MOG derived high-properties (ZrHfNbTaCr)C high-entropy nanoparticles to fabricate ceramics

• Novel (ZrHfNbTaCr)C high-entropy precursors were designed and synthesized successfully by metal–organic-gel method. • The HEC nanoparticles with high purity, regular morphology and fine particle size of 40 nm were prepared only at 1300 ℃. • Densified HEC ceramics exhibit high Vickers hardness (22.3 ± 0.5 GPa) and fracture toughness (4.1 ± 0.1 MPa·m 1/2 ). In this work, the (ZrHfNbTaCr)C high-entropy precursors were synthesized via a novel metal–organic-gel (MOG) strategy using pyromellitic acid as dual-functional carbon source and chelating agent, with transition metal chlorides (ZrCl 4 , HfCl 4 , NbCl 5 , TaCl 5 , CrCl 3 ) serving as metal source. The as-synthesized precursors were converted successfully into single-phase nanoparticles featuring regular morphology, average particle size of only about 40 nm and uniform elemental distribution by pyrolysis in vacuum at 1300 ℃. Through spark plasma sintering at 1950 ℃ for 1 h under 40 MPa pressure, the as-prepared nanoparticles were consolidated into dense ceramics achieving relative density of 99.3 %, while maintaining submicrometer-scale grain size of 0.48 ± 0.2 μm. The resultant ceramics exhibited enhanced mechanical properties, demonstrating the Vickers hardness of 22.3 ± 0.5 GPa coupled with the fracture toughness of 4.1 ± 0.1 MPa·m 1/2 . The process provide potential for the research and application of high-entropy carbide ceramics and composites.