Apparatus and method for generating fine particulates

Abstract

A method and apparatus to provide charges to a flow, or stream, of fluent material droplets, or a planar array of parallel droplet streams of fluent material, wherein said fluent material may be electrically conductive, to form smaller droplets thereof is described. In one embodiment, an apparatus is configured to generate a stream, such as a coaxial stream, of droplets of fluent material that are electrically isolated, about uniform in size, and are spaced about equidistantly apart. In one aspect, an electron emissive device is employed to irradiate the stream of droplets to inject charges therein. The charges atomize the droplets into smaller droplets to form a plume of the fluent material particulates having an approximately uniform size. In some embodiments, the individual particulates of fluent material freeze, thereby forming powder particulates having predictable characteristics.

1 . An apparatus for generating a plurality of particulates comprising: 
 at least one dispensing device for generating at least one of the group consisting of a stream of droplets, a coaxial stream of droplets, a planar array of parallel droplet streams, and combinations thereof; and    at least one charge injection device adjacent a discharge of said at least one dispensing device for inducing at least one charge to at least a portion of said plurality of said droplets dispensed from said at least one dispensing device;    wherein said at least one charge is of sufficient magnitude to initiate electrostatic atomization as per at least one of the group consisting of an equilibrium spray theory, a Coulomb bursting process, and combinations thereof.    
   
   
       2 . An apparatus according to  claim 1 , wherein said droplets are formed from at least one of the group consisting of Wood's metal, Inconel®, cobalt, chromium, nickel, titanium, Octoil®, alloys, superalloys, refractory metals, a high temperature liquid metal, a high temperature fluent material, and combinations thereof.  
   
   
       3 . An apparatus according to  claim 1 , wherein said droplets are at least one of the group consisting of electrically isolated from each other, substantially uniform in size, about equidistantly separated, and combinations thereof.  
   
   
       4 . An apparatus according to  claim 1 , wherein said electrostatic atomization of said droplets causes at least a portion of said particulates to disperse.  
   
   
       5 . An apparatus according to  claim 1 , wherein said electrostatic atomization of said droplets results in said plurality of said particulates having approximately uniform predetermined diameters.  
   
   
       6 . An apparatus according to  claim 1 , wherein said particulates are formed of at least one of the group consisting of powder, fluent materials, and combinations thereof.  
   
   
       7 . An apparatus according to  claim 1 , wherein said inducing at least one charge to said plurality of said droplets includes independently irradiating each of said droplets with said charges.  
   
   
       8 . An apparatus according to  claim 1 , wherein said at least one dispensing device comprises the sub-components of: 
 at least one reservoir for holding or storing a fluent material; and    at least one stream generator coupled to said reservoir for receiving said fluent material from said reservoir and generating at least one of the group consisting of said stream of droplets, said coaxial stream of droplets, said planar array of parallel droplet streams, and combinations thereof.    
   
   
       9 . An apparatus according to  claim 8 , wherein said at least one stream generator controls a gravitational flow of said fluent material from said reservoir to create said at least one of the group consisting of said stream of droplets, said coaxial stream of droplets, said planar array of parallel droplet streams, and combinations thereof.  
   
   
       10 . An apparatus according to  claim 1 , said apparatus further comprising: 
 at least one vacuum source coupled to said at least one dispensing device for evacuating an area surrounding a fluent material contained in said dispensing device.    
   
   
       11 . An apparatus according to  claim 1 , said apparatus further comprising: 
 at least one pressurization source coupled to said at least one dispensing device for pressurizing an area surrounding a fluent material contained in said dispensing device.    
   
   
       12 . An apparatus according to  claim 1 , said apparatus further comprising: 
 at least one heating assembly for maintaining a fluent material contained in said at least one dispensing device at or near a predetermined temperature setpoint.    
   
   
       13 . An apparatus according to  claim 12 , wherein said heating assembly includes at least one of the group consisting of a heater, a heat transfer liquid, an insulating jacket, and combinations thereof.  
   
   
       14 . An apparatus according to  claim 1 , wherein an atmosphere surrounding said apparatus is at least one of the group consisting of dry nitrogen containing less than one percent oxygen, an atmosphere maintained at a vacuum pressure, sulfur hexafluoride, and combinations thereof.  
   
   
       15 . An apparatus according to  claim 1 , said apparatus further comprising: 
 at least one stream heater for heating at least one of said droplets, a fluent material contained within said at least one dispensing device, and combinations thereof;    wherein said heating creates or retains said droplets in molten form prior to said inducing of said at least one charge.    
   
   
       16 . An apparatus according to  claim 1 , 
 wherein said at least one charge injection device includes at least one device for generating at least one beam of charged particles; and    wherein said at least one beam of charged particles induces said charge to said at least a portion of said droplets.    
   
   
       17 . An apparatus according to  claim 16 , wherein said charged particles are free electrons.  
   
   
       18 . An apparatus according to  claim 16 , wherein said at least one device for generating at least one beam of charged particles is an electron gun.  
   
   
       19 . An apparatus according to  claim 1 , 
 wherein said at least one charge injection device includes at least one electrode; and    wherein said at least one electrode provides an electric field for performing at least one of the group consisting of attracting at least one of said charges, accelerating at least one of said charges, directing at least one of said charges, and combinations thereof.    
   
   
       20 . An apparatus according to  claim 1 , said apparatus further comprising: 
 at least one barrier positioned between said at least one charge injection device and said at least one of the group consisting of said stream of droplets, said coaxial stream of droplets, said planar array of parallel droplet streams, and combinations thereof;    wherein said at least one barrier protects said at least one charge injection device from contamination caused by at least a portion of said droplets, at least a portion of said particulates, and combinations thereof.    
   
   
       21 . An apparatus according to  claim 20 , wherein said at least one barrier is a charge permeable membrane.  
   
   
       22 . An apparatus according to  claim 20 , said apparatus further comprising: 
 at least one electrode;    wherein said droplets are induced with said charge while passing between said at least one barrier and said at least one electrode.    
   
   
       23 . An apparatus according to  claim 1 , said apparatus further comprising: 
 at least one electrode;    wherein said droplets are induced with said charge while passing between said at least one charge injection device and said at least one electrode.    
   
   
       24 . An apparatus according to  claim 1 , wherein said at least one charge injection device is configured to minimize inter-droplet shielding.  
   
   
       25 . A method for generating a plurality of particulates comprising: 
 receiving at least one fluent material;    generating at least one of the group consisting of a stream of droplets, a coaxial stream of droplets, a planar array of parallel droplet streams, and combinations thereof from said fluent material;    inducing at least one charge to a plurality of said droplets, said charge having sufficient magnitude to initiate electrostatic atomization as per at least one of the group consisting of an equilibrium spray theory, a Coulomb bursting process, and combinations thereof; and    forming said plurality of particulates via said electrostatic atomization;    wherein said plurality of said particulates have approximately uniform, predetermined diameters.    
   
   
       26 . A method according to  claim 25 , wherein said droplets are formed from at least one of the group consisting of Wood's metal, Inconel®, cobalt, chromium, nickel, titanium, Octoil®, alloys, superalloys, refractory metals, a high temperature liquid metal, a high temperature fluent material, and combinations thereof.  
   
   
       27 . A method according to  claim 25 , wherein said droplets are at least one of the group consisting of electrically isolated from each other, substantially uniform in size, about equidistantly separated, and combinations thereof.  
   
   
       28 . A method according to  claim 25 , wherein said particulates are formed of at least one of the group consisting of powder, said fluent material, and combinations thereof.  
   
   
       29 . A method according to  claim 25 , wherein said inducing at least one charge to said plurality of said droplets includes independently irradiating each of said droplets with charges.  
   
   
       30 . A method according to  claim 25 , 
 wherein said fluent material is received from at least one reservoir; and    wherein said at least one of the group consisting of said stream of droplets, said coaxial stream of droplets, said planar array of parallel droplet streams, and combinations thereof are generated by at least one stream generator.    
   
   
       31 . A method according to  claim 30 , wherein said at least one stream generator controls a gravitational flow of said fluent material from said reservoir to create said at least one of the group consisting of said stream of droplets, said coaxial stream of droplets, said planar array of parallel droplet streams, and combinations thereof.  
   
   
       32 . A method according to  claim 25 , said method further comprising: 
 evacuating an area surrounding said at least one fluent material.    
   
   
       33 . A method according to  claim 25 , said method further comprising: 
 pressurizing an area surrounding said at least one fluent material.    
   
   
       34 . A method according to  claim 25 , said method further comprising: 
 maintaining said at least one fluent material at or near a predetermined temperature setpoint.    
   
   
       35 . An method according to  claim 25 , wherein at least a portion of an atmosphere in which at least a portion of said method is performed is at least one of the group consisting of dry nitrogen containing less than one percent oxygen, an atmosphere maintained at a vacuum pressure, sulfur hexafluoride, and combinations thereof.  
   
   
       36 . A method according to  claim 25 , said method further comprising: 
 heating at least one of said at least one fluent material, said droplets, and combinations thereof,    wherein said heating creates or retains said droplets in molten form prior to said inducing of said at least one charge.    
   
   
       37 . A method according to  claim 25 , wherein said inducing of said at least one charge is performed by irradiating at least a portion of said droplets with at least one beam of charged particles.  
   
   
       38 . A method according to  claim 37 , wherein said charged particles are free electrons.  
   
   
       39 . A method according to  claim 37 , wherein said at least one beam of charged particles is generated by an electron gun.  
   
   
       40 . A method according to  claim 25 , said method further comprising: 
 performing at least one of the group consisting of attracting at least one of said charges, accelerating at least one of said charges, directing at least one of said charges, and combinations thereof via at least one electrode.