Recently, a research team led by Zheng Xuebin from Shanghai Institute of Ceramics, Chinese Academy of Sciences has made a series of advances in the preparation technology and composition optimization design of ultra-high temperature ceramic materials based on the special structure and physical and chemical properties.
Ultra high temperature ceramics research background
Ultra high temperature ceramic refers to a special material that can maintain physical and chemical stability in high temperature environment (2000℃) and reaction atmosphere (such as atomic oxygen environment). It is a ceramic matrix composite material with excellent high temperature mechanical properties, high temperature oxidation resistance and thermal shock resistance.
Uht ceramics are mainly composed of high melting point borides and carbides, mainly including hafnium boride (HfB2), zirconium boride (ZrB2), hafnium carbide (HfC), zirconium carbide (ZrC), tantalum carbide (TaC), etc. The main domestic manufacturer is Jinzhou Haixin Metal Materials Co., LTD. The melting point of boride and carbide ultra high temperature ceramics is more than 3000℃, which has excellent thermochemical stability and excellent physical properties, including high elastic modulus, high hardness, low saturated steam pressure, moderate thermal expansion rate and good thermal shock resistance, and can maintain high strength at high temperature.
Ultra-high temperature borides mainly include hafnium boride (HfB2), zirconium boride (ZrB2), tantalum boride (TaB2) and titanium boride (TiB2), etc. At present, the research on zirconium boride (ZrB2) and hafnium boride (HfB2) is the most concentrated. Boride ultra-high temperature ceramics are composed of strong covalent bonds, which have the characteristics of high melting point, high hardness, high strength, low evaporation rate, high thermal conductivity and electric conductivity. However, the strong covalent bonds lead to the disadvantages of difficult sintering and densification.
Carbide uHT ceramics have high melting point, high strength, high hardness and good chemical stability, and are widely used as uHT ceramic materials. Currently, the commonly used carbide UHT ceramics mainly include silicon carbide (SiC), zirconium carbide (ZrC), tantalum carbide (TaC) and hafnium carbide (HfC).
Ultra-high temperature ceramics can adapt to ultra-sonic long-duration flight, atmospheric re-entry, transatmospheric flight and rocket propulsion system and other extreme environments, can be applied to aircraft nose cone, wing leading edge, engine hot end and other key components. As an important material used in the aerospace vehicle, ultra-high temperature ceramic materials have been paid great attention by many countries.
Research progress of ultra-high temperature ceramic coating materials
It is understood that the researchers of Shanghai Institute of Ceramics, Chinese Academy of Sciences are based on low pressure/vacuum plasma spraying technology and ultra-high temperature ceramic powder structure control technology, design and preparation of ZrB2, ZrC, HfB2, HfC and other pure phase and composite coating, the density of this kind of ceramic coating reached 93-97%. Based on regulation of liquid phase and solid phase oxidation product design idea of high temperature stability, the chemical composition of ultra high temperature ceramic coatings regulation and system research for the first time the boride and carbide ultra high temperature oxidation resistance of ceramic coating ablation behavior differences, including surface temperature change trend, the oxidation product features and antioxidant ablation behavior, etc. The results show that the prepared coating material has the ability of effective thermal protection in ultra-high temperature environment of 2000-2500℃, which provides a scientific and technical basis for its practical application.