关键词: 微硅粉;焙烧;除碳;结构特性

Abstract: Calcination was used to remove the free carbon in silica fume,at the same time several analysis methods were adopted to study the influence of the calcination on silica fume.The experiment results show that free carbon content show ladder type change along with calcination temperature increase,it decreased at first,then remained stable,and drop again,keep stable at last.When temperature over 950 ℃,free carbon content,SiO2 content and weightlessness rate tend to be stable,0.05％,83.78％and 4.82％respectively.The structural feature of silica fume changed significantly during calcination.silica fume began to crystallize at 850 ℃,and the crystalline degree is increased with the increase of calcination temperature;Average particle size of silica fume increase with calcination temperature increase,from 0.490 μm before calcination increased to 0.817 μm after 2 h of calcination at 1050 ℃;With the increase of calcination temperature the circularity of silica particle decreased;under 850 ℃,silica fume kept the original spherical morphology,when the temperature over 850 ℃,spherical morphology is destroyed,and silica fume gradually change into random block;specific surface area increased with the increase of calcination temperature,when calcination temperature reached 850 ℃,silica fume began to crystallize and the specific surface area drops rapidly,until cannot be measured.

Key words: silica fume;calcination;carbon removal;structural feature