b>) start of sample cooling, (<b>e</b>) start of sample cooling, (<b>f</b>) the final stage of cooling the samples.</p> Full article ">Figure 14
<p>List of empirically determined heat distribution coefficients for the PCM composite with coke recyclate.</p> Full article ">Figure 15
<p>Pareto diagram of the influence of the analyzed input quantities and their correlation on the value of the output expression.</p> Full article ">Figure 16
<p>Summary of independent variable assessments on the baseline quantity.</p> Full article ">Figure 17
<p>Summary of the results of ANOVA analysis of input variables on the value of the output variable, where: df, degrees of freedom; MS, pure error; SS, variance; F, statistic value, coefficient informing about the contribution of a given variable to the prediction; p, significance level, coefficient correlation; R<sup>2</sup>, regression coefficient.</p> Full article ">Figure 18
<p>Pareto diagram of the influence of the analyzed input quantities and their correlationswith the value of the output expression, excluding insignificant quantities.</p> Full article ">Figure 19
<p>Summary of independent variables assessments on the output quantity, excluding insignificant quantities.</p> Full article ">Figure 20
<p>Summary of the results of the ANOVA analysis of the input variables on the value of the output variable, excluding insignificant quantities.</p> Full article ">Figure 21
<p>Formation of graphs of approximating functions in the form of planes of input variable responses to the value of the heat distribution coefficient of the PCM composite with carbon recyclate, (<b>a</b>) The plane of the heating temperature response to the geometrical coefficient, (<b>b</b>) The plane of the heating temperature response to the initiation temperature, (<b>c</b>) The plane of geometrical coefficient response to the heating temperature, (<b>d</b>) The plane of geometrical coefficient response to the initiation temperature, (<b>e</b>) The plane of the initiation temperature response to the heating temperature, (<b>f</b>) The plane of the initiation temperature response to geometrical coefficient.</p> Full article ">Figure 22
<p>(<b>a</b>) The results of the test for fitting the theoretical quantities to the empirical heat distribution coefficient for pure PCM packages (<b>b</b>) The results of the test of fitting the theoretical values to the empirical heat distribution coefficient for packages with PCM and carbon recyclate.</p> Full article ">
14 pages, 13113 KiB  
Article
Nonlinear Optical Limiting and Radiation Shielding Characteristics of Sm2O3 Doped Cadmium Sodium Lithium Borate Glasses
by Aljawhara H. Almuqrin, Jagannath Gangareddy, Mahesh M. Hivrekar, A. G. Pramod, M. I. Sayyed, K. Keshavamurthy, Naseem Fatima and K. M. Jadhav
Materials 2022, 15(6), 2330; https://doi.org/10.3390/ma15062330 - 21 Mar 2022
Cited by 12 | Viewed by 2086
Abstract
Strong nonlinear absorption (NLA), reduced optical limiting (OL) thresholds, and high radiation shielding parameters are required for the effective use of glasses in the laser radiation and nuclear radiation protecting materials. In view of this, the efficacy of Sm2O3 on [...] Read more.
Strong nonlinear absorption (NLA), reduced optical limiting (OL) thresholds, and high radiation shielding parameters are required for the effective use of glasses in the laser radiation and nuclear radiation protecting materials. In view of this, the efficacy of Sm2O3 on the nonlinear optical (NLO) and OL properties were ascertained (at 532 nm) along with radiation shielding characteristics. The open and closed aperture Z-scan profiles revealed the presence of positive NLA and nonlinear refraction (NLR) phenomena respectively. OL measurements showed the existence of limiting behavior in the studied glasses. The NLA and NLR coefficients were improved while the OL thresholds were decreased as the doping of Sm2O3 elevated to a higher doping level. These improvements in NLA, NLR coefficients and OL efficiencies were attributed to the non-bridging oxygens and high polarizable Sm3+ ions. The NLA and OL results clearly suggest the high (5 mol %) Sm2O3 doped glass (Sm5CNLB) glass is beneficial to protect the delicate devices and human eye by suppressing the high energy laser light. The theoretical linear attenuation coefficients (LAC) values of the presented SmxCNLB glasses were obtained with the help of Phy-X software between 0.284 and 1.333 MeV. At 0.284 MeV, the maximum values occur and take values between 0.302 (for Sm0CNLB) and 0.409 cm−1 (for Sm5CNLB). We found that the LAC for the presented SmxCNLB glasses is a function of Sm2O3 content, where the LAC tends to increase, corresponding to the high probabilities of interaction, as the content of Sm2O3 changes from 0 to 5 mol %. The effective atomic number (Zeff) for the presented SmxCNLB glasses was examined between 0.284 and 1.333 MeV. As the amount of Sm2O3 is added, the Zeff increases, and this was observed at any energy. Full article
(This article belongs to the Special Issue Fabrications and Characterization of Different Glasses Systems)
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<p>FTIR spectral outcomes of Sm0CNLB and Sm3CNLB glass specimens.</p> Full article ">Figure 2
<p>OA Z-scan outcomes of studied Sm<span class="html-italic">x</span>CNLB glasses, where <span class="html-italic">x</span> = 0, 1, 2, 3, 4 and 5 mol %. The symbols and solid lines indicate the experimental and theoretical OA Z-scan data, respectively.</p> Full article ">Figure 3
<p>Variation of <span class="html-italic">α</span><sub>2</sub> with respect to Sm<sub>2</sub>O<sub>3</sub> content in the glass composition.</p> Full article ">Figure 4
<p>CA Z-scan profiles of studied Sm<span class="html-italic">x</span>CNLB glasses, where <span class="html-italic">x</span> = 0, 1, 2, 3, 4, and 5 mol %. The symbols and thick lines indicate the experimental and theoretical CA Z-scan data respectively.</p> Full article ">Figure 5
<p>Variation of n2 as the function of Sm<sub>2</sub>O<sub>3</sub> content in the glass composition.</p> Full article ">Figure 6
<p>(<b>a</b>) OL patterns of examined Sm<span class="html-italic">x</span>CNLB glasses, where <span class="html-italic">x</span> = 0, 1, 2, 3, 4, and 5 mol %. (<b>b</b>) Variation of OL thresholds with Sm<sub>2</sub>O<sub>3</sub> content in the glass composition. The solid symbols and solid lines in (<b>a</b>) represent the measured and theoretical OL data respectively.</p> Full article ">Figure 7
<p>The theoretical linear attenuation coefficient values of the presented Sm<span class="html-italic">x</span>CNLB glasses.</p> Full article ">Figure 8
<p>The effective atomic number values of the presented Sm–CNLB glasses.</p> Full article ">Figure 9
<p>The mean free path (MFP) of the Sm<span class="html-italic">x</span>CNLB glasses.</p> Full article ">Figure 10
<p>The relation between the half value layer and the Sm<sub>2</sub>O<sub>3</sub> content in the Sm<span class="html-italic">x</span>CNLB glasses.</p> Full article ">
19 pages, 8672 KiB  
Article
Numerical Simulation of Damage Evolution and Electrode Deformation of X100 Pipeline Steel during Crevice Corrosion
by Wenxian Su and Zhikuo Liu
Materials 2022, 15(6), 2329; https://doi.org/10.3390/ma15062329 - 21 Mar 2022
Cited by 5 | Viewed by 2364
Abstract
In this paper, the spatial and temporal damage evolution was described during crevice corrosion through developing a two-dimensional (2-D) model. COMSOL code was used to simulate the crevice corrosion regulated by the I∙R voltage of nickel (Ni) metal in sulfuric acidic. The electrode [...] Read more.
In this paper, the spatial and temporal damage evolution was described during crevice corrosion through developing a two-dimensional (2-D) model. COMSOL code was used to simulate the crevice corrosion regulated by the I∙R voltage of nickel (Ni) metal in sulfuric acidic. The electrode deformation, potential and current curves, and other typical characteristics were predicted during crevice corrosion, where results were consistent with published experimental results. Then, based on the Ni model, the damage evolution of X100 crevice corrosion in CO2 solution was simulated, assuming uniform distribution of solution inside and outside the crevice. The results showed that over time, the surface damage of Ni electrode increased under a constant applied potential. As the gap increased, the critical point of corrosion (CPC) inside the crevice moved into a deeper location, and the corrosion damage area (CDA) gradually expanded, but the threshold value of corrosion damage remained almost unchanged. The CDA inside the crevice extended toward the opening and the tip of crevice. Since the potential drop in this region increases with increasing current, the passivation potential point moved towards the opening. As the gap increased and the electrolyte resistance decreased, the critical potential for reaching the maximum corrosion rate moved into a deeper location. It is significant for predicting the initial damage location and the occurrence time of surface damage of crevice corrosion through the 2-D model that is not available through the one-dimensional simplified model. Full article
(This article belongs to the Special Issue Structural Strength, Corrosion and Failure Analysis of Pressure Vessel and Pipeline System)
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<p>2-D electrochemical model for corrosion. The gray area is electrolyte. Not to scale.</p> Full article ">Figure 2
<p>Polarization curve for Ni electrode in sulfuric acid along the active-to-passive direction from Brackman [<a href="#B33-materials-15-02329" class="html-bibr">33</a>], indicating the critical potential, <span class="html-italic">E<sub>crit</sub></span> = 0.108 V, and passive potential, <span class="html-italic">E<sub>pass</sub></span> = 0.20 V.</p> Full article ">Figure 3
<p>The PBCs of inside and outside the crevice: (<b>a</b>) Part I; (<b>b</b>) Part II.</p> Full article ">Figure 4
<p>Potential curves with varying crevice width <span class="html-italic">W</span>, at time <span class="html-italic">t</span> = 0 h: (<b>a</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.25 V; (<b>b</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.30 V.</p> Full article ">Figure 5
<p>Potential E<sub>SCE</sub> and current density for time <span class="html-italic">t</span> = 0 and <span class="html-italic">W</span> = 0.3 mm: (<b>a</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.25 V; (<b>b</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.30 V.</p> Full article ">Figure 6
<p>Curves of potential versus depth for the width <span class="html-italic">W</span> = 0.3 mm at various times: (<b>a</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.25 V; (<b>b</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.30 V.</p> Full article ">Figure 7
<p>Comparison of potential with experimental results from Abdulsalam [<a href="#B35-materials-15-02329" class="html-bibr">35</a>].</p> Full article ">Figure 8
<p>Current density with time for <span class="html-italic">W</span> = 0.3 mm: (<b>a</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.25 V; (<b>b</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.30 V.</p> Full article ">Figure 9
<p>Distribution of current density at time 50 h.</p> Full article ">Figure 10
<p>The crevice damage evolution inside the gap over time. (<b>a</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.25 V; (<b>b</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.30 V.</p> Full article ">Figure 11
<p>Comparison damage evolution with the result from Abdulsalam [<a href="#B35-materials-15-02329" class="html-bibr">35</a>]. The applied potential at time 50 h is 0.25 V, and the potential of the 150 h is 0.30 V.</p> Full article ">Figure 12
<p>Electrode damage as a function of crevice width after 50 h: (<b>a</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.25 V; (<b>b</b>) the applied potential <span class="html-italic">E<sub>A</sub></span> = 0.30 V.</p> Full article ">Figure 13
<p>2D electrochemical model for X100 crevice corrosion: (<b>a</b>) the geometric model; (<b>b</b>) the meshed model.</p> Full article ">Figure 14
<p>Anodic polarization curve of X100 in 0.5 mol/L Na<sub>2</sub>SO<sub>4</sub> saturated CO<sub>2</sub> solution at 20 °C.</p> Full article ">Figure 15
<p>Damage evolution of X100 crevice corrosion at width <span class="html-italic">W</span> = 0.1 mm: (<b>a</b>) 0 weeks; (<b>b</b>) 10 weeks; (<b>c</b>) 20 weeks; (<b>d</b>) 30 weeks; (<b>e</b>) 40 weeks; (<b>f</b>) 50 weeks.</p> Full article ">Figure 16
<p>Damage evolution of X100 steel crevice corrosion at width <span class="html-italic">W</span> = 0.15 mm: (<b>a</b>) 0 weeks; (<b>b</b>) 10 weeks; (<b>c</b>) 20 weeks; (<b>d</b>) 30 weeks; (<b>e</b>) 40 weeks; (<b>f</b>) 50 weeks.</p> Full article ">Figure 17
<p>Damage evolution of X100 crevice corrosion at width <span class="html-italic">W</span> = 0.20 mm: (<b>a</b>) 0 weeks; (<b>b</b>) 10 weeks; (<b>c</b>) 20 weeks; (<b>d</b>) 30 weeks; (<b>e</b>) 40 weeks; (<b>f</b>) 50 weeks.</p> Full article ">Figure 18
<p>Damage evolution of X100 crevice corrosion at width <span class="html-italic">W</span> = 0.25 mm: (<b>a</b>) 0 weeks; (<b>b</b>) 10 weeks; (<b>c</b>) 20 weeks; (<b>d</b>) 30 weeks; (<b>e</b>) 40 weeks; (<b>f</b>) 50 weeks.</p> Full article ">Figure 19
<p>The distribution of damage curves inside the crevice over time (<span class="html-italic">d</span> denotes damage profile and <span class="html-italic">L</span> denotes crevice depth): (<b>a</b>) <span class="html-italic">W</span> = 0.1 mm; (<b>b</b>) <span class="html-italic">W</span> = 0.15 mm; (<b>c</b>) <span class="html-italic">W</span> = 0.2 mm; (<b>d</b>) <span class="html-italic">W</span> = 0.25 mm.</p> Full article ">Figure 20
<p>Damage profiles inside the crevice as a function of width <span class="html-italic">W</span> at time <span class="html-italic">t</span> = 50 weeks.</p> Full article ">
32 pages, 4350 KiB  
Article
Strengthening of Reinforced Concrete Beams Subjected to Concentrated Loads Using Externally Bonded Fiber Composite Materials
by Paolo Foraboschi
Materials 2022, 15(6), 2328; https://doi.org/10.3390/ma15062328 - 21 Mar 2022
Cited by 12 | Viewed by 3710
Abstract
Renovation, restoration, remodeling, refurbishment, and the retrofitting of buildings often imply applying forces (i.e., concentrated loads) to beams that before were subjected to distributed loads only. In the case of reinforced concrete structures, the new condition causes a beam to bear a concentrated [...] Read more.
Renovation, restoration, remodeling, refurbishment, and the retrofitting of buildings often imply applying forces (i.e., concentrated loads) to beams that before were subjected to distributed loads only. In the case of reinforced concrete structures, the new condition causes a beam to bear a concentrated load with the crack pattern that resulted from the distributed loads which had acted before. If the concentrated load is applied at or near the beam’s midspan, the new shear demand reaches the maximum where cracks are vertical or quasi-vertical, and where inclined bars are not common according to any standards. So, the actual shear capacity can be substantially lower than new shear demand due to the concentrated load. This paper focuses on reinforced concrete beams whose load distribution has to be changed from distributed to concentrated and presents a design method to bring the beam’s shear capacity up to the new demand. The method consists of applying fiber composites (fiber-reinforced polymers or fiber-reinforced cementitious material) with fibers at an angle of 45° bonded to the beam’s web. This kind of external reinforcement arrangement has to comply with some practical measures, which are presented as well. The paper also provides the analytical model that predicts the concentrated load-carrying capacity of a beam in the strengthened state. The model accounts for the crack’s verticality, which nullifies the contributions of steel stirrups, aggregate interlock, and dowel action, and for the effective bond length of each fiber, which depends on the distance between the ends of the fiber and the crack it crosses. Full article
(This article belongs to the Section Construction and Building Materials)
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Figure 1
<p>RC beam with vertical cracks around the midspan, which are spread along the length γ at spacing α. The upper diagram shows the loading condition that acted in the past and cracked the beam. The lower diagram shows the unstrengthened beam subjected to the new loading condition, i.e., the force <span class="html-italic">P</span> at point <span class="html-italic">k</span>, whose abscissa is β <span class="html-italic">L</span> (the beam could not bear that force). The figure also shows the span <span class="html-italic">L</span>, the depth <span class="html-italic">t</span> of the concrete cover, the crack depth ξ’, and the effective crack depth ξ. Failure is dictated by the shadowed cantilever.</p> Full article ">Figure 2
<p>Concrete cantilever that dictates the capacity of the RC beam. (<b>a</b>): beam without external reinforcement. (<b>b</b>): beam with side-bonded FRP reinforcement, whose fibers are at ±45° (the sign of the angle depends on which of the two sides of the web the fibers are bonded to).</p> Full article ">Figure 3
<p>Externally bonded reinforcement that strengthens the RC beam subjected to a concentrated load: fabric sheets composed of unidirectional fibers at an angle of + 45° with the beam’s axis, where the shear force is positive, and at −45°, where the shear force is negative.</p> Full article ">Figure 4
<p>Concrete cantilever that fails (the midspan of the beam is on the right of the figure). On the left: strain profile in the external reinforcement at the two cracked sections that define the lateral sides (boundaries) of the concrete cantilever. The strain is linear, starting from zero at the neutral axis up to <math display="inline"><semantics> <mrow> <msub> <mi mathvariant="sans-serif">ε</mi> <mrow> <mi>Fd</mi> </mrow> </msub> </mrow> </semantics></math> at the right crack and up to <math display="inline"><semantics> <mrow> <mo> </mo> <msubsup> <mi mathvariant="sans-serif">ε</mi> <mrow> <mi mathvariant="normal">F</mi> <mtext>-</mtext> <mi>max</mi> </mrow> <mo>′</mo> </msubsup> <mo>&lt;</mo> <mo> </mo> <msub> <mi mathvariant="sans-serif">ε</mi> <mrow> <mi>Fd</mi> </mrow> </msub> </mrow> </semantics></math> at the left crack. The external reinforcement bonded onto the concrete cover (which is shadowed) does not transmit any stress. On the right: forces transferred from the longitudinal steel bars (flexural reinforcement) and from the side-bonded reinforcement (the fibers are at 45°) to the concrete cantilever. The latter forces consist in a resisting contribution that makes the effects of the former forces less.</p> Full article ">Figure 5
<p>Fraction μ of μ’ that represents the effective height of the side-bonded fabric sheet, whereas the remaining part of μ’ is the anchorage (bond) length. The shadowed length <span class="html-italic">L<sub>d</sub></span> + <span class="html-italic">L<sub>d</sub></span> is the length of a fiber that crack opening causes to debond around the crack.</p> Full article ">Figure 6
<p>Forces applied to the concrete cantilever, internal actions, and maximum stress. The steel longitudinal bars and the side-bonded reinforcement induce the internal actions <span class="html-italic">M<sub>e</sub></span>, <span class="html-italic">N<sub>e</sub></span>, and <span class="html-italic">V<sub>e</sub></span> at the built-in end of the concrete cantilever. At debonding, <span class="html-italic">M<sub>e</sub></span> and <span class="html-italic">N<sub>e</sub></span> induce the maximum tension stress σ<sub>cm</sub>, which is shown in the figure, including the point where it occurs (shadowed circle).</p> Full article ">Figure 7
<p>Experimental verification of the analytical model performed by means of four specimens tested up to collapse. The four beams were initially subjected to a two-point load, which produced vertical cracks around the midspan. Then, two beams were left unstrengthened, and two beams were strengthened in the fashion described in <a href="#sec4-materials-15-02328" class="html-sec">Section 4</a> (side-bonded reinforcement). Finally, a vertical force was applied to the midspan of each beam (pistons and actuators are shown in the picture) and was increased to failure. Once the side-bonded reinforcement debonded, the applied load caused the entire beam to collapse. The last event that led to the collapse of the beam was debonding of the longitudinal external FRP reinforcement applied on the lower side of the beam. Nevertheless, debonding of the flexural FRP reinforcement occurred after debonding of the shear CFRM reinforcement, when the load-carrying capacity was almost zero.</p> Full article ">Figure 8
<p>Diagram of the four identical RC beams that were tested. The figure shows the span, the dimensions of the cross-section, the longitudinal steel bars, the steel stirrups, and the externally bonded flexural reinforcement. The symbol φ denotes the diameter of a steel bars and a stirrup. Vertical cracks were produced around the midspan with a specific loading. The diagram also shows those cracks and their spacing. A vertical force (shown in the diagram) was applied to the midspan of each beam and was increased to failure.</p> Full article ">
10 pages, 2768 KiB  
Article
Preparation and Properties of Pea Starch/ε-Polylysine Composite Films
by Zuolong Yu, Deping Gong, Chao Han, Yunxiao Wei, Changchun Fu, Xuejiao Xu and Youri Lu
Materials 2022, 15(6), 2327; https://doi.org/10.3390/ma15062327 - 21 Mar 2022
Cited by 8 | Viewed by 2680
Abstract
The composite films comprising pea starch (St) and ε-polylysine (PL) as the matrix and glycerol and sodium alginate as the plasticizers were investigated. The rheological properties, mechanical properties, Fourier transformed infrared spectroscopy, water vapor permeability (WVP), oil permeability, microstructure, thermogravimetry (TGA), and antimicrobial [...] Read more.
The composite films comprising pea starch (St) and ε-polylysine (PL) as the matrix and glycerol and sodium alginate as the plasticizers were investigated. The rheological properties, mechanical properties, Fourier transformed infrared spectroscopy, water vapor permeability (WVP), oil permeability, microstructure, thermogravimetry (TGA), and antimicrobial properties of the composite films were analyzed. The properties of the composite films with different mass ratios of St/PL varied significantly. First, the five film solutions were different pseudoplastic fluids. Additionally, as the mass ratio of PL increased, the tensile strength of the blends decreased from 9.49 to 0.14 MPa, the fracture elongation increased from 38.41 to 174.03%, the WVP increased, and the oil resistance decreased substantially. The films with a broad range of St/PL ratios were highly soluble; however, the solubility of the film with a St/PL ratio of 2:8 was reduced. Lastly, the inhibition of E. coli, B.subtilis, and yeast by the films increased with increasing mass ratios of PL, and the inhibition of B.subtilis was the strongest. Full article
(This article belongs to the Section Biomaterials)
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<p>Rheological curves of the film solutions with different St/PL mass ratios.</p> Full article ">Figure 2
<p>Mechanic curves of the composite films with different St/PL mass ratios.</p> Full article ">Figure 3
<p>FTIR spectra of the composite films with different St/PL mass ratios.</p> Full article ">Figure 4
<p>Water vapor permeability and oil permeability of the composite films with St/PL mass ratios.</p> Full article ">Figure 5
<p>TGA and DTA curves of the composite films with different St/PL mass ratios. (<b>a</b>) TGA. (<b>b</b>) DTG.</p> Full article ">Figure 6
<p>The SEM images of the composite films with different mass St/PL ratios. (a) Magnification ×10.</p> Full article ">Figure 7
<p>Antimicrobial activities of the composite films with different St/PL mass ratios with two bacteria and a fungus.</p> Full article ">
20 pages, 4259 KiB  
Article
Effectiveness of Some Novel Ionic Liquids on Mild Steel Corrosion Protection in Acidic Environment: Experimental and Theoretical Inspections
by Osama Al-Rashed and Ahmed Abdel Nazeer
Materials 2022, 15(6), 2326; https://doi.org/10.3390/ma15062326 - 21 Mar 2022
Cited by 21 | Viewed by 2620
Abstract
Three ionic liquids (ILs)—1-butyl-1-methyl-pyrrolidinium Imidazolate (BMPyrIM), 1-butyl-3-methyl-imidazolium Imidazolate (BMImIM), and bis(1-butyl-3-methyl-imidazolium Imidazolate) (BBMImIM)—were synthesized and examined experimentally and theoretically as potential inhibitors for mild steel corrosion in HCl (1.0 M) solution. To our knowledge, two of the [...] Read more.
Three ionic liquids (ILs)—1-butyl-1-methyl-pyrrolidinium Imidazolate (BMPyrIM), 1-butyl-3-methyl-imidazolium Imidazolate (BMImIM), and bis(1-butyl-3-methyl-imidazolium Imidazolate) (BBMImIM)—were synthesized and examined experimentally and theoretically as potential inhibitors for mild steel corrosion in HCl (1.0 M) solution. To our knowledge, two of the ILs successfully synthesized in our laboratory named BMPyrIM and BBMImIM are novel. Different electrochemical (potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS)), surface and structural (scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Atomic force microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR)) and theoretical (Density functional theory (DFT)) techniques were utilized to confirm their use as efficient environmentally safe inhibitors. These ionic liquids were designed to study the cation effect (imidazolium and pyrrolidinium) and the dimeric effect of the imidazolium-based IL. A pronounced inhibiting effect was recorded using the optimum concentration (5 × 10−3 M) of BBMImIM with protection efficiency of 98.6% compared to 94.3% and 92.4% for BMImIM and BMPyrIM, respectively. The investigated ILs act as a mixed-type corrosion inhibitors and their protection obeys Langmuir adsorption isotherm. The results obtained by SEM, EDS and AFM confirmed the mild steel protection by the formation of protective film of the ILs on the steel surface resulted in less damaged surfaces compared with the blank solution. Furthermore, quantum chemical calculations illustrated the electronic structure of the investigated ILs and their optimized adsorptiοn configurations on mild steel surface. The findings from the different techniques helped to provide a supported interpretation of the inhibition mechanism. Full article
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<p>Potentiodynamic polarization curves for mild steel in presence of 1M HCl alone (blank) and containing different concentrations of <b>BBMImIM</b> ionic liquid at 25 °C.</p> Full article ">Figure 2
<p>Langmuir isotherm for the studied ionic liquids (<b>BMPyrIM</b>, <b>BMImIM</b> and <b>BBMImIM</b>) adsorption on mild steel in 1 M HCl at 25 °C.</p> Full article ">Figure 3
<p>Nyquist plots for mild steel in presence of 1.0 M HCl alone and containing different concentrations of <b>BBMImIM</b> ionic liquid at 25 °C.</p> Full article ">Figure 4
<p>Equivalent circuit used for fitting the data.</p> Full article ">Figure 5
<p>Bode (<b>A</b>) and phase angle (<b>B</b>) plots for mild steel in presence of 1.0 M HCl alone and containing different concentrations of <b>BBMImIM</b> ionic liquid at 25 °C.</p> Full article ">Figure 5 Cont.
<p>Bode (<b>A</b>) and phase angle (<b>B</b>) plots for mild steel in presence of 1.0 M HCl alone and containing different concentrations of <b>BBMImIM</b> ionic liquid at 25 °C.</p> Full article ">Figure 6
<p>Scanning electron microscopy (SEM) images of the mild-steel in 1.0 M HCl alone (<b>A</b>) and containing 5 × 10<sup>−3</sup> M of <b>BMPyrIM</b> (<b>B</b>), <b>BMImIM</b> (<b>C</b>) and <b>BBMImIM</b> (<b>D</b>) ionic liquids at 25 °C for 24 h. Scale bar is 10 µm.</p> Full article ">Figure 7
<p>Energy-dispersive X-ray spectroscopy (EDS) images of the mild-steel in 1.0 M HCl containing 5 × 10<sup>−3</sup> M of <b>BMPyrIM</b> (<b>A</b>), <b>BMImIM</b> (<b>B</b>) and <b>BBMImIM</b> (<b>C</b>) ionic liquids at 25 °C after immersion for 24 h.</p> Full article ">Figure 7 Cont.
<p>Energy-dispersive X-ray spectroscopy (EDS) images of the mild-steel in 1.0 M HCl containing 5 × 10<sup>−3</sup> M of <b>BMPyrIM</b> (<b>A</b>), <b>BMImIM</b> (<b>B</b>) and <b>BBMImIM</b> (<b>C</b>) ionic liquids at 25 °C after immersion for 24 h.</p> Full article ">Figure 8
<p>The 2d and 3d Atomic force microscopy (AFM) micrographs of mild steel surface in 1.0 M HCl solution in the absence (<b>A</b>) and presence of 5 × 10<sup>−3</sup> M of <b>BMPyrIM</b> (<b>B</b>), <b>BMImIM</b> (<b>C</b>) and <b>BBMImIM</b> (<b>D</b>) after 24 h immersion.</p> Full article ">Figure 8 Cont.
<p>The 2d and 3d Atomic force microscopy (AFM) micrographs of mild steel surface in 1.0 M HCl solution in the absence (<b>A</b>) and presence of 5 × 10<sup>−3</sup> M of <b>BMPyrIM</b> (<b>B</b>), <b>BMImIM</b> (<b>C</b>) and <b>BBMImIM</b> (<b>D</b>) after 24 h immersion.</p> Full article ">Figure 9
<p>Fourier Transform Infrared Spectroscopy (ATR-FTIR) spectrum for <b>BBMImIM</b> (<b>A</b>), <b>BMImIM</b> (<b>B</b>) and <b>BMPyrIM</b> (<b>C</b>) as a pure and adsorbed on the mild steel surface after immersion for 24 h.</p> Full article ">Figure 9 Cont.
<p>Fourier Transform Infrared Spectroscopy (ATR-FTIR) spectrum for <b>BBMImIM</b> (<b>A</b>), <b>BMImIM</b> (<b>B</b>) and <b>BMPyrIM</b> (<b>C</b>) as a pure and adsorbed on the mild steel surface after immersion for 24 h.</p> Full article ">Figure 10
<p>The optimized molecular structures, HOMO and LUMO of the investigated ILs (<b>BMPyrIM</b>, <b>BMImIM</b> and <b>BBMImIM</b>). Blue and yellow isosurfaces of the HOMO and LUMO denote positive and negative wavefunction phases, respectively, using Dmol<sup>3</sup> module.</p> Full article ">
13 pages, 6954 KiB  
Article
A Numerical Analysis of Ductile Deformation during Nanocutting of Silicon Carbide via Molecular Dynamics Simulation
by Bing Liu, Xiaolin Li, Ruijie Kong, Haijie Yang and Lili Jiang
Materials 2022, 15(6), 2325; https://doi.org/10.3390/ma15062325 - 21 Mar 2022
Cited by 6 | Viewed by 2779
Abstract
As a typical third-generation semiconductor material, silicon carbide (SiC) has been increasingly used in recent years. However, the outstanding performance of SiC component can only be obtained when it has a high-quality surface and low-damage subsurface. Due to the hard–brittle property of SiC, [...] Read more.
As a typical third-generation semiconductor material, silicon carbide (SiC) has been increasingly used in recent years. However, the outstanding performance of SiC component can only be obtained when it has a high-quality surface and low-damage subsurface. Due to the hard–brittle property of SiC, it remains a challenge to investigate the ductile machining mechanism, especially at the nano scale. In this study, a three-dimensional molecular dynamics (MD) simulation model of nanometric cutting on monocrystalline 3C-SiC was established based on the ABOP Tersoff potential. Multi-group MD simulations were performed to study the removal mechanism of SiC at the nano scale. The effects of both cutting speed and undeformed cutting thickness on the material removal mechanism were considered. The ductile machining mechanism, cutting force, hydrostatic pressure, and tool wear was analyzed in depth. It was determined that the chip formation was dominated by the extrusion action rather than the shear theory during the nanocutting process. The performance and service life of the diamond tool can be effectively improved by properly increasing the cutting speed and reducing the undeformed cutting thickness. Additionally, the nanometric cutting at a higher cutting speed was able to improve the material removal rate but reduced the quality of machined surface and enlarged the subsurface damage of SiC. It is believed that the results can promote the level of ultraprecision machining technology. Full article
(This article belongs to the Topic Processing, Analysis, Modelling and Mechanics of Materials and Structures)
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<p>MD model of nanometric cutting on monocrystalline 3C-SiC.</p> Full article ">Figure 2
<p>Variations of the atomic displacement vectors according to (<b>a</b>) x− and (<b>b</b>) y−direction.</p> Full article ">Figure 3
<p>The displacement vectors of the workpiece atoms during nanometric cutting at a distance of (<b>a</b>) 4 nm and (<b>b</b>) 16 nm.</p> Full article ">Figure 4
<p>The lateral bulge and surface morphology of machined SiC at cutting speed of (<b>a</b>) 100, (<b>b</b>) 200, and (<b>c</b>) 400 m/s.</p> Full article ">Figure 5
<p>The effect of cutting speed on the subsurface damage at different cutting speed of (<b>a</b>) 100, (<b>b</b>) 200, and (<b>c</b>) 400 m/s.</p> Full article ">Figure 6
<p>The variations of the subsurface damage with different undeformed cutting thicknesses.</p> Full article ">Figure 7
<p>The analysis results of cutting forces at different cutting speed. (<b>a</b>) Cutting force; (<b>b</b>) Normal force; (<b>c</b>) Tangential force.</p> Full article ">Figure 8
<p>The variations of (<b>a</b>) normal force Fz and (<b>b</b>) tangential force Fx with different undeformed cutting thicknesses.</p> Full article ">Figure 9
<p>The effects of (<b>a</b>) cutting speed and (<b>b</b>) undeformed cutting thickness on the hydrostatic pressure during nanometric cutting.</p> Full article ">Figure 10
<p>The effect of cutting speed on the temperature distribution of the diamond tool. The cutting speed was (<b>a</b>) 100 m/s, (<b>b</b>) 200 m/s and (<b>c</b>) 400 m/s, respectively.</p> Full article ">Figure 11
<p>The analysis results of the tool wear at different cutting speed. Displacement offset along (<b>a</b>) x and (<b>b</b>) y direction; (<b>c</b>) Number of amorphous damage atoms; (<b>d</b>) Average number of amorphous damage atoms.</p> Full article ">Figure 12
<p>The variations of number of amorphous damage atoms with different undeformed cutting thicknesses.</p> Full article ">
10 pages, 2843 KiB  
Article
Fabrication and Characterization of Submicron-Scale Bovine Hydroxyapatite: A Top-Down Approach for a Natural Biomaterial
by Maria Apriliani Gani, Aniek Setiya Budiatin, Maria Lucia Ardhani Dwi Lestari, Fedik Abdul Rantam, Chrismawan Ardianto and Junaidi Khotib
Materials 2022, 15(6), 2324; https://doi.org/10.3390/ma15062324 - 21 Mar 2022
Cited by 8 | Viewed by 2694
Abstract
Submicron hydroxyapatite has been reported to have beneficial effects in bone tissue engineering. This study aimed to fabricate submicron-scale bovine hydroxyapatite (BHA) using the high-energy dry ball milling method. Bovine cortical bone was pretreated and calcined to produce BHA powder scaled in microns. [...] Read more.
Submicron hydroxyapatite has been reported to have beneficial effects in bone tissue engineering. This study aimed to fabricate submicron-scale bovine hydroxyapatite (BHA) using the high-energy dry ball milling method. Bovine cortical bone was pretreated and calcined to produce BHA powder scaled in microns. BHA was used to fabricate submicron BHA with milling treatment for 3, 6, and 9 h and was characterized by using dynamic light scattering, scanning electron microscope connected with energy dispersive X-Ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffractometry to obtain its particle size, calcium-to-phosphorus (Ca/P) ratio, functional chemical group, and XRD peaks and crystallinity. Results showed that the particle size of BHA had a wide distribution range, with peaks from ~5 to ~10 µm. Milling treatment for 3, 6, and 9 h successfully gradually reduced the particle size of BHA to a submicron scale. The milled BHA’s hydrodynamic size was significantly smaller compared to unmilled BHA. Milling treatment reduced the crystallinity of BHA. However, the treatment did not affect other characteristics; unmilled and milled BHA was shaped hexagonally, had carbonate and phosphate substitution groups, and the Ca/P ratio ranged from 1.48 to 1.68. In conclusion, the fabrication of submicron-scale BHA was successfully conducted using a high-energy dry ball milling method. The milling treatment did not affect the natural characteristics of BHA. Thus, the submicron-scale BHA may be potentially useful as a biomaterial for bone grafts. Full article
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Graphical abstract
Full article ">Figure 1
<p>Relative compressive strength of BHA and HA. Each bar shows the mean ± <span class="html-italic">SD</span> ratio. * <span class="html-italic">p</span> &lt; 0.05 based on the unpaired <span class="html-italic">t</span>-test.</p> Full article ">Figure 2
<p>SEM images and particle size distribution of unmilled BHA (<b>A</b>–<b>D</b>), BHA milled for 3 h (<b>E</b>–<b>H</b>), BHA milled for 6 h (<b>I</b>–<b>L</b>), and BHA milled for 9 h (<b>M</b>–<b>P</b>). (<b>A</b>,<b>E</b>,<b>I</b>,<b>M</b>) Images show total magnification of 1000×. (<b>B</b>,<b>F</b>,<b>J</b>,<b>N</b>) Images show total magnification of 5000×. (<b>C</b>,<b>G</b>,<b>K</b>,<b>O</b>) Images show total magnification of 15,000×. (<b>D</b>,<b>H</b>,<b>L</b>,<b>P</b>) Graphs show the corresponding particle size distributions.</p> Full article ">Figure 3
<p>FTIR spectra of unmilled and milled BHA.</p> Full article ">Figure 4
<p>XRD spectra of unmilled and milled BHA.</p> Full article ">Figure 5
<p>The hydrodynamic particle size of milled and unmilled BHA. Each bar shows the mean ± <span class="html-italic">SD</span> value. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01 based on a one-way ANOVA test.</p> Full article ">
15 pages, 2741 KiB  
Article
Suitability of Constitutive Models of the Structural Concrete Codes When Applied to Polyolefin Fibre Reinforced Concrete
by Alejandro Enfedaque, Fernando Suárez, Marcos G. Alberti and Jaime C. Gálvez
Materials 2022, 15(6), 2323; https://doi.org/10.3390/ma15062323 - 21 Mar 2022
Cited by 2 | Viewed by 1699
Abstract
The use of fibres as structural reinforcement in concrete is included in standards, providing guidelines to reproduce their behaviour, which have been proven adequate when steel fibres are used. Nevertheless, in recent years new materials, such as polyolefin fibres, have undergone significant development [...] Read more.
The use of fibres as structural reinforcement in concrete is included in standards, providing guidelines to reproduce their behaviour, which have been proven adequate when steel fibres are used. Nevertheless, in recent years new materials, such as polyolefin fibres, have undergone significant development as concrete reinforcement. This work gives insight on how suitable the constitutive models proposed by the Model Code 2010 (MC2010) are in the case of such polymer fibres. A set of numerical models has been carried out to reproduce the material behaviour proposed by the MC2010 and the approach based on the softening function proposed by the authors. The results show remarkable differences between the experimental results and the numerical simulations when the constitutive models described in the MC2010 are employed for different polyolefin fibre reinforced concrete mixes, while the material behaviour can be reproduced with greater accuracy if the softening function proposed by the authors is employed when this type of macro-polymer fibres is used. Moreover, the relatively complex behaviour of polyolefin fibre reinforced concrete may be reproduced by using such constitutive model. Full article
(This article belongs to the Special Issue Fracture Mechanics of Fiber Reinforced Concrete)
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<p>Possible crack paths (<b>left</b>) and geometrical definitions of <math display="inline"><semantics> <mstyle mathvariant="bold" mathsize="normal"> <mi>w</mi> </mstyle> </semantics></math>, <math display="inline"><semantics> <mstyle mathvariant="bold" mathsize="normal"> <mi>n</mi> </mstyle> </semantics></math> and <math display="inline"><semantics> <mrow> <msup> <mstyle mathvariant="bold" mathsize="normal"> <mi>b</mi> </mstyle> <mo>+</mo> </msup> </mrow> </semantics></math> (<b>right</b>).</p> Full article ">Figure 2
<p>(<b>a</b>) Typical load F-CMOD curve for FRC and (<b>b</b>) geometry of a three-point bending test specimen.</p> Full article ">Figure 3
<p>Rigid-plastic model (<b>left</b>) and linear model (<b>right</b>) as described by the MC2010.</p> Full article ">Figure 4
<p>Trilinear diagram proposed by the authors for PFRC.</p> Full article ">Figure 5
<p>Comparison of the constitutive models obtained by each approach for different fibre dosages: (<b>a</b>) 3 kg/m<sup>3</sup>, (<b>b</b>) 4.5 kg/m<sup>3</sup>, (<b>c</b>) 6 kg/m<sup>3</sup>, (<b>d</b>) 10 kg/m<sup>3</sup>.</p> Full article ">Figure 6
<p>(<b>a</b>) Mesh refined along the crack path and boundary conditions, (<b>b</b>) maximum principal stress field in the damaged region of the model that used the linear constitutive law for 6 kg/m<sup>3</sup> fibre dosage with no crack tracking. Convergence is not reached.</p> Full article ">Figure 7
<p>Comparison of the load-deflection diagram obtained with each approach for different fibre dosages: (<b>a</b>) rigid-plastic model, (<b>b</b>) linear elastic model (unlimited development), (<b>c</b>) linear elastic model (limited development), (<b>d</b>) trilinear model.</p> Full article ">Figure 8
<p>Comparison among the experimental curves and the simulations results obtained with the constitutive models implemented.</p> Full article ">Figure 9
<p>Comparison of the loads borne by the simulations at certain deflection values with respect to the experimental values.</p> Full article ">
14 pages, 3761 KiB  
Article
Radiation-Induced Sharpening in Cr-Coated Zirconium Alloy
by Joël Ribis, Alexia Wu, Raphaëlle Guillou, Jean-Christophe Brachet, Cédric Baumier, Aurélie Gentils and Marie Loyer-Prost
Materials 2022, 15(6), 2322; https://doi.org/10.3390/ma15062322 - 21 Mar 2022
Cited by 8 | Viewed by 2529
Abstract
To improve the safety of nuclear power plants, a Cr protective layer is deposited on zirconium alloys to enhance oxidation resistance of the nuclear fuel cladding during both in-service and hypothetical accidental transients at High Temperature (HT) in Light Water Reactors. The formation [...] Read more.
To improve the safety of nuclear power plants, a Cr protective layer is deposited on zirconium alloys to enhance oxidation resistance of the nuclear fuel cladding during both in-service and hypothetical accidental transients at High Temperature (HT) in Light Water Reactors. The formation of the Cr2O3 film on the coating surface considerably helps in reducing the oxidation kinetics of the zirconium alloy, especially during hypothetic Loss of Coolant Accident (LOCA). However, if the Cr coating is successful to increase the oxidation resistance at HT of the zirconium substrate, for in-service conditions, under neutron irradiation, Cr desquamation has to be avoided to guarantee a safe use of the Cr-coated zirconium alloys. Therefore, the adhesion properties have to be maintained despite the structural defects created by sustained neutron irradiation in the reactor environment. This paper proposes to study the behavior of the Zircaloy-Cr interface of a first generation Cr-coated material during a specific in situ ion irradiation. As deposited, the Cr-coated sample presents a f.c.c. C15 Laves-type intermetallic phase at the interface with off-stoichiometric composition. After irradiation and for the specific conditions applied, this interfacial phase has significantly dissolved. Energy Dispersion Spectroscopy revealed that the dissolution was accompanied by a counterintuitive “sharpening” effect. Full article
(This article belongs to the Special Issue Advances in Radiation-Induced Nanostructuration of Materials)
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<p>Depth profile of displacement damage under gold ion irradiation in: (<b>a</b>) in situ irradiation condition, (<b>b</b>) ex situ irradiation condition.</p> Full article ">Figure 2
<p>TEM images of the Cr-coated zircaloy-4: (<b>a</b>) bright-field TEM showing both the Zr and Cr regions, (<b>b</b>) energy-filtered jump ratio images obtained at the Zr M and Cr M edges.</p> Full article ">Figure 3
<p>EDS analyses of the interface region: (<b>a</b>) STEM-ADF image, (<b>b</b>) EDS map obtained after collection of X-rays generated by emission from the energy-level shell Zr L, (<b>c</b>) EDS map obtained after collection of X-rays generated by emission from the energy-level shell Cr K, (<b>d</b>) Zr-Cr composition profile extracted from region labeled 1, (<b>e</b>) Zr-Cr composition profile extracted from region labeled 2, (<b>f</b>) Zr-Cr composition profile extracted from region labeled 3.</p> Full article ">Figure 4
<p>High-resolution TEM of the interface region: (<b>a</b>) bright-field TEM of the interface phase, (<b>b</b>) high-resolution image of the interface phase with corresponding Fast Fourier Transform (F.F.T.).</p> Full article ">Figure 5
<p>The interface region before and after irradiation: (<b>a</b>) bright field TEM image of the Zr-Cr interface, (<b>b</b>) same area after ion-irradiation, (<b>c</b>) detailed view of the interface corresponding to the white rectangle labeled 1 in (<b>a</b>), (<b>d</b>) detailed view of the interface after irradiation corresponding to the white rectangle labeled 2 in (<b>b</b>).</p> Full article ">Figure 6
<p>Concentration profile of Zr and Cr atoms across the interface: (<b>a</b>) before and after in situ irradiation (interface sharpening), (<b>b</b>) before and after ex situ irradiation (interface broadening).</p> Full article ">Figure 7
<p>Average strains for Cr layer versus sin<sup>2</sup>Ψ curves for unirradiated (black boxes) and irradiated (orange circles) samples. Dotted lines symbolize the linear regression for the sin<sup>2</sup>Ψ method.</p> Full article ">Figure 8
<p>Schematic representation of the sharpening effect caused by asymmetry of the diffusion coefficient.</p> Full article ">
20 pages, 10139 KiB  
Article
Production and Characterization of the Third-Generation Oxide Nanotubes on Ti-13Zr-13Nb Alloy
by Bożena Łosiewicz, Sandra Skwarek, Agnieszka Stróż, Patrycja Osak, Karolina Dudek, Julian Kubisztal and Joanna Maszybrocka
Materials 2022, 15(6), 2321; https://doi.org/10.3390/ma15062321 - 21 Mar 2022
Cited by 8 | Viewed by 2251
Abstract
In the group of vanadium-free titanium alloys used for applications for long-term implants, the Ti-13Zr-13Nb alloy has recently been proposed. The production of a porous layer of oxide nanotubes (ONTs) with a wide range of geometries and lengths on the Ti-13Zr-13Nb alloy surface [...] Read more.
In the group of vanadium-free titanium alloys used for applications for long-term implants, the Ti-13Zr-13Nb alloy has recently been proposed. The production of a porous layer of oxide nanotubes (ONTs) with a wide range of geometries and lengths on the Ti-13Zr-13Nb alloy surface can increase its osteoinductive properties and enable intelligent drug delivery. This work concerns developing a method of electrochemical modification of the Ti-13Zr-13Nb alloy surface to obtain third-generation ONTs. The effect of the anodizing voltage on the microstructure and thickness of the obtained oxide layers was conducted in 1 M C2H6O2 + 4 wt% NH4F electrolyte in the voltage range 5–35 V for 120 min at room temperature. The obtained third-generation ONTs were characterized using SEM, EDS, SKP, and 2D roughness profiles methods. The preliminary assessment of corrosion resistance carried out in accelerated corrosion tests in the artificial atmosphere showed the high quality of the newly developed ONTs and the slight influence of neutral salt spray on their micromechanical properties. Full article
(This article belongs to the Special Issue Corrosion and Corrosion Inhibition of Metals and Their Alloys)
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<p>The HKS 400 salt spray chamber during the NSS test according to ISO 9227:2017 [<a href="#B44-materials-15-02321" class="html-bibr">44</a>]: (<b>a</b>) Arrangement of collecting devices in the salt chamber; (<b>b</b>) Method of mounting the test samples in the holder (<b>c</b>).</p> Full article ">Figure 2
<p>Current transients for the Ti-13Zr-13Nb electrode in 1 M C<sub>2</sub>H<sub>6</sub>O<sub>2</sub> + 4 wt% NH<sub>4</sub>F electrolyte during anodizing for: (<b>a</b>) 7200 s; (<b>b</b>) first 80 s.</p> Full article ">Figure 3
<p>SEM image of the microstructure of the Ti-13Zr-13Nb alloy before and after anodizing in 1 M C<sub>2</sub>H<sub>6</sub>O<sub>2</sub> + 4 wt% NH<sub>4</sub>F electrolyte: (<b>a</b>) Etched; (<b>b</b>) Anodized at 5 V for 120 min; (<b>c</b>) Anodized at 10 V for 120 min.</p> Full article ">Figure 4
<p>SEM image of the microstructure of SWNTs layer formed on the Ti-13Zr-13Nb alloy in 1 M C<sub>2</sub>H<sub>6</sub>O<sub>2</sub> + 4 wt% NH<sub>4</sub>F electrolyte under anodizing conditions: (<b>a</b>) 15 V for 120 min; (<b>b</b>) 20 V for 120 min; (<b>c</b>) 25 V for 120 min; (<b>d</b>) 30 V for 120 min; (<b>e</b>) 35 V for 120 min.</p> Full article ">Figure 5
<p>The oxide nanotube diameter on the Ti-13Zr-13Nb alloy surface as a function of anodizing voltage (U) for 120 min in 1 M C<sub>2</sub>H<sub>6</sub>O<sub>2</sub> + 4 wt% NH<sub>4</sub>F electrolyte: (<b>a</b>) Outer diameter (D<sub>outer</sub>); (<b>b</b>) Inner diameter (D<sub>i</sub>).</p> Full article ">Figure 6
<p>The thickness (L) of the oxide layer on the Ti-13Zr-13Nb alloy surface obtained by anodizing in 1 M C<sub>2</sub>H<sub>6</sub>O<sub>2</sub> + 4 wt% NH<sub>4</sub>F electrolyte at 5–35 V for 120 min, measured over distance x.</p> Full article ">Figure 7
<p>The total surface area (A<sub>total</sub>) of SWNTs on the Ti-13Zr-13Nb alloy surface obtained by anodizing in 1 M C<sub>2</sub>H<sub>6</sub>O<sub>2</sub> + 4 wt% NH<sub>4</sub>F electrolyte at U of 15–35 V for 120 min.</p> Full article ">Figure 8
<p>EDS spectrum for the Ti-13Zr-13Nb alloy surface: (<b>a</b>) Before anodizing; (<b>b</b>) After anodizing at 35 V for 120 min.</p> Full article ">Figure 9
<p>The contact potential difference (CPD) map for the Ti-13Zr-13Nb alloy surface: (<b>a</b>) Before anodizing; (<b>b</b>) After anodizing at 15 V for 120 min; (<b>c</b>) After anodizing at 25 V for 120 min; (<b>d</b>) After anodizing at 35 V for 120 min.</p> Full article ">Figure 10
<p>The arithmetic mean (CPD<sub>av</sub>) and root mean square of height irregularities (CPD<sub>rms</sub>) for the Ti-13Zr-13Nb alloy surface before and after anodizing.</p> Full article ">Figure 11
<p>Roughness profile for the Ti-13Zr-13Nb alloy surface before and after anodizing at 15–35 V.</p> Full article ">Figure 12
<p>Basic surface texture parameters for the Ti-13Zr-13Nb alloy surface before and after anodizing: (<b>a</b>) Ra; (<b>b</b>) Rz; (<b>c</b>) Rp; (<b>d</b>) Rv.</p> Full article ">Figure 13
<p>The Ti-13Zr-13Nb alloy surface before and after NSS test according to ISO 9227:2017 [<a href="#B44-materials-15-02321" class="html-bibr">44</a>]: (<b>a</b>) Non-anodized substrate; (<b>b</b>) After anodizing at 15 V for 120 min; (<b>c</b>) After anodizing at 25 V for 120 min; (<b>d</b>) After anodizing at 35 V for 120 min.</p> Full article ">Figure 14
<p>Microhardness of the Ti-13Zr-13Nb alloy surface before and after the NSS test according to ISO 9227:2017 [<a href="#B44-materials-15-02321" class="html-bibr">44</a>] for non-anodized substrate (U = 0 V) and after anodizing at U of 5–35 V for 120 min.</p> Full article ">
15 pages, 5134 KiB  
Article
Investigating Optimum Conditions for Developing Pozzolanic Ashes from Organic Wastes as Cement Replacing Materials
by Suhail Zaffar, Aneel Kumar, Naeem Aziz Memon, Rabinder Kumar and Abdullah Saand
Materials 2022, 15(6), 2320; https://doi.org/10.3390/ma15062320 - 21 Mar 2022
Cited by 5 | Viewed by 2614
Abstract
This research was performed to investigate the optimum conditions for developing pozzolanic ashes from organic wastes to be used as cement replacement materials. The organic wastes explored in the research are rice husk ash (RHA), wheat straw ash (WSA), and cow dung (CDA). [...] Read more.
This research was performed to investigate the optimum conditions for developing pozzolanic ashes from organic wastes to be used as cement replacement materials. The organic wastes explored in the research are rice husk ash (RHA), wheat straw ash (WSA), and cow dung (CDA). When the organic waste is turned into ash, it develops a pozzolanic character due to the presence of silica. However, the presence of reactive silica and its pozzolanic reactivity depends on the calcination temperature, duration, and grinding. In this research, the organic wastes were calcined at three different calcination temperatures (300 °C, 400 °C, and 800 °C) for 2, 4, 6, and 8 h duration. The obtained ashes were ground for 30 min and replaced by 20% with cement. The samples containing ashes were tested for compressive strength, X-ray diffractometry (XRD), weight loss, and strength activity index (SAI). It was observed that the RHA calcinated at 600 °C for 2 h showed better strength. However, in the case of WSA and CDA, the most favorable calcination condition in terms of strength development was obtained at 600 °C for 6 h duration. The highest SAI was achieved for the mortar samples containing CDA calcinated at 600 °C for 6 h duration (CDA600-6H). The other two ashes (RHA and WSA) did not qualify as pozzolan according to the ASTM C618 classification. This was due to the presence of silica in crystalline form and lower surface area of the ash material. In this research, the ash was ground only for 30 min after calcination which did not contribute to an increase in the specific surface area and thus the pozzolanic activity. The materials ground for the higher duration are recommended for higher SAI. Full article
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<p>XRD pattern of rice RHA calcinated at (<b>a</b>) 300 °C (<b>b</b>) 600 °C and (<b>c</b>) 800 °C.</p> Full article ">Figure 2
<p>XRD pattern of rice WSA calcinated at (<b>a</b>) 300 °C (<b>b</b>) 600 °C and (<b>c</b>) 800 °C.</p> Full article ">Figure 3
<p>XRD pattern of rice CDA calcinated at (<b>a</b>) 300 °C (<b>b</b>) 600 °C and (<b>c</b>) 800 °C.</p> Full article ">Figure 4
<p>Compressive Strength behavior of RHA-cement mortar at different calcination temperatures.</p> Full article ">Figure 5
<p>Compressive Strength behavior of WSA-cement mortar at different calcination temperatures.</p> Full article ">Figure 6
<p>Compressive Strength behavior of CDA-cement mortar at different calcination temperatures.</p> Full article ">Figure 7
<p>SAI of RHA, WSA, and CDA samples at different incineration temperatures.</p> Full article ">Figure 8
<p>Weight loss of RHA, WSA, and CDA samples at different incineration temperatures.</p> Full article ">
20 pages, 6100 KiB  
Article
Combinatorial Study of Phase Composition, Microstructure and Mechanical Behavior of Co-Cr-Fe-Ni Nanocrystalline Film Processed by Multiple-Beam-Sputtering Physical Vapor Deposition
by Péter Nagy, Nadia Rohbeck, Remo N. Widmer, Zoltán Hegedűs, Johann Michler, László Pethö, János L. Lábár and Jenő Gubicza
Materials 2022, 15(6), 2319; https://doi.org/10.3390/ma15062319 - 21 Mar 2022
Cited by 7 | Viewed by 2546
Abstract
A combinatorial Co-Cr-Fe-Ni compositional complex alloy (CCA) thin film disk with a thickness of 1 µm and a diameter of 10 cm was processed by multiple-beam-sputtering physical vapor deposition (PVD) using four pure metal sources. The chemical composition of the four constituent elements [...] Read more.
A combinatorial Co-Cr-Fe-Ni compositional complex alloy (CCA) thin film disk with a thickness of 1 µm and a diameter of 10 cm was processed by multiple-beam-sputtering physical vapor deposition (PVD) using four pure metal sources. The chemical composition of the four constituent elements varied between 4 and 64 at.% in the film, depending on the distance from the four PVD sources. The crystal structure, the crystallite size, the density of lattice defects (e.g., dislocations and twin faults) and the crystallographic texture were studied as a function of the chemical composition. It was found that in a wide range of elemental concentrations a face-centered cubic (fcc) structure with {111} crystallographic texture formed during PVD. Considering the equilibrium phase diagrams, it can be concluded that mostly the phase composition of the PVD layer is far from the equilibrium. Body-centered cubic (bcc) and hexagonal-close packed (hcp) structures formed only in the parts of the film close to Co-Fe and Co-Cr sources, respectively. A nanocrystalline microstructure with the grain size of 10–20 nm was developed in the whole layer, irrespective of the chemical composition. Transmission electron microscopy indicated a columnar growth of the film during PVD. The density of as-grown dislocations and twin faults was very high, as obtained by synchrotron X-ray diffraction peak profile analysis. The nanohardness and the elastic modulus were determined by indentation for the different chemical compositions on the combinatorial PVD film. This study is the continuation of a former research published recently in Nagy et al., Materials 14 (2021) 3357. In the previous work, only the fcc part of the sample was investigated. In the present paper, the study was extended to the bcc, hcp and multiphase regions. Full article
(This article belongs to the Special Issue Advances in Structure Analysis of Amorphous and Nanocrystalline Materials)
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<p>The phase map of the Co-Cr-Fe-Ni CCA sample.</p> Full article ">Figure 2
<p>The points on the Co-Cr-Fe-Ni thin film surface investigated in this study (numbered from 1 to 19). The approximate positions of Cr, Ni, Co and Fe sputtering sources are also shown. The masked parts of the Si substrate, indicated by dark grey color, were not covered by CCA film. The areas indicate due to the masking effect of the sample holder. The points investigated in our previous work [<a href="#B21-materials-15-02319" class="html-bibr">21</a>] are marked by black squares while the additional locations studied in this paper are indicated by green circles.</p> Full article ">Figure 3
<p>The XRF maps of the 4 initial elements. The dotted line represents the contour of the wafer.</p> Full article ">Figure 4
<p>X-ray diffractograms for points Nos. 17 (<b>a</b>), 16 (<b>b</b>), 14 (<b>c</b>) and 15 (<b>d</b>). K = 2sinθ/λ, where θ is the Bragg angle, and λ is the wavelength of X-rays.</p> Full article ">Figure 5
<p>Evaluation of the first five XRD peaks of the bcc phase at points Nos. 15 (<b>a</b>) and 14 (<b>b</b>) applying CMWP fitting procedure. The peaks of the fcc phase were put into the background during the CMWP fitting.</p> Full article ">Figure 6
<p>The parameters of the microstructure determined by XLPA for different locations on the Co-Cr-Ni-Fe film.</p> Full article ">Figure 7
<p>(<b>a</b>) Bright-field and (<b>b</b>) dark-field TEM images taken on the cross-section of the film at point No. 3. (<b>c</b>) A magnified region from figure (<b>b</b>) indicated by the dashed square, showing the fragmentation of a column into grains. (<b>d</b>) HAADF image and (<b>e</b>–<b>h</b>) the corresponding element maps for the four constituents.</p> Full article ">Figure 8
<p>(<b>a</b>) Bright-field and (<b>b</b>) dark-field TEM images on the cross-section of the film at point No. 14 where dual phase fcc/bcc structure formed. (<b>c</b>) HAADF image and (<b>d</b>) the corresponding phase map obtained by diffraction in STEM. The green and blue regions represent the fcc and bcc phases, respectively, while in the grey areas the phase identification was uncertain. (<b>e</b>–<b>h</b>) Element maps for the four constituents in the region corresponding to figure (<b>c</b>,<b>d</b>).</p> Full article ">Figure 9
<p>(<b>a</b>) Dark-field TEM image of the film cross-section at point No. 15. (<b>b</b>) HAADF image and (<b>c</b>–<b>f</b>) the corresponding element maps for the four constituents.</p> Full article ">Figure 10
<p>The 111 pole figures determined by XRD for the fcc phase in the different points of the Co-Cr-Ni-Fe film. The blank squares indicate locations where the structure was different from fcc.</p> Full article ">Figure 11
<p>The 100 and 101 pole figures measured by XRD for the major hcp phase at location No. 9. The 110 and 200 XRD pole figures characterizing the texture for the bcc phase at point No. 15.</p> Full article ">Figure 12
<p>The distribution of the hardness (<b>a</b>) and the elastic modulus (<b>b</b>) for the Co-Cr-Ni-Fe thin film as determined by nanoindentation.</p> Full article ">
13 pages, 4656 KiB  
Article
Athermal ω Phase and Lattice Modulation in Binary Zr-Nb Alloys
by Mitsuharu Todai, Keisuke Fukunaga and Takayoshi Nakano
Materials 2022, 15(6), 2318; https://doi.org/10.3390/ma15062318 - 21 Mar 2022
Cited by 1 | Viewed by 2373
Abstract
To further explore the potential of Zr-based alloys as a biomaterial that will not interfere with magnetic resonance imaging (MRI), the microstructural characteristics of Zr-xat.% Nb alloys (10 ≤ x ≤ 18), particularly the athermal ω phase and lattice modulation, were investigated by [...] Read more.
To further explore the potential of Zr-based alloys as a biomaterial that will not interfere with magnetic resonance imaging (MRI), the microstructural characteristics of Zr-xat.% Nb alloys (10 ≤ x ≤ 18), particularly the athermal ω phase and lattice modulation, were investigated by conducting electrical resistivity and magnetic susceptibility measurements and transmission electron microscopy observations. The 10 Nb alloy and 12 Nb alloys had a positive temperature coefficient of electrical resistivity. The athermal ω phase existed in 10 Nb and 12 Nb alloys at room temperature. Alternatively, the 14 Nb and 18 Nb alloys had an anomalous negative temperature coefficient of the resistivity. The selected area diffraction pattern of the 14 Nb alloy revealed the co-occurrence of ω phase diffraction and diffuse satellites. These diffuse satellites were represented by gβ + q when the zone axis was [001] or [113], but not [110]. These results imply that these diffuse satellites appeared because the transverse waves consistent with the propagation and displacement vectors were q = <ζ ζ¯ 0>* for the ζ~1/2 and <110> directions. It is possible that the resistivity anomaly was caused by the formation of the athermal ω phase and transverse wave. Moreover, control of the athermal ω-phase transformation and occurrence of lattice modulation led to reduced magnetic susceptibility, superior deformation properties, and a low Young’s modulus in the Zr-Nb alloys. Thus, Zr-Nb alloys are promising MRI-compatible metallic biomaterials. Full article
(This article belongs to the Special Issue Advanced Materials for Societal Implementation)
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<p>Electrical resistivity of various Zr-x at.% Nb alloys (x = 10, 12, 14, and 18) during the cooling process: (<b>a</b>–<b>d</b>) x = 10, 12, 14, and 18, respectively.</p> Full article ">Figure 2
<p>Nb content dependence of the superconductive transition temperature (<span class="html-italic">T</span><sub>c</sub>) of Zr-x at.% Nb (10 ≤ x ≤ 18) alloys.</p> Full article ">Figure 3
<p>Results for Zr-x at.% Nb alloys (10 ≤ x ≤ 18), as obtained by applying the incident beam in the [113] direction at room temperature: (<b>a</b>–<b>d</b>) diffraction patterns for x = 10, 12, 14, and 18, respectively; (<b>a’</b>–<b>d’</b>) corresponding intensity profiles.</p> Full article ">Figure 4
<p>HV variation of the Zr-x at.% Nb alloys.</p> Full article ">Figure 5
<p>Dark-field images of Zr-14 at.% Nb alloy were observed by a circle in diffraction patterns in (<b>a</b>,<b>b</b>), respectively.</p> Full article ">Figure 6
<p>SADPs of the Zr-14 at.% Nb alloy: (<b>a</b>) SADP showing the zone axis of [001]; (<b>b</b>) SADP showing the systematic condition; (<b>a’</b>,<b>b’</b>) corresponding intensity profiles for the respective areas enclosed in the dotted boxes.</p> Full article ">Figure 7
<p>(<b>a</b>) SADP of the Zr-14 at.% Nb alloy (zone axis of [110]); (<b>b</b>) intensity profile along [1<span class="html-overline">1</span>0].</p> Full article ">Figure 8
<p>Diffraction patterns of Zr-18 at.%Nb alloy. The zone axis is [001] in (<b>a</b>) and [110] in (<b>b</b>).</p> Full article ">Figure 9
<p>Temperature dependence of diffraction patterns of Zr-18 at.%Nb alloy: (<b>a</b>) taken at 90 K and (<b>b</b>) taken at 230 K.</p> Full article ">Figure 10
<p>Magnetic susceptibilities of several alloys at room temperature [<a href="#B8-materials-15-02318" class="html-bibr">8</a>].</p> Full article ">Figure 11
<p>Electrical resistivity (<b>a</b>) and magnetic susceptibility (<b>b</b>) of the Zr-18 at.% Nb alloy.</p> Full article ">
13 pages, 5148 KiB  
Article
Peri-Implant Repair Using a Modified Implant Macrogeometry in Diabetic Rats: Biomechanical and Molecular Analyses of Bone-Related Markers
by Hugo Robertson Sant’Anna, Marcio Zaffalon Casati, Mounir Colares Mussi, Fabiano Ribeiro Cirano, Suzana Peres Pimentel, Fernanda Vieira Ribeiro and Mônica Grazieli Corrêa
Materials 2022, 15(6), 2317; https://doi.org/10.3390/ma15062317 - 21 Mar 2022
Cited by 1 | Viewed by 2068
Abstract
DM has a high prevalence worldwide and exerts a negative influence on bone repair around dental implants. Modifications of the microgeometry of implants have been related to positive results in bone repair. This study assessed, for the first time, the influence of an [...] Read more.
DM has a high prevalence worldwide and exerts a negative influence on bone repair around dental implants. Modifications of the microgeometry of implants have been related to positive results in bone repair. This study assessed, for the first time, the influence of an implant with modified macrodesign based on the presence of a healing chamber in the pattern of peri-implant repair under diabetic conditions. Thirty Wistar rats were assigned to receive one titanium implant in each tibia (Control Implant (conventional macrogeometry) or Test Implant (modified macrogeometry)) according to the following groups: Non-DM + Control Implant; Non-DM + Test Implant; DM + Control Implant; DM + Test Implant. One month from the surgeries, the implants were removed for counter-torque, and the bone tissue surrounding the implants was stored for the mRNA quantification of bone-related markers. Implants located on DM animals presented lower counter-torque values in comparison with Non-DM ones, independently of macrodesign (p < 0.05). Besides, higher biomechanical retention levels were observed in implants with modified macrogeometry than in the controls in both Non-DM and DM groups (p < 0.05). Moreover, the modified macrogeometry upregulated OPN mRNA in comparison with the control group in Non-DM and DM rats (p < 0.05). Peri-implant bone repair may profit from the use of implants with modified macrogeometry in the presence of diabetes mellitus, as they offer higher biomechanical retention and positive modulation of important bone markers in peri-implant bone tissue. Full article
(This article belongs to the Special Issue Dental Implant Biomaterials: In Vitro and In Vivo Simulations and Applications)
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<p>(<b>a</b>) Surgical exposition of the bone surface of the tibiae by rhombus dissection. (<b>b</b>) Bicortically prepared implant bed and placement of titanium implant into the tibia. (<b>c</b>) Implant was completely inserted when all screw threads had fixed into the bone cortex.</p> Full article ">Figure 2
<p>(<b>A</b>,<b>B</b>) Stereo microscopy of the implants (3×) for control and test groups, respectively. (<b>C</b>,<b>D</b>) Scanning electron microscopy of the implants (80–100×) for control and test groups, respectively.</p> Full article ">Figure 3
<p>* indicates intra-group statistical differences (Split-Plot Analysis of Variance; <span class="html-italic">p</span> &lt; 0.05). ǂ indicates inter-group statistical differences (Split-Plot Analysis of Variance; <span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 4
<p>ǂ indicates intra-group statistical differences (Wilcoxon Signed-rank Test; <span class="html-italic">p</span> &lt; 0.05). * indicates inter-group statistical differences (Mann–Whitney U Test; <span class="html-italic">p</span> &lt; 0.05). Relative levels of mRNA for: (<b>A</b>)—RUNX/GAPDH; (<b>B</b>)—BMP-2/GAPDH; (<b>C</b>)—β-CATENIN/GAPDH; (<b>D</b>)—OPN/GAPDH; (<b>E</b>)—OPG/GAPDH; (<b>F</b>)—DKK/GAPDH; (<b>G</b>)—RANKL/GAPDH; (<b>H</b>)—RANKL/OPG.</p> Full article ">
8 pages, 1482 KiB  
Article
Optimization of Digital Light Processing Three-Dimensional Printing of the Removable Partial Denture Frameworks; The Role of Build Angle and Support Structure Diameter
by Mostafa Omran Hussein and Lamis Ahmed Hussein
Materials 2022, 15(6), 2316; https://doi.org/10.3390/ma15062316 - 21 Mar 2022
Cited by 7 | Viewed by 3377
Abstract
The optimal three-dimensional (3D) printing parameters of removable partial denture (RPD) frameworks should be studied to achieve the best accuracy, printing time, and least materials consumed. This study aimed to find the best build angle and support structures’ diameter of the 3D printed [...] Read more.
The optimal three-dimensional (3D) printing parameters of removable partial denture (RPD) frameworks should be studied to achieve the best accuracy, printing time, and least materials consumed. This study aimed to find the best build angle and support structures’ diameter of the 3D printed (RPD) framework. Sixty (RPD) frameworks (10 in each group) were manufactured by digital light processing (DLP) 3D printing technology at three build angles (110-D, 135-D, and 150-D) and two support structures diameters (thick, L, and thin, S). Six groups were named according to their printing setting as (110-DS, 135-DS, 150-DS, 110-DL, 135-DL, and 150-DL). Frameworks were 3D scanned and compared to the original cast surface using 3D metrology software (Geomagic Control X; 3D Systems, Rock Hill, SC). Both printing time and material consumption were also recorded. Data were tested for the significant difference by one-way analysis of variance (ANOVA) test at (α = 0.05). The correlations between outcome parameters were also calculated. The 110-DL group showed the least accuracy. Significantly, the printing time of the 150-D groups had the lowest time. Material consumption of group 110-DS presented the lowest significantly statistical value. Printing time had a linear correlation with both accuracy and material consumption. Within the study limitations, the 150-degree build angle and thin diameter support structures showed optimal accuracy and time-saving regardless of material consumption. Full article
(This article belongs to the Section Biomaterials)
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<p>(<b>a</b>) Virtual waxing of the removable partial denture framework; (<b>b</b>) framework ready to export and three-dimensional printing.</p> Full article ">Figure 2
<p>Image representative to the 3D printed parts at different build angles and support thicknesses. The upper three parts for the thin support with 110, 135, and 150-degree angles (from right to left). The lower parts showing same sequence at thick support.</p> Full article ">Figure 3
<p>Sample of color maps of the three-dimensional deviations of different groups generated by the metrology software with a color-coded scale showing level of deviations. (<b>A</b>–<b>C</b>) represent 110, 135, and 150-degree angles with thin support structures. (<b>D</b>–<b>F</b>) represent same angle sequence but with thick support structures.</p> Full article ">
1 pages, 454 KiB  
Correction
Correction: Chen et al. The Effect of High-Quality RDX on the Safety and Mechanical Properties of Pressed PBX. Materials 2022, 15, 1185
by Shixiong Chen, Hua Qian, Bingxin Liu, Feiyang Xu, Jiuhou Rui and Dabin Liu
Materials 2022, 15(6), 2315; https://doi.org/10.3390/ma15062315 - 21 Mar 2022
Cited by 1 | Viewed by 1099
Abstract
Error in Figure [...] Full article
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<p>Apparent morphology images of different RDX crystals: (<b>a</b>) raw RDX (400×), (<b>b</b>) H-RDX (200×), (<b>c</b>) raw RDX (1500×), and (<b>d</b>) H-RDX (2000×).</p> Full article ">
16 pages, 1736 KiB  
Article
Fragment-Resistant Property Optimization within Ballistic Inserts Obtained on the Basis of Para-Aramid Materials
by Katarzyna Kośla, Paweł Kubiak, Marcin Łandwijt, Wioleta Urbaniak and Agnieszka Kucharska-Jastrząbek
Materials 2022, 15(6), 2314; https://doi.org/10.3390/ma15062314 - 21 Mar 2022
Cited by 5 | Viewed by 2443
Abstract
A high protection level without an excessive weight is a basic assumption in the design of modern armors and protection systems. Optimizing armors is a task of development of the utmost importance, and is the subject of the work contained within this article. [...] Read more.
A high protection level without an excessive weight is a basic assumption in the design of modern armors and protection systems. Optimizing armors is a task of development of the utmost importance, and is the subject of the work contained within this article. Optimization of ballistic inserts was carried out using multicriterial analysis (MCA), which enables the selection of the optimal composition, taking into account properties such as ballistic resistance, physicomechanical, and/or functional properties. For this purpose, various types of composite systems were produced and tested in terms of their fragment-resistant properties according to STANAG 2920 and the composite areal density of different ballistic inserts: Soft inserts made of Twaron® para-aramid sheets, hard ballistic inserts made of multilayer hot-pressed preimpregnated sheets, and hybrid hard ballistic inserts prepared on the basis of multilayer hot-pressed preimpregnated sheets and ceramics. The application of MCA and performance of experimental fragment resistance tests for a wide spectrum of para-aramid inserts are part of the novelty of this work. The obtained test results showed that depending on the composition of the composite system, we could obtain a wide range of fragmentation resistance in the range of 300 to >1800 m/s, which depended on the areal density and type of composite system used. The results also confirmed that MCA is a good computational tool to select the optimal design of para-aramid ballistic inserts. Full article
(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)
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Graphical abstract
Full article ">Figure 1
<p>Soft ballistic inserts made from Twaron<sup>®</sup> CT612 and Twaron<sup>®</sup> UD42 after FSP.22 fragment resistance tests.</p> Full article ">Figure 2
<p>Soft ballistic inserts after FSP.22 fragment resistance tests: made from Twaron<sup>®</sup> CT612 (<b>a</b>) and Twaron<sup>®</sup> UD42 (<b>b</b>).</p> Full article ">Figure 3
<p>V50 ballistic protection limit by areal density of the tested composite system obtained for composites type 1 and 2.</p> Full article ">Figure 4
<p>Hard ballistic inserts: Composite type 1—multilayer hot-pressed Twaron<sup>®</sup> CT736 preimpregnated sheets (shooting side) (<b>a</b>); composite type 1—visible delamination and para-aramid yarn breakage (outlet side of fragment) (<b>b</b>); composite type 2—multilayer hot-pressed Twaron<sup>®</sup> CT736 preimpregnated sheets and Al<sub>2</sub>O<sub>3</sub> (shooting side) (<b>c</b>); composite type 2—ceramic elements cracked as a result of the impact of the FSP.22 fragment (<b>d</b>).</p> Full article ">
18 pages, 3766 KiB  
Article
Hydrophobic Recovery of PDMS Surfaces in Contact with Hydrophilic Entities: Relevance to Biomedical Devices
by Tomoo Tsuzuki, Karine Baassiri, Zahra Mahmoudi, Ayyappasamy Sudalaiyadum Perumal, Kavya Rajendran, Gala Montiel Rubies and Dan V. Nicolau
Materials 2022, 15(6), 2313; https://doi.org/10.3390/ma15062313 - 21 Mar 2022
Cited by 19 | Viewed by 4861
Abstract
Polydimethylsiloxane (PDMS), a silicone elastomer, is increasingly being used in health and biomedical fields due to its excellent optical and mechanical properties. Its biocompatibility and resistance to biodegradation led to various applications (e.g., lung on a chip replicating blood flow, medical interventions, and [...] Read more.
Polydimethylsiloxane (PDMS), a silicone elastomer, is increasingly being used in health and biomedical fields due to its excellent optical and mechanical properties. Its biocompatibility and resistance to biodegradation led to various applications (e.g., lung on a chip replicating blood flow, medical interventions, and diagnostics). The many advantages of PDMS are, however, partially offset by its inherent hydrophobicity, which makes it unsuitable for applications needing wetting, thus requiring the hydrophilization of its surface by exposure to UV or O2 plasma. Yet, the elastomeric state of PDMS translates in a slow, hours to days, process of reducing its surface hydrophilicity—a process denominated as hydrophobic recovery. Using Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM), the present study details the dynamics of hydrophobic recovery of PDMS, on flat bare surfaces and on surfaces embedded with hydrophilic beads. It was found that a thin, stiff, hydrophilic, silica film formed on top of the PDMS material, following its hydrophilization by UV radiation. The hydrophobic recovery of bare PDMS material is the result of an overlap of various nano-mechanical, and diffusional processes, each with its own dynamics rate, which were analyzed in parallel. The hydrophobic recovery presents a hysteresis, with surface hydrophobicity recovering only partially due to a thin, but resilient top silica layer. The monitoring of hydrophobic recovery of PDMS embedded with hydrophilic beads revealed that this is delayed, and then totally stalled in the few-micrometer vicinity of the embedded hydrophilic beads. This region where the hydrophobic recovery stalls can be used as a good approximation of the depth of the resilient, moderately hydrophilic top layer on the PDMS material. The complex processes of hydrophilization and subsequent hydrophobic recovery impact the design, fabrication, and operation of PDMS materials and devices used for diagnostics and medical procedures. Consequently, especially considering the emergence of new surgical procedures using elastomers, the impact of hydrophobic recovery on the surface of PDMS warrants more comprehensive studies. Full article
(This article belongs to the Special Issue Novel Materials in Dentistry and Medical Applications)
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<p>(<b>A</b>) Process of the fabrication of PDMS surfaces embedded with hydrophilic particles. (<b>B</b>) Topography of PDMS surface with embedded hydrophilic particles. (<b>C</b>) SEM image of the surface of PDMS with aggregates of beads.</p> Full article ">Figure 2
<p>Evolution of physico-chemical properties of <span class="html-italic">flat</span> PDMS surfaces, prior to hydrophilization (red) and subsequently, i.e., during hydrophobic recovery (blue). (<b>a</b>) contact angle; (<b>b</b>) roughness; (<b>c</b>) force modulation; and (<b>d</b>) lateral force.</p> Full article ">Figure 3
<p>Evolution of the FTIR-ATR spectra of flat PDMS surfaces, before and immediately after hydrophilization, and at different times after.</p> Full article ">Figure 4
<p>AFM scans of the topography (<b>a</b>) and lateral force (<b>b</b>) of the hydrophilized PDMS immediately after UV radiation.</p> Full article ">Figure 5
<p>Variation of the lateral force for PDMS surface away (blue) and in the vicinity (red) of hydrophilic entities. The associated later force scans are indicated at the respective positions in time during hydrophobic recovery.</p> Full article ">Figure 6
<p>Sequence of histograms of the lateral force readings at various stages of hydrophobic recovery.</p> Full article ">Figure 7
<p>Sequence of double histograms of topography-lateral force readings at various stages of hydrophobic recovery.</p> Full article ">Figure 8
<p>Mechanism of hydrophobic recovery for bare PDMS and PDMS embedded with hydrophilic beads.</p> Full article ">
11 pages, 2056 KiB  
Article
Experimental and Theoretical Investigations of Three-Ring Ester/Azomethine Materials
by Fowzia S. Alamro, Nada S. Al-Kadhi, Sobhi M. Gomha, Saheed A. Popoola, Muna S. Khushaim, Omaima A. Alhaddad and Hoda A. Ahmed
Materials 2022, 15(6), 2312; https://doi.org/10.3390/ma15062312 - 21 Mar 2022
Cited by 6 | Viewed by 1736
Abstract
New three-ring ester/azomethine homologues series, (E)-4-((4-hydroxybenzylidene)amino)phenyl 4-(alkoxy)benzoate In, were prepared and their properties were investigated experimentally and theoretically. FT-IR, NMR, and elemental analyses were used to confirm the chemical structures of the synthesized compounds. The mesomorphic activities of the planned homologues [...] Read more.
New three-ring ester/azomethine homologues series, (E)-4-((4-hydroxybenzylidene)amino)phenyl 4-(alkoxy)benzoate In, were prepared and their properties were investigated experimentally and theoretically. FT-IR, NMR, and elemental analyses were used to confirm the chemical structures of the synthesized compounds. The mesomorphic activities of the planned homologues were evaluated using differential scanning calorimetry (DSC) and polarized optical microscopy. All of the homologous examined were found to have non-mesomorphic properties. Theoretical calculations using the density functional theory (DFT) were used to validate the experimental data and determine the most stable conformation of the synthesized compounds. All calculated conformers’ thermal properties, dipole moments, and polarizability were discussed. The results show that the terminal alkoxy chain length affects the thermal parameters of the conformers. The correlations between these parameters’ values and the conformer type were demonstrated. The base component was expected to be in two conformers according to the orientation of the N atom of imine-linkage. DFT calculations revealed the more probable of the two possible conformers, and the incorporation of the alkoxy terminal chain in one position affect its geometrical and mesomerphic characteristics. Full article
(This article belongs to the Special Issue Design of New Material through Advanced Theoretical Approach and Experimental Technique)
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<p>Molecular structure of investigated series <b>I</b><span class="html-italic">n</span>.</p> Full article ">Figure 2
<p>DSC thermogram of sample <b>I</b><span class="html-italic">6</span> on heating/ cooling cycles with rate 10 °C min<sup>−1</sup>.</p> Full article ">Figure 3
<p>Dependency of alkoxy chain length (n) on the thermal properties of series <b>I</b><span class="html-italic">n</span>.</p> Full article ">Figure 4
<p>Configurationally isomers of two possible conformers of <b>I</b><span class="html-italic">6</span> and <b>I</b><span class="html-italic">12</span> derivatives as examples.</p> Full article ">Figure 5
<p>FOM’s calculated at B3LYP/6-31G(d.p) for investigated series <b>I</b><span class="html-italic">n</span>.</p> Full article ">Figure 6
<p>MEP calculated at B3LYP/6-31G(d.p) for the isomer <b>I</b><span class="html-italic">6</span>.</p> Full article ">Scheme 1
<p>Synthetic method of series <b>I</b><span class="html-italic">n</span>.</p> Full article ">
13 pages, 3119 KiB  
Article
Low-Velocity Impact Response on Glass Fiber Reinforced 3D Integrated Woven Spacer Sandwich Composites
by Mahfuz Bin Rahman and Lvtao Zhu
Materials 2022, 15(6), 2311; https://doi.org/10.3390/ma15062311 - 21 Mar 2022
Cited by 12 | Viewed by 2451
Abstract
This study presents an experimental investigation on the low-velocity impact response of three-dimensional integrated woven spacer sandwich composites made of high-performance glass fiber reinforced fabric and epoxy resin. 3D integrated woven spacer sandwich composites with five different specifications were produced using a hand [...] Read more.
This study presents an experimental investigation on the low-velocity impact response of three-dimensional integrated woven spacer sandwich composites made of high-performance glass fiber reinforced fabric and epoxy resin. 3D integrated woven spacer sandwich composites with five different specifications were produced using a hand lay-up process and tested under low-velocity impact with energies of 5 J, 10 J, and 15 J. The results revealed that the core pile’s heights and diverse impact energies significantly affect the stiffness and energy absorption capacity. There is no significant influence of face sheet thickness on impact response. Moreover, the damage morphologies of 3D integrated woven spacer sandwich composites under different impact energies were analyzed by simple visualization of the specimen. Different damage and failure mechanisms were observed, including barely visible damage, visible damage, and clearly visible damage. Moreover, it was noticed that the damage of 3D integrated woven spacer sandwich composites samples only constraints to the impacted area and does not affect the integrity of the samples. Full article
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<p>Three-dimensional integrated woven spacer fabric.</p> Full article ">Figure 2
<p>Schematic diagram of the hand lay-up technique.</p> Full article ">Figure 3
<p>Drop weight impact test specimen.</p> Full article ">Figure 4
<p>(<b>a</b>) Instron Dynatup 9250 impact test device. (<b>b</b>) Schematic diagram of clamping system and impactor geometrics.</p> Full article ">Figure 5
<p>Force-deformation curves of five groups of 3D integrated woven spacer sandwich composites under different impact energy levels (<b>a</b>) 5 J, (<b>b</b>) 10 J, (<b>c</b>) 15 J.</p> Full article ">Figure 5 Cont.
<p>Force-deformation curves of five groups of 3D integrated woven spacer sandwich composites under different impact energy levels (<b>a</b>) 5 J, (<b>b</b>) 10 J, (<b>c</b>) 15 J.</p> Full article ">Figure 6
<p>Impact damage samples under impact energies (<b>a</b>) 5 J, (<b>b</b>) 10 J, and (<b>c</b>) 15 J.</p> Full article ">Figure 6 Cont.
<p>Impact damage samples under impact energies (<b>a</b>) 5 J, (<b>b</b>) 10 J, and (<b>c</b>) 15 J.</p> Full article ">Figure 7
<p>Energy absorption graph of 3D integrated woven spacer sandwich composites under impact energies (<b>a</b>) 5 J, (<b>b</b>) 10 J, and (<b>c</b>) 15 J.</p> Full article ">Figure 7 Cont.
<p>Energy absorption graph of 3D integrated woven spacer sandwich composites under impact energies (<b>a</b>) 5 J, (<b>b</b>) 10 J, and (<b>c</b>) 15 J.</p> Full article ">
14 pages, 27793 KiB  
Article
Design, Synthesis and Adsorption Evaluation of Bio-Based Lignin/Chitosan Beads for Congo Red Removal
by Xiaobing Han, Rong Li, Pengpai Miao, Jie Gao, Guowen Hu, Yuan Zhao and Tao Chen
Materials 2022, 15(6), 2310; https://doi.org/10.3390/ma15062310 - 21 Mar 2022
Cited by 27 | Viewed by 2732
Abstract
The morphology and intermolecular interaction are two of the most important factors in the design of highly efficient dye adsorbent in the industry. Millimeter-sized, bead-type, bio-based lignin/chitosan (Lig/CS) adsorbent was designed for the removal of Congo red (CR), based on the electrostatic attraction, [...] Read more.
The morphology and intermolecular interaction are two of the most important factors in the design of highly efficient dye adsorbent in the industry. Millimeter-sized, bead-type, bio-based lignin/chitosan (Lig/CS) adsorbent was designed for the removal of Congo red (CR), based on the electrostatic attraction, π-π stacking, and hydrogen bonding, which were synthesized through the emulsification of the chitosan/lignin mixture followed by chemical cross-linking. The effects of the lignin/chitosan mass ratio, initial pH, temperature, concentration, and contact time on the adsorption were thoroughly investigated. The highest adsorption capacity (173 mg/g) was obtained for the 20 wt% Lig/CS beads, with a removal rate of 86.5%. To investigate the adsorption mechanism and recyclability, an evaluation of the kinetic model and an adsorption/desorption experiment were conducted. The adsorption of CR on Lig/CS beads followed the type 1 pseudo-second-order model, and the removal rate for CR was still above 90% at five cycles. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Lignin/chitosan absorbent designed with different intermolecular interactions.</p> Full article ">Figure 2
<p>Synthesis procedure of the bio-based Lig/CS beads.</p> Full article ">Figure 3
<p>Image of the pure CS beads and 20% Lignin/Chitosan (Lig/CS) beads.</p> Full article ">Figure 4
<p>SEM images of the pure CS beads (<b>a</b>,<b>b</b>) and 20% Lig/CS beads (<b>c</b>,<b>d</b>) with different resolution.</p> Full article ">Figure 5
<p>FTIR spectra of the CS, CS beads, Lig, and 20% Lig/CS beads.</p> Full article ">Figure 6
<p>TG spectra of the Lig/CS beads with different lignin content.</p> Full article ">Figure 7
<p>Effect of lignin content on the adsorption capacity. (<span class="html-italic">C</span><sub>0</sub> = 200 mg/L, pH = 7, T = 25 °C, t = 24 h).</p> Full article ">Figure 8
<p>Effect of the initial pH on the adsorption capacity with 20% Lig/CS beads. (<span class="html-italic">C</span><sub>0</sub> = 200 mg/L, T = 25 °C, t = 24 h).</p> Full article ">Figure 9
<p>Effect of the temperature on the adsorption capacity with 20% Lig/CS beads. (<span class="html-italic">C</span><sub>0</sub> = 200 mg/L, pH = 3, t = 24 h).</p> Full article ">Figure 10
<p>Effect of the initial concentration and contact time on the adsorption capacity Q (mg/g) with 20% Lig/CS beads. (pH = 3, T = 35 °C).</p> Full article ">Figure 11
<p>Fitting of pseudo-first-order (<b>a</b>), type 1 pseudo-second-order (<b>b</b>), and type 2 pseudo-second-order (<b>c</b>) kinetic models for the adsorption of CR.</p> Full article ">Figure 12
<p>(<b>a</b>) Effect of recycling times on the adsorption capacity Q (mg/g) with 20% Lig/CS beads (<span class="html-italic">C</span><sub>0</sub> = 10 mg/L, pH = 3, T = 35 °C, t = 4 h); (<b>b</b>) FTIR spectra of 20% Lig/CS beads before adsorption and after regeneration.</p> Full article ">
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