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Material properties of silicon nitride

wallpapers News 2021-12-08
Silicon nitride is very strong, especially hot-pressed silicon nitride, which is one of the hardest materials in the world. It is extremely resistant to high temperatures, and its strength can be maintained to a high temperature of 1200°C without loss. It will not melt into a melt after being heated, and will not decompose until 1900°C. It has amazing chemical corrosion resistance and can withstand almost all inorganic acids. And caustic soda solution below 30% can also withstand the corrosion of many organic acids; at the same time, it is a high-performance electrical insulating material.
Silicon nitride hardly interacts with water. In a strong acid solution, silicon nitride is slowly hydrolyzed to produce ammonium salt and silicon dioxide. Silicon nitride is easily soluble in hydrofluoric acid and has no effect on dilute acid. The strong alkali solution can slowly corrode silicon nitride, and the molten alkali can quickly convert silicon nitride into silicate and ammonia. Silicon nitride can reduce transition metal (see transition element) oxides, lead oxide, zinc oxide, and tin dioxide at temperatures above 600°C, and release nitrogen oxide and nitrogen dioxide. The following reactions occur between silicon nitride and calcium dinitride Ca3N2 at 1285°C:
Ca3N2+Si3N4─→3CaSiN2
There are several methods for preparing silicon nitride: reacting powdered silicon with nitrogen at 1300~1400°C; reacting pure silicon with ammonia at 1500°C.
The mixture of silicon dioxide and carbon is burnt in nitrogen-containing a small amount of hydrogen; the ammonolysis product Si(NH2)4 of SiCl4 is completely thermally decomposed. Silicon nitride can be used as a catalyst carrier, high-temperature resistant material, coating, and abrasive.
Silicon nitride ceramics have the characteristics of high strength and high-temperature resistance. Among the ceramic materials, it has the best comprehensive mechanical properties, thermal shock resistance, oxidation resistance, abrasion resistance, and corrosion resistance. It is the first ceramic used in thermomechanical components. A candidate material. In the machinery industry, silicon nitride ceramics are used as bearing balls, rollers, ball races, molds, new ceramic tools, pump plungers, mandrel sealing materials, etc.
In the chemical industry, silicon nitride ceramics are used as wear-resistant and corrosion-resistant parts. Such as ball valves, pump bodies, combustion vaporizers, filters, etc.
In the metallurgical industry, silicon nitride ceramics are resistant to high temperatures, have low friction coefficients, and are self-lubricating. It is stable to most metals and alloy solutions. Therefore, it can be used to produce metal material processing tools and dies, such as dial mandrels, extrusion, and wire drawing dies, rollers, transfer rollers, heating element fixtures, thermocouple sets, metal heat treatment supports, Crucible, aluminum liquid guide camp, aluminum cladding lining, etc.
Silicon nitride ceramic materials are also widely used in electronics, military, and nuclear industries

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