Investigation of adsorption of some gases on tungsten powders prepared by plasma reduction

Processes of adsorption and desorption of water vapours, oxygen, nitrogen and hydrogen on tunsten powders with 2x10 m2/g specific surface prepared by reduction of tungsten trioxide in hydrogen plasma jet were investigated in 20-900 deg C temperature range. The powder with 0.1 m2/g specific surface prepared by usual reduction of WO3 in resistance furnaces was also investigated for comparison. Experiments were carried out in a high-vacuum assembly (pressure up to 10-7 mm Hg). It was shown that the desorption of H2O from ''plasma'' tungsten continued upto 500 deg C, and the quantity of extracted moisture was proportional to the specific surface of the sample. O2 desorption was practically the same for all samples of ''plasma'' W and considerably higher than for ''industrial'' tungsten, but the desorption rate depended on powder fineness. Nitrogen molecules formed a strong chemical bond with the metal even at low temperatures and nitrogen desorption into vacuum practically did not occur even at 900 deg C. Hydrogen desorbed almost completely when heated upto 400 deg C, but starting from 500 deg C its absorption by the powder intensified considerably