Enhanced electrical conductivity and hardness of silver-nickel composites by silver-coated multi-walled carbon nanotubes

Abstract

We investigated electrical conductivity and Vickers hardness of Ag- and Ni-based composites prepared by powder metallurgy involving spark plasma sintering. The starting composition was Ag:Ni = 61:39 vol%, which provided an electrical conductivity of 3.30 × 105 S cm-1 and a hardness of 1.27 GPa. The addition of bare multi-walled carbon nanotubes (MWNTs, 1.45 vol%) increased hardness (1.31 GPa) but decreased electrical conductivity (2.99 × 105 S cm-1) and carrier mobility (11 cm2 V-1 s-1) due to the formation of Ni<inf>3</inf>C in the interface between the MWNTs and Ni during spark plasma sintering. The formation of Ni<inf>3</inf>C was prevented by coating the surface of the nanotubes with Ag (nAgMWNTs), concomitantly increasing electrical conductivity (3.43 × 105 S cm-1) and hardness (1.37 GPa) of the sintered specimen (Ag:Ni:nAgMWNTs = 59.55:39:1.45 vol%). The electrical contact switching time (133 357) was also increased by 30%, demonstrating excellent feasibility as electrical contact materials for electric power industries. © 2015 IOP Publishing Ltd.