Niobium (Nb) is a kind of refractory metal with high melting point (2468℃), moderate density, corrosion resistance, radiation resistance, and high temperature strength, with good mechanical properties at high temperature. The excellent properties of niobium and niobium alloy make it one of the important candidate materials for high-temperature structural parts in aviation, aerospace and nuclear industry, which can be used to manufacture rocket engines, nuclear reactors and other key components. However, its poor oxidation performance, pure niobium at 600℃ “pest” oxidation phenomenon, and with the rise of temperature, the degree of oxidation, and eventually lead to the failure of its high temperature performance, this defect seriously restricted the application of niobium and niobium alloy. In order to improve its high temperature oxidation resistance, surface coating protection is an effective way to combine the high temperature mechanical properties and oxidation resistance of niobium and niobium alloy. When niobium silicide (NbSi2) is oxidized, SiO2 oxide film can be formed on the surface. The oxide film is dense and has the ability of self-healing, and has a good oxidation resistance at high temperature. Therefore, NbSi2 becomes the main choice of niobium and niobium alloy high-temperature protective coating.
Nb/ Si binary alloy matrix composite 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 high thermodynamic stability and microstructure stability at high temperature. Niobium/niobium silicide (niobium/niobium silicide) composites were prepared by the reaction hot pressing method of ball grinding powder, and their microstructure and mechanical properties were evaluated. In this study, the ball grinding process was used as a pretreatment method to improve the subsequent reaction sintering effect. Used for powder using the elements of the experimental study of niobium powder (99.9% purity, particle size < 325 mesh), semiconductor grade silicon (particle size < 300 mesh), according to the Nb – 3.5% Si Si, Nb, Nb – 6% – 10% Si Si and Nb – 16% (percentage of mo l) after proportioning, in a planetary ball mill for ball mill, grinding ball (10 mm diameter stainless steel ball) and mixed powder weight ratio of about 4:1. After ball grinding for a certain period of time (1 ~ 110h), the powder was hot pressed and vacuum sintered in graphite mold (sintered at 40MPa and 1773K for 3h). The changes of microstructure and mechanical properties of hot – pressing block were studied after annealing.
2. Preparation of a ceramic aluminum plate. The raw materials include: 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, 10-15 parts of niobium silicide, 15-20 parts of molybdenum boride, 5-10 parts of titanium carbide, 2-5 parts of titanium nitride, 5-8 parts of molybdenum, 10-20 parts of zirconium sand, 10-20 parts of glass fiber and 500-1000 parts of water. The ceramic aluminum plate by carbon, tungsten, titanium, nickel, molybdenum, niobium silicide and boride are added, make ceramic aluminum plate heat resistance is better, but also add the titanium carbide, titanium nitride, molybdenum, zirconium English sand and glass fiber, make ceramic aluminum plate hardness is higher, not only can more effectively prevent ceramic aluminum plate broken by knock against, and make the ceramic aluminum plate can withstand higher temperatures, will not damage in the process of use because of high temperature, increase the application range of ceramic aluminum plate, reduce the use of ceramic aluminum plate cost.
3. Preparation of alumina ceramic material with good toughness. It consists of the following raw materials according to 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 bomolite, 0.5-0.9 parts of zirconium nitride, 0.8-1.4 parts of chromium powder, 0.3-0.6 parts of niobium silicide. The invention also provides a preparation method of the alumina ceramic material with good toughness. The alumina ceramic materials with good toughness have good toughness and thermal shock resistance and low production cost, which is conducive to the further expansion of the application range of alumina ceramic materials and has a broad market prospect.
4. Preparation of a silicon-germanium alloy based thermoelectric element. Silicon germanium alloy base thermoelectric elements described by electrode layer, silicon germanium alloy base thermoelectric and the electrode layer and the silicon germanium alloy base thermoelectric layer between the barrier layer, described in the barrier layer for the silicide with a mixture of silicon nitride, described silicide for molybdenum silicide, tungsten silicide, silicide cobalt, nickel silicide, silicide niobium, zirconium silicide, tantalum silicide, silicide hafnium in at least one. The silicon-germanium alloy based thermoelectric element provided by the invention has a good combination of all aspects, no cracks and obvious diffusion phenomenon at the interface, small contact resistance, good thermal contact state, and can withstand a long time high temperature acceleration test. In addition, the preparation method provided 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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