Akademik Veri Yönetim Sistemi
OXIDATION OF METALS, cilt.53, ss.1-23, 2000 (SCI-Expanded)
Fine powders of aluminum were produced in a pilot-plant, inert-gas atomizer with a "confined-design" nozzle, which operated vertically upward. Argon and helium at 1.85 MPa ann nitrogen at 1.56 MPa were used as the atomizing agent. The morphology of the powder particles was examined by SEM. Powders were sieved dry and wet. The Sauter mean diameter of the powders varied from 20.70 to 10.25 mu m depending on the atomizing gas. The distribution of sizes was bimodal. The mean thickness of oxide on the surface of the powder was calculated from the total oxygen contents of powder samples (determined by a Leco analyzer). In addition, ESCA measurements and BET tests were carried out for surface-oxide thickness and area measurements, respectively. The finest powder produced under helium incorporated thinner surface-oxide layers than the coarser ones produced under argon and nitrogen. This was due to differences in physical properties (such as density, thermal conductivity) and flow properties (such as gas velocity and relative velocity,) of the atomizing gases used i.e., helium, argon, and nitrogen. The oxide was very irregular in thickness in rite coarse-size range of the Al powders produced under argon and nitrogen. This was presumably, because of the high- and low-temperature oxidation of aluminum droplets during the atomization and subsequent solidification and cooling periods leading to the rough surfaces observed with SEM investigation in the present work.