反应气体对ZrB_2涂层物相及显微结构的影响

Effect of reactive gas on the phase and microstructure of ZrB_2 coating

以ZrCl_4-BCl_3-H_2-Ar为反应体系,采用化学气相沉积法在石墨基体表面制备ZrB_2涂层。使用X射线衍射和扫描电镜(SEM)研究H_2和B与Zr的摩尔比对ZrB_2涂层物相和显微结构的影响。研究表明:在温度为1500℃,H_2流量为400 mL/min,B:Zr为1.434时,制备得到柱状晶组织的ZrB_2涂层。ZrB_2涂层中晶粒的生长以<110>和<100>方向为主,并随反应气体BCl3或H_2流量增加,<110>方向生长减弱,á100?方向生长增强。H_2流量变化导致沉积过程中气体的滞留时间和反应物组分变化,对涂层物相和结构产生影响。随H_2流量增加,涂层由致密变得疏松;当H_2流量为800 mL/min,B:Zr为1.434时,涂层中出现Zr B相。

ZrB2 coating was prepared on graphite substrate by chemical vapor deposition using ZrCh-BC13-H2-Ar as reaction system. The effects of H2 and mole ratio of B to Zr on the phase and microstructure of ZrB2 coatings were studied by X-ray diffraction and scanning electron microscopy （SEM）. The results show that the ZrB2 coating with columnar crystal structure can be obtained with the H2 flow rate of 400mL/min, B：Zr of 1.434 and the temperature of 1 500℃. The growth of grain in ZrB2 coating is mainly along （110） and （100） orientations. With increasing the flow rate of reactive gas BCla or H2, the growth along （110） orientation is weakened, and that along （100） orientation is enhanced. The variation of H2 flux rate leads to the change of gas retention time and reactant composition in the deposition process, which influences the phase and structure of the coating. With increasing H2 flow rate, the coating becomes loose. When the HE flux is 800mL/min and B：Zr is 1.434, the ZrB phase appears in the coating.