Si_3N_4-Al_2O_3-CaO系材料烧结性能及反应过程研究  

Sintering properties and reaction process of Si_ 3N_4-Al_2O_3-CaO composite in coke bed at high temperatures

作　　者：金胜利[1] 李亚伟[1] 陈汀水[1] 李楠[1] 

机构地区：[1]武汉科技大学高温陶瓷与耐火材料湖北省重点实验室,武汉430081

出　　处：《耐火材料》2003年第3期128-132,共5页Refractories

摘　　要：以氮化硅、活性氧化铝微粉和纯铝酸钙水泥为原料 ,研究了在焦炭保护情况下 ,Si3N4-Al2 O3-CaO系材料经 1 5 0 0℃、1 6 0 0℃和 1 6 5 0℃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 ,该体系材料的烧结性能与试样的组成和烧成温度有关 :温度由 1 5 0 0℃升至 1 6 0 0℃ ,试样体积密度增加 ,显气孔率降低 ,但升至 1 6 5 0℃时 ,试样的体积密度反而下降 ,显气孔率增加 ;在同一温度下 ,试样中Si3N4含量增加 ,体积密度下降。同时 ,试样在烧成过程中存在质量变化现象 :1 5 0 0℃烧成试样均表现为质量增加 ,当温度升至1 6 0 0℃和 1 6 5 0℃时 ,试样质量又由增加变为减小。根据热力学分析推测 ,试样烧成过程中存在复杂的化学反应 ,低于 1 5 0 0℃时 ,反应Si3N4(s) +3 /2CO(g) =3 /2Si2 N2 O(s) +1 /2N2 (g) +3 /2C(s)是试样质量增加的主要机理 ;高于 1 5 0 0℃时 ,反应Si3N4(s) +3 /2CO(g) =3 /2SiC(s) +3 /2SiO(g) +2N2 (g)是引起质量损失的主要机理。XRD分析显示 ,烧后试样中除存在刚玉和Si3N4相外 ,在烧成过程中还发生了物相变化 :1 5 0 0℃时出现了钙黄长石相 ,1 6 0 0℃时钙黄长石又消失 ,出现了Ca -α Sialon和β Sialon ,温度升至 1Si 3N 4-Al 2O 3-CaO composites are fired in coke powder bed at 1500 ℃,1600 ℃ and 1650 ℃.Their sintering properties and microstructures are investigated by SEM,EDX and XRD.The results show that their sintering properties are associated with their compositions and the sintering temperatures used.The bulk density of composites increases and their apparent porosity decreases from 1500 ℃ to 1600 ℃, whereas the phenomena at 1650 ℃ is contrary.Also,the bulk density of composites decreases with the increment of Si 3N 4 content at the same sintering temperature.Meanwhile,the mass changes occur in all composites fired at 1500 ℃,1600 ℃ and 1650 ℃.Thermodynamically,such reactions are inferred that Si 3N 4(s)+3/2CO(g)=3/2Si 2N 2O(s)+1/2N 2(g)+3/2C(s) is responsible for mass gain of all composites at 1500 ℃,and Si 3N 4(s)+3/2CO(g)=3/2SiC(s)+3/2SiO(g)+2N 2(g) leads to the weight loss at temperatures higher than 1500 ℃.Additionally,the phase changes are found in all composites examined by XRD as the sintering temperature rises up,although corundum,Si 3N 4,or only Si 3N 4 are main phases.At 1500 ℃,anorthite is produced in the system,and at 1600 ℃,anorthite is dissolved into liquid phase and at the same time,Ca-α-Sialon formed.At 1650 ℃,Ca-α-Sialon disappeared which is supposed that composition is deviated from Ca-α-Sialon stability region owing to the above reactions involved,and a great deal of β-Sialon was produced in the composites depending on Al 2O 3 and Si 3N 4 contents in the composites.

关 键 词：Si3N4—Al2O3—CaO系材料 烧结性能 反应过程 氮化硅 氧化铝 铝酸钙水泥 

分 类 号：TQ175.712[化学工程—硅酸盐工业]