TiO_(2)对Si_(3)N_(4)-SiC_(w)复合材料致密化和力学性能的影响

Effect of Titania Additives on Densification and Mechanical Properties of Si_(3)N_(4)-SiC_(w) Composites

以Yb_(2)O_(3)-Al_(2)O_(3)作为烧结助剂,采用烧结-热等静压工艺制备了具有高致密度和优异力学性能的Si_(3)N_(4)-SiC_(w)复合材料,研究了TiO_(2)含量对Si_(3)N_(4)-SiC_(w)复合材料致密化和力学性能的影响。结果表明:TiO_(2)的加入促进了Si_(3)N_(4)-SiC_(w)复合材料的致密化。随着TiO_(2)含量的增加,Si_(3)N_(4)-8%SiC_(w)复合材料的抗弯强度、断裂韧性和Vickers硬度均呈现出先提高后降低的变化趋势。当TiO_(2)含量(质量分数)为3%时,Si_(3)N_(4)-8%SiC_(w)复合材料的相对密度和综合力学性能最佳,其相对密度、抗弯强度、断裂韧性和Vickers硬度分别为(99.5±0.1)%、(1 301±87) MPa、(7.8±0.1) MPa·m^(1/2)、(16.2±0.1) GPa。TiO_(2)和Si_(3)N_(4)之间的原位反应生成的SiO_(2)和TiN对Si_(3)N_(4)-SiC_(w)复合材料的界面结合强度及力学性能产生了重要影响。

Si_(3)N_(4)-SiC_(w) composites were prepared via a sinter-hot isostatic pressing (sinter-HIP) process with Yb_(2)O_(3)-Al_(2)O_(3) as sintering additives.The effect of titania (TiO_(2)) addition on the densification and mechanical properties of Si_(3)N_(4)-SiC_(w) composites was investigated.The results show that the addition of titania enhances the densification of Si_(3)N_(4)-SiC_(w) composites.The flexural strength,fracture toughness and Vickers hardness of Si_(3)N_(4)-8%SiC_(w) composites firstly increase and then decrease with increasing titania content.Si_(3)N_(4)-8%SiC_(w) composites containing 3%TiO_(2) have a near-theoretical density and optimal mechanical properties (i.e.,the relative density of (99.5±0.1)%,the flexural strength of (1 301±87) MPa,the fracture toughness of (7.8±0.1) MPa·m^(1/2),and the Vickers hardness of (16.2±0.1) GPa).The formation of SiO_(2) and Ti N based on the in-situ reaction between TiO_(2) with Si_(3)N_(4)contributes to the improvement of the interfacial strength of bonding between SiC whisker and Si_(3)N_(4) matrix as well as the mechanical behaviors of the composites.