Apparatus for producing refractory compound powders

Abstract

A gas atomization apparatus is disclosed for producing high purity fine refractory compound powders. After the system reaches high vacuum, a first stage inert atomizing gas breaks superheated metal melt into droplets and a second stage reactive atomizing gas breaks the droplets further into ultrafine droplets while reacts with them to form refractory compound powders. The first stage atomizing gas is inert gas able to break up melt into droplets and prevent crust formation on the nozzle front. A reaction time enhancer is arranged at bottom of reaction chamber to furnish a reactive gas flow in a reverse direction of the falling droplets and powders. Under the reverse gas flow, the falling droplets and powders change moving direction and travel longer distance in reaction chamber to increase reaction time. This apparatus can produce refractory powders with ultrahigh purity and uniform powder size while maintain high process energy efficiency.

Our claims are defined as below: 
     
         1 . A two or more stage atomization apparatus with reaction time enhancer for producing ultra-fine refractory compound powders from a metal composition containing one or more reactive elemental metals, and the said apparatus comprising of:
 a) A heating and first-stage atomizing means to provide a stream of super-heated metal droplets. The atomizing fluid of the first stage is mostly of inert gas to prevent formation of high melting point crust at the openings of source spraying nozzle, so the nozzle would not be clogged;   b) A second-stage atomizing means by directing diluted reactive gas into said second-stage atomization chamber to impinge the said metal liquid droplets from the first stage atomization into ultra fine particles, and the said reactive gas also reacts with liquid metal droplets and transfers the metal droplets into compound powders.   c) The said reaction time enhancer by providing a flow of reactive gas in different flow direction of the droplets and powders, so the said metal droplets can change traveling direction, or even travel back and forth, in the reaction chamber, to increase the reaction time between the said metal droplets and the said reactive gases.   
     
     
         2 . The apparatus as set forth in  claim 1  wherein the atomization and reaction chambers must be pumped into high vacuum state before atomization for removing contaminating gas species, to make sure the said refractory compound powders not be contaminated. 
     
     
         3 . The apparatus as set forth in  claim 1  wherein the said source metal melting unit comprised of heating device selected from the group of arc spray device, induction crucible device, gas combustion spray device, induction heating spray device and plasma heating device, or combinations thereof. 
     
     
         4 . The apparatus as set forth in  claim 1  wherein the said first stage atomization gas is inert gas or mainly of inert gas to prevent clogging of spray nozzle by formation of high-melting point refractory compound crust between the superheated liquid metal and reactive gas at the nozzle front ends. 
     
     
         5 . The apparatus as set forth in  claim 1  wherein the said second stage atomization functions to break the first stage metal droplets further into ultra fine metal droplets and to transfer the said ultra fine metal droplets into refractory compound powders with the said reactive gas. The said reactive gas may be diluted with inert gases. 
     
     
         6 . The apparatus as set forth in  claim 1  wherein the said reactive gas in the second stage atomization is selected according to target compound powders from a group of gases consisting of hydrogen, carbon, nitrogen, oxygen, chlorine, fluorine, boron, sulfur etc and combinations thereof. 
     
     
         7 . The apparatus as set forth in  claim 1  wherein a reaction time enhancer is provided to increase the reaction time between the said metal droplets and the said reactive gas in the reaction chamber. 
     
     
         8 . The reaction time enhancer of  claim 7  wherein it extends the reaction time by providing a reactive gas flow in a different or even reverse traveling direction of the said droplets and powders, thus to drive the said droplets and powders to move back and forth in the reaction chamber. 
     
     
         9 . The reaction time enhancer of  claim 7  wherein the arrangement of the said reaction time enhancer in the reaction chamber can be selected from various options of location and orientation, and these options share the similarity that the said reactive gas flow is in a different or even reverse direction of the said droplets and powders. 
     
     
         10 . The reaction time enhancer of  claim 7  wherein the extent of time enhancement can be adjusted through modification of injection nozzle parameters such as size, shape and spraying angle relative to the said droplet and powder travel direction.