Metal and alloy powders and powder fabrication

Abstract

A precursor powder comprising a metal compound is formed into a sample for electro-deoxidation, for example by slip-casting. The sample is then immersed in a melt comprising a molten salt and a cathodic potential applied to remove non-metal species from the precursor powder by electro-deoxidation and dissolution in the melt. This typically forms a metallic sample which can be fragmented to form a metallic powder. In a second aspect of the invention a powdered feed material is formed into a shaped precursor and more extensive electro-deoxidation carried out so as to form a near-net shaped product.

1 . A method for producing a metallic powder, comprising the steps of: 
 treating by electro-deoxidation a precursor powder comprising a compound (M 1 X) between a metal (M 1 ) and an non-metal species (X), the precursor powder forming a cathode contacting a melt comprising a fused salt (M 2 Y), under conditions such that the non-metal species dissolves in the melt; and    processing a product of the electro-deoxidation as required to form the metallic powder.    
     
     
         2 . A method according to  claim 1 , in which the electro-deoxidation is Carried out under conditions whereby a cathodic potential less than a potential for the deposition of a cation (M 2 ) from the melt is applied to the cathode.  
     
     
         3 . A method according to  claim 1 , in which the melt comprises a mixture of salts, including two or more cations (M 2 ), and the electro-deoxidation is carried out under conditions whereby a cathodic potential less than a potential for the deposition of any cation (M 2 ) from the melt is applied to the cathode.  
     
     
         4 . A method according to  claim 1 ,  2  or  3 , in which the precursor powder is a conductor and is used as the cathode.  
     
     
         5 . A method according to  claim 1 ,  2  or  3 , in which the precursor powder is an insulator and is used in contact with a conductor to form the cathode.  
     
     
         6 . A method according to any preceding claim, in which electro-deoxidation is carried out at a temperature of 700-1000° C.  
     
     
         7 . A method according to any preceding claim, in which the precursor powder comprises particles between 0.05 and 20 μm in size.  
     
     
         8 . A method according to any of  claims 1  to  6 , in which the precursor powder comprises particles between 0.25 and 2 μm in size.  
     
     
         9 . A method according to any preceding claim, in which the metallic powder comprises particles between 1 and 30 μm in size.  
     
     
         10 . A method according to any preceding claim, in which the fused salt comprises as a cation species (M 2 ) Ca, Ba, Li, Cs and/or Sr.  
     
     
         11 . A method according to any preceding claim, in which the fused salt comprises as an anion (Y) Cl or F.  
     
     
         12 . A method according to any preceding claim, in which the non-metal species comprises O, S, C or N.  
     
     
         13 . A method according to any preceding claim, in which the metal (M 1 ) comprises Ti, Si, Ge, Zr, Hf, Sm, U, Al, Mg, Nd, Mo, Cr or Nb, V, Ta, Mb, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Be, Sr, Ga, In, Tl, lanthanides or actinides, or an alloy thereof.  
     
     
         14 . A method according to any preceding claim, in which the precursor powder is formed into a sample for electro-deoxidation by powder processing techniques, for example slip-casting or compaction, and the product of the electro-deoxidation is ground or fragmented to form the metallic powder.  
     
     
         15 . A method according to  claim 14 , in which the formation of the precursor powder comprises sintering.  
     
     
         16 . A method according to any preceding claim, in which the precursor powder comprises a mixture or solid solution of one or more metal compounds, and optionally one or more metals or alloys.  
     
     
         17 . A metallic powder produced according to a method as defined in any preceding claim.  
     
     
         18 . An apparatus for carrying out the method defined in any preceding claim.  
     
     
         19 . A method for forming a near net-shaped product, comprising the steps of: 
 forming a shaped precursor from a powdered feed material comprising a compound (M 1 X) between a metal (M 1 ) and a non-metal species (X);    treating the precursor by electro-deoxidation, the precursor forming a cathode contacting a melt comprising a fused salt (M 2 Y) under conditions such that the non-metal species dissolves in the melt, the electro-deoxidation being carried out for a sufficiently long time and/or at a sufficiently high temperature to form interconnections between metallic powder particles produced by the electro-deoxidation and to produce the near net-shaped product strong enough for further processing.    
     
     
         20 . A method according to  claim 19 , in which the electro-deoxidation is carried out under conditions whereby a cathodic potential less than a potential for the deposition of a cation (M 2 ) from the melt is applied to the cathode.  
     
     
         21 . A method according to  claim 19 , in which the melt comprises a mixture of salts, including two or more cations (M 2 ), and the electro-deoxidation is carried out under conditions whereby a cathodic potential less than a potential for the deposition of any cation (M 2 ) from the melt is applied to the cathode.  
     
     
         22 . A method according to  claim 19 ,  20  or  21 , in which the precursor is a conductor and is used as the cathode.  
     
     
         23 . A method according to  claim 19 ,  20  or  21 , in which the precursor powder is an insulator and is used in contact with a conductor to form the cathode.  
     
     
         24 . A method according to any of  claims 19  to  23 , in which electro-deoxidation is carried out at a temperature of 700-1000° C.  
     
     
         25 . A method according to any of  claims 19  to  24 , in which the powdered feed material comprises particles between 0.05 and 20 μm in size.  
     
     
         26 . A method according to any of  claims 19  to  24 , in which the powdered feed material comprises particles between 0.25 and 2 μm in size.  
     
     
         27 . A method according to any of  claims 19  to  26 , in which the fused salt comprises as a cation species (M 2 ) Ca, Ba, Li, Cs and/or Sr.  
     
     
         28 . A method according to any of  claims 19  to  27 , in which the fused salt comprises as an anion (Y) Cl or F.  
     
     
         29 . A method according to any of  claims 19  to  28 , in which the non-metal species comprises O, S, C or N.  
     
     
         30 . A method according to any of  claims 19  to  29 , in which the metal (M 1 ) comprises Ti, Si, Ge, Zr, Hf, Sm, U, Al, Mg, Nd, Mo, Cr, Nb, V, Ta, Mb, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Be, Sr, Ga, In, Tl, lanthanides or actinides, or an alloy thereof.  
     
     
         31 . A method according to any of  claims 19  to  30 , in which the powdered feed material is formed into a sample for electro-deoxidation by slip-casting or compaction.  
     
     
         32 . A method according to any of  claims 19  to  31 , in which the formation of the precursor comprises sintering.  
     
     
         33 . A method according to any of  claims 19  to  32 , in which the powdered feed material comprises a mixture or solid solution of one or more metal compounds, and optionally one or more metals or alloys.  
     
     
         34 . A method according to any of  claims 19  to  33 , in which the near net-shaped product is subsequently treated by sintering and/or machining.  
     
     
         35 . A near net-shaped product formed by a method as defined in any of  claims 19  to  34 .  
     
     
         36 . An apparatus for producing a near net-shaped product as defined in  claim 35.