【摘要】 选择了一种MgO-Al₂O₃-SiO₂系统添加剂,能在1550℃的较低温度（约10wt％液相量,30MPa）将氮化硅材料热压致密化。由于氮化硅和碳纤维在此较低温度能够共存,从而使氮化硅有可能和碳纤维构成复合材料,以改善氮化硅的脆性。 本文研究了在1450—1650℃温度范围内,有液相存在的氮化硅的热压烧结机理和动力学。发现致密化过程与Kingery液相烧结机理较为吻合。过程溶解-扩散-再沉淀阶段的动力学可用ΔL/L₀=K·t^1/n表述。温度的差异明显地影响致密化速率;压力和液相量对致密化速率亦有较大影响。更多还原

【Abstract】 An additive of the MgO-Al₂O₂-SiO₂ system has been selected, with which Si₂N₁ can be hot-pressed to complete densification at a temperature of 1550℃ or above （approx. 10wt% liquid phase, under 30MPa pressure）. As Si₃N₄ and carbon fiber can coexist without damage at such a low temperature, it is possible to produce carbon fiber reinforced Si₂N₄ composite to improve the brittleness of Si₃N₄. The mechanism and kine- tics of sintering of hot-pressed Si₃N₄ in the presence of liquid phase at the temperature of 1450—1650℃ has been studied through the determination of linear shrinkage, rolative density of specimens as well as wettahility of additive composition with Si₃N₄. The densification process seems to be consistent with Kingery’s liquid phase sintering model. The kinetics of solution-diffusion-reprecipitation can be represented by the equation₂ ⊿L/L_o=K₁f^1’n. It is believed that hot-pressing temperature is the dominating factor influencing densification rate. Other processing parameters affecting the denstfication rate obviously are applied pressure and amount of liquid phase formed.更多还原