冷冻胶凝成型制备Si_(3)N_(4)复相陶瓷材料的高温力学特性

High-temperature Mechanical Properties of Si_(3)N_(4) Composite Ceramics Prepared by Freeze Gelation

采用新型冷冻胶凝陶瓷成型技术制备Si_(3)N_(4)/钡长石(BaAl_(2)Si_(2)O_(8),BAS)复相陶瓷材料,研究了不同温度(25~1 400℃)和BAS含量(质量分数)条件下,Si_(3)N_(4)/BAS复相陶瓷材料弯曲强度、弯曲模量、弯曲断裂特性以及陶瓷微观结构。结果表明:BAS含量提高可显著提高材料高温力学性能,在1 400℃和40%BAS含量时,Si_(3)N_(4)/BAS复相陶瓷材料弯曲强度和弯曲模量分别可达241.0 MPa和92.0 GPa。在25~1 400℃,当BAS含量为30.0%~40.0%时,Si_(3)N_(4)/BAS试样加载断裂均表现为脆性断裂模式,此时材料烧结体主要由β-Si_(3)N_(4)和BAS两种晶相组成,不含Si_(2)N_(2)O晶相。当环境温度为1 500℃空气条件下,不同BAS含量的试样均出现明显的表面氧化现象,温度低于1 400℃时无表面氧化现象。

Si_(3)N_(4)/BaAl_(2)Si_(2)O_(8)(BAS)composite ceramics were prepared by a novel freeze gelation method.The flexural strength,flexural modulus,flexural fracture and microstructures of Si_(3)N_(4)/BAS composite ceramics were investigated at different temperatures(i.e.,25–1400℃)and BAS contents(i.e.,7.5%–40.0%,in mass fraction).The results show that the high-temperature mechanical properties of Si_(3)N_(4)/BAS composite ceramics can be improved via the increasing of BAS content.At 1400℃and 40%BAS,the flexural strength and flexural modulus of Si_(3)N_(4)/BAS composite ceramics are 241 MPa and 92 GPa,respectively.At 25–1400℃and 30%–40%BAS,Si_(3)N_(4)/BAS composite ceramics become a rigid fracture mode,and the sintered body is mainly composed ofβ-Si_(3)N_(4) and BAS without Si_(2)N_(2)O.In air,the testing samples show a surface oxidation phenomenon at 1500℃,but the samples are not oxidized at<1400℃.