Silicon nitride ceramics are a new type of ceramic material that, due to their unique properties and functions, have become an integral part of modern advanced science and technology. As a new ceramic material, silicon nitride ceramics are among the structural ceramics with the most outstanding comprehensive performance. They are regarded as one of the most promising high-temperature structural ceramic materials for future development and applications.

• Ultra-High Strength: Silicon nitride ceramics exhibit significantly higher strength compared to conventional ceramics.

• High Hardness: Their hardness reaches HRA91–93.

• Thermal Stability: They are resistant to oxidation at temperatures up to 1400°C.

• Excellent Thermal Shock Resistance: These ceramics can withstand rapid temperature changes without cracking or damage.

• Excellent Wear Resistance: Silicon nitride ceramics offer superior durability against abrasion.

• Self-Lubricating Properties: They exhibit good self-lubrication, reducing the need for external lubricants.

• Outstanding Insulation: These ceramics provide excellent electrical insulation.

• High Thermal Conductivity: They efficiently transfer heat, making them suitable for high-performance applications.

Compared to other ceramic materials, silicon nitride ceramics possess numerous superior properties, such as high theoretical thermal conductivity and excellent chemical stability. These characteristics make them a highly promising material for heat dissipation and packaging in high-speed circuits and high-power devices. They are expected to address the limitations of existing substrate materials like alumina and aluminum nitride, showing significant market potential in high-end semiconductor devices, particularly as substrates for high-power semiconductor components.

Silicon nitride ceramic substrates are used in a variety of high-performance applications due to their excellent thermal conductivity, high strength, and stability under extreme conditions. These substrates are ideal for use in high-power electronic devices, providing efficient heat dissipation and electrical insulation. They are especially valuable in the semiconductor industry, where they can be used as base materials for advanced power electronics, LEDs, and other high-performance components. Silicon nitride substrates offer improved reliability and longevity compared to traditional materials like alumina or aluminum nitride, making them a key material for next-generation technologies.

Due to the excellent properties of silicon nitride ceramics, including resistance to corrosion from non-ferrous metals, high-temperature stability, super-hard wear resistance, self-lubrication, thermal shock resistance, and resistance to high-temperature creep, they are ideal for use in various metallurgical applications. These include the manufacturing of thermocouple protection tubes for measuring molten aluminum temperature, iron separation rings, flowmeter covers, zinc flowmeters, aluminum liquid electromagnetic pumps, and vacuum aluminum crucibles, as well as other specialized components.

The aerospace industry has very stringent requirements for material performance. Silicon nitride, with its high-temperature strength, good fracture toughness, high hardness, high dielectric strength, excellent thermal shock resistance, and tribological properties, makes it an excellent choice for aerospace applications. It ensures outstanding mechanical reliability, wear resistance, and durability.

• Bearings

Due to silicon nitride ceramics’ ultra-hardness, wear resistance, and self-lubricating properties, bearings made from this material significantly increase the service life compared to traditional bearing alloys and bearing steels. Furthermore, because silicon nitride ceramics have an extremely low thermal expansion coefficient, the bearing assembly gap can be reduced, making it suitable for ultra-precision bearings and high-temperature bearings. Its strong corrosion resistance also makes it suitable for special bearings working in highly corrosive environments.

• Valves and Pipelines

Traditional valves and pipelines are made from materials like stainless steel, nylon, plastics, and cast iron. However, due to insufficient temperature resistance, corrosion resistance, and wear resistance, they often experience issues such as leakage, which severely affects the efficiency of fluid transport. Using silicon nitride ceramics can greatly extend the service life, save maintenance time, and reduce production costs.

• Ceramic Cutting Tools

Ceramic cutting tool materials have incomparable hardness, high chemical stability, and low friction coefficients, offering vast application prospects in the cutting field. These tools enable high-speed cutting, reduce tool replacement frequency, and minimize dimensional errors caused by tool wear, offering significant advantages in CNC machines and machining centers.

Silicon nitride ceramics, being covalent compounds, rely on covalent bonds between atoms, which gives them high hardness and wear resistance. Silicon nitride’s hardness is second only to diamond and cubic boron nitride, and its low friction coefficient and self-lubricating properties make it ideal for fine grinding. Compared to traditional grinding media, silicon nitride ceramic grinding balls have higher hardness and better wear resistance, making them superior in industries like ultrafine powder and food processing.

Porous silicon nitride ceramics have a large specific surface area, high strength, excellent thermal shock resistance, and good chemical stability, making them suitable as catalyst supports. For example, the use of silicon nitride as a support material in automotive exhaust purification catalysts has become popular. Honeycomb structures are commonly made from materials like cordierite, alumina, and silicon nitride. Currently, the development of high-efficiency, environmentally friendly porous ceramic supports is a key focus of national research and development efforts.

Porous silicon nitride materials have high mechanical strength, allowing them to withstand large pressure differentials. They are also highly resistant to high temperatures, with excellent thermal stability, making them suitable for high-temperature gas filtration, with operating temperatures exceeding 1000°C. Additionally, they have excellent thermal conductivity, a small coefficient of thermal expansion, and high filtration efficiency, making them ideal for filtering toxic gases and adsorbing hazardous substances in industrial applications, thus playing a significant role in reducing atmospheric pollution.

Aerospace communication materials (antenna radomes) protect spacecraft from harsh environmental conditions and ensure the proper functioning of systems such as communications, telemetry, detonators, and guidance. Porous silicon nitride ceramics have a low dielectric constant, low dielectric loss, low density, excellent insulation, and good strength. These characteristics, along with their long service life, make silicon nitride a promising material for aerospace radomes, with lower radar wave absorption compared to other ceramic materials.

The development of ceramic engines is a major objective of high-temperature structural ceramic research and one of its most important applications. Engine components typically operate under extreme conditions of high temperatures and high speeds, which ordinary metals or polymers cannot withstand. Even high-temperature alloys can only operate at temperatures up to 1050°C and have relatively low efficiency. Silicon nitride ceramic engines, however, can operate at temperatures ranging from 1200°C to 1650°C, improving engine performance, increasing combustion efficiency, and conserving energy.

Silicon nitride ceramics are known for their excellent wear resistance, corrosion resistance, and high-temperature oxidation resistance, making them suitable for various components such as mechanical seals, valves, molten metal containers, rolls, high-speed bearings, metal stretching dies, extrusion dies, and more. They are widely applied in industries such as machinery, steel, metallurgy, chemical engineering, and aerospace. The market share in these sectors abroad is approximately ten times larger than in the domestic market, which is expected to reach 10 billion yuan.

Silicon nitride ceramics are primarily studied, developed, and applied as high-temperature structural and engineering materials. The annual domestic demand for nitride special ceramics exceeds 270,000 tons, while domestic production is only around 100,000 tons. As a nitrogen enhancer in structural steels, silicon nitride can improve the comprehensive performance of steel, with domestic annual market demand exceeding 60,000 tons. In steel production, the demand for refractory materials exceeds 100,000 tons. For deep processing raw materials such as silicon nitride bearings, engine housings, and cutting tools, the annual demand is around 60,000 tons.

Overall, the domestic market demand is substantial. Typically, for every 10,000 tons of steel produced, 1 ton of hard alloys is consumed. The growth of hard alloys alone is insufficient, thus the demand for nitride special ceramics will inevitably rise. Currently, the domestic market can only produce a small number of simple-shaped hot-pressed ceramic tools, and cannot meet the demand for tools with central holes and cutting grooves, failing to satisfy the market’s needs.