Discuss of non-needle shape of violet tungsten oxide component:
Violet tungsten oxide is often of non-needle shape. One is large grain size, the other is small grain size.
Violet tungsten oxide produced by uniform ammonium paratungstate is of purple or fuchsia, some of the small grain is non-needle shape. Violet tungsten oxide produced by nonuniform ammonium paratungstate is black blue, there are more non-needle shape small grains. Small non-needle grain exists in uneven particles. Compared to needle shape, it is of low oxygen atom content without other impurity influences. It means for producing violet high quality violet tungsten oxide, except for the requirement for producing method, but also the uniformity of ammonium paratungstate.
Influences of micro structure of violet tungsten oxide on tungsten powder or tugnsten carbide powder:
Under low magnification SEM micrograph, the surface of violet tungsten oxide is rough, there are many small pores. Under the high magnification SEM micrograph, violet tungsten oxide is consisted of needle shape crystal and column crystal. These crystal are uneven in size. It makes the inside of violet tungsten oxide full of interspace, it is good for the volatilize of hydrogen and vapour, so the reduction can happens on the surface or inside the same time, so the reduction time will reduce and increase the reduction speed. It is better for producing little grain size tungsten powder.
Violet tungsten oxide being reduced into tungsten powder, the original needle shape or column shape is melted into rod, or formed into chain curves consisted of many single crystal, grain size is between 0.1-1um. This means the appearance changes a little, hydrogen makes the reduce of oxygen atom. The distribution of tungsten powder is even which is good for the carbonization of next reduction step.