Materials

17 pages, 6601 KiB

Open AccessArticle

Anti-Corrosion Flocking Surface with Enhanced Wettability and Evaporation

by Die Lu, Jing Ni, Zhen Zhang and Kai Feng

Materials 2024, 17(16), 4166; https://doi.org/10.3390/ma17164166 - 22 Aug 2024

Viewed by 712

The corrosion protection of tool steel surfaces is of significant importance for ensuring cutting precision and cost savings. However, conventional surface protection measures usually rely on toxic organic solvents, posing threats to the environment and human health. In this regard, an integrated process [...] Read more.

The corrosion protection of tool steel surfaces is of significant importance for ensuring cutting precision and cost savings. However, conventional surface protection measures usually rely on toxic organic solvents, posing threats to the environment and human health. In this regard, an integrated process of laser texturing and electrostatic flocking is introduced as a green anti-corrosion method on a high-speed steel (HSS) surface. Drawing from the principles of textured surface energy barrier reduction and fiber array capillary water evaporation enhancement, a flocking surface with a synergistic optimization of surface wettability and evaporation performance was achieved. Then, contact corrosion tests using 0.1 mol/L of NaCl droplets were performed. Contact angles representing wettability and change in droplet mass representing evaporation properties were collected. The elements and chemical bonds presented on the corroded surfaces were characterized by X-ray photoelectron spectroscopy (XPS). The results revealed that the flocking surface exhibited the lowest degree of corrosion when compared with smooth and textured surfaces. Corrosion resistance of the flocking surface was achieved through the rapid spread and evaporation of droplets, which reduced the reaction time and mitigated electrochemical corrosion. This innovative flocking surface holds promise as an effective treatment in anti-corrosion strategies for cutting tools. Full article

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22 pages, 4471 KiB

Open AccessArticle

Waste for Product—Synthesis and Electrocatalytic Properties of Palladium Nanopyramid Layer Enriched with PtNPs

by Magdalena Luty-Błocho, Adrianna Pach, Dawid Kutyła, Anna Kula, Stanisław Małecki, Piotr Jeleń and Volker Hessel

Materials 2024, 17(16), 4165; https://doi.org/10.3390/ma17164165 - 22 Aug 2024

Viewed by 730

Abstract

The presented research is the seed of a vision for the development of a waste-for-product strategy. Following this concept, various synthetic solutions containing low concentrations of platinum group metals were used to model their recovery and to produce catalysts. This is also the [...] Read more.

The presented research is the seed of a vision for the development of a waste-for-product strategy. Following this concept, various synthetic solutions containing low concentrations of platinum group metals were used to model their recovery and to produce catalysts. This is also the first report that shows the method for synthesis of a pyramid-like structure deposited on activated carbon composed of Pd and Pt. This unique structure was obtained from a mixture of highly diluted aqueous solutions containing both metals and chloride ions. The presence of functional groups on the carbon surface and experimental conditions allowed for: the adsorption of metal complexes, their reduction to metal atoms and enabled further hierarchical growth of the metal layer on the carbon surface. During experiments, spherical palladium and platinum nanoparticles were obtained. The addition of chloride ions to the solution promoted the hierarchical growth and formation of palladium nanopyramids, which were enriched with platinum nanoparticles. The obtained materials were characterized using UV–Vis, Raman, IR spectroscopy, TGA, SEM/EDS, and XRD techniques. Moreover, Pd@ROY, Pt@ROY, and Pd-Pt@ROY were tested as possible electrocatalysts for hydrogen evolution reactions. Full article

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

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10 pages, 2282 KiB

Open AccessArticle

Comparative Life Cycle Assessment of Bacterial and Thermochemical Retting of Hemp

by Yu Fu, Hongmei Gu, H. Felix Wu and Sheldon Q. Shi

Materials 2024, 17(16), 4164; https://doi.org/10.3390/ma17164164 - 22 Aug 2024

Viewed by 677

Abstract

The processes of hemp bast fiber retting, forming, and drying offer the opportunity for value-added products such as natural fiber-reinforced composites. A new process for the retting of raw bast fibers through enzyme-triggered self-cultured bacterial retting was developed in the lab-scale setup. This [...] Read more.

The processes of hemp bast fiber retting, forming, and drying offer the opportunity for value-added products such as natural fiber-reinforced composites. A new process for the retting of raw bast fibers through enzyme-triggered self-cultured bacterial retting was developed in the lab-scale setup. This study focused on comparing the energy consumption and environmental impacts of this bacterial retting process with the thermochemical retting process currently widely used to obtain lignocellulosic fibers for composites. The gate-to-gate life cycle assessment (LCA) models of the two retting processes were constructed to run a comparison analysis using the TRACI (the tool for the reduction and assessment of chemical and other environmental impacts) method for environmental impacts and the cumulative energy demand (CED) method for energy consumptions. This work has demonstrated the advantages of the bacterial retting method from an environmental standpoint. The result of our research shows about a 24% gate-to-gate reduction in CED for bacterial retting and 20–25% lower environmental impacts relating to global warming, smog formation, acidification, carcinogenics, non-carcinogenics, respiratory effects, ecotoxicity, and fossil fuel depletion when compared to that of thermochemical retting. Full article

(This article belongs to the Special Issue Bio-Based Natural Fiber Composite Materials)

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20 pages, 7710 KiB

Open AccessArticle

Synthesis of MnFe₂O₄ Spinel on Rusted Q235 Steel Surface and Its Corrosion Resistance Properties

by Bai-Ao Feng, Xu Miao and Ting-An Zhang

Materials 2024, 17(16), 4163; https://doi.org/10.3390/ma17164163 - 22 Aug 2024

Viewed by 621

Abstract

Corrosion of steel is an issue that cannot be ignored in contemporary society. Due to large-scale corrosion, it is urgent to develop a surface treatment process that enhances the corrosion resistance of steel, allowing for application in various scenarios as needed. This study [...] Read more.

Corrosion of steel is an issue that cannot be ignored in contemporary society. Due to large-scale corrosion, it is urgent to develop a surface treatment process that enhances the corrosion resistance of steel, allowing for application in various scenarios as needed. This study aims to investigate a novel surface treatment process to extend the service life of corroded Q235 steel, reduce its sensitivity to corrosion, and enable its use in multiple environments. This study employs the sol-gel method, using manganese nitrate solutions of varying concentrations to treat the surface of Q235 steel after different electrolysis times. The optimal conditions for precursor preparation were found to be a Mn²⁺ concentration of 0.1 mol/L and an electrolysis time of 2 h. Electrochemical tests using NaCl solutions of different concentrations revealed a significant reduction in the corrosion current for the composite coating based on Q235 steel treated with this method in NaCl solutions with wt.% = 1, 2, 3, 4, 5. Furthermore, the resistance to corrosion was strongest in the NaCl solution with a concentration of 1 wt.% where the corrosion current decreased from 24.8 µA/cm² to 6.79 µA/cm². Additionally, the coating was found to be diffusion-controlled in the early stages of the corrosion process and charge transfer-controlled in the later stages. The MnFe₂O₄ spinel coating demonstrated the greatest enhancement in corrosion resistance in the wt.% = 1 NaCl solution. Full article

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

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13 pages, 8159 KiB

Open AccessArticle

Molecular Dynamics Simulation Study of Aluminum–Copper Alloys’ Anisotropy under Different Loading Conditions and Different Crystal Orientations

by Xiaodong Wu and Wenkang Zhang

Materials 2024, 17(16), 4162; https://doi.org/10.3390/ma17164162 - 22 Aug 2024

Viewed by 760

Abstract

The commonly used aluminum–copper alloys in industry are mainly rolled plates and extruded or drawn bars. The aluminum–copper alloys’ anisotropy generated in the manufacturing process is unfavorable for subsequent applications. Its underlying mechanism shall be interpreted from a microscopic perspective. This paper conducted [...] Read more.

The commonly used aluminum–copper alloys in industry are mainly rolled plates and extruded or drawn bars. The aluminum–copper alloys’ anisotropy generated in the manufacturing process is unfavorable for subsequent applications. Its underlying mechanism shall be interpreted from a microscopic perspective. This paper conducted the loading simulation on Al–4%Cu alloy crystals at the microscopic scale with molecular dynamics technology. Uniaxial tension and compression loading were carried out along three orientations: X-<

\bar{1} 12

>, Y-<

1 \bar{1} 1

>, and Z-<110>. It analyzes the micro-mechanisms that affect the performance changes of aluminum–copper alloys through the combination of stress–strain curves and different organizational analysis approaches. As shown by the results, the elastic modulus and yield strength are the highest under tension along the <

1 \bar{1} 1

> direction. Such is the case for the reasons below: The close-packed plane of atoms ensures large atomic binding forces. In addition, the Stair-rod dislocation forms a Lomer–Cottrell dislocation lock, which has a strengthening effect on the material. The elastic modulus and yield strength are the smallest under tension along the <110> direction, and the periodic arrangement of HCP atom stacking faults serves as the main deformation mechanism. This is because the atomic arrangement on the <110> plane is relatively loose, which tends to cause atomic misalignment. When compressed in different directions, the plastic deformation mechanism is mainly dominated by dislocations and stacking faults. When compressed along the <110> direction, it has a relatively high dislocation density and the maximum yield strength. That should be attributed to the facts below. As the atomic arrangement of the <110> plane itself was not dense originally, compression loading would cause an increasingly tighter arrangement. In such a case, the stress could only be released through dislocations. This research aims to provide a reference for optimizing the processing technology and preparation methods of aluminum–copper alloy materials. Full article

(This article belongs to the Special Issue Mechanical Behaviors of Materials: Modelling and Measurement (2nd Edition))

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11 pages, 1960 KiB

Open AccessArticle

Silicon Carbide Nanowire Based Integrated Electrode for High Temperature Supercapacitors

by Shiyu Sha, Chang Liang, Songyang Lv, Lin Xu, Defu Sun, Jiayue Yang, Lei Zhang and Shouzhi Wang

Materials 2024, 17(16), 4161; https://doi.org/10.3390/ma17164161 - 22 Aug 2024

Viewed by 993

Abstract

Silicon carbide (SiC) single crystals have great prospects for high-temperature energy storage due to their robust structural stability, ultrahigh power output, and superior temperature stability. However, energy density is an essential challenge for SiC-based devices. Herein, a facile two-step strategy is proposed for [...] Read more.

Silicon carbide (SiC) single crystals have great prospects for high-temperature energy storage due to their robust structural stability, ultrahigh power output, and superior temperature stability. However, energy density is an essential challenge for SiC-based devices. Herein, a facile two-step strategy is proposed for the large-scale synthesis of a unique architecture of SiC nanowires incorporating MnO₂ for enhanced supercapacitors (SCs), arising from the synergy effect between the SiC nanowires as a highly conductive skeleton and the MnO₂ with numerous active sites. The SiC@MnO₂ integrated electrode-based SCs with ionic liquid (IL) electrolytes were assembled and delivered outstanding energy and power density, as well as a great lifespan at 150 °C. This impressive work offers a novel avenue for the practical application of SiC-based electrochemical energy storage devices with high energy density under high temperatures. Full article

(This article belongs to the Special Issue Research Progress of Advanced Crystals: Growth and Doping)

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15 pages, 2239 KiB

Open AccessArticle

Elastomeric Compositions of Ethylene–Norbornene Copolymer Containing Biofillers Based on Coffee and Tea Waste

by Aneta Malicka, Kamila Rułka, Malgorzata Latos-Brozio and Anna Masek

Materials 2024, 17(16), 4160; https://doi.org/10.3390/ma17164160 - 22 Aug 2024

Viewed by 722

Abstract

The development of eco-friendly elastomeric materials has become an important issue in recent years. In this work, thermoplastic elastomer samples of an ethylene–norbornene copolymer (EN) with coffee and tea biofillers mixed with typical fillers such as montmorillonite (MMT), silica (SiO₂), and [...] Read more.

The development of eco-friendly elastomeric materials has become an important issue in recent years. In this work, thermoplastic elastomer samples of an ethylene–norbornene copolymer (EN) with coffee and tea biofillers mixed with typical fillers such as montmorillonite (MMT), silica (SiO₂), and cellulose were investigated. The aim of this research was to determine the effect of fillers on the properties of the materials and to assess their degradability after two ultraviolet (UV) aging cycles (200, 400 h). The scientific novelty of this work is the assessment of the anti-aging effect of simultaneous biofillers–stabilizers based on coffee and tea waste. The surfaces of the obtained polymer compositions were examined using infrared spectroscopy (FTIR-ATR). Contact angles were determined, and surface energy was calculated. The mechanical properties were tested, and the influence of plant fillers and aging on the color change in the materials was analyzed. The combination of coffee with silica, MMT, and cellulose fillers limited the migration of fatty acids and other compounds from the biofiller to the EN surface (FTIR analysis). Based on the aging coefficients K, it was shown that all coffee- and tea-based fillers stabilized the polymer compositions during UV aging (400 h). The results allowed the authors to determine the importance and impact of waste plant fillers on the degradability of the synthetic EN. Full article

(This article belongs to the Special Issue New Advances in Elastomer Materials and Its Composites)

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18 pages, 5957 KiB

Open AccessArticle

Temperature Effect on Deformation Mechanisms and Mechanical Properties of Welded High-Mn Steels for Cryogenic Applications

by Minha Park, Gang Ho Lee, Geon-Woo Park, Gwangjoo Jang, Hyoung-Chan Kim, Sanghoon Noh, Jong Bae Jeon, Byoungkoo Kim and Byung Jun Kim

Materials 2024, 17(16), 4159; https://doi.org/10.3390/ma17164159 - 22 Aug 2024

Viewed by 685

Abstract

High-manganese steel (high-Mn) is valuable for its excellent mechanical properties in cryogenic environments, making it essential to understand its deformation behavior at extremely low temperatures. The deformation behavior of high-Mn steels at extremely low temperatures depends on the stacking fault energy (SFE) that [...] Read more.

High-manganese steel (high-Mn) is valuable for its excellent mechanical properties in cryogenic environments, making it essential to understand its deformation behavior at extremely low temperatures. The deformation behavior of high-Mn steels at extremely low temperatures depends on the stacking fault energy (SFE) that can lead to the formation of deformation twins or transform to ε-martensite or α′-martensite as the temperature decreases. In this study, submerged arc welding (SAW) was applied to fabricate thick pipes for cryogenic industry applications, but it may cause problems such as an uneven distribution of manganese (Mn) and a large weldment. To address these issues, post-weld heat treatment (PWHT) is performed to achieve a homogeneous microstructure, enhance mechanical properties, and reduce residual stress. It was found that the difference in Mn content between the dendrite and interdendritic regions was reduced after PWHT, and the SFE was calculated. At cryogenic temperatures, the SFE decreased below 20 mJ/m², indicating the martensitic transformation region. Furthermore, an examination of the deformation behavior of welded high-Mn steels was conducted. This study revealed that the tensile deformed, as-welded specimens exhibited ε and α′-martensite transformations at cryogenic temperatures. However, the heat-treated specimens did not undergo α′-martensite transformations. Moreover, regardless of whether the specimens were subjected to Charpy impact deformation before or after heat treatment, ε and α′-martensite transformations did not occur. Full article

(This article belongs to the Special Issue Advances in Solid-State Welding Processes)

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19 pages, 11368 KiB

Open AccessArticle

Influence of Mineral Additives on Strength Properties of Standard Mortar

by Grzegorz Rogojsz and Tomasz Rudnicki

Materials 2024, 17(16), 4158; https://doi.org/10.3390/ma17164158 - 22 Aug 2024

Viewed by 717

Abstract

In the article, the authors presented the results of research on the assessment of the effect of selected mineral additives on the strength properties of the standard mortar. The modification of the composition of the standard mortar made on the basis of CEM [...] Read more.

In the article, the authors presented the results of research on the assessment of the effect of selected mineral additives on the strength properties of the standard mortar. The modification of the composition of the standard mortar made on the basis of CEM I 42.5R cement and quartz sand consisted of using seven selected mineral additives in the form of compacted microsilica, Mikrosill microsilica, limestone flour, glass flour, glass granulate, basalt flour, and fly ash in the amounts of 10 and 20% in relation to cement as its substitute. Reducing the share of cement in the standard mortar by 10% has a beneficial effect on improving the compressive strength by over 40% with the addition of microsilica, and in the case of bending strength, even by 10%. Full article

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17 pages, 4182 KiB

Open AccessArticle

Activated Carbon for CO₂ Adsorption from Avocado Seeds Activated with NaOH: The Significance of the Production Method

by Joanna Siemak, Grzegorz Mikołajczak, Magdalena Pol-Szyszko and Beata Michalkiewicz

Materials 2024, 17(16), 4157; https://doi.org/10.3390/ma17164157 - 22 Aug 2024

Viewed by 1007

Abstract

The rise in atmospheric greenhouse gases like CO₂ is a primary driver of global warming. Human actions are the primary factor behind the surge in CO₂ levels, contributing to two-thirds of the greenhouse effect over the past decade. This study focuses [...] Read more.

The rise in atmospheric greenhouse gases like CO₂ is a primary driver of global warming. Human actions are the primary factor behind the surge in CO₂ levels, contributing to two-thirds of the greenhouse effect over the past decade. This study focuses on the chemical activation of avocado seeds with sodium hydroxide (NaOH). The influence of various preparation methods was studied under the same parameters: carbon precursor to NaOH mass ratio, carbonization temperature, and nitrogen flow. For two samples, preliminary thermal treatment was applied (500 °C). NaOH was used in the form of a saturated solution as well as dry NaOH. The same temperature of 850 °C of carbonization combined with chemical activation was applied for all samples. The applied modifications resulted in the following textural parameters: specific surface area from 696 to 1217 m²/g, total pore volume from 0.440 to 0.761 cm³/g, micropore volume from 0.159 to 0.418 cm³/g. The textural parameters were estimated based on nitrogen sorption at −196 °C. The XRD measurements and SEM pictures were also performed. CO₂ adsorption was performed at temperatures of 0, 10, 20, and 30 °C and pressure up to 1 bar. In order to calculate the CO₂ selectivity over N₂ nitrogen adsorption at 20 °C was investigated. The highest CO₂ adsorption (4.90 mmol/g) at 1 bar and 0 °C was achieved. Full article

(This article belongs to the Special Issue Progress in Carbon-Based Materials)

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17 pages, 11808 KiB

Open AccessArticle

Assessment of Microstructural Features of a Silchrome 1 Exhaust Valve of a Harley-Davidson WLA World War II Motorcycle

by Jan Růžička, Ali Alıcıoğlu, Jérémie Bouquerel, Pavel Novák and Jean-Bernard Vogt

Materials 2024, 17(16), 4156; https://doi.org/10.3390/ma17164156 - 22 Aug 2024

Viewed by 738

Abstract

The paper aims at documenting the material employed in 1942 for the fabrication of an exhaust valve for a Harley-Davidson WLA/WLC motorcycle and assesses the material features with modern steel standard specifications and treatment. Facing properties of the original historical parts of technical [...] Read more.

The paper aims at documenting the material employed in 1942 for the fabrication of an exhaust valve for a Harley-Davidson WLA/WLC motorcycle and assesses the material features with modern steel standard specifications and treatment. Facing properties of the original historical parts of technical heritage objects according to modern standards is a rare discipline, as these objects are nowadays in collections of museums or private collectors and experimental instrumental analyses are strictly forbidden. In this case, a preserved accessible unused surplus replacement kit was studied. The microstructure was assessed by light optical and scanning electron microscopy, electron probe micro-analysis and by heat treatment–hardness correlation. It was found that the valve was made of Silchrome 1 steel in coherence with the X45CrSi9-3 steel modern material standard, but with a slightly higher content of phosphorus and sulfur. Microscopic observations and hardness profile testing suggested a tempered martensitic structure (sorbite) with very fine grains uniformly distributed in the valve and an even heat treatment. Heat treatment–hardness experimentation demonstrated that the original heat treatment cannot be achieved by the modern standard procedure. The tempering temperature was surprisingly deduced to be lower than the recommended one according to the modern standard, which contrasts with the service temperature indicated in the contemporary motorcycle mechanics handbook. Full article

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10 pages, 5494 KiB

Open AccessArticle

Microstructure and Mechanical Properties of the Powder Metallurgy Nb-16Si-24Ti-2Al-2Cr Alloy

by Feng Wen, Wentao Liu, Ao Fu, Qianli Huang, Jian Wang, Yuankui Cao, Jingwen Qiu and Bin Liu

Materials 2024, 17(16), 4155; https://doi.org/10.3390/ma17164155 - 22 Aug 2024

Viewed by 511

Abstract

The Nb-16Si-24Ti-2Al-2Cr alloy was prepared by plasma rotating electrode process (PREP) technology and the hot-pressing (HP) method, and the effects of sintering temperature on the microstructure, mechanical properties and fracture behavior were investigated. The HP alloys sintered at temperatures below 1400 °C are [...] Read more.

The Nb-16Si-24Ti-2Al-2Cr alloy was prepared by plasma rotating electrode process (PREP) technology and the hot-pressing (HP) method, and the effects of sintering temperature on the microstructure, mechanical properties and fracture behavior were investigated. The HP alloys sintered at temperatures below 1400 °C are composed of Nbss (Nb solid solution), Nb₃Si and Nb₅Si₃ phases. When the sintering temperature reaches 1450 °C, the Nb₃Si phase is completely decomposed into Nbss and Nb₅Si₃ phases. Meanwhile, the microstructure coarsens significantly. Compared with the cast alloy, the HP alloy shows better mechanical properties. The fracture toughness of the alloy sintered at 1400 °C reaches 20.2 MPa·m^1/2, which exceeds the application threshold. The main reason for the highest fracture toughness is attributed to the decomposition of large-sized brittle Nb₃Si phase and the formation of a fine microstructure, which greatly increases the number of phase interfaces and improves the chance of crack deflection. In addition, the reduction in the size and content of silicides also reduces their plastic constraints on the ductile Nbss phase. Full article

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14 pages, 12302 KiB

Open AccessArticle

Post-Tensioned Hollow-Core Concrete Slabs with Unbonded Tendons for Truck Scale Platforms: Design Assumptions and Tests

by Rafał Stanisław Szydłowski, Barbara Łabuzek and Łukasz Bednarski

Materials 2024, 17(16), 4154; https://doi.org/10.3390/ma17164154 - 22 Aug 2024

Viewed by 541

Abstract

At Cracow University of Technology, attempts were made to develop national truck scale platforms with a capacity of 60 tons, made from prestressed concrete. For this work, we designed slabs partially prestressed with unbonded tendons featuring a cross-section of 1.00 × 0.28 m [...] Read more.

At Cracow University of Technology, attempts were made to develop national truck scale platforms with a capacity of 60 tons, made from prestressed concrete. For this work, we designed slabs partially prestressed with unbonded tendons featuring a cross-section of 1.00 × 0.28 m and a span of 5.94 m. To reduce the weight of the slabs, four channels made from commonly used ø110 × 2.2 mm PVC pipes were used. In this way, we created post-tensioned hollow-core slabs. Due to the unpredictable behavior of slabs operating in a cracked state under a repetitive load, two slabs were subjected to cyclic loads amounting to 1,000,000 cycles with different load values. This paper presents the basic design principles and design details of the slabs, as well as the methodology and results of the research conducted. Lastly, we provide appropriate conclusions directed at further optimizing the slabs. Full article

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

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20 pages, 3592 KiB

Open AccessArticle

Marginal Aggregates: The Role of Clays

by Arnon Bentur and Pavel Larianovsky

Materials 2024, 17(16), 4153; https://doi.org/10.3390/ma17164153 - 22 Aug 2024

Viewed by 470

Abstract

Clays are components in the fine portion of aggregates, less than 75 microns in size (micro-fines), which are usually washed away when producing coarse or fine (manufactured sand) aggregates in quarries. When marginal sources of aggregates are being used, the content of this [...] Read more.

Clays are components in the fine portion of aggregates, less than 75 microns in size (micro-fines), which are usually washed away when producing coarse or fine (manufactured sand) aggregates in quarries. When marginal sources of aggregates are being used, the content of this washed portion can be quite high, and there is an incentive to keep as much of it in the aggregate, including the clays. The present paper presents a comprehensive treatment of the role of clays in terms of the characterization of their composition and quantification of their effects on the rheological and mechanical properties of cementitious systems, as well as the means to mitigate deleterious influences. It is shown that the strategy for neutralizing the effect of micro-fines containing clays on increased water demand in concrete can be quantified in terms of the combination of their content in concrete and their nature as characterized by the methylene blue value (MBV); this is a more rational approach to considering their influence than their content in specific aggregates as specified in standards. The effect of low and medium MBV aggregates on the water requirement can be neutralized by lignosulfonates when their content in the concrete is below a threshold value of about 150 kg/m³; polycarboxylates (PC) are required at higher contents; for high MBV aggregates, a combination of PC and clay mitigating admixture (CMA) is required. It is also demonstrated that with proper treatment, such micro-fines can be turned into useful fillers, enhancing the strength of concrete and thus also serving as a means for reducing cement content. 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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11 pages, 6181 KiB

Open AccessArticle

Effect of Microwave Irradiation on Lead Adsorption Properties of Vermiculite with Different Particle Sizes

by Yunzhu Chen, Hongjuan Sun, Tongjiang Peng, Wenjin Ding and Hongmei Yin

Materials 2024, 17(16), 4152; https://doi.org/10.3390/ma17164152 - 22 Aug 2024

Viewed by 625

Abstract

The expansion of vermiculite using microwave irradiation is an environmentally friendly and efficient method that can enhance the material’s adsorption performance. This study investigated the microwave irradiation of vermiculite with five different particle sizes (4/2/1/0.5/0.2 mm) and found that the adsorption capacity for [...] Read more.

The expansion of vermiculite using microwave irradiation is an environmentally friendly and efficient method that can enhance the material’s adsorption performance. This study investigated the microwave irradiation of vermiculite with five different particle sizes (4/2/1/0.5/0.2 mm) and found that the adsorption capacity for Pb²⁺ increased with larger particle sizes. The equilibrium adsorption capacity reached 15.98 mg/g at 4 mm, representing a 45.01% improvement compared to 0.2 mm. The pseudo-second-order kinetic model effectively described the adsorption kinetics. No significant differences were observed in the specific surface area and pore size distribution of all samples. Thermogravimetric quantitative analysis revealed that larger particle sizes retained interlayer water more effectively. As the particle size decreased, the interlayer water content generally showed a decreasing trend. Fourier-transform infrared spectroscopy analysis also indicated that the -OH groups in larger particle sizes exhibited higher stability. The results suggest that the high content and stability of -OH groups may be key factors in the enhanced adsorption performance for Pb²⁺. This provides new insights for the preparation of environmentally friendly adsorbent materials rich in hydroxyl groups. Full article

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19 pages, 4387 KiB

Open AccessArticle

Comparative Study of the Structural, Microstructural, and Mechanical Properties of Geopolymer Pastes Obtained from Ready-to-Use Metakaolin–Quicklime Powders and Classic Geopolymers

by Maroua Zerzouri, Rabah Hamzaoui, Layella Ziyani and Saliha Alehyen

Materials 2024, 17(16), 4151; https://doi.org/10.3390/ma17164151 - 22 Aug 2024

Cited by 1 | Viewed by 981

Abstract

This study compares the structural, microstructural, thermal, and mechanical properties of geopolymer pastes (GPs) created through traditional methods and those derived from ready-to-use powders for geopolymer (RUPG) materials. The metakaolin (MK) precursor was activated using a sodium silicate solution or CaO and MOH [...] Read more.

This study compares the structural, microstructural, thermal, and mechanical properties of geopolymer pastes (GPs) created through traditional methods and those derived from ready-to-use powders for geopolymer (RUPG) materials. The metakaolin (MK) precursor was activated using a sodium silicate solution or CaO and MOH (where M is Na or K). Various ratios of precursor/activator and Na₂SiO₃ or CaO/MOH were tested to determine the optimal combination. For RUPG, the MK precursor was activated by replacing the sodium silicate solution with quicklime. Metakaolin, alkaline hydroxide, and quicklime powders were mixed at different CaO ratios (wt%) and subjected to extensive ball milling to produce RUPG. The RUPG was then hydrated, molded, and cured at 20 °C and 50% relative humidity until testing. Analytical methods were used to characterize the raw and synthesized materials. Classic geopolymers (CGPs) activated with quicklime burst after one hour of molding. The results indicated slight amorphization of GP compared to raw MK, as confirmed by X-ray diffraction analysis, showing N(K)-A-S-H in CGP and N(K)-A-S-H with calcium silicate hydrate (C-S-H/C-A-S-H) in RUPG. The compressive strength of MK-based geopolymers reached 31.45 MPa and 34.92 MPa for GP and CGP, respectively, after 28 days of curing. Full article

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21 pages, 5451 KiB

Open AccessArticle

LPBF Processability of NiTiHf Alloys: Systematic Modeling and Single-Track Studies

by Hediyeh Dabbaghi, Mohammad Pourshams, Mohammadreza Nematollahi, Behrang Poorganji, Michael M. Kirka, Scott Smith, Chins Chinnasamy and Mohammad Elahinia

Materials 2024, 17(16), 4150; https://doi.org/10.3390/ma17164150 - 22 Aug 2024

Viewed by 844

Abstract

Research into the processability of NiTiHf high-temperature shape memory alloys (HTSMAs) via laser powder bed fusion (LPBF) is limited; nevertheless, these alloys show promise for applications in extreme environments. This study aims to address this limitation by investigating the printability of four NiTiHf [...] Read more.

Research into the processability of NiTiHf high-temperature shape memory alloys (HTSMAs) via laser powder bed fusion (LPBF) is limited; nevertheless, these alloys show promise for applications in extreme environments. This study aims to address this limitation by investigating the printability of four NiTiHf alloys with varying Hf content (1, 2, 15, and 20 at. %) to assess their suitability for LPBF applications. Solidification cracking is one of the main limiting factors in LPBF processes, which occurs during the final stage of solidification. To investigate the effect of alloy composition on printability, this study focuses on this defect via a combination of computational modeling and experimental validation. To this end, solidification cracking susceptibility is calculated as Kou’s index and Scheil–Gulliver model, implemented in Thermo-Calc/2022a software. An innovative powder-free experimental method through laser remelting was conducted on bare NiTiHf ingots to validate the parameter impacts of the LPBF process. The result is the processability window with no cracking likelihood under diverse LPBF conditions, including laser power and scan speed. This comprehensive investigation enhances our understanding of the processability challenges and opportunities for NiTiHf HTSMAs in advanced engineering applications. Full article

(This article belongs to the Special Issue State of the Art in Materials for Additive Manufacturing)

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14 pages, 3505 KiB

Open AccessArticle

Annealing Effect on Structural, Optical and Electrophysical Properties of ZnSe Nanocrystals Synthesized into SiO₂/Si Ion Track Template

by Aiman Akylbekova, Alma Dauletbekova, Zein Baimukhanov, Liudmila A. Vlasukova, Abay Usseinov, Nuray Saduova, Abdirash T. Akilbekov, Vladimir A. Pankratov and Anatoli I. Popov

Materials 2024, 17(16), 4149; https://doi.org/10.3390/ma17164149 - 22 Aug 2024

Cited by 1 | Viewed by 1216

Abstract

We report the results of synthesis of zinc selenide (ZnSe) nanocrystals into SiO₂/Si track templates formed by irradiation with 200 MeV Xe ions up to a fluence of 10⁷ ions/cm². Zinc selenide nanocrystals were obtained by chemical deposition [...] Read more.

We report the results of synthesis of zinc selenide (ZnSe) nanocrystals into SiO₂/Si track templates formed by irradiation with 200 MeV Xe ions up to a fluence of 10⁷ ions/cm². Zinc selenide nanocrystals were obtained by chemical deposition from the alkaline aqueous solution. Scanning electron microscopy, X-ray diffractometry, Raman and photoluminescence spectroscopy, and electrical measurements were used for characterization of synthesized ZnSe/SiO_2nanoporous/Si nanocomposites. XRD data for as-deposited precipitates revealed the formation of ZnSe nanocrystals with cubic crystal structure, spatial syngony F-43m (216). According to non-empirical calculations using GGA-PBE and HSE06 functionals, ZnSe crystal is a direct-zone crystal with a minimum bandgap width of 2.36 eV and anisotropic electronic distribution. It was found that a thermal treatment of synthesized nanocomposites at 800 °C results in an increase in ZnSe nanocrystallites size as well as an increase in emission intensity of created precipitates in a broad UV-VIS spectra range. However, vacuum conditions of annealing still do not completely prevent the oxidation of zinc selenide, and a formation of hexagonal ZnO phase is registered in the annealed samples. The current–voltage characteristics of the synthesized nanocomposites proved to have n-type conductivity, as well as increased conductivity after annealing. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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11 pages, 4618 KiB

Open AccessArticle

Modeling Study of Si₃N₄ Waveguides on a Sapphire Platform for Photonic Integration Applications

by Diandian Zhang, Shui-Qing Yu, Gregory J. Salamo, Richard A. Soref and Wei Du

Materials 2024, 17(16), 4148; https://doi.org/10.3390/ma17164148 - 22 Aug 2024

Cited by 2 | Viewed by 1043

Abstract

Sapphire has various applications in photonics due to its broadband transparency, high-contrast index, and chemical and physical stability. Photonics integration on the sapphire platform has been proposed, along with potentially high-performance lasers made of group III–V materials. In parallel with developing active devices [...] Read more.

Sapphire has various applications in photonics due to its broadband transparency, high-contrast index, and chemical and physical stability. Photonics integration on the sapphire platform has been proposed, along with potentially high-performance lasers made of group III–V materials. In parallel with developing active devices for photonics integration applications, in this work, silicon nitride optical waveguides on a sapphire substrate were analyzed using the commercial software Comsol Multiphysics in a spectral window of 800~2400 nm, covering the operating wavelengths of III–V lasers, which could be monolithically or hybridly integrated on the same substrate. A high confinement factor of ~90% near the single-mode limit was obtained, and a low bending loss of ~0.01 dB was effectively achieved with the bending radius reaching 90 μm, 70 μm, and 40 μm for wavelengths of 2000 nm, 1550 nm, and 850 nm, respectively. Furthermore, the use of a pedestal structure or a SiO₂ bottom cladding layer has shown potential to further reduce bending losses. The introduction of a SiO₂ bottom cladding layer effectively eliminates the influence of the substrate’s larger refractive index, resulting in further improvement in waveguide performance. The platform enables tightly built waveguides and small bending radii with high field confinement and low propagation losses, showcasing silicon nitride waveguides on sapphire as promising passive components for the development of high-performance and cost-effective PICs. Full article

(This article belongs to the Special Issue Thin Films, Nanostructures and Devices for Optoelectronics Applications)

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18 pages, 11327 KiB

Open AccessArticle

A Comparative Study on the Texture of Exposed Aggregate Concrete (EAC) Pavements Using Different Measurement Techniques

by Pawel Gierasimiuk, Marta Wasilewska and Wladyslaw Gardziejczyk

Materials 2024, 17(16), 4147; https://doi.org/10.3390/ma17164147 - 22 Aug 2024

Viewed by 649

Abstract

This paper presents issues related to the assessment of the texture of aggregate concrete (EAC) surfaces using various methods for its verification. Microtexture was assessed using the British Pendulum Tester (BPT) and Dynamic Friction Tester (DFT). Two laser profilometers were used to assess [...] Read more.

This paper presents issues related to the assessment of the texture of aggregate concrete (EAC) surfaces using various methods for its verification. Microtexture was assessed using the British Pendulum Tester (BPT) and Dynamic Friction Tester (DFT). Two laser profilometers were used to assess macrotexture, circular texture meter (CTM) and stationary laser profilograph (SPL), as well as the commonly known volumetric method. Measurements were carried out on left and right tracks and in between them on five test sections of expressways. Based on the analyses performed, it was found that the results obtained by the DFT were less sensitive to changes in microtexture between individual tracks compared to the results obtained by the BPT. The BPN values in the left track were lower than those in the right track. However, the difference between the DFT20 results in these spots was insignificant. Both MPD and MTD values did not show significant differences between the right and left tracks. However, some differences were observed between the MPD parameters obtained using the CTM and SPL. This resulted from the different frequency and length of the scanned surface profile. However, the differences were at an acceptable level. A very high linear correlation was obtained in the case of BPN and DFT20 values (r − 0.719), and in the case of MPD and MTD values, the correlation was almost certain (r above 0.900). Based on a comparative analysis of the models estimating mean texture depth (MTD/ETD), a significant difference was observed between models based on EAC pavement results and those based on asphalt surfaces. Full article

(This article belongs to the Special Issue Sustainable Pavement Materials: Design, Application and Performance Evaluation)

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13 pages, 2866 KiB

Open AccessArticle

Impact of Heat Treatment on the Structural, Optical, Magnetic and Photocatalytic Properties of Nickel Oxide Nanoparticles

by Gharam A. Alharshan, A. Almohammedi, M. A. M. Uosif, E. R. Shaaban and M. Emam-Ismail

Materials 2024, 17(16), 4146; https://doi.org/10.3390/ma17164146 - 22 Aug 2024

Viewed by 631

Abstract

The precursor nanoparticles of nickel hydroxide (Ni(OH)₂) and nickel oxide (NiO) were successfully converted into the latter by the reaction of nickel chloride with hydrazine at ambient temperature. (TGA) and (DSC) were adapted for annealing the precursor products at different annealing [...] Read more.

The precursor nanoparticles of nickel hydroxide (Ni(OH)₂) and nickel oxide (NiO) were successfully converted into the latter by the reaction of nickel chloride with hydrazine at ambient temperature. (TGA) and (DSC) were adapted for annealing the precursor products at different annealing temperatures (210, 285, 350, 390, 425, and 450 °C). XRD, TEM, and UV-VIS absorption spectroscopy were used to characterize the products. Both the band edge and energy gap values decrease with increasing annealing temperatures. Hysteresis loops are visible in the M-H curves of annealed (350 °C and 390 °C) precursor NiO NPs, indicating the presence of ferromagnetic Ni domains. However, NiO nanoparticles annealed at higher temperatures (425 °C and 450 °C) had a straight M-H curve, indicating paramagnetic properties. NiO NPs were used to study photocatalysis in the degradation of the MB dye. As annealing temperatures increased, the catalyst caused the degradation of MB. The sample that was annealed at 450 °C, however, exhibits the maximum photocatalytic activity, reaching up to 72.4% after being exposed to visible light. In other words, it was discovered that as the catalyst’s annealing temperature rose, so did the rate of MB’s photocatalytic degradation. Full article

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14 pages, 5033 KiB

Open AccessArticle

The Tribological Properties of Novel Sulfoximine Derivatives as Lubricant Additives

by Jianbin Zhang, Chaoyang Zhang, Yanhua Liu, Libang Feng, Wufang Yang, Xiaowei Pei and Qiangliang Yu

Materials 2024, 17(16), 4145; https://doi.org/10.3390/ma17164145 - 22 Aug 2024

Viewed by 665

Abstract

Introducing an additive is a practical approach to improve the lubrication performance of base oil in the field of tribology. Herein, a series of sulfoximine derivatives was synthesized and incorporated into base oil A51 as additives. The tribological properties of these lubricants were [...] Read more.

Introducing an additive is a practical approach to improve the lubrication performance of base oil in the field of tribology. Herein, a series of sulfoximine derivatives was synthesized and incorporated into base oil A51 as additives. The tribological properties of these lubricants were evaluated at both room and high temperatures, and the result demonstrated that they displayed excellent friction reduction and wear resistance in the friction process under both test conditions. Moreover, the chemical composition of the worn scar surface was inspected using EDS, XPS and TOF-SIMS to explore the lubricating mechanism. It is reasonable to conclude that the synergistic interaction between the aromatic ring scaffolds and elements like N, F, and S facilitated the adsorption of lubricant on the steel block surfaces and forming a tribofilm during the friction process. This tribofilm has a dominant impact on the system’s lubrication performance. This research provides novel oil-soluble lubricant additives, offering a facile approach to formulating high-quality lubricants. Full article

(This article belongs to the Section Thin Films and Interfaces)

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20 pages, 6496 KiB

Open AccessArticle

Critical Model Insight into Broadband Dielectric Properties of Neopentyl Glycol (NPG)

by Aleksandra Drozd-Rzoska, Jakub Kalabiński and Sylwester J. Rzoska

Materials 2024, 17(16), 4144; https://doi.org/10.3390/ma17164144 - 21 Aug 2024

Cited by 1 | Viewed by 1103

Abstract

This report presents the low-frequency (LF), static, and dynamic dielectric properties of neopentyl glycol (NPG), an orientationally disordered crystal (ODIC)-forming material important for the barocaloric effect applications. High-resolution tests were carried out for

173 K < T < 440 K

, in liquid, [...] Read more.

This report presents the low-frequency (LF), static, and dynamic dielectric properties of neopentyl glycol (NPG), an orientationally disordered crystal (ODIC)-forming material important for the barocaloric effect applications. High-resolution tests were carried out for

173 K < T < 440 K

, in liquid, ODIC, and solid crystal phases. The support of the innovative distortion-sensitive analysis revealed a set of novel characterizations important for NPG and any ODIC-forming material. First, the dielectric constant in the liquid and ODIC phase follows the Mossotti Catastrophe-like pattern, linked to the Clausius–Mossotti local field. It challenges the heuristic paradigm forbidding such behavior for dipolar liquid dielectrics. For DC electric conductivity, the prevalence of the ‘critical and activated’ scaling relation is evidenced. It indicates that commonly applied VFT scaling might have only an effective parameterization meaning. The discussion of dielectric behavior in the low-frequency (LF) domain is worth stressing. It is significant for applications but hardly discussed due to the cognitive gap, making an analysis puzzling. For the contribution to the real part of dielectric permittivity in the LF domain, associated with translational processes, exponential changes in the liquid phase and hyperbolic changes in the ODIC phase are evidenced. The novelty also constitutes

t g δ

temperature dependence, related to energy dissipation. The results presented also reveal the strong postfreezing/pre-melting-type effects on the solid crystal side of the strongly discontinuous ODIC–solid crystal transition. So far, such a phenomenon has been observed only for the liquid–solid crystal melting transition. The discussion of a possible universal picture of the behavior in the liquid phase of liquid crystalline materials and in the liquid and ODIC phases of NPG is particularly worth stressing. Full article

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20 pages, 12286 KiB

Open AccessArticle

Characterizing Short-Time Aging Precipitation Behavior of a Novel Nickel–Iron-Based Alloy via Electrical Performance

by Junjian Cai, Chengkai Qian, Xin Huo, Qu Liu, Kejian Li, Wen Ji, Zheng Li, Zhengang Yang, Jun Cheng, Manjie Fan and Zhipeng Cai

Materials 2024, 17(16), 4143; https://doi.org/10.3390/ma17164143 - 21 Aug 2024

Cited by 1 | Viewed by 989

Abstract

In this paper, the precipitation behavior and its effect on resistivity in a new type of nickel–iron-based alloy during short-term aging were investigated. During the aging process, the

γ^{'}

phase increases in average size and decreases in number, with its area fraction [...] Read more.

In this paper, the precipitation behavior and its effect on resistivity in a new type of nickel–iron-based alloy during short-term aging were investigated. During the aging process, the

γ^{'}

phase increases in average size and decreases in number, with its area fraction fluctuating over time. This fluctuation is caused by the mismatch in the redissolution and growth rates of the

γ^{'}

phase. As the area fraction of the

γ^{'}

phase increases, the content of solute atoms in the matrix that scatter electrons decreases, lowering the resistivity of the alloy. Additionally, the continuous precipitation of

M_{23} C_{6}

at grain boundaries during aging causes the resistivity to gradually increase. This paper explains the fluctuation in the total amount of

γ^{'}

phase during short-term aging and proposes a new method for characterizing the precipitation behavior of the

γ^{'}

phase in the novel alloy using the relative trend of resistivity changes. Full article

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19 pages, 12840 KiB

Open AccessArticle

Relationship between Texture, Hydrogen Content, Residual Stress and Corrosion Resistance of Electrodeposited Chromium Coating: Influence of Heat Treatment

by Jinghan Yang, Pengfei Ji, Xuemei Yang, Linyang Wu, Xiaoyun Ding, Jin Zhang, Yong Lian, Shitao Dou, Liming Jiang and Biliang Zhang

Materials 2024, 17(16), 4142; https://doi.org/10.3390/ma17164142 - 21 Aug 2024

Viewed by 682

Abstract

Electrodeposited chromium plating continues to be widely used in a number of specialized areas, such as weapons, transport, aerospace, etc. However, the formation of texture, hydrogen content and residual stress can degrade the serviceability and lead to material failure. The effect of post [...] Read more.

Electrodeposited chromium plating continues to be widely used in a number of specialized areas, such as weapons, transport, aerospace, etc. However, the formation of texture, hydrogen content and residual stress can degrade the serviceability and lead to material failure. The effect of post heat treatment processes on the relationship of texture, hydrogen content, residual stress and corrosion resistance of hexavalent [Cr(VI)] chromium coatings deposited on Cr–Ni–Mo–V steel substrates was investigated. Macrotexture was measured by XRD. Microtexture, dislocation density and grain size were studied by EBSD. With the increase of the heat treatment temperature, it was found that the fiber texture strength of the (222) plane tended to increase and subsequently decrease. Below 600 °C, the increase in the (222) plane texture carried a decrease in the hydrogen content, residual stress, microhardness and an increase in the corrosion resistance. In addition, crack density and texture strength were less affected by the heat treatment time. Notably, relatively fewer crack densities of 219/cm², a lower corrosion current density of 1.798 × 10⁻⁶ A/dm² and a higher microhardness of 865 HV were found under the preferred heat treatment temperature and time of 380 °C and 4 h, respectively. The hydrogen content and residual stress were 7.63 ppm and 61 MPa, with 86% and 75% reduction rates compared to the as-plated state, respectively. In conclusion, in our future judgement of the influence of heat treatment on coating properties, we can screen or determine to a certain extent whether the heat treatment process is reasonable or not by measuring only the macrotexture. Full article

(This article belongs to the Special Issue Metallic Materials: Structure Transition, Processing, Characterization and Applications (Second Edition))

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18 pages, 7843 KiB

Open AccessArticle

Effect of La on the Microstructures and Mechanical Properties of Al-5.4Cu-0.7Mg-0.6Ag Alloys

by Xiang Li, Anmin Li, Xiangdu Qin, Hailong Yang and Peng Cheng

Materials 2024, 17(16), 4141; https://doi.org/10.3390/ma17164141 - 21 Aug 2024

Viewed by 563

Abstract

The effects of the rare earth element La on the microstructure and mechanical properties of cast Al-5.4Cu-0.7Mg-0.6Ag alloys have been investigated through metallographic observation, scanning electron microscopy analysis, transmission electron microscopy, X-ray diffraction, and tensile testing. The present form and action mechanism of [...] Read more.

The effects of the rare earth element La on the microstructure and mechanical properties of cast Al-5.4Cu-0.7Mg-0.6Ag alloys have been investigated through metallographic observation, scanning electron microscopy analysis, transmission electron microscopy, X-ray diffraction, and tensile testing. The present form and action mechanism of La have been analyzed. The findings indicate that the inclusion of trace amounts of La markedly diminishes the grain size in the Al-Cu-Mg-Ag alloy. Furthermore, as the La content increases, the alloy’s strength is significantly improved. When the La concentration reaches 0.4 wt.%, the mechanical properties of the alloy, both at room temperature and at 350 °C, surpass those of the alloy lacking rare earth elements. When the added rare earth La content exceeds 0.2 wt.%, the emergence of the Al₆Cu₆La phase causes the alloy structure to exhibit a skeletal morphology, altering the morphology and distribution of excess second phases along grain boundaries, thereby impacting the alloy’s overall performance. Incorporating La leads to a reduction in the size of the strengthening precipitate phase Ω while also enhancing its precipitation density, but an excess of La leads to the emergence of Al₆Cu₆La, depleting the available Cu and suppressing the precipitation of the Ω phase, ultimately affecting the mechanical properties of the alloy. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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15 pages, 6460 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Properties of 3D-Printed Onyx–Fiberglass Composites

by Jong-Hwan Yun, Gun-Woong Yoon, Yu-Jae Jeon and Min-Soo Kang

Materials 2024, 17(16), 4140; https://doi.org/10.3390/ma17164140 - 21 Aug 2024

Viewed by 957

Abstract

This study evaluated the properties of 3D-printed Onyx–fiberglass composites. These composites were 3D-printed with zero, one, two, three, and four layers of fiberglass. Ten samples of each configuration were printed for the tensile and flexural tests. The average tensile strength of the Onyx [...] Read more.

This study evaluated the properties of 3D-printed Onyx–fiberglass composites. These composites were 3D-printed with zero, one, two, three, and four layers of fiberglass. Ten samples of each configuration were printed for the tensile and flexural tests. The average tensile strength of the Onyx specimens was calculated to be 44.79 MPa, which increased linearly by approximately 20–25 MPa with each additional fiberglass layer. The elastic moduli calculated from the micromechanics models were compared with the experimental values obtained from the tensile tests. The experimental elastic modulus increased more significantly than the model prediction when more fiberglass layers were added. The flexural modulus of Onyx was 17.6 GPa, which increased with each additional fiberglass layer. This quantitative analysis of composites fabricated using 3D printing highlights their potential for commercialization and industrial applications. Full article

(This article belongs to the Section Advanced Composites)

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13 pages, 5507 KiB

Open AccessArticle

Pseudo-Core-Shell Permalloy (Supermalloy)@ZnFe₂O₄ Powders and Spark Plasma Sintered Compacts Based on Mechanically Alloyed Powders

by Traian Florin Marinca, Loredana Cotojman, Florin Popa, Bogdan Viorel Neamțu, Călin-Virgiliu Prică and Ionel Chicinaș

Materials 2024, 17(16), 4139; https://doi.org/10.3390/ma17164139 - 21 Aug 2024

Viewed by 619

Abstract

Soft magnetic composite cores were produced by spark plasma sintering (SPS) from Ni₃Fe@ZnFe₂O₄ and NiFeMo@ZnFe₂O₄ pseudo-core-shell powders. In the Fe-Ni alloys@ZnFe₂O₄ pseudo-core-shell composite powders, the core is a large nanocrystalline Permalloy or [...] Read more.

Soft magnetic composite cores were produced by spark plasma sintering (SPS) from Ni₃Fe@ZnFe₂O₄ and NiFeMo@ZnFe₂O₄ pseudo-core-shell powders. In the Fe-Ni alloys@ZnFe₂O₄ pseudo-core-shell composite powders, the core is a large nanocrystalline Permalloy or Supermalloy particle obtained by mechanical alloying, and the shell is a pseudo continuous layer of Zn ferrite particles. The pseudo-core-shell powders have been compacted by SPS at temperatures between 500–700 °C, with a holding time of 0 min. Several techniques were used for the characterisation of the powders and sintered compacts: X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, magnetic hysteresis measurements (DC and AC), and electrical resistivity. The electrical resistivity is stabilised at values of about 7 × 10⁻³ Ω·m for sintering temperatures between 600–700 °C and this value is three orders of magnitude higher than the electrical resistivity of sintered Fe compacts. The best relative initial permeability was obtained for the Supermalloy/ZnFe₂O₄ composite compacts sintered at 600 °C, which decreases linearly for the entire frequency range studied, from around 95 to 50. At a frequency of 2000 Hz, the power losses are smaller than 1.5 W/kg. At a frequency of 10 kHz, the power losses are larger, but they remain at a reduced level. In the case of Supermalloy/ZnFe₂O₄ composite compact SPS-ed at 700 °C, the specific power losses are even lower than 5 W/kg. The power losses’ decomposition proved that intra-particle losses are the main type of losses. Full article

(This article belongs to the Special Issue Novel Materials Synthesis by Mechanical Alloying/Milling (Second Volume))

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20 pages, 10241 KiB

Open AccessArticle

Influence of SiO₂ Nanoparticles Extracted from Biomass on the Properties of Electrodeposited Ni Matrix Composite Films on Si(100) Substrate

by Ivana O. Mladenović, Nebojša D. Nikolić, Vladislav Jovanov, Željko M. Radovanović, Marko M. Obradov, Dana G. Vasiljević-Radović and Marija M. Vuksanović

Materials 2024, 17(16), 4138; https://doi.org/10.3390/ma17164138 - 21 Aug 2024

Viewed by 747

Abstract

Lab-made biosilica (SiO₂) nanoparticles were obtained from waste biomass (rice husks) and used as eco-friendly fillers in the production of nickel matrix composite films via the co-electrodeposition technique. The produced biosilica nanoparticles were characterized using XRD, FTIR, and FE-SEM/EDS. Amorphous nano-sized [...] Read more.

Lab-made biosilica (SiO₂) nanoparticles were obtained from waste biomass (rice husks) and used as eco-friendly fillers in the production of nickel matrix composite films via the co-electrodeposition technique. The produced biosilica nanoparticles were characterized using XRD, FTIR, and FE-SEM/EDS. Amorphous nano-sized biosilica particles with a high SiO₂ content were obtained. Various current regimes of electrodeposition, such as direct current (DC), pulsating current (PC), and reversing current (RC) regimes, were applied for the fabrication of Ni and Ni/SiO₂ films from a sulfamate electrolyte. Ni films electrodeposited with or without 1.0 wt.% biosilica nanoparticles in the electrolyte were characterized using FE-SEM/EDS (morphology/elemental analyses, roundness), AFM (roughness), Vickers microindentation (microhardness), and sheet resistance. Due to the incorporation of SiO₂ nanoparticles, the Ni/SiO₂ films were coarser than those obtained from the pure sulfamate electrolyte. The addition of SiO₂ to the sulfamate electrolyte also caused an increase in the roughness and electrical conductivity of the Ni films. The surface roughness values of the Ni/SiO₂ films were approximately 44.0%, 48.8%, and 68.3% larger than those obtained for the pure Ni films produced using the DC, PC, and RC regimes, respectively. The microhardness of the Ni and Ni/SiO₂ films was assessed using the Chen-Gao (C-G) composite hardness model, and it was shown that the obtained Ni/SiO₂ films had a higher hardness than the pure Ni films. Depending on the applied electrodeposition regime, the hardness of the Ni films increased from 29.1% for the Ni/SiO₂ films obtained using the PC regime to 95.5% for those obtained using the RC regime, reaching the maximal value of 6.880 GPa for the Ni/SiO₂ films produced using the RC regime. Full article

(This article belongs to the Special Issue The Microstructures and Advanced Functional Properties of Thin Films)

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15 pages, 3112 KiB

Open AccessArticle

Polyurethane Foam and Algae-Based Activated Carbon Biocomposites for Oil Spill Remediation

by Lokmane Abdelkaddous Baidar, Malika Medjahdi, Badra Mahida, Belaid Mechab and Dominique Baillis

Materials 2024, 17(16), 4137; https://doi.org/10.3390/ma17164137 - 21 Aug 2024

Viewed by 785

Abstract

This study investigates the incorporation of algae-based activated carbon into polyurethane foam to improve a biocomposite for gasoil sorption. The biocomposites were thoroughly analyzed using various techniques to examine the properties of both the blank foam and the algae activated carbon foam with [...] Read more.

This study investigates the incorporation of algae-based activated carbon into polyurethane foam to improve a biocomposite for gasoil sorption. The biocomposites were thoroughly analyzed using various techniques to examine the properties of both the blank foam and the algae activated carbon foam with a carbon content of 4.41 mass% and particle diameter of 500 µm. These techniques included Scanning Electron Microscopy (SEM), thermogravimetric analysis (TGA), and density analysis. The TGA analysis revealed that the biocomposites had an impact on the onset temperature (T_onset) of the foams. Higher concentrations of the biocomposites resulted in a decrease in T_onset from approximately 310 °C in the blank foam (PUF0) to 300 °C in the composite (PUF3B). The final residue percentage also decreased from around 20% in PUF0 to 10% in PUF3B. Density analysis showed that the apparent density of the foam increased from 0.016 g/cm³ in the blank foam to 0.020 g/cm³ in the biocomposite (PUF3B), while the real density slightly decreased from 0.092 g/cm³ to 0.076 g/cm³, indicating a reduction in overall porosity from 82.5% to 74.4%. All foams that were modified showed an increase in their ability to absorb gasoil in a PUF/gasoil/water system. The optimized biocomposite (PUF1B), with 1.14 mass% of 500 µm algae carbon, displayed the highest sorption capacity, starting at approximately 50 g/g at 1.5 h and increasing to 53 g/g over 72 h. The analysis of adsorption kinetics revealed that by utilizing adsorption isotherms, particularly the Langmuir isotherm, a more accurate fit to the data was achieved. This allowed for the prediction of the maximum gasoil adsorption capacity. This study aims to further develop, analyze, and utilize biocomposites made from algae-based activated carbon and polyurethane. These materials offer a sustainable and environmentally friendly approach to cleaning up oil spills. Full article

(This article belongs to the Special Issue Recent Advances in the Environmental Remediation Using Zeolites and Other Adsorbent Materials)

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