Recession Rates of Zirconium Carbide and Zirconium Diboride During Ultra-High Temperature Oxidation
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Date
2025-05
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The Ohio State University
Abstract
This research project aims to compare the oxidation kinetics and microstructure development of zirconium carbide (ZrC) and zirconium diboride (ZrB2) at temperatures between 1600 and 2400°C. ZrC and ZrB2 are ultra-high temperature ceramics (UHTCs), which are a class of ceramic material with melting points above 3000°C. A mix of covalent and metallic bonding makes them thermally and chemically resilient with high thermal and electrical conductivities. Studies have shown that ZrB2 is favored over ZrC at temperatures below 1200°C, but not above because the protective liquid layer of boria (B2O3) evaporates, leaving the material exposed, causing it to oxidize very quickly. These materials are of interest for use in leading-edge surfaces of hypersonic aircraft, but due to difficulty of testing, a direct comparison of the oxidation behavior of ZrC and ZrB2 has not been done at predicted service temperatures in publicly available research. This research hypothesizes that ZrB2 will oxidize faster than ZrC above the temperature that boria boils. This experiment compares the oxidation rates at a realistic range of operating temperatures by measuring the rate of recession of the unoxidized base material. The boiling point of boria was calculated with FactSage thermodynamic software to be around 1780°C. This project uses the microplasma resistive heating system at the University of Virginia (UVA) to oxidize ZrC and ZrB2 at 1800-2200°C for 1-7 minutes in an ambient pressure Ar atmosphere with 1% O2. The microstructure and recession rate were analyzed with scanning electron microscopy (SEM) and image processing. Analysis indicates that at 1800-1900°C, ZrB2 oxidizes slower. The recession rate for 2000-2200°C was not able to be calculated because all samples either fully oxidize or vaporize in under 1 minute.
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Keywords
High Temperature, Ceramic, Oxidation, Materials Science