Satoshi Sugita
University of Guanajuato, Mexico
Title: Homogeneous precipitation of ceramic powders preparation from sulfate-sulfiteammonia system
Biography
Biography: Satoshi Sugita
Abstract
High quality ceramic powders can be produced by homogeneous precipitation. This method permits to control purity, particle size, shape, distribution and homogeneity, as known these factors play a very important role in the properties of finished ceramic materials. Alumina nano-sized particles could be obtained starting from the admixture of solutions of aluminum sulfate and ammonium bisulfite. The homogeneous precipitation carried out at pH 4.2, when the mixture of solutions was heated to the decomposition and boiling temperature. Nano-, spherical with narrow size distribution, and soft agglomerated, the basic aluminum sulfate (BAS) was easily produced. The powder was heated at 950 oC to decompose sulfate and then was calcined a 1250 oC to transform to a-alumina. Otherwise, treating BAS with aqueous ammonium solution, the precipitate could be transformed to nano-sized fibrillar pseudoboehmite, which could be transformed to g-alumina by calcining. On the other hand, to prepare mullite precursor, initially the silica nano powder (Aerosil 200, Degussa) was dispersed in water and mixed with the solutions of aluminum sulfate and ammonium bisulfite. The admixture was heated to the decomposition and boiling temperature, in which a precipitate of silica covered with BAS was produced. This precursor was transformed to mullite heating at 1250 oC. The other application example of this homogeneous precipitation is used to prepare in the fabrication of basic chromium sulfate. Starting from the admixture of solutions of chromium sulfate and ammonium bisulfite, the basic chromium sulfate can be precipitated. But in the last case it is not easy for all chromium precipitate since chromium forms a water soluble complex with ammonia. Even though, almost every chromium can be precipitated. In this presentation, a simple useful technique of homogeneous precipitation for preparing the basic sulfate salts of metals starting from the admixture of metal ion-sulfate-sulfite-ammonia aqueous system is discussed.