MATERIALS LETTERS
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2024
·
IF 2.7
Tiane Su,Dandan Ma,Min Zhu
The present study reports the first synthesis of a high-entropy (Fe 0.2 Co 0.2 Cu 0.2 Zn 0.2 Mn 0.2 )Nb 2 O 6 ceramics with the Pbcn single-phase columbite structure. Microstructure analysis using TEM + EDS and XRD techniques confirms the presence of a single-phase structure, demonstrating successful integration of multi-component cations into the same site. Additionally, experimental studies on the electrical and thermal properties of the sample are presented in this study. Notably, this material exhibits excellent thermal insulation ability, as evidenced by its relatively low intrinsic thermal conductivity values of 0.75 and 1.39 W·m −1 ·K −1 at 323 K and 1023 K, respectively.
研究领域:
材料科学
·
物理学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2022
·Vol. 106
·期 2
·841-847
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IF 4.186
Lei Han,Yu Chen,Haijun Zhang,Guangqiang Li,Quanli Jia,Shaowei Zhang
High-entropy transition-metal (IVB–VIB) carbide (HETMC) ceramics consisting of multiple principal components generally correspond to higher configuration entropy, and exhibit better overall performance. However, they also present certain synthesis challenges, for example, in the synthesis of a three-dimensional six-principal-component HETMC aerogel. In the present work, as an example a novel (Ti 0.167 Cr 0.167 V 0.167 Mo 0.167 Nb 0.167 Ta 0.167 )C aerogel was prepared at a relatively low temperature of 1773 K by an in-situ carbothermal reduction/partial sintering technique following the successful preparation of (Ti 0.2 V 0.2 Mo 0.2 Nb 0.2 Ta 0.2 )C and (Ti 0.2 Cr 0.2 Mo 0.2 Nb 0.2 Ta 0.2 )C five-principal-component HETMC aerogels. The synthesized 6-HETMC aerogel exhibited a homogeneous microstructure with grain phases and pores of 100–300 nm and 0.2–10 μm, respectively, a density of 0.45 g cm −3 , a high porosity and compressive strength of 94.5% and 0.8 MPa, respectively, a low thermal conductivity of 0.128 W (m K) −1 at 298 K, and a good high-temperature stability at least up to 1673 K in Ar. This research provided a novel strategy for future development of HETMC ceramic aerogels for high-temperature applications.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2024
·
IF 5.2
Yanyan He,Tao Chen,Yanyu Pan,Minzhong Huang,Kaixian Wang,Liyan Xue,Yazhu Li,Fengzhi Tan,Fan Yang,Tongkuan Xu,Heng Chen
Perovskite-type rare-earth ferrites (REFeO 3 ) are promising materials for absorbing electromagnetic (EM) wave pollution. However, insufficient dielectric loss and poor impedance matching are key factors that limit the broader implementation of REFeO 3 . Herein, a series of multicomponent perovskite-type ferrites with strong EM wave absorption capabilities was prepared. Through the synergistic effect of chemical constitution regulation and entropy regulation, optimization of the dielectric loss and impedance matching is achieved by strengthening the structural defect mechanism, thus further adjusting the EM wave absorption performance. Compared with (LaGdSmNdBa)FeO 3 (HE-1) and (LaGdPrSmNdBa)FeO 3 (HE-2), (LaGdBa)FeO 3 (ME-1) and (LaGdSmBa)FeO 3 (ME-2) exhibit favorable performance, with optimal minimum reflection loss (RL min ) of −56.35 dB (at 11.12 GHz) and −63.25 dB (at 7.22 GHz) and effective absorption bandwidth (EAB) of 4.46 and 4.72 GHz, respectively. This multicomponent design provides a new strategy for the development of EM wave absorption materials.
研究领域:
材料科学
·
电磁学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
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2022
·
IF 6.364
Qiang Gao,Cheng Han,Xiaozhou Wang,Yingde Wang
Polymeric precursors with refractory metal in the main chain while still possess meltable/soluble characteristics are highly desired for ultra-high temperature ceramics (UHTCs). Herein, we proposed a stepwise synthesis of polyzirconosilane (PZCS) with Zr-C-Si-N polymeric chain. The reaction mechanism was discussed based on the frontier molecular orbital theory and atom transfer radical polymerization , which was initiated and propagated by a low oxidation state active specie of Cp 2 Zr(II). The PZCS precursor has excellent soluble and meltable properties with a softening point of 80.8 ~ 89.2 o C, which could be spun into green fibers by melt spinning technique. The ceramization process of PZCS was studied, and the resulted SiZrNC multinary ceramics were composed of ZrC/SiC nanocrystals embedded by graphitized carbon phase. The excellent mouldable properties, oxygen-free compositions and high Zr content of PZCS make it an ideal precursor for the preparation of UHTCs matrixes and fibers.
研究领域:
材料科学
·
化学
✓ 已验证
DOI
高影响因子
POWDER METALLURGY AND METAL CERAMICS
·
2021
·Vol. 59
·期 11
·651-660
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IF 0.511
Zhangjun Bai,Yuhong Chen,Lu Li,Jiaxin Li,Yuewei Cheng
In this study, Ta–W–Ti–Al multialloys were prepared by spark plasma sintering (SPS) as a new powder metallurgy technology based on discharge activation and thermoplastic deformation process. The oxidation behavior of the as-obtained sintered alloys were investigated under 1000 and 1200°C in air atmosphere. Microstructures and phase compositions of alloys and oxides were analyzed using various analytical methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and backscatter electron microscopy (BSE). The sintered samples possessed relative densities reaching up to 98% with achievable densification. The densities of all specimens with high Ti contents exceeded 100%, suggesting the great impact of Ti addition on liquid-phase precipitation. Intermetallic compounds were formed in Ta–W–Al alloys, and samples with high Ti contents displayed grain boundary phases rich in titanium and oxygen. The addition of Ti and Al effectively improved the oxidation resistance of the resulting alloys. A protective alumina layer was formed after oxidation at 1000°C that made oxidation kinetics of the alloys obeying pseudo-parabolic laws. At the oxidation temperature of 1200°C, Al 2 O 3 reacted with Ta 2 O 5 to form the AlTaO 4 alloy with reduced protective effect. The mass gain in the alloys after oxidation at 1200°C for 4 h was about 7 times higher compared to processing at 1000°C.
研究领域:
材料科学
·
冶金工程
✓ 已验证
DOI
高影响因子
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