Materials

16 pages, 8254 KiB

Open AccessArticle

An Experimental Study on the Thermal Performance of a Heat Sink Filled with Porous Aluminum Skeleton/Paraffin Composite Phase Change Material

by Shufeng Huang, Zhihan Hu, Zhixin Chen, Dayong Yang, Weili Huang and Bin Zhang

Materials 2024, 17(17), 4332; https://doi.org/10.3390/ma17174332 (registering DOI) - 31 Aug 2024

Abstract

Organic phase change material is an ideal solution to solve the heat dissipation problem of electronic devices. However, its low thermal conductivity limits its application. To solve this problem, a new porous aluminum skeleton/paraffin composite phase change material (AS-PCM) was prepared. The effects [...] Read more.

Organic phase change material is an ideal solution to solve the heat dissipation problem of electronic devices. However, its low thermal conductivity limits its application. To solve this problem, a new porous aluminum skeleton/paraffin composite phase change material (AS-PCM) was prepared. The effects of porosity and porous aluminum skeletons on temperature control performance were explored. The experimental results show that the addition of AS significantly improves the thermal conductivity of organic PCM, and the thermal conductivity of AS-PCM is 32.3–59.6 times higher than that of pure paraffin. In addition, the temperature difference in AS-PCM with 75% porosity is 1–2 °C lower than that of AS-PCM with 85%, and 5–8 °C lower than that of AS-PCM with 95% porosity. The skeleton structure has an impact on the temperature control performance. The Mcc porous aluminum skeleton/paraffin composite phase change material (MAS-PCM) yields the best thermal performance compared with the Fcc porous aluminum skeleton/paraffin composite phase change material (FAS-PCM). The temperature control time of the MAS-PCM heat sink is increased by 5.3–50.8% relative to the FAS-PCM heat sink. The research results provide a novel approach for improving the thermal conductivity of PCMs. Full article

(This article belongs to the Section Energy Materials)

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13 pages, 2817 KiB

Open AccessArticle

Structure–Elasticity Relationships in Hybrid-Carrageenan Hydrogels Studied by Image Dynamic Light Scattering, Ultra-Small-Angle Light Scattering and Dynamic Rheometry

by Amine Ben Yahia, Adel Aschi, Bruno Faria and Loic Hilliou

Materials 2024, 17(17), 4331; https://doi.org/10.3390/ma17174331 (registering DOI) - 31 Aug 2024

Abstract

Hybrid-carrageenan hydrogels are characterized using novel techniques based on high-resolution speckle imaging, namely image dynamic light scattering (IDLS) and ultra-small-angle light scattering (USALS). These techniques, used to probe the microscopic structure of the system in sol–gel phase separation and at different concentrations in [...] Read more.

Hybrid-carrageenan hydrogels are characterized using novel techniques based on high-resolution speckle imaging, namely image dynamic light scattering (IDLS) and ultra-small-angle light scattering (USALS). These techniques, used to probe the microscopic structure of the system in sol–gel phase separation and at different concentrations in the gel phase, give access to a better understanding of the network’s topology on the basis of fractals in the dense phase. Observations of the architecture and the spatial and the size distributions of gel phase and fractal dimension were performed by USALS. The pair-distance distribution function, P(r), extracted from USALS patterns, is a new methodology of calculus for determining the network’s internal size with precision. All structural features are systematically compared with a linear and non-linear rheological characterization of the gels and structure–elasticity relationships are identified in the framework of fractal colloid gels in the diffusion limit. Full article

(This article belongs to the Special Issue Modification and Processing of Biodegradable Polymers (Volume II))

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18 pages, 12682 KiB

Open AccessArticle

Damage and Recovery Behavior of Low-Replacement-Rate Fly Ash Concrete after Different High-Temperature Exposures

by Lin Mi, Bowen Kuang, Daixin Fu, Lang Li, Yongjie Liu, Chong Wang, Chao He, Yao Chen, Hong Zhang, Fulin Liu and Qingyuan Wang

Materials 2024, 17(17), 4330; https://doi.org/10.3390/ma17174330 (registering DOI) - 31 Aug 2024

Abstract

This study focuses on investigating the strength recovery of fire-damaged fly ash concrete (FAC) with a low substitution rate of 10% through post-fire curing. The chemical and microstructural changes were analyzed using X-ray diffraction (XRD), derivative thermogravimetry (DTG), scanning electron microscopy (SEM), energy [...] Read more.

This study focuses on investigating the strength recovery of fire-damaged fly ash concrete (FAC) with a low substitution rate of 10% through post-fire curing. The chemical and microstructural changes were analyzed using X-ray diffraction (XRD), derivative thermogravimetry (DTG), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and nitrogen adsorption. The findings indicate that the incorporation of fly ash slightly enhanced the strength after exposure to 400 °C; this was attributed to improved pozzolanic reactions, which were not observed at higher temperatures of 600 °C and 800 °C. Moreover, a positive effect on the recovery of compressive strength was observed due to the pozzolanic reaction. However, due to the relatively low fly ash content, depletion occurred at a later age, resulting in the inability to inhibit microstructural damage caused by the production of portlandite, thereby weakening the compressive strength. Interestingly, fly ash influenced the morphology of calcium carbonate and calcium silicate hydrate crystals, which is potentially ascribed to the role of high aluminum content acting as a crystallization-guiding agent. Full article

(This article belongs to the Special Issue Green and Sustainable Infrastructure Construction Materials (2nd Edition))

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18 pages, 7058 KiB

Open AccessArticle

Adsorption Properties and Mechanisms of Methylene Blue by Modified Sphagnum Moss Bio-Based Adsorbents

by Junpeng Ren, Shijiang Zhang, Yu Wang and Hengxiu Yang

Materials 2024, 17(17), 4329; https://doi.org/10.3390/ma17174329 (registering DOI) - 31 Aug 2024

Abstract

The abundant pore structure and carbon composition of sphagnum peat moss render it a bio-based adsorbent for efficient methylene blue removal from wastewater. By utilizing sphagnum moss sourced from Guizhou, China, as raw material, a cost-effective and highly efficient bio-based adsorbent material was [...] Read more.

The abundant pore structure and carbon composition of sphagnum peat moss render it a bio-based adsorbent for efficient methylene blue removal from wastewater. By utilizing sphagnum moss sourced from Guizhou, China, as raw material, a cost-effective and highly efficient bio-based adsorbent material was prepared through chemical modification. The structure and performance of the modified sphagnum moss were characterized using SEM, EDS, FTIR, and TGA techniques. Batch adsorption experiments explored the effects of contact time, adsorbent dosage, pH, initial dye concentration, and temperature on adsorption performance. Kinetics, isotherm models, and thermodynamics elucidated the adsorption behavior and mechanism. The modified sphagnum moss exhibited increased surface roughness and uniform surface modification, enhancing active site availability for improved adsorption. Experimental data aligned well with the Freundlich isotherm model and pseudo-second-order kinetic model, indicating efficient adsorption. The study elucidated the adsorption mechanism, laying a foundation for effective methylene blue removal. The utilization of modified sphagnum moss demonstrates significant potential in effectively removing MB from contaminated solutions due to its robust adsorption capability and efficient reusability. Full article

(This article belongs to the Topic Porous Materials for Energy and Environment Applications)

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22 pages, 15310 KiB

Open AccessArticle

Effect of Deposition Parameters on Micromechanical Properties and Machining Performance of CrN Coating for Wet Finish Turning of Ti6Al4V Alloy

by Mohammad Shariful Islam Chowdhury, Bipasha Bose, Shahana Akter and Stephen Clarence Veldhuis

Materials 2024, 17(17), 4328; https://doi.org/10.3390/ma17174328 (registering DOI) - 31 Aug 2024

Abstract

This study aims to optimize the performance of CrN coatings deposited on WC cutting tools for machining Ti6Al4V alloy, where the formation of built-up edge (BUE) is a prevalent and critical issue. In-house CrN coatings were developed using the PVD (Physical Vapor Deposition) [...] Read more.

This study aims to optimize the performance of CrN coatings deposited on WC cutting tools for machining Ti6Al4V alloy, where the formation of built-up edge (BUE) is a prevalent and critical issue. In-house CrN coatings were developed using the PVD (Physical Vapor Deposition) process, with variations in deposition parameters including nitrogen gas pressure, bias voltage, and coating thickness. A comprehensive experimental approach encompassing deposition, characterization, and machining performance evaluation was employed to identify the optimal deposition conditions. The results indicated that CrN coatings deposited at a nitrogen gas pressure of 4 Pa, a bias voltage of −50 V, and a thickness of 1.81 µm exhibited superior performance, significantly reducing BUE formation and tool wear. These optimized coatings demonstrated enhanced properties, such as a higher elastic modulus and a lower coefficient of friction, which contributed to improved tool life and machining performance. Comparative studies with commercial CrN coatings revealed that the in-house developed coatings outperformed the commercial variants by approximately 65% in tool life, owing to their superior mechanical properties and reduced friction. This research highlights the potential of tailored CrN coatings for advanced machining applications and emphasizes the importance of optimizing deposition parameters to achieve high-performance tool coatings. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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20 pages, 9495 KiB

Open AccessArticle

Towards a Direct Consideration of Microstructure Deformation during Dynamic Recrystallisation Simulations with the Use of Coupled Random Cellular Automata—Finite Element Model

by Kacper Pawlikowski, Mateusz Sitko, Konrad Perzyński and Łukasz Madej

Materials 2024, 17(17), 4327; https://doi.org/10.3390/ma17174327 (registering DOI) - 31 Aug 2024

Abstract

Dynamic recrystallisation (DRX) is one of the fundamental phenomena in materials science, significantly impacting the microstructure and mechanical properties of components subjected to large plastic deformations. Experimental research on that topic carried out for a wide range of new metallic materials is often [...] Read more.

Dynamic recrystallisation (DRX) is one of the fundamental phenomena in materials science, significantly impacting the microstructure and mechanical properties of components subjected to large plastic deformations. Experimental research on that topic carried out for a wide range of new metallic materials is often supported by computational materials science. A direct consideration and detailed understanding of this phenomenon are possible with a class of full-field numerical models based on the cellular automata (CA) method. However, the classical CA approach is based on a regular, fixed computational space and has limitations in capturing large deformations of the computational domain. Therefore, the main goal of the work is to develop and implement an alternative solution to overcome this limitation. The proposed solution is based on coupling the finite element (FE) method with the random cellular automata (RCA) approach. Such a model can directly consider the influence of geometrical changes in microstructure during large plastic deformation on recrystallisation progress. Details of the developed RCA DRX model assumptions and coupling issues with FE mesh are discussed. Particular attention is also paid to increasing model efficiency and robustness studies. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

18 pages, 4055 KiB

Open AccessArticle

Development of a Novel Adsorbent Derived from Olive Mill Solid Wastes for Enhanced Removal of Methylene Blue

by Malak Hamieh, Nabil Tabaja, Sami Tlais, Bachar Koubaissy, Mohammad Hammoud, Khaled Chawraba, Tayssir Hamieh and Joumana Toufaily

Materials 2024, 17(17), 4326; https://doi.org/10.3390/ma17174326 (registering DOI) - 31 Aug 2024

Abstract

Industrial wastewater discharge, tainted with hazardous substances, including dyes like methylene blue (MB) from the textile sector, further emphasizes the need for water treatment to produce safe drinking water. This study explores the potential of olive mill solid waste, an abundant and cost-effective [...] Read more.

Industrial wastewater discharge, tainted with hazardous substances, including dyes like methylene blue (MB) from the textile sector, further emphasizes the need for water treatment to produce safe drinking water. This study explores the potential of olive mill solid waste, an abundant and cost-effective agricultural waste in Mediterranean regions, to yield high-quality activated carbon (AC) with zinc chloride activation for MB adsorption. The activation process, carried out at a modest temperature of 500 °C without the need for an inert atmosphere, resulted in AC with remarkable characteristics, boasting a substantial surface area of 1184 cm²·g⁻¹ and a total pore volume of 0.824 cm³·g⁻¹. Extensive characterization of the AC was carried out through a large range of surface techniques. The pH of the solution had minimal influence on MB adsorption, the maximum removal was 95%, which was under slightly acidic pH conditions (5.8), and the adsorbent dose was 0.4 g·L⁻¹ for a 50 mg·L⁻¹ MB concentration. Equilibrium data pertaining to MB adsorption were subjected to fitting with different models, namely Langmuir, Freundlich, and Temkin. Notably, the Langmuir model exhibited the best fit, revealing a maximum monolayer adsorption capacity of 500 mg·g⁻¹ at 25 °C, and the adsorption kinetics closely followed a pseudo-second-order model. Full article

(This article belongs to the Special Issue Advanced Nanoporous and Mesoporous Materials)

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14 pages, 14045 KiB

Open AccessArticle

A Template Method Leads to Precisely Synthesize SiO₂@Fe₃O₄ Nanoparticles at the Hundred-Nanometer Scale

by Jinying Zhang, Xinye Wang, Jiaxing Yang and Yexiaotong Zhang

Materials 2024, 17(17), 4325; https://doi.org/10.3390/ma17174325 (registering DOI) - 31 Aug 2024

Abstract

Constructing photonic crystals with core-shell structured nanoparticles is an important means for applications such as secure communication, anti-counterfeiting marking, and structural color camouflage. Nonetheless, the precise synthesis technology for core-shell structured nanoparticles at the hundred-nanometer scale faces significant challenges. This paper proposes a [...] Read more.

Constructing photonic crystals with core-shell structured nanoparticles is an important means for applications such as secure communication, anti-counterfeiting marking, and structural color camouflage. Nonetheless, the precise synthesis technology for core-shell structured nanoparticles at the hundred-nanometer scale faces significant challenges. This paper proposes a controlled synthesis method for core-shell structured nanoparticles using a template method. By using 100 nm diameter silica nanospheres as templates and coating them with a ferroferric oxide shell layer, SiO₂@Fe₃O₄ core-shell structured nanoparticles with regular morphology and good uniformity can be obtained. The study experimentally investigated the effects of feed amount, modifiers, temperature, and feed order on the coating effect, systematically optimizing the preparation process. Centrifugal driving technology was used to achieve structural colors in the visible wavelength range. Additionally, the method successfully created well-defined and uniform core-shell structured nanoparticles using 200 nm diameter silica nanospheres as templates, demonstrating that this controllable synthesis method can effectively produce core-shell structured nanoparticles over a wide range of particle sizes. The template method proposed in this paper can significantly improve morphological regularity and size uniformity while effectively reducing the preparation cost of core-shell structured nanoparticles. Full article

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26 pages, 13887 KiB

Open AccessArticle

Multi-Objective Optimization and Mechanical Properties Analysis of Steel–PVA Hybrid Fiber-Reinforced Cementitious Composites

by Rui Wang and Pinle Zhang

Materials 2024, 17(17), 4324; https://doi.org/10.3390/ma17174324 (registering DOI) - 31 Aug 2024

Abstract

When steel fiber and PVA fiber produced in China and PVA fiber made in Japan are prepared according to the appropriate proportions, the mechanical properties of hybrid fiber-reinforced cementitious composites (HFRCC) are better, which is beneficial to cost control and has wide application [...] Read more.

When steel fiber and PVA fiber produced in China and PVA fiber made in Japan are prepared according to the appropriate proportions, the mechanical properties of hybrid fiber-reinforced cementitious composites (HFRCC) are better, which is beneficial to cost control and has wide application prospects. The effects of the volume content of steel fibers and the volume substitution rate of PVA fibers on the tensile strength, compressive strength, and flexural strength of HFRCC were analyzed using the factor optimization method and principal component analysis (PCA). Through the principal component analysis of HFRCC, a mathematical model for comprehensive performance evaluation was established, and a multi-objective optimization was carried out. The results show that compared with the matrix, the tensile strength, compressive strength, and flexural strength of concrete increase significantly when the volume content of steel fibers is 0.2–0.4% and the volume substitution rate of domestically produced PVA fibers in China or PVA fibers produced in Japan is 50–100%. The maximum cost reduction is 88.25%, and the strength index of HFRCC can reach the optimum; the weights of each factor on the performance of HFRCC were obtained through mathematical statistics. Combined with a variable correlation analysis, these indicators should be noted when optimizing the performance of HFRCC. The research results can provide a basis for the preparation of HFRCC. Full article

(This article belongs to the Section Mechanics of Materials)

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20 pages, 3750 KiB

Open AccessArticle

Assessing the Potential of Rare Earth Elements in Bottom Ash from Coal Combustion in Poland

by Zdzisław Adamczyk, Joanna Komorek, Barbara Białecka and Jacek Nowak

Materials 2024, 17(17), 4323; https://doi.org/10.3390/ma17174323 (registering DOI) - 31 Aug 2024

Abstract

The aim of the research was to assess the potential of bottom ash from Polish coal-fired power plants as an alternative source of rare earth elements (REY). The potential of these ashes was compared with fly ash from the same coal combustion cycle. [...] Read more.

The aim of the research was to assess the potential of bottom ash from Polish coal-fired power plants as an alternative source of rare earth elements (REY). The potential of these ashes was compared with fly ash from the same coal combustion cycle. The phase and chemical composition, as well as REY, were determined using: X-ray diffraction and inductively coupled plasma mass spectrometry. The tested ashes were classified as inert-low pozzolanic and inert-medium pozzolanic, as well as sialic and ferrosialic, with enrichment in detrital material. The phase and chemical composition of bottom ash was similar to fly ash from the same fuel combustion cycle. The REY content in the ash was 199–286 ppm and was lower than the average for global deposits, and the threshold value was considered profitable for recovery from coal. Bottom ash’s importance as a potential source of REY will increase by recovering these metals from separated amorphous glass and mullite and grains rich in Al, Mg, K, and P. The industrial value of bottom ash as an alternative source of REY was similar to fly ash from the same fuel combustion cycle. Full article

(This article belongs to the Special Issue Current and Future Trends in Mineral Processing and Extractive Metallurgy)

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12 pages, 23755 KiB

Open AccessArticle

Estimation of the Structure of Hydrophobic Surfaces Using the Cassie–Baxter Equation

by Oleksiy Myronyuk, Egidijus Vanagas, Aleksej M. Rodin and Miroslaw Wesolowski

Materials 2024, 17(17), 4322; https://doi.org/10.3390/ma17174322 (registering DOI) - 31 Aug 2024

Abstract

The effect of extreme water repellency, called the lotus effect, is caused by the formation of a Cassie–Baxter state in which only a small portion of the wetting liquid droplet is in contact with the surface. The rest of the bottom of the [...] Read more.

The effect of extreme water repellency, called the lotus effect, is caused by the formation of a Cassie–Baxter state in which only a small portion of the wetting liquid droplet is in contact with the surface. The rest of the bottom of the droplet is in contact with air pockets. Instrumental methods are often used to determine the textural features that cause this effect—scanning electron and atomic force microscopies, profilometry, etc. However, this result provides only an accurate texture model, not the actual information about the part of the surface that is wetted by the liquid. Here, we show a practical method for estimating the surface fraction of texture that has contact with liquid in a Cassie–Baxter wetting state. The method is performed using a set of ethanol–water mixtures to determine the contact angle of the textured and chemically equivalent flat surfaces of AlSI 304 steel, 7500 aluminum, and siloxane elastomer. We showed that the system of Cassie–Baxter equations can be solved graphically by the wetting diagrams introduced in this paper, returning a value for the texture surface fraction in contact with a liquid. We anticipate that the demonstrated method will be useful for a direct evaluation of the ability of textures to repel liquids, particularly superhydrophobic and superoleophobic materials, slippery liquid-infused porous surfaces, etc. Full article

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18 pages, 3549 KiB

Open AccessArticle

Influence of Ambient Relative Humidity on the Shrinkage Strain of Engineered Geopolymer Composites Based on Orthogonal Experimental Design

by Hongyin Wang, Yuelong Zheng and Zhenyun Yu

Materials 2024, 17(17), 4321; https://doi.org/10.3390/ma17174321 (registering DOI) - 30 Aug 2024

Abstract

With the aim to systematically analyze the ambient relative humidity on the shrinkage strain of Engineered Geopolymer Composites (EGCs), this paper studied four variables (fly ash to ground granulated blast furnace slag mass ratio, alkali content, water–binder ratio, and fiber volume content) though [...] Read more.

With the aim to systematically analyze the ambient relative humidity on the shrinkage strain of Engineered Geopolymer Composites (EGCs), this paper studied four variables (fly ash to ground granulated blast furnace slag mass ratio, alkali content, water–binder ratio, and fiber volume content) though orthogonal experimental design and three different relative humidity values (30%, 60%, and 100% RH). The results indicated that, for EGC specimens under 30% RH and 60% RH, the decrease in slag content and increase in alkali content both resulted in greater drying shrinkage. The addition of fibers effectively reduced the shrinkage strain, while a minor impact on shrinkage was presented by the W/B ratio. The first and second key factors affecting the drying shrinkage strain were the FA/GGBS ratio and the alkali content. The optimal ratio of FA/GGBS, alkali content, and fiber volume fraction were 0/100, 4%, and 1.5%, respectively. Dring shrinkage strain was decreased with the increase in ambient relative humidity. Compared with the shrinkage strain under 30% RH, the reduction in shrinkage strain under 60% RH and 100%RH was up to 46.1% and 107.5%, respectively. At last, a relationship between shrinkage strain and curing age under 30% and 60% RH was established with a fitting degree from 0.9492 to 0.9987, while no clear relationship was presented under 100% RH. The results in this paper provide a practical method for solving the shrinkage problem of EGCs. Full article

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18 pages, 14089 KiB

Open AccessArticle

Change in Surface Roughness on the Inner and Outer Surfaces of the Microtube during Hollow Sinking

by Hayate Sakaguchi, Takuma Kishimoto, Saki Suematsu, Kenichi Tashima, Koichi Kano, Satoshi Kajino, Shiori Gondo and Shinsuke Suzuki

Materials 2024, 17(17), 4320; https://doi.org/10.3390/ma17174320 - 30 Aug 2024

Abstract

Hollow sinking experiments and tensile tests were conducted to clarify the evolution of surface roughness during hollow sinking. Stainless steel tubes (outer diameter: 1.5 mm; wall thickness: 0.045 mm) featuring a single grain spanning the wall thickness achieved via annealing as the starting [...] Read more.

Hollow sinking experiments and tensile tests were conducted to clarify the evolution of surface roughness during hollow sinking. Stainless steel tubes (outer diameter: 1.5 mm; wall thickness: 0.045 mm) featuring a single grain spanning the wall thickness achieved via annealing as the starting material. The tube was drawn without an internal tool using a draw bench by controlling the tube drawing speed ratio of the die entrance and exit sides. The surface roughnesses of the inner and outer surfaces at the die entrance and exit sides of the drawn tube were compared with the surface roughnesses of the inner and outer surfaces under the uniaxial tensile deformation of the starting material. As a result, two major findings were revealed; the surface roughness formation behavior during the hollow sinking; the uniaxial tensile deformation exhibits a tube on both sides of the entrance and the exit of a die. Former uniaxial tensile deformation forms surface roughness of the tube at the die-entrance-side. However, hollow sinking reduces the roughness. The tube keeps its small roughness even though it is applied the later uniaxial tensile deformation behind the die exit. Furthermore, the conventional formula to predict the surface roughness of a metal sheet caused by the uniaxial tensile deformation can predict the surface roughness of a tube in the hollow sinking. At both die entrance and exit sides, the roughness of the inner surface was larger than that of the outer surface at the die entrance and exit side. The outer surface of the tube contacts the inside of a die when the tube passes through the die. The height of the convex parts decreased at that moment. Hollow sinking suppressed the increase in surface roughness of the inner surface as the outer surface was smoothed in the die. However, due to the formation of surface roughness after leaving the die, there is an overall increasing trend in inner surface roughness. Full article

(This article belongs to the Special Issue Forming Technologies and Mechanical Properties of Advanced Materials - 2nd Volume)

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13 pages, 7766 KiB

Open AccessArticle

The Influence of Post-Treatment on Micropore Evolution and Mechanical Performance in AlSi10Mg Alloy Manufactured by Laser Powder Bed Fusion

by Qing Pu, Jinbiao Qian, Yingwei Zhang, Shangjing Yang, Hongshou Huang, Qi Chao and Guohua Fan

Materials 2024, 17(17), 4319; https://doi.org/10.3390/ma17174319 (registering DOI) - 30 Aug 2024

Abstract

Gas-induced porosity is almost inevitable in additively manufactured aluminum alloys due to the evaporation of low-melting point elements (e.g., Al, Mg, and Zn) and the encapsulation of gases (e.g., hydrogen) during the multiple-phase reaction in the melt pool. These micropores are highly unstable [...] Read more.

Gas-induced porosity is almost inevitable in additively manufactured aluminum alloys due to the evaporation of low-melting point elements (e.g., Al, Mg, and Zn) and the encapsulation of gases (e.g., hydrogen) during the multiple-phase reaction in the melt pool. These micropores are highly unstable during post-heat treatment at elevated temperatures and greatly affect mechanical properties and service reliability. In this study, the AlSi10Mg samples prepared by LPBF were subjected to solution heat treatment at 560 °C for 0.5 and 2 h, followed by artificial aging at 160 °C, 180 °C and 200 °C, respectively. The defect tolerance of gas porosity and associated damage mechanisms in the as-built and heat treated AlSi10Mg alloy were elucidated using optical, scanning electron microscopic analysis, X-ray micro computed tomography (XCT) and room temperature tensile testing. The results showed the defect tolerance of AlSi10Mg alloy prepared by LPBF was significantly reduced by the artificial aging treatment due to the precipitation of Mg-Si phases. Fracture analysis showed that the cooperation of fine precipitates and coarsened micropores assists nucleation and propagation of microcracks sites due to stress concentration upon tensile deformation and reduces the tensile elongation at break. Full article

(This article belongs to the Special Issue Heat Treatment and Additive Manufacturing of Alloys: Processing, Properties and Simulations)

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14 pages, 17420 KiB

Open AccessArticle

Electrospun Polymeric Fiber Systems Inoculated with Cyanoacrylate Tissue Adhesive: A Novel Hemostatic Alternative during Open Surgery

by Victor P. Tosa, Alexandru Ilie-Ene, Septimiu C. Tripon, Amalia Mesaros, Radu Fechete, Nicoleta Tosa, Alexandra Csapai, George C. Dindelegan and Catalin O. Popa

Materials 2024, 17(17), 4318; https://doi.org/10.3390/ma17174318 - 30 Aug 2024

Abstract

Natural-based and synthetic tissue adhesives have attracted extensive attention in the last two decades for their ability to stabilize uncontrolled bleeding instances. However; these materials present several drawbacks during use that scientists have tried to minimize in order to optimize their usage. This [...] Read more.

Natural-based and synthetic tissue adhesives have attracted extensive attention in the last two decades for their ability to stabilize uncontrolled bleeding instances. However; these materials present several drawbacks during use that scientists have tried to minimize in order to optimize their usage. This study comprises the development of a novel wound dressing, combining the excellent properties of polylactic acid (PLA) non-woven textile, as substrate, obtained through electrospinning, and a cyanoacrylate-based (CA) tissue adhesive, for rapid hemostatic action. Thus, the fabrication of electrospun PLA membranes at three different PLA concentrations, the design and manufacturing of the support system and the production of surgical patches were carried out. SEM and FT-IR methods were employed for analyzing the morphology as well as the indicative markers for the shelf life evolution of the obtained patches. PLA fibers with well-defined structures and a mean diameter varying between 4.6 and 7.24 μm were obtained with the increase of the concentration of the PLA solutions. In vivo tests on a rat model as well as peeling tests for good patch adhesion on liver fragments harvested from the test animals, with a limit for the strength of the liver tissue of 1.5 N, were carried out. The devices exhibited excellent adhesion to the parenchymal tissue and a long enough shelf life to be used with success in surgical procedures, also facilitating prompt hemostatic action. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))

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25 pages, 3704 KiB

Open AccessArticle

Production of Low-Cost Adsorbents within a Circular Economy Approach: Use of Spruce Sawdust Pretreated with Desalination Brine to Adsorb Methylene Blue

by Dorothea Politi, Elias Sakellis and Dimitrios Sidiras

Materials 2024, 17(17), 4317; https://doi.org/10.3390/ma17174317 - 30 Aug 2024

Abstract

A sustainable low-cost activated carbon substitute was produced based on pretreated lignocellulosic biomass, especially spruce sawdust. A harmful liquid waste, desalination brine, was used for the treatment of a solid wood industry waste, spruce sawdust. This approach is in the circular economy theory [...] Read more.

A sustainable low-cost activated carbon substitute was produced based on pretreated lignocellulosic biomass, especially spruce sawdust. A harmful liquid waste, desalination brine, was used for the treatment of a solid wood industry waste, spruce sawdust. This approach is in the circular economy theory and aims at the decarbonization of the economy. Pretreated sawdust was tested as an adsorbent appropriate for the removal of a commonly used pollutant, methylene blue, from industrial wastewater. The adsorption capacity of the pretreated material was found to have increased four times compared to the untreated one in the case that the Freundlich equation was fitted to the isotherms’ data, i.e., the one with the best fit to the isotherm’s experimental data of the three isotherm models used herein. The treatment experimental conditions with desalination brine that gave maximum adsorption capacity correspond to a 1.97 combined severity factor in logarithmic form value. Moreover, a kinetic experiment was carried out with regard to the methylene blue adsorption process. The desalination brine-pretreated sawdust adsorption capacity increased approximately two times compared to the untreated one, in the case when the second-order kinetic equation was used, which had the best fit of the kinetic data of the three kinetic models used herein. In this case, the pretreatment experimental conditions that gave maximum adsorption capacity correspond to −1.049 combined severity factor in logarithmic form. Industrial scale applications can be based on the kinetic data findings, i.e., spruce sawdust optimal pretreatment conditions at 200 °C, for 25 min, with brine solution containing 98.12 g L⁻¹ NaCl, as they are related to a much shorter adsorption period compared to the isotherm data. Full article

(This article belongs to the Special Issue Recovery and Preparation of Innovative Products and Composite Materials for Environmental Applications)

14 pages, 3009 KiB

Open AccessArticle

Enhanced Activation in Phosphorous-Doped Silicon via Dual-Beam Laser Annealing

by Rasheed Ayinde Taiwo, Yeongil Son, Joonghan Shin and Yusuff Adeyemi Salawu

Materials 2024, 17(17), 4316; https://doi.org/10.3390/ma17174316 - 30 Aug 2024

Abstract

In this study, we conduct a comparative analysis of single-beam laser annealing (SBLA) and dual-beam laser annealing (DBLA) techniques for semiconductor manufacturing. In the DBLA approach, two laser beams were precisely aligned to simultaneously heat a phosphorus-doped silicon (Si) wafer. The main objective [...] Read more.

In this study, we conduct a comparative analysis of single-beam laser annealing (SBLA) and dual-beam laser annealing (DBLA) techniques for semiconductor manufacturing. In the DBLA approach, two laser beams were precisely aligned to simultaneously heat a phosphorus-doped silicon (Si) wafer. The main objective was to investigate the impact of the two annealing techniques on the electrical properties, crystalline structure, and diffusion profile of the treated phosphorus-doped Si at equivalent laser powers. Both SBLA and DBLA improved the electrical properties of the phosphorus-doped Si, evidenced by increased carrier concentration and reduced carrier mobility. Additionally, the crystalline structure of the phosphorus-doped Si showed favorable modifications, with no defects and improved crystallinity. While both SBLA and DBLA produced similar phosphorus profiles with no significant redistribution of dopants compared to the as-implanted sample, DBLA achieved a higher activation ratio than SBLA. Although the results suggest improved dopant activation with minimal diffusion, further studies are needed to clearly confirm the effect of DBLA on dopant activation and diffusion. Full article

(This article belongs to the Special Issue Advanced Materials and Manufacturing Processes)

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16 pages, 11171 KiB

Open AccessArticle

Evaluation of Macro- and Micro-Geometry of Models Made of Photopolymer Resins Using the PolyJet Method

by Paweł Turek, Anna Bazan, Grzegorz Budzik, Tomasz Dziubek and Łukasz Przeszłowski

Materials 2024, 17(17), 4315; https://doi.org/10.3390/ma17174315 - 30 Aug 2024

Abstract

Additive manufacturing (AM) techniques are among the fastest-growing technologies for producing even the most geometrically complex models. Unfortunately, the lack of development of metrology guidelines for these methods, related to dimensional and geometry accuracy and surface roughness, significantly limits the commercialization of finished [...] Read more.

Additive manufacturing (AM) techniques are among the fastest-growing technologies for producing even the most geometrically complex models. Unfortunately, the lack of development of metrology guidelines for these methods, related to dimensional and geometry accuracy and surface roughness, significantly limits the commercialization of finished products manufactured using these methods. This paper aims to evaluate the macro- and micro-geometry of models manufactured using the PolyJet method from three types of photopolymer resins: Digital ABS Plus, RGD 720, and Vero Clear. For this purpose, test parts were designed and then manufactured on an Object 350 Connex3 3D printer. The Atos II Triple Scan optical system and the InfiniteFocusG4 microscope were used to evaluate macro- and micro-geometry, respectively. For both systems, measurement procedures were developed to obtain statistical results for evaluating geometric accuracy and surface roughness parameters. In the case of macro-geometry, for Digital ABS Plus and Vero Clear materials, 50% of the central deviations (between first quartile Q1 and third quartile Q3) lie within the range (−0.06, 0.03 mm) and for RGD 720 material within the range (−0.08, 0.01 mm). For micro-geometry, the arithmetic mean height (Sa) values for the Digital ABS Plus and Vero Clear samples were approximately 1.6 and 2.0 µm, respectively, while for RGD 720, it was 15.9 µm. The total roughness height expressed by reduced peak height (Spk) + core height (Sk) + reduced dale depth (Svk) for the Digital ABS Plus and Vero Clear samples was approximately 9.1 and 10.5 µm, respectively, while for the RGD 720, it was 101.9 µm. Full article

(This article belongs to the Special Issue Material Surface Topography Measurement, Analysis and Characterization)

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19 pages, 64403 KiB

Open AccessArticle

Improvement in Mechanical Properties of Completely Decomposed Granite Soil Concrete Fabricated with Pre-Setting Pressurization

by Yi Song, Zhongqi Quentin Yue and Yanlu Ding

Materials 2024, 17(17), 4314; https://doi.org/10.3390/ma17174314 - 30 Aug 2024

Abstract

This paper investigates the effectiveness of applying continuous high-compression pressure on the initial setting of fresh concrete to produce hardened concrete materials with excellent mechanical properties. A novel experimental apparatus was self-designed and used for the pre-setting pressure application. The utilization of the [...] Read more.

This paper investigates the effectiveness of applying continuous high-compression pressure on the initial setting of fresh concrete to produce hardened concrete materials with excellent mechanical properties. A novel experimental apparatus was self-designed and used for the pre-setting pressure application. The utilization of the completely decomposed granite (CDG) soil as an alternative aggregate in concrete production was also explored. A total of twenty-eight specimens were fabricated using two types of fine aggregates, six mix ratios, two initial pressure values, and two distinct durations of the initial pressure application. The density and uniaxial compressive strength (UCS) of the specimens were examined to evaluate their mechanical qualities, while micro-CT tests with image analysis were used to quantify their porosity. The results indicated that the 10 MPa initial pre-setting pressurization can effectively eliminate the excess air and voids within the fresh concrete, therefore enhancing the mechanical properties of the hardened concrete specimens of various types. Compared with non-pressurized specimens, the porosity values of pressurized specimens were reduced by 73.11% to 86.53%, the density values were increased by 1.43% to 8.31%, and the UCS values were increased by 8.42% to 187.43%. These findings provide a reference for using a continuous high pre-setting compression pressure and using CDG soil as an aggregate in the fabrication of concrete materials with improved mechanical performance. Full article

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

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