首页|Initial precursor reaction mechanism of CVD-HfC coating based on density functional theory

Initial precursor reaction mechanism of CVD-HfC coating based on density functional theory

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Recently,the preparation of ultra-high temperature HfC ceramic coating has gained sig-nificant attention,particularly through the application of the HfCl4-CH4-H2-Ar system via Chem-ical Vapor Deposition(CVD),which has been found widely applied to C/C composites.Herein,an analysis of the reactions that occur in the initial stage of the CVD-HfC coating process is presented using Density Functional Theory(DFT)and Transition State Theory(TST)at the B3LYP/Lan-l2DZ level.The results reveal that HfCl4 can only cleave to produce hypochlorite,which will further react with methyl to synthesize intermediates to form HfC.According to the analysis of the energy barrier and reaction constant,HfCl preferentially reacts with methyl groups to form complex adsorptive intermediates at 1573 K.With a C-Hf bond production energy of 212.8 kcal/mol(1 kcal=4.18 kJ),the reaction rate constant of HfCl+CH is calculated to be 2.15 × 10-18 cm3/s at 1573 K.Additionally,both the simulation and experimental results exhibit that the upward trend of reaction rate constants with temperature is also consistent with the deposition rate,indi-cating that the growth curve of the reaction rate constants tends to flatten out.The proposed reac-tion model of the precursor's decomposition and reconstruction during deposition process has significant implication for the process guidance.

Carbon compositeHfC coatingChemical vapor depositionDensity functional theoryPrecursor reaction mechanism

Yunzhou LIN、Yulei ZHANG、Yanqin FU、Jian ZHANG、Jing'an KONG、Ruicong CHEN

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State Key Laboratory of Solidification Processing,Carbon/Carbon Composites Research Center,Northwestern Polytechnical University,Xi'an 710072,China

Henan Key Laboratory of High Performance Carbon Fiber Reinforced Composites,Carbon Matrix Composites Research Institute,Henan Academy of Sciences,Zhengzhou 450046,China

National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Key Research and Development Program of ChinaND Basic Research Funds of Northwestern Polytechnical University,China

52293373521302052021YFA0715803G2022WD

2024

10.1016/j.cja.2024.05.005

中国航空学报(英文版)
中国航空学会

中国航空学报(英文版)

CSTPCDEI
影响因子：0.847
ISSN：1000-9361
年,卷(期)：2024.37(7)
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