Influence of sol–gel derived ZrO2 and ZrC additions on microstructure and properties of ZrB2 composites |
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| Affiliation: | 1. Department of Materials Engineering, Monash University, Clayton, VIC 3800, Australia;2. Monash Centre for Electron Microscopy, Monash University, Clayton, VIC 3800, Australia;3. Aerospace Division, Defence Science & Technology Organization, Fisherman''s Bend, VIC 3207, Australia;4. Process Science & Engineering, Commonwealth Scientific and Industrial Research Organisation, Clayton, VIC 3168, Australia;1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China;2. State Key Laboratory of Advanced Refractories, Sinosteel Luoyang Institute of Refractories Research Co., Ltd., Luoyang 471039, China;3. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK;1. State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Shanghai 200050, China;2. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | ZrB2 powder was coated with 5% Zr OC sol–gel precursor and sintered by SPS. Relative densities >98% were achieved at 1800 °C with minimal grain growth and an intergranular phase of ZrC. Carbon content in the precursor determined the type of reinforcing phase and porosity of the sintered composites. XRD, SEM and EDS studies indicated that carbon deficiency resulted in ZrO2 retention, improving ZrB2 densification with oxide particle reinforcement. Excess carbon resulted in ZrC formation as the reinforcing phase, but could yield porosity and residual carbon at grain boundaries. These two types of ZrB2 composites displayed different densification and microstructural evolution that explain their contrasting properties. In the extreme oxidative environment of oxyacetylene ablation, the composites with ZrC-C maintained superior leading edge geometry; whereas for mechanical strength, a bias towards the residual ZrO2 content was beneficial. This highlighted the sensitivity of processing carbon-precursors in the initial sol–gel process and the carbon content in ZrB2-based composite systems. |
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| Keywords: | Sol–gel processing Coated powder Zirconium diboride Zirconium carbide UHTC composites |
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