Effects of oxidation treatment on properties of SiO_(2f)/SiO_2-BN composites  

作　　者：LI Duan ZHANG Chang-rui LI Bin CAO Feng WANG Si-qing YANG Bei LIU Kun 李端;张长瑞;李斌;曹峰;王思青;杨备;刘坤(State Key Laboratory of Advanced Ceramic Fibers&Composites,College of Aerospace&Materials Engineering,National University of Defense Technology,Changsha 410073,China)

机构地区：[1]State Key Laboratory of Advanced Ceramic Fibers&Composites,College of Aerospace&Materials Engineering,National University of Defense Technology,Changsha 410073,China

出　　处：《Journal of Central South University》2012年第1期30-35,共6页中南大学学报（英文版）

基　　金：Projects(50902150,90916019) supported by the National Natural Science Foundation of China;Project (9140C8203040905) supported by the State Key Laboratory Foundation of China;Project(S100103) supported by the Graduate Innovation Foundation of National University of Defense Technology,China

摘　　要：The silica fiber reinforced silica and boron nitride-based composites （SiO2f/SiO2-BN） were prepared firstly via the sol-gel method and then the urea route, and the effects of oxidation treatment on the component, structure, mechanical and dielectric properties of the composites were investigated. The results show that the oxidation treatment at 450 ℃ will not impair the structure of boron nitride, and carbon is the main impurity with the excessive urea. The density of SiO2f/SiO2-BN composites is 1.81 g/cm3, and the flexural strength and elastic modulus are 113.9 MPa and 36.5 GPa, respectively. After oxidation treatment, the density varies to 1.80 g/cm3, and the flexural strength and elastic modulus are decreased to 58.9 MPa and 9.4 GPa, respectively. The mechanical properties of the composites are severely damaged, but they still exhibit a good toughness. The composites show excellent dielectric properties with the dielectric constant and loss tangent being 3.22 and 0.003 9, respectively, which indicates that the oxidation treatment is ineffective to improve the dielectric properties of SiOzf/SiO2-BN composites.The silica fiber reinforced silica and boron nitride-based composites(SiO2f/SiO2-BN) were prepared firstly via the sol-gel method and then the urea route,and the effects of oxidation treatment on the component,structure,mechanical and dielectric properties of the composites were investigated.The results show that the oxidation treatment at 450 °C will not impair the structure of boron nitride,and carbon is the main impurity with the excessive urea.The density of SiO2f/SiO2-BN composites is 1.81 g/cm3,and the flexural strength and elastic modulus are 113.9 MPa and 36.5 GPa,respectively.After oxidation treatment,the density varies to 1.80 g/cm3,and the flexural strength and elastic modulus are decreased to 58.9 MPa and 9.4 GPa,respectively.The mechanical properties of the composites are severely damaged,but they still exhibit a good toughness.The composites show excellent dielectric properties with the dielectric constant and loss tangent being 3.22 and 0.003 9,respectively,which indicates that the oxidation treatment is ineffective to improve the dielectric properties of SiO2f/SiO2-BN composites.

关 键 词：RADOME boron nitride urea route COMPOSITES oxidation treatment wave-transparent structure mechanical properties dielectric properties 

分 类 号：TB33[一般工业技术—材料科学与工程]