FLAKY ALPHA-ALUMINA CRYSTALS WITH LARGE ASPECT RATIO AND PREPARATION METHOD OF THEM

摘要

A method for preparing flaky alpha-alumina crystals is provided to allow easy control of the thickness and size of the crystals, to maintain an aspect ratio of at least 100, and to realize the use of the alpha-alumina crystals as a matrix for a high-quality pearl pigment, ceramic material or filler. A method for preparing flaky alpha-alumina crystals comprises the steps of: mixing an aqueous aluminum precursor solution containing an aqueous solvent with an aqueous precursor solution containing 0.05-5 parts by weight of a zinc precursor and 0.01-0.5 parts by weigh of a tin precursor based on 100 parts by weight of the aluminum precursor to provide an aqueous metal precursor solution; titrating the aqueous metal precursor solution with an aqueous sodium salt solution to a pH of 6.0-7.5 and carrying out hydrolysis to obtain a mixed gel; pretreating the mixed gel by aging the mixed gel at 60-100 deg.C for 5-30 hours, followed by drying; drying the pretreated gel at 60-200 deg.C for 5-30 hours; crystallizing the dried gel at 850-1300 deg.C for 1-8 hours to obtain crystallized cake; and cooling the crystallized cake to room temperature, dissolving the cake into water at 20-90 deg.C, followed by filtering to remove the solvent, and dispersing the resultant product into 0.1-30% sulfuric acid solution at 20-90 deg.C, followed by filtering, washing with water and drying to obtain alpha-alumina crystals. Further, the aluminum precursor is selected from acid salts of an aluminum, a halide and an oxide.