Abstract
Ultrahigh temperature ceramics (UHTCs) such as diborides of zirconium, hafnium tantalum and their composites are considered to be the candidate materials for thermal protection systems of hypersonic vehicles due to their exceptional combination of physical, chemical and mechanical properties. A composite of ZrB2-TiB2 is expected to have better properties. In this study, an attempt has been made to fabricate ZrB2-TiB2 ceramics using mechanically activated elemental powders followed by reactive spark plasma sintering (RSPS) at 1400 °C. Microstructure and phase analysis was carried out using X-ray diffractometer (XRD) and electron microscopy to understand microstructure evolution. Fracture toughness and hardness were evaluated using indentation methods. Nanoindentation was used to measure elastic modulus. Compressive strength of the composites has been reported.
Highlights
IntroductionZirconium diboride (ZrB2 ) and Titanium diboride (TiB2 ) have very high melting points above
Zirconium diboride (ZrB2 ) and Titanium diboride (TiB2 ) have very high melting points above3000 ◦ C, high hardness (>25 GPa), elastic modulus (>500 GPa), good electrical (1.0 × 107 S/m) and thermal (60–120 W·m−1 ·K−1 ) conductivities [1,2] and chemical stability
Pure titanium (Ti) (−325 mesh, 99.5% metal basis, Alfa Aesar, Chennai, India), zirconium (Zr) (99% pure sponge fines,
Summary
Zirconium diboride (ZrB2 ) and Titanium diboride (TiB2 ) have very high melting points above. 3000 ◦ C, high hardness (>25 GPa), elastic modulus (>500 GPa), good electrical (1.0 × 107 S/m) and thermal (60–120 W·m−1 ·K−1 ) conductivities [1,2] and chemical stability. These physical and chemical characteristics are mandatory requirements in applications such as thermal protection systems of re-entry vehicles, crucibles and rocket nozzle [3,4,5]. Fabricating fully dense compacts using conventional sintering techniques requires long processing time (>2 h) and high temperatures (>1800 ◦ C).
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