研究了ZrB2-20vol%SiC超高温陶瓷在空气气氛中的氧化行为,分析了氧化温度、氧分压和氧化时间等对硅酸锆形成和晶体生长过程的影响,提出了ZrB2-SiC超高温陶瓷氧化过程中硅酸锆相的形成机制.热力学计算结果表明,硅酸锆相的形成与高温下SiC的活性氧化有关.实验结果表明,常压氧化过程中,硅酸锆的形成可分为两个阶段,(Ⅰ)形核,这一过程与SiC的活性氧化有关;(Ⅱ)晶体生长,随着氧化时间的延长,氧化后形成的富硅玻璃相与氧化锆在硅酸锆晶核处反应,晶粒进一步长大.研究表明,在1500℃氧化90min后,硅酸锆的晶粒尺寸达到100μm左右.%Oxidation of ZrB2-20vol％ ceramic composites in air was investigated, and the effects of oxygen partial pressure, oxidation temperature and holding time on the formation of zircon phase ZrSiO4 were analyzed. The formation mechanism of zircon during oxidation in air of zirconium diboride-silicon carbide ceramic composites is proposed. Active oxidation of SiC is the major reason to explain the appearance of zircon according to thermal dynamic calculation results. The experimental results indicate that the formation of zircon can be divided into two steps: (I) Nucleation, which is related to the active oxidation of SiC; (I) Crystal growth, which is fulfilled by the reactions between silicate glass and zirconia crystalline at the interface of the zircon nuclei / melt. Zircon particles with mean size of 100 μm can be observed after oxidation in air for 90 min.
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