Materials
·
2023
·Vol. 16
·期 12
·4426
·
IF 3.4
Guang Zeng,Ping Xu,Chen Zeng,Qizhong Huang,Zhean Su
HfCxN1−xnanoparticles were synthesized using the urea-glass route, employing hafnium chloride, urea, and methanol as raw materials. The synthesis process, polymer-to-ceramic conversion, microstructure, and phase evolution of HfCxN1−x/C nanoparticles were thoroughly investigated across a wide range of molar ratios between the nitrogen source and the hafnium source. Upon annealing at 1600 °C, all precursors demonstrated remarkable translatability to HfCxN1−xceramics. Under high nitrogen source ratios, the precursor exhibited complete transformation into HfCxN1−xnanoparticles at 1200 °C, with no observed presence of oxidation phases. In comparison to HfO2, the carbothermal reaction of HfN with C significantly reduced the preparation temperature required for HfC. By increasing the urea content in the precursor, the carbon content of the pyrolyzed products increased, leading to a substantial decrease in the electrical conductivity of HfCxN1−x/C nanoparticle powders. Notably, as the urea content in the precursor increased, a significant decrease in average electrical conductivity values was observed for the R4-1600, R8-1600, R12-1600, and R16-1600 nanoparticles measured at a pressure of 18 MPa, yielding values of 225.5, 59.1, 44.8, and 46.0 S·cm−1, respectively.Keywords:HfCxN1−x;pyrolysis;ultra-high-temperature ceramics;nanoparticles
研究领域:
材料科学
·
无机化学
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DOI
PubMed
高影响因子
CERAMICS INTERNATIONAL
·
2022
·Vol. 48
·期 16
·22967-22974
·
IF 5.532
Guang Zeng,Ping Xu,Chen Zeng,Cunqian Fang,Yafeng Wang,Xin Yang,Mingyu Zhang,Zhean Su,Qizhong Huang
A novel single-source precursor was synthesized to prepare HfC x N 1-x /SiC multiphase ceramics by using hafnium chloride (HfCl 4 ), diallylamine (DAA) and polycarbosilane (PCS). We conducted an investigation of the synthesis process, polymer-to-ceramic conversion, as well as the microstructure and phase evolution of HfC x N 1-x /SiC multiphase ceramics with different levels of SiC content. The results showed that the core-shell particles of HfC x N 1-x -carbon were embedded homogeneously in the β-SiC matrix which is beneficial for preventing grain growth and improving oxidation resistance . Based on data from oxidation tests, the ceramics improved the oxidation temperature and remained stable at a high temperature (1500 °C) with oxidation layer formation on the surface. Due to the highly cross-linked structure without oxygen, high ceramic yield, homogeneous composition and excellent oxidation resistance of the pyrolysis product, the as-prepared precursor is a promising material for making high-performance composite ceramics.
研究领域:
材料科学
·
陶瓷与复合材料
·
聚合物衍生陶瓷
·
高温材料
·
无机合成
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DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
·
2026
·
IF 16.8
Xue Li,Wei Li,Yanqin Fu,Jianhua Zhang,Sen Yang,Zifeng Hu,Junhao Zhao,Yongbo Cao,Jian Zhang,Yulei Zhang
The laser ablation mechanism of PDC-SPS HfC x N 1 − x ceramics was clarified. • At 39.8 MW m –2 heat flux, HfC 0.75 N 0.25 shows superior ablation resistance. • Dislocations, lath-like structures and dense Hf(C,N,O) layers stabilize ablation. Hafnium carbonitride (HfC x N 1− x ) ceramics show great potential for thermal protection systems due to their ultra-high melting point, and investigating their ablation behavior is essential for their application under extreme conditions. In this work, HfC x N 1− x ceramics with varying nitrogen contents were synthesized via polymer-derived ceramic followed by spark plasma sintering. Laser ablation tests showed that HfC 0.75 N 0.25 achieved excellent ablation resistance under the laser power of 500 W, with linear and mass ablation rates of 1.08 µm s −1 and 0.32 mg s −1 , respectively. This is ascribed to the high melting point and exceptional thermal stability of HfC 0.75 N 0.25 , which result from moderate nitrogen incorporation. During laser ablation, dislocation accumulation and the formation of lath-like structures dissipate part of the laser heat flux. Subsequently, a dense Hf(C, N, O) solid solution layer with high viscosity forms, which effectively impedes oxygen diffusion and maintains stable ablation resistance of HfC 0.75 N 0.25 . Conversely, excessive nitrogen incorporation induces the formation of the Hf 7 O 8 N 4 phase with numerous defects and crack nucleation, ultimately deteriorating laser ablation resistance. These findings provide useful insights for the design and development of ultra-high temperature ceramics for applications in extreme environments. Download: Download high-res image (277KB) Download: Download full-size image
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高影响因子
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