The main method for producing tungsten powder is calcinating ammonium paratungstate into yellow tungsten oxide or blue tungsten oxide, then producing tungsten powder in hydrogen atmosphere. Tungsten powder produced by this method is of regular polymorph, grain size is controlled at 2~5um. In 1980s, doping alkali metallic salt in tungsten oxide mainly use medium temperature reduction method, it can enlarge grain size of tungsten powder by several times over. In terms of average particle size of tungsten powder, doping is the most effective, but it also causes a lot of residue in powder. There is also research shows that adding a small amount of other element in APT can enlarge tungsten powder grain size and uniformity.
Ammonium Paratungstate Reduction Producing Coarse Spherical Tungsten Powder
Raw Material: Ammonium tungstate solution with density 1.23g/ml. Li2CO3 of chemically pure. NaCl crystalline powder of chemically pure. KCl crystalline powder of chemically pure. Hydrochloric acid of analytically pure.
1)First, add Li2CO3, NaCl or Li2CO3、NaCl、KCl in ammonium tungstate solution, dissolve it and make it into mother liquor, crystallization under 50℃.
2)To satisfy the required grain size and control the powder particle size requirements in the crystallization process, constantly added solution prepared ammonium paratungstate wet slurry, dry in the infrared oven to get ammonium paratungstate powder.
3)After grinding and pass the mesh, put in single pipe hydrogen furnace, reduce under 1000℃ and soaking time 90~180℃ atmosphere.
4)Tungsten powder obtained after reduction of the single-tube hydrogen furnace needs to be put into hydrochloric acid and deionized water, and ultrasonic wave is used for cleaning and washing until the solution is clarified, finally dried, grinded and sieved again, and the obtained tungsten powder is analyzed by energy spectrometer to determine alkali metal elements. If recorded in the allowable range, then pack the product, or to be re-cleaned.