Stability of gas atomized reactive powders through multiple step in-situ passivation

Patent metadata

Field	Value
Publication number	US-10766831-B2
Application number	US-201715731053-A
Country	US
Kind code	B2
Filing date	Apr 11, 2017
Priority date	Apr 12, 2012
Publication date	Sep 8, 2020
Grant date	Sep 8, 2020

Abstract

A method for gas atomization of oxygen-reactive reactive metals and alloys wherein the atomized particles are exposed as they solidify and cool in a very short time to multiple gaseous reactive agents for the in-situ formation of a protective reaction film on the atomized particles. The present invention is especially useful for making highly pyrophoric reactive metal or alloy atomized powders, such as atomized magnesium and magnesium alloy powders. The gaseous reactive species (agents) are introduced into the atomization spray chamber at locations downstream of a gas atomizing nozzle as determined by the desired powder or particle temperature for the reactions and the desired thickness of the reaction film.

First claim

We claim:

1. Atomized powder particles comprising an oxygen-reactive metallic material wherein the powder particles have a protective layer that is formed on outer particle surfaces and that comprises a reaction product of a metal of the metallic material and a first reactive species and wherein the reaction product further includes an amount of a second reactive species to increase thermal ignition temperature of the atomized particles wherein the depth of particle penetration of the first reactive species is greater than the depth of penetration of the second reactive species such that the second reactive species is present only within the protective layer and wherein a maximum concentration of the second reactive species is present at an outer region of the protective layer as a result of sequential exposure of the atomized particles first to the first reaction species and thereafter to the second reactive species.

2. The particles of claim 1 wherein the metallic material comprises magnesium metal or a magnesium alloy.

3. The particles of claim 1 wherein the first reactive Species comprises oxygen.

4. The particles of claim 1 wherein the second reactive species comprises fluorine.

5. The particles of claim 1 wherein the reaction product comprises magnesium oxide that includes fluorine to a depth of penetration of the oxide of about 40 nm or less that is less than the thickness of the oxide.

6. The particles of claim 1 having an average diameter of 500 microns or less.

Assignees

• Univ Iowa State Res Found Inc

Inventors

• Anderson Iver E
• Steinmetz Andrew D
• Byrd David J

Classifications

• B22F1/145

  Chemical treatment, e.g. passivation or decarburisation · CPC title

• B22F2009/0844

  in controlled atmosphere · CPC title

• B22F9/16

  using chemical processes · CPC title

• C06B45/30 Primary

  the component base containing an inorganic explosive or an inorganic thermic component · CPC title

• B22F9/082

  atomising using a fluid (using centrifugal force B22F9/10) · CPC title