Mechanical properties and electrical conductivity of Cu-Cr and Cu-Cr-4% SiC nanocomposites for thermo-electric applications

The present work investigates the feasibility of microwave sintering to produce bulk metal-based nanocomposites having blend composition of Cu(99)Cr(1), Cu(94)Cr(6), Cu(99)Cr(1)-4 wt.% SiC and Cu(94)Cr(6)-4 wt.% SiC (average particle size similar to 30 nm). The 50 h ball-milled samples were uniaxially pressed, and then pellets were sintered at 800 degrees C, 900 degrees C and 1000 degrees C for a constant soaking period of 30 min by microwave sintering technique. Microstructural characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Sintered compacts resulted a highly densified compacts (similar to 95% relative density) while retaining ultra-fine grains (100-200 nm) in the matrix. The mechanical properties, namely, hardness and wear resistance, and electrical conductivity of the sintered specimens were also evaluated. The best combination of mechanical properties (e.g. hardness similar to 2.4 GPa) and electrical conductivity (60.3% of IACS) were obtained for Cu(94)Cr(6)-4 wt.% SiC sintered at 900 degrees C. This is possibly due to presence of ultra-fine grains in the bulk samples, good densification and proper bonding between particles. The results were analyzed in the light of interactions of microwaves between metallic matrix and microwave susceptive SiC particulates. (C) 2011 Elsevier B.V. All rights reserved.