Study On Technology Of Porous Mullite Ceramics Synthesized By Fly Ash And Pore Fractal

Fly ash, an industrial solid waste by-product,has caused significant pollution to enviroment. Their recycling is one of the tasks in the field of environment protection which should be solved in near future.In this study, fly ash,Alumina and starch was as raw material. Porous mullite ceramics with high porosity and high strength was fabricated via the SCC (starch consolidation casting) process. Through the fractal analysis of pore structure to study, in addition to porosity, the effect of the fractal structure of the pore on the material properties. By studying the effects of types of starch, starch content, solid content on slurry rheological properties, the appropriate preparation process of slurry was selected. The effects of types of starch, starch content, solid content on microstructure and properties of porous mullite were studied. The relationship between porosity and properties of porous mullite were also analyzed. Fractal analysis of pore structure were analyzed by image-pro-plus image analysis software. The microstructure and properties of material was tested by SEM, XRD, viscometer and universal testing machine.The results showed that: The slurry with potato,cassava,corn starch all belong to pseudoplastic fluids. The viscosity of the slurry containing potato starch was the largest and an increase in viscosity with increasing milling time was the most significant. According to slurry characteristics and the nature of forming green body, the preparation process of adding starch by step were developed.Using different types of starch prepared porous mullite ceramics,the size and shape of the pore were determined by appropriate starch nature. Pore size of porous ceramics with potato starch was maximum. Combination of all factors, porous mullite ceramics with potato starch had higher porosity and higher strength than with the other two starch. In the same condition,potato starch showed great performance in the preparation of porous ceramic process.Porosity and bending strength of porous mullite ceramics could be changed by the content of starch. Considering microstructure porosity and strength of porous ceramics. The porosity of porous mullite ceramics with 30wt% starch content and 70wt% solid content sintered at 1500℃, was above 60%, bending strength of ones attained above 40MPa.Solid content had a significant impact on the slurry viscosity and porosity and strength of green body and ceramic. In order to avoid the green body and ceramics had deformation defects,the solid content should be appropriately increased.Fractal dimention was important parameters which can describe the feature of the pore space geometry and distribution. By analyzing the relationship between strength and porosity,pore size,fractal dimention,it was found that with the same pore-forming agent, the influence of the porosity on the strength was consistent with fractal dimension. With the fractal dimention of pore volume decreased and the porosity reduced,the strength of porous ceramics increased; When with different pore-forming agents, the regularity of the relationship between porosity, pore size and strength is not obvious, but there are also relationship between the fractal dimension and strength, With the fractal dimention of pore volume decreased, the strength of porous ceramics increased.