Making sintered, transparent, alpha-alumina cutting tip with sub-micron structure employs high purity alumina slip formed by elutriation and evaporation

摘要

Aqueous slip is prepared from alpha alumina powder, using dispersant based on a polycarboxylic acid. Alumina chemical purity is 99.99% or better. Mean particle size ranges up to 0.3 microns . Range of particle size distribution, D90/D10 is up to about 3, where D90 and D10 denote particle sizes referred to volumes, at 10% and 90% of the total distribution. All agglomerates and coarser particles are separated from the slip by sedimentation, forming a dispersed layer of the finest fraction. Controlled evaporation of dispersant takes place simultaneously, or later. The formed green body so formed is thermally pre-treated in air or under reduced air pressure, at temperatures of about 650 deg C and heating rates of about 30 K/h or less. Air sintering takes place at temperatures of 1300 deg C or less, to form the final product. An Independent claim is included for the molding produced, with mean particle size 0.4-0.7 microns and linear optical transmission of 20%, at wavelength 375 nm, through 0.5 mm thickness.