Calcium phosphate-encapsulated silver powder

Abstract Calcium phosphate encapsulated silver powder was obtained by heterogeneous nucleation during treatments of dispersed silver first with solutions of Ca(NO 3 ) 2 and then with Na 2 HPO 4 . Before treatment silver powders were functionalized with 3-mercaptopropionic acid and dispersed in a precipitation medium so the carboxylate groups could serve as nucleation sites. The ratio Ca/P in the coating increases with the number of treatment cycles. In contrast, calcium phosphate precipitation by slow release of phosphate ions via hydrolysis of tri(4-nitrophenyl)phosphate in a solution of Ca(NO 3 ) 2 results in homogeneous nucleation only; coating does not form on silver particles.