硅酸盐学报

本文采用燃烧合成工艺 ,在 10 0MPa氮气的气相热等静压作用下 ,制备了致密的AlN -TiB2 系陶瓷 ,相对密度达 95 % ,抗弯强度达35 0MPa.研究表明 ,Al-N2 -TiB2 体系燃烧过程中 ,当反应温度升至 6 6 0℃时Al熔化 ,10 0 0℃时Al开始剧烈挥发 ,与N2 迅速反应形成AlN .在反应区高温下熔融Al在TiB2 表面发生漫流现象 ,使Al的反应层厚度减小 ,反应面积增大 ,反应速度提高 .同时Al的漫流使燃烧反应区发生液相烧结 ,从而使反应区孔隙率显著下降 ,当开气孔闭合时在气相压力作用下形成致密产物 .随着TiB2 含量增加 ,液相烧结作用增强 ,产物致密度提高 .Al-N2 -TiB2 体系燃烧合成的致密化主要发生在燃烧波蔓延方向 ,具有明显的方向性 .

Compact AlN/TiB 2 ceramics was fabricated by combustion synthesis of Al particles in the super_high pressure nitrogen (100 MPa). Maximal relative density of 95% and maximal bending strength of 350 MPa are reached for the products. In the SHS process of Al-N 2-TiB 2 system, when the temperature is up to 660 ℃, metal Al melts and volatilizes strongly at 1 000 ℃. Al vapor vapidly reacts with N 2 to form AlN. At high temperature melted Al spread over the TiB 2 particle surface, which lead to a decrease of reaction layer thickness of melted Al, an increase of reaction surface and speed, and liquid sinter occurs. As a result, the porosity of the reaction zone decreases significantly. With increasing of TiB 2 content in the original powder system, liquid sintering decreases, and the relative density, bending strength and fracture toughness of the products are increased. In Al-N 2-TiB 2 system, SHS-densification has apparent tropism of mainly occurs along the combustion front.