【摘要】 通过热解聚碳硅烷(PCS)和聚硼硅氮烷(PBS)两种有机先驱体混合物,制得非晶态SiC/SiBCN复合陶瓷,然后对复合陶瓷进行高温热处理,研究其析晶规律及影响因素。利用热分析(TG-DTA)、X射线衍射(XRD)及透射电子显微镜(TEM)分别研究先驱体的热解机理,先驱体的组成、热解温度和时间对SiC/SiBCN复合陶瓷结晶性的影响,以及复合陶瓷的微观结构。结果表明,先驱体的组成和热处理温度对复合陶瓷的析晶行为有重要影响。当PBS/PCS=1(w/w),1100℃/2 h制得非晶态SiC/SiBCN复合陶瓷;1400℃/4 h PCS热解转变的非晶SiC开始结晶,晶粒尺寸~3 nm;1500℃/4 h得到产物的相结构为~10 nm的SiC纳米晶均匀弥散在PBS热解得到的非晶态SiBCN中;1700℃/2 h SiC的晶粒尺寸~16 nm;1800℃/2 h非晶态SiBCN开始析晶,SiC晶粒尺寸~35 nm。更多还原

【Abstract】 A novel amorphous ceramic composites was fabricated from precursors mixed by polycarbonsilicon(PCS) and boron-modified polyvinylsilazane(PBS).The crystallization of the ceramic composites was studied after heat-treated at high temperature.Thermal analysis(TG-DTA),X-ray diffraction(XRD) and Transmission electron microscope(TEM) were utilized respectively to analyze the mechanism of pyrolysis,the effects of precursor compositions,pyrolysis temperature and time on crystallization and the microstructure of the sample.The experimental results indicate that the precursor compositions and the temperature have a major impact on the crystallization behavior.The SiC/SiBCN ceramic composites annealed 1100 ℃/2 h are prepared when PCS/PBS= 1(w/w) and pyrolysized.The SiC crystallites about 3 nm in size appear at 1400 ℃/4 h,which are pyrolysized from PCS.The microstructure of ceramic composites is SiC crystallites with ~10 nm in size embed in the amorphous SiBCN homogenously at 1500 ℃ /4 h.When the ceramic composites are heat-treated at 1700 ℃ for 2 h,the size of the SiC crystallites increases to ~16 nm.Moreover,the amorphous SiBCN starts to crystallize at 1800 ℃/2 h and the SiC crystallites grows to about 35 nm.更多还原