Purification process

Abstract

A method for purifying metal M 1 particles manufactured by an electrochemical reduction process, the method comprising the steps of introducing the metal M 1 particles into a heat source ( 13 ) at a temperature substantially equal to or higher than the melting point of M 1 so as to cause vaporisation of some or substantially all of the contaminating impurities present, removing the vaporised impurities from the vicinity of the particles, and cooling the purified metal M 1 particles. The purified particles can be used directly in lower temperature powder metallurgy processes and have a fully dense spherical particle morphology, imparting good flowability. The purification process can also be incorporated as an integral stage of sheet or stock production processes based on particle feedstocks that have been produced by electrochemical reduction.

1 . A method for purifying metal M 1  particles manufactured by an electrochemical reduction process, the method comprising the steps of:
 introducing the metal M 1  particles into a heat source at a temperature substantially equal to or higher than the melting point of M 1  so as to cause vaporisation of some or substantially all of the contaminating impurities present;   removing the vaporised impurities from the vicinity of the particles;   cooling the purified metal M 1  particles.   
     
     
         2 . A method for the manufacture of a metal alloy article containing a metal M 1 , comprising the steps of:
 electrochemically reducing a source of a compound of the general formula M 1 X to remove substantially all of element X and provide powder particles consisting substantially of metal M 1 ;   introducing the metal powder M 1  into a heat source at a temperature substantially equal to or higher than melting point of M 1  for a period of time sufficient to cause vaporisation of a significant proportion of the one or more impurities;   removing the vaporised impurities;   cooling the purified metal M 1  powder; and   mixing the purified M 1  powder with powder of other alloy components and performing a powder metallurgy process on the mixture to form the alloyed article.   
     
     
         3 . A method as claimed in  claim 1  wherein the particles are in the form of a powder. 
     
     
         4 . A method as claimed in  claim 2  wherein the powder metallurgy process involves powder sintering. 
     
     
         5 . A method as claimed in  claim 2  wherein the powder metallurgy process involves powder pressing or forging. 
     
     
         6 . A method as claimed in  claim 1  wherein the heat source is selected from any one of a plasma torch, a laser, an electric arc, an induction coil or a tube furnace. 
     
     
         7 . A method as claimed in  claim 1 , wherein the method is conducted in a controlled atmosphere. 
     
     
         8 . A method as claimed in  claim 1 , wherein a further purification step comprises water or acid washing and drying of the powder. 
     
     
         9 . A method as claimed in  claim 1  conducted in apparatus comprising a heat source, collection means for collecting the purified particles, and separate collection means for collecting the impurities. 
     
     
         10 . A method as claimed in  claim 1  wherein the particles are suspended in mid-air and/or permitted to free fall past or within the heat source. 
     
     
         11 . A method as claimed in  claim 10  wherein the free fall distance from the heat source is sufficiently long to allow any M 1  melted by the heat source to re-solidify before collection. 
     
     
         12 . A method as claimed in  claim 6  wherein the heat source is a plasma torch and the step of removing the vaporised impurities involves allowing the impurities to be swept away by the hot gas flow from the torch. 
     
     
         13 . A method as claimed in  claim 1  wherein the step of removing the vaporised impurities involves condensing the vaporised impurities on cold collector plates positioned adjacent the heat source and disposing of the condensed impurities. 
     
     
         14 . A method as claimed in  claim 1  wherein the temperature of the heat source is around or above the melting point, but below the boiling point of M 1 . 
     
     
         15 . (canceled) 
     
     
         16 . A method as claimed in  claim 1  wherein M 1  comprises titanium. 
     
     
         17 . A method as claimed in  claim 2  wherein M 1 X is titanium oxide TiO 2 . 
     
     
         18 . A method as claimed in  claim 1  wherein the impurities comprise one or more of magnesium, calcium and calcium chloride. 
     
     
         19 .- 30 . (canceled)