Ultralow content silver densely-coated glass microsphere for high performance conducting polymer-matrix composites

A synergistic electroless Ag plating using binary reductants of NaBH4 and glucose is demonstrated to fabricate high conducting silver-coated glass microsphere composite particles (GM@AgCPs) with ultralow Ag content (WAg) of 5.1 wt% for high performance conducting polymer-matrix composites (CPMCs). In this approach, NaBH4, as strong reductant, plays an important role in the nucleation while glucose, as weak one, is responsible for the growth of nuclei, indicating the synergistic effect between the binary reductants. Furthermore, the nucleation and growth are dexterously separated by our experimental design. First, the addition of a small amount of NaBH4 solution results in a large driving force of redox reaction, and favors nucleation burst. Meanwhile, homogeneous nucleation is effectively inhibited at a low T. Second, glucose at an elevated T results in fast and uniform growth rate of nuclei, which tends to form compact nanoshell on glass microsphere. Consequently, CPMCs of as-synthesized GM@AgCPs exhibit lower resistivity, smaller percolation threshold and stronger shielding effectiveness than those of composite particles with same WAg synthesized by the previously-reported methods, originating from denser silver nanoshell. More importantly, as-obtained CPMCs show the most excellent reliability for electronic device interconnect among all available commercial Ag-containing CPMCs with the comparative resistivity, owing to the lowest WAg. Additionally, the as-synthesized composite particles or their CPMCs exhibit perfect environmental adaptability and mechanical performance. Our results promise important applications in conducting or electromagnetic interference shielding polymer-matrix composites.