REACTIVE LASER ABLATION SYNTHESIS OF NANOSIZE ALUMINA POWDER

An aluminum (Al) target was laser ablated in an oxygen (O2) atmosphere, producing nanosize alumina (Al2O3) powder. The powder surface area decreased (and the particle size increased) with both increasing oxygen pressure and laser fluence. All powders produced had surface areas between 135 and 250 m2/g, corresponding to primary particle sizes ranging from 7 to 3 nm in radius. Phase evolution with temperature was studied via X-ray diffraction. These powders showed a direct transformation from gamma- to alpha-alumina at approximately 1200-degrees-C, bypassing other transition alumina phases, while still maintaining small particle size (< 30 nm). Despite the nanosize particles, green densities equal to 54% of the skeletal density (i.e., true density of the solid phase) were obtained by uniaxial pressing at 40 MPa.