What is silicon nitride ceramic

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Silicon nitride ceramics (Si ∝ N ₄) are covalent compounds composed of silicon and nitrogen elements, with excellent comprehensive properties, and are widely used in multiple high-tech fields.

1、 Material characteristics
-High strength and toughness: Silicon nitride ceramics can still maintain high strength and toughness at high temperatures, with a bending strength of over 350MPa. Even at high temperatures of 1200 ℃, their strength will not significantly decrease.
-Low coefficient of thermal expansion: Silicon nitride has a low coefficient of thermal expansion, which means it deforms less at high temperatures, making it particularly suitable for high-temperature applications that require stable size and shape.
-Excellent thermal shock resistance: Silicon nitride ceramics can maintain their strength and integrity under rapid temperature changes, making them suitable for equipment that requires frequent temperature cycling.
-Good wear resistance and self-lubricating properties: Silicon nitride ceramics have high hardness, self-lubricating properties, and excellent wear resistance, making them suitable for manufacturing components such as bearings and mechanical seal rings.
-Chemical corrosion resistance: Silicon nitride ceramics have good corrosion resistance to most inorganic acids and certain bases, and hardly react with other inorganic acids except hydrofluoric acid.
-Electrical Insulation: Silicon nitride ceramics are excellent electrical insulation materials suitable for electronic and semiconductor fields that require insulation properties.

2、 Preparation process
The preparation process of silicon nitride ceramics mainly includes three steps: powder preparation, molding, and sintering:

1. Powder preparation: Common preparation methods include silicon powder nitriding, liquid-phase reaction, and self propagating high-temperature synthesis.
2. Molding process: including dry pressing molding, cold isostatic pressing molding, casting molding, etc.
3. Sintering process: mainly includes hot pressing sintering, gas pressure sintering, hot isostatic pressing sintering, and discharge plasma sintering.

3、 Application Fields
-In the field of machinery, silicon nitride ceramics are widely used in the manufacturing of bearings, valves, pipelines, grading wheels, and ceramic cutting tools. Silicon nitride bearing balls are widely used in precision machine tool spindles, aerospace engines, and automotive engine bearings due to their low density, high hardness, and excellent wear resistance.
-Aerospace field: The high strength, low thermal expansion coefficient, and good thermal shock resistance of silicon nitride ceramics make them an ideal material for the aerospace field, such as combustion chamber parts, gas turbine blades, and transparent materials.
-Metallurgical industry: Silicon nitride ceramics can be used to manufacture temperature measuring thermocouple sleeves, furnace linings, crucibles, separation rings, etc., with good thermal shock resistance and wear resistance.
-Chemical industry: Silicon nitride ceramics can be used in industries such as aluminum smelting, steelmaking, and ironmaking, as refractory materials, pumps, pipelines, valves, and molds.
-In the semiconductor field, the electrical insulation and corrosion resistance of silicon nitride ceramics make them used as insulation substrates and high-temperature furnace linings in semiconductor manufacturing.
-New energy vehicles: Silicon nitride ceramic bearings are widely used in electric motor bearings for new energy vehicles due to their low density, high wear resistance, and good insulation performance.

Silicon nitride ceramics, with their excellent physical, chemical, and mechanical properties, have shown great potential for applications in many fields and are expected to play an important role in more high-tech fields in the future.