Chemical Pathways for Wollastonite Crystallization in CaO-SiO2 Based Glazes

Niah Johnson

Co-Presenters: Individual Presentation

College: Hennings College of Science Mathematics and Technology

Major: BS.CHEMISTRY/EXP

Faculty Research Mentor: Stokes-Huby, Heather  Mongelli, Mathew

Abstract:

Wollastonite (CaSiO3) crystallization in CaO-SiO2 based glasses is investigated as a melt-driven chemical reaction controlled by thermodynamic driving forces and kinetic limitations. This study focuses on the structural and chemical pathways that lead to wollastonite formation during a controlled cooling of calcium-rich silicate melts. Prepared glass compositions within the CaO-SiO2 system were analyzed in controlled thermal environments to isolate crystallization temperature windows. Differential thermal analysis, x-ray diffraction, and scanning electron microscopy were used to identify crystallization, confirm phase assemblages, and examine crystal morphology and chemical distribution. Results indicate that wollastonite formation is preceded by local ordering of Ca-O-SiO2 environments and chain silicate linkages. Crystallization occurs within a limited temperature range where thermodynamic driving force is sufficient and diffusion is kinetically accessible so structural reorganization is possible. These results support the reaction-pathway model in which wollastonite forms through progressive melt reorganization and structural ordering, providing a predictable melt mediated process for CaO-SiO2 based glass systems in wollastonite crystallization.Key words: Ceramics, glaze, crystallization, wollastonite.