Synthesis and Characterizations of Copperbased Nanostructures Developed by Mechanical Milling

The present work investigates on Cu-based nanocomposites developed by mechanical milling. Cu99Cr1, Cu94Cr6, Cu99Cr1–4 wt.% SiC and Cu94Cr6–4 wt.% SiC compositions were subjected to high energy ball milling for 50 h. The phase evolution and morphological changes of the milled samples were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared radiation (FTIR) and nano zeta sizer (NZS) analysis. XRD analysis for crystallite size, lattice microstrain% and lattice parameter of the Cu-based alloys revealed that very little amount Cu-based solid solution was possibly formed. XRD, FTIR and NZS analysis revealed that crystallite size/particle size of the 50 h milled samples was in the nanometer range. An attempt was made to consolidate the mechanically alloyed powder to produce bulk Cubased nanocomposites having densities near to the theoretical density. Consolidation was carried out by microwave sintering (800°C and 900°C, 30 min), vacuum sintering (900°C and 1000°C, 60 min) and conventional pressure-less sintering (900°C and 1000°C, 60 min) methods. The microwave sintering compacts achieved a relative density (with respect to theoretical density) of 90.8–95% (900°C, 30 min), compared to 84.2–89% in the vacuum sintered (1000°C, 60 min) and 82.3–87% in the pressure-less sintered (1000°C, 60 min) compacts. The particle size (< 200 nm) obtained through AFM and crystallite size(65–125 nm) calculated from XRD data of the sintered specimens established that the bulk consolidated materials were fine grained composites. The microwave sintered compacts showed greatly superior mechanical properties (e.g. Vickers hardness of 190–240 Hv) compared to the vacuum sintered (173–218 Hv) and pressure-less sintered compacts (170–216 Hv), due to the presence of nano-features and better densification. Wear resistance of the microwave sintered specimens was found to be increased with addition of Cr and nanosize SiC particles. Electrical conductivity of the microwave sintered specimens showed 60–70% conductivity of IACS compared to 40–50% for conventional and vacuum sintered compacts. Therefore the material developed in the present investigation could be successfully used for thermo-electric applications