# US 10,766,831 B2 · Stability of gas atomized reactive powders through multiple step in-situ passivation

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- Number: US 10,766,831 B2
- Document ID: US10766831B2
- Status: Granted
- Kind: B2
- Application number: 15/731,053
- Filed: 2017-04-11
- Published: 2017-11-23
- Granted: 2020-09-08
- Earliest claimed: 2012-04-12
- Assignees: Iowa State University Research Foundation, Inc.
- Applicants: Iowa State University Research Foundation, Inc.
- Inventors: Iver E. Anderson; Andrew D. Steinmetz; David J. Byrd
- Web page: https://patentgrep.com/patent/US10766831B2

## CPC

- C06B 45/30: the component base containing an inorganic explosive or an inorganic thermic component
- B22F 1/145: Chemical treatment, e.g. passivation or decarburisation
- B22F 9/082: {atomising using a fluid (using centrifugal force B22F9/10)}
- B22F 9/16: using chemical processes
- B22F 2009/0844: {in controlled atmosphere}
- B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy
- C06B: EXPLOSIVES OR THERMIC COMPOSITIONS (blasting F42D); MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES (compounds in general C01, C07 or C08; {demolition agents based on cementitious or like materials C04B41/0009})
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER

## 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.

## Claims

### 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.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

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