The physical and chemical properties of silicon nitride:
Molecular formula Si3N4, molecular weight of 140.28, according to the weight percentage, which accounted for 60.06% of silicon, nitrogen accounted for 39.94%. The two elements are closely related to the electric and negative, which is a compound of strong covalent bond (ionic bond only accounts for 30%). Color is gray, white or gray. Six party system. Hexahedral crystal. Density 3.44. The hardness of 9~9.5 is about 2200, and the microhardness is 32630MPa. Melting point 1900 C (under pressure). Usually decomposed at atmospheric pressure at 1900. The specific heat capacity is 0.71J/ (g, K). Generate heat for -751.57kJ/mol. The thermal conductivity is 16.7W/ (M / K). Linear expansion coefficient is 2.75 * 10-6/ C (20~1000 C). Insoluble in water. Soluble in hydrofluoric acid. Start oxidation in the air temperature 1300~1400. Specific volume resistance, 20, 1.4 x 105, m, 500 m, 4 x 108. Modulus of elasticity is 28420~46060MPa. Compressive strength of 490MPa (reactive sintering). 1285 when the degree of perturbation and two to two calcium reaction to generate two calcium calcium silicate, 600 degrees when the transition metal reduction, the release of nitrogen oxides. Bending strength is 147MPa. By heating in nitrogen silicon or silicon halide is reacted with ammonia produced. Silicon nitride has high hardness, high melting point, stable structure, good insulation properties and wear resistance; except hydrofluoric acid, it is not with other inorganic acid reaction, strong corrosion resistance, high temperature oxidation.
Silicon nitride and its deep processing products belong to the national industrial policy to encourage and support the high-tech materials.
Silicon nitride products have the following characteristics: saving resources, the production process without pollution, technology and capital intensive high value-added new materials products.
The production and use of silicon nitride:
Silicon nitride is grayish white, advanced inorganic non-metallic materials, has a very good application in steel smelting, refractory material, etc., at room temperature and high temperature resistant rubber, plastics, ceramics and other abrasive sealing is also widely used.
1, the main features. This product is a new type of material which is produced at the special atmosphere temperature. Main features: first, it has good corrosion resistance, thermal conductivity, heat shock and wear resistance. Can be used under the temperature of 1800 degrees celsius. Two is a good split endurance, very stable chemical composition and thermal conductivity. Three is a small expansion coefficient, thermal conductivity and strength of large advantages. Four is good at high temperature oxidation resistance.
2, advanced production technology. Silicon nitride production in our company adopts the international advanced production technology, to achieve stable production volume, can be long-term low price, high quality supply.
3, a wide range of products. Silicon nitride as a new material for modern industry found widely used in ceramics, refractory steel, metallurgy, nonferrous metal smelting, rubber and other industries. Such as:
1) in the non-ferrous industry, its corrosion resistance, erosion performance is very excellent, has been widely used.
2) in the iron and steel industry,
A, silicon nitride coatings can effectively solve the problem of loss of billet oxidation during heat treatment. The experimental results show that the nano silicate antioxidant coating and anti oxidation effect, oxide skin can make the original ordinary hot-rolled plate produced by 3%-5% to 0.1%-0.8%, the oxide skin of stainless steel hot rolled plate produced by 1%-3% below 0.2%.
B, silicon nitride gun mud. Containing silicon nitride stemming, will play the role of effective sintering activation, corrosion resistance and anti disruptive effect on the furnace or electric furnace can be used in the blast furnace mouth more stable sealed, and very easy to cut.
C, silicon nitride in HRB400 high strength hot rolled steel bar has a very good application. Si3N4 as a nitrogen adding agent, with the FeV for the production of V micro alloying grade III steel, excellent stability of the steel bar, is the production of HRB400 grade III reinforcement of a new alloying process.
D, silicon nitride in the nitrogen content in the unit of nitrogen content in the second only to BN, the price is low, there is a very high cost of nitrogen in the increase of nitrogen.
3) because the product has a good application in the new ceramics and composite materials, improve its corrosion resistance, thermal conductivity, heat resistance, wear resistance, high strength and so on.
4, the use of chemical properties. Silicon nitride has very high temperature stability. Under acidic conditions, the corrosion resistance of the high. At 500 degrees Celsius temperature, there is a high degree of resistance to alkali.
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