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Materials, Volume 15, Issue 8 (April-2 2022) – 254 articles

Cover Story (view full-size image): One current topic of significant interest in the field of condensed matter physics lies in searching for materials hosting a flat-band electronic structure in momentum space, which is crucial for realizing novel correlated phenomena. In the case of topological materials, such a flat band, the so-called drumhead surface state can be produced on the surface of a Dirac nodal line semi-metal. In this work, we report our observation of a Dirac nodal loop and a possible drumhead state in a topological semi-metal. The observed state was highly localized in energy and extended over a large region in momentum, indicating that this class of materials offers an ideal platform with which to explore various novel phases, opening up new research frontiers in correlated topological physics. View this paper.
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Article
Experimental Study on the Effect of Carbonation Reaction on the Properties of Imitation Site Soil
Materials 2022, 15(8), 2958; https://doi.org/10.3390/ma15082958 - 18 Apr 2022
Viewed by 638
Abstract
In this study, sodium methylsilicate and lime were selected to prepare the same proportion of Imitation Site Soil, and according to the principle of carbonation reaction of restoration materials, the effect of carbonation reaction on the performance of restoration soil of earthen sites [...] Read more.
In this study, sodium methylsilicate and lime were selected to prepare the same proportion of Imitation Site Soil, and according to the principle of carbonation reaction of restoration materials, the effect of carbonation reaction on the performance of restoration soil of earthen sites was studied. The study has good significance for the conservation and restoration of earthen sites. The samples were cured with CO2 concentration and curing age as variables. After curing, the samples were tested to determine their water-resistant properties, uniaxial compressive strength, and pH value and a micro scanning electron microscope was used. The results indicated that the carbonation reaction can quickly improve the water resistance and compressive strength of imitation site soil, and reduced the water absorption by 16.67% compared to the specimens conditioned at 0.03% CO2 concentration. The UCS of specimens at 5%, 10%, and 15% CO2 concentrations increased by 72.22%, 131.19%, and 219.27%, respectively, compared with those at 0.03% CO2 concentration after the specimens were environmentally maintained in the carbonation chamber at 0.03%, 5%, 10%, and 15% CO2 concentrations for 120 h, respectively. The internal particle gradation of the imitation site soil improved after carbonation. These results provide a basis for improving the restoration technology of earthen sites. Full article
(This article belongs to the Section Construction and Building Materials)
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Article
Mechanical Properties and Microstructural Characterization of Metakaolin Geopolymers Based on Orthogonal Tests
Materials 2022, 15(8), 2957; https://doi.org/10.3390/ma15082957 - 18 Apr 2022
Cited by 3 | Viewed by 635
Abstract
Metakaolin was used as a raw material for the preparation of geopolymers, where two types of alkali activators (Na2SiO3 + NaOH and Na2SiO3 + NaOH) were used to prepare metakaolin geopolymers at room temperature. The mechanical properties [...] Read more.
Metakaolin was used as a raw material for the preparation of geopolymers, where two types of alkali activators (Na2SiO3 + NaOH and Na2SiO3 + NaOH) were used to prepare metakaolin geopolymers at room temperature. The mechanical properties and microstructures of the metakaolin geopolymers were analyzed. A three-factor, four-level orthogonal test was designed to investigate the mechanical properties of the metakaolin geopolymer with different ratios. The compressive and flexural strength of different specimens were tested for 7 and 28 days. Both the Na-based and K-based geopolymers exhibited excellent mechanical properties, but the K-based geopolymer had better mechanical properties. The optimal compressive strength and flexural strength of the K-based geopolymer were 73.93 MPa and 9.37 MPa, respectively. The 28-day optimal compressive strength of the Na-based polymer was 65.79 MPa, and the flexural strength was 8.71 MPa. SEM, XRD, and FTIR analyses showed that the mechanical properties of the geopolymers could be greatly improved by using a higher alkaline solution concentration, proper Na2SiO3/MOH mass ratio, and proper mass ratio of alkali exciter to metakaolin. Amorphous silicoaluminate was more favorable for the dissolution of silicon–alumina raw materials, promoted the formation of an amorphous silicoaluminate gel, and caused the internal structure of the geopolymer to be more compact. Full article
(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications)
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Article
Influence of Additives on Microstructure and Mechanical Properties of Alumina Ceramics
Materials 2022, 15(8), 2956; https://doi.org/10.3390/ma15082956 - 18 Apr 2022
Cited by 1 | Viewed by 647
Abstract
Alumina is one of the most commonly used and researched structural ceramic because of its excellent properties. However, its intrinsic brittleness is the fatal drawback, which hinders it from wider applications. How to improve its fracture toughness as well as the bending strength [...] Read more.
Alumina is one of the most commonly used and researched structural ceramic because of its excellent properties. However, its intrinsic brittleness is the fatal drawback, which hinders it from wider applications. How to improve its fracture toughness as well as the bending strength is always challenging for material researchers. In this paper, alumina matrix composites were fabricated by hot-pressing, in which some additives, including zirconia, alumina platelets, and MXene, were incorporated. The influence of the introduced additives on their microstructure and mechanical properties was investigated. Compare with the monolithic alumina, both bending strength and fracture toughness of all samples were improved greatly. Incorporation of zirconia was beneficial to the mechanical properties due to the phase-transformation strengthening and toughening mechanism. While alumina platelets resulted in high fracture toughness because of the self-toughening of elongated grains. The synergistic effect of alumina platelets and MXene enormously improved the fracture toughness from 2.9 ± 0.3 MPa·m1/2 for monolithic alumina to 7.5 ± 0.4 MPa·m1/2 for the composite, which was increased by 159%. This work will provide useful references for the fabrication of high-strength and high-toughness alumina ceramics by introducing additives properly. Full article
(This article belongs to the Special Issue High-Performance Structural Ceramics and Hybrid Materials)
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Article
Wettability and Surface Roughness Analysis of Laser Surface Texturing of AISI 430 Stainless Steel
Materials 2022, 15(8), 2955; https://doi.org/10.3390/ma15082955 - 18 Apr 2022
Cited by 3 | Viewed by 642
Abstract
Due to its wide applicability in industry, devising microstructures on the surface of materials can be easily implemented and automated in technological processes. Laser Surface Texturing (LST) is applied to modify the chemical composition, morphology, and roughness of surfaces (wettability), cleaning (remove contaminants), [...] Read more.
Due to its wide applicability in industry, devising microstructures on the surface of materials can be easily implemented and automated in technological processes. Laser Surface Texturing (LST) is applied to modify the chemical composition, morphology, and roughness of surfaces (wettability), cleaning (remove contaminants), reducing internal stresses of metals (hardening, tempering), surface energy (polymers, metals), increasing the adhesion (hybrid joining, bioengineering) and decreasing the growth of pathogenic bacteria (bioengineering). This paper is a continuation and extension of our previous studies in laser-assisted texturing of surfaces. Three different patterns (crater array-type C, two ellipses at 90° overlapping with its mirror-type B and 3 concentric octagons-type A) were applied with a nanosecond pulsed laser (active medium Nd: Fiber Diode-pumped) on the surface of a ferritic stainless steel (AISI 430). Micro texturing the surface of a material can modify its wettability behavior. A hydrophobic surface (contact angle greater than 90°) was obtained with different variations depending on the parameters. The analysis performed in this research (surface roughness, wettability) is critical for assessing the surface functionality, characteristics and properties of the stainless steel surface after the LST process. The values of the surface roughness and the contact angle are directly proportional to the number of repetitions and inversely proportional to the speed. Recommendations for the use of different texturing pattern designs are also made. Full article
(This article belongs to the Special Issue Multifunctional Coatings: From Protective to Bio-Applications)
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Article
Biomedical Membrane of Fish Collagen/Gellan Gum Containing Bone Graft Materials
Materials 2022, 15(8), 2954; https://doi.org/10.3390/ma15082954 - 18 Apr 2022
Cited by 1 | Viewed by 660
Abstract
The development of a guided bone regeneration (GBR) membrane with non-mammalian fish collagen has the advantage of low risk for transmission of infectious diseases in tissue regeneration. In this work, a fish collagen/gellan gum and bone graft material (FC/GG-BGM) composite GBR membrane were [...] Read more.
The development of a guided bone regeneration (GBR) membrane with non-mammalian fish collagen has the advantage of low risk for transmission of infectious diseases in tissue regeneration. In this work, a fish collagen/gellan gum and bone graft material (FC/GG-BGM) composite GBR membrane were fabricated through solution blending and casting procedures in a vacuum. The membranes were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy observation (SEM), and atomic force microscope (AFM) analyses. FT-IR results suggested that ionic interactions were formed between FC and GG both in composite powder and membranes. In vivo experiments showed that these FC/GG-BGM composite membranes could generate osteoblast minerals and promote loose bone calcification, thus accelerating bone regeneration. At 2 weeks, the defected site of rats treated with FC/GG-BGM membrane (0.377 ± 0.012 mm3) showed higher regeneration than that of rats treated with the bovine collagen membrane (0.290 ± 0.015 mm3) and control rats without membrane (0.160 ± 0.008 mm3). Compared with bovine collagen membrane, the FC/GG-BGM composite membrane displays better bone regeneration ability. Therefore, FC/GG-BGM composite membrane is suitable as a GBR membrane for bone regeneration. Full article
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Article
Development of Eco-Friendly Concrete Mix Using Recycled Aggregates: Structural Performance and Pore Feature Study Using Image Analysis
Materials 2022, 15(8), 2953; https://doi.org/10.3390/ma15082953 - 18 Apr 2022
Cited by 5 | Viewed by 753
Abstract
The shortage of natural aggregates has compelled the developers to devote their efforts to finding alternative aggregates. On the other hand, demolition waste from old constructions creates huge land acquisition problems and environmental pollution. Both these problems can be solved by recycling waste [...] Read more.
The shortage of natural aggregates has compelled the developers to devote their efforts to finding alternative aggregates. On the other hand, demolition waste from old constructions creates huge land acquisition problems and environmental pollution. Both these problems can be solved by recycling waste materials. The current study aims to use recycled brick aggregates (RBA) to develop eco-friendly pervious concrete (PC) and investigate the new concrete’s structural performance and pore structure distributions. Through laboratory testing and image processing techniques, the effects of replacement ratio (0%, 20%, 40%, 60%, 80%, and 100%) and particle size (4.75 mm, 9.5 mm, and 12.5 mm) on both structural performance and pore feature were analyzed. The obtained results showed that the smallest aggregate size (size = 4.75 mm) provides the best strength compared to the large sizes. The image analysis method has shown the average pore sizes of PC mixes made with smaller aggregates (size = 4.75 mm) as 1.8–2 mm, whereas the mixes prepared with an aggregate size of 9.5 mm and 12.5 mm can provide pore sizes of 2.9–3.1 mm and 3.7–4.2 mm, respectively. In summary, the results confirmed that 40–60% of the natural aggregates could be replaced with RBA without influencing both strength and pore features. Full article
(This article belongs to the Special Issue Recycled Materials in Civil and Environmental Engineering)
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Article
Correlation Analysis of Ultrasonic Pulse Velocity and Mechanical Properties of Normal Aggregate and Lightweight Aggregate Concretes in 30–60 MPa Range
Materials 2022, 15(8), 2952; https://doi.org/10.3390/ma15082952 - 18 Apr 2022
Cited by 1 | Viewed by 491
Abstract
This study classified the strength of normal aggregate concrete (NC) and lightweight aggregate concrete (LC) into three levels (30, 45, and 60 MPa). In particular, the compressive strength, ultrasonic pulse velocity, and elastic modulus were measured and analyzed at the ages of 1, [...] Read more.
This study classified the strength of normal aggregate concrete (NC) and lightweight aggregate concrete (LC) into three levels (30, 45, and 60 MPa). In particular, the compressive strength, ultrasonic pulse velocity, and elastic modulus were measured and analyzed at the ages of 1, 3, 7, and 28 days to establish the correlation between the compressive strength and the ultrasonic pulse velocity and between the elastic modulus and the ultrasonic pulse velocity. In addition, this study proposed strength and elastic modulus prediction equations as functions of the ultrasonic pulse velocity. The developed equations were compared with previously proposed strength prediction equations. The results showed that the measured mechanical properties of NC tended to be higher at all ages than in LC. However, LC45 exhibited relatively high compressive strength compared to NC45. The relative mechanical properties of LC compared to NC were the highest at 45 MPa and the lowest at 60 MPa. The relative ultrasonic pulse velocity converged at all levels as the age increased. Moreover, the correlation between the compressive strength and the ultrasonic pulse velocity in LC exceeded that of NC, and in LC, the correlation coefficient decreased as the strength increased. The correlation coefficients between the elastic modulus and the ultrasonic pulse velocity were high at all levels except for LC45. Finally, this study proposed compressive strength and elastic modulus prediction equations as an exponential function of LC. The proposed equations outperformed the previously proposed strength prediction equations. Full article
(This article belongs to the Section Construction and Building Materials)
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Review
Low-Shrinkage Resin Matrices in Restorative Dentistry-Narrative Review
Materials 2022, 15(8), 2951; https://doi.org/10.3390/ma15082951 - 18 Apr 2022
Cited by 1 | Viewed by 771
Abstract
Dimethacrylate-based resin composites restorations have become widely-used intraoral materials in daily dental practice. The increasing use of composites has greatly enhanced modern preventive and conservative dentistry. They have many superior features, especially esthetic properties, bondability, and elimination of mercury and galvanic currents. However, [...] Read more.
Dimethacrylate-based resin composites restorations have become widely-used intraoral materials in daily dental practice. The increasing use of composites has greatly enhanced modern preventive and conservative dentistry. They have many superior features, especially esthetic properties, bondability, and elimination of mercury and galvanic currents. However, polymeric materials are highly susceptible to polymerization shrinkage and stresses that lead to microleakage, biofilm formation, secondary caries, and restoration loss. Several techniques have been investigated to minimize the side effects of these shrinkage stresses. The primary approach is through fabrications and modification of the resin matrices. Therefore, this review article focuses on the methods for testing the shrinkage, as well as formulations of resinous matrices available to reduce polymerization shrinkage and its associated stress. Furthermore, this article reviews recent cutting-edge developments on bioactive low-shrinkage-stress nanocomposites to effectively inhibit the growth and activities of cariogenic pathogens and enhance the remineralization process. Full article
(This article belongs to the Special Issue Advanced Functional Materials for Biomedicinal Applications)
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Article
Identification of Multiple Mechanical Properties of Laminates from a Single Compressive Test
Materials 2022, 15(8), 2950; https://doi.org/10.3390/ma15082950 - 18 Apr 2022
Viewed by 471
Abstract
In-plane elastic and interlaminar properties of composite laminates are commonly obtained through separate experiments. In this paper, a simultaneous identification method for both properties using a single experiment is proposed. The mechanical properties of laminates were treated as uncertainties and Bayesian inference was [...] Read more.
In-plane elastic and interlaminar properties of composite laminates are commonly obtained through separate experiments. In this paper, a simultaneous identification method for both properties using a single experiment is proposed. The mechanical properties of laminates were treated as uncertainties and Bayesian inference was employed with measured strain-load curves in compression tests of laminates with embedded delamination. The strain–load curves were separated into two stages: the pre-delamination stage and the post-delamination stage. Sensitivity analysis was carried out to determine the critical properties at different stages, in order to alleviate the ill-posed problem in inference. Results showed that the in-plane Young’s modulus and shear modulus in elastic properties are dominant in the pre-delamination stage, and the interlaminar strength and type I fracture toughness in interlaminar properties are dominant in the post-delamination stage. Five times of property identification were carried out; the maximum coefficient of variation of identified properties was less than 1.11%, and the maximum error between the mean values of the identified properties and the ones from standard experiments was less than 5.44%. The proposed method can reduce time and cost in obtaining multiple mechanical properties of laminates. Full article
(This article belongs to the Special Issue Mechanical Characterization of FRP Composite Materials)
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Article
Assembly of Semiconductor Nanorods into Circular Arrangements Mediated by Block Copolymer Micelles
Materials 2022, 15(8), 2949; https://doi.org/10.3390/ma15082949 - 18 Apr 2022
Viewed by 785
Abstract
The collective properties of ordered ensembles of anisotropically shaped nanoparticles depend on the morphology of organization. Here, we describe the utilization of block copolymer micelles to bias the natural packing tendency of semiconductor nanorods and organize them into circularly arranged superstructures. These structures [...] Read more.
The collective properties of ordered ensembles of anisotropically shaped nanoparticles depend on the morphology of organization. Here, we describe the utilization of block copolymer micelles to bias the natural packing tendency of semiconductor nanorods and organize them into circularly arranged superstructures. These structures are formed as a result of competition between the segregation tendency of the nanorods in solution and in the polymer melt; when the nanorods are highly compatible with the solvent but prefer to segregate in the melt to the core-forming block, they migrate during annealing toward the core–corona interface, and their superstructure is, thus, templated by the shape of the micelle. The nanorods, in turn, exhibit surfactant-like behavior and protect the micelles from coalescence during annealing. Lastly, the influence of the attributes of the micelles on nanorod organization is also studied. The circular nanorod arrangements and the insights gained in this study add to a growing list of possibilities for organizing metal and semiconductor nanorods that can be achieved using rational design. Full article
(This article belongs to the Section Soft Matter)
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Article
Enhancement of Bond Performance of Advanced Composite Materials Used in Cable Bridge Structures Based on Tensile Tests
Materials 2022, 15(8), 2948; https://doi.org/10.3390/ma15082948 - 18 Apr 2022
Viewed by 478
Abstract
Structural steel and concrete are essential materials for the construction of social infrastructures. However, these materials undergo degradation over time, thereby causing steel corrosion. To address this problem, a fiber-reinforced polymer (FRP) is used for reinforcement. In this study, tensile tests were performed [...] Read more.
Structural steel and concrete are essential materials for the construction of social infrastructures. However, these materials undergo degradation over time, thereby causing steel corrosion. To address this problem, a fiber-reinforced polymer (FRP) is used for reinforcement. In this study, tensile tests were performed to evaluate the material properties for the application of the FRP to cable bridge structures. These tests aimed to investigate various parameters to improve bond performance. Based on experiments with different parameters, sufficient bond performance could be achieved if the following conditions are met: mortar water ≤16%, regardless of the manufacturer; a depth of splitting and steel pipe length ratio ≥75%; upward/downward directions for the mortar injection; and the use of fiber-sheet reinforcement. In addition, the steel pipe used in the test (length of 410 mm and outer diameter of 42.7 mm) performed the best in terms of workability and cost effectiveness. By conducting more accurate tests to study the basic properties of materials, more accurate conditions to accomplish sufficient bond performance can likely be achieved. This will contribute to improved cost effectiveness and safety in the use of carbon FRP cables in cable bridge constructions. Full article
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Review
Influence of Rock Dust Additives as Fine Aggregate Replacement on Properties of Cement Composites—A Review
Materials 2022, 15(8), 2947; https://doi.org/10.3390/ma15082947 - 18 Apr 2022
Cited by 1 | Viewed by 660
Abstract
Concrete production consumes enormous amounts of fossil fuels, raw materials, and is energy intensive. Therefore, scientific research is being conducted worldwide regarding the possibility of using by-products in the production of concrete. The objective is not only to identify substitutes for cement clinker, [...] Read more.
Concrete production consumes enormous amounts of fossil fuels, raw materials, and is energy intensive. Therefore, scientific research is being conducted worldwide regarding the possibility of using by-products in the production of concrete. The objective is not only to identify substitutes for cement clinker, but also to identify materials that can be used as aggregate in mortar and concrete productions. Among the potential alternative materials that can be used in cement composite production is rock dust of different geological origin. However, some adversarial effects may be encountered when using rock dust regarding the properties and durability of mortars and concrete. Therefore, comprehensive research is needed to evaluate the adequacy of rock dust use in cementitious composite production. This paper presents a comprehensive review of the scientific findings from past studies concerning the use of various geological origins of rock dust in the production of mortars and concrete. The influence of rock dust as a replacement of fine aggregates on cementitious composites was analyzed and evaluated. In this assessment and review, fresh concrete and mortar properties, i.e., workability, segregation, and bleeding, mechanical properties, and the durability of hardened concrete and mortar were considered. Full article
(This article belongs to the Special Issue Recycled Materials in Civil Engineering Application)
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Article
Characterization of Low-Cost Particulates Used as Energy Storage and Heat-Transfer Medium in Concentrated Solar Power Systems
Materials 2022, 15(8), 2946; https://doi.org/10.3390/ma15082946 - 18 Apr 2022
Cited by 3 | Viewed by 529
Abstract
Utilizing solid particles as a heat-transfer medium in concentrated solar power applications has gained growing attention lately. Unlike molten salts, solid particles offer many benefits, which include: high operating temperatures (greater than 1000 °C), a lack of freezing issues and corrosivity, abundant availability, [...] Read more.
Utilizing solid particles as a heat-transfer medium in concentrated solar power applications has gained growing attention lately. Unlike molten salts, solid particles offer many benefits, which include: high operating temperatures (greater than 1000 °C), a lack of freezing issues and corrosivity, abundant availability, high thermal energy storage capacity, a low cost, and applicability in direct irradiation. Comprehensive knowledge of thermophysical and optical properties of solid particles is essential to ensure an effective harnessing of solar energy. The most important considerations when selecting solid particles include: thermophysical and optical properties, thermal resistance, crack resistance, satisfactory health and safety risks, availability, and low cost. It is also imperative to consider optical and thermophysical characteristics that might change from what they were “as received” after cyclic heating for a long period. Therefore, the knowledge of thermal performance of particulate materials becomes significant before using them as a heat-transfer medium. In this study, some particulate materials were chosen to study their feasibilities as heat-transfer and storage media for a particle-based central receiver tower system. These particulate materials included white sand, red sand, ilmenite, and Carbobead CP. The candidate particulate materials were heated at high temperatures for 6 h and then cooled to room temperature. After that, cyclic heating was performed on the particulate materials for 500 h at 1200 °C. The optical properties were represented by weighted solar absorptance, and the thermophysical properties of the particulates were measured “as received” and after cyclic heating (aging). EDX and XRD were conducted to quantify the chemical composition and interpret the changes in appearance associated with the particulate materials after cyclic heating. The results showed a considerable agglomeration in all particulates except for white sand in the 6 h heating test, and high agglomeration in the ilmenite. A slight decrease in the optical properties in the white sand and Carbobead CP was found after the aging test. The specific heat was decreased for red and white sand. The EDX and XRD results for white sand and Carbobead CP showed chemical stability, indicating high durability and reliability. Full article
(This article belongs to the Special Issue Advanced Materials for Thermal Energy Storage)
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Article
The Structural Evolution of Semipolar (11−22) Plane AlN Tem-Plate on m-Plane Sapphire Prepared by Sputtering and High Temperature Annealing
Materials 2022, 15(8), 2945; https://doi.org/10.3390/ma15082945 - 18 Apr 2022
Viewed by 544
Abstract
In this work, the epitaxial semipolar (11–22) AlN was prepared on nonpolar m-sapphire substrate by combining sputtering and high-temperature annealing. According to our systematic measurements and analysis from XRD, Raman spectra, and AFM, the evolution of crystalline structure and morphology was investigated [...] Read more.
In this work, the epitaxial semipolar (11–22) AlN was prepared on nonpolar m-sapphire substrate by combining sputtering and high-temperature annealing. According to our systematic measurements and analysis from XRD, Raman spectra, and AFM, the evolution of crystalline structure and morphology was investigated upon increasing AlN thickness and annealing duration. The annealing operation intensively resets the lattice and improves the crystalline quality. By varying the film thickness, the contribution from the AlN-sapphire interface on crystalline quality and lattice parameters during the annealing process was investigated, and its contribution was found to be not so obvious when the thickness increased from 300 nm to 1000 nm. When the annealing was performed under durations from 1 to 5 h, the crystalline quality was found unchanged; meanwhile, the evolution of morphology was pronounced, and it means the crystalline reorganization happens prior to morphology reset. Finally, the annealing treatment enabled a zig-zag morphology on the AlN template along the sapphire [0001] direction in the plane, which potentially affects the subsequent device epitaxy process. Therefore, our results act as important experience for the semipolar nitride semiconductor laser device preparation, particularly for the epitaxy of microcavity structure through providing the crystalline evolution. Full article
(This article belongs to the Special Issue Microcavity Optics: Materials, Physics and Devices)
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Article
Effect of Slag on the Strength and Shrinkage Properties of Metakaolin-Based Geopolymers
Materials 2022, 15(8), 2944; https://doi.org/10.3390/ma15082944 - 18 Apr 2022
Cited by 1 | Viewed by 507
Abstract
Metakaolin-based geopolymers possess excellent corrosion and high-temperature resistance, which are advantageous compared to ordinary Portland cement. The addition of slag in metakaolin-based geopolymers is a promising approach to improve their mechanical properties. Thus, this study investigated the effect of slag content on the [...] Read more.
Metakaolin-based geopolymers possess excellent corrosion and high-temperature resistance, which are advantageous compared to ordinary Portland cement. The addition of slag in metakaolin-based geopolymers is a promising approach to improve their mechanical properties. Thus, this study investigated the effect of slag content on the strength and shrinkage properties of metakaolin-based geopolymers. Increasing the slag content and Na2O content was beneficial to the reaction of alkali-activated metakaolin-based geopolymers, thereby improving their compressive strength and density. After 56 days of aging, a maximum compressive strength of 86.1 MPa was achieved for a metakaolin-based geopolymer with a slag content of 50 mass%. When the Na2O content was 12%, the compressive strength of the metakaolin geopolymers with a slag content of 30% was 42.36% higher than those with a Na2O content of 8%. However, as the slag and alkali contents increased, the reaction rate of the metakaolin-based geopolymers increased, which significantly decreased the porosity, increased the shrinkage, and decreased the volumetric stability of the system. In this paper, in-depth study of the volume stability of alkali-activated metakaolin-based geopolymers plays an important role in further understanding, controlling, and utilizing the deformation behavior of geopolymers. Full article
(This article belongs to the Special Issue Modification and Performance of Novel Cementitious Materials)
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Article
Investigations of Cavitation Erosion and Corrosion Behavior of Flame-Sprayed NiCrBSi/WC-12Co Composite Coatings
Materials 2022, 15(8), 2943; https://doi.org/10.3390/ma15082943 - 18 Apr 2022
Cited by 1 | Viewed by 567
Abstract
Flame-sprayed NiCrBSi/WC-12Co composite coatings were deposited in different ratios on the surface of stainless steel. Oxyacetylene flame remelting treatment was applied to surfaces for refinement of the morphology of the layers and improvement of the coating/substrate adhesion. The performance of the coated specimens [...] Read more.
Flame-sprayed NiCrBSi/WC-12Co composite coatings were deposited in different ratios on the surface of stainless steel. Oxyacetylene flame remelting treatment was applied to surfaces for refinement of the morphology of the layers and improvement of the coating/substrate adhesion. The performance of the coated specimens to cavitation erosion and electrochemical corrosion was evaluated by an ultrasonic vibratory method and, respectively, by polarization measurements. The microstructure was investigated by means of scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX). The obtained results demonstrated that the addition of 15 wt.% WC-12Co to the self-fluxing alloy improves the resistance to cavitation erosion (the terminal erosion rate (Vs) decreased with 15% related to that of the NiCrBSi coating) without influencing the good corrosion resistance in NaCl solution. However, a further increase in WC-Co content led to a deterioration of these coating properties (the Vs has doubled related to that of the NiCrBSi coating). Moreover, the corrosion behavior of the latter composite coating was negatively influenced, a fact confirmed by increased values for the corrosion current density (icorr). Based on the achieved experimental results, one may summarize that NiCrBSi/WC-Co composite coatings are able to increase the life cycle of expensive, high-performance components exposed to severe cavitation conditions. Full article
(This article belongs to the Special Issue Metal Coatings for Wear and Corrosion Applications)
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Editorial
Special Issue: Biopolymer-Based Materials for Biomedical Engineering
Materials 2022, 15(8), 2942; https://doi.org/10.3390/ma15082942 - 18 Apr 2022
Viewed by 580
Abstract
In the field of tissue engineering and regenerative medicine (TERM), the use of traditional biomaterials capable of integrating the host tissue to promote the healing and regenerative process while it degrades has become less and less a focus of inspiration [...] Full article
(This article belongs to the Special Issue Biopolymer-Based Materials for Biomedical Engineering)
Article
Investigation of Exfoliation Efficiency of 6H-SiC Implanted Sequentially with He+ and H2+ Ions
Materials 2022, 15(8), 2941; https://doi.org/10.3390/ma15082941 - 18 Apr 2022
Viewed by 453
Abstract
Silicon carbide (SiC) is a promising material used in the advanced semiconductor industry. Fabricating SiC-on-insulator via H implantation is a good method. He and H co-implantation into Si can efficiently enhance exfoliation efficiency compared to only H implantation. In this study, 6H-SiC single [...] Read more.
Silicon carbide (SiC) is a promising material used in the advanced semiconductor industry. Fabricating SiC-on-insulator via H implantation is a good method. He and H co-implantation into Si can efficiently enhance exfoliation efficiency compared to only H implantation. In this study, 6H-SiC single crystals were implanted with He+ and H2+ dual beams at room temperature, followed by annealing at 1100 °C for 15 min, and irradiations with 60 keV He ions with a fluence of 1.5 × 1016 ions/cm−2 or 5.0 × 1016 ions/cm−2 and 100 keV H2+ ions with a fluence of 5 × 1016 ions/cm−2 were carried out. The lattice disorder was characterized by both Raman spectroscopy and transmission electron microscopy. The intensity of Raman peaks decreased with increasing fluence. No Raman shift or new phases were found. A very high numerical density of bubbles was observed as compared to single H or He implantation. Moreover, stacking faults, Frank loops and tangled dislocations were formed in the damaged layer. Surface exfoliation was inhibited by co-implantation. A possible reason for this is an increase in fracture toughness and a decrease in elastic out-of-plane strain due to dense bubbles and stacking faults. Full article
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Article
Generation of A Space-Variant Vector Beam with Catenary-Shaped Polarization States
Materials 2022, 15(8), 2940; https://doi.org/10.3390/ma15082940 - 18 Apr 2022
Viewed by 549
Abstract
We demonstrate the generation of a space-variant vector beam with catenary-shaped polarization states based on the polarization interferometry. With a spatial light modulator and a common path interferometric configuration, two orthogonally circularly polarized beams with different phase modulation overlap each other, yielding the [...] Read more.
We demonstrate the generation of a space-variant vector beam with catenary-shaped polarization states based on the polarization interferometry. With a spatial light modulator and a common path interferometric configuration, two orthogonally circularly polarized beams with different phase modulation overlap each other, yielding the vector beams. In addition, the polarization states of this vector beam are scalable to the arbitrary spatial distribution because of its great flexibility and universal applicability. It is expected that this vector beam may have many potential and intriguing applications in the micro/nano material processing, liquid crystal elements fabrication and optical micro-manipulation, and so on. Full article
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Article
Hardening and Softening Behavior of Caliber-Rolled Wire
Materials 2022, 15(8), 2939; https://doi.org/10.3390/ma15082939 - 18 Apr 2022
Cited by 1 | Viewed by 452
Abstract
The different behaviors of the mechanical properties of drawn and caliber-rolled wires with applied strain were investigated to determine the appropriate process between wire drawing and caliber rolling with consideration of materials and process conditions. Ferritic, pearlitic, and TWIP steels were drawn and [...] Read more.
The different behaviors of the mechanical properties of drawn and caliber-rolled wires with applied strain were investigated to determine the appropriate process between wire drawing and caliber rolling with consideration of materials and process conditions. Ferritic, pearlitic, and TWIP steels were drawn and caliber-rolled under the same process conditions. Caliber-rolled wires exhibited a hardening behavior in the early deformation stage and softening behavior in the later deformation stage compared with the drawn wires, regardless of the steel. The hardening behavior of the caliber-rolled wires was explained by the higher strain induced by caliber rolling compared with wire drawing, especially the higher amount of redundant work in caliber-rolled wire. The caliber-rolled wire had approximately 36% higher strain than the drawn wire and approximately 85% higher strain than nominal strain. The softening behavior of the caliber-rolled wire in later deformation stages was related to the Bauschinger effect or low-cycle fatigue effect caused by the roll geometries and loading conditions during caliber rolling. The different intersection points of the tensile strength between drawn and caliber-rolled wires with the steels were attributed to the different strain hardening rates of each steel. Between the options of the caliber rolling and wire drawing processes, the appropriate process should be selected according to the strain hardening rate of the material and the amount of plastic deformation. For instance, when the wires need to deform at high levels, wire drawing is the better process because of the appearance of the Bauschinger effect in caliber-rolled wire. Full article
(This article belongs to the Topic Advanced Forming Technology of Metallic Materials)
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Article
Experimental Study on the Mix Proportion and Mechanical Properties of New Underwater Cementitious Filling Materials
Materials 2022, 15(8), 2938; https://doi.org/10.3390/ma15082938 - 18 Apr 2022
Viewed by 520
Abstract
Considering that it is difficult for traditional materials to simultaneously meet the requirements for filling grouting of water-filled karst caves and subsequent shield tunneling, an environmentally friendly and controllable new underwater cementitious filling material (NUC-FM) is developed, with abandoned shield mud as the [...] Read more.
Considering that it is difficult for traditional materials to simultaneously meet the requirements for filling grouting of water-filled karst caves and subsequent shield tunneling, an environmentally friendly and controllable new underwater cementitious filling material (NUC-FM) is developed, with abandoned shield mud as the basic raw material. Through laboratory tests, the mechanical property parameters of NUC-FM are tested, and its micromechanism is analyzed. The research results show that there is excellent synergistic interactions among shield mud, cement, flocculant, fly ash and other raw materials. The NUC-FM grouting filling material with superior performance can be prepared when the water binder ratio is between 0.45 and 0.6 and the water consumption is between 270 and 310 kg/m3. It has the characteristics of non-dispersion underwater and moderate consolidated body strength. The compressive strength of the NUC-FM consolidated body samples under each mix proportion is much higher than 0.5 MPa, which meets the technical strength requirements of a construction site, and the microstructure shows that there is an obvious dense and stable block structure inside. The cost of the NUC-FM prepared with an optimized mix proportion is only 34.57 dollars/m3, which is far lower than the market purchase price of concrete and cement mortar. It can be predicted that the NUC-FM is an ideal filling grouting material for water-filled karst caves in shield tunnels in water-rich karst areas. Full article
(This article belongs to the Topic Pipeline and Underground Space Technology)
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Article
Fatigue Crack Growth Analysis under Constant Amplitude Loading Using Finite Element Method
Materials 2022, 15(8), 2937; https://doi.org/10.3390/ma15082937 - 18 Apr 2022
Viewed by 590
Abstract
Damage tolerant design relies on accurately predicting the growth rate and path of fatigue cracks under constant and variable amplitude loading. ANSYS Mechanical R19.2 was used to perform a numerical analysis of fatigue crack growth assuming a linear elastic and isotropic material subjected [...] Read more.
Damage tolerant design relies on accurately predicting the growth rate and path of fatigue cracks under constant and variable amplitude loading. ANSYS Mechanical R19.2 was used to perform a numerical analysis of fatigue crack growth assuming a linear elastic and isotropic material subjected to constant amplitude loading. A novel feature termed Separating Morphing and Adaptive Remeshing Technology (SMART) was used in conjunction with the Unstructured Mesh Method (UMM) to accomplish this goal. For the modified compact tension specimen with a varied pre-crack location, the crack propagation path, stress intensity factors, and fatigue life cycles were predicted for various stress ratio values. The influence of stress ratio on fatigue life cycles and equivalent stress intensity factor was investigated for stress ratios ranging from 0 to 0.8. It was found that fatigue life and von Mises stress distribution are substantially influenced by the stress ratio. The von Mises stress decreased as the stress ratio increased, and the number of fatigue life cycles increased rapidly with the increasing stress ratio. Depending on the pre-crack position, the hole is the primary attraction for the propagation of fatigue cracks, and the crack may either curve its direction and grow towards it, or it might bypass the hole and propagate elsewhere. Experimental and numerical crack growth studies reported in the literature have validated the findings of this simulation in terms of crack propagation paths. Full article
(This article belongs to the Topic Numerical Modeling on Metallic Materials)
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Article
Study on Deterioration Law and Mechanism of Gray Brick Due to Salt Crystallization
Materials 2022, 15(8), 2936; https://doi.org/10.3390/ma15082936 - 18 Apr 2022
Viewed by 526
Abstract
Salinization has an important impact on the degradation of ancient masonry buildings, and systematically mastering the law of salt migration and degradation of ancient masonry buildings is an important part of the protection of ancient buildings. In this paper, the damage law of [...] Read more.
Salinization has an important impact on the degradation of ancient masonry buildings, and systematically mastering the law of salt migration and degradation of ancient masonry buildings is an important part of the protection of ancient buildings. In this paper, the damage law of gray bricks under the action of salt crystallization is studied. The orthogonal test method is used to carry out cyclic degradation tests on gray bricks. The nominal strength is proposed as a mechanical parameter to measure the structural damage of grey bricks, and the change in compressive strength and crystallization pressure of the samples after the test is measured and analyzed. The results show that the damage of different salts in the gray bricks shows a certain difference. Magnesium sulfate and sodium chloride cause significant damage to the surface of the gray bricks, while calcium chloride does not cause significant damage to the surface of the gray bricks. When the concentrations of sodium chloride solution, calcium chloride solution and magnesium sulfate solution are less than 13.73 mol/L, 11.47 mol/L and 17 mol/L, respectively, the nominal strength of gray brick samples increases; In the range of 9.9 mol/L and 4.73–8.94 mol/L, the crystallization pressure began to appear inside the sample. The research results provide an important scientific basis for evaluating the damage caused by salting to the damage of porous ancient building materials such as masonry. Full article
(This article belongs to the Section Construction and Building Materials)
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Article
Material Selection Process for Acoustic and Vibration Applications Using the Example of a Plate Resonator
Materials 2022, 15(8), 2935; https://doi.org/10.3390/ma15082935 - 18 Apr 2022
Viewed by 507
Abstract
In this work, a new method for selecting suitable materials is presented. This method has a high potential for a variety of engineering applications, such as the design of sound-absorbing and vibration-loaded structures, where a large number of different requirements have to be [...] Read more.
In this work, a new method for selecting suitable materials is presented. This method has a high potential for a variety of engineering applications, such as the design of sound-absorbing and vibration-loaded structures, where a large number of different requirements have to be met. The method is based on the derivation of functional dependencies of selected material parameters. These dependencies can be used in parameter studies to consider parameter combinations that lie in the range of real existing and targeted material groups. This allows the parameter space to be reduced, the calculation to be accelerated, and suitable materials to be (pre-)selected for the respective application, which contributes to a more target-oriented design. The method is applied to the example of a plate resonator. For this purpose, a semi-analytical model is implemented to calculate the transmission loss as well as the reflected and dissipated sound power of plate silencers, taking into account the influence of flow velocity and fluid temperature on the performance of plate silencers. Full article
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Editorial
Editorial Special Issue: “Advance Polymeric Materials: Synthesis, Properties and Applications”
Materials 2022, 15(8), 2934; https://doi.org/10.3390/ma15082934 - 18 Apr 2022
Viewed by 461
Abstract
As a consequence of their properties of lightness, strength, versatility, low toxicity, low cost and durability, the 20th century saw the beginning of the use of polymers as disruptive materials [...] Full article
(This article belongs to the Special Issue Advanced Polymeric Materials: Synthesis, Properties, and Applications)
Article
Mechanical Performance of Portland Cement, Coarse Silica Fume, and Limestone (PC-SF-LS) Ternary Portland Cements
Materials 2022, 15(8), 2933; https://doi.org/10.3390/ma15082933 - 18 Apr 2022
Viewed by 605
Abstract
Ternary Portland cements composed of coarse silica fume (SF), limestone (LS), and Portland cement (PC) can afford some environmental advantages by reducing the clinker content in Portland cements. These cements will help to reduce the clinker factor target from 0.78 to 0.60 by [...] Read more.
Ternary Portland cements composed of coarse silica fume (SF), limestone (LS), and Portland cement (PC) can afford some environmental advantages by reducing the clinker content in Portland cements. These cements will help to reduce the clinker factor target from 0.78 to 0.60 by 2050 with the aim to be climate neutral. Silica fume (SF) possesses pozzolanic properties that enhance mechanical strength and durability. By contrast, limestone powder has three main outcomes, i.e., filler, dilution, and chemical effects. The first reduces porosity and refines the microstructure of mortars and concretes. The second decreases the amount of hydration products and increases the porosity; the third one promotes the appearance of carboaluminates and reduces porosity. This paper covers the mechanical properties of Portland cement-limestone-coarse silica fume ternary cements, and its synergetic mechanism. Compressive and flexural strength of mortar at 2, 7, 14 and 28 days was performed. Coarse silica fume has a minor contribution on the nucleation effect compared to ground limestone at early ages. The nucleation and filler effects, at early ages, are less pronounced in coarse and very fine limestone powder. The highest compressive strength at 28 days is reached with the lowest content of coarse silica fume (3%). Mortar mixes made with a high level of limestone presented a delay in the compressive strength development. Full article
(This article belongs to the Special Issue Research on Novel Sustainable Binders, Concretes and Composites)
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Article
High Humidity Response of Sol–Gel-Synthesized BiFeO3 Ferroelectric Film
Materials 2022, 15(8), 2932; https://doi.org/10.3390/ma15082932 - 17 Apr 2022
Cited by 2 | Viewed by 656
Abstract
In this work, a BiFeO3 film is prepared via a facile sol–gel method, and the effects of the relative humidity (RH) on the BiFeO3 film in terms of capacitance, impedance and current–voltage (IV) are explored. The capacitance [...] Read more.
In this work, a BiFeO3 film is prepared via a facile sol–gel method, and the effects of the relative humidity (RH) on the BiFeO3 film in terms of capacitance, impedance and current–voltage (IV) are explored. The capacitance of the BiFeO3 film increased from 25 to 1410 pF with the increase of RH from 30% to 90%. In particular, the impedance varied by more than two orders of magnitude as RH varied between 30% and 90% at 10 Hz, indicating a good hysteresis and response time. The mechanism underlying humidity sensitivity was analyzed by complex impedance spectroscopy. The adsorption of water molecules played key roles at low and high humidity, extending the potential application of ferroelectric BiFeO3 films in humidity-sensitive devices. Full article
(This article belongs to the Special Issue Microstructural Design and Processing Control of Advanced Ceramics)
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Review
Review on Preparation Technology and Properties of Refractory High Entropy Alloys
Materials 2022, 15(8), 2931; https://doi.org/10.3390/ma15082931 - 17 Apr 2022
Viewed by 1104
Abstract
Refractory high entropy alloys have broad application prospects due to their excellent comprehensive properties in high temperature environments, and they have been widely implemented in many complex working conditions. According to the latest research reports, the preparation technology of bulk and coating refractory [...] Read more.
Refractory high entropy alloys have broad application prospects due to their excellent comprehensive properties in high temperature environments, and they have been widely implemented in many complex working conditions. According to the latest research reports, the preparation technology of bulk and coating refractory high entropy alloys are summarized, and the advantages and disadvantages of each preparation technology are analyzed. In addition, the properties of refractory high entropy alloys, such as mechanical properties, wear resistance, corrosion resistance, oxidation resistance, and radiation resistance are reviewed. The existing scientific problems of refractory high entropy alloys, at present, are put forward, which provide reference for the development and application of refractory high entropy alloys in the future, especially for plasma-facing materials in nuclear fusion reactors. Full article
(This article belongs to the Topic Metallurgical and Materials Engineering)
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Article
Laboratory Test and Geochemical Modeling of Cement Paste Degradation, in Contact with Ammonium Chloride Solution
Materials 2022, 15(8), 2930; https://doi.org/10.3390/ma15082930 - 17 Apr 2022
Cited by 1 | Viewed by 554
Abstract
Concrete tanks, in coke wastewater treatment plants, are exposed to aggressive wastewater with high ammonium and chloride content, deteriorating the concrete binder. Due to this, toxic compounds may migrate to the environment. The results of the experimental work presented confirmed the changes in [...] Read more.
Concrete tanks, in coke wastewater treatment plants, are exposed to aggressive wastewater with high ammonium and chloride content, deteriorating the concrete binder. Due to this, toxic compounds may migrate to the environment. The results of the experimental work presented confirmed the changes in the phase, microstructure and concentration of chlorides caused by the penetration of NH4Cl into the hardened cement paste in dry conditions. Geochemical modeling of the interactions between the aggressive solution, the cement stone matrix and the pore water was performed in order to track the destruction process effects. The results are useful for condition assessment of the structures operating under occasional immersion. Full article
(This article belongs to the Special Issue Development and Research of Cementitious Materials)
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Article
Assessment of the Destruction of a Fibre Cement Board Subjected to Fire in a Large-Scale Study
Materials 2022, 15(8), 2929; https://doi.org/10.3390/ma15082929 - 17 Apr 2022
Viewed by 543
Abstract
This article presents the results of a study involving the assessment of the structural destruction of fibre cement boards taken from a large-scale model subjected to fire. These were subjected to a three-point bending test using the acoustic emission method. The analysis of [...] Read more.
This article presents the results of a study involving the assessment of the structural destruction of fibre cement boards taken from a large-scale model subjected to fire. These were subjected to a three-point bending test using the acoustic emission method. The analysis of the obtained results took into account the course of bending stresses σm, the modulus of rupture (MOR), the number of acoustic emission events Nzd and the sum of EA events ∑Nzd. The conducted tests showed that the samples subjected to fire exhibited a clear decrease, up to 72%, in the recorded sum of EA events compared to a reference board (not subjected to fire). The analysis of the obtained modulus of rupture (MOR) values showed a similar trend—the reduction of the modulus of rupture for the degraded samples was in the range of 66–96%. In order to illustrate the changes taking place in the structure of the tested plates more precisely, analyses were carried out using the optical method and a digital microscope. This method may be sufficient for the final evaluation of degraded samples. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering (2nd Edition))
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