There are many types of ceramics used in multiple applications. One of these ceramics is silicon carbide (SiC), which is commonly listed as a technical ceramic. All ceramics fall under the umbrella of “inorganic solids,” and technical ceramics have the highest performance when it comes to thermal, electrical, and mechanical properties. The particular properties of SiC are similar to that of a diamond—it is hard, light, and strong. Read on to learn more about silicon carbide, what it is, and how it is made and machined.

What Is Silicon Carbide?

Silicon carbide was first used in the late 1800s, as an abrasive material. Today, precision machining of SiC is used in many industries, including semiconductor manufacturing, the making of electric vehicles, space applications, and solar energy fields. This is because it has so many uses due to its physical properties. SiC is also referred to as carborundum. It is a combination of both carbide and silicon in crystalline form. There are over 250 types of SiC that can be found. It is difficult to find SiC in nature; however, it is found in a mineral called moissanite, which was discovered in the 1800s (when SiC first was used as an abrasive.). The types of SiC all have different stacking arrangements for the atoms of carbon and silicon within the compound. One of the most simple structures is the aforementioned diamond structure, called b-SiC. Other more complex structures (e.g., rhombic, hexagonal) are referred to as -SiC. SiC has many applications as a polished precision ceramic because of its abrasion resistance and rigidity to weight ratio. It also has excellent thermal properties and is resistant to acids. As a result, it is used in various applications, such as cyclone components (a device that uses fluid pressure to produce rotational motion), spray nozzles, safeguarding nuclear weapons, lightweight space exploration components, high-heat duty kiln shelves, mechanical seals, paper-making components, heating elements, and turbochargers for engines.

What Are the Different Types of Silicon Carbide?

For purposes of precision machining, there are several types of SiC. These include:
  1. Nitride bonded silicon carbide (NBSC)
  2. Sintered silicon carbide (SSC)
  3. Reaction bonded silicon carbide (RBSC)
There are other less common variations as well, including SiAlON bonded silicon carbide, clay bonded SiC, and chemical vapor deposited SiC called CVD SiC, which is extremely rare.

How Is SiC Manufactured?

SiC is manufactured in several ways, and the most common types are reaction bonding and direct sintering. Reaction bonded SiC provides lower hardness but higher thermal conductivity. It also has the lowest production cost. Directly sintered SiC is of a higher grade and is better suited for high-temperature applications.

What Are the Properties of Silicon Carbide?

SiC has many properties because of its lightweight, hardness, and thermal conductivity. Some of the properties of SiC include:
  • Corrosion-resistant
  • Refractive index greater than a diamond
  • Thermal shock resistance
  • High hardness
  • Low density (lightweight)
  • Chemically and thermally resistant
  • Wear-resistant
  • High Young’s modulus
  • Low thermal expansion coefficient

More technical properties of SiC include:

Property and Chemical formula Vickers Hardness HV(GPa) Flexural Strength (MPa) Fracture Toughness (MPam¹/²) Coefficient of Thermal Expansion (×10-⁶/℃ Thermal Conductivity (W/(m・K)) Thermal Shock Resistance(℃) Dielectric Strength(kv/mm) Wear Resistance(Blast Abrasion Loss) (μm) Chemical Resistance
SiC 24 500 3 2.9 150 450 25 1.6 (Blast Abrasion Loss) Very Good
You can further see the properties of SiC when it is compared with the properties of a diamond:
Image of IRD Glass's chart that discusses the properties of SiC.
IRD Glass has been the leading supplier of customized precision ceramics, glass, optics, and sapphire product fabrication for over 40 years. To learn more about silicon carbide and our capabilities, speak to a representative today for a quote.