NANOCRYSTALLINE COMPOSITE MATERIAL BASED ON AL2O3 - ZRO2 - SIO2 AND ITS PRODUCTION METHOD

摘要

The merits of the present invention is production of commercially utilizable three- dimensional articles with nanocrystalline composite structure from a material based on Al2O3 - ZrO2 - SiO2. The nanocrystalline composite material contains 45 - 58 wt.% Al2O3, 28 - 38 wt.% ZrO2, 9 - 25 wt.% SiO2, its total porosity is below 5% and contains two levels of internal structure. At the micrometer level, the material is made up from mutually overlapping, thin and wavy discs (called splats) with thickness of up to 3 μm. The splats are formed by thermal spraying process and their respective chemical composition varies slightly. Inside of each splat, nanometer sized crystallites are found with average sizes ranging from 8 to 25 run and narrow size distribution. The nanometer sized crystallites are solely of one phase, which is the solid solution of tetragonal ZrO2 with Al2O3 and SiO2. The method producing the above material is as follows. Material containing Al2O3, ZrO2, and SiO2, is melted in arc furnace, the melt is casted, cooled, and crushed into powder with particle size below 120 μm. A coating is produced by thermal spraying of the powder onto a model preheated to 100-400 °C. The amorphous coating is removed during cooling and the temperature of crystallization in solid state (Tk) is determined by differential thermal analysis of the coating sample. The coating is then heated at a minimum heating rate of 5 K/s to a temperature from Tk -10 °C to Tk +80 °C, and after a dwell time of up to 60 minutes cooled at a minimum cooling rate of 5 K/s to the room temperature.