1. Department of Engineering Metallurgy, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, South Africa
2. Council for Scientific and Industrial Research (CSIR), Materials Science and Manufacturing, Meiring Naude Road, Brummeria, P.O. Box 395, Pretoria 0001, South Africa
3. DST/CSIR Nanotechnology Innovation Centre, National Centre for Nano-Structured Materials, Council for Scientific Industrial Research, P.O. Box 395, Pretoria 0001, South Africa