|About this Abstract
||Materials Science & Technology 2020
||Manufacturing and Processing of Advanced Ceramic Materials
||Investigating the Dependence of Microstructure Evolution in Alumina on the Liquid Phase Chemistry in the CaO-Al2O3-SiO2 System: Densification, Grain Growth and Secondary Phase Formation
||Sarah Whipkey, William M. Carty
|On-Site Speaker (Planned)
This study investigated microstructure evolution of industrial-grade alumina (88-98%) with grain boundary compositions in the CaO-Al2O3-SiO2 system. The SiO2:CaO ratio strongly influenced both densification and grain size under identical sintering conditions. Densification and grain growth behavior was categorized into three distinct regions by the SiO2:CaO ratio, proposed to be due to varying viscosities, diffusion rates, and glass forming tendencies. Chemistries with molar ratios of SiO2:CaO > 1 (high silica) exhibited predictable sintering behavior, with minimal secondary phase formation, whereas SiO2:CaO < 1 (high calcia) displayed significant secondary phase formation, which inhibited the growth of alumina grains and reduced grain sizes. Systems with SiO2:CaO ≈ 1 exhibited unpredictable behavior and secondary phase formation, presumably due to non-uniform chemistry distributions. Normal grain growth was observed in all cases, and average grain sizes increased with increasing CaO content until the SiO2:CaO ratio fell below 1:1.5, where excessive secondary phase formation occurred.
||Planned: At-meeting proceedings