Properties and application fields of silicon nitride ceramics

Overview of Silicon Nitride Si3N4

Silicon nitride is an inorganic substance with the chemical formula Si3N4. It is an important structural ceramic material with high hardness, inherent lubricity, wear resistance, atomic crystals and high temperature oxidation resistance. Moreover, it can resist the impact of cold and heat. It will not be broken if it is heated to above 1000°C in the air, cooled rapidly and then heated rapidly. It is precisely because of the excellent characteristics of silicon nitride ceramic that people often use it to manufacture mechanical components such as bearings, turbine blades, mechanical seal rings, permanent molds, and so on. If silicon nitride ceramics, which are resistant to high temperatures and difficult to transfer heat, are used to make the heating surfaces of engine components, not only can the quality of the diesel engine be improved, fuel savings, and thermal efficiency can be improved. China, the United States, Japan and other countries have developed such diesel engines.

Properties and application fields of silicon nitride ceramics

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 falling. 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%, it can also withstand the corrosion of many organic acids; at the same time, it is a high-performance electrical insulating material.

The nature of silicon nitride, chemical formula Si3N4. White powdery crystal; melting point 1900℃, density 3.44 g/cm (20℃); There are two variants: α type is hexagonal close-packed structure; β type is spar-like structure. Silicon nitride is gray when it has impurities or excess silicon.

Silicon nitride hardly interacts with water; it is slowly hydrolyzed in a strong acid solution to generate ammonium salt and silicon dioxide; it is easily soluble in hydrofluoric acid, and does not work with dilute acid. The strong alkali solution can slowly corrode silicon nitride, and the molten alkali can quickly transform 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 reaction occurs between silicon nitride and calcium dinitride Ca3N2 at 1285℃:

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 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 cutting tools, pump plungers, and mandrel sealing materials.

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 a low friction coefficient and are self-lubricating. It is stable to most metal 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.

1. The physical and chemical properties of silicon nitride ceramic powder and the technical indicators of the product

Silicon nitride ceramics is a white-gray powder with the molecular formula: SI3N4;

Molecular weight: 140.3, density 3.2g/cm³

Its chemical composition: N>38-39; 0<1-1.5; C<0.1; Fe<0.2.

The granularity is determined by user requirements.

Application of silicon nitride Si3N4

It is widely used in many fields such as high-tech structural ceramics, various wear-resistant materials, and refractory materials. Mainly used in photovoltaic, bearing, metallurgy, chemical industry, energy, environmental protection, aerospace and defense military, and new energy vehicle inverters and other new energy and new materials.

1) Manufacturing structural equipment: metallurgy, machinery, aviation, aerospace, etc.

2) Surface treatment of metals and other materials: such as molds, knives, turbine blades.

3) Composite materials: such as metal, ceramic and graphite composite materials, rubber, and plastics.

4) Colorless, transparent, self-lubricating and wear-resistant nano-particle film, used for high-level surface protection such as mobile phones and automobiles.

5) Ball bearings.

6) Ball valves and parts.

7) Corrosion resistant turbine.

Application of Silicon Nitride Si3N4 Ceramic Materials

Silicon nitride Si3N4 is used as a high-grade refractory material. For example, SI3N4-SIC refractory materials and sic are used in blast furnace bodies and other parts, and SI3N4-BN materials and BN are used in horizontal continuous casting separation rings. The continuous casting separation ring is a fine-structure ceramic material with uniform structure, high mechanical strength, good thermal shock resistance, and will not be wetted by molten steel, which meets the requirements of continuous casting process

Silicon nitride Si3N4 ceramic material has excellent properties such as high thermal stability, strong oxidation resistance, and high product dimensional accuracy. Since silicon nitride is a covalent compound with high bonding strength, it can form an oxide protective film in the air, so it also has good chemical stability and will not be oxidized below 1200°C. The protective film formed at 1200~1600°C can prevent further oxidation and will not be affected by aluminum, lead, tin, silver, brass, and nickel. Or corrosion, but can be corroded by molten magnesium, nickel-chromium alloy, stainless steel and other melts.

Silicon nitride Si3N4 ceramic materials can be used for high-temperature engineering parts, advanced refractories in the metallurgical industry, corrosion-resistant parts and seals in the chemical industry, tools and knives in the machining industry, etc. Carbide, aluminum oxide, thorium dioxide, boron nitride, etc. can form a firm bond, so it can be used as a bonding material to be modified in different proportions.

In addition, silicon nitride can also be applied to solar cells. After the silicon nitride film is coated by the PECVD method, it can not only be used as an anti-reflection film to reduce the reflection of incident light, but also in the deposition process of the silicon nitride film, the hydrogen atoms of the reaction product enter the silicon nitride film and the silicon wafer passivation Defects. The ratio of the number of silicon nitride to silicon atoms here is not strictly 4:3, but depends on the process conditions within a certain range. Internal fluctuations, different atomic ratios correspond to different physical properties of the film.

Used in ultra-high temperature gas turbines, aircraft engines, electric furnaces, etc.

Silicon nitride Si3N4 price

The price of silicon nitride Si3N4 will vary randomly with the production cost, transportation cost, international situation, exchange rate and the supply and demand of silicon nitride Si3N4 market. Tanki New Materials Co., Ltd. aims to help various industries and chemical wholesalers find high-quality, low-cost nanomaterials and chemicals by providing a full set of customized services. If you are looking for silicon nitride Si3N4, please feel free to send an inquiry to get the latest price of silicon nitride Si3N4.

Suppliers of Silicon Nitride Si3N4

As a global silicon nitride Si3N4 supplier, Tanki New Materials Co., Ltd. has extensive experience in the performance, application and cost-effective manufacturing of advanced engineering materials. The company has successfully developed a series of powder materials (titanium nitride, silicon nitride, titanium nitride, etc.) high-purity targets, functional ceramics and structural devices, and provides OEM services.