Composite metal foam and methods of preparation thereof

Abstract

The present invention is directed to composite metal foams comprising hollow metallic spheres and a solid metal matrix. The composite metal foams show high strength, particularly in comparison to previous metal foams, while maintaining a favorable strength to density ratio. The composite metal foams can be prepared by various techniques, such as powder metallurgy and casting.

1 - 19 . (canceled) 
     
     
         20 . A method for providing protection against radiation energy comprising exposing a structure to radiation such that an energy absorption panel of the structure shields a first side thereof against radiation on a second side thereof, wherein the energy absorption panel comprises at least one layer including a composite metal foam comprising a plurality of hollow metallic spheres arranged with an interstitial space therebetween, the interstitial space being filled with a solid metal matrix. 
     
     
         21 . The method of  claim 20 , wherein the radiation is one or both of gamma radiation and neutron radiation. 
     
     
         22 . The method of  claim 20 , wherein the hollow metallic spheres have an average diameter of about 0.5 mm to about 20 mm. 
     
     
         23 . The method of  claim 22 , wherein the hollow metallic spheres have an average wall porosity of less than about 12% and an average wall thickness of about 1% to about 15% of the average sphere diameter. 
     
     
         24 . The method of  claim 20 , wherein the composite metal foam has a strength, evaluated as the plateau stress, of at least about 25 MPa. 
     
     
         25 . The method of  claim 20 , wherein the composite metal foam has a density of less than about 4 g/cm 3 . 
     
     
         26 . The method of  claim 20 , wherein the composite metal foam has an energy absorption of at least about 20 MJ/m 3 . 
     
     
         27 . The method of  claim 20 , wherein the hollow metallic spheres and the solid metal matrix are formed of the same metal or metal alloy. 
     
     
         28 . The method of  claim 20 , wherein the hollow metallic spheres and the solid metal matrix are formed of different metals or metal alloys. 
     
     
         29 . The method of  claim 20 , wherein the solid metal matrix is a sintered mass of metal particles. 
     
     
         30 . The method of  claim 20 , wherein the solid metal matrix is a solidified mass of molten metal. 
     
     
         31 . The method of  claim 20 , wherein the structure is an aerospace vehicle. 
     
     
         32 . The method of  claim 20 , wherein the structure is a nuclear fuel container. 
     
     
         33 . The method of  claim 20 , wherein the energy absorption panel comprises one or more further layers. 
     
     
         34 . A method for making a radiation shielding structure comprising forming the radiation shielding structure with an energy absorption panel that comprises at least one layer including a composite metal foam comprising a plurality of hollow metallic spheres arranged with an interstitial space therebetween, the interstitial space being filled with a solid metal matrix. 
     
     
         35 . The method of  claim 34 , wherein the structure effectively shields against one or both of gamma radiation and neutron radiation. 
     
     
         36 . The method of  claim 34 , wherein the hollow metallic spheres have an average diameter of about 0.5 mm to about 20 mm. 
     
     
         37 . The method of  claim 36 , wherein the hollow metallic spheres have an average wall porosity of less than about 12% and an average wall thickness of about 1% to about 15% of the average sphere diameter. 
     
     
         38 . The method of  claim 34 , wherein the composite metal foam has a strength, evaluated as the plateau stress, of at least 25 MPa. 
     
     
         39 . The method of  claim 34 , wherein the composite metal foam has a density of less than about 4 g/cm 3 . 
     
     
         40 . The method of  claim 34 , wherein the composite metal foam has an energy absorption of at least about 20 MJ/m 3 . 
     
     
         41 . The method of  claim 34 , wherein the hollow metallic spheres and the solid metal matrix are formed of the same metal or metal alloy. 
     
     
         42 . The method of  claim 34 , wherein the hollow metallic spheres and the solid metal matrix are formed of different metals or metal alloys. 
     
     
         43 . The method of  claim 34 , wherein the solid metal matrix is a sintered mass of metal particles. 
     
     
         44 . The method of  claim 34 , wherein the solid metal matrix is a solidified mass of molten metal 
     
     
         45 . The method of  claim 34 , wherein the structure is an aerospace vehicle. 
     
     
         46 . The method of  claim 34 , wherein the structure is a nuclear fuel container. 
     
     
         47 . The method of  claim 34 , wherein the energy absorption panel comprises one or more further layers. 
     
     
         48 . A radiation shielding structure prepared according to the method of  claim 34  so as to comprise at least one layer including a composite metal foam comprising a plurality of hollow metallic spheres arranged with an interstitial space therebetween, the interstitial space being filled with a solid metal matrix, the radiation shielding structure being effective shielding against one or both of gamma radiation and neutron radiation. 
     
     
         49 . A radiation shielding structure comprising an energy absorption panel with at least one layer that includes a composite metal foam comprising a plurality of hollow metallic spheres arranged with an interstitial space therebetween, the interstitial space being filled with a solid metal matrix, the energy absorption panel being effective shielding against one or both of gamma radiation and neutron radiation. 
     
     
         50 . The structure of  claim 49 , wherein the hollow metallic spheres have an average diameter of about 0.5 mm to about 20 mm. 
     
     
         51 . The structure of  claim 50 , wherein the hollow metallic spheres have an average wall porosity of less than about 12% and an average wall thickness of about 1% to about 15% of the average sphere diameter. 
     
     
         52 . The structure of  claim 49 , wherein the composite metal foam has a strength, evaluated as the plateau stress, of at least 25 MPa. 
     
     
         53 . The structure of  claim 49 , wherein the composite metal foam has a density of less than about 4 g/cm 3 . 
     
     
         54 . The structure of  claim 49 , wherein the composite metal foam has an energy absorption of at least about 20 MJ/m 3 . 
     
     
         55 . The structure of  claim 49 , wherein the hollow metallic spheres and the solid metal matrix are formed of the same metal or metal alloy. 
     
     
         56 . The structure of  claim 49 , wherein the hollow metallic spheres and the solid metal matrix are formed of different metals or metal alloys.