Method of making nanocrystalline tungsten powder
There is described a method of making a nanocrystalline tungsten powder that comprises: (a) heating a tungsten-containing material in a reducing atmosphere at an intermediate temperature of from about 600° C. to about 700° C. for an intermediate time period; the tungsten-containing material being selected from ammonium paratungstate, ammonium metatungstate or a tungsten oxide; and (b) increasing the temperature to a final temperature of about 800° C. to about 1000° C. for a final time period.
1. A method of making a nanocrystalline tungsten powder, comprising:
a) heating a tungsten-containing material in a reducing atmosphere at an intermediate temperature of from about 600° C. to about 650° C. for an intermediate time period of at least 2 hours; the tungsten-containing material being selected from ammonium paratungstate, ammonium metatungstate, or a tungsten oxide; and
b) increasing the temperature to a final temperature of about 800° C. to about 1000° C. for a final time period.
2. The method of claim 1 wherein the reducing atmosphere comprises hydrogen gas.
3. The method of claim 1 wherein the intermediate temperature is about 650° C.
4. The method of claim 1 wherein the final temperature is about 900° C.
5. The method of claim 1 wherein the final time period is at least 1 hour.
6. A method of making a nanocrystalline tungsten powder, comprising:
a) heating a tungsten-containing material in a hydrogen-containing atmosphere at an intermediate temperature of from about 600° C. to about 650° C. for an intermediate time period of at least 2 hours; the tungsten-containing material being selected from ammonium paratungstate, ammonium metatungstate, or a tungsten oxide; and
b) increasing the temperature to a final temperature of about 800° C. to about 1000° C. for a final time period.
7. The method of claim 6 wherein the intermediate temperature is about 650° C.
8. The method of claim 7 wherein the final temperature is about 900° C. and the final time period is at least 1 hour.
9. The method of claim 8 wherein the hydrogen-containing atmosphere consists essentially of dry hydrogen.
10. The method of claim 6 wherein the hydrogen-containing atmosphere is selected from an H 2 /N 2 , H 2 /Ar, H 2 /He gas mixture.