![]() Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Zhang, Baoxi Zhang, Xinghong Hong, Changqing Qiu, Yunfeng Zhang, Jia Han, Jiecai Hu, PingAn Compressive strength of the composites has been reported.Įlectrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance. Nanoindentation was used to measure elastic modulus. Fracture toughness and hardness were evaluated using indentation methods. Microstructure and phase analysis was carried out using X-ray diffractometer (XRD and electron microscopy to understand microstructure evolution. In this study, an attempt has been made to fabricate ZrB 2-TiB 2 ceramics using mechanically activated elemental powders followed by reactive spark plasma sintering (RSPS at 1400 Â☌. A composite of ZrB 2-TiB 2 is expected to have better properties. Reactive Spark Plasma Sintering and Mechanical Properties of Zirconium Diboride–Titanium Diboride Ultrahigh Temperature Ceramic Solid Solutionsĭirectory of Open Access Journals (Sweden)įull Text Available Ultrahigh temperature ceramics (UHTCs such as diborides of zirconium, hafnium tantalum and their composites are considered to be the candidate materials for thermal protection systems of hypersonic vehicles due to their exceptional combination of physical, chemical and mechanical properties. The research potentially offers a basis for future modeling of thermal conductivity in ultra-high temperature ceramics based on the correlation between metallic radius and the decrease in thermal conductivity. This research provided insight into how additives and impurities affect thermal transport in ZrB 2. Additional strain appeared to exist for additives when the stable TM boride for that metal had different crystal symmetries than ZrB 2. The decrease in thermal conductivity for individual additives correlated directly to the metallic radius of the additive. Rietveld refinement of x-ray diffraction data was used to determine the lattice parameters of the compositions. The phonon contribution to thermal conductivity was calculated by subtracting the electron contribution from the total thermal conductivity. The electron contribution to thermal conductivity was calculated from measured electrical resistivity according to the Wiedemann-Franz law. Thermal conductivities were calculated from the diffusivities, using temperature-dependent values for density and heat capacity. The room temperature thermal diffusivities of the compositions ranged from 0.331 cm 2/s for nominally pure ZrB 2 to 0.105 cm 2/s for (Zr,Cr)B 2 and converged around 0.155cm 2/s at higher temperatures for all compositions. The transition metals that were investigated were: Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, and Re. To achieve this, ZrB 2 with 0.5 wt% carbon, and 3 mol% of individual transition metal borides, was densified by hot-press sintering. The overall goal was to improve the understanding of how different transition metal (TM) additives influence thermal transport in ZrB 2. This research focuses on the thermal properties of zirconium diboride ( ZrB 2) based ceramics. Thermal properties of zirconium diboride - transition metal boride solid solutions It is concluded that these diborides as well as MgB sub 2 samples behave like simple metals in the normal state with usual Bloch-Grueneisen temperature dependence of resistivity and with Debye temperatures: 280, 460 and 440 K, for ZrB sub 2, NbB sub 2 and MgB sub 2, respectively At T close to T sub c H sub c sub 2 (T) demonstrates a downward curvature. The upper critical field H sub c sub 2 (T) is linear in temperature below T sub c. ![]() The temperature dependences of resistivity and ac susceptibility of these samples reveal superconducting transition of ZrB sub 2 with T sub c = 5.5 K, while NbB sub 2 and TaB sub 2 have been observed nonsuperconducting up to 0.37 K. Results on syntheses and electron transport properties of polycrystalline samples of diborides (AB sub 2) with different transition metals atoms (A = Zr, Nb, Ta) are reported. Electron transport in diborides: observation of superconductivity in ZrB sub 2
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