Sc-Si-Si_3N_4陶瓷高温氧化对其力学性能的影响

Effect of high-temperature oxidation on mechanical properties of Sc-Si-Si_3N_4 ceramics

为改善Si3N4陶瓷的抗氧化性能以提高该材料使用寿命和可靠性,以Sc2O3和SiO2为添加剂,用真空热压烧结法制得Sc-Si-Si3N4陶瓷,并对该陶瓷在高温下的氧化行为及力学性能的变化进行了研究.采用X射线衍射、扫描电子显微镜和重量分析法研究了不同温度下的恒温热处理对陶瓷的表面相、氧化后形貌及陶瓷重量的影响;用三点弯曲法测量了抗折强度.结果表明,在1200～1400℃保温,陶瓷的氧化符合抛物线规律,其活化能为521kJ/mol,显示了较好的抗氧化性能.氧化过程主要由晶界添加剂离子及少量杂质离子和氧的双向扩散控制,氧化产生的表面裂纹和空洞使抗折强度明显降低.

To improve the oxidation resistance and increase the operating life and reliability of Si3N4 ceramics the oxidation behavior and variation of mechanical properties of hot-pressed Sc2O3-SiO2 doped Si3N4 ceramics at high temperature were investigated. The influence of isothermal heat treatment on the crystalline phase, the morphology of surface, and the weight of the prepared samples was measured by XRD, SEM and weighting method, respectively. Bending strength of these samples was measured by three-point bending method. The results indicate that the weight increment raised by oxidation in the range of 1200 - 1400 ℃ follows the typical parabolic regularity. The calculated oxidation activation energy of the material is 521 kJ/mol, which exhibits the good oxidation resistance behavior of the material. The oxidation process is mainly controlled by bidirectional diffusion between the additive ions or minor impurities and oxide ions. Cracks and pores caused by the surface oxidation are believed to be the main reason of decrease of bending strength of the material after heat treatment.