Preparation and formation mechanism of high-performance novel (TiHfVNb)C medium-entropy submicron particles and ceramics

In this study, transition metal halides and phenolic resin were utilized to synthesize (TiHfVNb)C medium-entropy precursors by multi-metal organic frameworks (MOFs) method. The (TiHfVNb)C submicron particles were obtained by carbothermal reduction at a relatively low temperature (1500 °C) and subsequently consolidated into medium-entropy carbide ceramics via spark plasma sintering at 1950 °C. Effects of molar ratios of transition metal halides and phenolic resin, pyrolysis temperatures and holding time on the properties of MOFs-derived (TiHfVNb)C submicron particles was systematically investigated. Comprehensive characterization was performed on the as-synthesized submicron particles using FTIR, TGA, XRD, SEM, EDS and TEM, revealing that the as-synthesized submicron particles exhibited an elliptical morphology with fine particles size (~150   nm) and uniform particle size and elemental distribution. The MOFs-derived (TiHfVNb)C ceramic by SPS achieved a high density of 99.6% and displayed homogeneous microstructure. Remarkably, the SPS-sintered (TiHfVNb)C ceramics demonstrated competitive mechanical properties, with Vickers hardness and fracture toughness values reaching 21.7   GPa and 4.4   MPa·m¹ / ², respectively.