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One of the most promising applications of high entropy ceramics is their use as high temperature protective materials. Due to the additional entropic stabilization of the crystal structure, four- and five-element high entropy ceramics exhibit enhanced thermal and mechanical properties. For these applications, one of the most promising high entropy protective oxides are ZrO2- and HfO2-based protective HEOs. In this article, we study the HfO2–ZrO2–Y2O3–CeO2 equimolar system with the addition of MgO as a fifth component. We found that the HfZrCeY(Mg)O system maintains a single FCC crystalline structure up to the MgO concentration = 31.9 mol.%. Additionally, we determined that an addition of MgO at the close-to-equimolar HfZrCeY(Mg)O composition enhances the thermal properties of HEO, but reduces the mechanical properties such as hardness and resistance to crack formation. The minimum weight loss at the heating from RT up to 1450 °C was measured for the close-to-equimolar HfZrCeY(Mg)O composition at 18.4 mol.% MgO. The hardness of such composition was around 18 GPa. Due to the combination of these properties, the synthesized coating can be used as a protective material for high temperature applications, such as the protection of turbine parts.

The influence of CH4 and N2 concentration in CH4/H2/N2gas mixture on microstructure and mechanical properties of diamond films is investigated. Nitrogen addition to the gas mixture up to 18.5 vol. % does not significantly affect the structure of the coating. In the entire range of gas concentrations, coating structure is represented by a set of dendrites consisting of diamond crystallites of various sizes, as well as non-diamond carbon. It is shown that CH4 has a greater effect on the coating hardness and Young's modulus. Besides, it has been found that nitrogen-doped diamond coatings have a higher level of tensile residual stress. With a decrease in coating thickness or nitrogen concentration in the gas mixture, this difference decreases.

In this article we show the optical, mechanical and surface properties change depending on the Hf-Zr-Ce-Y-O thin film composition. Hf4Zr4CeY2O21shows up to three times higher hardness compared to binary HfZrO4oxide and up to 50% higher hardness compared to cubic ZrO2 and HfO2due to the solid solution hardening effect. Equimolar film exhibit a high transmittance >85% and high hydrophobicity with the water contact angle ≈106°. Variation of the elemental composition in Hf-Zr-Ce-Y-O is allows to simultaneously tune mechanical and wetting properties for the optimum configuration depending on the application.