人工心瓣含硅低温热解炭涂层热处理分析

Analysis of Heat Treatment of Silicon-alloyed Low Temperature Pyrocarbon Coating for Artificial Heart Valves

采用化学气相沉积法制备人工心瓣含硅低温热解炭涂层,并进行热处理。利用X射线衍射仪、扫描电子显微镜、透射电子显微镜、纳米压痕仪、热膨胀仪研究了热处理对涂层微观结构和性能的影响。结果表明,涂层包含热解炭(乱层石墨结构)与β-Si C两种物相,热处理后热解炭微晶层间距减小,表明石墨化程度提高,同时β-Si C微晶与热解炭微晶尺寸增大。电镜下材料主要由类球形颗粒组成,颗粒之间存在微米级孔隙,热处理后材料孔隙结构发生变化,大孔隙减少,孔隙分布更加均匀。热处理后材料纳米硬度明显减小,热膨胀系数略增大,微观结构的变化是导致材料性能改变的主要原因。

Silicon-alloyed low temperature pyrocarbon coating for artificial heart valves was deposited by chemical vapor deposition（ CVD）. The influence of heat treatment on the microstructure and mechanical properties of specimen was studied by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,nanoindentation and dilatometer. The results show that the coating consists of two phases named pyrocarbon（ turbostratic graphite-like structure） and β-Si C. After heat treatment the grain size of both become larger,and the carbon（ 002） planar spacing decreases which means the degree of graphitization of pyrocarbon improved. SEM and TEM show the material consists of spherical particles,and there exists pores among the particles. After heat treatment the pore structure of the material is changed,the number of large pores decreases,the pore distribution is more uniform. The changes in microstructure consequently cause the decrease of nano-hardness and increase of thermal expansion coefficient.