以SICl4-NH3-H2为反应体系,采用化学气相渗透法CVI)制备C/Si3N4复合材料.渗透产物的能谱和X射线衍射表明渗透产物为非晶态Si3N4,经1350℃真空热处理后,产物仍然为非晶态Si3N4;经1450℃真空热处理后,产物已经发生晶型转变,由非晶态转变为晶态的α-Si3N4和β-Si3N4.渗透温度、渗透时间、气体流量对试样致密化、增重及微观结构的影响研究表明渗透温度为900℃、SiCl4流量为30mL/min、H2流量为100mL/min、NH3流量为80mL/min、渗透时间120h、系统压力1000Pa时,气体渗透进入碳布预制体后,在预制体内反应均匀,制备的复合材料较均匀.
C/Si3N4 composites were prepared by chemical vapor infiltration methods (CVI) from SiCl4-NH3-H2 system. The element and phases of the as-processed sample were characterized by EDS and XRD. The phase of the as-processed sample is an amorphous silicon nitride. The phase of the sample heat treated at 1350℃ is also an amorphous silicon nitride. The XRD indicates that the formation of α-Si3N4 and β-Si3N4 occurs after heat treatment at 1450℃. The influences of temperature, time and gas flux on densification, weight and microstructure were investigated. The results show that the gases infiltrate and react in preforms equably, the carbon preforms can be infiltrated uniformly and the uniform C/Si3N4 composites were prepared when the process parameters are as follows: temperatrure 900℃, SiCl4 flow 30mL/min, H2 flow 100mL/min, NH3 flow 80mL/min, time 120h and total pressure 1000Pa.
参考文献
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