Method and apparatus for preparing coated particles

Abstract

The present invention relates to a method of forming a metal coated particle, to metal coated particles prepared according to the method and the use of these metal coated particles. The method comprising the steps of: providing a source of base particles to be coated; providing a source of a metal-comprising coating particles; and feeding the base particles specified in step (a) and the source of metal comprising coating particles specified in step (b) into a continuous reactor including heat exchange means to cause contact of the base particles with the source of coating particles thereby to form the metal coated particles. The coated particles include a homogeneous coating and can be used in a variety of applications.

1 . A method for fabricating a plurality of metal coated particles in a liquid medium, the method comprising the steps of:
 a. providing in a liquid carrier a source of base particles to be coated,
 the source of base particles being selected from the group consisting of silicon, tin, germanium, gallium, lead, zinc, aluminium, graphite, oxides thereof, compounds thereof, and mixtures thereof, 
 the source of base particles being provided at a loading of at least 0.001 Kg/Kg; 
   b. providing a source of metal-comprising coating particles;   c. providing a continuous reactor including a tubular reaction chamber having an internal diameter of greater than 5 mm and comprising a heat conductive material thereby to provide heat exchange between the continuous reactor and surroundings; and   d. forming a reaction mixture by feeding the source of base particles and the source of the metal-comprising coating particles into the continuous reactor at a velocity of at least 0.05 m/s thereby to contact the source of base particles with the source of metal-comprising coating particles thereby to form a metal coating on base particle having a diameter of greater than 0.5 μm.   
     
     
         2 - 6 . (canceled) 
     
     
         7 . The method according to  claim 1 , wherein the source of metal-comprising coating particles is selected from the group consisting of silver, copper, platinum, palladium, iron, cobalt, rhodium, vanadium, nickel, ruthenium, iridium, and gold. 
     
     
         8 . (canceled) 
     
     
         9 . The method according to  claim 1 , wherein the source of metal-comprising coating particles comprises a dispersion of metal nano-particles in a carrier liquid. 
     
     
         10 . The method according to  claim 1 , wherein the source of metal-comprising coating particles comprises a solution comprising ions of the metal coating. 
     
     
         11 - 18 . (canceled) 
     
     
         19 . The method according to  claim 1 , wherein the reaction mixture is mixed at a temperature of no more than 120° C. 
     
     
         20 - 34 . (canceled) 
     
     
         35 . The method according to  claim 1 , which further comprises the step of separating the base particles comprising the metal coating from the reaction mixture. 
     
     
         36 . The method according to  claim 1 , wherein the continuous reactor is at a pressure less than or equal to 2000 KNm −2 . 
     
     
         37 . The method according to  claim 1 , wherein the source of base particles comprises silicon and the source of metal-comprising coating particles is a metal ion salt selected from group consisting of silver nitrate, ammoniacal silver nitrate, and a mixture thereof. 
     
     
         38 . The method according to  claim 1 , which further comprises the step of contacting the metal base particles comprising the metal coating with an etching solution thereby to etch the base particles comprising the metal coating. 
     
     
         39 - 40 . (canceled) 
     
     
         41 . The method according to  claim 1 , wherein the continuous reactor is a tubular reactor having an internal surface area to volume ratio of greater than 5:1 m −1 . 
     
     
         42 . The method according to  claim 1 , wherein the continuous reactor has an internal diameter of less than 14 mm. 
     
     
         43 - 45 . (canceled) 
     
     
         46 . The method according to  claim 1 , wherein the base particles have a BET Specific Surface Area of at least 1 m 2 /g. 
     
     
         47 - 48 . (canceled) 
     
     
         49 . An apparatus for continually coating base particles in a liquid carrier, the apparatus comprising a continuous reactor including heat exchange means, the reactor comprising:
 a. a tubular reaction chamber having an internal diameter of at least 5 mm and a first inlet for receiving one or more reagents of a reaction mixture comprising a source of base particles to be coated in a liquid carrier at a loading of at least 0.001 Kg/Kg and a source of metal coating particles;   b. an outlet for releasing products and/or spent reagents from the tubular reaction chamber;   c. means for continually causing reagents and coated products to flow from the inlet to the outlet at a fluid velocity of at least 0.05 m/s thereby to contact the source of base particles with the source of metal-comprising coating particles thereby to form a metal coating on base particles having a diameter of greater than 0.5 μm; and   d. heat exchange means to maintain temperature of the reaction mixture within a defined temperature range.   
     
     
         50 - 57 . (canceled) 
     
     
         58 . The apparatus according to  claim 49 , which is provided with one or more inlet means for introducing reagents into the chamber, the inlets being disposed between the first inlet and the outlet. 
     
     
         59 - 60 . (canceled) 
     
     
         61 . The apparatus according to  claim 49 , which further includes means for controlling the velocity of the particles between the first inlet and the outlet. 
     
     
         62 - 73 . (canceled) 
     
     
         74 . The method according to  claim 9 , wherein the concentration of metal nano-particles in the carrier liquid is at least 0.003 kg/kg. 
     
     
         75 . The method according to  claim 10 , wherein the metal ion is provided at a concentration of at least 2 mM/m 2  of exposed base particle surface. 
     
     
         76 . The method according to  claim 1 , wherein the source of base particles is provided in the form of a slurry comprising a dispersion of particles in a carrier liquid. 
     
     
         77 . The method according to  claim 1 , wherein the source of base particles is provided at a loading of no greater than 0.03 kg/kg. 
     
     
         78 . The method according to  claim 1 , wherein the velocity of feeding the source of base particles and the source of metal-comprising coating particles into the continuous reactor is greater than 0.5 m/s.