Method for manufacturing fine tungsten powder

Abstract

A method for finely powdering tungsten powder, which includes electrolytically oxidizing tungsten powder while stirring in an aqueous mineral-acid solution to form an oxide film in the surface of the tungsten powder and removing the oxide film with an alkaline aqueous solution; a method for producing tungsten powder to obtain fine tungsten powder by a process including the above method for finely powdering; and a tungsten powder having an average particle size of 0.04 to 0.4 μm, in which the dMS value (product of an average particle size d (μm), true density M (g/cm 3 ) and BET specific surface area S (m 2 /g)) is within the range of 6±0.4.

1 . A method for finely powdering tungsten powder, comprising electrolytically oxidizing tungsten powder while stirring in an electrolytic solution to form an oxide film in the particle surface of the tungsten powder and removing the oxide film with an alkaline aqueous solution. 
     
     
         2 . The method for finely powdering tungsten powder as claimed in  claim 1 , wherein the removal of the oxide film with an alkaline aqueous solution includes mechanically removing the reaction product in the particle surface of the tungsten powder. 
     
     
         3 . The method for finely powdering tungsten powder as claimed in  claim 1 , wherein the electrolytic solution is an aqueous solution of mineral acid. 
     
     
         4 . The method for finely powdering tungsten powder as claimed in  claim 3 , wherein the mineral acid is selected from phosphoric acid, nitric acid, hydrochloric acid, boric acid and sulfuric acid. 
     
     
         5 . The method for finely powdering tungsten powder as claimed in  claim 4 , wherein the mineral acid is phosphoric acid or boric acid. 
     
     
         6 . A method for finely powdering tungsten powder, comprising dispersing tungsten powder in an aqueous solution containing an oxidizing agent to form an oxide film in the surface of the tungsten powder, removing the oxide film with an alkaline aqueous solution, followed by the method claimed in  claim 1 . 
     
     
         7 . A method for producing fine tungsten powder, comprising obtaining tungsten powder having an average particle size of 0.04 to 0.4 μm by a process including the method claimed in  claim 1 . 
     
     
         8 . A method for producing fine tungsten powder, comprising obtaining tungsten powder, in which the product of an average particle size (μm), true density (g/cm 3 ) and BET specific surface area (m 2 /g) is within the range of 6±0.4, by a process including the method claimed in  claim 1 . 
     
     
         9 . A tungsten powder having an average particle size of 0.04 to 0.4 μm, in which the dMS value (product of an average particle size d (μm), true density M (g/cm 3 ) and BET specific surface area S (m 2 /g)) is within the range of 6±0.4.