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Advantages of SiC Thermal Shock Resistance

Key Takeaways

  • Silicon Carbide (SiC), also known as carborundum, is a compound of carbon and silicon that possesses useful mechanical and thermal properties. 

  • The ability of a material to withstand temperature changes is called thermal shock resistance. Rapid temperature changes induce thermal stresses in materials and can produce microcracks that permanently damage the material. 

  • The thermal conductivity of SiC is in the range of 120-270 W/mK and thermal expansion is 4.0x10-6/°C,  which is less than most other semiconductor materials. 

SiC

Silicon Carbide (SiC),  also known as Carborundum

If you are searching for technical grade ceramics for turbine components, Silicon Carbide (SiC) might fit your needs. Also known as carborundum, SiC is an inorganic semiconductor compound of carbon and silicon with useful mechanical and thermal properties.  

The SiC lattice structure consists of bonds between tetrahedron carbon and silicon atoms. Due to these bonds, SiC possesses substantial hardness and mechanical strength, along with low density, high elastic modulus, inertness, low thermal expansion, high thermal conductivity, and high thermal shock resistance. 

SiC thermal shock resistance is a derived property—the high thermal conductivity, low thermal expansion, and high strength are the characteristics that lead to exceptional shock resistance. 

SiC Thermal Shock Resistance

Rapid temperature changes induce thermal stresses in a material and can produce microcracks that permanently damage it. The ability of a material to withstand temperature changes is called thermal shock resistance. When compared to metals and plastics, ceramics are popular for their thermal properties, especially their thermal shock resistance. Most isotropic ceramics exhibit high resistance to thermal shocks with a low coefficient of thermal expansion. 

When SiC ceramics are subjected to temperature fluctuations, they are exposed to extreme temperature gradients, meaning the temperature varies at different parts of the material. Due to this temperature gradient, the SiC material undergoes different rates of expansion and contraction in different sections. The differential deformations in the SiC induce thermal stress. When thermal stress exceeds the fracture strength of the SiC, the component or structure degrades or fails.

Thermal shock resistance is a characteristic feature of SiC. SiC material can withstand thermal shock due to the high thermal conductivity and low thermal expansion of SiC. The thermal conductivity of SiC is in the range of 120-270 W/mK and thermal expansion is 4.0x10-6/°C, which is less than most semiconductor materials. The combination of thermal conductivity and expansion improves thermal shock resistance and, therefore, the durability of SiC. Because of the high thermal shock resistance of SiC, it is used for manufacturing semiconductor electronics, rocket nozzles, heat exchangers, combustion engine valves, and electric vehicle environments. 

Properties of SiC

The table below shows some of the properties of SiC:

Property

Value

Density

3.21 g/cm3

Molecular weight

40.11 g/mol

Melting point

2,730 °C

Odor

None

Appearance

Black grey, green powder, grey solid

Solubility

Insoluble in water, alcohol, and acid

SiC properties

High-Temperature Applications of SiC

Due to useful characteristics such as high force-to-weight radius, hardness, non-corrosive nature, and good thermal properties, SiC is a widely used ceramic. The maintenance of elastic resistance at temperatures up to 1650℃ is also one of the factors that contributes to the use of SiC in high-temperature applications.

The thermal shock resistance of SiC is a very important parameter to be considered for SiC applications, as it affects material fractures. SiC thermal shock resistance is lower than silicon nitride and higher than zirconia ceramic. For rapid fluctuations in temperature, silicon nitride is preferred, but for moderate temperature variations, SiC offers the best performance, as it prevents internal cracking. 

Power Electronics Applications of SiC

As two viable alternatives to Si material, SiC and GaN are revolutionizing the power electronics industry. In particular, SiC material is in high demand for the manufacturing of high voltage power devices, given its high critical avalanche breakdown field, high thermal conductivity, and wide bandgap. Since SiC can withstand high voltages, fewer devices need to be connected in series to satisfy voltage requirements, reducing costs and system complexities. Additionally, the low-on state resistance and operational reliability of SiC at high temperatures makes it more desirable than silicon for fabricating power devices. SiC devices also provide low switching and heating losses, lowering the cost of cooling mechanisms.

SiC devices are frequently used in motors, electric drives, and inverters due to their unique characteristics. In the automotive industry, the majority of power electronics in electric vehicles use SiC components for their vibration resistance and high-temperature operation capabilities. Additionally, SiC-based Schottky diodes are widely used in switch-mode power supplies and in power factor correction circuits. 

In terms of temperature, power, speed, and losses, overall, SiC-based power devices are some of the best replacements for Si semiconductor devices. If you are trying to build structural components that will be subjected to high temperatures, high currents, or high power applications, consider SiC the perfect building material. 

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