Magnesium-Based Alloy Foam

Abstract

Morphology, microstructure, compressive behavior, and biocorrosive properties of magnesium or magnesium alloy foams allow for their use in biodegradable biomedical, metal-air battery electrode, hydrogen storage, and lightweight transportation applications. Magnesium or Mg alloy foams are usually very difficult to manufacture due to the strong oxidation layer around the metallic particles; however, in this invention, they can be synthesized via a camphene-based freeze-casting process with the addition of graphite powder using precisely controlled heat-treatment parameters. The average porosity ranges from 45 to 85 percent and the median pore diameter is about a few tens to hundreds of microns, which are suitable for bio and energy applications utilizing their enhanced surface area. This invention based on powder-slurry freeze-casting method using camphene as a volatile solvent is also applicable for other metal foams such as iron, copper, or others to produce three-dimensional metal foams with high strut connectivity.

This invention claimed is: 
     
         1 . A composition of matter comprising a three dimensionally connected magnesium or magnesium alloy foams of at least one of Mg—Al, Mg—Zn, Mg—Al, Mg—Mn, Mg—Si, Mg—Cu, Mg—Zr, or Mg-rare earth elements, or any combination of these. 
     
     
         2 . The composition of  claim 1  wherein the foam's pore structure has a porosity of about 45 percent to about 85 percent with an open pore structure. 
     
     
         3 . The composition of  claim 1  wherein the magnesium or magnesium alloy green-body foam has a sintering process comprising (i) burning of chemical additives (binder and dispersant) at about 300 degrees Celsius to about 450 degrees Celsius for about 3 hours to about 5 hours and (ii) sintering of magnesium or magnesium alloy green-body foam at 500 degrees Celsius to 650 degrees Celsius for about 3 hours to about 10 hours in argon atmosphere. 
     
     
         4 . A method comprising:
 mixing magnesium or magnesium alloy powder in a solution of liquid camphene to obtain a suspension solution;   stirring or sonicating the suspension solution in water bath at above 40 degrees Celsius to obtain a slurry solution;   freeze casting the camphene-based magnesium or magnesium alloy powder slurry solution;   drying, via sublimation, camphene, a frozen green-body foam, by placing the frozen green-body foam; and   after drying, sintering the frozen green-body foam comprising the magnesium or magnesium alloy.   
     
     
         5 . The method of  claim 4  comprising:
 after sintering, a three dimensionally connected magnesium or magnesium alloy foam is produced of at least one of Mg—Al, Mg—Zn, Mg—Al, Mg—Mn, Mg—Si, Mg—Cu, Mg—Zr, or Mg-rare earth element, or any combination thereof. 
 
     
     
         6 . The method of  claim 5  wherein the sintering the frozen green-body foam comprising the magnesium or magnesium alloy comprises a sintering process comprising
 burning of the binder and dispersant at about 300 degrees Celsius to about 450 degrees Celsius for about 3 hours to about 5 hours, and sintering of frozen green-body foam at about 500 degrees Celsius to about 650 degrees Celsius for about 3 hours to about 10 hours. 
 
     
     
         7 . A method comprising:
 mixing magnesium or magnesium alloy powder having a particle size from about 36 microns to 45 microns in a solution of camphene to obtain a suspension solution;   stirring or sonicating the suspension solution in a water bath to obtain a slurry solution;   freeze casting the camphene-based magnesium or magnesium alloy powder slurry solution;   drying, via sublimation, camphene, a frozen green-body foam; and   after drying, sintering the frozen green-body foam comprising the magnesium or magnesium alloy.   
     
     
         8 . The method of  claim 7  wherein the sintering comprises burning of the binder and dispersant at about 300 degrees Celsius to about 450 degrees Celsius for about 3 hours to about 5 hours. 
     
     
         9 . The method of  claim 8  wherein the sintering comprises sintering of frozen green-body foam at about 500 degrees Celsius to about 650 degrees Celsius for about 3 hours to about 10 hours in an argon atmosphere. 
     
     
         10 . The method of  claim 8  wherein after sintering, a three dimensionally connected magnesium or magnesium alloy foam is produced of at least one of Mg—Al, Mg—Zn, Mg—Al, Mg—Mn, Mg—Si, Mg—Cu, Mg—Zr, or Mg-rare earth element, or any combination thereof. 
     
     
         11 . The method of  claim 7  wherein the binder is polystyrene and the dispersant is oligometric polyester powder. 
     
     
         12 . The method of  claim 7  comprising:
 mechanically mixing powders of the magnesium and another element to obtain a uniform particle mixing before mixing with liquid caphene, binder, and dispersant when the powders used are not prealloyed. 
 
     
     
         13 . The method of  claim 7  comprising:
 drying the slurry solution in a vacuum at a temperature from about −80 degrees Celsius to about room temperature. 
 
     
     
         14 . The method of  claim 7  comprising:
 sintering the frozen green-body foam in an alumina crucible filled with graphite powder having a mean particle size of about 1 micron to about 30 microns. 
 
     
     
         15 . The method of  claim 7  comprising:
 freezing the slurry solution at a temperature from about −80 degrees Celsius to about 40 degrees Celsius. 
 
     
     
         16 . The method of  claim 15  wherein the magnesium or magnesium alloy foam comprises a three-dimensional pore structure with uniformly distributed pores having diameters from about 1 micron to about 300 microns. 
     
     
         17 . The method of  claim 7  wherein the suspension solution comprises about 3 weight-percent binder to about 6 weight-percent binder and about 1 weight-percent dispersant to about 3 weight-percent dispersant. 
     
     
         18 . The method of  claim 7  wherein the drying the frozen green-body foam comprises using a freeze dryer. 
     
     
         19 . The method of  claim 7  wherein the drying the frozen green-body foam comprises using an air hood. 
     
     
         20 . The method of  claim 7  wherein the binder is polystyrene and the dispersant is oligometric polyester powder.