Arsenic doped ammonium metatungstate (AMT) is generated by adding ammonium metatungstate into the nitric acid solution of elemental arsenic and stirring, drying and grinding, the excellent raw material for preparing nano tungsten powder. Nano tungsten powder is the tungsten powder which the particle size is fine to nanoscale, at present, the traditional method for manufacturing nano tungsten powder is tungsten oxide reduction method, wherein the reducing agent maybe hydrogen or carbon; with the appearing of nano materials, the manufacture methods of nano tungsten powder are emerging constantly, such as high-energy ball milling, gas evaporation, plasma, self-propagating high-temperature reduction and molten salt electrolysis method.
There is a study to take ammonium metatungstate as raw material, and through doping process to get arsenic doped ammonium metatungstate to finally get nano tungsten powder, with the producing process like the following:
1. Preparation of arsenic doped ammonium metatungstate precursor composite powder
Add a certain amount of elemental arsenic into the nitric acid with a certain concentration, then add ammonium metatungstate into the nitric acid solution of elemental arsenic after the As is completely dissolved with the arsenic content being controlled; electric mix the raw materials, then dry them in a oven under 70~90°C for 8~10 hours, and then, grind to get arsenic doped ammonium metatungstate precursor compound powder.
2. Arsenic doped ammonium metatungstate calcination to prepare yellow tungsten trioxide powder
Put the prepared arsenic doped ammonium metatungstate precursor compound powder in a box type resistance furnace at the temperature of 580~620°C to carry out calcination in air atmosphere for 2~3 hours, then we get yellow tungsten trioxide powder.
3. Tungsten trioxide reduction to generate nano tungsten powder
Put the yellow tungsten trioxide powder in a tube furnace to get reduction by inletting hydrogen, under the reduction temperature of 780~820°C with the heating rate of 5°C/min, and the heat preservation time of 3~4 hours, to finally manufacture nano tungsten powder
The nano tungsten powder get by arsenic doped ammonium metatungstate has the advantages of good dispersion, and uniform particle size distribution, thus to effectively promote the development and application of nano-crystal WC-Co alloy.