PCS原位热解法低温制备自结合碳化硅材料的研究

摘要

为了在较低温度下制备性能较好的自结合碳化硅材料，在黑碳化硅的基础配料中引入聚碳硅烷（PCS），以二乙烯基苯（DVB）作溶剂和交联剂，经混练、成型、烘干后，于1450℃保温5 h热处理，制备由聚碳硅烷原位热解产生的SiC结合的碳化硅材料，主要研究了PCS加入量（分别为黑碳化硅质量的3％、5％和7％）和热处理气氛（分别为N2气氛和埋炭气氛）对碳化硅材料体积密度、显气孔率、常温耐压强度、常温抗折强度、高温抗折强度、抗热震性、物相组成和显微结构的影响。结果表明：1）随着PCS加入量的增加，热处理后碳化硅试样的致密度、常温强度、高温强度和烧后线收缩率均增大。2）在PCS 加入量相同时，在两种气氛中热处理制备的碳化硅试样的致密度差别很小，但在N2气氛中热处理制备的碳化硅试样的常温抗折强度、常温耐压强度和高温抗折强度均比在埋炭气氛中制备的小。3）在N2气氛中热处理制备的碳化硅试样中含有少量Si2N2O，而在埋炭气氛中制备的碳化硅试样由β-SiC和α-SiC 组成；在两种气氛中热处理制备的碳化硅试样中都生成了纤维状物质，但在埋炭气氛中制备的碳化硅试样的纤维状物质更多，长径比更大。%This work aims at preparing high performance self-bonded silicon carbide materials at relatively low temperatures.Self-bonded silicon carbide materials were prepared by in-situ pyrolysis using black sili-con carbide as the basic ingredient,introducing polycarbosilane (PCS),divinylbenzene (DVB)as a sol-vent and a crosslinking agent,mixing,forming,drying,and then firing at 1 450 ℃ for 5 h.The influence of the PCS addition (3%,5% and 7% of the black silicon carbide content)and heat treatment atmosphere (N2 and carbon embedded atmosphere ) on the bulk density,apparent porosity,cold compressive strength,cold modulus of rupture,hot modulus of rupture,thermal shock resistance,phase composition and microstructure of the silicon carbide materials were researched.The results show that:(1)with the addition of PCS increasing,the density,cold and hot strength,and shrinkage rate of the fired silicon carbide speci-mens improve gradually;(2)with the same PCS addition,the difference in density of the silicon carbide specimens fired in two atmospheres is small;the specimens fired in N2 have lower cold compressive strength and cold and hot modulus of rupture;(3 )the silicon carbide specimens fired in N2 atmosphere contain a small amount of Si2 N2 O,while the silicon carbide specimens fired in carbon embedded atmos-phere consist of β-SiC and α-SiC;the silicon carbide specimens prepared in the two atmospheres both have fibrous materials,but the fibrous materials in silicon carbide specimens fired in the carbon embedded atmosphere is more and of greater fiber aspect ratios.