Electrolytic reduction of metal oxides such as titanium dioxide and process applications

Abstract

A method of removing oxygen from a solid metal, metal compound or semi-metal M1O by electrolysis in a fused salt of M2Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface and that oxygen dissolves in the electrolyte M2Y and wherein, M1O is in the form of (sintered) granules or is in the form of a powder which is continuously fed into the fused salt. Also disclosed is a method of producing a metal foam comprising the steps of fabricating a foam-like metal oxide perform, removing oxygen from said foam structured metal oxide prefrom by electrolysis in a fused salt of M2Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface. The method is advantageously applied for the production of titanium from Ti-dioxide.

1 .- 4 . (canceled)  
     
     
         5 . A feedstock for the electrolytic reduction of a metal oxide, semi-metal oxide or a mixture of oxides of appropriate alloying elements, said feedstock comprising a sintered mass of a bimodal mixture of said oxide particles of size greater than 20 microns and finer particles of less than 7 microns.  
     
     
         6 . A feedstock as claimed in  claim 5 , wherein said finer particles make up between 5 and 70% of the sintered block by weight.  
     
     
         7 . A feedstock as claimed in  claim 6 , wherein said finer particles make up between 10 and 55% of the sintered block by weight.  
     
     
         8 . A method of producing a metal matrix composite comprising: 
 a) blending particulate reinforcement with metal oxide or semi-metal oxide powder to provide a mixture;    b) sintering said mixture; and    c) removing oxygen from sintered mixture by the electrolysis in a fused salt M2Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface and that oxygen dissolves in the electrolyte M2Y.    
     
     
         9 . A method of producing a fibre reinforced metal matrix composite comprising: 
 (a) coating reinforcement fibres with a metal oxide or semi-metal oxide/binder slurry to produce a pre-form; and    (b) removing oxygen from the preform by the electrolysis in a fused salt M2Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface and that oxygen dissolves in the electrolyte M2Y.    
     
     
         10 . A method of producing a metal or semi-metal or alloy component comprising: 
 (a) providing a ceramic facsimile of the component from the metal oxide or semi-metal oxide or a mixture of oxides of appropriate alloying elements; and    (b) removing oxygen from facsimile by the electrolysis in a fused salt M2Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface and that oxygen dissolves in the electrolyte M2Y.    
     
     
         11 .- 13 . (canceled)  
     
     
         14 . A method of producing a metal or semi-metal foam comprising the steps of fabricating a foam-like metal oxide or semi-metal oxide preform, removing oxygen from said foam structured metal oxide preform by electrolysis in a fused salt M 2 Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface and that oxygen dissolves in the electrolyte M2Y.  
     
     
         15 . A method as claimed in  claim 14  wherein said metal oxide or semi--metal oxide preform is produced by infiltrating a polymeric foam with metal oxide or semi-metal oxide slip which is then dried and fired.  
     
     
         16 . A method as claimed in  claim 15  wherein the metal oxide or semi-metal oxide preform is produced by the steps of: 
 (a) mixing the metal oxide or semi-metal oxide powder with organic foaming agents so as to evolve a foaming gas;    (b) curing to give a solidified foam; and    (c) firing the foam to remove the organic material.    
     
     
         17 . A method as claimed in  claim 15  wherein said metal oxide or semi-metal oxide preform is sintered metal oxide or semi-metal oxide granules.  
     
     
         18 . A method according to  claim 8  wherein M 1  s selected from the group comprising Ti, Zr, Hf, Al, Mg, U, Nd, Mo, Cr, Nb, Ge, P, As, Si, Sb, Sm or any alloy thereof.  
     
     
         19 . A method according to  claim 8  wherein M 2  is Ca, Ba, Li, Cs, Sr.  
     
     
         20 . A method according to  claim 8  wherein Y is Cl.  
     
     
         21 .- 22 . (canceled)