氮化硅陶瓷材料高温抗热震性能及其衰减规律研究

Study on Thermal Shock Resistance and Attenuation Law of Silicon Nitride Ceramic Materials at High Temperature

氮化硅陶瓷作为先进陶瓷材料具有耐高温、抗腐蚀等优异性能,因此被广泛应用于航空航天领域的强热冲击环境。热压烧结制备的Si_(3)N_(4)复合材料的抗弯强度较高,但抗热震性能随温度升高显著降低,热压烧结工艺在提升抗热震性能方面尚有不足。本文提出了使用二次热处理烧结方式来提高Si_(3)N_(4)陶瓷的抗热震性能,通过热压烧结-气压烧结二次热处理的烧结方式获得更致密、抗热震性能更好的Si_(3)N_(4)陶瓷材料。测试结果显示,常规热压方式制备的氮化硅陶瓷,随着热震温度的升高、次数的增加,材料内部产生微裂纹的概率增大,热震后试样抗弯强度逐渐降低,1200℃时平均强度下降率达23.48%。而经过二次热处理后氮化硅陶瓷抗弯强度略有降低,但抗热震性能得到明显改善,随着热处理时间增加,二次热处理后氮化硅陶瓷显微结构更加致密,抗热震性能将明显提高,热震后强度下降率明显减小,1200℃热震10次后强度下降率为12.25%。本文提出了提高Si_(3)N_(4)陶瓷的抗热震性的方法,探讨了氮化硅陶瓷在1200℃高温下的抗热震性能及其衰减规律,为改善氮化硅陶瓷器件高温性能提供了参考。

As advanced ceramic materials,Si_(3)N_(4)ceramics are widely used in strong thermal shock environment in aerospace field because of the excellent properties such as high temperature resistance and corrosion resistance.The Si_(3)N_(4)composites prepared by hot pressing sintering had high flexural strength,but the thermal shock resistance decreased rapidly with the increase of temperature.The hot pressing sintering process was still insufficient to enhance the thermal shock resistance.In this paper,a secondary heat treatment method of hot pressing sintering-gas pressure sintering was proposed to improve the thermal shock resistance of Si_(3)N_(4)ceramics,and obtain a denser Si_(3)N_(4)ceramic material with better thermal shock resistance.The results showed that with the increase of thermal shock temperature and times,the probability of micro-cracks in the SiN4 ceramics prepared by conventional hot pressing increased,and the bending strength of the samples decreased gradually after thermal shock,with the average strength reduction rate reaching 23.48%at 1200℃.After the second heat treatment,the flexural strength of Si_(3)N_(4)ceramics samples decreased slightly,but the thermal shock resistance was obviously improved.With the increase of heat treatment time,the microstructure of Si_(3)N_(4)ceramics after the second heat treatment became denser,and the thermal shock resistance was obviously improved.The strength reduction rate of the sample decreased significantly after 10 times of thermal shock at 1200℃,which was about 12.31%.Method of improving the thermal shock resistance of Si,Nceramics was proposed to study the thermal shock resistance and the attenuation law of Si_(3)N_(4)ceramics at 1200℃,which provided a reference for improving the high temperature performance of silicon nitride ceramic devices.