Since the birth of silicon carbide, its high stiffness and high-temperature stability have been rooted in its “NDA”; it is used as an abrasive and refractory material in large quantities across various industries. With the breakthrough of SiC synthesis technology, it has been used in the field of high-brightness LED semiconductors since the late 20th century. Over the past decade, driven by the strong growth of emerging industries such as new energy vehicles, photovoltaic energy storage, and 5G communications, silicon carbide has experienced a surge in demand.
The following article will tell the characteristics, grade, synthesis, and uses of silicon carbide to help you gain a deeper understanding of it.
Material Characteristics
● High-temperature resistance: Even at a temperature of 1600-1650℃, the mechanical properties and shape of SiC ceramic parts can remain well.
● High thermal conductivity: It can reach 120~200 W/k.m, second only to aluminum nitride (AlN) and beryllium oxide(BeO)
● Low coefficient of thermal expansion(CTE): SiC (4.0~4.5-6/K) is one of the industrial ceramics with thermal expansivity closest to that of Si chips(2.5 ~4.2 x 10-6/K).
● Hardness / abrasive resistance: Its Mohs hardness is 9.5, just slightly lower than that of diamond (10).
● Corrosion resistance: It is one of the most chemically inert products among all advanced ceramics. In various harsh environments, it can resist aging.
● Others: Lightweight(3.1~3.2g/cm3), high elastic modulus (400~450GPa), excellent thermal shock, not wetted or eroded by most molten metals, semiconductor properties, good electrical insulation, and non-toxic.
Grades & Synthesis
Silicon carbide is a fundamental material for ceramic structural components. Its grade is mainly divided according to the sintering process and the degree of densification as follows:
1. Pressureless Sintered type(SSiC)
● Synthesis method:
Densification is achieved through solid-phase sintering at high temperature and atmospheric pressure by adding sintering aids such as boron and carbon. This is the most common and economical process.
● Performance:
High density (≥98% theoretical density), excellent strength, hardness, wear resistance, and corrosion resistance.
● Applications:
Sealing rings, bearings, nozzles, wear-resistant liners, kiln furniture (saggers, rollers), etc.
2. Reaction-bonded type (RBSiC)
● Synthesis method:
After α-SiC powder and carbon powder are mixed and molded, they react with molten silicon or silicon vapor at high temperature to generate β-SiC, which fills the pores and achieves densification.
● Performance:
High density, ideal sintering deformation, high dimensional accuracy, short preparation cycle, and low cost. But the material usually contains a small amount of free silicon, which limits its maximum operating temperature (about 1350°C) because silicon will melt.
● Applications:
Components with high-dimensional accuracy requirements, such as precision mechanical seals, heater brackets in the photovoltaic industry, rollers, etc.
3. Re-crystallized type(R-SiC)
● Synthesis method:
A pressureless sintering process that uses SiC evaporation-condensation mass transfer at high temperatures to achieve grain growth and bonding, without the addition of any sintering aids.
● Performance:
Extremely pure and free of glass, it offers excellent high-temperature resistance (capable of long-term use above 1600°C) and excellent oxidation and thermal shock resistance. However, it has a high porosity (approximately 15%-20%) and relatively low mechanical strength.
● Applications:
High-end kiln furniture (such as supports and beams), burner nozzles, heat exchanger tubes, and other applications involving high-temperature, oxygen-rich environments.
4. Hot Isostatic pressing type(HIPSiC)
● Synthesis method:
Sintering is performed at high temperatures using extremely high pressure (hot pressing) or isotropic high-pressure gas (hot isostatic pressing). Sintering aids are typically added.
● Performance:
Achieving nearly 100% theoretical density, with fine and uniform grains, results in the highest mechanical properties (strength and toughness) of all grades.
● Applications:
Used in applications with extremely demanding performance requirements, such as armor plating, critical aerospace components, and high-end cutting tools. Due to its high cost, its application range is limited.
Silicon Carbide Ceramic Uses
Because different grades of silicon carbide offer varying combinations of properties, they can be precisely tailored to specific industries and transformed into your business solutions. The following table lists corresponding applications based on performance, which we hope will be helpful.
|
Core Properties |
Target industries |
Real Parts in Uses |
|
Excellent wear resistance |
Mining, energy, chemicals |
● Nozzle: Sand blasting, water jet cutting
|
|
Automobile and machinery manufacturing |
● Seals: Shaft seals for severe environments.
● Wear plates |
|
|
Excellent mechanical strength and rigidity |
Pumps, valves, and fluid machinery |
● Mechanical seals: Used in chemical pumps and multi-stage pumps.
● Bearing balls & rollers: Used in high-speed spindles and precision machine tools.
● Pump sleeves & thrust collars: Core components of magnetic drive pumps. |
|
Defense and aerospace |
Lightweight armor material: using its high hardness and high strength to resist impact |
|
|
Excellent high-temperature resistance and thermal management capabilities |
Metallurgy, glass, ceramics |
● Kiln accessories: Kiln furniture (supports, crossbeams, push plates), furnace.
● Burner nozzles: Highly efficient and energy-saving burner components. |
|
semiconductor manufacturing |
● Wafer processing components: grinding discs, fixtures, annealing paddles, and epitaxial trays. They ensure the flatness and low contamination of silicon wafers during high-temperature processes. |
|
|
Excellent chemical inertness |
Chemical industry， Oil and gas |
● Seal rings & mechanical seals: Used in pumps handling strong acids (sulfuric acid, hydrochloric acid) and strong alkalis.
● Valve balls & valve seats: Control the flow of corrosive media.
● Heat exchangers: Used for heat transfer in highly corrosive environments. |
|
High thermal conductivity and electrical properties
|
Power Electronics and Semiconductors |
● Electronic device substrates: Heat sinks for high-power LEDs and IGBT modules.
● Wafer manufacturing equipment: Electrostatic chucks and heaters. |
|
Industrial Sensing and Control |
● Heater & Sensor Assemblies: High-temperature heat treatment equipment. |
Conclusions
In short, silicon carbide is a versatile advanced ceramic material, especially in terms of wear resistance, thermal performance, and chemical inertness, which far surpasses other engineered ceramics. It has a variety of synthesis methods, resulting in different grades of products with unique properties. Silicon carbide parts enable numerous challenging application scenarios, allowing them to break through higher limits and provide better total cost solutions.
JingHui Industry is a professional supplier of high-quality silicon nitride components made from various grade materials. Please send us an inquiry if you are interested.