Niobium (Nb) is a refractory metal with a high melting point (2468°C), moderate density, corrosion resistance, radiation resistance, high temperature strength, and good high temperature mechanical properties. The excellent properties of niobium and niobium alloys make it one of the important candidate materials for high-temperature structural parts in the aviation, aerospace and nuclear industries, and can be used to manufacture key components such as rocket engines and nuclear reactors. However, its oxidation performance is poor. Pure niobium undergoes "pest" oxidation at 600°C. As the temperature increases, the degree of oxidation intensifies, eventually leading to the failure of its high-temperature performance. This shortcoming severely restricts niobium and niobium. Application of alloys. In order to improve its high temperature oxidation resistance, surface coating protection is a practical and effective way to balance the high temperature mechanical properties and oxidation resistance of niobium and niobium alloys. When niobium silicide (NbSi2) is oxidized, SiO2 oxide film can be formed on the surface. The oxide film is dense, self-healing, and has good high temperature oxidation resistance, making NbSi2 the main choice for high temperature protective coatings for niobium and niobium alloys.

What is the application of niobium silicide in materials?

1. Synthetic niobium/niobium silicide composite material. Nb/Si binary alloy matrix composite material is a promising high-temperature structural material, in which solid solution niobium provides room temperature toughness and Nb5Si3 provides high temperature strength , This composite material has a high degree of thermodynamic stability and microstructure stability at high temperatures. Units such as the Japan Institute of Ultra-High Temperature Materials have studied the preparation of niobium/niobium silicide composite materials by reactive hot pressing of ball-milled powders, and have studied and evaluated their microstructure and mechanical properties. In this study, the ball milling process is used as a pretreatment method to improve the subsequent reaction sintering effect. The powder used for the experimental study used elemental niobium powder (purity 99.9%, particle size <325 mesh), semiconductor grade silicon (particle size <300 mesh), according to Nb-3.5%Si, Nb-6%Si, Nb-10%Si After mixing with Nb-16%Si (both mole percentages), ball milling is carried out in a planetary ball mill. The weight ratio of the grinding ball (stainless steel ball with a diameter of 10mm) to the mixed powder is about 4:1. After ball milling the powder for a certain period of time (1～110h), hot-press vacuum sintering (sintering at 40MPa, 1773K for 3h) in a graphite mold. The hot briquette was annealed to study the changes in microstructure and mechanical properties.

2. Prepare a ceramic aluminum plate. Including the following raw materials in parts by weight: 800-1000 parts of clay, 50-100 parts of aluminum, 20-30 parts of carbon, 5-8 parts of tungsten, 3-5 parts of titanium, 8-10 parts of nickel, 10-parts of niobium silicide 15 parts, molybdenum boride 15-20 parts, titanium carbide 5-10 parts, titanium nitride 2-5 parts, molybdenum 5-8 parts, zircon sand 10-20 parts, glass fiber 10-15 parts and water 500- 1000 copies. The ceramic aluminum plate has better heat resistance through the addition of carbon, tungsten, titanium, nickel, niobium silicide and molybdenum boride, and is also added with titanium carbide, titanium nitride, molybdenum, zircon sand and glass fiber , The hardness of the ceramic aluminum plate is higher, not only can prevent the ceramic aluminum plate from being broken due to bumps, but also make the ceramic aluminum plate can withstand higher temperatures, and will not be damaged due to high temperature during use. The scope of application reduces the use cost of ceramic aluminum plates.

3. Prepare an alumina ceramic material with good toughness. It is composed of the following raw materials in parts by weight: 95-97 parts of alumina, 1-2 parts of light calcium carbonate, 1.5-3.2 parts of kaolin, 0.7-1.8 parts of boehmite, 0.5-0.9 parts of zirconium nitride, 0.8 parts of chromium powder -1.4 parts, 0.3-0.6 parts of niobium silicide. The invention also provides a preparation method of the alumina ceramic material with good toughness. The prepared alumina ceramic material with good toughness has good toughness and thermal shock resistance, and is low in production cost, which is conducive to the further expansion of the application range of the alumina ceramic material and has a broad market prospect.

4. Prepare a silicon-germanium alloy-based thermoelectric element. The silicon-germanium alloy-based thermoelectric element is composed of an electrode layer, a silicon-germanium alloy-based thermoelectric layer, and a barrier layer between the electrode layer and the silicon-germanium alloy-based thermoelectric layer. The barrier layer is a mixture of silicide and silicon nitride, The silicide is at least one of molybdenum silicide, tungsten silicide, cobalt silicide, nickel silicide, niobium silicide, zirconium silicide, tantalum silicide, and hafnium silicide. The silicon-germanium alloy-based thermoelectric element provided by the present invention has a good combination of interfaces, no cracks and obvious diffusion phenomena at the interface, low contact resistance, good thermal contact state, and can withstand long-term high-temperature accelerated tests. In addition, the provided preparation method has the characteristics of simple process, high reliability, low cost, no need of special equipment, and suitable for large-scale production.

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