摘要
选择了一种MgO-Al_2O_3-SiO_2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/L_0=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。
An additive of the MgO-Al_2O_2-SiO_2 system has been selected, with which Si_2N_1 can be hot-pressed to complete densification at a temperature of 1550℃ or above (approx. 10wt% liquid phase, under 30MPa pressure). As Si_3N_4 and carbon fiber can coexist without damage at such a low temperature, it is possible to produce carbon fiber reinforced Si_2N_4 composite to improve the brittleness of Si_3N_4. The mechanism and kine- tics of sintering of hot-pressed Si_3N_4 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 Si_3N_4. 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 equation_2 ⊿L/L_o=K_1f^(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.
出处
《硅酸盐学报》
EI
CAS
CSCD
北大核心
1989年第6期530-536,共7页
Journal of The Chinese Ceramic Society
关键词
氮化硅
烧结机理
低温热压烧结
Si_3N_4
mechanism and kinetics of sintering
hot-pressing at lower temperatures
