Synthesis and Characterization of γ-Al₂O₃/SiO₂ Composite Materials

This article reports the synthesis process of γ-alumina/SiO₂ composite from aluminium powders and amorphous nanosilica through the means of tetra-methyl-ammonium hydroxide (TMAH) as the mixing medium which produced aluminium hydroxide Al(OH)₃ in the form of white powders. The crystal structures, microstructures, and mapping of the atomic constituent of γ-Al₂O₃ and γ-Al₂O₃/SiO₂ samples were respectively analyzed via X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray SEM-EDX. At the calcination temperature to 300 °C, the samples still had boehmite phase, and the boehmite phase transformation to γ-alumina phase occurred at temperature of 700-900 °C. The γ-alumina phase began to form at the calcination temperature of 500-700 °C with the crystal structure of (440), (511), (400), (222), (311), and (111). The similar diffraction pattern was also shown by the γ-Al₂O₃/SiO₂ composite for the calcination temperature of 700 °C and 900 °C. The microstructure analysis of the γ-Al₂O₃/SiO₂ showed that SiO₂ particles were smaller and round while the γ-Al₂O₃ particles were bigger and elongated. Additionally, the mapping results showed SiO₂ and γ-Al₂O₃ particles were homogenously distributed.