Submicron and nano size particle encapsulation by electrochemical process and apparatus

Abstract

An apparatus and method for coating or treating powdered material, particularly ultra-fine powders in the nanometer or submicron range of mean diameters, by electrolytic processes. A platen is mounted for rotation upon a fixed shaft, and a rotary flow-through electrolytic cell is mounted upon a platen for rotation thereon, the cell's axis of rotation being offset from the platen's axis of rotation. The cells axis of rotation revolves around the platen's axis as the platen rotates. The electrolytic cell accordingly undergoes a planetary rotation, as the cell revolves around the platen's axis of rotation. The planetary rotation of the cell allows the powdered material to be collected by centrifugal force and constantly agitated to promote uniform electroplating. An electrode array and rolling contact system are supplied which allow electric potential to be applied only to those electrodes actually in contact with the powdered material to be treated.

1 . A method for depositing a coating on a substrate powder, the method comprising the steps of: 
 rotatably mounting a rotary flow-through electrolytic cell on a platen;    loading a substrate powder comprising a particle size of less than 20 micrometers in the cell;    rotating the cell about a first axis relative to the platen;    rotating the platen about a second axis offset from and parallel to the first axis, thereby enabling the cell to undergo planetary revolution;    flowing a solution through the cell;    generating sufficient centrifugal force to overcome suspension of the substrate powder in the solution; and    depositing the coating on at least a portion of the substrate powder.    
     
     
         2 . The method of  claim 1  wherein the generating step comprises forcing at least a portion of the substrate powder against the inner wall of the cell.  
     
     
         3 . The method of  claim 2  wherein at least a portion of the substrate powder contacts an electrode strip attached to the inner wall of the cell.  
     
     
         4 . The method of  claim 2  wherein most of the substrate powder collects along a short arcuate segment of the inner wall.  
     
     
         5 . The method of  claim 4  further comprising the step of tumbling the substrate powder along the inner wall as the cell rotates.  
     
     
         6 . The method of  claim 5  wherein the powder contacts one or more electrode strips arrayed on the inner wall.  
     
     
         7 . The method of  claim 6  wherein only a subset of electrode strips is electrically connected to a power supply at any given time.  
     
     
         8 . The method of  claim 7  further comprising the step of varying which electrode strips comprise the subset so that most of the tumbling substrate powder is substantially continually in contact with at least one charged electrode strip.  
     
     
         9 . The method of  claim 1  further comprising the step of reversibly disposing an electrode into the cell.  
     
     
         10 . The method of  claim 1  further comprising the step of filtering and recirculating the solution.  
     
     
         11 . The method of  claim 1  further comprising the step of reversing the rotation of the cell.  
     
     
         12 . The method of  claim 11  further comprising the step of auguring the substrate powder out of the cell.