热处理温度对BN界面涂层微观结构和相稳定性的影响

Influence of Heat-treatment Temperature on Microstructure and Properties of BN Interfacial Coatings

采用化学气相渗透工艺在SiC纤维表面制备BN界面涂层,在比沉积温度更高的温度下分别对涂层进行热处理。采用扫描电镜、透射电镜、拉曼光谱、X射线光电子能谱等技术,对BN界面涂层的微观结构和化学成分进行分析,并对涂层进行相稳定性能研究。结果表明:在850℃沉积的BN界面涂层分别在1050、1150、1250℃下进行热处理,BN均发生有序化转变,非晶态的BN转变为六方相;并且随着热处理温度的增加,BN结晶度增加。未经高温热处理的非晶态BN涂层易氧化,部分BN和空气反应生成B2O3;并且,在室温至1200℃时相稳定性差;经过热处理的涂层中几乎全部为BN,在室温至1200℃时无相变。

BN interfacial coatings were prepared on the surface of SiC fibers by chemical vapor infiltration(CVI).Then the coatings were heat-treated at several temperatures higher than the deposition temperature.The microstructure and chemical compositions of BN interfacial coatings were analyzed by scanning electron microscope,transmission electron microscope,Raman spectra,and Xray photoelectron spectroscopy,and the phase stability of the coatings were studied.The results show that when BN interfacial coatings deposited at 850℃were heat-treated at 1050,1150 and 1250℃,respectively,BN was ordered and amorphous BN was transformed into hexagonal crystallographic phase.Moreover,the crystallinity of BN increased with the increase of heat-treatment temperature.The amorphous BN coatings without high temperature heat-treatment were partly reacted with air to form B2O3.This kind of BN coatings had poor phase stability in the range of room temperature to 1200℃.The coatings with high temperature heattreatment were almost composed of BN,and there was no phase transformation from room temperature to 1200℃.