Spherical silver powder and method for producing same

Abstract

While a water reaction system containing silver ions is irradiated with ultrasonic waves to cause cavitation therein, a reducing agent containing solution, which contains an aldehyde as a reducing agent, is mixed with the water reaction system to deposit silver particles, the solid-liquid separation of which is carried out, and thereafter, the separated silver particles are washed and dried to produce a spherical silver powder which has a closed cavity in each particle thereof.

1 . A method for producing a spherical silver powder, said method comprising the steps of:
 preparing a water reaction system containing silver ions;   preparing a reducing agent containing solution which contains an aldehyde as a reducing agent; and   depositing silver particles by reduction by mixing the reducing agent containing solution with the water reaction system while causing cavitation in the water reaction system.   
     
     
         2 . A method for producing a spherical silver powder as set forth in  claim 1 , wherein said cavitation is caused by irradiating said water reaction system containing silver ions with ultrasonic waves. 
     
     
         3 . A method for producing a spherical silver powder as set forth in  claim 1 , wherein said water reaction system containing silver ions is an aqueous solution containing a silver ammonia complex. 
     
     
         4 . A method for producing a spherical silver powder as set forth in  claim 1 , wherein said reducing agent containing solution is a solution containing formaldehyde or acetaldehyde. 
     
     
         5 . A method for producing a spherical silver powder as set forth in  claim 1 , which further comprises steps of carrying out the solid-liquid separation of said silver particles deposited by reduction;
 washing the separated silver particles; and   drying the washed silver particles at a temperature of not higher than 100° C.   
     
     
         6 . A method for producing a spherical silver powder as set forth in  claim 1 , wherein said spherical silver powder has a closed cavity in each particle thereof. 
     
     
         7 - 11 . (canceled)