High-performance multifunctional (Hf _0.2Nb _0.2Ta _0.2Ti _0.2Zr _0.2)C high-entropy ceramic reinforced with low-loading 3D hybrid graphene–carbon nanotube

There has been growing interest in the high-entropy ceramic (HEC) recently owing to its tailorable compositions and microstructures, versatile properties, together with promising structural functional applications. However, inferior fracture toughness (KIC) damage tolerance restricted many practical applications of HEC. Herein, we addressed this challenge by incorporating a three-dimensional graphene–carbon nanotube (3D G–CNT) as toughening agent (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)C. The resulting enhanced 3D G–CNT/(Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)C featured an outstanding 8.23 MPa·m1/2, while remaining superior strength (763 MPa) hardness (24.7 GPa). An ultralow friction coefficient (0.15) coupled wear rate (w, 2.6×10−7 mm3/(N·m)) was obtained primarily function lubricating scrolls, which two-dimensional (2D) graphene acted tribolayer, one-dimensional (1D) carbon nanotubes nano ball bearings embedded inside. Strikingly, exhibited rather low thermal conductivity (κ) yet excellent electrical (σ, 1.3×106 S/m) comparison pure This study provided great potential for maximizing physical properties HEC various