Papers by Author: Wen Jun Wang

Abstract: Effects of Al in different added condition on pores shape and mullite configuration were investigated. Three sorts of hole were got by using Al as foaming agent in mullite composites. It was concluded that isolated holes could be formed by Al changing to Al2Ol3 with acidity condition in green state, open holes could be formed by Al changing to Al2O3 directly in sintering process, and mixed hole of isolated and open ones could be formed by Al changing to Al(OH)3 with alkalescence condition in green state followed changing to Al2O3 in sintering process. These holes could supply a position for growth of mullite as well.

Abstract: Porous mullite was prepared from a reactive mixture of Al metal powder and the fly ash produced by power plant. The sintering ceramics was characterized for the pore structure and phase identification studies. It was found that the sintered specimen expands at first (1300-1400°C) and then shrinks which was correspondence to the changing of open porosity. The expansion was attributed to the fact that the alumina produced from the oxidation reaction of Al powder made the volume larger than the starting mixtures. At 1550°C, it was inferred that the alkaline element in the fly ash made the mullite decomposed then destroyed the mullite structure. The SEM photographs suggested us that the pore diameter of the sintered ceramics might be adjusted by adding Al powder with different grain sizes. Moreover, because of the rod-like mullite produced in the pores, Mg metal addition could develop the further modification of the pore structure with similar porosity (47% at 1400°C/4h) compared with that (53%) with 0wt % Mg metal powders.