Method of creating porous structures by particle expansion
A process for producing a metal foam. The process includes mechanically working a metallic powder such that oxide particles and/or dissolved oxygen are finely dispersed within a metallic matrix of the metallic particles that make up the metallic powder. The mechanically worked metallic powder is then annealed in a reducing atmosphere, where the reducing atmosphere is an atmosphere that results in the reduction of oxide and/or dissolved oxygen into vapor or gas molecules such that intraparticle porosity is formed within the metallic matrix by conversion of the oxide particles and/or dissolved oxygen to create vapor or gas molecules.
1. A process for producing a metal foam comprising:
mechanically working a metallic powder such that oxide particles and/or dissolved oxygen are finely dispersed within a metallic matrix;
annealing the mechanically worked metallic powder in a reducing atmosphere, the reducing atmosphere being an atmosphere that results in the reduction of oxide and/or dissolved oxygen into vapor or gas molecules such that porosity is formed within the metallic matrix; and
forming the metal foam of the annealed metallic powder having intraparticle porosity formed by conversion of the oxide particles and/or dissolved oxygen to create vapor or gas molecules.
2. The process of claim 1 , wherein the metallic powder is a silver containing metallic powder.
3. The process of claim 1 , wherein the mechanical working is ball milling the metallic powder.
4. The process of claim 3 , wherein the metallic powder is a copper containing metallic powder.
5. The process of claim 4 , wherein the ball milling alloys copper particles with non-copper particles.
6. The process of claim 5 , wherein the non-copper particles are antimony particles.
7. The process of claim 3 , wherein the ball milling, is cryogenic ball milling.
8. The process of claim 3 , wherein the ball milling is room temperature ball milling.
9. The process of claim 1 , wherein the reducing atmosphere is an inert atmosphere.
10. The process of claim 1 , wherein the annealing occurs at a temperature less than or equal to 800° C.
11. The process of claim 9 , wherein the annealing occurs at a temperature less than or equal to 700° C.
12. The process of claim 10 , wherein the annealing occurs at a temperature less than or equal to 600° C.
13. The process of claim 1 , further comprising compacting the annealed ball milled metallic powder into a desired shape.
14. The process of claim 13 , wherein the desired shape has a porosity of at least 40%.
15. The process of claim 14 , wherein the porosity is at least 50%.
16. The process of claim 15 , wherein the porosity is at east 60%.
17. The process of claim 16 , wherein the porosity is at least 65%.
18. The process of claim 1 , further comprising the step of sintering the annealed mechanically worked metallic particles into a desired shape.
19. The process of claim 18 , wherein the desired shape has a metal foam structure and a porosity of the metal foam structure after foaming is at least 40%.
20. The process of claim 19 , wherein the porosity of the metal foam structure after foaming is at least 60%.