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Search Results (340)

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Keywords = high-pressure sintering

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17 pages, 1522 KiB  
Article
Characterization of Solid Particulates to Be Used as Storage as Well as Heat Transfer Medium in Concentrated Solar Power Systems
by Rageh Saeed, Syed Noman Danish, Shaker Alaqel, Nader S. Saleh, Eldwin Djajadiwinata, Hany Al-Ansary, Abdelrahman El-Leathy, Abdulelah Alswaiyd, Zeyad Al-Suhaibani, Zeyad Almutairi and Sheldon Jeter
Appl. Sci. 2025, 15(15), 8566; https://doi.org/10.3390/app15158566 (registering DOI) - 1 Aug 2025
Viewed by 113
Abstract
Using solid particulates as a heat transfer medium for concentrated solar power (CSP) systems has many advantages, positioning them as a superior option compared with conventional heat transfer media such as steam, oil, air, and molten salt. However, a critical imperative lies in [...] Read more.
Using solid particulates as a heat transfer medium for concentrated solar power (CSP) systems has many advantages, positioning them as a superior option compared with conventional heat transfer media such as steam, oil, air, and molten salt. However, a critical imperative lies in the comprehensive evaluation of the properties of potential solid particulates intended for utilization under such extreme thermal conditions. This paper undertakes an exhaustive examination of both ambient and high-temperature thermophysical properties of four naturally occurring particulate materials, Riyadh white sand, Riyadh red sand, Saudi olivine sand, and US olivine sand, and one well-known engineered particulate material. The parameters under scrutiny encompass loose bulk density, tapped bulk density, real density, sintering temperature, and thermal conductivity. The results reveal that the theoretical density decreases with the increase in temperature. The bulk density of solid particulates depends strongly on the particulate size distribution, as well as on the compaction. The tapped bulk density was found to be larger than the loose density for all particulates, as expected. The sintering test proved that Riyadh white sand is sintered at the highest temperature and pressure, 1300 °C and 50 MPa, respectively. US olivine sand was solidified at 800 °C and melted at higher temperatures. This proves that US olivine sand is not suitable to be used as a thermal energy storage and heat transfer medium in high-temperature particle-based CSP systems. The experimental results of thermal diffusivity/conductivity reveal that, for all particulates, both properties decrease with the increase in temperature, and results up to 475.5 °C are reported. Full article
(This article belongs to the Section Applied Thermal Engineering)
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13 pages, 8060 KiB  
Article
Microstructural, Mechanical, and Thermal Properties of Textured Si3N4/BN Composite Ceramics Prepared Using Two-Step Sintering
by Dexiang Gong, Yi Zhou, Yunwei Shi and Qianglong He
Materials 2025, 18(15), 3573; https://doi.org/10.3390/ma18153573 - 30 Jul 2025
Viewed by 223
Abstract
Textured Si3N4/BN composite ceramics were successfully fabricated using two-step sintering, combining pseudo-hot isostatic pressing (PHIP) and gas pressure sintering. The grain size of h-BN platelets had a significant influence on densification and mechanical and thermal properties. With an increase [...] Read more.
Textured Si3N4/BN composite ceramics were successfully fabricated using two-step sintering, combining pseudo-hot isostatic pressing (PHIP) and gas pressure sintering. The grain size of h-BN platelets had a significant influence on densification and mechanical and thermal properties. With an increase in h-BN grain size, the volume density of the composite ceramics gradually decreased, while flexural strength gradually increased. Meanwhile, larger h-BN platelets were more likely to trigger toughening mechanisms like large-angle deflection and greatly increase fracture toughness. Through proper selection of h-BN grain size, textured ceramics, with the addition of h-BN platelets of 1–2 μm, showed high thermal conductivity (∼92 W∙m−1∙K−1) and reliable mechanical properties (∼540 MPa, ∼7.5 MPa∙m1/2, ∼11.1 GPa). Therefore, texture control is an effective means of improving the overall performance of ceramic materials. Novel textured composite ceramics thus have great potential in large-scale fabrication and directional heat dissipation applications. Full article
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14 pages, 1452 KiB  
Review
Recent Advances in Liquid Metal-Based Stretchable and Conductive Composites for Wearable Sensor Applications
by Boo Young Kim, Wan Yusmawati Wan Yusoff, Paolo Matteini, Peter Baumli and Byungil Hwang
Biosensors 2025, 15(7), 466; https://doi.org/10.3390/bios15070466 - 19 Jul 2025
Viewed by 503
Abstract
Liquid metals (LMs), with their unique combination of high electrical conductivity and mechanical deformability, have emerged as promising materials for stretchable electronics and biointerfaces. However, the practical application of bulk LMs in wearable sensors has been hindered by processing challenges and low stability. [...] Read more.
Liquid metals (LMs), with their unique combination of high electrical conductivity and mechanical deformability, have emerged as promising materials for stretchable electronics and biointerfaces. However, the practical application of bulk LMs in wearable sensors has been hindered by processing challenges and low stability. To overcome these limitations, liquid metal particles (LMPs) encapsulated by native oxide shells have gained attention as versatile and stable fillers for stretchable and conductive composites. Recent advances have focused on the development of LM-based hybrid composites that combine LMPs with metal, carbon, or polymeric fillers. These systems offer enhanced electrical and mechanical properties and can form conductive networks without the need for additional sintering processes. They also impart composites with multiple functions such as self-healing, electromagnetic interference shielding, and recyclability. Hence, the present review summarizes the fabrication methods and functional properties of LM-based composites, with a particular focus on their applications in wearable sensing. In addition, recent developments in the use of LM composites for physical motion monitoring (e.g., strain and pressure sensing) and electrophysiological signal recording (e.g., EMG and ECG) are presented, and the key challenges and opportunities for next-generation wearable platforms are discussed. Full article
(This article belongs to the Special Issue The Application of Biomaterials in Electronics and Biosensors)
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8 pages, 720 KiB  
Article
Microscopic Characterization of Pb10−xCux(PO4)6O by 31P and 63/65Cu NMR Measurements
by Qing-Ping Ding, Yue Sun, Qiang Hou, Wei Wei, Xin Zhou, Xinyue Wang, Zhixiang Shi and Yuji Furukawa
J. Compos. Sci. 2025, 9(7), 377; https://doi.org/10.3390/jcs9070377 - 18 Jul 2025
Viewed by 801
Abstract
The report of the first room-temperature, ambient-pressure superconductivity in copper-doped lead apatite Pb10−xCux(PO4)6O has attracted lots of attention. However, subsequent studies revealed the presence of numerous impurity phases in the polycrystalline sample, and the [...] Read more.
The report of the first room-temperature, ambient-pressure superconductivity in copper-doped lead apatite Pb10−xCux(PO4)6O has attracted lots of attention. However, subsequent studies revealed the presence of numerous impurity phases in the polycrystalline sample, and the sharp superconducting-like transition is not due to a superconducting transition but most likely due to a reduction in resistivity caused by the first-order structural phase transition of Cu2S at around 385 K from the β phase at high temperature to the γ phase at low temperature. Before now, only bulk measurements have been performed on a Pb10−xCux(PO4)6O powder sample, which could be affected by the impurity phases, masking the intrinsic properties of Pb10−xCux(PO4)6O. In this study, 31P and 63/65Cu nuclear magnetic resonance (NMR) measurements have been performed on a Pb10−xCux(PO4)6O powder sample to investigate its physical properties from a microscopic point of view. Our NMR data evidence the non-magnetic insulating nature of Pb10−xCux(PO4)6O without any trace of electron correlation effects. Furthermore, the 63/65Cu NMR results suggest that no copper or very little copper is substituted for Pb in Pb10(PO4)6O prepared by sintering Pb2SO5 and Cu3P. Full article
(This article belongs to the Special Issue Optical–Electric–Magnetic Multifunctional Composite Materials)
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16 pages, 8362 KiB  
Article
Analysis of Selected Spark Plasma Sintering Parameters on the Mechanical Properties of Sintered X30Cr13 Steel
by Anna Kulakowska, Teresa Bajor and Anna Kawalek
Materials 2025, 18(13), 3084; https://doi.org/10.3390/ma18133084 - 29 Jun 2025
Viewed by 371
Abstract
This paper presents the possibilities of using the reaction sintering method for the production of tool steel used in medicine. The applied method enables the sintering of powders in one technological process. The SPS (spark plasma sintering) process is a technology in which [...] Read more.
This paper presents the possibilities of using the reaction sintering method for the production of tool steel used in medicine. The applied method enables the sintering of powders in one technological process. The SPS (spark plasma sintering) process is a technology in which electric pulses generate heat and pressure, which allows for the quick and effective connection of powder particles into a homogeneous material with high density and good mechanical properties. As a result, a product of small dimensions and a precisely defined chemical composition, established at the stage of preparing the powder mixture, is obtained. The advantages of the applied production process are the sintering time and small amounts of post-production waste compared to conventional methods of producing a finished product from steel. The method of producing a semi-finished product is particularly useful in the case of small-scale and small-sized production. The subject of the research was the analysis of the conditions for obtaining X30Cr13 martensitic steel used for the production of surgical instruments. This paper analyzes the effect of sintering temperature and time on sinterability and on selected physical and mechanical properties of the obtained materials. The sintering parameters of the starting mixture have been optimized to obtain the highest possible sinter properties, such as density and hardness. Based on the analysis of the results, it was found that the powder preparation method for the SPS process and the grain size significantly affect the microstructure and mechanical properties of the final product. The optimal sintering parameters for X30Cr13 steel are a temperature of 950 °C and a sintering time of 12 min. Furthermore, the use of the SPS method allows for a reduction in the manufacturing costs of martensitic steel semi-finished products. Full article
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17 pages, 5119 KiB  
Article
Anode-Supported SOFCs with a Bi2O3-Doped NiO–ScSZ Anode and ScSZ Electrolyte: Low-Temperature Co-Sintering and High Performance
by Shang Peng, Zhao Liu, Pairuzha Xiaokaiti, Tiancheng Fang, Jiwei Wang, Guoqing Guan and Abuliti Abudula
ChemEngineering 2025, 9(4), 66; https://doi.org/10.3390/chemengineering9040066 - 24 Jun 2025
Viewed by 391
Abstract
In this study, a novel anode-supported solid oxide fuel cell (SOFC) comprising a Bi2O3-doped NiO-ScSZ anode and an ScSZ electrolyte was successfully fabricated via a low-temperature co-sintering process at 1300 °C. The incorporation of 3 wt% Bi2O [...] Read more.
In this study, a novel anode-supported solid oxide fuel cell (SOFC) comprising a Bi2O3-doped NiO-ScSZ anode and an ScSZ electrolyte was successfully fabricated via a low-temperature co-sintering process at 1300 °C. The incorporation of 3 wt% Bi2O3 effectively promoted the sintering of both the anode support and electrolyte layer, resulting in a dense, gas-tight electrolyte and a mechanically robust porous anode support. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the formation of phase-pure, highly crystalline ScSZ with an optimized microstructure. Electrochemical performance measurements demonstrated that the fabricated cells achieved excellent power density, reaching a peak value of 0.861 W cm−2 at 800 °C under humidified hydrogen fuel conditions. The cells maintained stable performance under dry methane operation, with a maximum power density of 0.624 W cm−2 at 800 °C, indicating resistance to carbon deposition. Gas chromatographic analyses further revealed that the Bi2O3-doped NiO-ScSZ anode facilitated earlier and more stable electrochemical oxidation of methane-derived species compared with the conventional NiO-YSZ system, even under conditions of an elevated methane partial pressure. These findings demonstrate that Bi2O3 co-doping, combined with low-temperature co-sintering, provides an effective approach for fabricating high-performance intermediate-temperature SOFCs with enhanced structural integrity and electrochemical stability. The developed methodology presents a promising pathway toward achieving cost-effective and durable SOFC technologies. Full article
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9 pages, 15356 KiB  
Article
Fabrication and Properties of ITTO Segments for Cylindrical Targets by Pressureless Oxygen Atmosphere Sintering Method
by Jiwen Xu, Fangzhou Wu, Yuan Yao, Ling Yang, Guisheng Zhu and Huarui Xu
Ceramics 2025, 8(2), 75; https://doi.org/10.3390/ceramics8020075 - 18 Jun 2025
Viewed by 343
Abstract
Cylindrical targets have a high utilization rate, but are difficult to manufacture. A large hollow ITTO segment with thin walls was prepared by cold isostatic pressure and two-stage sintering. The fabrication process yielded a segment with an outer diameter of 153 mm, an [...] Read more.
Cylindrical targets have a high utilization rate, but are difficult to manufacture. A large hollow ITTO segment with thin walls was prepared by cold isostatic pressure and two-stage sintering. The fabrication process yielded a segment with an outer diameter of 153 mm, an inner diameter of 135 mm, and a length of 700 mm, indicating a length to thickness ratio of up to 78. The dense and uniform green bodies ensure the achievement of high density and uniformity of the sintered body throughout its volume. The segment exhibited a high relative density of about 99.5% and a low resistivity of below 3.4 × 10−4 Ω·cm. The density and resistivity illustrate a minimal inhomogeneity along the length of the segment. The segment exhibits a cubic bixbyite phase and is characterized by densely packed fine grains with an average size of several microns. Therefore, these results establish a substantial foundation for the large-scale production of cylindrical ITTO segments. Full article
(This article belongs to the Special Issue Advances in Electronic Ceramics, 2nd Edition)
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24 pages, 7719 KiB  
Article
All-Ceramic Fiber Fabry–Perot Cavity High-Temperature Pulsating Pressure Sensor Based on HTCC
by Xiangcong Xu, Fei Wang, Guoqing Han, Huiyi Tang, Wanfeng Zhou, Xiaohua Lei and Xianming Liu
Sensors 2025, 25(12), 3678; https://doi.org/10.3390/s25123678 - 12 Jun 2025
Viewed by 557
Abstract
In the aerospace, energy and nuclear energy sectors, dynamic pressure measurement of power equipment and pressure vessels in high-temperature environments is critical for validating design, manufacturing processes and operational condition monitoring. The existing electric sensors are resistant to temperature. It is difficult to [...] Read more.
In the aerospace, energy and nuclear energy sectors, dynamic pressure measurement of power equipment and pressure vessels in high-temperature environments is critical for validating design, manufacturing processes and operational condition monitoring. The existing electric sensors are resistant to temperature. It is difficult to meet the pressure measurement requirements of high temperature and high-frequency responses. In this paper, combining the material properties of high-temperature co-fired ceramics (HTCC) with the structural characteristics of Fabry–Perot, an all-ceramic fiber-optic Fabry–Perot high-temperature pulsating pressure sensor based on a HTCC pressure- sensing diaphragm and ceramic high-temperature sintering process, is proposed. Experimental results show that in the pressure range of 6 MPa, the static pressure sensitivity of the sensor is 1.30 nm/MPa, and the linear goodness of fit reaches 0.99913. The dynamic response frequency of the sensor reaches 598.5 kHz. The survival time at high temperature of 800 °C is more than 80 h. The sensitivity to temperature is 0.00475 nm/°C. Full article
(This article belongs to the Special Issue Advances in Optical Fiber-Based Sensors)
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12 pages, 26078 KiB  
Article
The Effect of Mg Content on the Microstructure and Open Porosity of a Porous FeAl Intermetallic Compound
by Weilun Xue, Zhuoxuan Liu, Dongming Liu and Zhigang Xu
Metals 2025, 15(6), 628; https://doi.org/10.3390/met15060628 - 31 May 2025
Viewed by 341
Abstract
In this study, a porous FeAl intermetallic compound with high porosity was synthesized via vacuum sintering using Mg powder as a pore-forming agent, leveraging its high saturated vapor pressure and almost non-reactivity with Fe. The influence of the addition of Mg powder on [...] Read more.
In this study, a porous FeAl intermetallic compound with high porosity was synthesized via vacuum sintering using Mg powder as a pore-forming agent, leveraging its high saturated vapor pressure and almost non-reactivity with Fe. The influence of the addition of Mg powder on pore characteristics and microstructure evolution was systematically investigated. The results indicate that variations in Mg content within sintered compacts exhibit a negligible impact on primary phase composition, with the FeAl phase remaining predominant. However, excessive initial Mg content induces the encapsulation of the FeAl phase by minor Fe2Al5 and Al3Mg2 phases, compromising the phase’s purity. The porosity positively correlates with Mg content, and porous material with a porosity of 72.8% is obtained (40 at.% of Mg as an additive). Moreover, the pore structure manifests as an interconnected hole morphology. These findings provide valuable insights for further exploration of the design of porous FeAl material and its performance enhancement in emerging applications. Full article
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7 pages, 2085 KiB  
Brief Report
Preparation of High-Purity Silicon Carbide Ceramics by Hot Pressing Sintering
by Chang Zou, Yifan Xiao, Lixia Li, Jiagang Chen, Wei Sun and Xingzhong Guo
Nanomaterials 2025, 15(11), 825; https://doi.org/10.3390/nano15110825 - 29 May 2025
Viewed by 507
Abstract
Wafer carriers, as one of the key components in semiconductor manufacturing processes, have strict purity requirements. In this work, high-strength and high-purity SiC ceramics were fabricated using hot pressing sintering (HPS) combined with particle gradation. After hot pressing sintering with the addition of [...] Read more.
Wafer carriers, as one of the key components in semiconductor manufacturing processes, have strict purity requirements. In this work, high-strength and high-purity SiC ceramics were fabricated using hot pressing sintering (HPS) combined with particle gradation. After hot pressing sintering with the addition of 15 wt% nano-SiC, a sintering temperature of 2200 °C, and a pressure of 40 MPa, the resultant SiC ceramics demonstrated excellent comprehensive properties with a high purity of 99.967%, a flexural strength of 458.71 MPa, a Vickers hardness of 23.31 GPa, and a fracture toughness of 4.06 MPa·m1/2. The high-strength and high-purity SiC ceramics show potential to function as wafer carrier materials in semiconductor manufacturing processes. Full article
(This article belongs to the Section Nanocomposite Materials)
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23 pages, 4984 KiB  
Review
Leaching of Scheelite Concentrate for Tungsten Extraction
by Xinran Li, Hao Jiang, Zhiwei Peng, Anan Duan, Tong Zhang and Zexi Gong
Minerals 2025, 15(5), 475; https://doi.org/10.3390/min15050475 - 30 Apr 2025
Cited by 1 | Viewed by 694
Abstract
As a critical raw material, tungsten plays a broad role in machining, electronics, aerospace, and other high-tech industries. The extraction of tungsten from tungsten concentrates is a prerequisite for the production of high-purity products. Approximately 70% of China’s tungsten resources are in the [...] Read more.
As a critical raw material, tungsten plays a broad role in machining, electronics, aerospace, and other high-tech industries. The extraction of tungsten from tungsten concentrates is a prerequisite for the production of high-purity products. Approximately 70% of China’s tungsten resources are in the form of scheelite. The extraction method of low-quality scheelite is crucial for the production application of the tungsten process as resources of high-quality wolframite are gradually being depleted. This article systematically reviews the processes and challenges faced in the hydrometallurgical process of scheelite concentrates and provides useful insights. Typical leaching processes for scheelite concentrate have shown excellent leaching efficiencies, with tungsten trioxide (WO3) recoveries exceeding 90%. Alkaline leaching processes are promising, but temperature and pressure are crucial for this method. The sintering–leaching process is energy-consuming and costly. Meanwhile, leaching with hydrochloric acid (HCl) or sulfuric acid (H2SO4) often results in the formation of tungstic acid (H2WO4) on the mineral surface, which inhibits further leaching and leads to a low extraction rate. In contrast, the mixed-acid leaching method is more promising, with recovery close to 100%, a short process, and low-cost, and the acid leaching solution is recyclable. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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33 pages, 4942 KiB  
Article
Improved Oil/Water Separation by Employing Packed-Bed Filtration of Modified Quartz Particles
by Nthabiseng Ramanamane and Mothibeli Pita
Water 2025, 17(9), 1339; https://doi.org/10.3390/w17091339 - 29 Apr 2025
Viewed by 758
Abstract
This study explores the development and optimization of quartz-based filtration media for industrial oil–water separation, focusing on enhancing surface wettability, minimizing fouling, and improving oil rejection efficiency. High-purity quartz particles (SiO2: 98%, Fe2O3: 0.18%, particle size: 0.8–1.8 [...] Read more.
This study explores the development and optimization of quartz-based filtration media for industrial oil–water separation, focusing on enhancing surface wettability, minimizing fouling, and improving oil rejection efficiency. High-purity quartz particles (SiO2: 98%, Fe2O3: 0.18%, particle size: 0.8–1.8 mm) were evaluated in three configurations: raw, acid-washed, and surface-coated with hydrophilic nanoparticles (Al2O3 and P2O5). The filtration medium was constructed as a packed-bed of quartz particles rather than a continuous sintered membrane, providing a cost-effective and modular structure for separation processes. Comprehensive material characterization was performed using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). XRD confirmed the crystalline stability of quartz across all treatments, while SEM and EDS revealed enhanced surface morphology and elemental distribution—especially phosphorus and aluminum—in coated samples. Performance testing with synthetic oily wastewater (initial oil concentration: 183,754.8 mg/L) demonstrated that the coated quartz medium achieved superior separation, reducing residual oil concentration to 29.3 mg/L, compared to 1583.7 mg/L and 1859.8 mg/L for washed and raw quartz, respectively. Contact angle analysis confirmed improved hydrophilicity in coated media, which also exhibited lower fouling propensity. Taguchi optimization (conducted via Minitab 21.3) and regression modeling identified surface coating and operational pressure (optimal at 2.5 bar) as the most significant parameters influencing oil rejection. Post-filtration SEM and XRD confirmed structural integrity and coating durability. Additionally, flux recovery above 90% after backwashing indicated strong regeneration capability. These findings validate surface-modified quartz packed beds as robust, scalable, and economically viable alternatives to conventional membranes in oily wastewater treatment. Future research will explore multilayer coatings, long term performance under aggressive conditions, and AI-based prediction models. Full article
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14 pages, 7415 KiB  
Article
Enhancing Thermal Conductivity of SiC Matrix Pellets for Accident-Tolerant Fuel via Atomic Layer Deposition of Al2O3 Coating
by Yumeng Zhao, Wenqing Wang, Jiquan Wang, Xiao Liu, Yu Li, Zongshu Li, Rong Chen and Wei Liu
Energies 2025, 18(8), 2130; https://doi.org/10.3390/en18082130 - 21 Apr 2025
Viewed by 396
Abstract
This study investigates the enhancement of thermal conductivity in silicon carbide (SiC) matrix pellets for accident-tolerant fuels via atomic layer deposition (ALD) of alumina (Al2O3) coatings. Pressure-holding ALD protocols ensured precursor saturation, enabling precise coating control (0.09 nm/cycle). The [...] Read more.
This study investigates the enhancement of thermal conductivity in silicon carbide (SiC) matrix pellets for accident-tolerant fuels via atomic layer deposition (ALD) of alumina (Al2O3) coatings. Pressure-holding ALD protocols ensured precursor saturation, enabling precise coating control (0.09 nm/cycle). The ALD-coated Al2O3 layers on SiC particles were found to be more uniform while minimizing surface oxidation compared to traditional mechanical mixing. Combined with yttria (Y2O3) additives and spark plasma sintering (SPS), ALD-coated samples achieved satisfactory densification and thermal performance. Results demonstrated that 5~7 wt.% ALD-Al2O3 + Y2O3 achieved corrected thermal conductivity enhancements of 14~18% at 100 °C., even with reduced sintering aid content, while maintaining sintered densities above 92% T.D. (theoretical density). This work highlights ALD’s potential in fabricating high-performance, accident-tolerant SiC-based fuels for safer and more efficient nuclear reactors, with implications for future optimization of sintering processes and additive formulations. Full article
(This article belongs to the Section B4: Nuclear Energy)
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14 pages, 12032 KiB  
Article
Fabrication of Stainless Steel/Alumina Composite Powders by Spray Granulation and Plasma Spheroidization
by Elodie Cabrol, Sandrine Cottrino, Hocine Si-Mohand and Gilbert Fantozzi
Materials 2025, 18(8), 1872; https://doi.org/10.3390/ma18081872 - 19 Apr 2025
Viewed by 419
Abstract
This work presents a new approach for the fabrication of 316L/Al2O3 composites, based on a combination of spray granulation, radio frequency (RF) plasma spheroidization and spark plasma sintering (SPS). Initially, a suspension containing 316L and alumina powders is formulated by [...] Read more.
This work presents a new approach for the fabrication of 316L/Al2O3 composites, based on a combination of spray granulation, radio frequency (RF) plasma spheroidization and spark plasma sintering (SPS). Initially, a suspension containing 316L and alumina powders is formulated by precisely adjusting the pH and selecting an appropriate dispersant, thereby ensuring homogeneous dispersion of the constituents. The spray granulation process then produces granules with controlled size and morphology. RF plasma spheroidization, carried out using a TekSphero-40 system, is investigated by varying parameters such as the power, gas flow rates, injection position and feed rate, in order to optimize the formation of spherical and dense particles. The analysis reveals a marked sensitivity to heat transfer from the plasma to the particles, with a tendency for fine particles to segregate, which underscores the necessity for precise control of the processing conditions. Finally, SPS densification, performed under a constant pressure and a rigorously controlled thermal cycle, yields composites with excellent density and hardness characteristics. This study thus demonstrates that the proposed hybrid process offers an optimal synergy between a uniform distribution of alumina and a controlled microstructure, opening up promising avenues for the design of high-performance composite materials for demanding applications. Full article
(This article belongs to the Section Metals and Alloys)
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20 pages, 11102 KiB  
Article
Liquid Phase Sintering of Al Powder Using Al-X (X=Cu, Ca, Mg) Eutectic Alloy Powders: Effect of Alloy Elements and Oxide Film Thickness
by Ryotaro Kusunoki, Hideaki Hayashi, Erika Matsumoto, Asuka Suzuki, Naoki Takata, Makoto Kobashi, Akira Yoshida, Takahiro Hamada and Moe Mekata
Materials 2025, 18(8), 1755; https://doi.org/10.3390/ma18081755 - 11 Apr 2025
Viewed by 540
Abstract
Sinter-based additive manufacturing (AM) requires sintering for the densification of green bodies. Al powder is difficult to sinter due to the dense oxide film on the surface, and it is difficult to apply to sinter-based AM. Liquid phase sintering using Al-based eutectic alloy [...] Read more.
Sinter-based additive manufacturing (AM) requires sintering for the densification of green bodies. Al powder is difficult to sinter due to the dense oxide film on the surface, and it is difficult to apply to sinter-based AM. Liquid phase sintering using Al-based eutectic alloy powder is promising for sintering Al powder without external pressure. In this study, Al powders with various oxide film thicknesses were sintered using Al-X eutectic alloy powders (X=Cu, Ca, and Mg) to clarify suitable alloy elements in the sintering aids for the liquid phase sintering. When an as-supplied Al powder with an oxide film thickness of approximately 2 nm (presumably amorphous Al2O3 film) was used, Al-Cu and Al-Ca aids promoted the densification, whereas numerous pores were observed in the sample sintered using Al-Mg aid. The pores would be formed during the cooling after sintering, along with the homogenization of Mg distribution. When Al powder with an oxide film thickness of around 4 nm was used, a high relative density of over 95% was maintained using Al-Cu aid, whereas the relative density of the sample sintered using Al-Ca aid significantly degraded, presumably due to the formation of Ca-based oxide. These results indicate that the Al-Cu eutectic alloy powder is a promising sintering aid for the liquid phase sintering of Al powder. Full article
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