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This work continues the earlier studies focusing on fabrication of heterophase micropowders and consolidated ceramics based on HfB2–HfC–SiC ultra-high-temperature boride/carbide compositions via self-propagating high-temperature synthesis (SHS) and hot pressing (HP). The effect of NH4Cl addition on the morphology and microstructure of the SHS powders was studied. Composite micropowders characterized by particle size of 0.2–10 μm and 40–50% content of the submicron-sized fraction were fabricated. The structure, mechanical and thermophysical properties, kinetics and mechanism of high-temperature oxidation of hot-pressed ceramic materials composed of 57–72 wt % HfB2, 14–20 wt % HfCx, 10–14 wt % SiC, and 8–15 wt % HfO2 were studied. They are found to have hardness up to 18.9 GPa, crack resistance up to 9.7 MPa m0.5, bending strength up to 400 MPa, temperature diffusivity up to 22.6 mm2/s, and thermal conductivity up to 59 W/(m K). The power law describes their oxidation kinetics. The protection mechanism against oxidation involves the formation of a multilayered heterogenous oxide film consisting of HfO2, HfSiO4, and borosilicate glass. [ABSTRACT FROM AUTHOR]

This work is devoted to the production of a ceramic target (ZrSi2–ZrB2–MoSi2)/Cr by hot pressing of products of self-propagating high-temperature synthesis and deposition of coatings in the Zr–Si–Mo–B system by DC magnetron sputtering and high-power pulsed magnetron sputtering. The composition and structure of the initial powder mixtures, SHS products, a two-layer functionally graded target, and coatings deposited during its sputtering have been studied. It is shown that the developed target (ZrSi2–ZrB2–MoSi2)/Cr can be successfully used to obtain coatings with a dense homogeneous defect-free structure, including at high-energy sputtering regimes, peak current of 50 A, and peak power of 50 kW. [ABSTRACT FROM AUTHOR]

This paper presents an in-depth study on the combustion synthesis, solid-solution formation, processing, and characterization of NbB2–HfB2 ceramics, aiming to explore their potential applications, particularly in industries requiring high-performance materials. We conducted macrokinetic measurements and fitted regression models to predict combustion temperature and velocity for compositions ranging from 50 to 100% HfB2. A combined method of ball milling and hot pressing was developed for processing the combustion products into dense ceramics. These methods resulted in samples with relative densities reaching 97%, hardness of up to 34 GPa, and Young's modulus of up to 530 GPa, with NbB2–50% HfB2 solid solution exhibiting the best mechanical properties. The study revealed a linear increase in thermal properties and density with the rise in HfB2 content. The thermal conductivity of the solid solutions in the Nb–Hf–B system ranged from 34 to 40 W/mK and was found to increase with temperature, making these ceramics suitable for ultra-high-temperature applications. The findings have significant implications for aerospace and high-performance engineering sectors and provide a solid foundation for further investigation of Nb–Hf–B ceramics under real-world operational conditions. [ABSTRACT FROM AUTHOR]

Porous sintered solid solutions (Hf1 –хTaх)B2 were synthesized from elements by self-propagating high-temperature synthesis and were then ground in a ball mill to fraction d50 < 10 μm. Compacts were hot-pressed from single-phase solid solutions of various stoichiometries (Hf1 –хTaх)B2, and their structure and properties were studied. The constructed dependences of the unit cell parameters on the parameter x confirmed that they obey Vegard's law. Analysis of the microstructure by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy confirmed the existence of a region of single-phase solutions between the HfВ2 and TaB2 phases. Lamellas made of (Hf0.8Ta0.2)B2 and (Hf0.6Ta0.4)B2 compacts were studied by transmission electron microscopy. It was determined that, with an increase in the tantalum content, the size of subgrains decreases to 0.2–1 μm, which correlates with the size of coherent scattering regions. The mechanical properties of the single-phase solid solutions were measured. It was shown that the solid solutions of the compositions (Hf0.8Ta0.2)B2 and (Hf0.6Ta0.4)B2 have record-high values of hardness (63–70 GPa) and elastic modulus (550–587 GPa). The temperature dependence of the electrical resistance was constructed, and the heat capacity, thermal diffusivity, and thermal conductivity were determined in over a wide range of compositions of solid solutions (Hf1 –xTax)B2, where x = 0–0.9. [ABSTRACT FROM AUTHOR]