Patent ID: 8372178

Claim:
A process for making silver powder comprising silver particles, each silver particle comprising silver components 100-500 nm long, 80-100 nm wide and 80-100 nm thick, assembled to form a spherically-shaped, open structured particle substantially as shown in FIG 3 , wherein the surface of the particle resembles the surface of an orange rind and wherein the silver particles have a d 50 particle size of from about 2.5 μm to about 6 μm, said process comprising: (a) preparing an acidic aqueous silver salt solution comprising a water soluble silver salt dissolved in deionized water; (b) preparing an acidic reducing and surface morphology modifier solution comprising: (i) a reducing agent selected from the group consisting of an ascorbic acid, an ascorbate and mixtures thereof dissolved in deionized water; (ii) nitric acid; and (iii) a surface morphology modifier selected from the group consisting of sodium citrate, citric acid and mixtures thereof; (c) maintaining the acidic aqueous silver salt solution and the acidic reducing and surface morphology modifier solution at the same temperature, wherein that temperature is in the range of about 20° C. to about 55° C., while stirring each solution; and (d) mixing the acidic aqueous silver salt solution and the acidic reducing and surface morphology solution over a period of less than 10 seconds with no stirring to make a reaction mixture that is maintained at the temperature of (c) and after 3 to 7 minutes stirring the reaction mixture for 2 to 5 minutes to produce the silver powder particles in a final aqueous solution.