Effects of different forming methods on the properties of solidified body by non-firing process through the mechanochemical treatment

Abstract

A "non-firing ceramic process" for producing high-strength ceramic solids without calcination is developed. In this process, a ceramic powder, activated by mechanochemical processing, is dispersed in an alkaline solvent to dissolve any metallic ions in the powder and to form precipitates between grains via reprecipitation. The ash powder of the incinerated paper sludge (PS ash, waste generated during paper recycling) is subjected to mechanochemical processing using a planetary ball mill, and non-fired compacts are prepared by wet forming or dry press forming; the effects of different forming methods on the compact properties are investigated. The compacts obtained by the wet forming had a low mechanical strength because the impurities in the PS ash reacted with KOH, resulting in gas emission during solidification and thus in the fracture of already solidified matter through the expansion of gas volume. However, dry press forming yielded good-quality compacts with few defects such as pores and cracks because only the minimum amount of the powders surface necessary for solidification was dissolved and reprecipitated, limiting the excessive dissolution of powder by the KOH solution.