Effects of heat treatment on the microstructure of amorphous boron carbide coating deposited on graphite substrates by chemical vapor deposition

被引：19

作者：

Li, Siwei ^{[1
,2
]}

Zeng, Bin ^{[1
]}

Feng, Zude ^{[1
]}

Liu, Yongsheng ^{[2
]}

Yang, Wenbin ^{[2
]}

Cheng, Iaifei ^{[2
]}

Zhang, Litong ^{[2
]}

机构：

[1] Xiamen Univ, Coll Mat, Fujian Key Lab Adv Mat, Xiamen 361005, Peoples R China

[2] Northwestern Polytech Univ, Natl Key Lab Thermostruct Composite Mat, Xian 710072, Peoples R China

来源：

THIN SOLID FILMS | 2010年 / 519卷 / 01期

基金：

中国国家自然科学基金;

关键词：

Amorphous boron carbide; Annealing; Microstructure; Epitaxial growth; Chemical vapor deposition; SIC/SIC COMPOSITES; CARBON; GROWTH; MIXTURES; RANGE; PHASE;

D O I：

10.1016/j.tsf.2010.08.099

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

A two-layer boron carbide coating is deposited on a graphite substrate by chemical vapor deposition from a CH4/BCl3/H-2 precursor mixture at a low temperature of 950 degrees C and a reduced pressure of 10 KPa. Coated substrates are annealed at 1600 degrees C, 1700 degrees C, 1800 degrees C, 1900 degrees C and 2000 degrees C in high purity argon for 2 h, respectively. Structural evolution of the coatings is explored by electron microscopy and spectroscopy. Results demonstrate that the as-deposited coating is composed of pyrolytic carbon and amorphous boron carbide. A composition gradient of B and C is induced in each deposition. After annealing, B4C crystallites precipitate out of the amorphous boron carbide and grow to several hundreds nanometers by receiving B and C from boron-doped pyrolytic carbon. Energy-dispersive spectroscopy proves that the crystallization is controlled by element diffusion activated by high temperature annealing, after that a larger concentration gradient of B and C is induced in the coating. Quantified Raman spectrum identifies a graphitization enhancement of pyrolytic carbon. Transmission electron microscopy exhibits an epitaxial growth of B4C at layer/layer interface of the annealed coatings. Mechanism concerning the structural evolution on the basis of the experimental results is proposed. (C) 2010 Elsevier B.V. All rights reserved.

引用

页码：251 / 258

页数：8

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