Materials

24 pages, 7109 KiB

Open AccessArticle

Experimental Study on Proportion Optimization of Rock-like Materials Based on Genetic Algorithm Inversion

by Hui Su, Shaoxing Liu, Baowen Hu, Bowen Nan, Xin Zhang, Xiaoqing Han and Xiao Zhang

Materials 2024, 17(19), 4940; https://doi.org/10.3390/ma17194940 - 9 Oct 2024

Viewed by 1014

It is very important to clarify the optimization method of the rock-like material ratio for accurately characterizing mechanical properties similar to the original rock. In order to explore the optimal ratio of rock-like materials in gneissic granite, the water–paste ratio, iron powder content [...] Read more.

It is very important to clarify the optimization method of the rock-like material ratio for accurately characterizing mechanical properties similar to the original rock. In order to explore the optimal ratio of rock-like materials in gneissic granite, the water–paste ratio, iron powder content and coarse sand content were selected as the influencing factors of the ratio. An orthogonal test design and sensitivity analysis of variance were used to obtain the significant influencing factors of the ratio factors on seven macroscopic mechanical parameters, including compressive strength σ_c, tensile strength σ_t, shear strength τ_f, elastic modulus E, Poisson’s ratio ν, internal friction angle φ and cohesion c. A multivariate linear regression equation was constructed to obtain the quantitative relationship between the significant ratio factors and the macroscopic mechanical parameters. Finally, a rock-like material ratio optimization program based on genetic algorithm inversion was written. The results show that the water–paste ratio had extremely significant effects on σ_c, σ_t, τ_f, E, ν and c. The iron powder content had a highly significant effect on σ_c, σ_t, τ_f and c, and it had a significant effect on ν and φ. Coarse sand content had a significant effect on σ_c, E and c. The multiple linear regression model has good reliability after testing, which can provide theoretical support for predicting the macroscopic mechanical parameters of rock-like materials to a certain extent. After testing, the ratio optimization program works well. When the water–paste ratio is 0.5325, the iron powder content is 3.975% and the coarse sand content is 15.967%, it is the optimal ratio of rock-like materials. Full article

(This article belongs to the Section Materials Simulation and Design)

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20 pages, 3485 KiB

Open AccessArticle

Performance-Based Design of Ferronickel Slag Alkali-Activated Concrete for High Thermal Load Applications

by Andres Arce, Anastasija Komkova, Catherine G. Papanicolaou and Thanasis C. Triantafillou

Materials 2024, 17(19), 4939; https://doi.org/10.3390/ma17194939 - 9 Oct 2024

Viewed by 625

Abstract

This study aimed to develop optimized alkali-activated concrete using ferronickel slag for high-temperature applications, focusing on minimizing environmental impact while maintaining high compressive strength and slump. A response surface methodology, specifically the mixture design of experiments, was employed to optimize five components: water, [...] Read more.

This study aimed to develop optimized alkali-activated concrete using ferronickel slag for high-temperature applications, focusing on minimizing environmental impact while maintaining high compressive strength and slump. A response surface methodology, specifically the mixture design of experiments, was employed to optimize five components: water, FNS-based alkali-activated binder, and three aggregate sizes. Twenty concrete mixes were tested for slump and compressive strength before and after exposure to 600 °C for two hours. The optimal mix achieved 88 MPa compressive strength before heat exposure and 34 MPa after, with a slump of 140 mm. An upscaled version with improved workability (210 mm slump) maintained similar unheated strength but showed reduced post-heating strength (23.5 MPa). Replacing limestone with olivine aggregates in the upscaled mix resulted in 65 MPa unheated and 32 MPa post-heating strengths. Life Cycle Analysis revealed that the optimized ferronickel slag alkali-activated concrete’s CO₂ emissions were 77% lower than those of ordinary Portland cement concrete of equivalent strength. This approach demonstrated the applicability of mixture design of experiments as an alternative design methodology for alkali activated concrete, providing a valuable performance-based design tool to advance the application of alkali-activated concrete in the construction industry, where no prescriptive standards for alkali-activated ferronickel concrete mix design exist. The study concluded that the developed ferronickel slag alkali-activated concrete, obtained through a performance-based mixture design methodology, offers a promising, environmentally friendly alternative for high-strength, high-temperature applications in construction. Full article

(This article belongs to the Special Issue The Development of Sustainable Concrete with Solid Waste and By-Products)

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22 pages, 6453 KiB

Open AccessArticle

Application of Experimental Studies of Humidity and Temperature in the Time Domain to Determine the Physical Characteristics of a Perlite Concrete Partition

by Anna Szymczak-Graczyk, Gabriela Gajewska, Barbara Ksit, Ireneusz Laks, Wojciech Kostrzewski, Marek Urbaniak and Tomasz Pawlak

Materials 2024, 17(19), 4938; https://doi.org/10.3390/ma17194938 - 9 Oct 2024

Viewed by 539

Abstract

These days, the use of natural materials is required for sustainable and consequently plus-, zero- and low-energy construction. One of the main objectives of this research was to demonstrate that pelite concrete block masonry can be a structural and thermal insulation material. In [...] Read more.

These days, the use of natural materials is required for sustainable and consequently plus-, zero- and low-energy construction. One of the main objectives of this research was to demonstrate that pelite concrete block masonry can be a structural and thermal insulation material. In order to determine the actual thermal insulation parameters of the building partition, in situ experimental research was carried out in real conditions, taking into account the temperature distribution at different heights of the partition. Empirical measurements were made at five designated heights of the partition with temperature and humidity parameters varying over time. The described experiment was intended to verify the technical parameters of perlite concrete in terms of its thermal insulation properties as a construction material used for vertical partitions. It was shown on the basis of the results obtained that the masonry made of perlite concrete blocks with dimensions of 24 × 24.5 × 37.5 cm laid on the mounting foam can be treated as a building element that meets both the structural and thermal insulation requirements of vertical single-layer partitions. However, it is important for the material to work in a dry environment, since, as shown, a wet perlite block has twice the thermal conductivity coefficient. The results of the measurements were confirmed, for they were known from the physics of buildings, the general principles of the formation of heat and the moisture flow in the analysed masonry of a perlite block. Illustrating this regularity is shown from the course of temperature and moisture in the walls. The proposed new building material is an alternative to walls with a layer of thermal insulation made of materials such as polystyrene or wool and fits into the concept of sustainable construction, acting against climate change, reducing building operating costs, improving living and working conditions as well as fulfilling international obligations regarding environmental goals. Full article

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23 pages, 95742 KiB

Open AccessArticle

Research on the Physical Properties of an Eco-Friendly Layered Geopolymer Composite

by Agnieszka Przybek and Michał Łach

Materials 2024, 17(19), 4937; https://doi.org/10.3390/ma17194937 - 9 Oct 2024

Viewed by 1058

Abstract

Building envelopes with natural fibers are the future of sustainable construction, combining ecology and energy efficiency. The geopolymer building envelope was reinforced with innovative composite bars and two types of natural insulation (coconut mats and flax/hemp non-woven fabrics) were used as the core [...] Read more.

Building envelopes with natural fibers are the future of sustainable construction, combining ecology and energy efficiency. The geopolymer building envelope was reinforced with innovative composite bars and two types of natural insulation (coconut mats and flax/hemp non-woven fabrics) were used as the core material. A 10 mol sodium hydroxide solution with an aqueous sodium silicate solution was used for the alkaline activation of the geopolymers. The purpose of this study was to confirm the feasibility of producing geopolymer composites with insulating layers made of renewable materials, which would have compressive strengths like those of C25/30-grade concrete and thermal conductivity coefficients like those of lightweight concrete. This publication presents the results of physicochemical tests on the base materials (oxide (XRF) and mineral phase (XRD) analysis as well as morphology and EDS) and studies the physical (density measurements), mechanical (flexural and compressive strength tests) and insulating properties (thermal conductivity measurements) of the finished sandwich partitions. The composites achieved a flexural strength of 7 MPa, a compressive strength of up to 30 MPa and a decrease in the thermal conductivity coefficient of about 60%. The research demonstrates contribution to sustainable construction by developing geopolymer composites, offering both structural integrity and superior thermal insulation. This innovation not only reduces reliance on traditional, carbon-intensive materials but also promotes the use of eco-friendly resources, significantly lowering the carbon footprint of construction. The integration of natural fibers into geopolymer matrices addresses key environmental concerns, advancing a rapidly growing field that aligns with global efforts toward energy efficiency, waste reduction, and circular economy principles in building design. Full article

(This article belongs to the Special Issue Research on Geopolymers: Synthesis Methods, Manufacturing Process, Properties and Applications)

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14 pages, 7850 KiB

Open AccessArticle

Composite Materials Used for Dental Fillings

by Joanna Wysokińska-Miszczuk, Katarzyna Piotrowska, Michał Paulo and Monika Madej

Materials 2024, 17(19), 4936; https://doi.org/10.3390/ma17194936 - 9 Oct 2024

Viewed by 888

Abstract

This article explores the properties of composite materials employed in dental fillings. A traditional nano-hybrid composite containing nanofiller particles exceeding 82% by weight served as a benchmark. The remaining samples were fabricated from ormocer resin, maintaining an identical nanofiller content of 84%. In [...] Read more.

This article explores the properties of composite materials employed in dental fillings. A traditional nano-hybrid composite containing nanofiller particles exceeding 82% by weight served as a benchmark. The remaining samples were fabricated from ormocer resin, maintaining an identical nanofiller content of 84%. In all specimens, the nanoparticles were dispersed randomly within the matrix. This study presents findings from investigations into surface geometry, hardness, wettability, and tribological behavior. The microscopic observations revealed that ormocer-based samples exhibited greater surface roughness than those composed of the traditional composite. Hardness testing indicated that both ceramic addition and sample preparation significantly influenced mechanical properties. Ceramic-enhanced samples demonstrated superior hardness, surpassing the reference composite by 30% and 43%, respectively. Contact angle measurements revealed hydrophilic characteristics in the classic composite, contrasting with the hydrophobic nature of ceramic-containing samples. Tribological evaluations revealed the superiority of the classic composite in terms of friction coefficients and volumetric wear compared to ormocer-based materials. Full article

(This article belongs to the Special Issue Advanced Biomaterials for Dental Applications)

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11 pages, 6924 KiB

Open AccessArticle

Preparation of Imidazole Compounds as Latent Curing Agents and Their Application in RGB LED Packaging

by Jiangcong Chen, Shujuan Zhang, Biwen Li, Pinghu Chen and Hengfeng Li

Materials 2024, 17(19), 4935; https://doi.org/10.3390/ma17194935 - 9 Oct 2024

Viewed by 639

Abstract

LED packaging miniaturization has raised more requirements for LED materials. As a material contacting the LED chip directly, the reliability of LED non-conductive adhesive has also garnered increasing attention. This study optimized the formula for non-conductive adhesives for an imidazole curing system. The [...] Read more.

LED packaging miniaturization has raised more requirements for LED materials. As a material contacting the LED chip directly, the reliability of LED non-conductive adhesive has also garnered increasing attention. This study optimized the formula for non-conductive adhesives for an imidazole curing system. The optimized composition of the adhesive is 25%wt for the curing agent and 30%wt for the silica. The prepared non-conductive adhesive has a 7-day pot life and 9-month storage stability. The shear strength reached 87 g and 72 g at 25 °C and 160 °C, respectively. The reliability of the LED modules packaged with the non-conductive adhesive was researched. The green and blue light intensity change was 4.7%, 43.7%, respectively, indicating good anti-aging properties. The blue light decay was mainly due to adhesive aging. The non-conductive adhesive effectively prevented “caterpillar” growth. This provides useful and practical guidelines for industry for applications of adhesive in different packages. Full article

(This article belongs to the Special Issue Advances in Materials Science and Engineering—in Celebration of 55th Anniversary of the Faculty of Technical Sciences, Warmia and Mazury University in Olsztyn, Poland)

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23 pages, 14785 KiB

Open AccessArticle

Experimental Study of Used Wind Turbine Blades for Their Reuse in Slope and Trench Protection

by Lidia Buda-Ożóg, Anna Halicka, Mirosław Broniewicz, Joanna Zięba, Damian Nykiel, Łukasz Jabłoński and Filip Broniewicz

Materials 2024, 17(19), 4934; https://doi.org/10.3390/ma17194934 - 9 Oct 2024

Viewed by 823

Abstract

This article presents the results of an experimental study carried out to assess the possibility of using waste wind turbine blades as retaining wall structures for slopes and trenches. The use of Vestas and LM-type blades as retaining wall components was assumed, based [...] Read more.

This article presents the results of an experimental study carried out to assess the possibility of using waste wind turbine blades as retaining wall structures for slopes and trenches. The use of Vestas and LM-type blades as retaining wall components was assumed, based on ‘columns’ made of Vestas-type closed profiles filled with concrete and ‘slabs’ of fragments extracted from LM-type blades. The results of the tests and comparisons of the displacement and strain values of the components obtained using different measurement methods are presented in this paper. The force–strain and force–displacement relationships obtained from the tests were used to validate numerical models of slope protection walls and excavations designed from used wind turbine blades. According to our research, there is a high degree of variability in the strength parameters and deformation of the composite elements made from the wind turbine blades. Therefore, in the case of this type of material, characterized by a significant variation in carrying capacity, deformability, and the nature of the failures, the use of different measurement methods makes it possible to obtain much of the data necessary for assessing the reusability of wind turbine blades in building. Full article

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13 pages, 7643 KiB

Open AccessArticle

Influence of Annealing and Aging Parameters on the Microstructure and Properties of 1200 MPa Grade Cold-Rolled Dual-Phase Steel

by Xiaoyue Ma, Xiaohong Chu, Yuebiao Yang, Hongzhou Lu, Wenjun Wang and Zhengzhi Zhao

Materials 2024, 17(19), 4933; https://doi.org/10.3390/ma17194933 - 9 Oct 2024

Viewed by 774

Abstract

With the rapid development of the automotive industry, the requirements for bodywork materials are not only focused on high strength but also on improved forming properties. To develop a new generation of automotive steels with higher strength–plasticity matching, a high elongation 1200 MPa [...] Read more.

With the rapid development of the automotive industry, the requirements for bodywork materials are not only focused on high strength but also on improved forming properties. To develop a new generation of automotive steels with higher strength–plasticity matching, a high elongation 1200 MPa grade V-Nb microalloyed cold-rolled reinforced formable dual-phase steel was developed in this experiment through rational compositional design and precise process machining. The properties of the test steel are improved by varying the over-aging temperature as well as the annealing temperature to achieve a good strength–plasticity balance. The results show that as the aging temperature increases, the tensile strength and yield strength of the test steel decrease, while the elongation continues to increase. At an aging temperature of 310 °C, the steel exhibits not only high strength but also better ductility. As the annealing temperature increases, the tensile strength and yield strength of the test steel initially increase and then decrease, while the elongation continues to increase. When the heat treatment process involves an annealing temperature of 860 °C and an over-aging temperature of 310 °C, the test steel achieves the best strength–plasticity balance. Full article

(This article belongs to the Special Issue Physical Metallurgy of Metals and Alloys (3rd Edition))

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3 pages, 484 KiB

Open AccessCorrection

Correction: Zhao et al. Research on the Formation Conditions and Preventive Measures of Uranium Precipitates during the Service Process of Medical Isotope Production Reactors. Materials 2024, 17, 945

by Yanli Zhao, Yuan Gao, Xinyue Li, Yi Le, Yang Zhang, Jie Qiu and Yong Xin

Materials 2024, 17(19), 4932; https://doi.org/10.3390/ma17194932 - 9 Oct 2024

Viewed by 402

Abstract

There were two errors in the original publication [...] Full article

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9 pages, 3702 KiB

Open AccessArticle

Synthesis of β-Ga₂O₃:Mg Thin Films by Electron Beam Evaporation and Postannealing

by Weitao Fan, Sairui Li, Wei Ren, Yanhan Yang, Yixuan Li, Guanghui Liu and Weili Wang

Materials 2024, 17(19), 4931; https://doi.org/10.3390/ma17194931 - 9 Oct 2024

Viewed by 693

Abstract

Doping divalent metal cations into Ga₂O₃ films plays a key role in adjusting the conductive behavior of the film. N-type high-resistivity β-Ga₂O₃:Mg films were prepared using electron beam evaporation and subsequent postannealing processing. Various characterization [...] Read more.

Doping divalent metal cations into Ga₂O₃ films plays a key role in adjusting the conductive behavior of the film. N-type high-resistivity β-Ga₂O₃:Mg films were prepared using electron beam evaporation and subsequent postannealing processing. Various characterization methods (X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, etc.) revealed that the Mg content plays an important role in affecting the film quality. Specifically, when the Mg content in the film is 3.6%, the S2 film’s resistivity, carrier content, and carrier mobility are 59655.5 Ω·cm, 1.95 × 10¹⁴ cm³/C, and 0.53682 cm²/Vs. Also, the film exhibits a smoother surface, more refined grains, and higher self-trapped exciton emission efficiency. The Mg cation mainly substitutes the Ga⁺ cation at a tetrahedral site, acting as a trap for self-trapped holes. Full article

(This article belongs to the Special Issue Design, Preparation, and Microstructural Characterization of High Entropy Materials)

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18 pages, 6074 KiB

Open AccessArticle

Study on Cavity Filling Defects and Tensile Properties of L-Shaped Profiled Rings

by Tiewen Hao, Junzhe Chen, Tao Zhang, Zhenyang Qin and Yunxin Wu

Materials 2024, 17(19), 4930; https://doi.org/10.3390/ma17194930 - 9 Oct 2024

Viewed by 540

Abstract

Severe cavity filling defects and poor mechanical properties increase the difficulty in the integrated forming of L-shaped profiled rings due to its asymmetrical section geometry. A novel rolling method of a C-shaped ring was proposed in this study, and two symmetric L-shaped rings [...] Read more.

Severe cavity filling defects and poor mechanical properties increase the difficulty in the integrated forming of L-shaped profiled rings due to its asymmetrical section geometry. A novel rolling method of a C-shaped ring was proposed in this study, and two symmetric L-shaped rings were prepared simultaneously. A numerical model of C-shaped ring rolling was established, and the cavity filling defects in different directions and the overall forming defect were defined for a qualitative analysis of the geometry’s accuracy. The effect of the rolling parameters on the forming defects and ring quality was investigated. The forming defects increased with an increase in the groove depth ratio as well as decreases in the groove angle and rolling ratio. The feeding strategy with a constant ring growth velocity led to the best geometric accuracy and strain uniformity of the C-shaped rings. Optimized rolling parameters can be acquired by the Box–Behnken optimization method with multi-objective optimization of the rolling stability and ring quality. An experiment of C-shaped ring rolling was successfully prepared, based on the optimized parameters. The hardness distribution on the cross-section was symmetric and uniform. The C-shaped ring showed obvious anisotropy of the tensile properties of the cast ring’s blank, and heat treatment had little effect on the improvement of the isotropy. Full article

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14 pages, 33689 KiB

Open AccessArticle

Optimisation of Active Magnetic Elements in Beam-like Structures—Numerical Modelling Studies

by Katarzyna Majewska

Materials 2024, 17(19), 4929; https://doi.org/10.3390/ma17194929 - 9 Oct 2024

Viewed by 695

Abstract

This paper explores integrating advanced materials, including magnetic shape memory alloys, magnetorheological fluids, and classical shape memory alloys, within structural elements to achieve exceptional physical properties. When these materials are integrated within structures—whether as wires, actuators, or dampers—they provide the structures with unique [...] Read more.

This paper explores integrating advanced materials, including magnetic shape memory alloys, magnetorheological fluids, and classical shape memory alloys, within structural elements to achieve exceptional physical properties. When these materials are integrated within structures—whether as wires, actuators, or dampers—they provide the structures with unique static, dynamic, and damping characteristics not commonly found in nature. This study aimed to evaluate the efficacy of these active materials in enhancing the performance of beam-like structures. This investigation was conducted through a comprehensive numerical analysis, focusing on a composite beam. The study examined the impact of different active elements, their position within the structure, and their influence on key dynamic properties. Additionally, a simplified damage scenario was considered, wherein the adverse effects of structural damage were mitigated through the strategic application of these materials. Numerical simulations were carried out using the finite element method, with custom computational codes developed in MATLAB. The findings of these simulations are presented and discussed in this paper. Full article

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14 pages, 24410 KiB

Open AccessFeature PaperArticle

Characteristics of Merging Plasma Plumes for Materials Process Using Two Atmospheric Pressure Plasma Jets

by Sang Un Jeon, Jae Wan Kim, Hyun-Young Lee, Gyoo-Cheon Kim and Hae June Lee

Materials 2024, 17(19), 4928; https://doi.org/10.3390/ma17194928 - 9 Oct 2024

Viewed by 597

Abstract

Atmospheric pressure plasma jets (APPJs) have attracted significant attention due to their ability to generate plasma without vacuum systems, facilitating their use in small areas of plasma processing applications across various fields, including medicine, surface treatment, and agriculture. In this study, we investigate [...] Read more.

Atmospheric pressure plasma jets (APPJs) have attracted significant attention due to their ability to generate plasma without vacuum systems, facilitating their use in small areas of plasma processing applications across various fields, including medicine, surface treatment, and agriculture. In this study, we investigate the interaction between two helium plasma jets, focusing on the effects of varying flow rate, voltage, and directional angle. By examining both in-phase and out-of-phase configurations, this research aims to elucidate the fundamental mechanisms of plasma plume merging, which has critical implications for optimizing plasma-based material processing systems. We demonstrate that while increasing voltage and flow rate for the in-phase condition leads to an extended plasma plume length, the plumes do not merge, maintaining a minimal gap. Conversely, plasma plume merging is observed for the out-of-phase condition, facilitated by forming a channel between the jets. This study further explores the impact of these merging phenomena on plasma chemistry through optical emission spectroscopy, revealing substantial differences in the emission intensities of OH, the second positive system of

N_{2}

, and the first negative system of

N_{2}^{+}

. These findings offer valuable insights into controlling plasma jet interactions for enhanced efficiency in plasma-assisted processes, particularly where plume merging can be leveraged to improve the treatment area and intensity. Full article

(This article belongs to the Special Issue Advanced Plasma Technology in Material Synthesis, Processing and Analysis)

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16 pages, 8633 KiB

Open AccessArticle

Stress-Strain Behavior and Strength Development of High-Amount Phosphogypsum-Based Sustainable Cementitious Materials

by Ying Shi, Yue Li, Hongwei Wang, Yixuan Ma and Xinyue Lu

Materials 2024, 17(19), 4927; https://doi.org/10.3390/ma17194927 - 9 Oct 2024

Viewed by 742

Abstract

Phosphogypsum is a common industrial solid waste that faces the challenges of high stockpiling and low utilization rates. This study focuses on the mechanical properties and internal characteristics of cementitious materials with a high phosphogypsum content. Specifically, we examined the effects of varying [...] Read more.

Phosphogypsum is a common industrial solid waste that faces the challenges of high stockpiling and low utilization rates. This study focuses on the mechanical properties and internal characteristics of cementitious materials with a high phosphogypsum content. Specifically, we examined the effects of varying amounts of ground granulated blast furnace slag (5–28%), fly ash (5–20%), and hydrated lime (0.5–2%) on the stress–strain curve, unconfined uniaxial compressive strength, and elastic modulus (E₅₀) of these materials. The test results indicate that increasing the ground granulated blast furnace slag content can significantly enhance the mechanical properties of phosphogypsum-based cementitious materials. Additionally, increasing the fly ash content can have a similar beneficial effect with an appropriate amount of hydrated lime. Furthermore, microscopic analysis of the cementitious materials using a scanning electron microscope revealed that the high sulfate content in phosphogypsum leads to the formation of calcium aluminate as the main product. Concurrently, a continuous reaction of the raw materials contributes to the strength development of the cementitious materials over time. The results could provide a novel method for improving the reusing phosphogypsum amount in civil engineering materials. Full article

(This article belongs to the Special Issue Effects of Adding Cement Admixtures on the Microstructure and Properties of Cement Materials)

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13 pages, 874 KiB

Open AccessArticle

Electro-Optic Kerr Response in Optically Isotropic Liquid Crystal Phases

by Tetiana Yevchenko, Dorota Dardas, Natalia Bielejewska and Arkadiusz C. Brańka

Materials 2024, 17(19), 4926; https://doi.org/10.3390/ma17194926 - 9 Oct 2024

Viewed by 505

Abstract

The results of an experimental investigation of the temperature and wavelength dependence of the Kerr constant (K) of mixtures with an increasing amount of chiral dopant in an isotropic liquid crystal phase are reported. The material was composed of a nematic [...] Read more.

The results of an experimental investigation of the temperature and wavelength dependence of the Kerr constant (K) of mixtures with an increasing amount of chiral dopant in an isotropic liquid crystal phase are reported. The material was composed of a nematic liquid crystal (5CB) and a chiral dopant (CE2), which formed non-polymer-stabilized liquid crystalline blue phases with an exceptionally large value of K∼2 × 10⁻⁹ mV⁻². The measurements were performed on liquid and blue phases at several concentrations covering a range of temperatures and using three wavelengths: 532 nm, 589 nm and 633 nm. The work focused on changes caused by concentration and their impact on the increase in the value of K, and it was found that in the case of the 5CB/CE2 mixture these changes were significant and quite systematic with temperature and wavelength. It is shown that the dispersion relation based on the single-band birefringence model described K well in isotropic liquid crystal phases at all of the measured concentrations. In an isotropic fluid, both temperature-dependent parameters in the dispersion relation had a simple linear form and, therefore, the K-surface could be described by only four constants. In the blue phase, the expression reproducing the temperature variation of K depended on concentration, which could vary from being almost linear to quasi-linear and could be represented well by an inverse exponential analytic expression. Full article

(This article belongs to the Section Optical and Photonic Materials)

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12 pages, 6301 KiB

Open AccessArticle

High-Temperature Fatigue Degradation Behaviors of a 3D Braided C/SiC with a Thin Interlayer in Different Dry Oxygen Atmospheres

by Lexin Yang, Dianwei He, Chen Hu, Zhenhuan Gao, Liping Nie, Youbei Sun, Lei Zhang and Xingang Luan

Materials 2024, 17(19), 4925; https://doi.org/10.3390/ma17194925 - 9 Oct 2024

Viewed by 524

Abstract

In order to evaluate the increase in the flexural strength of a 3D braided C/SiC composite comprised with a thin pyrolytic carbon (PyC) interlayer (TI C/SiC) under a load of 60 MPa with an amplitude of ±20 MPa at an oxygen partial pressure [...] Read more.

In order to evaluate the increase in the flexural strength of a 3D braided C/SiC composite comprised with a thin pyrolytic carbon (PyC) interlayer (TI C/SiC) under a load of 60 MPa with an amplitude of ±20 MPa at an oxygen partial pressure of 8000 Pa, the effect of temperature, oxidation and stress value on the length change in the sample, fracture behavior, residual flexural strength and fracture morphology were studied up to 1500 °C. It was found that the gauge length change behaviors of the material are related to (i) the positive damage of the thin interlayer and (ii) to the negative damage of the C phase. The most serious damage of TI C/SiC under 60 ± 20 MPa occurs in an oxygen partial pressure of 17,000 Pa at 1300 °C. When the oxygen partial pressure and/or the temperature are reduced, the positive C phase damage is relieved. In the case that the oxygen partial pressure, temperature and stress increase, the negative C phase damage is facilitated. The oxidation mechanism of the C phase is controlled by the inward diffusion of oxygen from the sample surface to the center; however, a higher stress is considered to change the oxygen diffusion mechanism by increasing the reaction of the C phase, with oxygen causing a widening of microcracks. Full article

(This article belongs to the Special Issue Advanced Multifunctional Materials under High Temperature and High Pressure)

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13 pages, 356 KiB

Open AccessReview

Bose Metals, from Prediction to Realization

by M. C. Diamantini and C. A. Trugenberger

Materials 2024, 17(19), 4924; https://doi.org/10.3390/ma17194924 - 9 Oct 2024

Viewed by 453

Abstract

Bose metals are metals made of Cooper pairs, which form at very low temperatures in superconducting films and Josephson junction arrays as an intermediate phase between superconductivity and superinsulation. We predicted the existence of this 2D metallic phase of bosons in the mid [...] Read more.

Bose metals are metals made of Cooper pairs, which form at very low temperatures in superconducting films and Josephson junction arrays as an intermediate phase between superconductivity and superinsulation. We predicted the existence of this 2D metallic phase of bosons in the mid 1990s, showing that they arise due to topological quantum effects. The observation of Bose metals in perfectly regular Josephson junction arrays fully confirms our prediction and rules out alternative models based on disorder. Here, we review the basic mechanism leading to Bose metals. The key points are that the relevant vortices in granular superconductors are core-less, mobile XY vortices which can tunnel through the system due to quantum phase slips, that there is no charge-phase commutation relation preventing such vortices from being simultaneously out of condensate with charges, and that out-of-condensate charges and vortices are subject to topological mutual statistics interactions, a quantum effect that dominates at low temperatures. These repulsive mutual statistics interactions are sufficient to increase the energy of the Cooper pairs and lift them out of condensate. The result is a topological ground state in which charge conduction along edges and vortex movement across them organize themselves so as to generate the observed metallic saturation at low temperatures. This state is known today as a bosonic topological insulator. Full article

(This article belongs to the Special Issue Advanced Materials with Strong Electron Correlations)

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19 pages, 8399 KiB

Open AccessArticle

Effects of Strontium Modification on Corrosion Resistance of Al-Si Alloys in Various Corrosive Environments

by Lau Lin Jie, Mirza Farrukh Baig and Ervina Efzan Mhd Noor

Materials 2024, 17(19), 4923; https://doi.org/10.3390/ma17194923 - 9 Oct 2024

Viewed by 590

Abstract

This study investigates the impact of strontium (Sr) additions on the corrosion resistance of an LM6 (A413) aluminium alloy. By incorporating varying concentrations of Sr (0.01 wt.% and 0.05 wt.%), the morphological and corrosion behaviours of the alloy were analysed under different corrosive [...] Read more.

This study investigates the impact of strontium (Sr) additions on the corrosion resistance of an LM6 (A413) aluminium alloy. By incorporating varying concentrations of Sr (0.01 wt.% and 0.05 wt.%), the morphological and corrosion behaviours of the alloy were analysed under different corrosive environments, including sulphuric acid, sodium hydroxide, and sodium chloride solutions. The results demonstrate that Sr modifications significantly enhance the alloy’s corrosion resistance, with the most substantial improvement observed at 0.05 wt.% Sr. The analysis revealed that the weight loss of the alloy in sulphuric acid decreased by 2.5% with 0.05 wt.% Sr after 10 days of immersion, due to the formation of a stable passive oxide layer. In sodium hydroxide, however, the weight loss was reduced by 5% with 0.05 wt.% Sr after 10 days, indicating aggressive uniform corrosion. In the 3.5% sodium chloride solution, the corrosion rates remain relatively low, and the 0.05 wt.% Sr alloy showed a decrease in corrosion product formation over time, suggesting enhanced resistance. Detailed surface analyses, including 3D profiling and morphology assessments, revealed that Sr additions refine the eutectic silicon phase, transforming it from a coarse to a more desirable fibrous or lamellar structure, thus improving the alloy’s overall performance. The innovative findings underscore the potential of Sr as an effective microstructural modifier for enhancing the durability and longevity of Al-Si alloys in corrosive environments. Full article

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14 pages, 7701 KiB

Open AccessArticle

Compressive Strength and Chloride Ion Penetration Resistance of GGBFS-Based Alkali-Activated Composites Containing Ferronickel Slag Aggregates

by Jae-In Lee, Chae-Young Kim, Joo-Ho Yoon and Se-Jin Choi

Materials 2024, 17(19), 4922; https://doi.org/10.3390/ma17194922 - 9 Oct 2024

Viewed by 615

Abstract

Various studies have reported the use of alkali-activated composites to enable sustainable development in the construction industry as these composites eliminate the need for cement. However, few studies have used ferronickel slag aggregates (FSAs) as an aggregate material for alkali-activated composites. Alkali-activated composites [...] Read more.

Various studies have reported the use of alkali-activated composites to enable sustainable development in the construction industry as these composites eliminate the need for cement. However, few studies have used ferronickel slag aggregates (FSAs) as an aggregate material for alkali-activated composites. Alkali-activated composites are environmentally friendly and sustainable construction materials that can reduce carbon dioxide emissions from cement production, which accounts for 7% of global carbon emissions. In the construction industry, various research was conducted to improve the performance of alkali-activated composites, such as changing the binder, alkali activator, or aggregate. However, research on the application of ferronickel slag aggregate as an aggregate in alkali-activated composites is still insufficient. In addition, the effect of ferronickel slag aggregate on the performance of alkali-activated composites when using calcium-based or sodium-based alkali activators has not been reported yet. Thus, this study prepared ground granulated blast-furnace slag-based alkali-activated composites with 0, 10, 20, and 30% FSA as natural fine aggregate substitutes. Then, the fluidity, micro-hydration heat, compressive strength properties, and resistance to chloride ion penetration of the alkali-activated composite were evaluated. The test results showed that the maximum temperature of the CF10, CF20, and CF30 samples with FSA was 35.4–36.4 °C, which is 3.8–6.7% higher than that of the CF00 sample. The 7 d compressive strength of the sample prepared with CaO was higher than that of the sample prepared with Na₂SiO₃. Nevertheless, the 28 d compressive strength of the NF20 sample with Na₂SiO₃ and 20% FSA was the highest, with a value of approximately 55.0 MPa. After 7 d, the total charge passing through the sample with Na₂SiO₃ was approximately 1.79–2.24 times higher than that of the sample with CaO. Moreover, the total charge decreased with increasing FSA content. Full article

(This article belongs to the Special Issue Convergence & Sustainable Technology in Building Materials (2nd Edition))

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2 pages, 139 KiB

Open AccessRetraction

RETRACTED: Shi et al. Effect of Final Rolling Temperature on Microstructures and Mechanical Properties of AZ31 Alloy Sheets Prepared by Equal Channel Angular Rolling and Continuous Bending. Materials 2020, 13, 3346

by Laixin Shi, Lei Liu, Li Hu, Tao Zhou, Mingbo Yang, Yong Lian and Jin Zhang

Materials 2024, 17(19), 4921; https://doi.org/10.3390/ma17194921 - 9 Oct 2024

Viewed by 493

Abstract

The journal retracts the article, “Effect of Final Rolling Temperature on Microstructures and Mechanical Properties of AZ31 Alloy Sheets Prepared by Equal Channel Angular Rolling and Continuous Bending” [...] Full article

17 pages, 5528 KiB

Open AccessArticle

Effect of Pouring Techniques and Funnel Structures on Crucible Metallurgy: Physical and Numerical Simulations

by Wenwen Feng, Wenkang Yao, Lin Yuan, Ye Yuan, Yiming Li, Pu Wang and Jiaquan Zhang

Materials 2024, 17(19), 4920; https://doi.org/10.3390/ma17194920 - 8 Oct 2024

Viewed by 530

Abstract

In the planar flow casting process of amorphous strips, the flow behavior of molten metal and the inclusion content in the crucible are crucial to the morphology and magnetic properties of the material. This study conducts a comparative analysis of the effects of [...] Read more.

In the planar flow casting process of amorphous strips, the flow behavior of molten metal and the inclusion content in the crucible are crucial to the morphology and magnetic properties of the material. This study conducts a comparative analysis of the effects of non-immersed and immersed funnels, as well as various funnel structures, on the fluid flow and inclusion removal efficiency in the crucible by integrating numerical and physical models. The findings reveal that for the same pouring flow rate, the diameter of the liquid column in non-immersed pouring conditions is smaller than that of the funnel outlet, leading to a faster injection flow velocity. As a result, the melt in the crucible is subjected to severe impacts, accompanied by an increased possibility of slag entrapment. Conversely, immersed pouring substantially reduces the velocity of the molten metal at the funnel outlet, thereby extending the residence time in the crucible and diminishing the volume of the dead zone. Additionally, the molten metal backflows due to the negative pressure formed in the inner chamber of the funnel. The design of a trumpet-shaped funnel increases the effective volume while reducing the height of the backflow fluid, consequently reducing the velocity of the molten metal at the funnel outlet and prolonging the residence time. Compared to the conventional pouring process with the non-immersed funnel, the outlet velocity is reduced from 1.1 m/s to 0.12 m/s by adopting the immersed funnel with an inverted trapezoidal trumpet structure. This reduction results in a stable flow state, a 9.69% reduction in the dead zone volume fraction, and a 22.96% increase in average inclusion removal efficiency. These improvements demonstrate that a crucible funnel with a well-designed structure and the implementation of an immersion process can significantly improve the metallurgical effects in the planar flow casting process. Full article

(This article belongs to the Special Issue Advanced Metallurgy Technologies: Physical and Numerical Modelling)

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15 pages, 483 KiB

Open AccessArticle

Integrating Flow Field Dynamics and Chemical Atmosphere Predictions for Enhanced Sulfur Corrosion Risk Assessment in Power Boilers

by Dariusz Kardaś, Sylwia Polesek-Karczewska and Izabela Wardach-Świȩcicka

Materials 2024, 17(19), 4919; https://doi.org/10.3390/ma17194919 - 8 Oct 2024

Viewed by 633

Abstract

In this work, we attempt to explain the phenomenon of sulfur corrosion of power boiler water walls under the conditions of large fluctuations in carbon monoxide concentrations. To assess the conditions required for corrosion formation, a criterion based on the chemical and flow [...] Read more.

In this work, we attempt to explain the phenomenon of sulfur corrosion of power boiler water walls under the conditions of large fluctuations in carbon monoxide concentrations. To assess the conditions required for corrosion formation, a criterion based on the chemical and flow field parameters of the flue gas is proposed. The formulated sulfur corrosion criterion is based on the mixture fraction variance and the turbulence time scale. Numerical modeling of coal combustion in a 250 MW power boiler is performed using ANSYS. Two cases of combustion in a boiler are analyzed, with the first simulating the boiler operated using classic high-swirl burners and the second one accounting for boiler operation with modified low-swirl burners. Calculations of pulverized coal combustion are performed using the standard k-

ε

turbulence model and the combustion described by the mixture fraction. The simulation results reveal that the low-swirl burner is characterized by higher values of the mixture fraction variance and a higher frequency of fluctuation of the velocity field, which is strongly related to an increased corrosion rate. The study outcomes show the validity of using the criterion of the mixture fraction variance and velocity field fluctuations to determine the areas at risk of sulfur corrosion. Full article

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18 pages, 8433 KiB

Open AccessArticle

Towards More Sustainable Schiff Base Carboxylate Anodes for Sodium-Ion Batteries

by Irene Gómez-Berenguer, Bernardo Herradón, José Manuel Amarilla and Elizabeth Castillo-Martínez

Materials 2024, 17(19), 4918; https://doi.org/10.3390/ma17194918 - 8 Oct 2024

Viewed by 613

Abstract

Bismine sodium salt (BSNa), a Schiff base with two sodium carboxylates, has shown promising electrochemical performance as an anode material. However, its synthesis involves toxic reagents and generates impurities, requiring significant solvent use for purification. This study introduces a novel synthetic method using [...] Read more.

Bismine sodium salt (BSNa), a Schiff base with two sodium carboxylates, has shown promising electrochemical performance as an anode material. However, its synthesis involves toxic reagents and generates impurities, requiring significant solvent use for purification. This study introduces a novel synthetic method using sodium hydroxide as the sole reagent, which acts as both a base and Na source in the ion exchange step. With this procedure, we reduce the amounts of chemicals, diminish toxicity, improve the purity of the target compound, and use less solvent while maintaining comparable electrochemical performance. Additionally, the procedure is carried out under anhydrous conditions that avoid the undesirable hydrolysis of the imine linkages. In a previous report, the processing of the composite electrode was not established. In this article, we address this issue; the electrochemical performance, specifically the rate capability, is enhanced by processing the electrodes in laminate form rather than powder. As alternative to N-methyl-2-pyrrolidone (NMP), a common but disadvantageous solvent in laminate processing, other solvents were explored by testing acetone (DMK), methylisopropylketone (MIPK), and a DMK-NMP mixture. The remarkable electrochemical performance (specific capacity of 260–280 mAh/g, and capacity retentions higher than 84% at 1C (260 mA/g) remained consistent across these solvents. Furthermore, we investigated replacing copper with aluminum as the current collector to reduce costs and increase the energy density of the battery. While aluminum performed comparably to copper at low specific currents C/10 (26 mA/g), it showed a significant shift in the redox process potentials at higher specific currents. Full article

(This article belongs to the Special Issue Advanced Anode Materials for Alkali-Ion Batteries)

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19 pages, 5829 KiB

Open AccessArticle

Mechanical Properties of Full-Scale Wooden Beams Strengthened with Carbon-Fibre-Reinforced Polymer Sheets

by Michał Marcin Bakalarz

Materials 2024, 17(19), 4917; https://doi.org/10.3390/ma17194917 - 8 Oct 2024

Viewed by 631

Abstract

The strengthening, rehabilitation and repair of wooden beams and beams made of wood-based materials are still important scientific and technical issues. This is reflected, among other things, in the number of scientific articles appearing and the involvement of research centres around the world. [...] Read more.

The strengthening, rehabilitation and repair of wooden beams and beams made of wood-based materials are still important scientific and technical issues. This is reflected, among other things, in the number of scientific articles appearing and the involvement of research centres around the world. This is also related to society’s growing belief in the importance of ecological and sustainable development. This article presents an overview of the latest work in this field and the results of our own research on strengthening solid wooden beams with carbon-fibre-reinforced polymer (CFRP) sheets. The tests were carried out on full-size solid beams with nominal dimensions of 70 × 170 × 3300 mm. A 0.333 mm thick CFRP sheet was used for reinforcement. The research analysed various reinforcement configurations and different reinforcement ratios. For the most effective solution, a 46% increase in load capacity, 35% stiffness and 249% ductility were achieved with a reinforcement ratio of 1.7%. Generally, the higher the reinforcement ratio and coverage of the surface of the wood, the higher the strengthening effectiveness. The brittle fracture of wood in the tensile zone for unreinforced beams and the ductile crushing of wood in the compressive zone for reinforced beams were obtained. The most important achievement of this work is the description of the static work of beams in previously unanalysed configurations of strengthening and the confirmation of their effectiveness. The described solutions should extend the life of existing wooden buildings and structures and increase the competitiveness of wooden-based structures. The results indicate that, from the point of view of optimizing the cost of reinforcement, it is crucial to develop cheaper ways of combining wood and composite than to verify different types of fibres. Full article

(This article belongs to the Section Construction and Building Materials)

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15 pages, 2513 KiB

Open AccessArticle

In Vitro Investigation Using a New Biomechanical Force–Torque Analysis System: Comparison of Conventional and CAD/CAM-Fixed Orthodontic Retainers

by Francesca Thaden, Linus Hötzel, Hisham Sabbagh, Matthias Mertmann and Andrea Wichelhaus

Materials 2024, 17(19), 4916; https://doi.org/10.3390/ma17194916 - 8 Oct 2024

Viewed by 620

Abstract

(1) Background: After more than a decade since their first description, Inadvertent Tooth Movements (ITMs) remain an adverse effect of orthodontic retainers without a clear etiology. To further investigate the link between ITMs and the mechanical properties of different retainers, the response upon [...] Read more.

(1) Background: After more than a decade since their first description, Inadvertent Tooth Movements (ITMs) remain an adverse effect of orthodontic retainers without a clear etiology. To further investigate the link between ITMs and the mechanical properties of different retainers, the response upon vertical loading was compared in three retainer types (two stainless steel and one nickel–titanium). The influence of different reference teeth was also considered. (2) Methods: Three retainers (R1, R2, R3) were tested in a newly developed biomechanical analysis system (FRANS). They were bonded to 3D-printed models of the lower anterior jaw and vertically displaced up to 0.3 mm. Developing forces and moments were recorded at the center of force. (3) Results: The vertical displacement caused vertical forces (Fz) and labiolingual moments (My) to arise. These were highest in the lateral incisors (up to 2.35 ± 0.59 N and 9.27 ± 5.86 Nmm for R1; 1.69 ± 1.06 N and 7.42 ± 2.65 Nmm for R2; 3.28 ± 1.73 N and 15.91 ± 9.71 Nmm for R3) for all analyzed retainers and with the R3 retainer for all analyzed reference teeth, while the lowest Fz and My values were recorded with the R1 retainer. (4) Conclusions: Displacements of 0.2 mm and larger provided forces and moments which could be sufficient to cause unwanted torque movements, such as ITMs, in all analyzed retainers. Clinicians must be mindful of these risks and perform post-treatment checkups on patients with retainers of all materials. Full article

(This article belongs to the Special Issue Orthodontic Materials: Properties and Effectiveness of Use)

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17 pages, 4104 KiB

Open AccessArticle

Using the Ethaline Electropolishing Method on the Internal Surface of Additive Manufactured Tubes

by Dongyi Zou, Chaojiang Li, Yuxin Yang, Xin Jin, Shenggui Liu, Hongyi Zhang and Na Zhang

Materials 2024, 17(19), 4915; https://doi.org/10.3390/ma17194915 - 8 Oct 2024

Viewed by 635

Abstract

Electropolishing is a widely used technique for polishing additive manufactured (AM) components, while complex internal surface polishing remains a challenge. In this study, we explore the use of ethaline as an electrolyte and investigate the effects of temperature, time, stirring speed, and voltage [...] Read more.

Electropolishing is a widely used technique for polishing additive manufactured (AM) components, while complex internal surface polishing remains a challenge. In this study, we explore the use of ethaline as an electrolyte and investigate the effects of temperature, time, stirring speed, and voltage on the electropolishing effectiveness for AM tubes without pre-treatment through orthogonal experiments. The optimal combination of these factors is then applied in further electropolishing experiments on straight tubes with large length-to-diameter ratios and an angled tube. Our results indicate that temperature has the most significant impact on internal surface electropolishing performance, and other factors’ effects are also analyzed. Ethaline can be a promising electrolyte for internal surface electropolishing of AM components because of its high viscosity, which is validated by flow field simulation of the hydrodynamic conditions inside the tubes. Full article

(This article belongs to the Topic Advanced Manufacturing and Surface Technology)

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15 pages, 4643 KiB

Open AccessArticle

Composites Based on Electrodeposited WO₃ and TiO₂ Nanoparticles for Photoelectrochemical Water Splitting

by Ramunas Levinas, Elizabeth Podlaha, Natalia Tsyntsaru and Henrikas Cesiulis

Materials 2024, 17(19), 4914; https://doi.org/10.3390/ma17194914 - 8 Oct 2024

Viewed by 678

Abstract

Photoelectrochemically active WO₃ films were fabricated by electrodeposition from an acidic (pH 2), hydrogen-peroxide-containing electrolyte at −0.5 V vs. SCE. WO₃-TiO₂ composites were then synthesized under the same conditions, but with 0.2 g/L of anatase TiO₂ nanoparticles (⌀ [...] Read more.

Photoelectrochemically active WO₃ films were fabricated by electrodeposition from an acidic (pH 2), hydrogen-peroxide-containing electrolyte at −0.5 V vs. SCE. WO₃-TiO₂ composites were then synthesized under the same conditions, but with 0.2 g/L of anatase TiO₂ nanoparticles (⌀ 36 nm), mechanically suspended in the solution by stirring. After synthesis, the films were annealed at 400 °C. Structural characterization by XRD showed that the WO₃ films exhibit the crystalline structure of a non-stoichiometric hydrate, whereas, in WO₃-TiO₂, the WO₃ phase was monoclinic. The oxidation of tungsten, as revealed by XPS, was W⁶⁺ for both materials. Ti was found to exist mainly as Ti⁴⁺ in the composite, with a weak Ti³⁺ signal. The efficiency of the WO₃ films and composites as an oxygen evolution reaction (OER) photo-electrocatalyst was examined. The composite would generate approximately three times larger steady-state photocurrents at 1.2 V vs. SCE in a neutral 0.5 M Na₂SO₄ electrolyte compared to WO₃ alone. The surface recombination of photogenerated electron–hole pairs was characterized by intensity-modulated photocurrent spectroscopy (IMPS). Photogenerated charge transfer efficiencies were calculated from the spectra, and at 1.2 V vs. SCE, were 86.6% for WO₃ and 62% for WO₃-TiO₂. Therefore, the composite films suffered from relatively more surface recombination but generated larger photocurrents, which resulted in overall improved photoactivity. Full article

(This article belongs to the Special Issue Electrochemical Material Science and Electrode Processes)

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10 pages, 2712 KiB

Open AccessArticle

Influence of Conductive Filler Types on the Ratio of Reflection and Absorption Properties in Cement-Based EMI Shielding Composites

by Daeik Jang, Jihoon Park, Woosuk Jang, Jinho Bang, G. M. Kim, Jaesuk Choi, Joonho Seo and Beomjoo Yang

Materials 2024, 17(19), 4913; https://doi.org/10.3390/ma17194913 - 8 Oct 2024

Viewed by 558

Abstract

The growing importance of electromagnetic interference (EMI) shielding composites in civil engineering has garnered increasing attention. Conductive cement-based composites, incorporating various conductive fillers, such as carbon nanotubes (CNTs), carbon fibers (CFs), and graphene nanoplatelets (GNPs), provide effective solutions due to their high electrical [...] Read more.

The growing importance of electromagnetic interference (EMI) shielding composites in civil engineering has garnered increasing attention. Conductive cement-based composites, incorporating various conductive fillers, such as carbon nanotubes (CNTs), carbon fibers (CFs), and graphene nanoplatelets (GNPs), provide effective solutions due to their high electrical conductivity. While previous studies have primarily focused on improving the overall shielding effectiveness, this research emphasizes balancing the reflection and absorption properties. The experimental results demonstrate an EMI shielding performance exceeding 50 dB, revealing that filler size (nano, micro, or macro) and shape (platelet or fiber) significantly influence both reflection and absorption characteristics. Based on a comprehensive evaluation of the shielding properties, this study highlights the need to consider factors such as reflection versus absorption losses and filler shape or type when optimizing filler content to develop effective cement-based EMI shielding composites. Full article

(This article belongs to the Special Issue Low-Carbon Construction and Building Materials)

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17 pages, 4501 KiB

Open AccessArticle

Preparation and Characterization of Novel Poly(Lactic Acid) Composites Reinforced with “Latxa” Sheep Wool Fibers: The Effect of Peroxide Surface Treatments and Fiber Content

by Aitor Arbelaiz, Telmo Yurramendi, Ander Larruscain, Ane Arrizabalaga, Arantxa Eceiza and Cristina Peña-Rodriguez

Materials 2024, 17(19), 4912; https://doi.org/10.3390/ma17194912 - 8 Oct 2024

Viewed by 775

Abstract

“Latxa” sheep wool is rough, and it is not used in the textile industry because the fiber diameter is high compared with other wool fibers. Nowadays, this wool is considered as disposal and, with the aim to give it value, new uses must [...] Read more.

“Latxa” sheep wool is rough, and it is not used in the textile industry because the fiber diameter is high compared with other wool fibers. Nowadays, this wool is considered as disposal and, with the aim to give it value, new uses must be explored. In the current work, the “Latxa” sheep wool fiber was evaluated as poly(lactic acid) (PLA) polymer reinforcement. With the objective to optimize fiber/matrix adhesion, fibers were surface modified with peroxide. Oxidation treatment with peroxide led to chemical modifications of the wool fibers that improved the fiber/PLA adhesion, but the strength values achieved for the composites were lower compared to the neat PLA ones. The mechanical properties obtained in the current work were compared with the literature data of the PLA composites reinforced with vegetable fibers. The wool fibers showed inferior mechanical properties compared to the vegetable fiber counterparts. However, the preliminary results indicated that the incorporation of wool fibers to PLA reduced the flammability of composites. Full article

(This article belongs to the Section Advanced Composites)

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14 pages, 9262 KiB

Open AccessArticle

Innovative Hemp Shive-Based Bio-Composites: Part I: Modification of Potato Starch Binder by Sodium Meta-Silicate and Glycerol

by Laura Vitola, Ina Pundiene, Jolanta Pranckeviciene and Diana Bajare

Materials 2024, 17(19), 4911; https://doi.org/10.3390/ma17194911 - 8 Oct 2024

Viewed by 613

Abstract

The growing demand for sustainable building materials has boosted research on plant-based composite materials, including hemp shives bound with biodegradable binders. This study investigates the enhancement of potato-starch-based binders with sodium metasilicate and glycerol to produce eco-friendly bio-composites incorporating hemp shives. Potato starch, [...] Read more.

The growing demand for sustainable building materials has boosted research on plant-based composite materials, including hemp shives bound with biodegradable binders. This study investigates the enhancement of potato-starch-based binders with sodium metasilicate and glycerol to produce eco-friendly bio-composites incorporating hemp shives. Potato starch, while renewable, often results in suboptimal mechanical properties and durability in its unmodified form. The addition of sodium metasilicate is known to improve the mechanical strength and thermal stability of starch-based materials, while glycerol acts as a plasticizer, potentially enhancing flexibility and workability. Bio-composites were produced with varying concentrations of sodium metasilicate (0–107% by mass of starch) and glycerol (0–133% by mass of starch), and their properties were evaluated through thermal analysis, density measurements, water absorption tests, compressive strength assessments, and thermal conductivity evaluations. The results demonstrate that sodium metasilicate significantly increases the bulk density, water resistance, and compressive strength of the bio-composites, with enhancements up to 19.3% in density and up to 2.3 times in compressive strength. Glycerol further improves flexibility and workability, though excessive amounts can reduce compressive strength. The combination of sodium metasilicate and glycerol provides optimal performance, achieving the best results with an 80% sodium metasilicate and 33% glycerol mixture by weight of starch. These modified bio-composites offer promising alternatives t2 o conventional building materials with improved mechanical properties and environmental benefits, making them suitable for sustainable construction applications. Full article

(This article belongs to the Section Construction and Building Materials)

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