Abstract
Nanosized silver particles were produced by chemical reduction method using silver nitrate as precursor. PVP was added as a protective agent to avoid agglomeration of these nanosized Ag colloids. Increasing PVP concentration and decreasing aging temperature for a given mass of precursor were found to yield smaller nanosized silver particles. By varying the initial conditions, the colloidal size can be controlled within the range of 30-50nm. Results indicated that this polyol process can be easily scaled up if we can overcome the problem of heat transfer to assume uniform temperature distribution within the reactor.In order to reduce the influence of PVP in future applications, the synthesized particles must be separated and purified. The suspension was first washed by acetone, followed by centrifugation to separate PVP-Ag colloids. Then the colloids were washed two times by water/acetone(1:3) solution. After these steps, we could then obtain pure silver nanoparticles without PVP. The silver loss however was about 21wt.%. These agglomerated silver nanoparticles were then dissolved in tetrahydrofuran and mixed with epoxy resin. Tetrahydrofuran was later removed by evaporation to obtain Ag-resin nanocomposite.With regards to the electric properties of nanocomposite, the apparent critical volume fraction decreased to about 1.13vol.% when we used 40nm nanosized silver particles as conductive fillers. In addition, we found that the three-roll-mill process could help to disperse well Ag nanoparticles in the composite and to obtain uniform electric properties.