A Novel Microstructural Evolution Model for Growth of Ultra-Fine Al₂O₃ Oxides from SiO₂ Silica Ceramic Decomposition...

In this paper, experimental verification of the microstructural evolution model during sintering of aluminum, iron and particulate mullite ceramic powders using self-propagated high-temperature synthesis (SHS) was performed. The powder mixture with 20% wt. content of reinforcing ceramic was investigated throughout this research. The mixed powders were cold pressed and sintered in a vacuum at 1030 °C. The SHS reaction between sintered feed powders resulted in a rapid temperature increase from the heat generated. The temperature increase led to the melting of an aluminum-based metallic liquid. The metallic liquid infiltrated the porous SiO₂ ceramics. Silicon atoms were transited into the intermetallic iron-aluminum matrix. Subsequently, a ternary matrix from the Fe-Al-Si system was formed, and synthesis of the oxygen and aluminum occurred. Synthesis of both these elements resulted in formation of new, fine Al₂O₃ precipitates in the volume of matrix. The proposed microstructural evolution model for growth of ultra-fine Al₂O₃ oxides from SiO₂ silica ceramic decomposition during SHS was successfully verified through scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS) analysis and X-ray diffraction (XRD).