ZrB_2-SiBCN复合陶瓷恒温氧化行为研究

Oxidation Behavior of ZrB_2-SiBCN Composite Ceramics at Constant Temperature

高温结构材料ZrB_2陶瓷由于其烧结温度高,应用受到限制,SiBCN聚合物前驱体的添加降低了ZrB_2的烧结温度,并能够获得致密的ZrB_2-SiBCN复合陶瓷。研究其氧化行为对于ZrB_2-SiBCN陶瓷在高温领域的应用有重要的意义。通过XRD、SEM等手段对陶瓷1300℃时氧化行为进行了分析和研究,结果表明,在高温空气环境下,SiBCN陶瓷氧化直接生成硼硅酸盐玻璃,硼硅酸盐玻璃粘度低,铺展速度快,在陶瓷表面可形成氧化物保护层,阻碍陶瓷的进一步氧化。ZrO_2与SiO_2反应生成新的ZrSiO_4相,使硼硅酸玻璃层因被消耗而变薄,ZrSiO_4附近的ZrB_2颗粒从硼硅酸盐玻璃层内裸露出来,加速了ZrB_2的氧化。ZrSiO_4相的生成降低了硼硅酸盐玻璃对陶瓷的抗氧化保护作用。

High sintering temperature is one of the biggest challenge in the application of ZrB2 ceramics. Sintering temperature could be reduced and dense ZrB2-SiBCN composite ceramics were prepared by the addition of PBSZ as a sintering additive. Research on oxidation process is of great important for the application of ZrB2-SiBCN ceramics in high-temperature field. In this paper, the oxidation behavior at 1300 ℃ was researched and analyzed by XRD and SEM. The results showed that SiBCN ceramics oxidized and formed borosilicate glass. The lowly viscous glass spreaded over the surface, a continuous coating thus forms and further oxidation can be prevented. The generation of ZrSiO4 by reaction between ZrO2 and SiO2 consumed the borosilicate glass coating. The ZrB2 particles exposed near the ZrSiO4 phase as a result, which speeds up the oxidation. The ZrSiO4 phase weakened the oxidation resistance of borosilicate glass.