Effects of milling time on the structural and morphological features of Si-Based refractory compounds derived from selected Agro-Wastes

The effects of milling time on the structural and morphological features of Si-based refractory compounds (SBRC) derived from selected agro-wastes (bamboo leaves- BL and coconut shell-CS) are reported. The processing of the SBRC was done using the controlled environment of a conventional furnace at a heating rate of 10°/min between 900 and 1650 °C. The SBRC was then placed in 250 ml vial containing zirconia balls as grinding media of 8 mm in diameter to mill in an argon atmosphere (ultra-pure with 99.98% wt, < 3 ppm O₂) using a planetary mill, Retsch, with a speed of 300 rpm. A ball-to-powder ratio (BPR) of 10:1 with 3 wt% of ethanol as process control agent (PCA) were used. The optimum milling time used was 25 h at a variation of 5 h. The morphological features were examined using a scanning electron microscope (SEM/EDX) and X-ray diffraction (XRD). The SEM results revealed a good dispersion of SBRC in the network of the BL and CS respectively. SiC precipitating as moissanite phase being a polytype of SiC with cubic structure was revealed from the XRD spectrum for BL sample. Also, other intermetallic phases were evident from all the samples under different milling time. It is evident that size grows with milling time due to high plastic deformation. It was observed that the milling time influenced, to a significant extent, the dislocation density. The attainment of a nanometer scale particle sizes was achieved using this method. The SBRC shows a good potential as nano-reinforcement materials for the development of aluminium matrix composites.