Method Of Production Of High Purity Silver Particles

Abstract

A method for synthesizing high purity silver particles and colloids without requiring the addition of either surfactants or reducing agents thereto, or requiring only a minimal amount thereof. The synthesizing process comprises: (i) a silver oxalate synthesizing process; (ii) a process of dispersing silver oxalate into an appropriate carrier; and {iii) a process of heating said silver oxalate dispersed into said carrier at a temperature of at least 100° C. Silver particles and colloids of various form factor and size may be synthesized depending upon the reaction conditions, the carrier, and the type of surfactant.

1 . A method for production of silver particles, comprising the steps of:
 (a) dispersing solid silver oxalate particles in a carrier; and   (b) heating said dispersed silver oxalate to a temperature of at least 100° C. under a pressure that is greater than atmospheric pressure to decompose said silver oxalate into silver particles.   
     
     
         2 . The method of  claim 1 , further comprising the step before step (a) of producing said silver oxalate by mixing a first solution of a silver compound and a second solution of an oxalate compound to form silver oxalate. 
     
     
         3 . The method of  claims 1  or  2 , further comprising the step of adding a surfactant to said dispersed silver oxalate before the heating of step (b). 
     
     
         4 . The method of  claim 3  wherein said surfactant is selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorochemical surfactants, polymerizable surfactants, and any combination of the preceding surfactants. 
     
     
         5 . The method of  claim 2 , further comprising the step of adding a surfactant to said first solution before said mixing step. 
     
     
         6 . The method of  claim 5  wherein said surfactant is selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluOrochemical surfactants, polymerizable surfactants, and any combination of the preceeding surfactants. 
     
     
         7 . The method of  claim 2  further comprising the step of adding a surfactant to said second solution before said mixing step. 
     
     
         8 . The method of  claim 7  wherein said surfactant is selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorochemical surfactants, polymerizable surfactants, and any combination of the preceeding surfactants. 
     
     
         9 . The method of  claims 1  or  2 , wherein the dispersing of step (a) comprises adding silver oxalate to said carrier and subjecting the mixture of silver oxalate and carrier to ultrasonic treatment. 
     
     
         10 . The method of  claims 1  or  2 , wherein said carrier is selected from the group consisting of water, methyl alcohol, ethyl alcohol, propyl alcohol, and a mixture of any of the preceding. 
     
     
         11 . The method of  claim 2 , wherein said silver compound is AgNO 3 . 
     
     
         12 . The method of  claim 2 , wherein said oxalate compound is selected from the group consisting of sodium oxalate and oxalic acid. 
     
     
         13 . The method of  claim 2 , further comprising the step following the production of silver oxalate of washing said silver oxalate with water to remove impurities. 
     
     
         14 . The method of  claim 4 , wherein said surfactant is selected from the group consisting of PVP (polyvinyl pyrrolidone) and gelatin. 
     
     
         15 . The method of  claim 6 , wherein said surfactant is selected from the group consisting of PVP (polyvinyl pyrrolidone) and gelatin. 
     
     
         16 . The method of  claim 8 , wherein said surfactant is selected from the group consisting of PVP (polyvinyl pyrrolidone) and gelatin. 
     
     
         17 . The method of  claim 3 , wherein said surfactant is no greater than 80% by weight of the silver in step (b). 
     
     
         18 . The method of  claim 5 , wherein said surfactant is no greater than 80% by weight of the silver in step (b). 
     
     
         19 . The method of  claim 7 , wherein said surfactant is no greater than 80% by weight of the silver in step (b).