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Materials, Volume 13, Issue 3 (February-1 2020) – 316 articles

Cover Story (view full-size image): The immobilization of antimicrobial agents on plastic surfaces through easy methodologies has attracted a great deal of research over the last few years, to afford scalable functional materials endowed with antimicrobial activity. Our studies deal with the synthesis of new antimicrobial ruthenium complexes bearing a long aliphatic chain, a structural feature that was exploited in tethering them onto a polystyrene surface through hydrophobic interactions, thus affording antimicrobial composites. View this paper.
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12 pages, 3102 KiB  
Article
MgO-Lignin Dual Phase Filler as an Effective Modifier of Polyethylene Film Properties
by Karol Bula, Grzegorz Kubicki, Teofil Jesionowski and Łukasz Klapiszewski
Materials 2020, 13(3), 809; https://doi.org/10.3390/ma13030809 - 10 Feb 2020
Cited by 19 | Viewed by 3501
Abstract
Functional magnesium oxide-lignin hybrid materials were obtained via mechanical grinding. Their particle shape and size as well as physicochemical properties were characterized. MgO-lignin materials with biocomponent content (between 20% and 80% amount of total weight of filler) were used as a partially bio-structured [...] Read more.
Functional magnesium oxide-lignin hybrid materials were obtained via mechanical grinding. Their particle shape and size as well as physicochemical properties were characterized. MgO-lignin materials with biocomponent content (between 20% and 80% amount of total weight of filler) were used as a partially bio-structured modifier of low density polyethylene. The composites with 5% by weight of dual fillers and polyethylene grafted with maleic anhydride were compounded in a twin screw extruder working in co-rotating mode. The prepared blends were cast extruded using a single screw extruder and laboratory cast line. The properties of the obtained films were verified in case of their weldability. The seal strength as well as shear test and tear strength of the welded sheets were examined. The results showed that the shortest equivalent time required to perform correct weld occurred in the system, where the highest amount of lignin was used in hybrid filler MgO-L (1:5 w/w). From mechanical tests of welds, a sharp increase in ultimate seal force was noticed for almost all compositions with lignin, especially where MgO was coupled with a high lignin content. For those composition seal open force raised up to 37.0 N, from the value of 23.6 N, achieved for neat low density polyethylene (LDPE). Tear strength of weld sheets confirmed once more that LDPE composition with MgO-L (1:5 w/w) achieved the highest ultimate force with its value of 71.5 N, and it was ~20.0 N higher than in the case of neat LDPE. Full article
(This article belongs to the Special Issue Composite Materials: New Design Trends, Interphase Characterization and Lifecycle)
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Figure 1
<p>Digital photo of the obtained hybrid fillers.</p> Full article ">Figure 2
<p>SEM images of MgO (<b>a</b>), lignin (<b>b</b>) and MgO-lignin hybrid materials with a weight ratio of components equal to: 5:1 <span class="html-italic">w</span>/<span class="html-italic">w</span> (<b>c</b>), 1:1 <span class="html-italic">w</span>/<span class="html-italic">w</span> (<b>d</b>), and 1:5 <span class="html-italic">w</span>/<span class="html-italic">w</span> (<b>e</b>).</p> Full article ">Figure 3
<p>FTIR spectra of MgO and lignin (<b>a</b>) and MgO-lignin hybrid materials (<b>b</b>).</p> Full article ">Figure 4
<p>TGA curves of MgO and lignin (<b>a</b>) and MgO-lignin hybrid materials (<b>b</b>).</p> Full article ">Figure 5
<p>Required heating time of the tested films with relation to its thickness.</p> Full article ">Figure 6
<p>Comparison of the seal open force for tested materials.</p> Full article ">Figure 7
<p>Comparison of the ultimate shear force applied in lap shear test.</p> Full article ">Figure 8
<p>Comparison of the ultimate shear force applied in lap shear test.</p> Full article ">Figure 9
<p>View of the welded specimens mounted in tensile machine grips, in tested mode: (<b>a</b>) seal strength, (<b>b</b>) lap shear test, and (<b>c</b>) tear the weld test.</p> Full article ">
14 pages, 8430 KiB  
Article
Stability of a Melt Pool during 3D-Printing of an Unsupported Steel Component and Its Influence on Roughness
by Mateusz Skalon, Benjamin Meier, Andreas Gruberbauer, Sergio de Traglia Amancio-Filho and Christof Sommitsch
Materials 2020, 13(3), 808; https://doi.org/10.3390/ma13030808 - 10 Feb 2020
Cited by 15 | Viewed by 4230
Abstract
The following work presents the results of an investigation of the cause–effect relationship between the stability of a melt pool and the roughness of an inclined, unsupported steel surface that was 3D-printed using the laser powder bed fusion (PBF-L/M) process. In order to [...] Read more.
The following work presents the results of an investigation of the cause–effect relationship between the stability of a melt pool and the roughness of an inclined, unsupported steel surface that was 3D-printed using the laser powder bed fusion (PBF-L/M) process. In order to observe the balling effect and decrease in surface quality, the samples were printed with no supporting structures placed on the downskin. The stability of the melt pool was investigated as a function of both the inclination angle and along the length of the melt pool. Single-track cross-sections were described by shape parameters and were compared and used to calculate the forces acting on the melt pool as the downskin was printed. The single-melt track tests were printed to produce a series of samples with increasing inclination angles with respect to the baseplate. The increasing angles enabled us to physically simulate specific solidification conditions during the sample printing process. As the inclination angle of the unsupported surface increased, the melt-pool altered in terms of its size, geometry, contact angles, and maximum length of stability. The balling phenomenon was observed, quantified, and compared using roughness tests; it was influenced by the melt track stability according to its geometry. The research results show that a higher linear energy input may decrease the roughness of unsupported surfaces with low inclination angles, while a lower linear energy input may be more effective with higher inclination angles. Full article
(This article belongs to the Special Issue Laser Materials Processing 2019)
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Figure 1
<p>AISI 316L austenitic stainless-steel powder: (<b>a</b>) Grain size distribution, (<b>b</b>) SEM micrograph.</p> Full article ">Figure 2
<p>(<b>a</b>) An overview of the set of cuboidal samples and their location on the build-plate; (<b>b</b>) scheme of a sample used to simulate the increasing inclination angle, where α is the leaning angle of an unsupported surface and β is the inclination angle of a slope, with β = 90 − α.</p> Full article ">Figure 3
<p>Schematics of the melt pool cross-sections: (<b>a</b>) Arrangement along the edge of the printed area; (<b>b</b>) forces acting on the melt pool when placed on an incline, and (<b>c</b>) display of specific points and parameters. L<sub>t</sub>—Layer thickness; g—gravitational constant; σ—surface tension.</p> Full article ">Figure 4
<p>Top view of single melt tracks printed on slopes. (<b>a</b>) Series A; (<b>b</b>) series B.</p> Full article ">Figure 5
<p>Measured inclination angle (β<sub>m</sub>) as a function of the designed one (β) for (<b>a</b>) series A and (<b>b</b>) series B.</p> Full article ">Figure 6
<p>Melt-pool length (L) for (<b>a</b>) series A, (<b>b</b>) series B, and melt-pool height (h) as a function of β<sub>m</sub> (<b>c</b>) for series A and (<b>d</b>) series B.</p> Full article ">Figure 7
<p>Area (A) for (<b>a</b>) series A and (<b>b</b>) series B, and radius (R) as a function of β<sub>m</sub> (<b>c</b>) for series A and (<b>d</b>) series B.</p> Full article ">Figure 8
<p>Advancing wetting angle (Θ<sub>adv</sub>) for (<b>a</b>) series A and (<b>b</b>) series B, and receding wetting angle Θ<sub>rec</sub> (R) as a function of β<sub>m</sub> (<b>c</b>) for series A and (<b>d</b>) series B.</p> Full article ">Figure 9
<p>Forces (Equation (1)) acting on the melt pool for series A and B.</p> Full article ">Figure 10
<p>(<b>a</b>) Capillary stability of an unsegmented cylinder of a liquid on a solid substrate; (<b>b</b>) stability map based on [<a href="#B7-materials-13-00808" class="html-bibr">7</a>]. λ is the length of a melt pool and D is the semi-cylinder (melt-pool) diameter.</p> Full article ">Figure 11
<p>(<b>a</b>) Stability factor <math display="inline"><semantics> <mi mathvariant="sans-serif">Φ</mi> </semantics></math>/π as a function of β inclination angle; (<b>b</b>) maximum length of a stable liquid cylinder.</p> Full article ">Figure 12
<p>Stability map for series A and series B. The circular and square outlines represent values that were calculated, assuming melt-pool lengths of 365 μm for series A and 380 μm for series B. Solid circles or squares indicate measurement points for a known melt-pool length.</p> Full article ">Figure 13
<p>Representative overview of unsupported, inclined surfaces (downskins) from selected samples: (<b>a</b>) Series A; (<b>b</b>) series B.</p> Full article ">Figure 14
<p>Cross-section of downskin areas: (<b>a</b>) Series A; (<b>b</b>) series B.</p> Full article ">Figure 15
<p>Comparison of roughness measurements for downskins: (<b>a</b>) R<sub>a</sub>, parallel to the X–Y printing plane; (<b>b</b>) R<sub>a</sub>, perpendicular to the X–Y printing plane; (<b>c</b>) R<sub>z</sub>, parallel to the X–Y printing plane; (<b>d</b>) R<sub>z</sub>, perpendicular to the X–Y printing plane.</p> Full article ">
14 pages, 6788 KiB  
Article
Effect of Ultrasonic Bending Vibration Introduced by the L-shaped Ultrasonic Rod on Solidification Structure and Segregation of Large 2A14 Ingots
by Chen Shi, Yongjun Wu, Daheng Mao and Gaofeng Fan
Materials 2020, 13(3), 807; https://doi.org/10.3390/ma13030807 - 10 Feb 2020
Cited by 10 | Viewed by 3510
Abstract
In order to achieve long-term and stable ultrasonic treatment in the direct chill semi-continuous casting process, a new L-shaped ceramic ultrasonic wave guide rod is designed to introduce ultrasonic bending vibration into 2A14 aluminum alloy melt. The effect of ultrasonic bending vibration on [...] Read more.
In order to achieve long-term and stable ultrasonic treatment in the direct chill semi-continuous casting process, a new L-shaped ceramic ultrasonic wave guide rod is designed to introduce ultrasonic bending vibration into 2A14 aluminum alloy melt. The effect of ultrasonic bending vibration on the solidification structure and composition segregation of large 2A14 aluminum alloy ingots (φ 830 mm × 6000 mm) in the process of semi-continuous casting were studied by means of a direct reading spectrometer, scanning electron microscope, metallographic microscope, and hardness test. The ultrasonic ingot treated by bending vibration was compared with the ingot without ultrasonic treatment and the ingot treated by the traditional straight-rod titanium alloy wave guide rod. The results show that, during the solidification of 2A14 aluminum alloy, ultrasonic treatment can significantly refine the grain, break up the agglomerated secondary phase, and make its distribution uniform. The macro-segregation degree of solute including the negative segregation at the edge of the ingots and the positive segregation in the center can be reduced. Through comparative analysis, the macrostructure of the ingot, treated by the L-shaped ceramic ultrasonic wave guide rod, was found to be better than that of the ingot treated by the traditional straight-rod titanium alloy wave guide rod. In particular, the grain refinement effect at the edge of the ingot was the best, the secondary phase was smaller, more solute elements can be dissolved into the α-Al matrix, and the ability of the L-shaped ultrasonic wave guide rod to restrain segregation was stronger at the edge of the ingot. Full article
(This article belongs to the Special Issue Ultrasound for Material Characterization and Processing)
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Figure 1
<p>Structure of ultrasonic guided wave device.</p> Full article ">Figure 2
<p>2A14 aluminum alloy ultrasonic semi-continuous casting: (<b>a</b>) schematic diagram of casting; (<b>b</b>) photo of casting site; and (<b>c</b>) ingot product.</p> Full article ">Figure 3
<p>Sampling locations of ingot samples.</p> Full article ">Figure 4
<p>Macrostructure of obtained under different processing conditions: (<b>a</b>) no ultrasonic treatment; (<b>b</b>) treatment by the L-shaped ultrasonic wave guide rod; (<b>c</b>) treatment by the straight-rod ultrasonic wave guide rod.</p> Full article ">Figure 5
<p>Microstructure of obtained under different processing conditions: (<b>a</b>) Center of ingot without ultrasonic; (<b>b</b>) 1/2 radius of ingot without ultrasonic; (<b>c</b>) edge of ingot without ultrasonic; (<b>d</b>) center of ingot by L-shaped ultrasonic; (<b>e</b>) 1/2 radius of ingot by L-shaped ultrasonic; (<b>f</b>) edge of ingot by L-shaped ultrasonic; (<b>g</b>) center of ingot by straight-rod ultrasonic; (<b>h</b>) 1/2 radius of ingot by straight-rod ultrasonic; and (<b>i</b>) edge of ingot by straight-rod ultrasonic.</p> Full article ">Figure 6
<p>Distribution of grain size of ingots under different processing conditions.</p> Full article ">Figure 7
<p>Distribution of the secondary phase of the ingots under different processing conditions: (<b>a</b>) Center of ingot without ultrasonic; (<b>b</b>) 1/2 radius of ingot without ultrasonic; (<b>c</b>) edge of ingot without ultrasonic; (<b>d</b>) center of ingot by L-shaped ultrasonic; (<b>e</b>) 1/2 radius of ingot by L-shaped ultrasonic; (<b>f</b>) edge of ingot by L-shaped ultrasonic; (<b>g</b>) center of ingot by straight-rod ultrasonic; (<b>h</b>) 1/2 radius of ingot by straight-rod ultrasonic; and (<b>i</b>) edge of ingot by straight-rod ultrasonic.</p> Full article ">Figure 8
<p>Distribution of the secondary phase in the grain at the 1/2 radius: (<b>a</b>) No ultrasonic treatment; (<b>b</b>) treatment by the L-shaped ultrasonic wave guide rod; (<b>c</b>) treatment by the straight-rod ultrasonic wave guide rod.</p> Full article ">Figure 9
<p>Area percentage of each secondary phase in the grain at the 1/2 radius.</p> Full article ">Figure 10
<p>Results and areas of line scan analysis of main alloy elements in the ingots under different processing conditions: (<b>a</b>) No ultrasonic treatment; (<b>b</b>) treatment by the L-shaped ultrasonic wave guide rod; and (<b>c</b>) treatment by the straight-rod ultrasonic wave guide rod.</p> Full article ">Figure 11
<p>Variation of segregation rate of Cu (<b>a</b>), Mg (<b>b</b>), and Si (<b>c</b>) elements in the cross section of ingots under different processing conditions.</p> Full article ">Figure 12
<p>Hardness test results along the radial direction of the ingots under different processing conditions.</p> Full article ">
11 pages, 2192 KiB  
Article
Effect of Diisocyanates as Compatibilizer on the Properties of BF/PBAT Composites by In Situ Reactive Compatibilization, Crosslinking and Chain Extension
by Xiwei Xie, Caili Zhang, Yunxuan Weng, Xiaoqian Diao and Xinyu Song
Materials 2020, 13(3), 806; https://doi.org/10.3390/ma13030806 - 10 Feb 2020
Cited by 27 | Viewed by 3966
Abstract
Due to the hydrophobic nature of poly (butylene terephthalate) (PBAT), and the hydrophilic nature of bamboo flour (BF), a BF/PBAT (50/50) blend shows low mechanical properties, and especially shows poor impact strength. In order to increase the interfacial adhesion between BF and PBAT, [...] Read more.
Due to the hydrophobic nature of poly (butylene terephthalate) (PBAT), and the hydrophilic nature of bamboo flour (BF), a BF/PBAT (50/50) blend shows low mechanical properties, and especially shows poor impact strength. In order to increase the interfacial adhesion between BF and PBAT, diisocyanate was used as a reactive compatibilizer to modify bamboo powder. A series of BF/PBAT composites were prepared by the method of mixing and melting in an internal mixer. After adding reactive compatibilizer 4,4′-methylenebis(phenyl isocyanate) (MDI), BF/PBAT (50/50) composites with high mechanical properties were successfully prepared. The tensile strength, elongation at break, and impact strength of the BF/MDI-2/PBAT composite with 2 wt % MDI content were increased by 1.9, 6.8, and 4.3 times respectively over the BF/PBAT blend without the added MDI. The higher toughening effect of MDI in BF/PBAT composites can be mainly ascribed to the improved interface bonding between BF and PBAT. The isocyanate group of MDI can react with the hydroxyl group on the BF surface and in situ formation of the carbamate group on the BF surface. The residual isocyanate can then react with the hydroxyl group of PBAT and form carbamate groups. The rheological behaviors demonstrate that addition of appropriate amounts of MDI, 1 wt % and 2 wt %, can promote the flowability of the molten BF/PBAT composites due to the decrease in interparticle interaction between bamboo powder and the increase in the thermal motion of the molecules. Full article
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Figure 1
<p>Effect of 4,4-methylenebis (phenyldiisocyanate) (MDI) contents on the mechanical properties of BF/PBAT composite: (<b>a</b>) tensile strength, (<b>b</b>) tensile modulus, (<b>c</b>) elongation at break, and (<b>d</b>) impact strength.</p> Full article ">Figure 2
<p>ATR spectra of pure PBAT, BF, MDI, and BF/PBAT composites.</p> Full article ">Figure 3
<p>Reaction mechanism of BF/PBAT composites modified by MDI.</p> Full article ">Figure 4
<p>Effect of different contents of MDI on: (<b>a</b>) complex viscosity, (<b>b</b>) storage modulus, (<b>c</b>) loss modulus, and (<b>d</b>) damping factor.</p> Full article ">Figure 5
<p>(<b>a</b>) TGA and (<b>b</b>) DTG curves of BF/PBAT composites without and with different contents of MDI.</p> Full article ">Figure 6
<p>Fracture surface morphologies of: (<b>a</b>) BF/PBAT, (<b>b</b>) BF/MDI-1/PBAT, (<b>c</b>) BF/MDI-2/PBAT, (<b>d</b>) BF/MDI-3/PBAT and (<b>e</b>) BF/MDI-4/PBAT.</p> Full article ">
11 pages, 4540 KiB  
Article
Rodlike YMn2O5 Powders Derived from Hydrothermal Process Using Oxygen as Oxidant
by Jun Shi, Jing Wang, Huifen He, Yang Lu and Zhongxiang Shi
Materials 2020, 13(3), 805; https://doi.org/10.3390/ma13030805 - 10 Feb 2020
Cited by 5 | Viewed by 2705
Abstract
A facile approach is proposed herein to fabricate YMn2O5 powders with the hydrothermal method with oxygen as an oxidant. The structure and morphology of the as-synthesized YMn2O5 powders were characterized by XRD, SEM, and high-resolution transmission electron [...] Read more.
A facile approach is proposed herein to fabricate YMn2O5 powders with the hydrothermal method with oxygen as an oxidant. The structure and morphology of the as-synthesized YMn2O5 powders were characterized by XRD, SEM, and high-resolution transmission electron microscopy (HRTEM). The results manifested that the main factors that affected the formation of the rod-like YMn2O5 structures were the stirring time, hydrothermal temperature, and hydrothermal time. The oxidation time in the air had a remarkable effect on the final product by oxidizing Mn2+ ions to Mn3+ ions and Mn4+ ions. The obtained YMn2O5 powder was single crystalline and possessed a nanorod morphology, where the growth direction was along the c axis. The possible formation mechanism involved a dissolution–crystallization mechanism. Under the 397 nm excitation, the Mn4+ ions exhibited an intense orange emission at 596 nm. The energy bandgap of YMn2O5 powders was 1.18 eV. Full article
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Figure 1

Figure 1
<p>Digital images of the precursor solution with different stirring times.</p> Full article ">Figure 2
<p>XRD patterns of products obtained by hydrothermal treatment at 180 °C at different oxidation times in the air: (<b>a</b>) 0 min; (<b>b</b>) 10 min; (<b>c</b>) 20 min; (<b>d</b>) 30 min.</p> Full article ">Figure 3
<p>SEM images of hydrothermal products obtained with different stirring times: (<b>a</b>) 0 min; (<b>b</b>) 10 min; (<b>c</b>) 20 min; (<b>d</b>) 30 min.</p> Full article ">Figure 4
<p>XRD patterns of samples synthesized at different hydrothermal temperatures: (<b>a</b>) 140 °C; (<b>b</b>) 160 °C; (<b>c</b>) 170 °C; (<b>d</b>) 180 °C; (<b>e</b>) 200 °C; (<b>f</b>) 220 °C.</p> Full article ">Figure 5
<p>SEM images of samples synthesized at different hydrothermal temperatures: (<b>a</b>) 140 °C; (<b>b</b>) 160 °C; (<b>c</b>) 170 °C; (<b>d</b>) 180 °C; (<b>e</b>) 200 °C; (<b>f</b>) 220 °C.</p> Full article ">Figure 6
<p>XRD patterns of samples synthesized at 180 °C for different hydrothermal times: (<b>a</b>) 6 h; (<b>b</b>) 12 h; (<b>c</b>) 18 h; (<b>d</b>) 24 h; (<b>e</b>) 48 h.</p> Full article ">Figure 7
<p>SEM images of samples synthesized at different hydrothermal times: (<b>a</b>) 6 h; (<b>b</b>) 12 h; (<b>c</b>) 18 h; (<b>d</b>) 24 h; (<b>e</b>) 48 h.</p> Full article ">Figure 7 Cont.
<p>SEM images of samples synthesized at different hydrothermal times: (<b>a</b>) 6 h; (<b>b</b>) 12 h; (<b>c</b>) 18 h; (<b>d</b>) 24 h; (<b>e</b>) 48 h.</p> Full article ">Figure 8
<p>TEM, high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) images of YMn<sub>2</sub>O<sub>5</sub>: (<b>a</b>) TEM; (<b>b</b>) HRTEM; (<b>c</b>) amplification of the HRTEM; (<b>d</b>) SAED.</p> Full article ">Figure 9
<p>Schematic model of dissolution and recrystallization for YMn<sub>2</sub>O<sub>5</sub>.</p> Full article ">Figure 10
<p>Excitation spectra (<b>a</b>) and emission spectra (<b>b</b>) of the YMn<sub>2</sub>O<sub>5</sub> sample.</p> Full article ">Figure 11
<p>(<b>a</b>) UV–VIS absorption spectra of the YMn<sub>2</sub>O<sub>5</sub> sample, (<b>b</b>) Tauc–Mott plot of (αhν)<sup>1/2</sup> versus hν.</p> Full article ">
18 pages, 3602 KiB  
Article
Experimental Study on Water Recovery from Flue Gas Using Macroporous Ceramic Membrane
by Chao Cheng, Heng Zhang and Haiping Chen
Materials 2020, 13(3), 804; https://doi.org/10.3390/ma13030804 - 10 Feb 2020
Cited by 19 | Viewed by 2823
Abstract
In this work, a ceramic membrane tube with a pore size of 1 μm was used to conduct experimental research on moisture and waste heat recovery from flue gas. The length, inner/outer diameter, and porosity were 800 mm, 8/12 mm, and 27.2%, respectively. [...] Read more.
In this work, a ceramic membrane tube with a pore size of 1 μm was used to conduct experimental research on moisture and waste heat recovery from flue gas. The length, inner/outer diameter, and porosity were 800 mm, 8/12 mm, and 27.2%, respectively. In the experiments, the flue gas, which was artificially prepared, flowed on the shell side of membrane module. The water coolant passed through the membrane counter-currently with the gas. The effects of flue gas flow rate, flue gas temperature, water coolant flux, and water coolant temperature on the membrane recovery performance were analyzed. The results indicated that, upon increasing the flue gas flow rate and its temperature, both the amount of recycled water and the recovered heat increased. The amount of recycled water, recycled water rate, recovered heat, and heat recovery rate all decreased as the water coolant temperature increased. When the water coolant temperature exceeded 30 °C, the amount of recycled water dropped sharply. The maximum amounts of recycled water, recovered heat, and total heat transfer coefficient were 2.93 kg/(m2·h), 3.63 kW/m2, and 224.3 W/(m2·K), respectively. Full article
(This article belongs to the Section Energy Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Microstructure of 1-μm-pore ceramic membrane.</p> Full article ">Figure 2
<p>Schematic of experimental system.</p> Full article ">Figure 3
<p>Effect of flue gas flow rate on (<b>a</b>) water, (<b>b</b>) heat, and (<b>c</b>) total heat transfer coefficient (THTC). (Experimental conditions: flue gas temperature 50 °C, water coolant flux 1.664 × 10<sup>−2</sup> kg/s, water coolant temperature 20 °C).</p> Full article ">Figure 4
<p>Variables changes with flue gas temperature in terms of (<b>a</b>) water, (<b>b</b>) heat, and (<b>c</b>) THTC. (Experimental conditions: flue gas flow rate 1.875 × 10<sup>−4</sup> kg/s, water coolant flux 1.664 × 10<sup>−2</sup> kg/s, water coolant temperature 20 °C).</p> Full article ">Figure 4 Cont.
<p>Variables changes with flue gas temperature in terms of (<b>a</b>) water, (<b>b</b>) heat, and (<b>c</b>) THTC. (Experimental conditions: flue gas flow rate 1.875 × 10<sup>−4</sup> kg/s, water coolant flux 1.664 × 10<sup>−2</sup> kg/s, water coolant temperature 20 °C).</p> Full article ">Figure 5
<p>Vapor content change with flue gas temperature (Flue gas flow rate 1.875 × 10<sup>−4</sup> kg/s).</p> Full article ">Figure 6
<p>Membrane performance changes with water coolant flux in terms of (<b>a</b>) water, (<b>b</b>) heat, and (<b>c</b>) THTC. (Experimental conditions: flue gas flow rate 1.875 × 10<sup>−4</sup> kg/s, flue gas temperature 50 °C, water coolant temperature 20 °C).</p> Full article ">Figure 6 Cont.
<p>Membrane performance changes with water coolant flux in terms of (<b>a</b>) water, (<b>b</b>) heat, and (<b>c</b>) THTC. (Experimental conditions: flue gas flow rate 1.875 × 10<sup>−4</sup> kg/s, flue gas temperature 50 °C, water coolant temperature 20 °C).</p> Full article ">Figure 7
<p>Effect of water coolant temperature in terms of (<b>a</b>) water, (<b>b</b>) heat, and (<b>c</b>) <span class="html-italic">THTC</span>. (Experimental conditions: flue gas flow rate 1.875 × 10<sup>−4</sup> kg/s, flue gas temperature 50 °C, water coolant flux 1.664 × 10<sup>−2</sup> kg/s).</p> Full article ">Figure 7 Cont.
<p>Effect of water coolant temperature in terms of (<b>a</b>) water, (<b>b</b>) heat, and (<b>c</b>) <span class="html-italic">THTC</span>. (Experimental conditions: flue gas flow rate 1.875 × 10<sup>−4</sup> kg/s, flue gas temperature 50 °C, water coolant flux 1.664 × 10<sup>−2</sup> kg/s).</p> Full article ">
14 pages, 1632 KiB  
Article
Material-Oriented Shape Functions for FGM Plate Finite Element Formulation
by Wojciech Gilewski and Jan Pełczyński
Materials 2020, 13(3), 803; https://doi.org/10.3390/ma13030803 - 10 Feb 2020
Cited by 9 | Viewed by 3725
Abstract
A four-noded finite element of a moderately thick plate made of functionally graded material (FGM) is presented. The base element is rectangular and can be extended to any shape using a transformation based on NURBS functions. The proposed 2D shape functions are consistent [...] Read more.
A four-noded finite element of a moderately thick plate made of functionally graded material (FGM) is presented. The base element is rectangular and can be extended to any shape using a transformation based on NURBS functions. The proposed 2D shape functions are consistent with the physical interpretation and describe the states of element displacement caused by unit displacements of nodes. These functions depend on the FGM’s material parameters and are called material-oriented. The shape function matrix is based on a superposition displacement field of two plate strips with 1D exact shape functions. A characteristic feature of the proposed formulation is full coupling of the membrane and bending states in the plate. The analytical form of the stiffness matrix and the nodal load vector was obtained, which leads to the numerical efficiency of the formulation. The element has been incorporated into Abaqus software with the use of Maple program. The finite element shows good convergence properties for different FGM models in the transverse direction to the middle plane of the plate. During derivation of the 2D plate element the formally exact 1D finite element for transverse nonhomogeneous FGM plate strip was developed. Full article
(This article belongs to the Special Issue Advances in Structural Mechanics Modeled with FEM)
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<p>Four-noded rectangular plate element.</p> Full article ">Figure 2
<p>Crossed plate strips.</p> Full article ">Figure 3
<p>Selected transverse nonhomogeneous materials of the plate.</p> Full article ">Figure 4
<p>Plates taken for convergence analysis: simply supported and clamped with concentrated load in the middle.</p> Full article ">Figure 5
<p>Convergence graphs for simply supported plate (multiplier <math display="inline"><semantics> <mrow> <mfrac> <mrow> <mi>P</mi> <msup> <mi>L</mi> <mn>2</mn> </msup> </mrow> <mrow> <msub> <mi>E</mi> <mn>0</mn> </msub> <msup> <mi>h</mi> <mn>3</mn> </msup> </mrow> </mfrac> </mrow> </semantics></math>).</p> Full article ">Figure 6
<p>Convergence graphs for clamped plate (multiplier <math display="inline"><semantics> <mrow> <mfrac> <mrow> <mi>P</mi> <msup> <mi>L</mi> <mn>2</mn> </msup> </mrow> <mrow> <msub> <mi>E</mi> <mn>0</mn> </msub> <msup> <mi>h</mi> <mn>3</mn> </msup> </mrow> </mfrac> </mrow> </semantics></math>).</p> Full article ">Figure 7
<p>Example of free-form element shapes.</p> Full article ">
13 pages, 4690 KiB  
Article
Effect of Rough Surface Platforms on the Mucosal Attachment and the Marginal Bone Loss of Implants: A Dog Study
by Javier Montero, Alberto Fernández-Ruiz, Beatriz Pardal-Peláez, Alvaro Jiménez-Guerra, Eugenio Velasco-Ortega, Ana I. Nicolás-Silvente and Loreto Monsalve-Guil
Materials 2020, 13(3), 802; https://doi.org/10.3390/ma13030802 - 10 Feb 2020
Cited by 8 | Viewed by 3740
Abstract
The preservation of peri-implant tissues is an important factor for implant success. This study aimed to assess the influence of the surface features of a butt-joint platform on soft-tissue attachment and bone resorption after immediate or delayed implant placement. All premolars and first [...] Read more.
The preservation of peri-implant tissues is an important factor for implant success. This study aimed to assess the influence of the surface features of a butt-joint platform on soft-tissue attachment and bone resorption after immediate or delayed implant placement. All premolars and first molars of eight Beagle dogs were extracted on one mandible side. Twelve-weeks later, the same surgery was developed on the other side. Five implants with different platform surface configurations were randomly inserted into the post-extracted-sockets. On the healed side, the same five different implants were randomly placed. Implants were inserted 1 mm subcrestal to the buccal bony plate and were connected to abutments. The primary outcome variables were the supracrestal soft tissue (SST) adaptation and the bone resorption related to the implant shoulder. The SST height was significantly larger in immediate implants (IC95% 3.9–4.9 mm) compared to delayed implants (IC95% 3.1–3.5 mm). Marginal bone loss tended to be higher in immediate implants (IC95% 0.4–0.9 mm) than in delayed implants (IC95% 0.3–0.8 mm). Linear-regression analysis suggested that the SST height was significantly affected by the configuration of the platform (0.3–1.9 mm). Roughened surface platforms resulted in higher SST height when compared to machined surface platforms. Marginal bone loss was less pronounced in roughened designs. Full article
(This article belongs to the Special Issue Materials in Implant Dentistry and Regenerative Medicine)
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<p>The topographic profiles and platform surfaces of the five implant designs evaluated: Straumann BL platform with SLA<sup>®</sup> surface platform; IPX-Std with a fully machined platform; IPX-Half with Nanoblast Plus<sup>®</sup> surface in the outer half of the platform and machined surface in the inner half of the platform; IPX-Full with the whole platform treated with Nanoblast Plus<sup>®</sup> and IPX-Control with full body and platform machined.</p> Full article ">Figure 2
<p>High magnification images (1000×) of the surfaces evaluated; (<b>A</b>) SLA<sup>®</sup> Surface, (<b>B</b>) Nanoblast Plus<sup>®</sup> Surface, and (<b>C</b>) IPX Machined Surface.</p> Full article ">Figure 3
<p>Histological images of immediate implants. (<b>A</b>) Straumann BL; (<b>B</b>) IPX-Std; (<b>C</b>) IPX-Half; (<b>D</b>) IPX-Full; (<b>E</b>) IPX-Control.</p> Full article ">Figure 4
<p>Histological images of delayed implants. (<b>A</b>) Straumann BL; (<b>B</b>) IPX-Std; (<b>C</b>) IPX-Half; (<b>D</b>) IPX-Full; (<b>E</b>) IPX-Control.</p> Full article ">Figure 5
<p>Diagram illustrating the landmarks for histological evaluation. IS—implant shoulder; B—most coronal bone-to-implant contact location; C—top of the alveolar crest; aJE—the apical border of the junctional epithelium; PM—the top of the margin of the peri-implant mucosa.</p> Full article ">
45 pages, 6648 KiB  
Review
Progress and Status of Hydrometallurgical and Direct Recycling of Li-Ion Batteries and Beyond
by François Larouche, Farouk Tedjar, Kamyab Amouzegar, Georges Houlachi, Patrick Bouchard, George P. Demopoulos and Karim Zaghib
Materials 2020, 13(3), 801; https://doi.org/10.3390/ma13030801 - 10 Feb 2020
Cited by 228 | Viewed by 27209
Abstract
An exponential market growth of Li-ion batteries (LIBs) has been observed in the past 20 years; approximately 670,000 tons of LIBs have been sold in 2017 alone. This trend will continue owing to the growing interest of consumers for electric vehicles, recent engagement [...] Read more.
An exponential market growth of Li-ion batteries (LIBs) has been observed in the past 20 years; approximately 670,000 tons of LIBs have been sold in 2017 alone. This trend will continue owing to the growing interest of consumers for electric vehicles, recent engagement of car manufacturers to produce them, recent developments in energy storage facilities, and commitment of governments for the electrification of transportation. Although some limited recycling processes were developed earlier after the commercialization of LIBs, these are inadequate in the context of sustainable development. Therefore, significant efforts have been made to replace the commonly employed pyrometallurgical recycling method with a less detrimental approach, such as hydrometallurgical, in particular sulfate-based leaching, or direct recycling. Sulfate-based leaching is the only large-scale hydrometallurgical method currently used for recycling LIBs and serves as baseline for several pilot or demonstration projects currently under development. Conversely, most project and processes focus only on the recovery of Ni, Co, Mn, and less Li, and are wasting the iron phosphate originating from lithium iron phosphate (LFP) batteries. Although this battery type does not dominate the LIB market, its presence in the waste stream of LIBs causes some technical concerns that affect the profitability of current recycling processes. This review explores the current processes and alternative solutions to pyrometallurgy, including novel selective leaching processes or direct recycling approaches. Full article
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Graphical abstract
Full article ">Figure 1
<p>Cylindrical cell details ((reproduced with permission from Springer Nature Ref. [<a href="#B26-materials-13-00801" class="html-bibr">26</a>]).</p> Full article ">Figure 2
<p>Bill of materials of lithium-cobalt oxide battery (wt.%) (based on data provided by Silveira et al. [<a href="#B27-materials-13-00801" class="html-bibr">27</a>]).</p> Full article ">Figure 3
<p>Energy consumption for different synthesis methods and various active materials (reproduced with permission from The Royal Society of Chemistry Ref. [<a href="#B38-materials-13-00801" class="html-bibr">38</a>]); here, NMC, LMR-NMC, LCO, and LFP are lithium-nickel-manganese-cobalt oxide, Li and Mn-rich lithium-nickel-manganese-cobalt oxide, lithium-cobalt oxide, and lithium-iron phosphate, respectively; and SS and HT are solid state and hydrothermal synthesis methods.</p> Full article ">Figure 4
<p>Gas emissions for synthesis methods for various active materials (reproduced with permission from The Royal Society of Chemistry Ref. [<a href="#B38-materials-13-00801" class="html-bibr">38</a>]); here, NMC and LMR-NMC are lithium-nickel-manganese-cobalt oxide and Li and Mn-rich lithium-nickel-manganese-cobalt oxide; SS and HT are solid state and hydrothermal synthesis methods; and GHG is greenhouse gas.</p> Full article ">Figure 5
<p>Cyclic flow chart of manufacturing, usage, and end-of-life of Li-ion batteries.</p> Full article ">Figure 6
<p>Schematic flow and comparison of three approaches for recycling spent Li-ion batteries (LIBs).</p> Full article ">Figure 7
<p>Thermogravimetry-differential scanning calorimetry (TG-DSC) curves of spent laptop Li-ion batteries in air (reproduced with permission from Springer Nature Ref. [<a href="#B88-materials-13-00801" class="html-bibr">88</a>]).</p> Full article ">Figure 8
<p>H<sub>2</sub>SO<sub>4</sub> recycling process of lithium-iron phosphate (LFP) batteries patented by Recupyl (according to Ref. [<a href="#B46-materials-13-00801" class="html-bibr">46</a>]).</p> Full article ">Figure 9
<p>Selective leaching process proposed by Li et al. (according to [<a href="#B123-materials-13-00801" class="html-bibr">123</a>]); here, LFP is LiFePO<sub>4.</sub></p> Full article ">Figure 10
<p>Selective leaching process proposed by Zheng et al. (according to Ref. [<a href="#B85-materials-13-00801" class="html-bibr">85</a>,<a href="#B126-materials-13-00801" class="html-bibr">126</a>]); here, NMC(OH)<sub>2</sub> and NMC(111) are Ni<sub>1/3</sub>Mn<sub>1/3</sub>Co<sub>1/3(</sub>OH)<sub>2</sub> and LiNi<sub>1/3</sub>Mn<sub>1/3</sub>Co<sub>1/3</sub>O<sub>2</sub>, respectively.</p> Full article ">Figure 11
<p>HCl leaching process proposed by Laucournet et al. (according to [<a href="#B164-materials-13-00801" class="html-bibr">164</a>]); here LFP, LTO, and PVDF are for LiFePO<sub>4</sub>, Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub>, and polyvinylidene fluoride, respectively.</p> Full article ">Figure 12
<p>HNO<sub>3</sub> leaching and electrodeposition process proposed by Li et al. (adapted from [<a href="#B180-materials-13-00801" class="html-bibr">180</a>]); here, LCO and NMP are LiCoO<sub>2</sub> and N-methyl-2-pyrrolidone, respectively.</p> Full article ">Figure 13
<p>H<sub>3</sub>PO<sub>4</sub> leaching process suggested by Yang et al. (according to [<a href="#B76-materials-13-00801" class="html-bibr">76</a>]); here, LFP and EDTA-2Na are for LiFePO<sub>4</sub> and ethylenediamine tetraacetic acid disodium salt, respectively.</p> Full article ">Figure 14
<p>Selective leaching of LFP proposed by Amouzegar et al. (according to [<a href="#B185-materials-13-00801" class="html-bibr">185</a>]); here, LFP is for LiFePO<sub>4</sub>.</p> Full article ">Figure 15
<p>Selective leaching of LFP proposed by Yang et al. (according to [<a href="#B77-materials-13-00801" class="html-bibr">77</a>]).</p> Full article ">Figure 16
<p>LFP dissolution process proposed by Li et al. (according to [<a href="#B207-materials-13-00801" class="html-bibr">207</a>]); here, LFP, PVDF, and NMP are LiFePO<sub>4</sub>, polyvinylidene fluoride, and N-methyl-2-pyrrolidone, respectively.</p> Full article ">Figure 17
<p>Pilot-scale thermal regeneration process of LFP (according to [<a href="#B97-materials-13-00801" class="html-bibr">97</a>]).</p> Full article ">Figure 18
<p>Hydrothermal process proposed by Sloop (according to [<a href="#B218-materials-13-00801" class="html-bibr">218</a>]).</p> Full article ">Figure 19
<p>Iodide relithiation process proposed by Ganter et al. (according to [<a href="#B217-materials-13-00801" class="html-bibr">217</a>]).</p> Full article ">Figure 20
<p>Electrochemical resynthesis process for LCO (according to [<a href="#B219-materials-13-00801" class="html-bibr">219</a>]).</p> Full article ">
14 pages, 6137 KiB  
Article
Effect of Nickel and Titanium on Properties of Fe-Al-Si Alloy Prepared by Mechanical Alloying and Spark Plasma Sintering
by Pavel Novák, Zdeněk Barták, Kateřina Nová and Filip Průša
Materials 2020, 13(3), 800; https://doi.org/10.3390/ma13030800 - 10 Feb 2020
Cited by 9 | Viewed by 2781
Abstract
This paper describes the structure and properties of an innovative Fe-Al-Si alloy with a reduced amount of silicon (5 wt. %) in order to avoid excessive brittleness. The alloy was produced by a combination of mechanical alloying and spark plasma sintering. Nickel and [...] Read more.
This paper describes the structure and properties of an innovative Fe-Al-Si alloy with a reduced amount of silicon (5 wt. %) in order to avoid excessive brittleness. The alloy was produced by a combination of mechanical alloying and spark plasma sintering. Nickel and titanium were independently tested as the alloying elements for this alloy. It was found that wear resistance, which reached values comparable with tool steels, could be further improved by the addition of nickel. Nickel also improved the high-temperature oxidation behavior, because it lowers the liability of the oxide layers to spallation. Both nickel and titanium increased the hardness of the alloy. Titanium negatively influenced oxidation behavior and wear resistance because of the presence of titanium dioxide in the oxide layer and the brittle silicides that caused chipping wear, respectively. Full article
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<p>X-ray diffraction analysis (XRD) patterns of the tested bulk alloys that were produced by mechanical alloying and spark plasma sintering.</p> Full article ">Figure 2
<p>Microstructure of the bulk FeAl35Si5 alloy (<b>a</b>), the FeAl35Si5Ni20 alloy (<b>b</b>), and the FeAl35Si5Ti20 alloy (<b>c</b>) that were produced by mechanical alloying and spark plasma sintering.</p> Full article ">Figure 3
<p>Energy dispersive spectrometer (EDS) elemental map of the bulk FeAl35Si5 alloy.</p> Full article ">Figure 4
<p>EDS elemental map of the bulk FeAl35Si5Ni20 alloy.</p> Full article ">Figure 5
<p>EDS elemental map of the bulk FeAl35Si5Ti20 alloy.</p> Full article ">Figure 6
<p>Wear tracks on the FeAl35Si5 alloy (<b>a</b>), the FeAl35Si5Ni20 alloy (<b>b</b>), and the FeAl35Si5Ti20 alloy (<b>c</b>), as documented by backscattered electrons (BSE)-SEM.</p> Full article ">Figure 7
<p>Dependence of specific weight gain (g∙m<sup>−2</sup>) on the duration of cyclic oxidation at 800 °C in air.</p> Full article ">Figure 8
<p>Dependence of the weight of delaminated oxides (g∙m<sup>−2</sup>) on the duration of cyclic oxidation at 800 °C in air.</p> Full article ">Figure 9
<p>XRD patterns of the tested bulk alloys after cyclic oxidation at 800 °C for 400 h in air.</p> Full article ">Figure 10
<p>Microstructure (secondary electrons (SE)-SEM) of the oxide layers on the bulk alloys after cyclic oxidation at 800 °C for 400 h in air: the FeAl35Si5 alloy (<b>a</b>), the FeAl35Si5Ni20 alloy (<b>b</b>), and the FeAl35Si5Ti20 alloy (<b>c</b>).</p> Full article ">
12 pages, 1861 KiB  
Article
Experimental Study for the Stripping of PTFE Coatings on Al-Mg Substrates Using Dry Abrasive Materials
by Guillermo Guerrero-Vaca, David Carrizo-Tejero, Óscar Rodríguez-Alabanda, Pablo E. Romero and Esther Molero
Materials 2020, 13(3), 799; https://doi.org/10.3390/ma13030799 - 10 Feb 2020
Cited by 10 | Viewed by 3325
Abstract
Polytetrafluoroethylene (PTFE) coatings are used in many applications and processing industries. With their use, they wear out and lose properties and must be replaced by new ones if the cost of the element so advises. There are different stripping techniques, but almost all [...] Read more.
Polytetrafluoroethylene (PTFE) coatings are used in many applications and processing industries. With their use, they wear out and lose properties and must be replaced by new ones if the cost of the element so advises. There are different stripping techniques, but almost all of them are very difficult and require strict environmental controls. It is a challenge to approach the process through efficient and more sustainable techniques. In the present work, we have studied the stripping of PTFE coatings by projection with abrasives (1 step) as an alternative to carbonization + sandblasting procedures (2 steps). For this purpose, different types of abrasives have been selected: brown corundum, white corundum, glass microspheres, plastic particles, and a walnut shell. The tests were performed at pressures from 0.4 to 0.6 MPa on PTFE-coated aluminium substrates of EN AW-5182 H111 alloy. Stripping rates, surface roughness, and substrate hardness have been studied. Scanning electron microscopy (SEM) images of sandblasted specimens have also been obtained. All abrasives improved mechanical and surface properties in one-step vs. two-step processes. The abrasives of plastic and glass microspheres are the most appropriate for the one-step process, which increases the hardness and roughness level Ra in the substrate. Corundum abrasives enable the highest stripping rates. Full article
(This article belongs to the Section Thin Films and Interfaces)
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<p>EN AW-5182 Al-Mg alloy substrate with PTFE coating.</p> Full article ">Figure 2
<p>Diagram and assembly of abrasive particle spraying equipment.</p> Full article ">Figure 3
<p>Stripping rate on PTFE coatings on EN AW-5182 substrate vs. spray pressure with different abrasives: (i) BC-brown corundum, (ii) WC-white corundum, (iii) G-glass microspheres, (iv) P-plastic particles, and (v) WS-walnut shell.</p> Full article ">Figure 4
<p>Ra (<b>a</b>) and Rz (<b>b</b>) values after stripping PTFE coatings on the EN AW 5182 substrates with different abrasives: (i) BC-brown corundum, (ii) WC-white corundum, (iii) G-glass microspheres, (iv) P-plastic particles, and (v) WS-walnut Shell.</p> Full article ">Figure 5
<p>Vickers hardness values with loads of 5 kg (HV5) after stripping PTFE coatings on an EN AW 5182 substrate with different abrasives at 0.4, 0.5, and 0.6 MPa: (i) BC-brown corundum, (ii) WC-white corundum, (iii) G-glass microspheres, (iv) P-plastic particles, and (v) WS-walnut Shell.</p> Full article ">Figure 6
<p>Vickers hardness with loads 5, 10, 20, and 30 kp versus penetration depth in ENAW5182 aluminium substrate, after sandblasting with various abrasives between 0.4 to 0.6 MPa for PTFE stripping.</p> Full article ">Figure 7
<p>SEM images of the various sandblasted samples. (<b>a</b>) State of delivery, (<b>b</b>) brown corundum, (<b>c</b>) white corundum, (<b>d</b>) glass microspheres, (<b>e</b>) plastic particles, and (<b>f</b>) walnut shell.</p> Full article ">
18 pages, 4981 KiB  
Article
Magnesium Reinforced with Inconel 718 Particles Prepared Ex Situ—Microstructure and Properties
by Zuzanka Trojanová, Zdeněk Drozd, Pavel Lukáč, Peter Minárik, Gergely Németh, Sankaranarayanan Seetharaman, Ján Džugan and Manoj Gupta
Materials 2020, 13(3), 798; https://doi.org/10.3390/ma13030798 - 10 Feb 2020
Cited by 7 | Viewed by 3183
Abstract
Magnesium samples reinforced with 0.7, 1.4, and 2.4 vol.% of Inconel 718 particles were prepared using a disintegrated melt deposition technique followed by hot extrusion. Mechanical properties, thermal expansion, and damping were studied with the aim of revealing the particle influence on the [...] Read more.
Magnesium samples reinforced with 0.7, 1.4, and 2.4 vol.% of Inconel 718 particles were prepared using a disintegrated melt deposition technique followed by hot extrusion. Mechanical properties, thermal expansion, and damping were studied with the aim of revealing the particle influence on the microstructure, texture, tensile and compressive behavior, thermal expansion coefficient, and internal friction. The flow stresses are significantly influenced by the test temperature and the vol.% of particles. A substantial asymmetry in the tensile and compressive properties was observed at lower temperatures. This asymmetry is caused by different deformation mechanisms operating in tension and compression. The fiber texture of extruded composite samples, refined grain sizes, and the increased dislocation density improved the mechanical properties. On the other hand, a decrease in the thermal expansion coefficient and internal friction was observed. Full article
(This article belongs to the Special Issue Mechanical and Physical Properties of Metallic Composites)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Microstructure of samples visible in sections perpendicular to the extrusion direction taken for: (<b>a</b>) pure Mg, (<b>b</b>) Mg + 0.7 In718, (<b>c</b>) Mg + 1.4 In718, and (<b>d</b>) Mg + 2.4 In718.</p> Full article ">Figure 2
<p>Microstructure of samples visible in sections parallel to the extrusion direction taken for: (<b>a</b>) pure Mg, (<b>b</b>) Mg + 0.7 In718, (<b>c</b>) Mg + 1.4 In718, and (<b>d</b>) Mg + 2.4 In718.</p> Full article ">Figure 3
<p>Electron back scatter (EBSD) inverse pole figures (IPF) calculated from <a href="#materials-13-00798-f001" class="html-fig">Figure 1</a> for: (<b>a</b>) pure Mg, (<b>b</b>) Mg + 0.7 In718, (<b>c</b>) Mg + 1.4 In718, and (<b>d</b>) Mg + In718 (scale: blue to red).</p> Full article ">Figure 4
<p>True stress–true strain curves obtained in tension and compression for (<b>a</b>,<b>b</b>) pure Mg, (<b>c</b>,<b>d</b>) Mg + 0.7 In718, (<b>e</b>,<b>f</b>) Mg + 1.4 In718, (<b>g</b>,<b>h</b>) Mg + 2.4 In718.</p> Full article ">Figure 4 Cont.
<p>True stress–true strain curves obtained in tension and compression for (<b>a</b>,<b>b</b>) pure Mg, (<b>c</b>,<b>d</b>) Mg + 0.7 In718, (<b>e</b>,<b>f</b>) Mg + 1.4 In718, (<b>g</b>,<b>h</b>) Mg + 2.4 In718.</p> Full article ">Figure 5
<p>Stress–strain curves obtained in tension and compression at room temperature for (<b>a</b>) pure Mg and (<b>b</b>) Mg + 2.4 In718. The tension–compression asymmetry is obvious.</p> Full article ">Figure 6
<p>Tension–compression asymmetry: (<b>a</b>) TYS and CYS estimated for Mg + 0.7 In718 at various temperatures and (<b>b</b>) the difference between TYS and CYS estimated at room temperature depending on the vol.% of Inconel particles.</p> Full article ">Figure 7
<p>Temperature dependence of characteristic stresses obtained in (<b>a</b>) tension and in (<b>b</b>) compression for pure Mg.</p> Full article ">Figure 8
<p>Characteristic stresses estimated for various particles’ content and temperatures in tension: (<b>a</b>) tensile yield stress (TYS) and (<b>b</b>) maximum tensile stress (MTS).</p> Full article ">Figure 9
<p>Characteristic stresses estimated for various particles content and temperatures in compression: (<b>a</b>) compression yield stress (CYS) and (<b>b</b>) compressive peak stress (CPS).</p> Full article ">Figure 10
<p>Concentration dependence of the thermal expansion coefficient (CTE).</p> Full article ">Figure 11
<p>Concentration dependence of logarithmic decrement.</p> Full article ">Figure 12
<p>EBSD image of the Mg + 1.7 In718 sample after predeformation ε<sub>pl</sub> = 0.02.</p> Full article ">Figure 13
<p>Concentration dependence of (<b>a</b>) the yield stress (TYS/CYS) and (<b>b</b>) the maximum/peak stress (MTS/CPS) estimated at room temperature.</p> Full article ">Figure 14
<p>Microhardness measured in two directions plotted against <span class="html-italic">d</span><sup>−1/2</sup>.</p> Full article ">Figure 15
<p>TYS and CYS plotted against <span class="html-italic">d</span><sup>−1/2</sup>. Experimental values are linked with the dash line, and corrected values are linked with the solid line.</p> Full article ">Figure 16
<p>Concentration dependence of the thermal expansion coefficient.</p> Full article ">
5 pages, 1763 KiB  
Editorial
Bioengineering Methods of Analysis and Medical Devices: A Current Trends and State of the Art
by Marco Cicciù
Materials 2020, 13(3), 797; https://doi.org/10.3390/ma13030797 - 10 Feb 2020
Cited by 14 | Viewed by 4832
Abstract
Implantology, prosthodontics, and orthodontics in all their variants, are medical and rehabilitative medical fields that have greatly benefited from bioengineering devices of investigation to improve the predictability of clinical rehabilitations. The finite element method involves the simulation of mechanical forces from an environment [...] Read more.
Implantology, prosthodontics, and orthodontics in all their variants, are medical and rehabilitative medical fields that have greatly benefited from bioengineering devices of investigation to improve the predictability of clinical rehabilitations. The finite element method involves the simulation of mechanical forces from an environment with infinite elements, to a simulation with finite elements. This editorial aims to point out all the progress made in the field of bioengineering and medicine. Instrumental investigations, such as finite element method (FEM), are an excellent tool that allows the evaluation of anatomical structures and any facilities for rehabilitation before moving on to experimentation on animals, so as to have mechanical characteristics and satisfactory load cycle testing. FEM analysis contributes substantially to the development of new technologies and new materials in the biomedical field. Thanks to the 3D technology and to the reconstructions of both the anatomical structures and eventually the alloplastic structures used in the rehabilitations it is possible to consider all the mechanical characteristics, so that they could be analyzed in detail and improved where necessary. Full article
(This article belongs to the Special Issue Dental Implants and Materials)
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<p>Mandibular von Mises analysis with all on four implant prosthetic rehabilitation.</p> Full article ">Figure 2
<p>Passant abutment screws von Mises analysis.</p> Full article ">Figure 3
<p>Mandibular finite element method (FEM) model.</p> Full article ">
25 pages, 45511 KiB  
Article
Numerical and Experimental Analysis of Material Removal and Surface Defect Mechanism in Scratch Tests of High Volume Fraction SiCp/Al Composites
by Xu Zhao, Yadong Gong, Ming Cai and Bing Han
Materials 2020, 13(3), 796; https://doi.org/10.3390/ma13030796 - 10 Feb 2020
Cited by 21 | Viewed by 3122
Abstract
This paper addresses a comprehensive and further insight into the sensitivity of material removal and the surface defect formation mechanism to scratch depth during single-grit scratch tests of 50 vol% SiCp/Al composites. The three-dimensional (3D) finite element model with more realistic 3D micro-structure, [...] Read more.
This paper addresses a comprehensive and further insight into the sensitivity of material removal and the surface defect formation mechanism to scratch depth during single-grit scratch tests of 50 vol% SiCp/Al composites. The three-dimensional (3D) finite element model with more realistic 3D micro-structure, particle-matrix interfacial behaviors, particle-particle contact behaviors, particle-matrix contact behaviors and a Johnson-Holmquist-Beissel (JHB) model of SiC was developed. The scratch simulation conducted at scratch velocity 10 mm/min and loading rate 40 N/min revealed that the scratch depth plays a crucial role in material removal and the surface forming process. Brittle fracturing of SiC particles and surface defects become more deteriorative under a large scratch depth ranging from 0.0385 to 0.0764 μm. The above phenomenon can be attributed to the influence of scratch depth on SiC particles’ transport; the increase in the amount of SiC particle transport resulting from an increase of scratch depth raises the occurrence of particle-particle collision which provides hard support and shock for the scratched particles; therefore, brittle fracturing gradually becomes the major removal mode of SiC particles as the scratch depth increases. On the deteriorative surface, various defects are observed; i.e., lateral cracks, interfacial debonding, cavies filled with residually broken particles, etc. The von Mises stress distribution shows that SiC particles bear vast majority of load, and thus present greater stress than the surrounding Al matrix. For example: their ratio of 3 to 30 under the scratch depth of 0.011 mm. Namely, SiC particles impede stress diffusion within the Al matrix. Finally, the SEM images of the scratched surface obtained from the single-grit scratch experiments verify the numerical analysis’s results. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
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<p>The microstructure of 50 vol% SiCp/5083Al.</p> Full article ">Figure 2
<p>Schematic diagram of the scratch process simulation.</p> Full article ">Figure 3
<p>3D structural model of SiC/Al of 100 × 100 × 100 μm<sup>3</sup>.</p> Full article ">Figure 4
<p>The meshing strategy for SiC particles and Al matrix: (<b>a</b>) SiC particles, (<b>b</b>) Al matrix.</p> Full article ">Figure 5
<p>Loads and boundary conditions.</p> Full article ">Figure 6
<p>Experimental method: (<b>a</b>) MFT-4000 Scratch Tester for Material Surface Properties; (<b>b</b>) schematic diagram of scratch with a linearly increasing down force.</p> Full article ">Figure 7
<p>Simulated initial scratch process at a depth of 0 to 0.011 mm: (<b>a</b>) scratch depth <span class="html-italic">h</span> = 0, (<b>b</b>) <span class="html-italic">h</span> = 1.01 × 10<sup>−5</sup> mm, (<b>c</b>) <span class="html-italic">h</span> = 3.96 × 10<sup>−3</sup> mm, (<b>d</b>) <span class="html-italic">h</span> = 5.77 × 10<sup>−3</sup> mm, (<b>e</b>) <span class="html-italic">h</span> = 8.43 × 10<sup>−3</sup> mm, (<b>f</b>) <span class="html-italic">h</span> = 0.011 mm.</p> Full article ">Figure 8
<p>Von Mises stress distribution of the initial scratch model sectioned along the scratch direction: (<b>a</b>) scratch depth <span class="html-italic">h</span> = 0, (<b>b</b>) <span class="html-italic">h</span> = 1.01 × 10<sup>−5</sup> mm, (<b>c</b>) <span class="html-italic">h</span> = 3.96 × 10<sup>−3</sup> mm, (<b>d</b>) <span class="html-italic">h</span> = 5.77 × 10<sup>−3</sup> mm, (<b>e</b>) <span class="html-italic">h</span> = 8.43 × 10<sup>−3</sup> mm, (<b>f</b>) <span class="html-italic">h</span> = 0.011 mm.</p> Full article ">Figure 8 Cont.
<p>Von Mises stress distribution of the initial scratch model sectioned along the scratch direction: (<b>a</b>) scratch depth <span class="html-italic">h</span> = 0, (<b>b</b>) <span class="html-italic">h</span> = 1.01 × 10<sup>−5</sup> mm, (<b>c</b>) <span class="html-italic">h</span> = 3.96 × 10<sup>−3</sup> mm, (<b>d</b>) <span class="html-italic">h</span> = 5.77 × 10<sup>−3</sup> mm, (<b>e</b>) <span class="html-italic">h</span> = 8.43 × 10<sup>−3</sup> mm, (<b>f</b>) <span class="html-italic">h</span> = 0.011 mm.</p> Full article ">Figure 9
<p>Von Mises stress distribution on the initial scratch model sectioned perpendicularly to the scratch direction: (<b>a</b>) Sectioning scheme, (<b>b</b>) <span class="html-italic">t</span> = 0.294 s, (<b>c</b>) <span class="html-italic">t</span> = 0.315 s, (<b>d</b>) <span class="html-italic">t</span> = 0.336 s, (<b>e</b>) <span class="html-italic">t</span> = 0.356 s, (<b>f</b>) <span class="html-italic">t</span> = 0.419 s.</p> Full article ">Figure 10
<p>The final state of SiC particles in the initial scratch model.</p> Full article ">Figure 11
<p>Simulated middle scratch process at a depth of 0.011 to 0.0385 mm: (<b>a</b>) <span class="html-italic">h</span> = 0.011 mm, (<b>b</b>) <span class="html-italic">h</span> = 0.0122 mm, (<b>c</b>) <span class="html-italic">h</span> = 0.0162 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.0212 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.0290 mm, (<b>f</b>) <span class="html-italic">h</span> = 0.0385 mm.</p> Full article ">Figure 12
<p>Von Mises stress distribution on the middle scratching model sectioned along the scratching direction: (<b>a</b>) <span class="html-italic">h</span> = 0.011 mm, (<b>b</b>) <span class="html-italic">h</span> = 0.0122 mm, (<b>c</b>) <span class="html-italic">h</span> = 0.0162 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.0212 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.0290 mm, (<b>f</b>) <span class="html-italic">h</span> = 0.0385 mm.</p> Full article ">Figure 13
<p>Von Mises stress distribution on the middle scratching model sectioned perpendicularly to the scratching direction: (<b>a</b>) sectioning scheme, (<b>b</b>) <span class="html-italic">t</span> = 0.157 s, (<b>c</b>) <span class="html-italic">t</span> = 0.209 s, (<b>d</b>) <span class="html-italic">t</span> = 0.235 s, (<b>e</b>) <span class="html-italic">t</span> = 0.261 s, (<b>f</b>) <span class="html-italic">t</span> = 0.365 s.</p> Full article ">Figure 13 Cont.
<p>Von Mises stress distribution on the middle scratching model sectioned perpendicularly to the scratching direction: (<b>a</b>) sectioning scheme, (<b>b</b>) <span class="html-italic">t</span> = 0.157 s, (<b>c</b>) <span class="html-italic">t</span> = 0.209 s, (<b>d</b>) <span class="html-italic">t</span> = 0.235 s, (<b>e</b>) <span class="html-italic">t</span> = 0.261 s, (<b>f</b>) <span class="html-italic">t</span> = 0.365 s.</p> Full article ">Figure 14
<p>The final state of SiC particles in the middle scratching model.</p> Full article ">Figure 15
<p>Simulated final scratching process at a depth of 0.0385 to 0.0764 mm: (<b>a</b>) <span class="html-italic">h</span> = 0.0385 mm, (<b>b</b>) <span class="html-italic">h</span> = 0.0442 mm, (<b>c</b>) <span class="html-italic">h</span> = 0.0476 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.0571 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.0654 mm, (<b>f</b>) <span class="html-italic">h</span> = 0.0764 mm.</p> Full article ">Figure 16
<p>Von Mises stress distribution on the middle scratching model sectioned along the scratching direction: (<b>a</b>) scratching depth <span class="html-italic">h</span> = 0.0385 mm, (<b>b</b>) <span class="html-italic">h</span> = 0.0442 mm, (<b>c</b>) <span class="html-italic">h</span> = 0.0476 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.0571 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.0654 mm, (<b>f</b>) <span class="html-italic">h</span> = 0.0764 mm.</p> Full article ">Figure 17
<p>Von Mises stress distribution on the final scratching model sectioned perpendicularly to the scratching direction: (<b>a</b>) sectioning scheme, (<b>b</b>) <span class="html-italic">t</span> = 0.445 s, (<b>c</b>) <span class="html-italic">t</span> = 0.594 s, (<b>d</b>) <span class="html-italic">t</span> = 0.693 s, (<b>e</b>) <span class="html-italic">t</span> = 0.842 s, (<b>f</b>) <span class="html-italic">t</span> = 0.941 s.</p> Full article ">Figure 17 Cont.
<p>Von Mises stress distribution on the final scratching model sectioned perpendicularly to the scratching direction: (<b>a</b>) sectioning scheme, (<b>b</b>) <span class="html-italic">t</span> = 0.445 s, (<b>c</b>) <span class="html-italic">t</span> = 0.594 s, (<b>d</b>) <span class="html-italic">t</span> = 0.693 s, (<b>e</b>) <span class="html-italic">t</span> = 0.842 s, (<b>f</b>) <span class="html-italic">t</span> = 0.941 s.</p> Full article ">Figure 18
<p>The final state of SiC particles in the final scratching model.</p> Full article ">Figure 19
<p>Forming process of the scratched groove topography during the initial scratching stage at a depth of 0 to 0.011 mm: (<b>a</b>) scratching depth <span class="html-italic">h</span> = 1 × 10<sup>−5</sup> mm, (<b>b</b>) <span class="html-italic">h</span> = 3.843 × 10<sup>−5</sup> mm, (<b>c</b>) <span class="html-italic">h</span> = 0.00246 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.00486 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.00702 mm, (<b>f</b>) <span class="html-italic">h</span> = 0.011 mm.</p> Full article ">Figure 19 Cont.
<p>Forming process of the scratched groove topography during the initial scratching stage at a depth of 0 to 0.011 mm: (<b>a</b>) scratching depth <span class="html-italic">h</span> = 1 × 10<sup>−5</sup> mm, (<b>b</b>) <span class="html-italic">h</span> = 3.843 × 10<sup>−5</sup> mm, (<b>c</b>) <span class="html-italic">h</span> = 0.00246 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.00486 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.00702 mm, (<b>f</b>) <span class="html-italic">h</span> = 0.011 mm.</p> Full article ">Figure 20
<p>Forming process of the scratched grooves topography during the middle scratching stage at a depth of 0.011 to 0.0385 mm: (<b>a</b>) scratching depth <span class="html-italic">h</span> = 0.0139 mm, (<b>b</b>) <span class="html-italic">h</span> = 0.0177 mm, (<b>c</b>) <span class="html-italic">h</span> = 0.0194 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.0254 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.03 mm, (<b>f</b>) <span class="html-italic">h</span> = 0.0385 mm.</p> Full article ">Figure 21
<p>Forming process of the scratched grooves topography during the final scratching stage at a depth of 0.0385 to 0.0764 mm: (<b>a</b>) scratch depth <span class="html-italic">h</span> = 0.0427 mm, (<b>b</b>) <span class="html-italic">h</span> = 0.0476 mm, (<b>c</b>) <span class="html-italic">h</span> = 0.0571 mm, (<b>d</b>) <span class="html-italic">h</span> = 0.0629 mm, (<b>e</b>) <span class="html-italic">h</span> = 0.0764 mm.</p> Full article ">Figure 22
<p>SEM images of the single single-grit scratched groove: (<b>a</b>) the overall surface topography, (<b>b</b>) the magnified view of the identified area on the initial scratching surface, (<b>c</b>) the magnified view of the identified area on the final scratching surface, (<b>d</b>) the magnified view of lateral cracks in (<b>c</b>) and (<b>e</b>) the magnified view of other defects in (<b>c</b>). I—the SiC particle which is marked with a red dot; II—small SiC fragments pushed ahead and pressed into the matrix; III—a cavity filled with residual particles; IV—fragmented particles remaining in the matrix.</p> Full article ">
14 pages, 4914 KiB  
Article
Degradation of Axial Ultimate Load-Bearing Capacity of Circular Thin-Walled Concrete-Filled Steel Tubular Stub Columns after Corrosion
by Fengjie Zhang, Junwu Xia, Guo Li, Zhen Guo, Hongfei Chang and Kejin Wang
Materials 2020, 13(3), 795; https://doi.org/10.3390/ma13030795 - 10 Feb 2020
Cited by 35 | Viewed by 4097
Abstract
This work aimed to investigate the effects of steel tube corrosion on the axial ultimate load-bearing capacity (AULC) of circular thin-walled concrete-filled steel tubular (CFST) members. Circular thin-walled CFST stub column specimens were made of steel tubes with various wall-thicknesses. These CFST column [...] Read more.
This work aimed to investigate the effects of steel tube corrosion on the axial ultimate load-bearing capacity (AULC) of circular thin-walled concrete-filled steel tubular (CFST) members. Circular thin-walled CFST stub column specimens were made of steel tubes with various wall-thicknesses. These CFST column specimens were subjected to an accelerated corrosion test, where the steel tubes were corroded to different degrees of corrosion. Then, these CFST specimens with corroded steel tubes experienced an axial static loading test. Results show that the failure patterns of circular thin-walled CFST stub columns with corroded steel tubes are different from those of the counterpart CFST columns with ordinary wall-thickness steel tubes, which is a typical failure mode of shear bulging with slight local outward buckling. The ultimate strength and plastic deformation capacity of the CFST specimens decreased with the increasing degree of steel corrosion. The failure modes of the specimens still belonged to ductile failure because of the confinement of outer steel tube. The degree of steel tube corrosion, diameter-to-thickness ratio, and confinement coefficient had substantial influences on the AULC and the ultimate compressive strength of circular thin-walled CFST stub columns. A simple AULC prediction model for corroded circular thin-walled CFST stub columns was presented through the regression of the experimental data and parameter analysis. Full article
(This article belongs to the Special Issue Concrete and Construction Materials)
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<p>Schematic of a circular thin-walled CFST stub column.</p> Full article ">Figure 2
<p>Schematic and photograph of accelerated corrosion on a CFST column. (<b>a</b>) The schematic; (<b>b</b>) a photograph.</p> Full article ">Figure 3
<p>Photo of test setup and data acquisition devices. (<b>a</b>) The specimen; (<b>b</b>) the data acquisition device.</p> Full article ">Figure 4
<p>Load vertical displacement behavior of CFST specimens with different corrosion ratios. (<b>a</b>) <span class="html-italic">t</span> = 0.92 mm; (<b>b</b>) <span class="html-italic">t</span> = 1.42 mm; (<b>c</b>) <span class="html-italic">t</span> = 1.92 mm.</p> Full article ">Figure 4 Cont.
<p>Load vertical displacement behavior of CFST specimens with different corrosion ratios. (<b>a</b>) <span class="html-italic">t</span> = 0.92 mm; (<b>b</b>) <span class="html-italic">t</span> = 1.42 mm; (<b>c</b>) <span class="html-italic">t</span> = 1.92 mm.</p> Full article ">Figure 5
<p>Photographs of CFST columns after failure. (<b>a</b>) CSC1-1; (<b>b</b>) CSC2-1; (<b>c</b>) CSC3-1; (<b>d</b>) CSC1-3; (<b>e</b>) CSC2-4; (<b>f</b>) CSC3-2.</p> Full article ">Figure 6
<p>Typical photographs of the core concrete after failure. (<b>a</b>) CSC1-3; (<b>b</b>) CSC2-2; (<b>c</b>) CSC2-4; (<b>d</b>) CSC3-2.</p> Full article ">Figure 7
<p>Relationship between specimens’ relative axial ultimate load-bearing capacity (AULC) and steel tube corrosion ratios.</p> Full article ">Figure 8
<p>Relationship between specimens’ ultimate compressive strength and diameter/thickness ratios.</p> Full article ">Figure 9
<p>Relationship between specimens’ ultimate compressive strength and confinement factors.</p> Full article ">
10 pages, 2701 KiB  
Communication
In-Situ Helium Implantation and TEM Investigation of Radiation Tolerance to Helium Bubble Damage in Equiaxed Nanocrystalline Tungsten and Ultrafine Tungsten-TiC Alloy
by Osman El Atwani, Kaan Unal, William Streit Cunningham, Saryu Fensin, Jonathan Hinks, Graeme Greaves and Stuart Maloy
Materials 2020, 13(3), 794; https://doi.org/10.3390/ma13030794 - 10 Feb 2020
Cited by 14 | Viewed by 3316
Abstract
The use of ultrafine and nanocrystalline materials is a proposed pathway to mitigate irradiation damage in nuclear fusion components. Here, we examine the radiation tolerance of helium bubble formation in 85 nm (average grain size) nanocrystalline-equiaxed-grained tungsten and an ultrafine tungsten-TiC alloy under [...] Read more.
The use of ultrafine and nanocrystalline materials is a proposed pathway to mitigate irradiation damage in nuclear fusion components. Here, we examine the radiation tolerance of helium bubble formation in 85 nm (average grain size) nanocrystalline-equiaxed-grained tungsten and an ultrafine tungsten-TiC alloy under extreme low energy helium implantation at 1223 K via in-situ transmission electron microscope (TEM). Helium bubble damage evolution in terms of number density, size, and total volume contribution to grain matrices has been determined as a function of He+ implantation fluence. The outputs were compared to previously published results on severe plastically deformed (SPD) tungsten implanted under the same conditions. Large helium bubbles were formed on the grain boundaries and helium bubble damage evolution profiles are shown to differ among the different materials with less overall damage in the nanocrystalline tungsten. Compared to previous works, the results in this work indicate that the nanocrystalline tungsten should possess a fuzz formation threshold more than one order of magnitude higher than coarse-grained tungsten. Full article
(This article belongs to the Special Issue Radiation Damage in Materials: Helium Effects)
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<p>A schematic showing the sample shape, implanted He (red curve), and displacement per atom (dpa) damage (blue curve) distributions of 2 keV He<sup>+</sup> (as determined by SRIM). The thickness of the sample is magnified for the purpose of overlapping the implanted He and displacement damage distributions. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)</p> Full article ">Figure 2
<p>(<b>a</b>–<b>h</b>): Bright-field TEM micrographs of a small implanted region taken under Fresnel conditions (under-focused) showing He bubble formation and evolution as a function of He<sup>+</sup> fluence in the grain matrices and grain boundaries in equiaxial nanocrystalline tungsten (NCW) with an average grainsize of 85 nm implanted in-situ with 2 keV He<sup>+</sup> at 1223 K. Scale bar of (<b>b</b>–<b>h</b>) is the same and is shown in (<b>b</b>). Red box in (<b>a</b>) approximately represents a magnified region presented in (<b>b</b>) to (<b>h</b>).</p> Full article ">Figure 3
<p>(<b>a</b>–<b>h</b>): Bright-field TEM micrographs of a small implanted region taken under Fresnel conditions (under-focused) showing He bubble formation and evolution as a function of He<sup>+</sup> fluence in the grain matrices and grain boundaries in W-TiC (1.1%) implanted in-situ with 2 keV He<sup>+</sup> at 1223 K. Scale bar of (<b>b</b>–<b>h</b>) is the same and is shown in (<b>b</b>). Red box in (<b>a</b>) approximately represents a magnified region presented in (<b>b</b>) to (<b>h</b>).</p> Full article ">Figure 4
<p>(Color online) Helium bubble density, average area, and the total change in volume in the grain matrices of (<b>a</b>) W-TiC and (<b>b</b>) NCW as a function of He<sup>+</sup> implantation fluence. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)</p> Full article ">Figure 5
<p>(Color online) normalized bar graphs of bubble size distributions in the grain matrices in (<b>a</b>) NCW and (<b>b</b>) W-TiC as a function of implantation He<sup>+</sup> fluence. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)</p> Full article ">
13 pages, 4444 KiB  
Article
Heavy Metals Removing from Municipal Solid Waste Incineration Fly Ashes by Electric Field-Enhanced Washing
by Yang Tian, Rong Wang, Zhenggang Luo, Rui Wang, Feihua Yang, Zhaojia Wang, Jiancheng Shu and Mengjun Chen
Materials 2020, 13(3), 793; https://doi.org/10.3390/ma13030793 - 10 Feb 2020
Cited by 16 | Viewed by 3302
Abstract
Municipal solid waste incineration (MSWI) fly ash contains chlorides, heavy metals, and organic pollutants, which requires appropriate disposal to eliminate this risk. In this study, the effects of agents on heavy metals removal from MSWI fly ash by electric field-enhanced washing were systematically [...] Read more.
Municipal solid waste incineration (MSWI) fly ash contains chlorides, heavy metals, and organic pollutants, which requires appropriate disposal to eliminate this risk. In this study, the effects of agents on heavy metals removal from MSWI fly ash by electric field-enhanced washing were systematically studied. The results show that when these fly ashes were washed at a current density of 35 mA/cm2, polarity switching frequency of 40 Hz, Ethylenediaminetetraacetic acid (EDTA) dosage of 0.5 mol/L, and a pH of 2 for 4 h, almost all of the Cd and Ni could be were removed, with a removal efficiency of 100.00% and 99.59%, respectively. Meanwhile, it also shows a significant effect on Cu and Zn, with a removal efficiency higher than 85%. After washing, the results of the sequential extraction procedure showed that the residual forms of Pb, Cu, Zn, Cd, Ni, and As increased obviously. According to GB5085.3-2007, the toxicity of the treated MSWI fly ash were below their thresholds of 5 and 1 mg/L for Pb and Cd, respectively. Thus, a novel technology for heavy metals removal from MSWI fly ash is proposed. Full article
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<p>The experimental apparatus of enhanced extracted by electric field.</p> Full article ">Figure 2
<p>XRD patterns (<b>a</b>) and SEM images (<b>b</b>) of MSWI fly ash.</p> Full article ">Figure 3
<p>Heavy metal forms of MSWI fly ash.</p> Full article ">Figure 4
<p>Effect of pH on heavy metals efficiency (0.5 mol/L EDTA, 25 mA/cm<sup>2</sup>, 4 h, 0 Hz).</p> Full article ">Figure 5
<p>Effect of current density on heavy metals efficiency (0.5 mol/L EDTA, pH = 2, 4 h, 0 Hz).</p> Full article ">Figure 6
<p>Effect of extraction time on heavy metals efficiency (0.5 mol/L EDTA, 35 mA/cm<sup>2</sup>, pH = 2, 0 Hz).</p> Full article ">Figure 7
<p>Effect of periodically switched polarity on heavy metals efficiency (0.5 mol/L EDTA, 35 mA/cm<sup>2</sup>, pH = 2, 2 h).</p> Full article ">Figure 8
<p>Composition changes in the extracting solution at different extraction times (mol/L).</p> Full article ">Figure 9
<p>XRD patterns (<b>a</b>) and SEM images (<b>b</b>) and (<b>c</b>) of treated MSWI fly ash.</p> Full article ">Figure 10
<p>Heavy metal forms of treated MSWI fly ash.</p> Full article ">Figure 11
<p>Electric field intensifies heavy metal in MSWI fly ash removal process.</p> Full article ">
13 pages, 5573 KiB  
Article
Damping Property of Cement Mortar Incorporating Damping Aggregate
by Yaogang Tian, Dong Lu, Jianwei Zhou, Yuxuan Yang and Zhenjun Wang
Materials 2020, 13(3), 792; https://doi.org/10.3390/ma13030792 - 9 Feb 2020
Cited by 14 | Viewed by 3147
Abstract
This study proposes a new cement mortar incorporating damping aggregate (DA) and investigates the mechanical properties and damping property of the cement mortar. Four types of DA were prepared, lightweight aggregate presaturated water and three types of polymer emulsion. Further, the effects of [...] Read more.
This study proposes a new cement mortar incorporating damping aggregate (DA) and investigates the mechanical properties and damping property of the cement mortar. Four types of DA were prepared, lightweight aggregate presaturated water and three types of polymer emulsion. Further, the effects of polypropylene fiber and rubber powder on the performance of the cement mortar were studied. The experimental results showed that the damping ratio of specimens containing 70% DA was approximately three times higher than that of the reference mortar, with a slight decrease in the mechanical properties. Adding fiber was more effective than rubber powder in improving the damping ratio of the cement mortar, and the optimal dosage of fiber was 0.5%. Full article
(This article belongs to the Section Construction and Building Materials)
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<p>Particle gradation of aggregate.</p> Full article ">Figure 2
<p>Flow chart of damping aggregate preparation.</p> Full article ">Figure 3
<p>Damping aggregate used in this study.</p> Full article ">Figure 4
<p>Schematic of the experimental setting and specimen dimension for the free vibration test.</p> Full article ">Figure 5
<p>Acceleration response signals as time-magnitude.</p> Full article ">Figure 6
<p>The half-power bandwidth method for the estimation of the damping ratio of the cement mortar.</p> Full article ">Figure 7
<p>Compressive strength of cement mortar: (<b>a</b>) aggregate type; (<b>b</b>) replacement percentage of DA; (<b>c</b>) fiber content, and (<b>d</b>) rubber powder content.</p> Full article ">Figure 8
<p>Flexural strength of the cement mortar: (<b>a</b>) aggregate type; (<b>b</b>) replacement percentage of DA; (<b>c</b>) fiber content, and (<b>d</b>) rubber powder content.</p> Full article ">Figure 8 Cont.
<p>Flexural strength of the cement mortar: (<b>a</b>) aggregate type; (<b>b</b>) replacement percentage of DA; (<b>c</b>) fiber content, and (<b>d</b>) rubber powder content.</p> Full article ">Figure 9
<p>Damping ratio of the cement mortar: (<b>a</b>) aggregate type; (<b>b</b>) replacement percentage of DA; (<b>c</b>) fiber content, and (<b>d</b>) rubber powder content.</p> Full article ">Figure 9 Cont.
<p>Damping ratio of the cement mortar: (<b>a</b>) aggregate type; (<b>b</b>) replacement percentage of DA; (<b>c</b>) fiber content, and (<b>d</b>) rubber powder content.</p> Full article ">Figure 10
<p>Secondary Electron images of damping aggregate: (<b>a</b>) lightweight aggregate and (<b>b</b>) lightweight aggregate presaturated with polymer.</p> Full article ">Figure 11
<p>Damping structure among the DA, polymer emulsion, and hydration products of the cement in mortar.</p> Full article ">
12 pages, 3817 KiB  
Article
Influence of O2 on the Erosion-Corrosion Performance of 3Cr Steels in CO2 Containing Environment
by Lei Xia, Yan Li, Leilei Ma, Hongmei Zhang, Na Li and Zhengyi Jiang
Materials 2020, 13(3), 791; https://doi.org/10.3390/ma13030791 - 9 Feb 2020
Cited by 12 | Viewed by 2595
Abstract
With the introduction of O2 during oil and gas production, the erosion-corrosion rate of tubing steels increases; the objective of this report is to explore the reason for this. Erosion–corrosion experiments were performed in environments of CO2 and CO2–O [...] Read more.
With the introduction of O2 during oil and gas production, the erosion-corrosion rate of tubing steels increases; the objective of this report is to explore the reason for this. Erosion–corrosion experiments were performed in environments of CO2 and CO2–O2, respectively. Macrographs, microstructures, and the compositions of erosion-corrosion scales were investigated using a digital camera, scanning electron microscope (SEM), Kevex-SuperDry energy spectrometer (EDS) and X-ray diffraction (XRD). The results show that the erosion-corrosion products are composed of large FeCO3 particles and some amorphous product in the CO2 environment, while they are made up of FeCO3, Fe2O3, Fe3O4, and bits of amorphous product in the CO2–O2 environment. The interface between erosion-corrosion scales and the substrate of 3Cr steel is smooth, and Cr enrichment obviously exists in the erosion-corrosion products in the CO2 condition. However, the erosion-corrosion scale is loose and porous with little Cr enrichment in the CO2–O2 environment, which makes the protectiveness of the erosion–corrosion scale weak, and pitting corrosion occurs. The addition of O2 may destroy the protective FeCO3 scale and Cr enrichment in the erosion-corrosion scale, which may be the main reason for the decline in the level of protectiveness of the erosion-corrosion scale, making it weak in terms of preventing the corrosive medium from diffusing to the substrate. Full article
(This article belongs to the Section Corrosion)
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<p>Schematic diagram of the HTHPE.</p> Full article ">Figure 2
<p>The shape and size of specimen (<b>a</b>) side view; (<b>b</b>) top view.</p> Full article ">Figure 3
<p>Microstructure of 3Cr steel.</p> Full article ">Figure 4
<p>Average erosion-corrosion rate of 3Cr steel.</p> Full article ">Figure 5
<p>Macrostructure of erosion-corrosion products and substrates after removal erosion-corrosion products under different conditions (<b>a</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, erosion-corrosion product, (<b>b</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, substrate, (<b>c</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.2 MPa, erosion-corrosion product, (<b>d</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.2 MPa, substrate, (<b>e</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.4 MPa, erosion-corrosion product, (<b>f</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.4 MPa, substrate, (<b>g</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.6 MPa, erosion-corrosion product, (<b>h</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.6 MPa, substrate.</p> Full article ">Figure 6
<p>SEM and elemental analysis of erosion-corrosion products in CO<sub>2</sub> and CO<sub>2</sub>–O<sub>2</sub> environments (<b>a</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, surface morphology, (<b>b</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, elemental analysis, (<b>c</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.6 MPa, surface morphology, (d) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.6 MPa, elemental analysis.</p> Full article ">Figure 7
<p>XRD analysis of erosion-corrosion products of 3Cr steel under different conditions (<b>a</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, (<b>b</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.2 MPa, (<b>c</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.4 MPa, (<b>d</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, P<sub>O</sub><sub>2</sub>: 0.6 MPa.</p> Full article ">Figure 8
<p>Cross-section morphologies and Cr elements concentration of erosion-corrosion product (<b>a</b>) P<sub>CO</sub><sub>2</sub>: 2.5 MPa, Cross-section morphology, (<b>b</b>) P<sub>CO2</sub>: 2.5 MPa, Cr element concentration, (<b>c</b>) P<sub>CO2</sub>: 2.5 MPa, P<sub>O2</sub>: 0.6 MPa, Cross-section morphology, (<b>d</b>) P<sub>CO2</sub>: 2.5 MPa, P<sub>O2</sub>: 0.6 MPa, Cr element concentration.</p> Full article ">
18 pages, 6273 KiB  
Article
Recycling of Cigarette Butts in Fired Clay Bricks: A New Laboratory Investigation
by Halenur Kurmus and Abbas Mohajerani
Materials 2020, 13(3), 790; https://doi.org/10.3390/ma13030790 - 9 Feb 2020
Cited by 33 | Viewed by 11708
Abstract
Cigarette butts (CBs) are the most commonly littered waste material in the world. It is estimated that over 5.7 trillion cigarettes are consumed worldwide each year. Consequently, millions of tonnes of highly toxic waste are contaminating the environment. CBs are composed of cellulose [...] Read more.
Cigarette butts (CBs) are the most commonly littered waste material in the world. It is estimated that over 5.7 trillion cigarettes are consumed worldwide each year. Consequently, millions of tonnes of highly toxic waste are contaminating the environment. CBs are composed of cellulose acetate filters—a polymer with poor biodegradability—and which, depending upon the environmental conditions, can take many years to decompose. In this study, fired clay bricks were manufactured with 0.5%, 1%, 1.5%, and 2% CBs by mass and tested against control bricks with 0% CBs. The results revealed a decrease in compressive strength from 48.6 MPa for 0% CB content bricks to 30.8 MPa for 1% CB content bricks, and a decrease in dry density with the increase in CB content, from 2114 kg/m3 for the control bricks to 1983 kg/m3 and 1969 kg/m3 for 1% and 2% CB content bricks. The highest value of water absorption appeared for 2% CB content bricks, which reached an absorption rate of 13.1% compared to 9% for the control bricks. The energy required during the firing process was calculated with a saving of up to 10.20%, for bricks incorporating 1% CBs. The thermal conductivity of the samples showed a reduction of 17% from 1.078 to 0.898 W m−1·K−1 with the addition of 1% CBs. In addition, the manufactured bricks were tested for efflorescence, an initial rate of absorption (IRA), microstructural analysis, and shrinkage. A life-cycle assessment (LCA) is recommended to analyze the environmental impacts of bricks incorporating CBs. Full article
(This article belongs to the Special Issue Novel Sustainable Technologies for Recycling Waste Materials)
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<p>Littered CBs.</p> Full article ">Figure 2
<p>CBs used in this study.</p> Full article ">Figure 3
<p>Particle-size distribution curve of brick soil used in this study.</p> Full article ">Figure 4
<p>XRD patterns of brick soil.</p> Full article ">Figure 5
<p>TG and DTA curves of 0% CB content clay mixture and 1% CB content clay mixture.</p> Full article ">Figure 6
<p>Some of the samples prepared in this study.</p> Full article ">Figure 7
<p>Height shrinkage versus CB percentage by mass.</p> Full article ">Figure 8
<p>Diametric shrinkage versus CB percentage by mass.</p> Full article ">Figure 9
<p>Dry density versus CB percentage by mass.</p> Full article ">Figure 10
<p>Compressive strength versus CB percentage by mass.</p> Full article ">Figure 11
<p>Water absorption versus CB percentage by mass.</p> Full article ">Figure 12
<p>IRA versus CB percentage by mass.</p> Full article ">Figure 13
<p>24-hour cold water and 5-hour boiling water test.</p> Full article ">Figure 14
<p>Efflorescence on bricks for mixes with 0%, 0.5%, 1.0%, 1.5%, and 2.0% CBs.</p> Full article ">Figure 15
<p>X-ray CT images of 0% (left) and 1% (right) CB content clay bricks.</p> Full article ">Figure 16
<p>Energy saving versus CB percentage by mass.</p> Full article ">Figure 17
<p>Thermal conductivity of each brick sample.</p> Full article ">Figure 18
<p>Fired clay brick wall.</p> Full article ">
13 pages, 7731 KiB  
Article
Microstructure and Fracture Behavior of Special Multilayered Steel
by Xin Zhou, XiaoKang Zhao, Rui Cao, RuiHua Zhang, Yun Ding and XiaoBo Zhang
Materials 2020, 13(3), 789; https://doi.org/10.3390/ma13030789 - 9 Feb 2020
Cited by 1 | Viewed by 2988
Abstract
In this research, multilayered steel (MLS), which is composed of middle-carbon martensite steel, high-carbon martensite steel, and a pure Ni thin layer was obtained by the accumulative roll-bonding method. The microstructure and mechanical properties of the MLS were investigated by scanning electron microscopy [...] Read more.
In this research, multilayered steel (MLS), which is composed of middle-carbon martensite steel, high-carbon martensite steel, and a pure Ni thin layer was obtained by the accumulative roll-bonding method. The microstructure and mechanical properties of the MLS were investigated by scanning electron microscopy (SEM), Vickers microhardness, tensile, and bending tests. In-situ SEM tensile tests were used to observe the crack initiation and propagation processes during the tensile loading. The results show that the ultimate tensile strength and bending strength of the MLS can reach 946 MPa and 3153 MPa, and the maximum elongation can reach 18%, which is related to the better combined quality of the interface. The middle and larger martensite layer (ML) becomes the weakest link of tensile fracture and interfacial delamination of the MLS during the tensile processes, because there are lots of large hard blocks Cr23C6 phases distributed in the middle thicker ML layer. Besides, the MLS can withstand larger bending deformation. When the MLS was bent to 180 degrees, neither macro-cracks in the outer side of the bending parts nor interfacial delamination can be found. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic of as-received multilayered steel.</p> Full article ">Figure 2
<p>The size of the specimens involved in the experiment (dimensions in mm). (<b>a</b>) Dimensions of tensile specimens, (<b>b</b>) Dimensions of bending specimens, (<b>c</b>) Dimensions of in-situ tensile specimens, (<b>d</b>) macro figure of in-situ tensile specimens.</p> Full article ">Figure 3
<p>Microstructure and line scanning results of multilayered steel. (<b>a</b>) macro-feature of the MLS, (<b>b</b>)the magnification of ML in <a href="#materials-13-00789-f003" class="html-fig">Figure 3</a>a, (<b>c</b>) the magnification of the composite layer at two sides in <a href="#materials-13-00789-f003" class="html-fig">Figure 3</a>a, (<b>d</b>) line scanning distribution location, (<b>e</b>) line scanning result along the black line OA in <a href="#materials-13-00789-f003" class="html-fig">Figure 3</a>d, (<b>f</b>) EBSD phase analysis, (<b>g</b>) the misorientation distribution obtained by EBSD.</p> Full article ">Figure 4
<p>Engineering stress–strain curve of a multilayered steel (MLS) tensile specimen.</p> Full article ">Figure 5
<p>Fracture surface of MLS tensile specimen. (<b>a</b>) the macro-fracture surface, (<b>b</b>) the magnification of ML in <a href="#materials-13-00789-f005" class="html-fig">Figure 5</a>a, (<b>c</b>) the magnification of the interfaces of the ML and Ni layer and the ML<sub>1</sub> and Ni layer in <a href="#materials-13-00789-f005" class="html-fig">Figure 5</a>a, (<b>d</b>) the magnification of the interfaces between the ML<sub>1</sub> layer and the Ni layer in two sides of MLS.</p> Full article ">Figure 5 Cont.
<p>Fracture surface of MLS tensile specimen. (<b>a</b>) the macro-fracture surface, (<b>b</b>) the magnification of ML in <a href="#materials-13-00789-f005" class="html-fig">Figure 5</a>a, (<b>c</b>) the magnification of the interfaces of the ML and Ni layer and the ML<sub>1</sub> and Ni layer in <a href="#materials-13-00789-f005" class="html-fig">Figure 5</a>a, (<b>d</b>) the magnification of the interfaces between the ML<sub>1</sub> layer and the Ni layer in two sides of MLS.</p> Full article ">Figure 6
<p>Macro-feature and SEM morphology of the bending specimen after bending to 136 degrees. (<b>a</b>) Macroscopic bending morphology, (<b>b</b>–<b>d</b>) SEM bending features.</p> Full article ">Figure 6 Cont.
<p>Macro-feature and SEM morphology of the bending specimen after bending to 136 degrees. (<b>a</b>) Macroscopic bending morphology, (<b>b</b>–<b>d</b>) SEM bending features.</p> Full article ">Figure 7
<p>Macro-feature and SEM morphology of the bending specimen after bending to 180 degrees. (<b>a</b>) Macroscopic bending morphology, (<b>b</b>–<b>g</b>) SEM bending features.</p> Full article ">Figure 8
<p>SEM features and cracking of carbides observed at various tensile elongations, (<b>a</b>) 0, (<b>b</b>) 16.9%, (<b>c</b>) 17.3%, (<b>d</b>) 17.8%, (<b>e</b>,<b>f</b>) 18.2%.</p> Full article ">Figure 9
<p>Deformation of the Ni layer observed at various tensile elongations, (<b>a</b>) 17.8%, (<b>b</b>,<b>c</b>) 18.2%.</p> Full article ">Figure 10
<p>Fracture surfaces of multilayered steel (MLS) in-situ tensile specimen (<b>a</b>) one fracture surface, (<b>b</b>) matched fracture surface.</p> Full article ">
12 pages, 8292 KiB  
Article
Micro-Texture Analyses of a Cold-Work Tool Steel for Additive Manufacturing
by Jun-Yun Kang, Jaecheol Yun, Byunghwan Kim, Jungho Choe, Sangsun Yang, Seong-Jun Park, Ji-Hun Yu and Yong-Jin Kim
Materials 2020, 13(3), 788; https://doi.org/10.3390/ma13030788 - 9 Feb 2020
Cited by 2 | Viewed by 3130
Abstract
Small objects of an alloy tool steel were built by selective laser melting at different scan speeds, and their microstructures were analyzed using electron backscatter diffraction (EBSD). To present an explicit correlation with the local thermal cycles in the objects, prior austenite grains [...] Read more.
Small objects of an alloy tool steel were built by selective laser melting at different scan speeds, and their microstructures were analyzed using electron backscatter diffraction (EBSD). To present an explicit correlation with the local thermal cycles in the objects, prior austenite grains were reconstructed using the EBSD mapping data. Extensive growth of austenitic grains after solidification could be detected by the disagreement between the networks of carbides and austenite grain boundaries. A rapid laser scan at 2000 mm/s led to less growth, but retained a larger amount of austenite than a slow one at 50 mm/s. The rapid scan also exhibited definite evolution of Goss-type textures in austenite, which could be attributed to the growth of austenitic grains under a steep temperature gradient. The local variations in the microstructures and the textures enabled us to speculate the locally different thermal cycles determined by the different process conditions, that is, scan speeds. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metals and Alloys)
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<p>Additive manufacturing (AM) object by the selective laser melting process (SD: scan direction, BD: build direction, the scan pattern is indicated with the alternate arrows) [<a href="#B22-materials-13-00788" class="html-bibr">22</a>] and its cross-sectional specimen for the microanalyses with the indicated sampled regions.</p> Full article ">Figure 2
<p>Microstructure of the powder: (<b>a</b>) image from forward scatter detectors (FSDs); and (<b>b</b>) phase map by the different phase colors, (<b>c</b>) original and (<b>d</b>) reconstructed inverse pole figure (IPF) map referred to the normal of the observation surface (Refer to the given color key for a cubic crystal. Grain boundaries were drawn for misorientation angle &gt;5° and the twin boundaries were defined by the misorientaions of 60°//&lt;111&gt; within 5° tolerance).</p> Full article ">Figure 3
<p>Representative microstructure on the mid-layers of the AM object built at 50 mm/s (C50): (<b>a</b>) FSD image, (<b>b</b>) phase map, and (<b>c</b>) original and (<b>d</b>) reconstructed IPF map referred to BD (The phase colors, the IPF color key, and the convention for boundary drawing followed those in <a href="#materials-13-00788-f002" class="html-fig">Figure 2</a>. The carbides in (<b>b</b>) and the twin boundaries in (<b>d</b>) were removed for cleanliness).</p> Full article ">Figure 4
<p>Representative microstructure on the mid-layers of the AM object built at 2000 mm/s (C2k): (<b>a</b>) FSD image, (<b>b</b>) phase map, and (<b>c</b>) original and (<b>d</b>) reconstructed BD-IPF map (The phase colors, the IPF color key, and the convention for boundary drawing followed those in <a href="#materials-13-00788-f002" class="html-fig">Figure 2</a>. The carbides in (<b>b</b>) and the twin boundaries in (<b>d</b>) were removed for cleanliness).</p> Full article ">Figure 5
<p>Representative microstructures on the different sampled regions in the AM objects: (<b>a</b>,<b>b</b>), (<b>e</b>,<b>f</b>), and (<b>i</b>,<b>j</b>) phase maps; (<b>c</b>,<b>d</b>), (<b>g</b>,<b>h</b>), and (<b>k</b>,<b>l</b>) reconstructed BD-IPF maps (Refer to the left and the upper parts of the figure for the information on the regions and the process conditions. The phase colors, the IPF color key, and the convention for boundary drawing followed those in <a href="#materials-13-00788-f002" class="html-fig">Figure 2</a>. The carbides in (<b>b</b>) and the twin boundaries in (<b>d</b>) were removed for cleanliness).</p> Full article ">Figure 6
<p>Average fraction of retained austenite according to the regions and the scan speeds of the AM objects (the error bars and the broken horizontal lines represent the standard errors and the average values for the whole sampled regions, respectively).</p> Full article ">Figure 7
<p>Average sizes of the prior austenite grains according to the regions and the scan speeds of the AM objects: (<b>a</b>) for all the detected grains, and (<b>b</b>) the grains of diameter &gt;5 and (<b>c</b>) &gt;10 μm only (the error bars and the broken horizontal lines represent the standard errors and the average values for the whole sampled regions, respectively).</p> Full article ">Figure 8
<p>Orientation distribution functions (ODFs) on the φ<sub>2</sub> = 45° section of the Euler space (Bunge’s convention) according to the regions and the scan speeds of the AM objects (Refer to the left and the upper parts of the figure for the information on the regions and the speeds. The sample reference axes 1 and 3 correspond to SD and BD, respectively): (<b>a</b>–<b>d</b>) ODFs of the lower, the mid-, the upper layers and all the sampled regions of C50 respectively, (<b>e</b>–<b>h</b>) ODFs of the lower, the mid-, the upper layers and all the sampled regions of C2k respectively</p> Full article ">
11 pages, 1270 KiB  
Article
Color Stability and Micro-Hardness of Bulk-Fill Composite Materials after Exposure to Common Beverages
by Nora Bahbishi, Waad Mzain, Bayan Badeeb and Hani M. Nassar
Materials 2020, 13(3), 787; https://doi.org/10.3390/ma13030787 - 9 Feb 2020
Cited by 45 | Viewed by 5174
Abstract
Objectives: To assess the color stability and surface microhardness of Bulk-Fill composite materials available in the Saudi Arabia market. Methods: Five composite materials (Filtek Z350, Filtek Bulk-Fill, Tetric N-Ceram Bulk-Fill, Sonic Fill 2, and SDR) were investigated. Samples (n = 20; 10 [...] Read more.
Objectives: To assess the color stability and surface microhardness of Bulk-Fill composite materials available in the Saudi Arabia market. Methods: Five composite materials (Filtek Z350, Filtek Bulk-Fill, Tetric N-Ceram Bulk-Fill, Sonic Fill 2, and SDR) were investigated. Samples (n = 20; 10 mm in diameter and 2 mm in thickness) were fabricated using a stainless-steel mold and were immersed in tea, coffee, berry juice, and distilled water (control). Baseline (T0) shades of specimens were recorded using a spectrophotometer and after 10 (T1), 30 (T2), 60 (T3), and 90 days (T4) of immersion. Measurements were obtained against a black background and CIE L*a*b* data was used to calculate ΔE for each group. Vickers microhardness values were obtained at T0 and T4. Data was analyzed using mixed model repeated measure ANOVA at 0.05 significance level. Results: Time, material, and solution effects have statistically significant effect on ΔE. Tea was the most staining solution. Z350 was associated with the highest ΔE values while SDR showed the lowest values. No other materials showed significant difference between each other. Solutions were statistically different from each other. All materials were different from each other regarding microhardness. Conclusion: Bulk-Fill materials showed more color stability but lower microhardness values compared to universal resin control. Full article
(This article belongs to the Section Biomaterials)
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<p>Photographs of specimens from each group of the study at baseline and after 90 days of immersion in the staining solutions.</p> Full article ">Figure 2
<p>Line graphs showing ΔE values for the five tested materials after immersion in different solutions for 10, 30, 60, and 90 days: (<b>a</b>) Filtek Z350, (<b>b</b>) Filtek Bulk-Fill, (<b>c</b>) Tetric N-Ceram Bulk-Fill, (<b>d</b>) Sonic Fill 2, and (<b>e</b>) SDR. Error bars represent standard error.</p> Full article ">Figure 2 Cont.
<p>Line graphs showing ΔE values for the five tested materials after immersion in different solutions for 10, 30, 60, and 90 days: (<b>a</b>) Filtek Z350, (<b>b</b>) Filtek Bulk-Fill, (<b>c</b>) Tetric N-Ceram Bulk-Fill, (<b>d</b>) Sonic Fill 2, and (<b>e</b>) SDR. Error bars represent standard error.</p> Full article ">Figure 3
<p>Bar graph showing ΔE values after 90 days of immersion in different solutions. Error bars represent standard error.</p> Full article ">Figure 4
<p>Changes in the CIE Lab parameters for the 5 tested materials after 90 days of immersion in tea solution. (1) Filtek Z350, (2) Filtek Bulk-Fill, (3) Tetric N-Ceram Bulk-Fill, (4) Sonic Fill 2, and (5) SDR. ΔE: overall shade change, ΔL: changes in lightness and darkness, Δa: changes in the red-green axis, Δb: changes in the blue-yellow axis. Please note different scales used for each parameter.</p> Full article ">
16 pages, 1160 KiB  
Review
Selection of Collagen Membranes for Bone Regeneration: A Literature Review
by Luca Sbricoli, Riccardo Guazzo, Marco Annunziata, Luca Gobbato, Eriberto Bressan and Livia Nastri
Materials 2020, 13(3), 786; https://doi.org/10.3390/ma13030786 - 9 Feb 2020
Cited by 159 | Viewed by 11626
Abstract
Several treatment modalities have been proposed to regenerate bone, including guided bone regeneration (GBR) where barrier membranes play an important role by isolating soft tissue and allowing bone to grow. Not all membranes biologically behave the same way, as they differ from their [...] Read more.
Several treatment modalities have been proposed to regenerate bone, including guided bone regeneration (GBR) where barrier membranes play an important role by isolating soft tissue and allowing bone to grow. Not all membranes biologically behave the same way, as they differ from their origin and structure, with reflections on their mechanical properties and on their clinical performance. Collagen membranes have been widely used in medicine and dentistry, because of their high biocompatibility and capability of promoting wound healing. Recently, collagen membranes have been applied in guided bone regeneration with comparable outcomes to non-resorbable membranes. Aim of this work is to provide a review on the main features, application, outcomes, and clinical employment of the different types of collagen membranes. Comparisons with non-resorbable membranes are clarified, characteristics of cross-linked collagen versus native collagen, use of different grafting materials and need for membrane fixation are explored in order to gain awareness of the indications and limits and to be able to choose the right membrane required by the clinical condition. Full article
(This article belongs to the Special Issue Biomaterials and Biological Mediators for Periodontal and Bone Regeneration)
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<p>Publications by year on non-resorbable membranes, collagen membranes, and cross-linked membranes (data from PubMed Library). The chart clearly shows the increase of publications toward collagen membranes.</p> Full article ">Figure 2
<p>Forest plot illustrating the results in terms of defect height reduction from the meta-analysis of all trials with a non-resorbable expanded polytetrafluorethylene membrane in combination with any bone substitute (ePTFE + BS) as a control. CM: collagen membrane. (From Thoma, DS, Bienz, SP, Figuero, E, Jung, RE, Sanz-Martín, I. Efficacy of lateral bone augmentation performed simultaneously with dental implant placement: A systematic review and meta-analysis. <span class="html-italic">J Clin Periodontol</span>. 2019; 46(Suppl. 21): 257–276. With permission).</p> Full article ">Figure 3
<p>Analysis and forest plot for the results of the included studies that determined membrane exposure. Ev/Trt represents the test (cross-linked membranes) group, while Ev/Ctrl represents the control (non-cross-linked membranes) group. Red line represents the average for all results, and the vertical black line represents the no-effect line (from Garcia J, et al. Effect of cross-linked vs non-cross-linked collagen membranes on bone: A systematic review. <span class="html-italic">J Periodontal Res</span>. 2017;52(6):955–964. With permission).</p> Full article ">
10 pages, 4707 KiB  
Article
Low Temperature Synthesis of Phase Pure MoAlB Powder in Molten NaCl
by Cheng Liu, Zhaoping Hou, Quanli Jia, Xueyin Liu and Shaowei Zhang
Materials 2020, 13(3), 785; https://doi.org/10.3390/ma13030785 - 9 Feb 2020
Cited by 25 | Viewed by 3863
Abstract
MoAlB fine powders were prepared in molten NaCl from Al, B and Mo powders. The effects of key parameters affecting the synthesis process and phase morphology were examined and the underpinning mechanisms proposed. MoAlB product particles exhibited different shapes/sizes, as follows: spherical grains [...] Read more.
MoAlB fine powders were prepared in molten NaCl from Al, B and Mo powders. The effects of key parameters affecting the synthesis process and phase morphology were examined and the underpinning mechanisms proposed. MoAlB product particles exhibited different shapes/sizes, as follows: spherical grains (1~3 μm), plate-like particles (<5 μm in diameter) and columnar crystals with lengths up to 20 μm and diameters up to 5 μm, resultant from different reaction processes. Phase pure MoAlB was synthesised under the following optimal conditions: use of 140% excess Al and 6 h of firing at 1000 °C. This temperature was at least 100 °C lower than required by other methods/techniques previously reported. At the synthesis condition, Mo first reacted with Al and B, forming Al8Mo3 and MoB, respectively, which further reacted with excess Al to form Al-rich Al–Mo phases and MoAlB. The Al-rich Al–Mo phases further reacted with the residual B, forming additional MoAlB. The molten NaCl played an important role in accelerating the overall synthesis process. Full article
(This article belongs to the Special Issue High Temperature Ceramic Materials)
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<p>XRD spectra of the samples with the stoichiometric composition after 6 h at (<b>a</b>) 850, (<b>b</b>) 900 and (<b>c</b>) 950 °C.</p> Full article ">Figure 2
<p>XRD spectra of the samples heated at 850 °C for 6 h, with different amounts of excess Al at (<b>a</b>) stoichiometric amount, (<b>b</b>) 60%, (<b>c</b>) 80%, (<b>d</b>) 100% and (<b>e</b>) 120%.</p> Full article ">Figure 3
<p>XRD patterns of the samples with various amounts of excess Al, after 6 h of firing at (<b>a</b>) 900 and (<b>b</b>) 950 °C, separately.</p> Full article ">Figure 4
<p>XRD patterns of samples with 120% and 140% excess Al, separately, after 6 h of firing at 1000 °C.</p> Full article ">Figure 5
<p>(<b>a</b>) XRD pattern of the sample after 6 h of firing at 1000 °C and the subsequent acid leaching, and (<b>b</b>) comparison of XRD patterns (within 36–40°) of the samples before and after acid leaching.</p> Full article ">Figure 5 Cont.
<p>(<b>a</b>) XRD pattern of the sample after 6 h of firing at 1000 °C and the subsequent acid leaching, and (<b>b</b>) comparison of XRD patterns (within 36–40°) of the samples before and after acid leaching.</p> Full article ">Figure 6
<p>(<b>a</b>) Low and (<b>b</b>) high magnification SEM images of MoAlB particles resulting from 6 h of firing at 1000 °C and the subsequent acid leaching.</p> Full article ">Figure 7
<p>(<b>a</b>) TEM image and (<b>b</b>) selected area electron diffraction (SAED) of a representative MoAlB crystal in the sample, whose microstructure is shown in <a href="#materials-13-00785-f006" class="html-fig">Figure 6</a>.</p> Full article ">
24 pages, 5273 KiB  
Review
Antimicrobial Nanostructured Coatings: A Gas Phase Deposition and Magnetron Sputtering Perspective
by Giulio Benetti, Emanuele Cavaliere, Francesco Banfi and Luca Gavioli
Materials 2020, 13(3), 784; https://doi.org/10.3390/ma13030784 - 8 Feb 2020
Cited by 29 | Viewed by 4960
Abstract
Counteracting the spreading of multi-drug-resistant pathogens, taking place through surface-mediated cross-contamination, is amongst the higher priorities in public health policies. For these reason an appropriate design of antimicrobial nanostructured coatings may allow to exploit different antimicrobial mechanisms pathways, to be specifically activated by [...] Read more.
Counteracting the spreading of multi-drug-resistant pathogens, taking place through surface-mediated cross-contamination, is amongst the higher priorities in public health policies. For these reason an appropriate design of antimicrobial nanostructured coatings may allow to exploit different antimicrobial mechanisms pathways, to be specifically activated by tailoring the coatings composition and morphology. Furthermore, their mechanical properties are of the utmost importance in view of the antimicrobial surface durability. Indeed, the coating properties might be tuned differently according to the specific synthesis method. The present review focuses on nanoparticle based bactericidal coatings obtained via magneton-spattering and supersonic cluster beam deposition. The bacteria–NP interaction mechanisms are first reviewed, thus making clear the requirements that a nanoparticle-based film should meet in order to serve as a bactericidal coating. Paradigmatic examples of coatings, obtained by magnetron sputtering and supersonic cluster beam deposition, are discussed. The emphasis is on widening the bactericidal spectrum so as to be effective both against gram-positive and gram-negative bacteria, while ensuring a good adhesion to a variety of substrates and mechanical durability. It is discussed how this goal may be achieved combining different elements into the coating. Full article
(This article belongs to the Special Issue Antimicrobial Nanomaterials)
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Figure 1
<p>Schematic representation of a bacterium on a surface of a nanostructured coating. The major coating/bacterium interaction mechanisms are listed.</p> Full article ">Figure 2
<p>(<b>a</b>) Scheme of the magnetron sputtering process.; (<b>b</b>) scheme of the beam synthesis from pulsed gas sources.</p> Full article ">Figure 3
<p>(<b>A</b>) Plot of the X-ray diffraction intensity versus 2θ showing single phase cubic AgO and mixed phase AgO and Ag<sub>2</sub>O deposited at lower oxygen partial pressure; (<b>B</b>) scanning electron micrograph showing the typical surface microstructure of the silver oxide deposited at room temperature. The microstructure can be impacted by deposition pressure, deposition power, oxygen partial pressure, and coating thickness. Reprinted from [<a href="#B67-materials-13-00784" class="html-bibr">67</a>] under the Creative Commons Attribution License 4.0.</p> Full article ">Figure 4
<p>(<b>a</b>) Hardness H (gray squares), effective Young’s modulus E* (black circles); and (<b>b</b>) elastic recovery We (gray squares) and H/E* ratio (black circles) of Zr–Cu–N coatings sputtered on Si (100) substrates as a function of Cu content. Reprinted from [<a href="#B121-materials-13-00784" class="html-bibr">121</a>], Copyright 2015, with permission from AIP Publishing LLC.</p> Full article ">Figure 5
<p>(<b>a</b>) Normalized O1s core level spectra obtained from the as-deposited Ag NPs film (curve 0d) and from the same film two days (curve 2d), seven days (curve 7d) and fifteen days (curve 15d) after the deposition. In the bottom panel the difference spectra show that the variation of the peak observed after 2 days (curve 2d-0d) remains mostly unchanged up to 15 days. (<b>b</b>) O1s core level obtained from the Ag NPs film two days after deposition, with the peaks resulting from the least square fitting procedure. The AgO related peak (dark gray) is at 530.2 eV binding energy while the SiO<sub>2</sub> related peak (light gray) is at 531.6 eV binding energy. (<b>c</b>) intensity dependence of the relative area of the two peaks as a function of time.</p> Full article ">Figure 6
<p>(<b>a</b>) The NPs virtual thin film (dimensions L<sub>X</sub> × L<sub>Y</sub> × L<sub>Z</sub> = 35 nm × 20 nm × 30 nm) obtained by MD simulations. The NPs are divided into blue (large, diameter ~ 6 nm) and green (small, diameter ~ 1 nm). (<b>b</b>) Experimental AFM image of the 30 nm-thick Ag NPs film. (<b>c</b>) Computed AFM images obtained from the simulated cell and taking into account tip convolution effects. The computed images are obtained from intermediate deposition steps of the MD simulations, i.e., subsequent shots of the simulation resulting in films of average thickness ⟨t<sub>F</sub>⟩ = 9, 14, 23, 27, and 31 nm for shots one through five, respectively. Adapted from [<a href="#B132-materials-13-00784" class="html-bibr">132</a>] (<a href="https://pubs.acs.org/doi/10.1021/acs.jpcc.7b05795" target="_blank">https://pubs.acs.org/doi/10.1021/acs.jpcc.7b05795</a>), with permission from ACS (further permissions related to the material excerpted should be directed to the ACS).</p> Full article ">Figure 7
<p>Quantification of the ME for different extensively drug-resistant phenotypes. All microorganisms were tested in three independent experiments and results were averaged. To calculate standard deviations (SD), when no viable cells were counted, the result was arbitrarily assumed as 4.2 × 10<sup>1</sup> CFU, representing the detection limit value.</p> Full article ">Figure 8
<p>(<b>a</b>,<b>d</b>) TEM images of AgTi8020 and AgTi5050 scattered NPs, respectively, with the relative elemental map plotted in panels (<b>b</b>,<b>c</b>), respectively. The data show that Ag and Ti are phase-separated into the NPs. (<b>e</b>,<b>f</b>) HR-STEM images of the NPs, with the inset showing the FFT analysis of Ag crystalline structure of the zone in the purple rectangle. Red arrows indicate small Ag NPs, and green arrows point to the Ti part of the NPs. The data indicate that Ag is crystalline and Ti is amorphous. (<b>g</b>,<b>h</b>) Schematic representation of the elemental weight in the initial rod and in the NPS, showing the good correspondence of the material concentration. Adapted from Ref. [<a href="#B71-materials-13-00784" class="html-bibr">71</a>] under the Creative Commons Attribution License 4.0.</p> Full article ">Figure 9
<p>STEM (<b>a</b>) and corresponding EDX elemental maps (<b>b</b>) for the Mg/Ag/Cu NPs. Scale bar is 20 nm. Adapted from Ref. [<a href="#B146-materials-13-00784" class="html-bibr">146</a>] under the Creative Commons Attribution License 4.0.</p> Full article ">Figure 10
<p>Microbicidal tests on S. aureus (blue) and E. coli (red), comparing the count of viable bacteria (reported as CFU per milliliter) of the control before incubation (T0), control bare substrate after incubation (Control), pure Mg NPs (Mg NP), and tri-elemental AgCuMg503020 film. The dashed line at 10<sup>2</sup> CFU ml<sup>−1</sup> is the limit of detection of the experiment. Reproduced from [<a href="#B146-materials-13-00784" class="html-bibr">146</a>] by permission of the PCCP Owner Societies.</p> Full article ">
13 pages, 3105 KiB  
Article
Energy Absorption Behavior of Al-SiC-Graphene Composite Foam under a High Strain Rate
by Sourav Das, Dipen Kumar Rajak, Sanjeev Khanna and D. P. Mondal
Materials 2020, 13(3), 783; https://doi.org/10.3390/ma13030783 - 8 Feb 2020
Cited by 16 | Viewed by 3652
Abstract
The present work was addressed to the closed-cell aluminum (Al)-silicon carbide (SiC) particles (15 wt.%) with graphene (0.5 wt.%) reinforced hybrid composite foam, which was produced through the melt route process. Under the strain rates ranging from 500 s-1 to 2760 s [...] Read more.
The present work was addressed to the closed-cell aluminum (Al)-silicon carbide (SiC) particles (15 wt.%) with graphene (0.5 wt.%) reinforced hybrid composite foam, which was produced through the melt route process. Under the strain rates ranging from 500 s-1 to 2760 s-1, the compression deformation behavior of hybrid composite foam was executed. The compression results disclosed that plateau stress along with energy absorption of produced hybrid composite foam are heightened with strain rates and is also discovered to be responsive to the relative density under the confront domain of experiments. Analysis of Variance was deployed for optimizing parameters such as strain rates, mass, density, relative density, and pore size. Furthermore, the contribution of each optimized parameters on plateau stress and energy absorption were observed. Full article
(This article belongs to the Special Issue Microstructure-mechanical Properties Relationship for Porous Materials)
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Figure 1
<p>(<b>a</b>) Al foam block; (<b>b</b>) polished sample.</p> Full article ">Figure 2
<p>Pore size distribution of Al-SiC hybrid composite foam.</p> Full article ">Figure 3
<p>(<b>a</b>) SHPB (Split Hopkinson Pressure Bar) apparatus applied in the confront investigation as viewed from the transmitter bar end and foam specimen between the incident and transmitted bar shown in under doted circle; (<b>b</b>) major components of SHPB.</p> Full article ">Figure 4
<p>(<b>a</b>) SEM micrograph showing pores and SiC particles in the cell walls; (<b>b</b>) micrograph showing the distribution of SiC particles in the cell wall.</p> Full article ">Figure 5
<p>(<b>a</b>) compressive stress–strain diagram of Al hybrid composite foam with RD = 0.29 at different strain rate (500 s<sup>-1</sup> to 2700 s<sup>−1</sup>); (<b>b</b>) stress and energy absorption relation with RD.</p> Full article ">Figure 6
<p>Residual plots obtained for energy absorption from the ANOVA test.</p> Full article ">Figure 7
<p>Main effect plot for energy absorption.</p> Full article ">Figure 8
<p>Interaction plot for energy absorption from the ANOVA test.</p> Full article ">
31 pages, 10540 KiB  
Review
Waste Rubber Recycling: A Review on the Evolution and Properties of Thermoplastic Elastomers
by Ali Fazli and Denis Rodrigue
Materials 2020, 13(3), 782; https://doi.org/10.3390/ma13030782 - 8 Feb 2020
Cited by 155 | Viewed by 24026
Abstract
Currently, plastics and rubbers are broadly being used to produce a wide range of products for several applications like automotive, building and construction, material handling, packaging, toys, etc. However, their waste (materials after their end of life) do not degrade and remain for [...] Read more.
Currently, plastics and rubbers are broadly being used to produce a wide range of products for several applications like automotive, building and construction, material handling, packaging, toys, etc. However, their waste (materials after their end of life) do not degrade and remain for a long period of time in the environment. The increase of polymeric waste materials’ generation (plastics and rubbers) in the world led to the need to develop suitable methods to reuse these waste materials and decrease their negative effects by simple disposal into the environment. Combustion and landfilling as traditional methods of polymer waste elimination have several disadvantages such as the formation of dust, fumes, and toxic gases in the air, as well as pollution of underground water resources. From the point of energy consumption and environmental issues, polymer recycling is the most efficient way to manage these waste materials. In the case of rubber recycling, the waste rubber can go through size reduction, and the resulting powders can be melt blended with thermoplastic resins to produce thermoplastic elastomer (TPE) compounds. TPE are multi-functional polymeric materials combining the processability of thermoplastics and the elasticity of rubbers. However, these materials show poor mechanical performance as a result of the incompatibility and immiscibility of most polymer blends. Therefore, the main problem associated with TPE production from recycled materials via melt blending is the low affinity and interaction between the thermoplastic matrix and the crosslinked rubber. This leads to phase separation and weak adhesion between both phases. In this review, the latest developments related to recycled rubbers in TPE are presented, as well as the different compatibilisation methods used to improve the adhesion between waste rubbers and thermoplastic resins. Finally, a conclusion on the current situation is provided with openings for future works. Full article
(This article belongs to the Special Issue Recent Advances in Rubber Recycling)
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Figure 1
<p>Chemical structure of isoprene and natural rubber (NR) (polyisoprene). Adapted with permission from [<a href="#B12-materials-13-00782" class="html-bibr">12</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 2
<p>Chemical structure of styrene-butadiene rubber (SBR). Adapted with permission from [<a href="#B12-materials-13-00782" class="html-bibr">12</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 3
<p>Monomers and polymer structure of nitrile-butadiene rubber (NBR). Adapted with permission from [<a href="#B12-materials-13-00782" class="html-bibr">12</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 4
<p>Chemical structure of ethylene-propylene-diene monomer (EPDM) containing 5-ethylidene-2-norborene (ENB) as a diene. Adapted with permission from [<a href="#B15-materials-13-00782" class="html-bibr">15</a>]; copyright 2019 John Wiley and Sons Ltd.</p> Full article ">Figure 5
<p>Schematic representation of polyurethane (PU) and its monomers. Adapted with permission from [<a href="#B18-materials-13-00782" class="html-bibr">18</a>]; copyright 2019 RSC Publishing.</p> Full article ">Figure 6
<p>The four groups making polysiloxanes: “M” is trimethylsiloxychlorosilanes (Me<sub>3</sub>SiO), “D” Me<sub>2</sub>SiO<sub>2</sub>, “T” MeSiO<sub>3</sub>, and “Q” silicate (SiO<sub>4</sub>). For “P”, replace Me by phenyl side groups, while for “V”, replace Me by vinyl side groups. Adapted with permission from [<a href="#B12-materials-13-00782" class="html-bibr">12</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 7
<p>Morphology of a block copolymer thermoplastic elastomer (TPE). Adapted with permission from [<a href="#B33-materials-13-00782" class="html-bibr">33</a>]; copyright 2020 Elsevier Ltd.</p> Full article ">Figure 8
<p>Morphology of rubber/plastic blend thermoplastic elastomer (TPE). Adapted with permission from [<a href="#B32-materials-13-00782" class="html-bibr">32</a>]; copyright 2020 Elsevier Ltd.</p> Full article ">Figure 9
<p>Thermoplastic vulcanizates (TPV) morphology with continuous plastic phase and discrete rubber particles. Adapted with permission from [<a href="#B32-materials-13-00782" class="html-bibr">32</a>]; copyright 2020 Elsevier Ltd.</p> Full article ">Figure 10
<p>Processing steps to produce thermoplastic vulcanizates (TPV) compounds. Adapted with permission from [<a href="#B42-materials-13-00782" class="html-bibr">42</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 11
<p>Different structures of linear copolymers: (<b>a</b>) alternating, (<b>b</b>) random, (<b>c</b>) gradient, and (<b>d</b>) block copolymers. Adapted with permission from [<a href="#B45-materials-13-00782" class="html-bibr">45</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 12
<p>Notched Izod impact strength of high-density polyethylene (HDPE)/ground tire rubber (GTR) composites as a function of rubber content. Adapted with permission from [<a href="#B50-materials-13-00782" class="html-bibr">50</a>]; copyright 2019 John Wiley and Sons Ltd.</p> Full article ">Figure 13
<p>The three possible cases for nanoparticles’ (NP) localisation in an immiscible binary polymer blend: (<b>a</b>) in the dispersed phase, (<b>b</b>) at the interface (ideal case), or (<b>c</b>) in the continuous phase. Adapted with permission from [<a href="#B58-materials-13-00782" class="html-bibr">58</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 14
<p>Schematic representation of the devulcanisation and reclamation process. Adapted with permission from [<a href="#B1-materials-13-00782" class="html-bibr">1</a>]; copyright 2020 Elsevier Ltd.</p> Full article ">Figure 15
<p>Elongation at break as a function of composition for ground tire rubber (GTR)/polypropylene (PP) blends. Adapted with permission from [<a href="#B73-materials-13-00782" class="html-bibr">73</a>]; copyright 2019 Taylor &amp; Francis Ltd.</p> Full article ">Figure 16
<p>Effect of ground tire rubber (GTR) particle size on the mechanical properties of thermoplastic blends. Adapted with permission from [<a href="#B1-materials-13-00782" class="html-bibr">1</a>]; copyright 2020 Elsevier Ltd.</p> Full article ">Figure 17
<p>SEM micrographs of ethylene-vinyl acetate (EVA) blends with different ground tire rubber (GTR) contents: (<b>a</b>) 10 wt.%, (<b>b</b>) 20 wt.%, (<b>c</b>) 50 wt.%, and (<b>d</b>) 70 wt.%. Adapted with permission from [<a href="#B74-materials-13-00782" class="html-bibr">74</a>]; copyright 2019 SAGE Publications Ltd.</p> Full article ">Figure 18
<p>Torque evolution for polypropylene (PP)/waste tire dust (WTD) blends (250–500 μm). Adapted with permission from [<a href="#B73-materials-13-00782" class="html-bibr">73</a>]; copyright 2019 Taylor &amp; Francis Ltd.</p> Full article ">Figure 19
<p>Complex viscosity as a function of angular frequency for thermoplastic natural rubber (TPNR) based on different natural rubber (NR)/high-density polyethylene (HDPE) ratios. Adapted with permission from [<a href="#B82-materials-13-00782" class="html-bibr">82</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 20
<p>Storage modulus (G′) as a function of angular frequency for thermoplastic natural rubber (TPNR) based on different natural rubber (NR)/high-density polyethylene (HDPE) ratios. Adapted with permission from [<a href="#B82-materials-13-00782" class="html-bibr">82</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 21
<p>Hardness of high-density polyethylene (HDPE) as a function of reclaimed rubber (RR) content: (1) H-R10, (2) HR10-C, (3) H-R10-P. Adapted with permission from [<a href="#B77-materials-13-00782" class="html-bibr">77</a>]; copyright 2019 Springer Nature Ltd.</p> Full article ">Figure 22
<p>Tensile stress-strain curves of high-density polyethylene (HDPE) and HDPE/ground tire rubber (GTR) compounds. Adapted with permission from [<a href="#B50-materials-13-00782" class="html-bibr">50</a>]; copyright 2019 John Wiley and Sons Ltd.</p> Full article ">Figure 23
<p>Reaction mechanism for low-density polyethylene (LDPE)/natural rubber (NR) modified with maleic anhydride (MA). Adapted with permission from [<a href="#B85-materials-13-00782" class="html-bibr">85</a>]; copyright 2019 Taylor &amp; Francis Ltd.</p> Full article ">Figure 24
<p>X-ray diffraction patterns of: (<b>a</b>) Cloisite 15A and TPE nanocomposites based on polypropylene (PP) with: (<b>b</b>) 60%, (<b>c</b>) 40%, and (<b>d</b>) 20% ethylene-propylene-diene monomer (EPDM). Adapted with permission from [<a href="#B87-materials-13-00782" class="html-bibr">87</a>]; copyright 2019 John Wiley and Sons Ltd.</p> Full article ">Figure 25
<p>SEM micrographs of TPE based on: (<b>a</b>) unfilled polypropylene (PP)/ethylene-propylene-diene monomer (EPDM) (60/40), (<b>b</b>) nanoclay-filled PP/EPDM (60/40), (<b>c</b>) unfilled PP/EPDM (40/60), and (<b>d</b>) nanoclay-filled PP/EPDM (40/60) blends. Adapted with permission from [<a href="#B87-materials-13-00782" class="html-bibr">87</a>]; copyright 2019 John Wiley and Sons Ltd.</p> Full article ">Figure 26
<p>SEM of the ground tire rubber (GTR) particles surface: (<b>a</b>) untreated and treated with: (<b>b</b>) perchloric acid (HClO<sub>4</sub>), (<b>c</b>) nitric acid (HNO<sub>3</sub>), and (<b>d</b>) sulphuric acid (H<sub>2</sub>SO<sub>4</sub>). Adapted with permission from [<a href="#B89-materials-13-00782" class="html-bibr">89</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 27
<p>Compatibilisation mechanism of thermoplastic/ground tire rubber (GTR) blends using an elastomer as a modifier. Adapted with permission from [<a href="#B80-materials-13-00782" class="html-bibr">80</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 28
<p>Tensile strength and elongation at break of dynamically cured devulcanized rubber (DR)/copolyester (COPE) blends as a function of the devulcanisation time at 180 °C. Adapted with permission from [<a href="#B91-materials-13-00782" class="html-bibr">91</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">Figure 29
<p>Schematic representation of the microstructure differences between the thermoplastic vulcanizates (TPV) based on devulcanized rubber (DR)/copolyester (COPE) and undevulcanised rubber (DR)/copolyester (COPE) blends. Adapted with permission from [<a href="#B91-materials-13-00782" class="html-bibr">91</a>]; copyright 2019 Elsevier Ltd.</p> Full article ">
15 pages, 3706 KiB  
Article
First Electrochemical Sensor (Screen-Printed Carbon Electrode Modified with Carboxyl Functionalized Multiwalled Carbon Nanotubes) for Ultratrace Determination of Diclofenac
by Agnieszka Sasal, Katarzyna Tyszczuk-Rotko, Magdalena Wójciak and Ireneusz Sowa
Materials 2020, 13(3), 781; https://doi.org/10.3390/ma13030781 - 8 Feb 2020
Cited by 16 | Viewed by 3784
Abstract
A simple, sensitive and time-saving differential-pulse adsorptive stripping voltammetric (DPAdSV) procedure using a screen-printed carbon electrode modified with carboxyl functionalized multiwalled carbon nanotubes (SPCE/MWCNTs-COOH) for the determination of diclofenac (DF) is presented. The sensor was characterized using optical profilometry, SEM, and cyclic voltammetry [...] Read more.
A simple, sensitive and time-saving differential-pulse adsorptive stripping voltammetric (DPAdSV) procedure using a screen-printed carbon electrode modified with carboxyl functionalized multiwalled carbon nanotubes (SPCE/MWCNTs-COOH) for the determination of diclofenac (DF) is presented. The sensor was characterized using optical profilometry, SEM, and cyclic voltammetry (CV). The use of carboxyl functionalized MWCNTs as a SPCE modifier improved the electron transfer process and the active surface area of sensor. Under optimum conditions, very sensitive results were obtained with a linear range of 0.1–10.0 nmol L−1 and a limit of detection value of 0.028 nmol L−1. The SPCE/MWCNTs-COOH also exhibited satisfactory repeatability, reproducibility, and selectivity towards potential interferences. Moreover, for the first time, the electrochemical sensor allows determining the real concentrations of DF in environmental water samples without sample pretreatment steps. Full article
(This article belongs to the Section Carbon Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Differential-pulse adsorptive stripping voltammetric (DPAdSV) curves of diclofenac (DF) with different concentrations in a 0.1 mol L<sup>−1</sup> NaAc–HAc solution with a pH value of 5.0 ± 0.1 at the surface of a bare screen-printed carbon electrode (SPCE) (a,b) and the surface of a screen-printed carbon electrode modified with multiwalled carbon nanotubes (SPCE/MWCNTs-COOH) (c,d). (a) and (c) are for the DF concentration of 0.05 µmol L<sup>−1</sup>. (b) and (d) are for the DF concentration of 0.1 µmol L<sup>−1</sup>. The DPAdSV parameters: accumulation potential (<span class="html-italic">E<sub>acc</sub></span>) of −0.5 V, accumulation time (<span class="html-italic">t<sub>acc</sub></span>) of 30 s, amplitude <span class="html-italic">(A</span>) of 100 mV, modulation time (<span class="html-italic">t<sub>m</sub></span>) of 40 ms, and scan rate (<span class="html-italic">ν</span>) of 175 mV s<sup>−1</sup>.</p> Full article ">Figure 2
<p>(<b>A</b>) Optical profiles. (<b>B</b>) SEM images of the SPCE (a) and the SPCE/MWCNTs-COOH (b). (<b>C</b>) CV curves recorded at the surfaces of the SPCE (a) and the SPCE/MWCNTs-COOH (b) in a solution of 0.1 mol L<sup>−1</sup> KCl containing 5.0 mmol L<sup>−1</sup> K<sub>3</sub>[Fe(CN)<sub>6</sub>] at a <span class="html-italic">ν</span> range of 5–500 mV s<sup>−1</sup>. (<b>D</b>) Dependences between <span class="html-italic">I<sub>p</sub></span> and <span class="html-italic">v</span><sup>1/2</sup> for the SPCE (a) and the SPCE/MWCNTs (b).</p> Full article ">Figure 3
<p>Effects of pH value (<b>A</b>) and concentration of the NaAc–HAc buffer solution with a pH value of 4.0 ± 0.1 (<b>B</b>) on DF current response. (a) and (b) in (<b>A</b>) are for the DF concentration of 0.05 and 0.1 µmol L<sup>−1</sup>, respectively. (a) and (b) in (<b>B</b>) are for the DF concentration of 0.05 and 0.1 µmol L<sup>−1</sup>, respectively. Other parameters are the same as in <a href="#materials-13-00781-f001" class="html-fig">Figure 1</a>.</p> Full article ">Figure 4
<p>(<b>A</b>) CV curves recorded in the 0.1 mol L<sup>−1</sup> NaAc–HAc buffer solution with a pH value of 4.0 ± 0.1 at <span class="html-italic">v</span> equal to 175 mV s<sup>−1</sup>. Curves (a–c) represent CV curves in the solution without DF and with 1.0 µmol L<sup>−1</sup> DF for the first cycle and the second cycle, respectively. (<b>B</b>) CV curves recorded in the 0.1 mol L<sup>−1</sup> NaAc–HAc buffer solution with a pH value of 4.0 ± 0.1 containing 1.0 µmol L<sup>−1</sup> DF at different <span class="html-italic">v</span> values. Curves (a–c) represent CV curves at <span class="html-italic">v</span> equal to 50, 100, and 175 mV s<sup>−1</sup>, respectively. The dependences between <span class="html-italic">Ip</span> and <span class="html-italic">v</span><sup>1/2</sup> (<b>C</b>), log<span class="html-italic">Ip</span> and log<span class="html-italic">v</span> (<b>D</b>), and <span class="html-italic">E<sub>p</sub></span> and log<span class="html-italic">v</span> (<b>E</b>) for <span class="html-italic">v</span> from 5 to 250 mV s<sup>−1</sup>. (<b>F</b>) Oxidation mechanism of DF</p> Full article ">Figure 5
<p>Effects of <span class="html-italic">E<sub>acc</sub></span> (<b>A</b>) and <span class="html-italic">t<sub>acc</sub></span> (<b>B</b>) on DF current response. (a,b) in (<b>A</b>) represent the responses for DF concentrations of 0.01 and 0.05 µmol L<sup>−1</sup>, respectively. (a,b) in (<b>B</b>) represent the responses for DF concentrations of 0.01 and 0.05 µmol L<sup>−1</sup>, respectively. The DPAdSV parameters in (<b>A</b>) are t<sub>acc</sub> of 30 s, <span class="html-italic">A</span> of 100 mV, <span class="html-italic">t<sub>m</sub></span> of 40 ms, and <span class="html-italic">ν</span> of 175 mV s<sup>−1</sup>; the DPAdSV parameters in (<b>B</b>) are <span class="html-italic">E<sub>acc</sub></span> of −0.25 V, <span class="html-italic">A</span> of 100 mV, <span class="html-italic">t<sub>m</sub></span> of 40 ms, and <span class="html-italic">ν</span> of 175 mV s<sup>−1</sup>.</p> Full article ">Figure 6
<p>Effects of <span class="html-italic">A</span> (<b>A</b>), <span class="html-italic">ν</span> (<b>B</b>), and <span class="html-italic">t<sub>m</sub></span> (<b>C</b>) on DF current response. Curves (a,b) are for 0.01 and 0.05 µmol L<sup>−1</sup> DF, respectively. The DPAdSV parameters: (<b>A</b>) <span class="html-italic">E<sub>acc</sub></span> of −0.25 V, <span class="html-italic">t<sub>acc</sub></span> of 60 s, <span class="html-italic">ν</span> of 175 mV s<sup>−1</sup> and <span class="html-italic">t<sub>m</sub></span> of 40 ms; (<b>B</b>) A of 125 mV and t<sub>m</sub> of 40 ms; and (<b>C</b>) <span class="html-italic">A</span> of 125 mV and <span class="html-italic">ν</span> of 175 mV s<sup>−1</sup>.</p> Full article ">Figure 7
<p>(<b>A</b>) DPAdSV curves recorded at the surface of the SPCE/MWCNTs-COOH in the NaAc–HAc buffer solution with a pH value of 4.0 ± 0.1 containing increasing concentrations of DF: (a) 0.1, (b) 0.2, (c) 0.5, (d) 1.0, (e) 2.0, (f) 5.0, and (g) 10.0 nmol L<sup>-1</sup>. (<b>B</b>) Calibration graph of DF. The DPAdSV parameters: <span class="html-italic">E<sub>acc</sub></span> of −0.25 V, <span class="html-italic">t<sub>acc</sub></span> of 60 s, <span class="html-italic">A</span> of 125 mV, <span class="html-italic">t<sub>m</sub></span> of 10 ms, and <span class="html-italic">ν</span> of 175 mV s<sup>−1</sup>.</p> Full article ">Figure 8
<p>DPAdSV curves recorded at the SPCE/MWCNTs-COOH surface in the course of DF determination in 5 ml Vistula river water sample #1 without DF (a) and with 0.5 nmol L<sup>−1</sup> (b), 1.0 (c) nmol L<sup>−1</sup><sup>,</sup> and 1.5 nmol L<sup>−1</sup> (d) of DF. Other conditions are the same as in <a href="#materials-13-00781-f007" class="html-fig">Figure 7</a>.</p> Full article ">
14 pages, 12735 KiB  
Article
Maintenance of the Austenite/Ferrite Ratio Balance in GTAW DSS Joints Through Process Parameters Optimization
by Bryan R. Rodriguez, Argelia Miranda, David Gonzalez, Rolando Praga and Eduardo Hurtado
Materials 2020, 13(3), 780; https://doi.org/10.3390/ma13030780 - 8 Feb 2020
Cited by 16 | Viewed by 3428
Abstract
The present work describes the influence of the parameters employed in the gas tungsten arc welding process (GTAW) when nickel powder is used as a filler metal in 2304/2507 duplex stainless-steel dissimilar joints. Multi-objective optimization was applied in order to maintain the austenite/ferrite [...] Read more.
The present work describes the influence of the parameters employed in the gas tungsten arc welding process (GTAW) when nickel powder is used as a filler metal in 2304/2507 duplex stainless-steel dissimilar joints. Multi-objective optimization was applied in order to maintain the austenite/ferrite percentage in the welded zone. A microstructural and phase quantification analysis was performed in each sample through optical and scanning electron microscopes. It was found that a nickel powder addition combined with low heat input increased the biphasic ratio across the different zones of the dissimilar welded samples. Although the austenite volume fraction increased in the 2304 heat-affected zone (HAZ) near to 25%, it was not sufficient according to international standards. The obtained results led to the maintenance of the 50/50 phase percentage in the 2507 HAZ welded joint side, as well as to the increment of the austenite percentage in the 2304 HAZ. Full article
(This article belongs to the Special Issue Advances in Duplex Stainless Steels)
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<p>Scheme of the dissimilar duplex stainless-steel butt joint.</p> Full article ">Figure 2
<p>Box plot for austenite percentage. FZ: fusion zone; HAZ: heat-affected zone.</p> Full article ">Figure 3
<p>Base metal microstructure observed by scanning electron microscope (SEM): (<b>a</b>) SDSS 2304 and (<b>b</b>) SDSS 2507. δ: ferrite phase; γ: austenite phase.</p> Full article ">Figure 4
<p>Welded zones by optical microscope to 10 ×: (<b>a</b>) Test #3 and (<b>b</b>) Test #1.</p> Full article ">Figure 5
<p>Welded zones by optical microscope to 50 × : 130 A welding current.</p> Full article ">Figure 6
<p>Welded zones by optical microscope to 50 ×: 220 A welding current.</p> Full article ">Figure 7
<p>Area fraction through the distinct welded zones: (<b>a</b>) Test #1 and (<b>b</b>) Test #2.</p> Full article ">Figure 8
<p>Area fraction through the distinct welded zones: (<b>a</b>) Test #3 and (<b>b</b>) Test #4.</p> Full article ">Figure 9
<p>SEM micrographs of the heat-affected zone: (<b>a</b>) lean duplex stainless steel (LDSS) 2304; and (<b>b</b>) SDSS 2507. WA: Widmanstätten austenite; IGA: intragranular austenite; PTA: partially transformed austenite; GBA: grain boundary austenite.</p> Full article ">Figure 10
<p>Area fraction through the distinct welded zones to 220 A: (<b>a</b>) Test #5 and (<b>b</b>) Test #6.</p> Full article ">Figure 11
<p>Area fraction through the distinct welded zones to 175 A: (<b>a</b>) Test #7 and (<b>b</b>) Test #8.</p> Full article ">Figure 12
<p>Area fraction through the distinct welded zones to 130 A: (<b>a</b>) Test #9 and (<b>b</b>) Test #10.</p> Full article ">Figure 13
<p>Area fraction through the distinct welded zones: (<b>a</b>) Test #11 and (<b>b</b>) Test #12.</p> Full article ">
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