Dr. Tetiana Prikhna

Abstract:

The sintering processes of TaB₂ and TaB₂ mixtures with 20 and 30 wt. % SiC, ZrSi₂, Si₃N₄, and MoSi₂ were investigated under hot pressing (HotP) conditions at 30 MPa, 1750-1970 °C, 0.33 - 1.0 h, and high pressure–high temperature (HP-HT) conditions at 4.1 GPa, 1800 °C, 0.33 h,, as well as TaB₂ and its mixtures with 20 and 30 wt.% SiC under spark plasma sintering (SPS) at 45 MPa, 1500-1950 °C, 0.05 h. The highest values of mechanical characteristics of single-phase TaB₂ samples were achieved after sintering by the HotP (1900 °C, 1 h) – Vickers hardness Н_V(9.8 N) = 32.4 ± 0.1 GPa (density r =11.8 g/cm³) and SPS (1950 °C, 0.05 h) - Н_V(49 N) = 20.8 ± 2.0 GPa and K_1C(49 N)= 7.6 ± 1.6 MPa•m^0.5 (r =11.75 g/cm³). A significant improvement in Young's modulus from 532 GPa to 853 GPa was achieved by adding 20 wt.% SiC and HotP at 1900, 1 h. By sintering mixtures with 30 wt.% SiC using the HP-HT and SPS methods at 1800 °C for 0.13 and 0.05 h, respectively, the following materials were obtained: with Н_V(9.8 N)= 39.4 GPa and K_1C(9.8 N)=6.75 MPa•m^0.5 (HotP) and Н_V(49 N)=25.4±2.1 GPa and K_1C(49 N)=10.8±0.8 MPa•m^0.5 (SPS). The variation in the properties of the materials upon addition of additives is explained by the formation of solid solutions due to the diffusion during sintering of the present elements and different porosity. When adding 30 wt.% SiC after HotP (1900 °C, 1 h), the approximate stoichiometric composition of the matrix phase of the sample estimated by SEM EDX was TaB₂Si_0.5O_0.06.