Preparation And Property Study Of Mullite Ceramic Materials Utilizing Silicon From Silica Fume

In our country, silica fume production is huge. Silica fume is considered as solidby-product of smelting silicon series products. Not only its recovery and storage increaseenterprise operation cost, but also it causes great pollution to the atmospheric environment.Therefore, make the realization of the recovery and utilization of silica fume so as to realizethe waste to treasure, to alleviate the burden on enterprises income, to improve the air qualityof the environment.Silica fume has higher SiO2content. In experiment, we used silica fume as main rawmaterial with different aluminum sources, taking different ceramic material preparationtechnology to synthesize several kinds of mullite material.Firstly, Silica fume and industrial aluminum oxide powder were taken as reactionmaterial, we studied the effects of Al2O3/SiO2molar ratio, calcination temperature andholding time on the synthesis of mullite. Moreover, we discussed the law between mullitepowders milling characteristics and planetary ball milling time. The results show thatcompared with amorphous SiO2as silicon source, silica fume is in favor of preparing mullite,and when the sample of which Al2O3/SiO2molar ratio is3:2.5at1450℃for4h, the powderpreparation of mullite content is the highest, mullite powder average particle size decreaseswith the increase of milling time, the particle size distribution evolves from the beginning ofun-imodal uni-modal distribution to bimodal distribution, the size and specific surface area offinal milling powder are0.58μ,9.26m2/g, respectively.Secondly, in the above foundation, porous mullites were prepared by two kinds porousceramics molding process of tert-butyl alcohol based gel-casting and adding potato starch aspore. Gel-casting: when calcination temperature is1300℃for4h, the volume density andporosity of porous mullite sample with3:2.5of Al2O3/SiO2molar ratio are2.5g/cm3,21%,and while the calcination temperature is1400℃, the compressive strength of sample reach to260.9330.22MPa. Adding potato starch as pore: when the sintering temperature is1450℃for4h and starch content is40wt%, the samples with3:2.5of Al2O3/SiO2molar ratio reach itshighest content of mullite, and its volume density, thermal conductivity and flexural strengthare2.02g/cm3,1.40W m-1K-1,79.91MPa, respectively; There are a lot of interleaving slivershaped mullite crystal in matrix, the crystal morphology can not only make the pore structurestable to maintain a certain porosity reducing the thermal conductivity of the composites, butalso give the mechanical properties of sample with good. Finally, we study the effects of different calcination temperature on the synthesis ofmullite as well as its microstructure in the two salt conditions of K2SO4and Na2SO4, usingsilica fume and aluminum sulfat as the main raw material. The results show that1000℃is theoptimum calcination temperature for both salt condition. The mullite whiskers prepared bymolten sodium sulfate after alkai treatment have higher straight gain rate and smooth surface,the values of its length, diameter, apparent density and surface area are3~4μm,10~30nm,0.26g/cm3and13.5m2/g, respectively.