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Materials, Volume 15, Issue 11 (June-1 2022) – 302 articles

Cover Story (view full-size image): Solid oxide fuel cell (SOFC) anode materials require mixed ionic and electronic conduction properties. This is achieved in perovskite oxides with SrMo1−xAlxO3−δ composition. A neutron powder diffraction investigation showed that they are cubic (s.g. Pm-3m), displaying a random distribution of Mo and Al cations over the octahedral sites of the structure. This results in conspicuous amounts of oxygen vacancies in the perovskite, detected by neutrons at the working conditions of a SOFC. Oxygen deficiency is essential to induce ionic diffusion. Indeed, these defective perovskites outperform as anode materials in test fuel cells, providing substantial output power densities. They are, thus, a good replacement of conventional biphasic cermet anodes in SOFC. View this paper
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Article
Study on the Fracture Toughness of Softwood and Hardwood Estimated by Boundary Effect Model
Materials 2022, 15(11), 4039; https://doi.org/10.3390/ma15114039 - 06 Jun 2022
Viewed by 405
Abstract
The tensile strength and fracture toughness of softwood and hardwood are measured by the Boundary Effect Model (BEM). The experimental results of single-edge notched three-point bending tests indicate that the BEM is an appropriate method to estimate the fracture toughness of the present [...] Read more.
The tensile strength and fracture toughness of softwood and hardwood are measured by the Boundary Effect Model (BEM). The experimental results of single-edge notched three-point bending tests indicate that the BEM is an appropriate method to estimate the fracture toughness of the present fibrous and porous woods. In softwood with alternating earlywood and latewood layers, the variation in the volume percentage of different layers in a small range has no obvious influence on the mechanical properties of the materials. In contrast, the hardwood presents much higher tensile strength and fracture toughness simultaneously due to its complicated structure with crossed arrangement of the fibers and rays and big vessels diffused in the fibers. The present research findings are expected to provide a fundamental insight into the design of high-performance bionic materials with a highly fibrous and porous structure. Full article
(This article belongs to the Special Issue Toughening Mechanisms in Natural Materials and Bioinspired Designs)
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Article
Methodologyfor Molecular Dynamics Simulation of Plastic Deformation of a Nickel/Graphene Composite
Materials 2022, 15(11), 4038; https://doi.org/10.3390/ma15114038 - 06 Jun 2022
Viewed by 348
Abstract
In this study, some features of molecular dynamics simulation for evaluating the mechanical properties of a Ni/graphene composite and analyzing the effect of incremental and dynamic tensile loading on its deformation are discussed. A new structural type of the composites is considered: graphene [...] Read more.
In this study, some features of molecular dynamics simulation for evaluating the mechanical properties of a Ni/graphene composite and analyzing the effect of incremental and dynamic tensile loading on its deformation are discussed. A new structural type of the composites is considered: graphene network (matrix) with metal nanoparticles inside. Two important factors affecting the process of uniaxial tension are studied: tension strain rate (5 ×103 ps1 and 5 ×104 ps1) and simulation temperature (0 and 300 K). The results show that the strain rate affects the ultimate tensile strength under tension: the lower the strain rate, the lower the critical values of strain. Tension at room temperature results in lower ultimate tensile strength in comparison with simulation at a temperature close to 0 K, at which ultimate tensile strength is closer to theoretical strength. Both simulation techniques (dynamic and incremental) can be effectively used for such a study and result in almost similar behavior. Fabrication technique plays a key role in the formation of the composite with low anisotropy. In the present work, uniaxial tension along three directions shows a big difference in the composite strength. It is shown that the ultimate tensile strength of the Ni/graphene composite is close to that of pure crumpled graphene, while the ductility of crumpled graphene with metal nanoparticles inside is two times higher. The obtained results shed the light on the simulation methodology which should be used for the study of the deformation behavior of carbon/metal nanostructures. Full article
(This article belongs to the Special Issue Current and Future Trends in Carbon-Based Materials)
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Article
Design for Additive Manufacturing and Investigation of Surface-Based Lattice Structures for Buckling Properties Using Experimental and Finite Element Methods
Materials 2022, 15(11), 4037; https://doi.org/10.3390/ma15114037 - 06 Jun 2022
Viewed by 381
Abstract
Additive Manufacturing (AM) is rapidly evolving due to its unlimited design freedom to fabricate complex and intricate light-weight geometries with the use of lattice structure that have potential applications including construction, aerospace and biomedical applications, where mechanical properties are the prime focus. Buckling [...] Read more.
Additive Manufacturing (AM) is rapidly evolving due to its unlimited design freedom to fabricate complex and intricate light-weight geometries with the use of lattice structure that have potential applications including construction, aerospace and biomedical applications, where mechanical properties are the prime focus. Buckling instability in lattice structures is one of the main failure mechanisms that can lead to major failure in structural applications that are subjected to compressive loads, but it has yet to be fully explored. This study aims to investigate the effect of surface-based lattice structure topologies and structured column height on the critical buckling load of lattice structured columns. Four different triply periodic minimal surface (TPMS) lattice topologies were selected and three design configurations (unit cells in x, y, z axis), i.e., 2 × 2 × 4, 2 × 2 × 8 and 2 × 2 × 16 column, for each structure were designed followed by printing using HP MultiJet fusion. Uni-axial compression testing was performed to study the variation in critical buckling load due to change in unit cell topology and column height. The results revealed that the structured column possessing Diamond structures shows the highest critical buckling load followed by Neovius and Gyroid structures, whereas the Schwarz-P unit cell showed least resistance to buckling among the unit cells analyzed in this study. In addition to that, the Diamond design showed a uniform decrease in critical buckling load with a column height maximum of 5193 N, which makes it better for applications in which the column’s height is relatively higher while the Schwarz-P design showed advantages for low height column maximum of 2271 N. Overall, the variations of unit cell morphologies greatly affect the critical buckling load and permits the researchers to select different lattice structures for various applications as per load/stiffness requirement with different height and dimensions. Experimental results were validated by finite element analysis (FEA), which showed same patterns of buckling while the numerical values of critical buckling load show the variation to be up to 10%. Full article
(This article belongs to the Special Issue Mechanical Metamaterials and Their Applications)
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Article
Relevant Aspects of Titanium and Zirconia Dental Implants for Their Fatigue and Osseointegration Behaviors
Materials 2022, 15(11), 4036; https://doi.org/10.3390/ma15114036 - 06 Jun 2022
Viewed by 381
Abstract
Osseointegration capacity and good mechanical behavior are key to the success of the dental implant. In many investigations, comparisons of properties are made using different dental implant designs and therefore the results can be influenced by the macrodesign of the dental implant. In [...] Read more.
Osseointegration capacity and good mechanical behavior are key to the success of the dental implant. In many investigations, comparisons of properties are made using different dental implant designs and therefore the results can be influenced by the macrodesign of the dental implant. In this work, studies were carried out with the same dental implant model using different roughness and different materials—commercially pure titanium (grade 4) and zirconia. For this purpose, 80 smooth passivated titanium (Ti), 80 smooth zirconia (ZrO2), and 80 rough passivated titanium (Ti-R) dental implants were used. The samples were characterized by their roughness, wettability, surface energy, residual stresses, and fatigue behavior. The implants were implanted in minipigs for 4 and 12 weeks. The animals were sacrificed, and histological studies were carried out to determine the osseointegration parameters for each of the implantation times. Ti and ZrO2 dental implants have very similar wettability and surface energy properties. However, the roughness causes a decrease in the hydrophilic character and a decrease of the total surface energy and especially the dispersive component, while the polar component is higher. Due to the compressive residual stresses of alumina sandblasting, the rough dental implant has the best fatigue behavior, followed by Ti and due to the lack of toughness and rapid crack propagation the ZrO2 implants have the worst fatigue behavior. The bone index contact (BIC) values for 4 weeks were around 25% for Ti, 32% for ZrO2, and 45% for Ti-R. After 12 weeks the Ti dental implants increased to 42%, for Ti, 43% for ZrO2, and an important increase to 76% was observed for Ti-R implants. In vivo results showed that the key factor that improves osseointegration is roughness. There was no significant difference between ZrO2 and Ti implants without sandblasting. Full article
(This article belongs to the Special Issue Ti Alloys for Dental Implant Applications-Series II)
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Article
Experimental Evaluations on Seismic Performances of Porcelain and GFRP Composite UHV GIS Bushings
Materials 2022, 15(11), 4035; https://doi.org/10.3390/ma15114035 - 06 Jun 2022
Viewed by 373
Abstract
To evaluate the seismic performances of the ultra-high voltage (UHV) gas-insulated switchgear (GIS) bushings made by porcelain and glass fiber reinforced polymer (GFRP) composite materials, shaking table tests were conducted on the two full-scale GIS bushings. The dynamic characteristics and seismic responses of [...] Read more.
To evaluate the seismic performances of the ultra-high voltage (UHV) gas-insulated switchgear (GIS) bushings made by porcelain and glass fiber reinforced polymer (GFRP) composite materials, shaking table tests were conducted on the two full-scale GIS bushings. The dynamic characteristics and seismic responses of the two UHV GIS bushings were obtained. The experimental results indicated that the two UHV GIS bushings meet the seismic requirements in the corresponding standards. The supporting frame and bus canister amplify the seismic responses of the UHV GIS bushings. Under earthquakes, the GFRP composite UHV GIS bushing is safer than the porcelain bushing. In the seismic design of the electrical substation, the large seismic displacement of the GFRP composite UHV GIS bushings should be considered. Full article
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Article
Experimental Study on the Mix Ratio of Restored Heritage Building Adobe
Materials 2022, 15(11), 4034; https://doi.org/10.3390/ma15114034 - 06 Jun 2022
Viewed by 393
Abstract
The reciprocating action of the external environment gradually reduces the mechanical properties and water stability of original heritage buildings, resulting in the gradual loss of their cultural value. In this paper, the adobe for the construction of raw soil and cultural relics in [...] Read more.
The reciprocating action of the external environment gradually reduces the mechanical properties and water stability of original heritage buildings, resulting in the gradual loss of their cultural value. In this paper, the adobe for the construction of raw soil and cultural relics in western Henan is taken as the research object. The local plain soil is used as the raw material, and the adobe samples are prepared with modified materials such as quicklime and sodium methyl silicate, in order to improve its mechanical properties and water stability. The degree of correlation between the compressive strength, capillary water absorption, pH value, particle size distribution, and the electrical conductivity of modified raw adobe, as well as the modification mechanism of the microstructure, was studied. The results show that the addition of quicklime and sodium methyl silicate can enhance the compressive strength and water resistance of the modified raw adobe, and the optimum dosage is 1.5% sodium methyl silicate; with the increase of the curing age, the compressive strength of the single-mixed quicklime sample, the single mixed sodium methyl silicate samples, and the composite sample were increased by 1.94 times, 12.6 times and 2.61 times, respectively, compared with the plain soil samples, and with the increase of compressive strength, the pH, conductivity and capillary water absorption of the samples decreased continuously. It is evident from the particle gradation test and SEM images that the internal pores of the samples in the modified group become smaller, and the particle structure of the sample doped with sodium methyl silicate is the densest. The results of the study provide support for the restoration of the soil and cultural-relic buildings. Full article
(This article belongs to the Section Construction and Building Materials)
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Article
Chemical Composition and Related Properties of Lime (Tilia cordata Mill.) Bark and Wood as Affected by Tree Growth Conditions
Materials 2022, 15(11), 4033; https://doi.org/10.3390/ma15114033 - 06 Jun 2022
Viewed by 391
Abstract
Tilia cordata Mill. is a favourite tree used in urban spaces. For this reason, it is important to know its sensitivity to environmental stress, which is particularly burdensome for vegetation in urban spaces. The aim of the study was to investigate the properties [...] Read more.
Tilia cordata Mill. is a favourite tree used in urban spaces. For this reason, it is important to know its sensitivity to environmental stress, which is particularly burdensome for vegetation in urban spaces. The aim of the study was to investigate the properties necessary to control the growth of these trees and their subsequent use, i.e., chemical properties (percentage contents of cellulose, holocellulose, lignin, pentosans and substances soluble in NaOH and EtOH) as well as the chemical elements (K, Na, Mg, Ca and Fe, Zn, Cu, Pb, Cd, B, Ni, Cr, Al, As and Hg) and selected hygroscopic properties (hysteresis and sorption isotherms). Trees of Tilia cordata Mill. growing in environments exposed to environmental stress of varying severity were examined. Regardless of the growth conditions, in terms of its chemical composition, bark differs significantly from wood, showing twice the contents of soluble substances in NaOH and lignin and half the content of polysaccharides. Growth conditions clearly affect the range of selected chemical components in bark, e.g., substances soluble in ethanol, cellulose, or lignin. The main inorganic elements in bark and wood are Na, K, Ca, Mg and Zn. In bark, a relationship was found between the content of most chemical elements and differing environmental growth conditions. It was shown that environmental stress influenced the hygroscopic properties of wood and bark, which are a consequence of the percentage of chemical components. Full article
(This article belongs to the Special Issue Trends on the Wood Materials and Technologies)
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Article
Unraveling the Phase Stability and Physical Property of Modulated Martensite in Ni2Mn1.5In0.5 Alloys by First-Principles Calculations
Materials 2022, 15(11), 4032; https://doi.org/10.3390/ma15114032 - 06 Jun 2022
Viewed by 341
Abstract
Large magnetic field-induced strains can be achieved in modulated martensite for Ni-Mn-In alloys; however, the metastability of the modulated martensite imposes serious constraints on the ability of these alloys to serve as promising sensor and actuator materials. The phase stability, magnetic properties, and [...] Read more.
Large magnetic field-induced strains can be achieved in modulated martensite for Ni-Mn-In alloys; however, the metastability of the modulated martensite imposes serious constraints on the ability of these alloys to serve as promising sensor and actuator materials. The phase stability, magnetic properties, and electronic structure of the modulated martensite in the Ni2Mn1.5In0.5 alloy are systematically investigated. Results show that the 6M and 5M martensites are metastable and will eventually transform to the NM martensite with the lowest total energy in the Ni2Mn1.5In0.5 alloy. The physical properties of the incommensurate 7M modulated martensite (7M–IC) and nanotwinned 7M martensite (7M(52¯)2) are also calculated. The austenite (A) and 7M(52¯)2 phases are ferromagnetic (FM), whereas the 5M, 6M, and NM martensites are ferrimagnetic (FIM), and the FM coexists with the FIM state in the 7M–IC martensite. The calculated electronic structure demonstrates that the splitting of Jahn–Teller effect and the strong Ni–Mn bonding interaction lead to the enhancement of structural stability. Full article
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Article
Study on Photocatalytic Performance of Ag/TiO2 Modified Cement Mortar
Materials 2022, 15(11), 4031; https://doi.org/10.3390/ma15114031 - 06 Jun 2022
Viewed by 363
Abstract
In this paper, Ag-TiO2 photocatalysts with different Ag contents (1 mol%–5 mol%) were prepared and applied to cement mortar. The photocatalytic performance of Ag-TiO2 and photocatalytic cement mortar under UV light and simulated solar light was evaluated. The results showed that [...] Read more.
In this paper, Ag-TiO2 photocatalysts with different Ag contents (1 mol%–5 mol%) were prepared and applied to cement mortar. The photocatalytic performance of Ag-TiO2 and photocatalytic cement mortar under UV light and simulated solar light was evaluated. The results showed that Ag loading on the surface of TiO2 could reduce its band gap width and increase its absorbance in the visible region, and 2% Ag-TiO2 had the highest photocatalytic activity under UV light, the degradation rate of methyl orange (MO) was 95.5% at 30 min, and the first-order reaction constant k was 0.0980 min−1, which was 61.7% higher than that of TiO2, and 5% Ag-TiO2 had the highest photocatalytic activity under solar light, the degradation rate of methylene blue (MB) was 69.8% at 40 min, and the first-order reaction constant k was 0.0294 min−1, which was 90.9% higher than that of TiO2. The photocatalytic mortar prepared by the spraying method has high photocatalytic performance, The MO degradation rate of sample S2 under UV light was 87.5% after 120 min, MB degradation rate of sample S5 under solar light was 75.4% after 120 min. The photocatalytic reaction conforms to the zero-order reaction kinetics, which was 1.5 times–3.3 times higher than that of the mixed samples and has no effect on the mechanical properties of mortar. Full article
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Article
Modeling Dynamic Recrystallization Behavior in a Novel HIPed P/M Superalloy during High-Temperature Deformation
Materials 2022, 15(11), 4030; https://doi.org/10.3390/ma15114030 - 06 Jun 2022
Viewed by 308
Abstract
The dynamic recrystallization (DRX) features and the evolution of the microstructure of a new hot isostatic pressed (HIPed) powder metallurgy (P/M) superalloy are investigated by hot-compression tests. The sensitivity of grain dimension and DRX behavior to deformation parameters is analyzed. The results reveal [...] Read more.
The dynamic recrystallization (DRX) features and the evolution of the microstructure of a new hot isostatic pressed (HIPed) powder metallurgy (P/M) superalloy are investigated by hot-compression tests. The sensitivity of grain dimension and DRX behavior to deformation parameters is analyzed. The results reveal that the DRX features and grain-growth behavior are significantly affected by deformation conditions. The DRX process is promoted with a raised temperature/true strain or a reduced strain rate. However, the grains grow up rapidly at relatively high temperatures. At strain rates of o.1 s−1 and 1 s−1, a uniform microstructure and small grains are obtained. Due to the obvious differences in the DRX rate at various temperatures, the piecewise DRX kinetics equations are proposed to predict the DRX behavior. At the same time, a mathematical model for predicting the grain dimension and the grain growth behavior is established. To further analyze the DRX behavior and the changes in grain dimension, the hot deformation process is simulated. The developed grain-growth equation as well as the piecewise DRX kinetics equations are integrated into DEFORM software. The simulated DRX features are consistent with the test results, indicating that the proposed DRX kinetics equations and the established grain-growth model can be well used for describing the microstructure evolution. So, they are very useful for the practical hot forming of P/M superalloy parts. Full article
(This article belongs to the Special Issue Feature Papers in "Metals and Alloys" Section)
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Article
Compressive and Thermal Properties of Non-Structural Lightweight Concrete Containing Industrial Byproduct Aggregates
Materials 2022, 15(11), 4029; https://doi.org/10.3390/ma15114029 - 06 Jun 2022
Viewed by 462
Abstract
This study aimed to investigate the recycling opportunities for industrial byproducts and their contribution to innovative concrete manufacturing processes. The attention was mainly focused on municipal solid waste incineration fly ash (MSWI-FA) and its employment, after a washing pre-treatment, as the main component [...] Read more.
This study aimed to investigate the recycling opportunities for industrial byproducts and their contribution to innovative concrete manufacturing processes. The attention was mainly focused on municipal solid waste incineration fly ash (MSWI-FA) and its employment, after a washing pre-treatment, as the main component in artificially manufactured aggregates containing cement and ground granulated blast furnace slag (GGBFS) in different percentages. The produced aggregates were used to produce lightweight concrete (LWC) containing both artificial aggregates only and artificial aggregates mixed with a relatively small percentage of recycled polyethylene terephthalate (PET) in the sand form. Thereby, the possibility of producing concrete with good mechanical properties and enhanced thermal properties was investigated through effective PET reuse with beneficial impacts on the thermal insulation of structures. Based on the obtained results, the samples containing artificial aggregates had lower compressive strength (up to 30%) but better thermal performance (up to 25%) with respect to the reference sample made from natural aggregates. Moreover, substituting 10% of recycled aggregates with PET led to a greater reduction in resistance while improving the thermal conductivity. This type of concrete could improve the economic and environmental aspects by incorporating industrial wastes—mainly fly ash—thereby lowering the use of cement, which would lead to a reduction in CO2 emissions. Full article
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Article
A Simple and Efficient Method for Preparing High-Purity α-CaSO4·0.5H2O Whiskers with Phosphogypsum
Materials 2022, 15(11), 4028; https://doi.org/10.3390/ma15114028 - 06 Jun 2022
Viewed by 371
Abstract
A simple and efficient approach for the high-purity CaSO4·2H2O (DH) whiskers and α-CaSO4·0.5H2O (α-HH) whiskers derived from such phosphogypsum (PG) was proposed. The impact of different experimental parameters on supersaturated dissolution–recrystallization and preparation processes of [...] Read more.
A simple and efficient approach for the high-purity CaSO4·2H2O (DH) whiskers and α-CaSO4·0.5H2O (α-HH) whiskers derived from such phosphogypsum (PG) was proposed. The impact of different experimental parameters on supersaturated dissolution–recrystallization and preparation processes of α-CaSO4·0.5H2O was elaborated. At 3.5 mol/L HCl concentration, the dissolution temperature and time were 90 °C and 20 min, respectively. After eight cycles and 5–8 times cycles, total crystallization amount of CaSO4·2H2O was 21.75 and 9.97 g/100 mL, respectively, from supersaturated HCl solution. The number of cycles affected the shape and amount of the crystal. Higher HCl concentration facilitated CaSO4·2H2O dissolution and created a much higher supersaturation, which acted as a larger driving force for phase transformation of CaSO4·2H2O to α-CaSO4·0.5H2O. The HCl solution system’s optimum experimental conditions for HH whiskers preparation involved acid leaching of CaSO4·2H2O sample, with HCl concentration 6.0 mol/L, reaction temperature 80 °C, and reaction time 30 min–60 min. Under the third cycle conditions, α-CaSO4·0.5H2O whiskers were uniform in size, clear, and distinct in edges and angles. The length range of α-CaSO4·0.5H2O whiskers was from 106 μm to 231 μm and diameter range from 0.43 μm to 1.35 μm, while the longest diameter ratio was 231. Purity of α-CaSO4·0.5H2O whiskers was approximately 100%, where whiteness reached 98.6%. The reuse of the solution enables the process to discharge no waste liquid. It provides a new reference direction for green production technology of phosphogypsum. Full article
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Article
An Experimental Investigation on the Thermo-Rheological Behaviors of Lactic Acid-Based Natural Deep Eutectic Solvents
Materials 2022, 15(11), 4027; https://doi.org/10.3390/ma15114027 - 06 Jun 2022
Viewed by 370
Abstract
The rheological studies of Lactic Acid (LA)-based Natural Deep Eutectic Solvents (NADES) are provided in the present investigation. Those mechanisms were also studied in which three distinct Hydrogen Bond Acceptors (HBAs) of Choline Chloride (ChCl), Betaine (Be), and β-Alanine (β-Al), after being added [...] Read more.
The rheological studies of Lactic Acid (LA)-based Natural Deep Eutectic Solvents (NADES) are provided in the present investigation. Those mechanisms were also studied in which three distinct Hydrogen Bond Acceptors (HBAs) of Choline Chloride (ChCl), Betaine (Be), and β-Alanine (β-Al), after being added to a specific Hydrogen Bond Donor (HBD) at a predefined mole-to-mole ratio of 1:1, affected the rheological properties of the prepared NADES. The alterations in the rheology-related characteristics in association with the mechanical and physical properties indicate the tolerance of the material under various operational conditions in the field and show their potential utilization as environmentally suitable and feasible solvents for industrial applications. In the present research, the viscoelastic properties of the three samples of NADES were assessed along with their shear flow properties. The backward and forward temperature change in the Apparent Viscosity (AV) pattern related to the NADES system was described by a rheogram. Furthermore, the density was determined and compared with the AV while considering the temperature-related factor. On a further note, the viscoelastic characteristics were utilized in describing and investigating the network disturbance on the level of the microstructure of NADES upon frequency sweep. A series of experiments were carried out using Thermogravimetry Analysis (TGA) to investigate the thermo-physical properties to optimize them. The rheological properties of shear flow measurements were analyzed using the Bingham model that is best suited for the AV developed with the shear rate with the dynamic yield stress of three systems. The Bingham model was used to determine the lowest stress necessary to disturb the network structure and commence the flow of LA-based NADES. Overall, the viscoelastic behavior of the LA-based NADES revealed the dissimilarity between their strength and viscosity. In addition, shear flow investigations demonstrated that LA-based NADES systems exhibit non-Newtonian properties and substantial shear-thinning effects equivalent to those of alternative IL sorbents. Assessing the rheological properties of LA-based NADES is crucial for a better understanding the key challenges associated with high viscosity. Defining the transport yield stress requirements for NADES systems under different conditions benefits their future development and potentially opens the door to more challenging applications. Full article
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Article
Thermodynamic Formation Properties of Point Defects in Germanium Crystal
Materials 2022, 15(11), 4026; https://doi.org/10.3390/ma15114026 - 06 Jun 2022
Viewed by 288
Abstract
Point defects are crucial in determining the quality of germanium crystals. A quantitative understanding of the thermodynamic formation properties of the point defects is necessary for the subsequent control of the defect formation during crystal growth. Here, molecular dynamics simulations were employed to [...] Read more.
Point defects are crucial in determining the quality of germanium crystals. A quantitative understanding of the thermodynamic formation properties of the point defects is necessary for the subsequent control of the defect formation during crystal growth. Here, molecular dynamics simulations were employed to investigate the formation energies, total formation free energies and formation entropies of the point defects in a germanium crystal. As far as we know, this is the first time that the total formation free energies of point defects in a germanium crystal have been reported in the literature. We found that the formation energies increased slightly with temperature. The formation free energies decreased significantly with an increase in temperature due to the increase in entropy. The estimated total formation free energies at the melting temperature are ~1.3 eV for self-interstitial and ~0.75 eV for vacancy, corresponding to a formation entropy of ~15 kB for both types of point defects. Full article
(This article belongs to the Special Issue Thermodynamic Modeling of Materials: Microstructure and Properties)
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Article
Multi Expression Programming Model for Strength Prediction of Fly-Ash-Treated Alkali-Contaminated Soils
Materials 2022, 15(11), 4025; https://doi.org/10.3390/ma15114025 - 06 Jun 2022
Viewed by 390
Abstract
Rapid industrialization is leading to the pollution of underground natural soil by alkali concentration which may cause problems for the existing expansive soil in the form of producing expanding lattices. This research investigates the effect of stabilizing alkali-contaminated soil by using fly ash. [...] Read more.
Rapid industrialization is leading to the pollution of underground natural soil by alkali concentration which may cause problems for the existing expansive soil in the form of producing expanding lattices. This research investigates the effect of stabilizing alkali-contaminated soil by using fly ash. The influence of alkali concentration (2 N and 4 N) and curing period (up to 28 days) on the unconfined compressive strength (UCS) of fly ash (FA)-treated (10%, 15%, and 20%) alkali-contaminated kaolin and black cotton (BC) soils was investigated. The effect of incorporating different dosages of FA (10%, 15%, and 20%) on the UCSkaolin and UCSBC soils was also studied. Sufficient laboratory test data comprising 384 data points were collected, and multi expression programming (MEP) was used to create tree-based models for yielding simple prediction equations to compute the UCSkaolin and UCSBC soils. The experimental results reflected that alkali contamination resulted in reduced UCS (36% and 46%, respectively) for the kaolin and BC soil, whereas the addition of FA resulted in a linear rise in the UCS. The optimal dosage was found to be 20%, and the increase in UCS may be attributed to the alkali-induced pozzolanic reaction and subsequent gain of the UCS due to the formation of calcium-based hydration compounds (with FA addition). Furthermore, the developed models showed reliable performance in the training and validation stages in terms of regression slopes, R, MAE, RMSE, and RSE indices. Models were also validated using parametric and sensitivity analysis which yielded comparable variation while the contribution of each input was consistent with the available literature. Full article
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Article
Numerical Simulation Study of Gas-Solid Heat Transfer and Decomposition Processes of Limestone Calcined with Blast Furnace Gas in a Parallel Flow Regenerative Lime Kiln
Materials 2022, 15(11), 4024; https://doi.org/10.3390/ma15114024 - 06 Jun 2022
Viewed by 346
Abstract
Quicklime is an essential reducing agent in the steel smelting process and its calcination from limestone is accompanied by considerable energy consumption. As a relatively economical lime kiln, the Parallel Flow Regenerative (PFR) lime kiln is used as the main equipment for the [...] Read more.
Quicklime is an essential reducing agent in the steel smelting process and its calcination from limestone is accompanied by considerable energy consumption. As a relatively economical lime kiln, the Parallel Flow Regenerative (PFR) lime kiln is used as the main equipment for the production of quicklime by various steel industries. PFR lime kilns generally use natural gas as the fuel gas. Although natural gas has a high calorific value and is effective in calcination, with the increasing price of natural gas and the pressure saves energy and protect the environment, it makes sense of exploring the use of cleaner energy sources or other sub-products as fuel gas. The use of blast furnace gas (BFG) as a low calorific value fuel gas produced in the steel smelting process has been of interest. This paper therefore develops a set of mathematical models for gas-solid heat transfer and limestone decomposition based on a Porous Medium Model (PMM) and a Shrinking Core Model (SCM) to numerically simulate a PFR lime kiln using BFG in order to investigate the feasibility of calcining limestone with low calorific fuel gas and to provide a valuable reference for future development of such processes and the kiln structure improvement. Full article
(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization)
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Article
Mechanical Properties Analysis of Explosive Welded Sheet of AA2519-Ti6Al4V with Interlayer of AA1050 Subjected to Heat-Treatment
Materials 2022, 15(11), 4023; https://doi.org/10.3390/ma15114023 - 06 Jun 2022
Viewed by 370
Abstract
The paper presents results of investigations of welding sheets of AA2519-Ti6Al4V, a difficult-to-joint components materials, produced by explosive welding with a thin technological interlayer of AA1050. The joining process leads to the formation of intermetalics in the vicinity of joint and generates significant [...] Read more.
The paper presents results of investigations of welding sheets of AA2519-Ti6Al4V, a difficult-to-joint components materials, produced by explosive welding with a thin technological interlayer of AA1050. The joining process leads to the formation of intermetalics in the vicinity of joint and generates significant residual stresses. In the next step the laminate was subjected to a heat treatment process in order to improve the mechanical properties by precipitation hardening. This treatment should not be carried out before welding because of negative influence on a ductility of the aluminum alloy. Material in this state was subjected to the tests of chemical composition, microstructure, and microhardness. A tensile test was carried out with accompanying strain analysis by the digital image correlation (DIC) method. Moreover, the residual stresses were determined which were measured by using two methods, the X-ray diffraction and the hole drilling. This approach made it possible to measure the residual stresses both in the plane parallel to the surface and in the cross section of the laminate. Full article
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Article
Effect of Laser Heating on the Life of Cutting Tools Coated with Single- and Multilayer Coatings Containing a TiN Layer
Materials 2022, 15(11), 4022; https://doi.org/10.3390/ma15114022 - 06 Jun 2022
Viewed by 369
Abstract
This study proposes a novel use of laser heating to increase the adhesion between coatings fabricated by low-temperature PVD and replaceable cemented carbide cutting inserts, thus extending the life of these cutting tools in the machining of difficult-to-machine materials. Our previous studies conducted [...] Read more.
This study proposes a novel use of laser heating to increase the adhesion between coatings fabricated by low-temperature PVD and replaceable cemented carbide cutting inserts, thus extending the life of these cutting tools in the machining of difficult-to-machine materials. Our previous studies conducted on CVD coatings showed that these coatings had higher adhesion due to a much higher process temperature. However, taking into account the fact that PVD coatings have better technological properties (e.g., lower structure porosity, higher hardness, and better tribological properties) than CVD coatings, it is fully justified to investigate ways of improving the PVD coating adhesion to the substrate. In this study, replaceable cutting inserts with different hard coatings of titanium nitride were used. Laser heating was conducted with different power densities. The adhesion strength of the tested coatings was determined via vibration spectrum analysis. In addition, 2D surface imaging, scanning electron microscopy, and X-ray fluorescence spectrometry were employed to examine the coatings after laser heating. A significant increase in the adhesion of single-layer (TiN) and double-layer (TiCN + TiN) coatings to the cemented carbide substrate, together with increased tool life, was observed after heating the samples with 40% of the maximum laser power. The application of a multilayer coating containing thermal shock-sensitive (TiAlSi) N did not increase the tool life. This paper attempts to interpret the obtained results. Full article
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Article
An Accuracy Comparison of Micromechanics Models of Particulate Composites against Microstructure-Free Finite Element Modeling
Materials 2022, 15(11), 4021; https://doi.org/10.3390/ma15114021 - 06 Jun 2022
Viewed by 299
Abstract
Micromechanics models of composite materials are preferred in the analysis and design of composites for their high computational efficiency. However, the accuracy of the micromechanics models varies widely, depending on the volume fraction of inclusions and the contrast of phase properties, which have [...] Read more.
Micromechanics models of composite materials are preferred in the analysis and design of composites for their high computational efficiency. However, the accuracy of the micromechanics models varies widely, depending on the volume fraction of inclusions and the contrast of phase properties, which have not been thoroughly studied, primarily due to the lack of complete and representative experimental data. The recently developed microstructure-free finite element modeling (MF-FEM) is based on the fact that, for a particulate-reinforced composite, if the characteristic size of the inclusions is much smaller than the composite representative volume element (RVE), the elastic properties of the RVE are independent of inclusion shape and size. MF-FEM has a number of advantages over the conventional microstructure-based finite element modeling. MF-FEM predictions have good to excellent agreement with the reported experiment results. In this study, predictions produced by MF-FEM are used in replace of experimental data to compare the accuracy of selected micromechanics models of particulate composites. The results indicate that, only if both the contrasts in phase Young’s moduli and phase Poisson’s ratios are small, the micromechanics models are able to produce accurate predictions. In other cases, they are more or less inaccurate. This study may serve as a guide for the appropriate use of the micromechanics models. Full article
(This article belongs to the Special Issue Experimental and Numerical Investigation of Composite Materials)
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Article
Influence of Build Angle and Polishing Roughness on Corrosion Resistance of 316L Stainless Steel Fabricated by SLM Method
Materials 2022, 15(11), 4020; https://doi.org/10.3390/ma15114020 - 06 Jun 2022
Viewed by 305
Abstract
Metal parts formed by laser additive manufacturing methods usually have large surface roughness, which affects the corrosion resistance of the parts. This study reported the reason for and mechanism of the large surface roughness of 316L stainless steel samples manufactured by selective laser [...] Read more.
Metal parts formed by laser additive manufacturing methods usually have large surface roughness, which affects the corrosion resistance of the parts. This study reported the reason for and mechanism of the large surface roughness of 316L stainless steel samples manufactured by selective laser melting (SLM) at different build angles. Through the study, the reason for the large top surface roughness (average surface roughness is 15.3 μm) is due to the molten channel structure formed on the surface. The large side surface roughness (average surface roughness is 19.1 μm) is due to the incomplete fused particles adhering to the surface. Through electrochemical experiments, the influence of the build angle and polishing treatment on the corrosion resistance of the sample was studied. The different roughness of the top and side surfaces results in different corrosion resistances (the top surface pitting potential is 0.317 VAg/AgCl and the side surface pitting potential is 0.148 VAg/AgCl), and polishing can improve the surface corrosion resistance of specimens by reducing the surface roughness, especially for the side surface (from 0.148 to 0.351 VAg/AgCl). Therefore, parts manufactured by SLM can be post-treated to reduce roughness and improve surface corrosion resistance. Full article
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Article
Study on Simulation and Experiment of Cu, C-Doped Ag/Ni Contact Materials
Materials 2022, 15(11), 4019; https://doi.org/10.3390/ma15114019 - 06 Jun 2022
Viewed by 271
Abstract
Ag/Ni contact material with greenery and good performance is a cadmium-free silver-based contact material that has been vigorously developed in recent years. However, Ag/Ni contact material has poor welding resistance. Based on the first principles of density functional theory, the interface model of [...] Read more.
Ag/Ni contact material with greenery and good performance is a cadmium-free silver-based contact material that has been vigorously developed in recent years. However, Ag/Ni contact material has poor welding resistance. Based on the first principles of density functional theory, the interface model of Cu, C-doped Ag/Ni was established. The work of separation and interfacial energy of interface models showed that doping can improve the interfacial bonding strength and interfacial stability, with C-doped Ag/Ni having the strongest stability and interfacial bonding strength. It can be seen from the population and density of state that covalent bonds exist between Ag and Ni atoms of the Ag/Ni phase interface at the electronic structure level. Finally, the doped Ag/Ni contact material was prepared by the powder metallurgy method. Through the arc energy and welding force in the electrical contact experiment, it was obtained that the welding resistance of C-doped Ag/Ni was better than Cu-doped Ag/Ni contact material, which verified the correctness of the simulation results. Overall, the present study provides a theoretical method for the screening of doping elements to improve the performance of Ag/Ni contact material. Full article
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Article
Effect of Microstructure on the Mechanical Properties of Steel Fiber-Reinforced Recycled Concretes
Materials 2022, 15(11), 4018; https://doi.org/10.3390/ma15114018 - 06 Jun 2022
Viewed by 331
Abstract
A steel fiber-reinforced recycled concrete (SFRRC) is a porous material, and its macromechanical properties are affected by its microstructure. To elucidate the change rules and internal mechanisms of the mechanical properties of SFRRCs, the mechanical properties and failure modes of SFRRCs were studied [...] Read more.
A steel fiber-reinforced recycled concrete (SFRRC) is a porous material, and its macromechanical properties are affected by its microstructure. To elucidate the change rules and internal mechanisms of the mechanical properties of SFRRCs, the mechanical properties and failure modes of SFRRCs were studied at different water–cement ratio, replacement rate of recycled concrete aggregate (RCA), and steel fiber content. Moreover, the microstructures of the interface transition zones (ITZ) of the SFRRC specimens were tested by scanning electron microscopy and mercury intrusion, and the effect of the microscopic pore structure on the macromechanical properties of SFRRC was analyzed. The research results showed that an appropriate amount of steel fibers could reduce the size and number of cracks in the ITZ and improve the pore structure of an SFRRC. Based on the fractal dimension, porosity and other factors, the quantitative relationship between the macromechanical properties and microscopic pore structure parameters of SFRRCs was established. Full article
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Article
Influence of Fiber Type and Length on Mechanical Properties of MICP-Treated Sand
Materials 2022, 15(11), 4017; https://doi.org/10.3390/ma15114017 - 06 Jun 2022
Viewed by 350
Abstract
Fibers are applied in construction work to improve the strength and avoid brittle failure of soil. In this paper, we analyze the impact mechanism of fiber type and length on the immobilization of microorganisms from macroscopic and microscopic perspectives with fibers of 0.2% [...] Read more.
Fibers are applied in construction work to improve the strength and avoid brittle failure of soil. In this paper, we analyze the impact mechanism of fiber type and length on the immobilization of microorganisms from macroscopic and microscopic perspectives with fibers of 0.2% volume fraction added to microbial-induced calcite precipitation (MICP)-treated sand. Results show the following: (1) The unconfined compressive strength (UCS) of MICP-treated sand first increases and then decreases with increasing fiber length because short fiber reinforcement can promote the precipitation of calcium carbonate, and the network formed between the fibers limits the movement of sand particles and enhances the strength of the microbial solidified sand. However, the agglomeration caused by overlong fibers leads to uneven distribution of calcium carbonate and a reduction in strength. The optimal fiber length of polypropylene, glass, and polyvinyl alcohol fiber is 9 mm, and that of basalt fiber is 12 mm. (2) The UCS of the different fiber types, from small to large, is basalt fiber < polypropylene fiber < glass fiber < polyvinyl alcohol fiber because the quality of the fiber monofilament differs. More fibers result in more a evident effect of interlacing and bending on sand and higher strength in consolidated sand. Full article
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Article
Strain-Enhanced Thermoelectric Performance in GeS2 Monolayer
Materials 2022, 15(11), 4016; https://doi.org/10.3390/ma15114016 - 06 Jun 2022
Viewed by 389
Abstract
Strain engineering has attracted extensive attention as a valid method to tune the physical and chemical properties of two-dimensional (2D) materials. Here, based on first-principles calculations and by solving the semi-classical Boltzmann transport equation, we reveal that the tensile strain can efficiently enhance [...] Read more.
Strain engineering has attracted extensive attention as a valid method to tune the physical and chemical properties of two-dimensional (2D) materials. Here, based on first-principles calculations and by solving the semi-classical Boltzmann transport equation, we reveal that the tensile strain can efficiently enhance the thermoelectric properties of the GeS2 monolayer. It is highlighted that the GeS2 monolayer has a suitable band gap of 1.50 eV to overcome the bipolar conduction effects in materials and can even maintain high stability under a 6% tensile strain. Interestingly, the band degeneracy in the GeS2 monolayer can be effectually regulated through strain, thus improving the power factor. Moreover, the lattice thermal conductivity can be reduced from 3.89 to 0.48 W/mK at room temperature under 6% strain. More importantly, the optimal ZT value for the GeS2 monolayer under 6% strain can reach 0.74 at room temperature and 0.92 at 700 K, which is twice its strain-free form. Our findings provide an exciting insight into regulating the thermoelectric performance of the GeS2 monolayer by strain engineering. Full article
(This article belongs to the Special Issue Materials Physics in Thermoelectric Materials)
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Article
Synthesis of a Superhydrophobic Fluorinated Nano-Emulsion and Its Modification on the Wettability of Tight Sandstone
Materials 2022, 15(11), 4015; https://doi.org/10.3390/ma15114015 - 06 Jun 2022
Viewed by 300
Abstract
The water-blocking effect is a serious problem when developing tight sandstone gas reservoirs, which can cause a sharp reduction in gas production. Wettability alteration of near-wellbore sand rock surface from superhydrophilicity to superhydrophobicity is an effective method to decrease capillary pressure. In this [...] Read more.
The water-blocking effect is a serious problem when developing tight sandstone gas reservoirs, which can cause a sharp reduction in gas production. Wettability alteration of near-wellbore sand rock surface from superhydrophilicity to superhydrophobicity is an effective method to decrease capillary pressure. In this study, a superhydrophobic fluorinated nano-emulsion was synthesized via a soap-free emulsion polymerization process using methacryloxyethyl trimethyl ammonium chloride, trifluoctyl methacrylate, and styrene as monomers. The effect of the fluorinated monomer concentration on wettability alteration was evaluated by measuring the contact angle of the formation water droplet on the modified glass slides using nano-emulsions with different fluorinated monomer concentrations. The results showed that the nano-emulsion had a good dispersibility and homogeneous particle size of around 90 nm, and with the increase in fluorinated monomer concentration, the contact angle increased. The contact angle was the largest when the fluorinated monomer mass rate concentration reached 50%. The adsorption of nanoparticles could alter the rock wettability from a super hydrophilic state (θ = 7°) to a superhydrophobic state (θ = 150°). The spontaneous imbibition experiments showed that the formation water adsorption quality of the core decreased by 49.7% after being modified by the nano-emulsion. The nano-emulsion showed a good superhydrophobicity and had the potential to be used to reduce the water-blocking damage in the tight gas reservoirs. Full article
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Article
Physical, Hydric, Thermal and Mechanical Properties of Earth Renders Amended with Dolomitic Lime
Materials 2022, 15(11), 4014; https://doi.org/10.3390/ma15114014 - 06 Jun 2022
Viewed by 358
Abstract
The global objective of this work was to manufacture resistant and durable (water resistant) earth renders with good thermal insulation. For this purpose, a medium plastic clayey soil from Kôdéni (Burkina Faso), constituted by kaolinite (62 wt.%), quartz (31 wt.%), and goethite (2 [...] Read more.
The global objective of this work was to manufacture resistant and durable (water resistant) earth renders with good thermal insulation. For this purpose, a medium plastic clayey soil from Kôdéni (Burkina Faso), constituted by kaolinite (62 wt.%), quartz (31 wt.%), and goethite (2 wt.%), was mixed with dolomitic lime (up to 6 wt.%) to manufacture earth renders. The mineralogical, microstructural, and chemical characteristics of dolomitic lime, as well as the physical (linear shrinkage, apparent density, and accessible porosity), hydric (water absorption test by capillarity and spray test), thermal (thermal conductivity), and mechanical (abrasion resistance, flexural, and compressive strengths) properties of the earth renders were evaluated. From these studies, it appears that the addition of dolomitic lime induces the formation of calcium silicate (CSH) and magnesium silicate (MSH) hydrates. These CSH and MSH are mainly formed from the pozzolanic reaction between finely ground quartz and the weak silica of kaolinite in basic media. These formed hydrates improve the physical, hydric, thermal, and mechanical properties of earth renders. This improvement is due to the fact that the formed CSH and MSH stick to the isolated particles of the soil, making them more compact. In view of the good mechanical strength and water resistance, as well as the low thermal conductivity, the elaborated earth renders are suitable for habitats with dry climates, such as the Sahel. Full article
(This article belongs to the Special Issue Earth-Based Building Materials)
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Article
In-Plane Seismic Strengthening of Brick Masonry Using Steel and Plastic Meshes
Materials 2022, 15(11), 4013; https://doi.org/10.3390/ma15114013 - 06 Jun 2022
Viewed by 344
Abstract
Unreinforced masonry structures are vulnerable to seismic loading due to their brittle behavior, and must therefore be strengthened. This paper presents the seismic performance of brick masonry strengthened with steel and plastic meshes. For this purpose, twenty masonry wallets of (600 × 600 [...] Read more.
Unreinforced masonry structures are vulnerable to seismic loading due to their brittle behavior, and must therefore be strengthened. This paper presents the seismic performance of brick masonry strengthened with steel and plastic meshes. For this purpose, twenty masonry wallets of (600 × 600 × 113 mm) were constructed, keeping the same materials and workmanship. Fifteen of them were reinforced using steel and plastic meshes. These specimens were tested for in-plane static cyclic diagonal tension (shear) behavior. The critical parameters, such as shear stress, strain, failure modes, ductility, energy dissipation, and stiffness degradation were investigated. Compared to reference and plastic-reinforced specimens, the steel-reinforced samples were found to be highly effective. Furthermore, the recommended category of steel increased the shear capacity, energy dissipation, and ductility ratio by 1.3, 14, and 6.3 times, respectively. Full article
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Article
Bio-Alcohol Sensor Based on One-Dimensional Photonic Crystals for Detection of Organic Materials in Wastewater
Materials 2022, 15(11), 4012; https://doi.org/10.3390/ma15114012 - 05 Jun 2022
Viewed by 383
Abstract
In this work, we have explored a novel application of one–dimensional (1D) photonic crystals (PCs) as a biomarker for the detection of organic materials in wastewater. The high concentration of organic materials may lead to adverse impact on human life. In order to [...] Read more.
In this work, we have explored a novel application of one–dimensional (1D) photonic crystals (PCs) as a biomarker for the detection of organic materials in wastewater. The high concentration of organic materials may lead to adverse impact on human life. In order to save human life from these adverse effects, we have investigated the bio-alcohol sensing properties of a 1D multilayer periodic structure (AB)N/C/(AB)N capable of detecting organic materials in wastewater. The proposed structure works on the principle to detect a very small change in the refractive index of the wastewater sample under investigation by means of producing a shift in the position of the defect mode inside the photonic band gap (PBG) of the proposed structure. The transfer matrix method (TMM) has been used to investigate the transmission properties of the proposed design with the help of MATLAB software. We have also studied the effect of changes in the defect layer’s thickness, the volume fraction of the nanocomposite material and the incident angle on the sensitivity of our proposed bio-alcohol sensing design. Our bio-alcohol sensor shows a high sensitivity value of 500 nm/RIU and a low detection limit value of 1 × 10−5 RIU. The figure of merit and quality factor values of our bio-alcohol sensor are 5 × 103 and 5.236 × 103, respectively. The damping rate of the design is ξ=95.4927×105. Full article
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Article
Load-to-Failure Resistance and Optical Characteristics of Nano-Lithium Disilicate Ceramic after Different Aging Processes
Materials 2022, 15(11), 4011; https://doi.org/10.3390/ma15114011 - 05 Jun 2022
Viewed by 380
Abstract
The aim of this study was to compare the load-to-failure resistance and optical properties of nano-lithium disilicate (NLD) with lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) in different aging processes. Thirty crowns were milled from NLD, LDS, and ZLS (n = 10). [...] Read more.
The aim of this study was to compare the load-to-failure resistance and optical properties of nano-lithium disilicate (NLD) with lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) in different aging processes. Thirty crowns were milled from NLD, LDS, and ZLS (n = 10). All crowns were subjected to thermomechanical aging and loaded until catastrophic failure. Ten specimens from each material were prepared in two different thicknesses (0.7 mm and 1.5 mm, n = 5), and color coordinates were measured before and after coffee thermocycling. Color differences (ΔE00) and relative translucency parameter (RTP) were calculated. Data were analyzed by using ANOVA and Bonferroni-corrected t-tests (α = 0.05). ZLS had the highest load-to-failure resistance (p ≤ 0.002), while the difference between LDS and NLD was nonsignificant (p = 0.776). The interaction between material type and thickness affected ΔE00 (p < 0.001). Among the 0.7 mm thick specimens, ZLS had the lowest ΔE00 (p < 0.001). Furthermore, 1.5 mm thick ZLS had lower ΔE00 than that of 1.5 mm thick LDS (p = 0.036). Other than ZLS (p = 0.078), 0.7 mm thick specimens had higher ΔE00 (p < 0.001). The interaction between material type, thickness, and thermocycling affected RTP (p < 0.001). Thinner specimens presented higher RTP (p < 0.001). NLD and LDS had higher RTP than ZLS (p ≤ 0.036). However, 0.7 mm thick specimens had similar RTP after coffee thermocycling (p ≥ 0.265). Coffee thermocycling reduced the RTP values of 0.7 mm thick NLD (p = 0.032) and LDS (p = 0.008). NLD may endure the occlusal forces present in the posterior region. However, long-term coffee consumption may impair the esthetics of restorations particularly when thin NLD is used. Full article
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Article
Investigation of Friction and Wear Behavior of Cast Aluminum Alloy Piston Skirt with Graphite Coating Using a Designed Piston Skirt Test Apparatus
Materials 2022, 15(11), 4010; https://doi.org/10.3390/ma15114010 - 05 Jun 2022
Viewed by 360
Abstract
A piston skirt friction and wear apparatus that simulates the contact and the relative motion of piston and cylinder liner in a real engine has been designed and constructed. With this apparatus, the friction and wear behavior of a cast aluminum alloy piston [...] Read more.
A piston skirt friction and wear apparatus that simulates the contact and the relative motion of piston and cylinder liner in a real engine has been designed and constructed. With this apparatus, the friction and wear behavior of a cast aluminum alloy piston with a graphite coating under different loads was studied, and the effectiveness of the apparatus was confirmed. The total wear of the piston skirt was higher under a higher load, and the upper part of the skirt surface (around the height of the piston pin) was worn more severely. The wear mechanisms were studied and, based on the test results and surface analyses, three main wear modes were believed to occur in the wear process of the piston skirt: abrasive, adhesive, and fatigue wear. The effects of skirt profile design, coating, and surface texturing on the friction and wear behavior of the piston skirt can be investigated well using the proposed apparatus, which can truly reflect actual working conditions and is useful to improve the tribological performances of piston skirts. Full article
(This article belongs to the Section Metals and Alloys)
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