气体流量对LPCVD ZrC涂层结构和沉积机理的影响

利用低压化学气相沉积(LPCVD)工艺,采用Zr-Br2-C3H6-H2-Ar反应体系,在1200℃下,于石墨基底表面制备了ZrC涂层。研究了气体流量对ZrC涂层微观形貌和沉积机理的影响。结果表明,随着气体流量由200 mL/min向1000 mL/min增大,涂层的沉积速率先增大后减小,在800 mL/min时达到极值,极大值为3.37×10-3g·cm-2·h-1。同时,涂层的择优取向发生了明显的变化,在600~800 mL/min范围内,涂层具有稳定且强烈的(200)晶面择优取向。XPS分析结果表明,沉积产物中的C/Zr比也随气体流量的增大,相应的由0.85快速地升高到1.49。当气体流量为200 mL/min时,涂层致密光滑,ZrC晶粒具有典型的等轴晶结构特征;当气体流量为400~800 mL/min时,涂层光滑平坦,ZrC晶粒具有规则的四面体结构;当气体流量为1000 mL/min时,涂层表面存在着大量不规则的岛状、弓状颗粒。基底表面边界层厚度的变化是影响涂层沉积过程的主要因素。

Effect of Total Flow Rate on Morphology and Growth Mechanism of ZrC Coating Prepared by LPCVD

Zirconium carbide(ZrC) coatings were deposited on graphite substrate at 1200℃ by low pressure chemical vapor deposition(LPCVD) using the Zr-Br2-C3H6-H2-Ar system.The effects of total flow rate on the microstructure and growth mechanism of ZrC coatings were investigated.The results show that as the total flow increases,the deposition rate increases firstly and then decreases slowly,and the deposition rate reaches the maximum of 3.37×10-3 g·cm-2·h-1 at the total flow rate of 800 mL/min.Meanwhile,the preferential orientation of ZrC coatings changes evidently,and the(200) plane is the preferential orientation of ZrC coatings at the total flow rate of 600~800 mL/min.XPS results show that the C/Zr ratio of ZrC coatings increases from 0.85 to 1.49.At the total flow rate is 200 mL/min,the ZrC coatings are dense and composed of equiaxed gains.As the total flow rate increases from 400 to 800 mL/min,the ZrC coatings are well-faceted pyramidal-shaped crystals.When the total flow rate is 1000 mL/min,the ZrC coatings own loose complex island-like gains.The variation of ZrC coatings is mainly attributed to the boundary layer with increasing the total flow rate.