Unlocking ultrastrong high-temperature ceramics: Beyond Equimolar Compositions in High Entropy Nitrides

Traditionally, increasing compositional complexity and chemical diversity of high entropy alloy ceramics whilst maintaining a stable single-phase solid solution has been a primary design strategy for the development of new ceramics. However, only a handful have shown properties that justify the increased alloying content. Here, we unveil a groundbreaking strategy based on deviation from conventional equimolar composition towards non-equimolar composition space, enabling tuning the metastability level of the supersaturated single-phase solid solution. By employing high-temperature micromechanical testing of refractory metal-based high entropy nitrides, we found that the activation of an additional strengthening mechanism upon metastable phase decomposition propels the yield strength of a non-equimolar nitride at 1000 C to a staggering 6.9 GPa, that is 30 % higher than the most robust equimolar nitride. We show that the inherent instability triggers the decomposition of the solid solution with non-equimolar composition at high temperatures, inducing strengthening due to the coherency stress of a spinodally modulated structure, combined with the lattice resistance of the product solid solution phase. In stark contrast, the strength of equimolar systems, boasting diverse chemical compositions, declines as a function of temperature due to the weakening of the lattice resistance and the absence of other strengthening mechanisms.Comment: 17 pages, 4 figures, 25 supplementary pages, 19 supplementary figures, 1 Supplementary Tabl

Influence of ion implantation on the physical and mechanical properties of multifunctional coatings based on Ti-Si-N

Current paper presents the results of investigating of multifunctional Ti-Si-N coatings. Ti-Si-N coatings have been deposited using CAVD method with the aim of studying their chemical, physical, structural and mechanical properties. Coatings of Ti-Si-N were modified by high-intensity ion implantation using copper ions with dose D = 2 × 1017 ions/cm2 and energy E = 60 keV. The results demonstrated that ion implantation has effect on grain size, hardness, and Young modulus of the Ti-Si-N coating

High Temperature Annealing of Ion-Plasma Nanostructured Coatings Based on AlN−TiB2(TiSi2)AlN-TiB_2(TiSi_2)

The coatings investigated in this paper were deposited via the magnetron sputtering of $AlN-TiB_2-Ti-Si_2$ target in Ar atmosphere. The investigation of structural-phase composition, element composition, morphology and mechanical properties before and after annealing up to 1350°C was carried out. The concentration of elements in the coating was changed after annealing at 900°C and further annealing at 1350°C (especially after annealing at 1350°C). The hardness of as-deposited coatings was 15 GPa, but after annealing at 1350°C the value of hardness increased up to 22÷23.5 GPa. The value of the viscoplastic index was 0.07. All this provide high damping properties of the coating, and amorphous-like structure makes promising the use of these coatings as diffusion barriers in the form of independent elements, and as a contacting layer in multilayer wear resistant coatings