Polymer-derived W-doping (Zr, Hf, Nb, Ta)C high entropy ceramics: Preparation, Properties and DFT calculation

(Zr, Hf, Nb, Ta, W)C high entropy carbides nano -powders (average particle size less than 65 nm) with low oxygen content (0.2-1.4 wt%) were synthesized through pyrolysis of polymer precursors. Bulk ceramics were fabricated through the process of hot -pressing, and their characteristics were studied by both computational and experimental methods. Density functional theory was carried out to analyze the effects of defects and the W element on the melting point, hardness, modulus, and toughness of ceramics. The results showed that W content had limited influence on the melting points and the aforementioned mechanical properties of ceramics, while carbon vacancies lead to a significant decrease in melting point, hardness and modulus, with slight increases in toughness. Experimental results indicated that the grain size, grain boundary strength, and lattice distortion of ceramic bulks increased with the increase of W content, which affected the mechanical properties consequently. Ceramics with W content of 5 mol% exhibited the best experimental comprehensive performances, with the Vickers hardness, fracture toughness and flexural strength of 23.82 +/- 0.49 GPa, 5.66 +/- 0.22 MPa & sdot;m1/2 and 593.95 +/- 15.71 MPa, respectively.