Ammonium dodecamolybdomolybdate and method of making
A novel molybdenum compound, ammonium dodecamolybdomolybdate (AMM), is described which may be used in the manufacture of molybdenum metal and molybdenum carbide powders. The molybdenum compound is a dodecaheteropoly acid salt having a Keggin-type structure wherein molybdenum resides in both the hetero as well as peripheral atomic positions. The novel compound has the general formula (NH 4 ) 2 Mo 12 MoO 40 ·6H 2 O. Because of its low solubility, the compound can be crystallized efficiently and at a high purity from ammonium molybdate solutions.
1. A method for making a molybdenum metal powder comprising heating ammonium dodecamolybdomolybate in a reducing atmosphere at a temperature and for a time sufficient to form the metal powder.
2. The method of claim 1 wherein the ammonium dodecamolybdomolybdate is heated at a temperature from 5000° C. to 11000° C. for 2 hours to 6 hours.
3. The method of claim 1 wherein the particles of the molybdenum metal powder are mono-morphic having a dog-bone shape.
4. The method of claim 1 wherein the molybdenum metal powder has a submicron particle size.
5. A method for making a molybdenum carbide powder comprising:
(a) combining an ammonium molybdate solution with a carbon powder;
(b) precipitating ammonium dodecamolybdomolybdate from the ammonium molybdate solution;
(c) recovering the solids containing the carbon and ammonium molybdomolybdate from the solution; and
(d) heating the solids in a reducing atmosphere at a temperature and for a time sufficient to form the molybdenum carbide powder.
6. The method of claim 5 wherein the solids are heated at a temperature from 8400° C. to 1140° C. for 2 hours to 6 hours.