Journal of Asian Ceramic Societies
·
2023
·
IF 2.3
Yangshuo Bai,Weixia Shen,Chao Fang,Liangchao Chen,Qianqian Wang,Biao Wan,Xiaopeng Jia,Yuewen Zhang,Zhuangfei Zhang
Ultra-high-temperature ceramics are required for many aerospace applications. In this work, HfB2-30 vol.% HfC and HfB2-26 vol.% HfC-43 vol.% MoB high-density composites were prepared by one-step in-situ reactive spark plasma sintering (R-SPS) using Hf, B4C and Mo powders as starting materials. The influences of sintering temperature on the densification mechanism, microstructural evolution, mechanical properties and oxidation resistance of the composites were thoroughly investigated. The results demonstrate that the raw materials undergo a complete chemical reaction to form new binary HfB2-HfC and ternary HfB2-HfC-MoB composite structures at a temperature of 1300°C. The HfB2-HfC and HfB2-HfC-MoB composites prepared at the optimal conditions (pressure = 50 MPa, temperature = 1800°C, holding time = 5 min) had highre densities of 97% and 98%, respectively. The Vickers hardness, Young’s modulus and fracture toughness of the HfB2-HfC composite were 18.3 GPa, 525 GPa and 6.34 MPa·m1/2, respectively. However, after molybdenum was added, the Vickers hardness of the ternary HfB2-HfC-MoB composite increased to 19.4 GPa but its fracture toughness decreased slightly to 6.1 MPa·m1/2. Compared with the binary composite, the ternary composite exhibited a low and thermally stable oxidation rate up to a temperature of 1400°C, and the test was conducted in air atmosphere.
研究领域:
材料科学
·
航空航天工程
·
陶瓷
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CHEMICAL AND ENGINEERING DATA
·
2019
·
IF 2.298
Yibo Fang,Zanjun Gao,Kangli Bao,Jiongliang Huang,Xiaosheng Ji,Xiaohong Han,Guangming Chen
The working pairs of HFCs + organic absorption solvents are commonly used in absorption systems. In this work, the vapor–liquid equilibrium (VLE) data of HFC-32 + DMETrEG at (293.15–343.15) K and HFC-32 + NMP at (323.15–343.15) K were measured in a dual cycle apparatus. The VLE data were correlated by Antione-type equation, NRTL, and PR + MHV1 + NRTL model, respectively. The predicted VLE data showed a good agreement with the experimental VLE data. NRTL model was recommended to predict the VLE data and characteristic of solution for HFC-32 + DMETrEG and HFC-32 + NMP, compared to PR + MHV1 + NRTL model. The comparison of VLE characteristics for five binary mixtures (HFC-32 + DMETrEG, HFC-32 + NMP, HFC-32 + DMF, HFC-32 + DMAC, and HFC-32 + DMEDEG) was carried out. The compared results showed that the system pressures of HFC-32 + DMETrEG and HFC-32 + NMP were lower than other three mixtures, and the negative deviations from Raoult’s law of HFC-32 + DMETrEG and HFC-32 + NMP were larger than the others, which indicated that the two mixtures were more suitable as the working fluids for absorption system.
研究领域:
化学工程
·
热力学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CHEMICAL AND ENGINEERING DATA
·
2016
·
IF 1.835
Xiaohong Han,Zhangzhang Yang,Zanjun Gao,Wenjie Guan,Guangming Chen
Fluoroethane (HFC-161) is one of the most promising alternative refrigerants because of its excellent environmental and thermodynamic properties. It was considered as one of the most promising absorption working fluids in the absorption refrigeration. To make a better application of the refrigerant in absorption refrigeration systems, suitable absorbents should be selected for matching HFC-161. Vapor–liquid equilibrium (VLE) data is the key of the chemical engineering simulation and the refrigeration cycle calculation. On the basis of these, the vapor–liquid equilibrium data for the mixture of HFC-161 + dimethyl ether triethylene glycol were obtained at temperatures from 293.15 to 353.15 K by using a recirculation apparatus. The VLE data were then correlated by the Peng−Robinson (PR) equation of state combined with the modified Huron-Vidal first order (MHV1) mixing rule and nonrandom two liquid (NRTL) model. The experimental results had a good consistency with calculated values. Phase behaviors of HFC-161 combined with different absorbents were compared in this paper.
研究领域:
化学工程
·
制冷技术
✓ 已验证
产品关联
DOI
高影响因子
Open Ceramics
·
2023
·
IF 0
Zhaoju Yu,Zhenyue Wang,Xichao Dong,Jia Sun,Xingang Luan,Ralf Riedel
Liquid polymeric precursors have found wide applications as a matrix source for continuous fiber reinforced ceramic matrix composites (CMCs) because of their excellent fluidity and high ceramic yield. In the present study, a processable liquid single-source-precursor was synthesized using allylhydropolycarbosilane (AHPCS) and low-cost hafnium tetrachloride (HfCl 4 ) as raw materials to form final SiC-HfC-C nanocomposites by well-known polymer-derived ceramic (PDC) approach. The precursor synthesis, thermal behavior, polymer-to-ceramic transformation and ceramic phase evolution were investigated by FT-IR, TGA, XRD and TEM. The TGA results show that the obtained single-source-precursor exhibits very high ceramic yields of over 80.0 wt% after heat treated at 1400 °C. After annealing at 1600 °C, the resultant SiC-HfC-C nanocomposites contain SiC@C and HfC@C nanoparticles with SiC and HfC as cores and amorphous carbon as shells. The present single-source-precursor is candidate material for CMC applications due to its liquidity and high ceramic yield.
研究领域:
材料科学
·
陶瓷材料
✓ 已验证
DOI
CHEMICAL PHYSICS LETTERS
·
2023
·
IF 2.8
Wujian Zhang,Xiangdong Zhou,Hui Sun,Zhenxiang Li,Kangjun Wang,Panpan Zhang,Wenfeng Han,Ying Li,Haodong Tang
The activated alumina with different specific surface areas and different acidity was used to catalyze the dehydrofluorination reaction of CF 3 CH 2 F (HFC-134a). The catalytic performance of the alumina catalysts was rationalized by analyzing the relationship between specific surface area and acidity before and after fluorination. A series of physiochemical techniques, including Scanning Electron Microscope (SEM), X-ray diffraction (XRD), and N 2 physical adsorption (BET), were used to investigate the changes in catalyst structure and surface morphology before and after being tested for the dehydrofluorination reaction. The Al 2 O 3 catalyst prepared from the precipitation method (Al 2 O 3 -P) demonstrated the best stability among all the Al 2 O 3 catalysts. Results from XRD techniques showed that Al 2 O 3 catalysts were fully or partially fluorinated into AlF 3 after the dehydrofluorination reaction. Al 2 O 3 -B catalyst and Al 2 O 3 -S catalyst containing mainly α-AlF 3 deactivate easier than the Al 2 O 3 -P catalyst, which has primarily β-AlF 3 . In addition, it can be concluded the high surface area Al 2 O 3 -P catalyst still has the highest specific surface area and pore size when fluorinated to AlF 3 , while forming the β-AlF 3 crystalline phase. Therefore, it has the optimum catalytic performance for dehydrofluorination of HFC-134a. This provides a new idea for designing alumina catalysts with reasonable structure.
研究领域:
化学工程
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2023
·
IF 5.7
Junjie Xu,Wei Sun,Xiang Xiong,Hongbo Zhang,Lingkun Yang
To improve the ablation resistance of carbon fibre (Cf), alleviate the interdiffusion between Cf and the matrix, and improve the complex preparation process of double-layer carbide coating, a high-quality SiC-HfC double interpenetrating coating was prepared on the surface of Cf using a molten salt synthesis (MSS) method. The microstructure, formation mechanism, and ablation behaviour of the coating were studied. The results show that the coating is composed of interpenetrating HfC and SiC phases. The interpenetrating structure was formed due to the transport of Hf ions into the interior of porous SiC nanowires facilitated by the molten salt medium, followed by diffusion through carbon. The SiC-HfC double-layer interpenetrating coating can serve as an oxygen barrier to protect Cf from oxidative damage under extreme temperature (2000 °C) and aerobic environment (oxyacetylene flame).
研究领域:
材料科学
·
表面工程
✓ 已验证
产品关联
DOI
高影响因子
WEAR
·
2024
·
IF 5.3
Jiangling Luo,Xiaofan Ma,Xianhang Huang,Yi Cao,Linlin Pan,Xiaodong Zou,Jianglong Yi,Lianyi Shao
The study involved plasma arc transfer welding (PTAW) for preparing coatings of Inconel 625 alloys that contained different amounts of nano-sized hafnium carbide (nano-HfC) particles. The impact of nano-HfC on the microstructure evolution and mechanical properties of PTAWed Inconel 625 were investigated. The research reveals that nano-HfC decomposes during the high-temperature plasma arc process and then react with O element to generate nano-HfO 2 . These HfO 2 can serve as nucleation sites for MC carbides, which restricts the growth of secondary dendrite arms, leading to a more disordered grain growth direction. Simultaneously, the decomposition of HfC can increase the C/Nb ratio of the matrix, effectively suppressing Laves phase formation while encouraging the development of MC carbides. Compared with IN625, the wear rate of composites at room temperature and 600 °C were decreased. Notably, at 600 °C, the wear rate of the coating with 0.5 wt% HfC is the lowest among all the samples, as reflected by a noteworthy reduction in wear rate of 50 %. This is mainly attributed to the refinement of γ matrix, reduction of Laves phase as well as precipitation of the fine-sized MC carbides. This work illustrates that adding nano-HfC is an effective way to improve the wear resistance of the PTAWed Inconel 625.
研究领域:
材料科学
·
焊接工程
·
表面工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2023
·
IF 3.9
Zhe Zhao,Cheng Han,Xiaozhou Wang,Yingde Wang
Metallopolymers containing refractory metal in the main chain are highly desired but rarely reported as oxygen-free single-source precursors for preparing ultrahigh-temperature ceramics. Herein, a novel single-source precursor of poly-hafnium-borocarbosilane (PHBCNS) with an Hf–N–B backbone molecular structure was synthesized through the dehalogenation reaction between HfCl 4 and B(NHCH 3 ) 3 . The polymeric Hf–N–B chain with large bond angle and conjugated molecular structure endowed the PHBCNS precursor to be relatively stable, dissolvable, and meltable. Subsequent precursor pyrolysis up to 1800°C resulted in an HfC/HfB 2 nanocomposite comprising an Hf content of 87.54 wt%, with the average grain size of HfC and HfB2 to be 34.9 and 74.1 nm, respectively. The ceramization mechanism and phase evolution from the PHBCNS precursor to HfC/HfB 2 composite ceramics were thoroughly investigated. This work not only highlights a novel Hf–N–B backbone polymer with high metal content and good shaping properties but also provides fresh insights of designing single-source precursors for ultrahigh-temperature composite ceramics.
研究领域:
材料科学
·
无机化学
✓ 已验证
产品关联
DOI
高影响因子
International Journal of Applied Ceramic Technology
·
2023
·Vol. 20
·期 3
·1646-1657
·
IF 2.1
Lu Fu,Shifeng Wen,Wanbo Hou,Xinhao Shi,Tao Feng,Mingde Tong
2D-C/HfC–SiC composites were prepared by a combination of precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI). Creep tests were performed at 1100°C in air under different stress conditions. Unlike most, C/SiC and SiC/SiC ceramic matrix composites only underwent primary and secondary creep stages, and the C/HfC–SiC composites underwent tertiary creep stage in the creep process. The reason was that the mechanical properties of C/HfC–SiC materials prepared by PIP + CVI methods were different from those prepared by traditional methods. The microscopic morphological analysis of the sample fracture showed that the oxidation products SiO 2 and Hf–Si–O glass phases of the HfC–SiC matrix played a crack filling role in the sample during creep. In turn, it provided effective protection to the internal fibers of the sample. The creep failure of C/HfC–SiC composites in a high-temperature oxidizing atmosphere was caused by the oxidation of the fibers. The total creep process was dominated by the oxidation of carbon fibers. It is noteworthy that there was the generation of Hf x Si y O z nanowires in the samples after high-temperature creep. The analysis of the experimental data showed that the creep stress had a linear negative correlation with the creep life.
研究领域:
材料科学
·
力学
✓ 已验证
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2017
·
IF 2.986
Jun Cheng,Jun Wang,Xiaozhou Wang,Hao Wang
A novel precursor was synthesized by reacting hafnium chloride with dicyandiamide and dimethylformamide. The precursor was characterized via FT-IR and NMR , as well as TG. Subsequently, the precursor was annealed in Ar over a range of temperatures from 1000 °C to 2000 °C, and the microstructural evolution of the ceramics was investigated by XRD , XPS , and TEM. The results show that the carbothermal reduction of the precursor starts at 1150 °C and the ceramic yields at 1500 °C reach 44.6 wt%. The obtained powders exhibit a uniform distribution and are composed of N-doped HfC and graphite. The N-doped structure postponed the oxidation of the HfC(N) ceramics. The HfC(N) ceramics were first oxidized to yield HfO 2 , carbon, and nitrogen, and then the carbon was oxidized with the evolution of CO 2 . The presented synthesis method is believed to be applicable to the preparation of other high-performance ceramics.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2018
·
IF 3.779
Jun Cheng,Xiaozhou Wang,Jun Wang,Hao Wang,Shengxuan Hu
Precursors with different nitrogen contents were synthesised using hafnium (IV) chloride (HfCl 4 ), dicyandiamide (DICY) and triethylamine (Et 3 N) as raw materials and were used for preparing Hf-based nanocomposites. The synthesis, ceramic conversion and microstructural evolution of HfC-based nanocomposites derived from precursors with different nitrogen contents were investigated. The results indicate that the composition of the synthesised precursors can be controlled by adjusting the molar ratio of HfCl 4 and dicyandiamide. Pyrolysis of the precursors at 1200 °C led to the formation of Hf 2 CN or HfN-based ceramics. As the nitrogen content of the synthesised precursors increased, the Hf 2 CN crystallites present in the ceramics annealed at 1200 °C gradually transformed to HfN. Furthermore, at 1600 °C, the HfN and Hf 2 CN phases gradually converted to HfC(N). The results also indicate that nitrogen favours the sintering of the obtained nanocomposites. The HfC-based ceramics should be promising for application as high-performance composite 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
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2020
·
IF 4.495
Youlin Jiang,Dewei Ni,Bowen Chen,Jun Lu,Feiyan Cai,Xuegang Zou,Chunjing Liao,Hongda Wang,Shaoming Dong
In this work, 3D-C f /HfC-SiC-based composites were fabricated and optimized via reactive melt infiltration (RMI) of Si into porous C f /HfC-C preforms prepared by a sol-gel processing. The physical and chemical processes involved during the fabrication were identified and analyzed in details. It is revealed that fibers and interphase of the composites can be eroded during carbothermal reduction process, which can be further aggravated during RMI, with the formation of Hf-containing substance on the fibers surface. The fibers and interphase degradation is mainly induced by the reactions between HfO 2 and C/SiC interphase layers at elevated temperatures. Accordingly, a two-step carbothermal reduction treatment was proposed for the optimization of the fabrication procedure. As a result, less fiber/interphase erosion and improved mechanical properties are achieved in the composites, with the bending strength increased by ∼49 % (from 214.1 ± 15.7 MPa to 319.0 ± 26.0 MPa).
研究领域:
材料科学
·
复合材料制备
✓ 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）