Investigation of tungsten powders prepared by plasma reduction method

Physico-chemical properties of tungsten powders obtained by tungsten trioxide and halides reduction in hydrogen plasma stream have been investigated. As evidenced by X-ray structural analysis, the powder contained two phases, namely b.c.c. lattice α-tungsten and β-tungsten of A-15 structure. The amount of oxygen in the powders has been determined. The β-W → α-W transition was found to start at 630 deg C and continue to 900 deg C. Magnetization of the plasmic W powder containing 30 % β-W has been measured. β-W with particles larger than 500 A displays the absence of superconductivity. Conditions in the plasmic stream provide for formation of metastable β-modification of tungsten in amounts up to 40 % regardless of the raw material