| 摘要 |
PURPOSE:To obtain metallic W powder of a high content of K with good reproducibility by reducing a W oxide of a high content of O cont. K to metallic W by way of a W oxide of a low content of O. CONSTITUTION:Wolframite and scheelite which are raw materials are screened, and are ground with a ball mill or the like. The powder is then subjected to an alkali treatment to extract W components. An acid treatment is applied to the W components to convert the same to tungstic acid; further, an aq. soln. of NH4OH is added thereto to obtain the crystal of ammonium paratungstate. The crystal is reduced in H2 of low moisture at about 500 deg.C, whereby blue oxide powder of 16-21% content of O is obtained. K2O, etc. are doped in the powder and the powder is reduced in low moisture H2 of about <=850 deg.C, whereby brown oxide powder of 3-11% content of O is obtd. The powder is reduced in low moisture H2 at about 1,000 deg.C, whereby metallic W powder is obtained. The powder is washed with acids to remove the ineffective doping agents stuck on the surfaces of the powder particles and is then dried thoroughly. |
