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Volume 13, January-1

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Materials, Volume 13, Issue 2 (January-2 2020) – 214 articles

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Open AccessArticle
Absolute Rheological Measurements of Model Suspensions: Influence and Correction of Wall Slip Prevention Measures
Materials 2020, 13(2), 467; https://doi.org/10.3390/ma13020467 (registering DOI) - 18 Jan 2020
Abstract
Since suspensions (e.g., in food, cement, or cosmetics industries) tend to show wall slip, the application of structured measuring surfaces in rheometers is widespread. Usually, for parallel-plate geometries, the tip-to-tip distance is used for calculation of absolute rheological values, which implies that there [...] Read more.
Since suspensions (e.g., in food, cement, or cosmetics industries) tend to show wall slip, the application of structured measuring surfaces in rheometers is widespread. Usually, for parallel-plate geometries, the tip-to-tip distance is used for calculation of absolute rheological values, which implies that there is no flow behind this distance. However, several studies show that this is not true. Therefore, the measuring gap needs to be corrected by adding the effective gap extension δ to the prescribed gap height H in order to obtain absolute rheological properties. In this paper, we determine the effective gap extension δ for different structures and fluids (Newtonian, shear thinning, and model suspensions that can be adjusted to the behavior of real fluids) and compare the corrected values to reference data. We observe that for Newtonian fluids a gap- and material-independent correction function can be derived for every measuring system, which is also applicable to suspensions, but not to shear thinning fluids. Since this relation appears to be mainly dependent on the characteristics of flow behaviour, we show that the calibration of structured measuring systems is possible with Newtonian fluids and then can be transferred to suspensions up to a certain particle content. Full article
(This article belongs to the Special Issue Rheology of Reactive, Multiscale, Multiphase Construction Materials)
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Open AccessReview
Parameters Influencing the Outcome of Additive Manufacturing of Tiny Medical Devices Based on PEEK
Materials 2020, 13(2), 466; https://doi.org/10.3390/ma13020466 (registering DOI) - 18 Jan 2020
Abstract
In this review, we discuss the parameters of fused deposition modeling (FDM) technology used in finished parts made from polyether ether ketone (PEEK) and also the possibility of printing small PEEK parts. The published articles reporting on 3D printed PEEK implants were obtained [...] Read more.
In this review, we discuss the parameters of fused deposition modeling (FDM) technology used in finished parts made from polyether ether ketone (PEEK) and also the possibility of printing small PEEK parts. The published articles reporting on 3D printed PEEK implants were obtained using PubMed and search engines such as Google Scholar including references cited therein. The results indicate that although many have been experiments conducted on PEEK 3D printing, the consensus on a suitable printing parameter combination has not been reached and optimized parameters for printing worth pursuing. The printing of reproducible tiny-sized PEEK parts with high accuracy has proved to be possible in our experiments. Understanding the relationships among material properties, design parameters, and the ultimate performance of finished objects will be the basis for further improvement of the quality of 3D printed medical devices based on PEEK and to expand the polymers applications. Full article
(This article belongs to the Special Issue Biomaterials, Implants and Scaffolds in Additive Manufacturing)
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Open AccessArticle
Effect of High Temperatures on the Impact Strength of Concrete Based on Recycled Aggregate Made of Heat-Resistant Cullet
Materials 2020, 13(2), 465; https://doi.org/10.3390/ma13020465 (registering DOI) - 18 Jan 2020
Abstract
The article presents results obtained during testing of concrete based on CEM I 42.5R Portland cement, fine and coarse aggregate, glass, volatile ash, and superplastifier. The concrete mixture was modified using filler consisting of bromosilicate heat resistant cullet. Recycled aggregate was added to [...] Read more.
The article presents results obtained during testing of concrete based on CEM I 42.5R Portland cement, fine and coarse aggregate, glass, volatile ash, and superplastifier. The concrete mixture was modified using filler consisting of bromosilicate heat resistant cullet. Recycled aggregate was added to the batch. Samples for the need of testing were produced as (100 × 100 × 100) mm cubes. Before commencing proper tests, samples have been heated within the temperature range of 20–800 °C. Tests carried out during the proper testing procedure included tests of compressive strength, elevated temperature, impact strength, as well as macroscopic tests of the contact area. The obtained test results have provided proof of there being a possibility of producing special concrete, modified by products obtained from heat resistant cullet. This type of is generally characterized by satisfactory performance parameters. The average compressive strength for concrete modified by a 10% of heat resistant cullet was determined as 43.6 MPa and 48.3 MPa respectively after 28 and 180 days of curing. Full article
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Open AccessArticle
Characteristics of the Molten Pool Temperature Field and Its Influence on the Preparation of a Composite Coating on a Ti6Al4V Alloy in the Micro-Arc Oxidation Process
Materials 2020, 13(2), 464; https://doi.org/10.3390/ma13020464 (registering DOI) - 18 Jan 2020
Abstract
In this study, the phase transition of secondary phase particles in a composite coating is used to estimate the temperature field of the molten pool on a Ti6Al4V alloy in the micro-arc oxidation (MAO) process. The behavior of the sparks and the molten [...] Read more.
In this study, the phase transition of secondary phase particles in a composite coating is used to estimate the temperature field of the molten pool on a Ti6Al4V alloy in the micro-arc oxidation (MAO) process. The behavior of the sparks and the molten pool during the MAO process was observed in real-time by a long-distance microscope. The microstructures and compositions of the composite coatings were studied by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results revealed that, for the temperature field distribution range of the molten pool in the active period, the lower limit is 2123 K and the upper limit is not lower than 3683 K. The reason for the multiphase coexistence is that the high-temperature phase is retained by the rapid cooling effect of the electrolyte, and the low-temperature phase is formed due to secondary phase transformation during the long active time of the molten pool temperature field. The strengthening mechanism of the composite coating prepared by adding the secondary phase particles is elemental doping rather than particle enhancement. The secondary phase particles are able to enter the composite coating by adhering to the surface during the cooling process. The secondary phase particles will then be wrapped into the coating in the next active period. Full article
(This article belongs to the Section Thin Films)
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Open AccessArticle
Fabrication and Tribological Properties of Mesocarbon Microbead–Cu Friction Composites
Materials 2020, 13(2), 463; https://doi.org/10.3390/ma13020463 (registering DOI) - 18 Jan 2020
Abstract
Graphite–metal composites have been used as friction materials owing to their self-lubricity, which is ascribed to the weak interlayer bonding of graphite. To overcome the shortage of graphite flake (GrF)-filled composites of having low tribological properties, graphite-Cu composites with mesocarbon microbead (MCMB) as [...] Read more.
Graphite–metal composites have been used as friction materials owing to their self-lubricity, which is ascribed to the weak interlayer bonding of graphite. To overcome the shortage of graphite flake (GrF)-filled composites of having low tribological properties, graphite-Cu composites with mesocarbon microbead (MCMB) as the solid lubricant are developed in this paper. The MCMB–Cu composites have a lower friction coefficient and wear rate than do the GrF–Cu composites taken as reference materials, exhibiting a better self-lubricating performance. Microstructural analysis indicates that the relatively weaker interlayer bonding of the MCMB, smooth interface between the MCMB and matrix, and more cementite formation thorough reaction of MCMB and iron are the key factors behind the enhanced tribological properties. In addition, both the friction coefficients and wear rates of the two groups of composites gradually decrease with the graphite content. This work opens an avenue for designing desirable graphite-based metal friction materials. Full article
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Open AccessArticle
Bionanotechnology: Silver Nanoparticles Supported on Bovine Bone Powder Used as Bactericide
Materials 2020, 13(2), 462; https://doi.org/10.3390/ma13020462 (registering DOI) - 18 Jan 2020
Abstract
Bionanotechnology is a relatively new term that implies the use of some biological material or organisms in order to prepare nanosystems or nanoparticles. This work presents the preparation and bactericide application of a sustainable nanometric system (silver nanoparticles) using a waste biological support [...] Read more.
Bionanotechnology is a relatively new term that implies the use of some biological material or organisms in order to prepare nanosystems or nanoparticles. This work presents the preparation and bactericide application of a sustainable nanometric system (silver nanoparticles) using a waste biological support (bovine bone powder). This system was prepared by the method of metallic salt reduction, using NaBH4 as reducing agent and AgNO3 as metallic salt. Two silver contents were analyzed, 1% and 5% weight. The latter was found to be more efficient than the former. Transmission electronic microscopy shows an average size of 10.5 ± 3.3 nm and quasi-sphere morphology. The antimicrobial assay shows that a 5% weight content of silver had a bactericide effect for Escherichia coli at 46.8 min of exposure. The minimum inhibitory concentration (MIC) of silver nanoparticles supported on bovine bone powder for Escherichia coli was 7.5 µg/mL. The biocomposite exhibits a specific antibacterial kinetics constant (k) of 0.1128 min−1 and decimal reduction time (DRT) of 20.39 min for Escherichia coli. Thus, it was concluded that a biocomposite was prepared with a biodegradable, waste, and low-cost support, under mild conditions (room temperature and atmospheric pressure) and using water as solvent. Full article
(This article belongs to the Special Issue Nanocomposites as Effective and Targeted Antibacterial Agents)
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Open AccessArticle
A Study of Characteristics of Aluminum Bronze Coatings Applied to Steel Using Additive Technologies
Materials 2020, 13(2), 461; https://doi.org/10.3390/ma13020461 (registering DOI) - 18 Jan 2020
Abstract
The influence of laser power on the microstructural, strength, and tribological characteristics of aluminum bronze coatings applied to steel by laser cladding was studied. It was found that with an increase in laser power, the morphology of the coating surface becomes more uniform [...] Read more.
The influence of laser power on the microstructural, strength, and tribological characteristics of aluminum bronze coatings applied to steel by laser cladding was studied. It was found that with an increase in laser power, the morphology of the coating surface becomes more uniform without extreme height differences. This study revealed that the coating microstructure corresponds to that of a composite material and consists of a bronze matrix and iron dendrites of different sizes (depending on the laser power). Such a microstructure affects the microhardness indices, which have a scatter of values over the coating thickness. There is a diffusion zone at the steel–bronze interface, which promotes adhesion of the matrix and coating materials. According to the results of tribological tests, the dry friction coefficient for the studied samples is in the range of 0.389–0.574. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessFeature PaperReview
Recent Development in Modeling of Coated Spherical Contact
Materials 2020, 13(2), 460; https://doi.org/10.3390/ma13020460 (registering DOI) - 18 Jan 2020
Abstract
Since a coated rough surface can be modeled as a collection of many spherical coated asperities, in order to understand the coated rough surface contact, it is required to first model a single coated spherical contact. This review paper presents a comprehensive summary [...] Read more.
Since a coated rough surface can be modeled as a collection of many spherical coated asperities, in order to understand the coated rough surface contact, it is required to first model a single coated spherical contact. This review paper presents a comprehensive summary of the coated spherical contact modeling and its experimental validation that was done mostly by the authors’ group at the Technion and published in the relevant literature. The coated spherical contact is considered under two loading modes, namely pure normal loading and combined normal and tangential loading. Based on the normally loaded spherical contact results, a coated rough surface contact modeling is presented. In addition, experimental results that show an interesting correlation with the coated spherical modeling are briefly discussed. Finally, some limited work on the bilayer/multilayer coated spherical contact is introduced. Full article
(This article belongs to the Special Issue Tribology: Friction and Wear of Engineering Materials)
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Open AccessArticle
Preparation and Mechanical Behavior of Ultra-High Strength Low-Carbon Steel
Materials 2020, 13(2), 459; https://doi.org/10.3390/ma13020459 (registering DOI) - 18 Jan 2020
Abstract
The low-carbon steel (~0.12 wt%) with complete martensite structure, obtained by quenching, was cold rolled to get the high-strength steel sheets. Then, the mechanical properties of the sheets were measured at different angles to the rolling direction, and the microstructural evolution of low-carbon [...] Read more.
The low-carbon steel (~0.12 wt%) with complete martensite structure, obtained by quenching, was cold rolled to get the high-strength steel sheets. Then, the mechanical properties of the sheets were measured at different angles to the rolling direction, and the microstructural evolution of low-carbon martensite with cold rolling reduction was observed. The results show that the hardness and the strength gradually increase with increasing rolling reduction, while the elongation and impact toughness obviously decrease. The strength of the sheets with the same rolling reduction are different at the angles of 0°, 45°, and 90° to the rolling direction. The tensile strength (elongation) along the rolling direction is higher than that in the other two directions, but the differences between them are not obvious. When the aging was performed at a low temperature, the strength of the initial martensite and deformed martensite increased with increasing aging time during the early stages of aging, followed by a gradual decrease with further aging. However, the elongation increases with increasing aging time. The change of hardness is consistent with that of strength for the cold-rolled martensite, while the hardness of the initial martensite decreases gradually with increasing aging time. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Steels)
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Open AccessArticle
TRIP Steels: A Multiscale Computational Simulation and Experimental Study of Heat Treatment and Mechanical Behavior
Materials 2020, 13(2), 458; https://doi.org/10.3390/ma13020458 (registering DOI) - 18 Jan 2020
Viewed by 73
Abstract
A multiscale investigation of the microstructure and the mechanical behavior of TRIP steels is presented. A multi-phase field model is employed to predict the microstructure of a low-alloy TRIP700 steel during a two-stage heat treatment. The resulting stability of retained austenite is examined [...] Read more.
A multiscale investigation of the microstructure and the mechanical behavior of TRIP steels is presented. A multi-phase field model is employed to predict the microstructure of a low-alloy TRIP700 steel during a two-stage heat treatment. The resulting stability of retained austenite is examined through the M s s temperature. The phase field results are experimentally validated and implemented into a model for the kinetics of retained austenite during strain-induced transformation. The kinetics model is calibrated by using experimental data for the evolution of the martensite volume fraction in uniaxial tension. The transformation kinetics model is used together with homogenization methods for non-linear composites to develop a constitutive model for the mechanical behavior of the TRIP steel. A methodology for the numerical integration of the constitutive equations is developed and the model is implemented in a general-purpose finite element program (ABAQUS). Necking of a bar in uniaxial tension is simulated and “forming limit diagrams” (FLDs) for sheets made of TRIP steels are calculated. The models developed provide an integrated simulation toolkit for the computer-assisted design of TRIP steels and can be used to translate mechanical property requirements into optimised microstructural characteristics and to identify the appropriate processing routes. Full article
Open AccessArticle
On the Compressive Response of Polymeric Cellular Materials
Materials 2020, 13(2), 457; https://doi.org/10.3390/ma13020457 (registering DOI) - 18 Jan 2020
Viewed by 71
Abstract
This paper presents a series of compression tests performed on a variety of high performance lightweight cellular materials conventionally used in energy absorption applications. Compressive tests were performed over a range of strain rates with a universal testing machine and a single stage [...] Read more.
This paper presents a series of compression tests performed on a variety of high performance lightweight cellular materials conventionally used in energy absorption applications. Compressive tests were performed over a range of strain rates with a universal testing machine and a single stage gas gun. Experimental results revealed a dependency of the mechanical properties on the polymeric precursor, density, infill topology and strain rates. The dynamic strength of the investigated materials was determined through a material parameter identification study via the finite element (FE) method. Numerical results matched well with the experimental results and revealed a substantial enhancement in the compressive strength of the tested material from quasi-static to dynamic loading regimes by as much as 87%. The strength of 3D printed polymers was superior with respect to the tested polymeric foams. On the other hand, polymeric foams showed higher efficiency and energy absorption ability. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle
Development and Application of Novel Sodium Silicate Microcapsule-Based Self-Healing Oil Well Cement
Materials 2020, 13(2), 456; https://doi.org/10.3390/ma13020456 (registering DOI) - 17 Jan 2020
Viewed by 105
Abstract
A majority of well integrity problems originate from cracks of oil well cement. To address the crack issues, bespoke sodium silicate microcapsules were used in this study for introducing autonomous crack healing ability to oil well cement under high-temperature service conditions at 80 [...] Read more.
A majority of well integrity problems originate from cracks of oil well cement. To address the crack issues, bespoke sodium silicate microcapsules were used in this study for introducing autonomous crack healing ability to oil well cement under high-temperature service conditions at 80 °C. Two types of sodium silicate microcapsule, which differed in their polyurea shell properties, were first evaluated on their suitability for use under the high temperature of 80 °C in the wellbore. Both types of microcapsules showed good thermal stability and survivability during mixing. The microcapsules with a more rigid shell were chosen over microcapsule with a more rubbery shell for further tests on the self-healing efficiency since the former had much less negative effect on the oil well cement strength. It was found that oil well cement itself showed very little healing capability when cured at 80 °C, but the addition of the microcapsules significantly promoted its self-healing performance. After healing for 7 days at 80 °C, the microcapsule-containing cement pastes achieved crack depth reduction up to ~58%, sorptivity coefficient reduction up to ~76%, and flexural strength regain up to ~27%. The microstructure analysis further confirmed the stability of microcapsules and their self-healing reactions upon cracking in the high temperature oil well cement system. These results provide a promising perspective for the development of self-healing microcapsule-based oil well cements. Full article
(This article belongs to the Special Issue Self-Healing and Smart Cementitious Construction Materials)
Open AccessArticle
The Influence of the Internal Forces of the Buckling Modes on the Load-Carrying Capacity of Composite Medium-Length Beams under Bending
Materials 2020, 13(2), 455; https://doi.org/10.3390/ma13020455 (registering DOI) - 17 Jan 2020
Viewed by 100
Abstract
The distribution of the internal forces corresponding to the individual buckling modes of lip-channel (LC) beams is investigated using the Semi Analytical Method (SAM) and the Finite Element Method (FEM). Channel section beams made of 8-layered GFRP (Glass Fiber Reinforced Polymer) laminate with [...] Read more.
The distribution of the internal forces corresponding to the individual buckling modes of lip-channel (LC) beams is investigated using the Semi Analytical Method (SAM) and the Finite Element Method (FEM). Channel section beams made of 8-layered GFRP (Glass Fiber Reinforced Polymer) laminate with three different layer arrangements were considered. The effect of the internal forces on the non-linear first-order coefficients corresponding to the interactive buckling was also studied. Moreover, distributions of the internal forces corresponded to the loading, leading to structure failure for which the load-carrying capacity was determined. The results indicated a high influence of the Nx internal force component on the buckling loads and load-carrying capacity of the LC-beams. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle
Using a Multi-Layer Stacked AlGaN/GaN Structure to Improve the Current Spreading Performance of Ultraviolet Light-Emitting Diodes
Materials 2020, 13(2), 454; https://doi.org/10.3390/ma13020454 (registering DOI) - 17 Jan 2020
Viewed by 94
Abstract
To obtain excellent current spreading performance of ultraviolet light-emitting diodes (UVLEDs), a 60-period stacked Si modulation-doped n-AlGaN/u-GaN structure is proposed to replace the traditional n-AlGaN structure. The high-resolution X-ray diffraction ω-scan rocking curves show that the periodic growth of AlGaN and GaN layers [...] Read more.
To obtain excellent current spreading performance of ultraviolet light-emitting diodes (UVLEDs), a 60-period stacked Si modulation-doped n-AlGaN/u-GaN structure is proposed to replace the traditional n-AlGaN structure. The high-resolution X-ray diffraction ω-scan rocking curves show that the periodic growth of AlGaN and GaN layers plays a positive role in reducing dislocation density. Compared with the conventional UV light-emitting diodes (LEDs), light emission micrographs of devices with a multi-layer stacked n-AlGaN/u-GaN structure reveal higher brightness and a more uniform distribution. In addition, the output power and external quantum efficiency under a 20-mA injection current are increased by 22% and 26.5%, respectively. Experimental and simulation results indicate that a multi-layer stacking structure can alleviate the current crowding effect in four ways: 1) a reduction in dislocation density; 2) replacement of quasi-two-dimensional electron transport with electronic bulk transport to enhance electron mobility; 3) an increase in electron concentration without improving the impurity concentration; and 4) a weakening of the electron scattering effect by reducing the impurity concentration. Full article
Open AccessArticle
Material Analysis and Molecular Dynamics Simulation for Cavitation Erosion and Corrosion Suppression in Water Hydraulic Valves
Materials 2020, 13(2), 453; https://doi.org/10.3390/ma13020453 - 17 Jan 2020
Viewed by 111
Abstract
In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the [...] Read more.
In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the appropriate selection, we conflicted properties that are vital for erosion and corrosion inhibitors, as well as the tribology in the sense of coefficient of friction. This article aimed to choose the best alternative polymer for coating on the selected substrate, that is, Cr2O3, Al2O3, Ti2O3. By applying PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations), the best polymer obtained with an analyzed performance attribute is Polytetrafluoroethylene (PTFE) that comes up with higher outranking (0.5932052). A Molecular Dynamics (MD) simulation was conducted to identify the stronger bonding with the regards of the better cleave plane between Polytetrafluoroethylene (PTFE) and the selected substrate. Polytetrafluoroethylene (PTFE)/Al2O3 cleaved in (010) plane was observed to be the strongest bond in terms of binding energy (3188 kJ/mol) suitable for further studies. Full article
(This article belongs to the Special Issue Advanced Coatings for Corrosion Protection)
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Open AccessArticle
Cytotoxicity of Self-Etch Versus Etch-and-Rinse Dentin Adhesives: A Screening Study
Materials 2020, 13(2), 452; https://doi.org/10.3390/ma13020452 - 17 Jan 2020
Viewed by 106
Abstract
Six dentin adhesives were tested in vitro regarding their cytotoxicity on human fibroblasts. The adhesives Hybrid Bond, One-up Bond F Plus, AdheSE, Clearfil SE Bond, Optibond Solo Plus and Syntac were eluted with culture medium as single or sequentially applied adhesive part for [...] Read more.
Six dentin adhesives were tested in vitro regarding their cytotoxicity on human fibroblasts. The adhesives Hybrid Bond, One-up Bond F Plus, AdheSE, Clearfil SE Bond, Optibond Solo Plus and Syntac were eluted with culture medium as single or sequentially applied adhesive part for 24 h. 75 Petri dishes were produced per group. They were evaluated triangulated, comprising the quantitative evaluation (105 ones) to determine “viable”, “dead” and “debris” cells with the use of a cell-counter and the reactivity index was also identified based on the qualitative assessment (420 ones). One-up Bond F Plus, AdheSE and Clearfil SE Bond showed a statistical difference of viable cells to the cell control. For One-up Bond F Plus, statistically, differences compared to hybrid bond and Syntac were also found. All the adhesives except One-up Bond F Plus showed significant differences between single and sequentially applied adhesive part regarding the quantitative evaluation. The test material showed a moderate grade of cytotoxicity. As a result, a statistically significant difference of the cytotoxicity between the self-etch and etch-and-rinse adhesives cannot be demonstrated regarding the qualitative evaluation and the reactivity index, but the differences between sequentially applied and single applied components can be proved. Full article
(This article belongs to the collection Dental Biomaterials)
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Open AccessArticle
Strategy of Residual Stress Determination on Selective Laser Melted Al Alloy Using XRD
Materials 2020, 13(2), 451; https://doi.org/10.3390/ma13020451 - 17 Jan 2020
Viewed by 92
Abstract
Selective laser melting (SLM) is known to generate large and anisotropic residual stresses in the samples. Accurate measurement of residual stresses on SLM-produced samples is essential for understanding the residual stress build-up mechanism during SLM, while a dramatic fluctuation can be observed in [...] Read more.
Selective laser melting (SLM) is known to generate large and anisotropic residual stresses in the samples. Accurate measurement of residual stresses on SLM-produced samples is essential for understanding the residual stress build-up mechanism during SLM, while a dramatic fluctuation can be observed in the residual stress values reported in the literature. On the basis of studying the influence of surface roughness on residual stress measured using X-ray diffraction (XRD), we propose a procedure coupling XRD technique with pretreatment consisting of mechanical polishing and chemical etching. The results highlight that residual stresses measured using XRD on as-built SLM-produced samples with high surface roughness are significantly lower than those measured on samples with finished surface, which is due to the stress relaxation on the spiked surface of as-built samples. Surface distribution of residual stresses and the effect of scanning strategy were systematically investigated for SLM-produced AlSi10Mg samples. Microstructural morphology was observed at the interface between sample and building platform and was linked to the surface distribution of residual stresses. This procedure can help us accurately measure the residual stresses in SLM-produced samples and thus better understand its build-up mechanism during the SLM process. Full article
(This article belongs to the Special Issue Additively Manufactured Metallic Materials)
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Open AccessArticle
Liquid Regions of Lanthanum-Bearing Aluminosilicates
Materials 2020, 13(2), 450; https://doi.org/10.3390/ma13020450 - 17 Jan 2020
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Abstract
The Al2O3-SiO2, La2O3-Al2O3, and La2O3-SiO2 binary phase diagrams were estimated by Redlich–Kister expression. La4.67Si3O13 (=La4.67(SiO4) [...] Read more.
The Al2O3-SiO2, La2O3-Al2O3, and La2O3-SiO2 binary phase diagrams were estimated by Redlich–Kister expression. La4.67Si3O13 (=La4.67(SiO4)3O) was introduced to improve the existing phase diagrams. The Al2O3-SiO2-La2O3 ternary phase diagram extrapolated by Kohler method was optimized. Then, the liquidus of Al2O3-SiO2-La2O3 system at 1600 °C was compared with Al2O3-SiO2-RE2O3 (RE = Rare Earth Elements) systems and experimental results in other literature. The high temperature experiments were conducted in the tube furnace at 1500 °C. Then the field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) were employed to verify the calculated liquid region and precipitates phase at 1500 °C. Moreover, the liquidus of binary systems were compared with FactSage results and experiments. The optimized ternary phase diagram shows the relatively reliable region of liquid phase, and it is significant to the seal glass of solid oxide fuel cells and other fields being related to RE containing silicates. Full article
(This article belongs to the Special Issue Rare Earth Oxides and Their Applications)
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Open AccessFeature PaperArticle
Cloaking In-Plane Elastic Waves with Swiss Rolls
Materials 2020, 13(2), 449; https://doi.org/10.3390/ma13020449 - 17 Jan 2020
Viewed by 91
Abstract
We propose a design of cylindrical cloak for coupled in-plane shear waves consisting of concentric layers of sub-wavelength resonant stress-free inclusions shaped as Swiss rolls. The scaling factor between inclusions’ sizes is according to Pendry’s transform. Unlike the hitherto known situations, the present [...] Read more.
We propose a design of cylindrical cloak for coupled in-plane shear waves consisting of concentric layers of sub-wavelength resonant stress-free inclusions shaped as Swiss rolls. The scaling factor between inclusions’ sizes is according to Pendry’s transform. Unlike the hitherto known situations, the present geometric transform starts from a Willis medium and further assumes that displacement fields u in original medium and u in transformed medium remain unaffected ( u = u ). This breaks the minor symmetries of the rank-4 and rank-3 tensors in the Willis equation that describe the transformed effective medium. We achieve some cloaking for a shear polarized source at specific, resonant sub-wavelength, frequencies, when it is located in close proximity to a clamped obstacle surrounded by the structured cloak. The structured medium approximating the effective medium allows for strong Willis coupling, notwithstanding potential chiral elastic effects, and thus mitigates roles of Willis and Cosserat media in the achieved elastodynamic cloaking. Full article
(This article belongs to the Special Issue Advances in Mechanical Metamaterials)
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Open AccessArticle
Micro-Structure Modelling and Electrical Properties Analysis of PZT Matrix Ferroelectric Composites
Materials 2020, 13(2), 448; https://doi.org/10.3390/ma13020448 - 17 Jan 2020
Viewed by 124
Abstract
PZT matrix ferroelectric composite is an important research topic in material science because of its many practical, industrial, and scientific applications. Materials with high dielectric permittivity are used to manufacture electronic devices, particularly capacitors and dynamic random access memory (DRAM). Therefore, the development [...] Read more.
PZT matrix ferroelectric composite is an important research topic in material science because of its many practical, industrial, and scientific applications. Materials with high dielectric permittivity are used to manufacture electronic devices, particularly capacitors and dynamic random access memory (DRAM). Therefore, the development of reliable and efficient micro models to be utilized in analyzing electrical properties can be of great value in accelerating research in this field. In this paper, a 3D microstructure model for PZT matrix ferroelectric composites has been developed and adopted the finite element method (FEM) to calculate the dielectric constant. The microscopy parameters of developed microstructure model are acquired based on the real composites from X-ray (micro-) diffraction and stereological method. The dielectric constant of different volume ratios of PZT matrix ferroelectric composites can be calculated by accurately controlling the volume of Ferrite particles. At the point of validation, the proposed approach makes visual and numeric comparisons between the morphology of the real microstructure and the model generated by the proposed technique. The simulation results by our method was essentially in agreement with experimental results in other literature. Simulation Experimental results also demonstrate that the dielectric constant of PZT matrix ferroelectric composites is significantly changed while the volume ratio of high dielectric phase particles was below 20%. PZT matrix ferroelectric composites Consequently, this method can be easily extended to composites preparation. Full article
(This article belongs to the Section Electronic Materials)
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Open AccessFeature PaperArticle
Diffusion Reflection Measurements of Antibodies Conjugated to Gold Nanoparticles as a Method to Identify Cutaneous Squamous Cell Carcinoma Borders
Materials 2020, 13(2), 447; https://doi.org/10.3390/ma13020447 - 17 Jan 2020
Viewed by 108
Abstract
Diffusion reflectance spectroscopy measurements targeted with gold nanoparticles (GNPs) can identify residual cutaneous squamous cell carcinoma (SCC) in excision borders. Human SCC specimens were stained with hematoxylin and eosin to identify tumor borders, and reflected onto an unstained deparaffinized section. Diffusion reflection of [...] Read more.
Diffusion reflectance spectroscopy measurements targeted with gold nanoparticles (GNPs) can identify residual cutaneous squamous cell carcinoma (SCC) in excision borders. Human SCC specimens were stained with hematoxylin and eosin to identify tumor borders, and reflected onto an unstained deparaffinized section. Diffusion reflection of three sites (normal and SCC) were measured before and after GNPs targeting. Hyperspectral imaging showed a mean of 2.5 sites with tumor per specimen and 1.2 tumor-free (p < 0.05, t-test). GNPs were detected in 25/30 tumor sites (sensitivity 83.3%, false-negative rate 16.6%) and 12/30 non-tumor sites (specificity 60%, false-positive rate 40%). This study verifies the use of nanotechnology in identifying SCC tumor margins. Diffusion reflection scanning has high sensitivity for detecting the residual tumor. Full article
(This article belongs to the Special Issue Nanoparticles for Biological Imaging and Treatment Applications)
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Open AccessArticle
Facile Synthesis of Sandwich-Like rGO/CuS/Polypyrrole Nanoarchitectures for Efficient Electromagnetic Absorption
Materials 2020, 13(2), 446; https://doi.org/10.3390/ma13020446 - 17 Jan 2020
Viewed by 109
Abstract
Currently, electromagnetic pollution management has gained much attention due to the various harmful effects on wildlife and human beings. Electromagnetic absorbers can convert energy from electromagnetic waves into thermal energy. Previous reports have demonstrated that reduced graphene oxide (rGO) makes progress in the [...] Read more.
Currently, electromagnetic pollution management has gained much attention due to the various harmful effects on wildlife and human beings. Electromagnetic absorbers can convert energy from electromagnetic waves into thermal energy. Previous reports have demonstrated that reduced graphene oxide (rGO) makes progress in the electromagnetic absorption (EA) field. But the high value of permittivity of rGO always mismatches the impedance which results in more electromagnetic wave reflection on the surface. In this work, sandwich-like rGO/CuS/polypyrrole (PPy) nanoarchitectures have been synthesized by a facile two-step method. The experimental result has shown that a paraffin composite containing 10 wt.% of rGO/CuS/PPy could achieve an enhanced EA performance both in bandwidth and intensity. The minimum reflection loss (RL) value of −49.11 dB can be reached. Furthermore, the effective bandwidth can cover 4.88 GHz. The result shows that the as-prepared rGO/CuS/PPy nanoarchitectures will be a promising EA material. Full article
Open AccessArticle
High-Performance Temperature Sensors Based on Dual 4H-SiC JBS and SBD Devices
Materials 2020, 13(2), 445; https://doi.org/10.3390/ma13020445 - 17 Jan 2020
Viewed by 128
Abstract
Schottky diode-based temperature sensors are the most common commercially available temperature sensors, and they are attracting increasing interest owing to their higher Schottky barrier height compared to their silicon counterparts. Therefore, this paper presents a comparison of the thermal sensitivity variation trend in [...] Read more.
Schottky diode-based temperature sensors are the most common commercially available temperature sensors, and they are attracting increasing interest owing to their higher Schottky barrier height compared to their silicon counterparts. Therefore, this paper presents a comparison of the thermal sensitivity variation trend in temperature sensors, based on dual 4H-SiC junction barrier Schottky (JBS) diodes and Schottky barrier diodes (SBDs). The forward bias current–voltage characteristics were acquired by sweeping the DC bias voltage from 0 to 3 V. The dual JBS sensor exhibited a higher peak sensitivity (4.32 mV/K) than the sensitivity exhibited by the SBD sensor (2.85 mV/K), at temperatures ranging from 298 to 573 K. The JBS sensor exhibited a higher ideality factor and barrier height owing to the p–n junction in JBS devices. The developed sensor showed good repeatability, maintaining a stable output over several cycles of measurements on different days. It is worth noting that the ideality factor and barrier height influenced the forward biased voltage, leading to a higher sensitivity for the JBS device compared to the SBD device. This allows the JBS device to be suitably integrated with SiC power management and control circuitry to create a sensing module capable of working at high temperatures. Full article
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Open AccessReview
Research Progress on the Collaborative Drag Reduction Effect of Polymers and Surfactants
Materials 2020, 13(2), 444; https://doi.org/10.3390/ma13020444 - 17 Jan 2020
Viewed by 104
Abstract
Polymer additives and surfactants as drag reduction agents have been widely used in the field of fluid drag reduction. Polymer additives can reduce drag effectively with only a small amount, but they degrade easily. Surfactants have an anti-degradation ability. This paper categorizes the [...] Read more.
Polymer additives and surfactants as drag reduction agents have been widely used in the field of fluid drag reduction. Polymer additives can reduce drag effectively with only a small amount, but they degrade easily. Surfactants have an anti-degradation ability. This paper categorizes the mechanism of drag reducing agents and the influencing factors of drag reduction characteristics. The factors affecting the degradation of polymer additives and the anti-degradation properties of surfactants are discussed. A mixture of polymer additive and surfactant has the characteristics of high shear resistance, a lower critical micelle concentration (CMC), and a good drag reduction effect at higher Reynolds numbers. Therefore, this paper focuses more on a drag reducing agent mixed with a polymer and a surfactant, including the mechanism model, drag reduction characteristics, and anti-degradation ability. Full article
(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)
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Open AccessArticle
Sulfur-Deficient Porous SnS2−x Microflowers as Superior Anode for Alkaline Ion Batteries
Materials 2020, 13(2), 443; https://doi.org/10.3390/ma13020443 - 17 Jan 2020
Viewed by 128
Abstract
SnS2 as a high energy anode material has attracted extensive research interest recently. However, the fast capacity decay and low rate performance in alkaline-ion batteries associated with repeated volume variation and low electrical conductivity plague them from practical application. Herein, we propose [...] Read more.
SnS2 as a high energy anode material has attracted extensive research interest recently. However, the fast capacity decay and low rate performance in alkaline-ion batteries associated with repeated volume variation and low electrical conductivity plague them from practical application. Herein, we propose a facile method to solve this problem by synthesizing porous SnS2 microflowers with in-situ formed sulfur vacancies. The flexible porous nanosheets in the three-dimensional flower-like nanostructure provide facile strain relaxation to avoid stress concentration during the volume changes. Rich sulfur vacancies and porous structure enable the fast and efficient electron transport. The porous SnS2−x microflowers exhibit outstanding performance for lithium ion battery in terms of high capacity (1375 mAh g−1 at 100 mA g−1) and outstanding rate capability (827 mA h g−1 at high rate of 2 A g−1). For sodium ion battery, a high capacity (~522 mAh g−1) can be achieved at 5 A g−1 after 200 cycles for SnS2−x microflowers. The rational design in nanostructures, as well as the chemical compositions, might create new opportunities in designing the new architecture for highly efficient energy storage devices. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle
Evaluation of Strength Development in Concrete with Ground Granulated Blast Furnace Slag Using Apparent Activation Energy
Materials 2020, 13(2), 442; https://doi.org/10.3390/ma13020442 - 17 Jan 2020
Viewed by 129
Abstract
Ground granulated blast furnace slag (GGBFS) conventionally has been incorporated with ordinary Portland cement (OPC) owing to reduce the environmental load and enhance the engineering performance. Concrete with GGBFS shows different strength development of normal concrete, but sensitive, to exterior condition. Thus, a [...] Read more.
Ground granulated blast furnace slag (GGBFS) conventionally has been incorporated with ordinary Portland cement (OPC) owing to reduce the environmental load and enhance the engineering performance. Concrete with GGBFS shows different strength development of normal concrete, but sensitive, to exterior condition. Thus, a precise strength evaluation technique based on a quantitative model like full maturity model is required. Many studies have been performed on strength development of the concrete using equivalent age which is based on the apparent activation energy. In this process, it considers the effect of time and temperature simultaneously. However, the previous models on the apparent activation energy of concrete with mineral admixtures have limitation, and they have not considered the effect of temperature on strength development. In this paper, the apparent activation energy with GGBFS replacement ratio was calculated through several experiments and used to predict the compressive strength of GGBFS concrete. Concrete and mortar specimens with 0.6 water/binder ratio, and 0 to 60% GGBFS replacement were prepared. The apparent activation energy (Ea) was experimentally derived considering three different curing temperatures. Thermodynamic reactivity of GGBFS mixed concrete at different curing temperature was applied to evaluate the compressive strength model, and the experimental results were in good agreement with the model. The results show that when GGBFS replacement ratio was increased, there was a delay in compressive strength. Full article
(This article belongs to the Special Issue Supplementary Cementitious Materials in Concrete)
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Open AccessCommunication
Combining Organic and Inorganic Wastes to Form Metal–Organic Frameworks
Materials 2020, 13(2), 441; https://doi.org/10.3390/ma13020441 - 17 Jan 2020
Viewed by 147
Abstract
This paper reports a simple method to recycle plastic-bottle and Li-ion-battery waste in one process by forming valuable coordination polymers (metal–organic frameworks, MOFs). Poly(ethylene terephthalate) from plastic bottles was depolymerized to produce an organic ligand source (terephthalate), and Li-ion batteries were dissolved as [...] Read more.
This paper reports a simple method to recycle plastic-bottle and Li-ion-battery waste in one process by forming valuable coordination polymers (metal–organic frameworks, MOFs). Poly(ethylene terephthalate) from plastic bottles was depolymerized to produce an organic ligand source (terephthalate), and Li-ion batteries were dissolved as a source of metals. By mixing both dissolution solutions together, selective precipitation of an Al-based MOF, known as MIL-53 in the literature, was observed. This material can be recovered in large quantities from waste and presents similar properties of purity and porosity to as-synthesis MIL-53. This work illustrates the opportunity to form hybrid porous materials by combining different waste streams, laying the foundations for an achievable integrated circular economy from different waste cycle treatments (for batteries and plastics). Full article
(This article belongs to the Special Issue Innovative Materials for Energy and Recycling)
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Open AccessArticle
Dual and Multi-Emission Hybrid Micelles Realized through Coordination-Driven Self-Assembly
Materials 2020, 13(2), 440; https://doi.org/10.3390/ma13020440 - 16 Jan 2020
Viewed by 217
Abstract
Building novel functional nanomaterials with a polymer is one of the most dynamic research fields at present. Here, three amphiphilic block copolymers of 8-hydroxyquinoline derivative motifs (MQ) with excellent coordination function were synthesized by Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) polymerization. The coordination [...] Read more.
Building novel functional nanomaterials with a polymer is one of the most dynamic research fields at present. Here, three amphiphilic block copolymers of 8-hydroxyquinoline derivative motifs (MQ) with excellent coordination function were synthesized by Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) polymerization. The coordination micelles were prepared through the self-assembly process, which the MQ motifs were dispersed in the hydrophobic polystyrene (PSt) blocks and hydrophilic Poly(N-isopropylacrylamide (PNIPAM)) blocks, respectively. The dual-emission micelles including the intrinsic red light emission of quantum dots (QDs) and the coordination green light emission of Zn2+-MQ complexes were built by introducing the CdSe/ZnS and CdTe/ZnS QDs in the core and shell precisely in the coordination micelles through the coordination-driven self-assembly process. Furthermore, based on the principle of three primary colors that produce white light emission, vinyl carbazole units (Polyvinyl Carbazole, PVK) with blue light emission were introduced into the hydrophilic PNIPAM blocks to construct the white light micelles that possess special multi-emission properties in which the intrinsic red light emission of QDs, the coordination green light of Zn2+-MQ complexes, and the blue light emission of PVK were synergized. The dual and multi-emission hybrid micelles have great application prospects in ratiometric fluorescent probes and biomarkers. Full article
(This article belongs to the Section Materials Chemistry)
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Open AccessArticle
Model-based Residual Stress Design in Multiphase Seamless Steel Tubes
Materials 2020, 13(2), 439; https://doi.org/10.3390/ma13020439 - 16 Jan 2020
Viewed by 193
Abstract
Residual stresses in quenched seamless steel tubes highly depend on the cooling conditions to which the tubes have been subjected. The design aspect of how to use controlled cooling strategies in multiphase steel tubes to achieve certain residual stress and phase configurations is [...] Read more.
Residual stresses in quenched seamless steel tubes highly depend on the cooling conditions to which the tubes have been subjected. The design aspect of how to use controlled cooling strategies in multiphase steel tubes to achieve certain residual stress and phase configurations is discussed. In an experimentally validated finite element (FE) model considering a coupled evolution of martensite and bainite, three cooling strategies are tested for a low-alloyed 0.25 wt.% C steel tube. The strategies are (i) external cooling only, (ii) internal and external cooling for low residual stresses in a mainly martensitic tube, and (iii) internal and external cooling with low cooling rate for a mainly bainitic tube. The strategies represent design cases, where low residual stresses with different phase compositions are provoked, in order to show the potential of numerical analysis for residual stress and property design. It can be concluded that, for the investigated steel class, intense external cooling leads to a characteristic residual stress profile regardless of the dimension. A combination of external and internal cooling allows a more flexible design of residual stress and phase distribution by choosing different cooling parameters (i.e., water amount and cooling times). In general, lower cooling rates lead to lower thermal misfit strains, and thus less plasticity and lower residual stresses. Full article
(This article belongs to the Section Materials Simulation and Design)
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Open AccessArticle
Engineering Gels with Time-Evolving Viscoelasticity
Materials 2020, 13(2), 438; https://doi.org/10.3390/ma13020438 - 16 Jan 2020
Viewed by 190
Abstract
From a mechanical point of view, a native extracellular matrix (ECM) is viscoelastic. It also possesses time-evolving or dynamic behaviour, since pathophysiological processes such as ageing alter their mechanical properties over time. On the other hand, biomaterial research on mechanobiology has focused mainly [...] Read more.
From a mechanical point of view, a native extracellular matrix (ECM) is viscoelastic. It also possesses time-evolving or dynamic behaviour, since pathophysiological processes such as ageing alter their mechanical properties over time. On the other hand, biomaterial research on mechanobiology has focused mainly on the development of substrates with varying stiffness, with a few recent contributions on time- or space-dependent substrate mechanics. This work reports on a new method for engineering dynamic viscoelastic substrates, i.e., substrates in which viscoelastic parameters can change or evolve with time, providing a tool for investigating cell response to the mechanical microenvironment. In particular, a two-step (chemical and enzymatic) crosslinking strategy was implemented to modulate the viscoelastic properties of gelatin hydrogels. First, gels with different glutaraldehyde concentrations were developed to mimic a wide range of soft tissue viscoelastic behaviours. Then their mechanical behaviour was modulated over time using microbial transglutaminase. Typically, enzymatically induced mechanical alterations occurred within the first 24 h of reaction and then the characteristic time constant decreased although the elastic properties were maintained almost constant for up to seven days. Preliminary cell culture tests showed that cells adhered to the gels, and their viability was similar to that of controls. Thus, the strategy proposed in this work is suitable for studying cell response and adaptation to temporal variations of substrate mechanics during culture. Full article
(This article belongs to the Special Issue Soft Materials)
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