Production of nanocrystalline metal powders via combustion reaction synthesis

Patent metadata

Field	Value
Publication number	US-9802834-B2
Application number	US-70092310-A
Country	US
Kind code	B2
Filing date	Feb 5, 2010
Priority date	Feb 5, 2010
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

Nanocrystalline metal powders comprising tungsten, molybdenum, rhenium and/or niobium can be synthesized using a combustion reaction. Methods for synthesizing the nanocrystalline metal powders are characterized by forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and a base-soluble, ammonium precursor of tungsten, molybdenum, rhenium, or niobium in amounts that yield a stoichiometric burn when combusted. The combustion synthesis solution is then heated to a temperature sufficient to substantially remove water and to initiate a self-sustaining combustion reaction. The resulting powder can be subsequently reduced to metal form by heating in a reducing gas environment.

First claim

We claim:

1. A method for synthesizing powders by a combustion reaction, the method comprising:
forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and at least one base-soluble ammonium metatungstate (AMT) in amounts that yield a stoichiometric burn when combusted;
heating the combustion synthesis solution to a temperature sufficient to substantially remove the water and to initiate a self-sustaining combustion reaction to form a combustion product of WO 2 crystallites of a size less than 60 nm; and
heating the combustion product for less than 6 hours in a reducing atmosphere at a temperature lower than 850° C. to form the W powder.

2. The method of claim 1 , further comprising dissolving a nitrate reagent of an alloying metal in the combustion synthesis solution.

3. The method of claim 2 , wherein the oxidizer comprises the nitrate reagent.

4. The method of claim 1 , wherein the oxidizer comprises nitric acid.

5. The method of claim 1 , wherein the oxidizer comprises ammonium nitrate.

6. The method of claim 1 , wherein the fuel comprises glycine.

7. The method of claim 1 , further comprising cooling the combustion product to a temperature below 100° C. and then introducing an oxidizing gas to passivate the surface of W powder.

8. A method for synthesizing W nanocrystalline metal powders by a combustion reaction, the method characterized by the steps of:
forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and at least one base-soluble ammonium metatungstate (AMT) in amounts that yield a stoichiometric burn when combusted;
heating the combustion synthesis solution to a temperature sufficient to substantially remove the water and to initiate a self-sustaining combustion reaction to form a combustion product of WO 2 crystallites; and
heating the combustion product to a temperature below 850° C. in a reducing atmosphere to reduce the WO 2 crystallites to W nanocrystalline metal powder.

9. The method of claim 8 wherein the reducing comprises exposing the WO 2 crystallites to hydrogen.

10. The method of claim 9 wherein the reducing further comprises heating the WO 2 crystallites to a temperature between 600° C. and 800° C.

11. The method of claim 10 wherein the reducing further comprises rapidly heating the WO 2 crystallites to the temperature and rapidly cooling the W nanocrystalline metal powder to room temperature.

12. The method of claim 11 wherein the rapid heating and/or cooling is performed at a rate up to 100° C./min.

13. The method of claim 8 wherein the W nanocrystalline metal powder has an average particle size of less than 60 nm.

14. The method of claim 8 wherein the W nanocrystalline metal powder has an average particle size of less than 30 nm.

Assignees

• Frye John G
• Weil Kenneth Scott
• Lavender Curt A
• Kim Jin Yong
• Battelle Memorial Institute

Inventors

• Frye John G
• Weil Kenneth Scott
• Lavender Curt A
• Kim Jin Yong

Classifications

• C22C1/045

  Alloys based on refractory metals · CPC title

• C01G33/00

  Compounds of niobium · CPC title

• C01G41/02

  Oxides; Hydroxides · CPC title

• C22C1/058

  Chemistry & Metallurgy · mapped topic

• B22F1/0044

  Operations & Transport · mapped topic