中文摘要：

采用低压化学气相沉积法（ LPCVD）在炭纤维表面制备了SiC涂层，借助扫描电镜、X射线衍射仪和拉曼光谱仪对不同沉积位置SiC涂层的微观形貌和晶体结构进行了表征。 SEM结果表明，沿气流方向，涂层表面逐渐致密和均匀；SiC涂层为多层结构，这种多层结构的形成可能是由于反应中产生的HCl气体吸附在表面反应活性点，从而通过活性点的阻塞机制来阻止SiC晶粒的生长。 XRD结果表明，制备的涂层中存在自由碳，各位置处的SiC晶体在（111）晶面存在择优取向，且沿气流方向（111）晶面的取向性逐渐减弱，（220）和（311）晶面的取向性逐渐增加。拉曼光谱低段频谱（200~600 cm-1）的出现表明CVD涂层中存在一定的缺陷。

英文摘要：

SiC coatings were prepared on carbon fibers by low pressure chemical vapor deposition （LPCVD）.The morphologies and crystalline structures of the coating at different deposition sites were analyzed by scanning electron microscopy （SEM）,X-ray diffraction （XRD） and Raman spectra （RMS）.The SEM images show that the coatings are dense and uniform along the gas flow di-rection. Furthermore,the coatings are multi-layers affected by the HCl, which is produced during the pyrolysis process.This phenom-enon can be explained by the “block active sites” mechanism. The results of XRD show that the free carbon coexists within the coatings and the （111） plane of-SiC crystallines at all positions are all preferred orientation.The degree of （111） plane preferred o-rientation is decreased,while other orientations such as （ 220） and （ 331） preferred orientation are increased along the gas direction. The appearance of a group of low-frequency bands at 200~600 cm-1 in RMS indicates that some defects exist in the SiC crystalline.