Synthesis of silver nanoparticles and their self-organization behavior in epoxy resin

Silver nanoparticles were chemically synthesized by means of microemulsions techniques. Their self-organization behavior, including detailed descripti on of the mechanism, the process and the resultant structure changes, was i nvestigated by examining the electrically conductive characteristics of sil ver nanoparticles/solvent suspension, silver nanoparticles/epoxy resin mixt ure and its cured version, respectively. For silver nanoparticles suspensio n, higher particle concentration was found to be unfavorable to the formati on of conducting paths owing to particles aggregation. For silver/epoxy mix ture, transition-like changes in conductivity as a function of temperature were observed, manifesting two-stage self-organization of the nanoparticles : one related to the formation of some texture and the other related to mel ting and growth of the particles. As a result, conductive networks can be e stablished by freezing the nanoparticles aggregation at the first stage und er a particle loading even lower than the percolation threshold estimated c onventionally. Accordingly, curing reaction of epoxy resin should be so des igned as to adequately match the self-organization process. (C) 1999 Elsevi er Science Ltd. All rights reserved.