Advisor(s)
Manoj Mahapatra
Committee Member(s)
Gregory Kubacki
Haibin Ning
James Hemrick
Robin Foley
Shane Catledge
School
School of Engineering
Document Type
Dissertation
Department (new version)
Materials Engineering
Date of Award
9-11-2025
Abstract
The feasibility of gahnite (zinc aluminate, ZnAl2O4) as an alternative to magnesium aluminate spinel (MgAl2O4) in high-temperature refractory applications has been explored. ZnAl2O4 is being studied due to its high melting point (1950 °C), comparable thermomechanical properties, similar crystal structure, and complete solid solubility with MgAl2O4, enabling partial or complete replacement of MgAl2O4 in refractories. MgAl2O4 is known to exhibit good phase compatibility with calcium aluminate cement (CAC) phases such as hibonite (CaAl12O19, CA6), which is linked to excellent thermomechanical properties. Phase evolution was studied in the Al2O3-rich region of the CaO–Al2O3–ZnO ternary system to explore solid-state compatibility between ZnAl2O4 and CAC phases. The investigation focused on the formation of ternary phases CAZ-I (Ca2Zn2Al28O46), and CAZ-II (CaZn2Al16O27), drawing parallels to the well-established phase relations in the CaO–Al2O3–MgO system. The CaO–Al2O3–ZnO ternary phase diagram is found to be analogous to the CaO–Al2O3–MgO system on the Al2O3-rich side. Formation of CAZ phases using CAC in ZnAl2O4-Al2O3 castable formulation was investigated using various industry-grade aggregates. Specifically, microstructural development in CAC-bonded ZnAl2O4–Al2O3 castables was studied, with focus on spatial distribution of acicular phases in matrix and aggregate–matrix interfaces. Corrosion resistance was evaluated using static cup tests against industry-representative steelmaking slags. A comparative study between ZnAl2O4 and MgAl2O4 was conducted to examine the influence of slag chemistry, with focus on iron oxide content and basicity—two key factors affecting refractory corrosion. In addition to slag corrosion, resistance to alkali vapor attack was assessed using ASTM C987, simulating vapor-phase corrosion in cement kilns, glass furnaces, and gasifiers. Results reveal distinct differences in corrosion response, highlighting the chemical stability of ZnAl2O4 under various slag chemistries. To complement the experimental findings, computational fluid dynamics (CFD) simulations were used to model convective slag flow in the static cup setup, offering a mechanistic understanding of how thermal and fluid dynamics contribute to refractory wear. The results support ZnAl2O4 as a viable alternative to MgAl2O4, either as a partial or complete replacement in refractory castables, with demonstrated compatibility with cement, and superior corrosion resistance to molten slags and alkali vapor.
ProQuest ID
Recommended Citation
Ramteke, Rajat Durgesh, "Phase Compatibility, Bonding, And Corrosion Resistance Of Gahnite And Spinel Refractories" (2025). All ETDs from UAB. 7399.
https://digitalcommons.library.uab.edu/etd-collection/7399
