Methods for preparation of metallic and ceramic foam products and products made

Abstract

The present invention relates to the fabrication of low cost, in situ, porous metallic, ceramic and cermet foam structures having improved mechanical properties such as energy absorption and specific stiffness. Methods of fabricating the structures from compositions including ceramic and/or metallic powders are provided. The flowable compositions also include an immiscible phase that results in pores within the final structure. Furthermore, the structures may be shaped to have external porosity, such as with mesh-like structures.

1 . A method of fabricating a porous object comprising, in combination: 
 (a) mixing structure forming powder, binder, and a pore forming compound to provide a flowable composition, wherein the pore forming compound is generally immiscible with the structure forming powder and binder;    (b) gelling the flowable composition in a mold to form a composite object; and    (c) heating the composite object to a temperature and for a time effective for removing at least an amount of the pore forming compound to provide a sintered object having internal porosity.    
   
   
       2 . The method of  claim 1  wherein the structure forming powder and binder are mixed to form a generally uniform composition and wherein the pore forming compound is subsequently mixed with the composition.  
   
   
       3 . The method of  claim 1  wherein the pore forming compound is present in the flowable composition as discrete droplets of regular or irregular shape or combinations thereof.  
   
   
       4 . The method of  claim 1  wherein the structure forming powder is selected from the group consisting of metal powder, ceramic powder, cermet powder and combinations thereof.  
   
   
       5 . The method of  claim 1  wherein the pore forming compound is a polymeric compound.  
   
   
       6 . The method of  claim 5  wherein the pore forming compound is selected from the group consisting of polymethyl methacrylate, ethyl vinyl acrylate, polyethylene ethacrylate, poly-2-ethyl-2-oxazoline, polyethylene glycol, polystyrene, microcellulose, butrylactone, hexanedioldiacrylate, and combinations thereof.  
   
   
       7 . The method of  claim 1  wherein the flowable composition includes one or more compounds for enhancing the processability of the flowable composition.  
   
   
       8 . The method of  claim 1  wherein the flowable composition includes one or more compounds for enhancing the material properties of the sintered object.  
   
   
       9 . A structure formed by the method of  claim 1 .  
   
   
       10 . A method of fabricating a porous object comprising, in combination: 
 (a) mixing structure forming powder, binder, and microspheres to provide a flowable composition;    (b) gelling the flowable composition in a mold to form a composite object; and    (c) heating the composite object to a temperature and for a time effective for providing a sintered object having internal porosity.    
   
   
       11 . The method of  claim 10  wherein the structure forming powder and binder are mixed to form a generally uniform composition and wherein the microspheres are subsequently mixed with the composition.  
   
   
       12 . The method of  claim 10  wherein the structure forming powder is selected from the group consisting of metal powder, ceramic powder, cermet powder and combinations thereof.  
   
   
       13 . The method of  claim 10  wherein the microspheres are hollow ceramic micro spheres.  
   
   
       14 . The method of  claim 10  wherein the microspheres are polymeric microspheres and wherein at least an amount of the polymeric microspheres are removed during heating to provide pores within the object.  
   
   
       15 . The method of  claim 10  wherein the flowable composition includes one or more compounds for enhancing the processability of the flowable composition.  
   
   
       16 . The method of  claim 10  wherein the flowable composition includes one or more compounds for enhancing the material properties of the sintered object.  
   
   
       17 . A structure formed by the method of  claim 10.