摘要
以氮化硅、活性氧化铝微粉和氧化硅微粉为原料,研究了在焦炭保护条件下,Si_3N_4-Al_2O_3-SiO_2系材料经1500℃、1600℃和1650℃烧成时的烧结性能和物相变化,同时借助SEM、EDX和XRD等手段对其显微结构和反应过程进行了观察和分析。结果表明,随着烧成温度的升高,Si_3N_4-Al_2O_3-SiO_2系材料的体积密度下降,显气孔率增加,同时烧成后试样的质量损失大大增加,尤其是经1650℃烧成的试样,显气孔率在40％以上,质量损失大于20％。XRD物相分析显示,1500℃时,产物中生成Si_2N_2O,高于1650℃时,生成SiC相,与热力学计算结果一致。同时,高温下大量的N_2(g)及SiO(g)逸出试样表面,可能是导致试样质量损失、结构松散、显气孔率增加的主要原因。切开经高温烧成的试样发现,其截面由中心致密区、过渡区和边缘的松散区3部分组成,含氮物相的形状由中心部位发育良好的柱状,演变成过渡区的针状或须状,直至松散区时消失。这种松散区所占面积和松散程度取决于试样的组成和烧成温度。
Si3N4 -AI2O3 -SiO2 composites are fired in coke powder bed at 1500 ℃ 1600 ℃ and 1650 ℃ respectively. Their sintering properties and microstructures are investigated by SEM,EDX and XRD. It shows that the bulk density of Si3N4 -AI2O3 -SiO2 composites increase and their apparent porosity decrease with the increment of firing temperatures,accompanying with the mass loss. Especially at 1650 ℃.the apparent porosities of all composites are more than 40% ,and their mass losses are more than 20%. Also,except for Si3N4 and corundum,Si2N2O phase is produced in composites fired at 1500 ℃,then Si2N2O, X and SiC phases at 1650 ℃,which is agreement with thermodynamic calculation. Simultaneously,it is supposed that gases such as N2(g) ,SiO(g) etc. escape from the surface of the composite at high temperatures,leading to the weight loss,loose structure and increment at apparent porosity. Correspondingly,the dense,transitional and loose areas are observed in composites from the center to the verge. The ratio of the loose area in the section relates to heating temperature and composite constitute. Also,well developed column and needle like grains of the nitrogen-containing phases are found in dense,transitional areas respectively,and disappear at loose area in the verge of composites.
出处
《耐火材料》
CAS
北大核心
2003年第5期262-266,共5页
Refractories
基金
教育部科学技术研究重点资助项目
