Some aspects of heat transfer upon the interaction between components with a sharp leading edge and high-enthalpy high-speed flow of dissociated air have been considered; some material characteristics, which should be primarily taken into account when prognosticating the behavior of materials that are promising for using as components of hypersonic flight vehicles, have been substantiated; specific features of the oxidation of materials based on zirconium and hafnium diborides have been touched briefly; the methods of increasing oxidation resistance of these materials that have been developed by various groups of researchers have been demonstrate; some works concerning the behavior of samples under the effect of high-enthalpy flows of dissociated air have been described, including those that simulate sharp leading domes and edges of wings of hypersonic flight vehicles.

Promising ultra-high-temperature ceramic materials for aerospace applications

Transition metal diborides in hexagonal AlB2 type structure typically form stable MB2 phases for group IV elements (M = Ti, Zr, Hf). For group V (M = V, Nb, Ta) and group VI (M = Cr, Mo, W) the sta ...

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Influence of boron vacancies on phase stability, bonding and structure of MB₂ (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with AlB₂ type structure.

Carbon is the sixth element of the periodic table with the ground state level 3P0 and electron configuration 1s 2 2s 2 2p 2, which is hybridized to form sp 1, sp 2 and sp 3 chemical bonds between atoms.

Carbon (Graphene/Graphite)

Authors have studied the interaction between high-melting compounds from various classes, such as transition-metal carbides, borides, nitrides, and silicides, and covalent-bonded B4C, SiC, Si3N4, AlN etc. (over 160 phase diagrams), ternary B4C-SiC-MedB2, SiC-TiC-TiB2 and other eutectics, which is important for optimizing the sintering temperature, material design and prediction of properties of many materials for high temperature applications including wear, aggressive, impact and radiation conditions. A vast identified group of eutectics with number of components n ≥ 2 has reduced eutectic temperature Тeut. (in some sistems reducing reaches 1200 °C). Noted, that increasing of n suppresses grain growth, which is particularly important for developing nanostructured ceramics via pressureless sintering and for controlling the ceramic's performance. Multiphase ceramics (SiC-TiC-TiB2, B4C-SiC-MedB2, B4C-W2B5-MedB2, B4C-LnB6-MedB2, etc.) feature improved mechanical parameters and high wear and impact resistance.

Nonoxide High-Melting Point Compounds as Materials for Extreme Conditions

Spark plasma sintering of SiC-LaB6 composite

The T-x phase diagram of the W2B5-ZrB2 join in the ternary system Zr-W-B is mapped out. W2B5 and ZrB2 form a eutectic at 20 mol % ZrB2 with a melting point of 2180°C.

Phase diagram of the W2B5-ZrB2 system

The T–x phase diagram of the SiC–LaB6 join in the quaternary system La–B–C–Si is mapped out. The join is shown to be pseudobinary, with simple eutectic phase relations. The eutectic is located at 74 mol % SiC and 26 mol % LaB6 , with a melting point of 2110 ± 20°C.

Phase Relations in the SiC–LaB6 System

The interaction was studied and the polythermic section B4C-LaB6 was constructed for the ternary system La-B-C described by a eutectic phase diagram.

S. S. Ordan’yan

Papers

Phase diagram of the W2B5-ZrB2 system

Phase Relations in the SiC–LaB6 System

Polythermic Section B4C-LaB6 in the Ternary System La-B-C