Influence of Weight Fraction on the Average Crystallite Size of Hybrid ZnO/Al2O3 Supported Bio-Waste Activated Carbon Composites

Due to the inherent high surface energy and the multifaceted interaction between them and the matrix interface, metal  nanoparticles tend to coalesce in the absence of repulsive forces provided by a capping agent. It is therefore imperative  to provide a support system that will moderate the spatial behaviour of the particles to prevent the formation of bulk  particles and eventually deteriorate in quality. This paper reports the influence of weight fraction on the average  crystallite size of Al2O3 introduced onto formulated ZnO groundnut shell activated carbon (GSAC) supported  composites. Al2O3 was synthesised using the sol-gel technique with aluminium trichloride as precursor salt. The surface  morphology and average particle size of synthesised Al2O3 were determined using scanning electron microscopy (SEM)  and transmission electron microscope (TEM), respectively. Al2O3 was introduced onto formulated GSAC/ZnO mixture  at varying weight percentages (75:25, 50:50 and 25:75) to produce GSAC-ZnO/Al2O3 composites. The resulting  composites were then characterised using X-ray diffraction (XRD). Relying on lattice parameters such as diffraction  peaks and full width at half maximum (FWHM) obtained from the X-ray powder diffraction, the effects of weight  fraction on the average crystallite size of ZnO/Al2O3 supported GSAC composites were determined using the Scherrer  equation. The result obtained showed an increase in average crystallite size with the increase in amount of Al2O3  introduced onto the formulated GSAC/ZnO composite, but declined with further addition of Al2O3. The GSAC-ZnO/  Al2O3 composite with a 75:25 weight fraction was found to have the smallest average crystallite size of 52.25 nm. The  results suggest that the stabilisation influence of GSAC on ZnO and Al2O3 is reduced with an increase in the amount of  Al2O3 and the tendency for agglomeration of ZnO and Al2O3 ions may have been weakened with the addition of more  Al2O3, resulting in a decrease in crystallite size.