Characterization of nano-tungsten powder
Tungstenacid and ammonia as raw materials, pre-frozen with liquid nitrogen - freeze drying - two were prepared to restore access to the 30nm nano-W powder. Powder preparation process and the various stages of product was characterized by: using XRD, SEM, FESEM of freeze-dried powder, a reduction of powder and the second phase reduction of powder composition and morphology were analyzed. The results show that the present freeze-dried powder is amorphous, flocculent powder was reunited with no apparent particle morphology, surface smooth. Also showed a reduction of amorphous powders, loose sponge structure. The final product is the W crystalline powder, particle size distribution. IR results show that freeze-dried powder remains Keggin structure; thermal analysis showed that the freeze-dried powder in three phases lose their adsorbed water, crystal water, the structure of water.