Small Structures
·
2022
·Vol. 4
·期 1
·2200161
·
IF 11.343
Lu Chen,Youbing Li,Ke Chen,Xiaojing Bai,Mian Li,Shiyu Du,Zhifang Chai,Qing Huang
Entropy stabilization is an effective method to design and explore MAX phases with outstanding properties via tuning constituent elements and crystal structures, which have received considerable critical attention. Currently, some medium-/high-entropy (ME/HE) MAX phases, whose A layers are composed of Al, S, and magnetic elements, are reported, while few discussions about ME/HE-MAX phases with other A elements (e.g., Sn) are conducted. Herein, fully dense ME/HE-MAX phase bulks ((TiVNb) 2 SnC, (TiVNbZr) 2 SnC, and (TiVNbZrHf) 2 SnC) are designed and synthesized because of the chemical diversity of MAX phases. The results of Rietveld refinement of X-ray diffraction, scanning electron microscopy, and high-resolution scanning transmission electron microscopy-affiliated energy-dispersive spectrometer analysis comprehensively verify the crystal structure of ME/HE-MAX phases. Both the electrical conductivity and the charge carrier mobility are significantly lower than the reported correlation ternary MAX phases, due to the electron scattering and structural defects in ME/HE-MAX phase crystal structures. Similarly, the electron contribution of thermal conductivity is gradually declining; on the contrary, the phonon plays an increasingly dominant role as temperature increases. Owing to the richness in composition of MAX phases, herein, a composition design route for discovering new MAX phases and tuning their properties is indicated.
研究领域:
材料科学
·
凝聚态物理
✓ 已验证
产品关联
DOI
高影响因子
TRANSACTIONS OF THE INDIAN INSTITUTE OF METALS
·
2025
·Vol. 78
·期 4
·1-11
·
IF 1.6
Chen Qijie,Liu Chencheng,Han Jiaxin,Cheng Yong,Chen Qingyun,Xiong Zhonggang
A new high-entropy MAX phase (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 W 0.2 ) 2 AlC was successfully synthesized at 1500 ℃ by nonpressure sintering one-step solid phase reaction method. The microstructure, crystal structure and oxidation behavior of high-entropy (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 W 0.2 ) 2 AlC MAX phase were investigated. Using thermogravimetry analysis to investigate the oxidative stability of (V 0.2 Nb 0.2 Ta 0.2 Mo 0.2 W 0.2 ) 2 AlC in air environment at high temperature from 0 to 1000 °C, there is no volume change from 0 to 400 °C, and the morphology still exhibits a typical layered structure, demonstrating thermal stability. Oxidation rate gradually decreases with the increase in temperature, and the K p3 value decreases to 0.86 × 10 –4 kg 2 m −4 s 2 at 1000 ℃. The microscopic morphology analysis at different temperatures shows that the surface defects of the matrix gradually form under high-temperature conditions, in which the formation of carbide and Al 2 O 3 layers hinds the further oxidation of the sample. The research provides a reference for the synthesis and thermal stability of new two-dimensional layered high-entropy MAX ceramics.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2025
·
IF 5.6
Shuaiqian Wang,Baoji Miao,Muhammad Shahid Nadeem,Huaizhi He,Yao Zhao,Muhammad Yasir,Qiuling Chen,Guoqin Liu,Jinbo Bai
This study successfully prepared a novel high-entropy MAX phase (Ti 1/4 V 1/4 Zr 1/4 Nb 1/4 ) 2 AlC and conducted a comprehensive investigation of its microwave absorption performance. The material was synthesized using a pressure less sintering method, and by optimizing the selection of raw materials and synthesis processes, high purity, and excellent microwave absorption performance were achieved. The composition, structure, morphology, and electromagnetic parameters of the material were analyzed in detail using characterization methods such as XRD, SEM, EDS, TEM, XPS, and vector network analyzer (VNA). Experimental results exhibit that (Ti 1/4 V 1/4 Zr 1/4 Nb 1/4 ) 2 AlC can achieve a lowest RL of -62.56 dB at a thickness of 2.25 mm with frequency of 13.26 GHz, demonstrating outstanding microwave absorption capabilities. The study also explored the microwave absorption mechanisms of grown material, including conductivity, dipole polarization relaxation processes, internal lattice defects, and magnetic loss. This research not only delivers new approaches and development of effective microwave absorption materials but also lays the foundation for subsequent studies on MXene and more multi-element high-entropy MAX phase 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 MATERIALS SCIENCE & TECHNOLOGY
·
2022
·
IF 10.319
Linjing Qiao,Jianqiang Bi,Guandong Liang,Chen Liu,Zhuangzhuang Yin,Yao Yang,Hongyi Wang,Shaoyin Wang,Mengmeng Shang,Weili Wang
Herein, a novel kind of high-entropy MAX phases, (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders were successfully synthesized by a newly proposed two-step solid state reaction process. The oxidation experiments demonstrate that the oxidation products of Al 2 Mo 3 O 12 and rutile TiO 2 are formed at about 600 and 800 °C, respectively. Besides, the dielectric and electromagnetic (EM) wave absorption properties of (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders and those after oxidation at different temperatures were also examined. The results show that the as-synthesized (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders possess excellent EM wave absorption performances with the minimum reflection loss ( RL ) of -45.80 dB (at 1.7 mm thickness) and the maximum effective absorption bandwidth ( E AB ) of 3.6 GHz (at 1.5 mm thickness). After oxidation at 400–800 °C, due to the coupling of conductivity loss and polarization loss, (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders can retain good EM wave absorption properties in a certain frequency range. In this paper, the effects of oxidation on EM wave absorption properties of high-entropy MAX phases were systematically investigated for the first time. This work manifests that high-entropy MAX phases are promising EM wave absorbing candidates and can maintain good EM wave absorption performances after oxidation.
研究领域:
材料科学
·
电磁学
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）