Description

Specialty ceramics include nitrides, borides, carbon or graphite, zirconia, rare earth oxide (REO) materials, silicides and other specialized non-metallic compounds. They are sometimes called fine ceramics, advanced ceramics, engineered ceramics, technical ceramics, and high performance ceramics.

Types

The GlobalSpec SpecSearch database contains information about these types of specialty ceramics.

• Aluminum oxide (alumina or Al2O3) ceramics have a high temperature service limit, relatively low cost, and are easily machined.
• Aluminum nitride (AlN) is used in substrates for electronic packages, heat sinks, and turbine blades because of its high thermal conductivity and excellent electrical insulation properties. Alumina's main drawback is its relatively poor thermal shock resistance. In its cubic form, boron nitride (BN) is one of the hardest materials known.
• Hexagonal boron nitride is used as a high-temperature lubricant where the electrical conductivity of graphite powder might cause problems.
• Magnesium nitride (Mg3N2) can function as an unconventional superconductor.
• Silicon nitride (Si3N4) exceeds other ceramics in thermal shock resistance.
• Boride ceramics are compounds of boron, including: boron carbide (B4C), titanium diboride (TiB2), and zirconium diboride (ZrB2).
• Silicon carbide (SiC) has high corrosion resistance. Applications include mechanical seals and pump parts.
• Silicide ceramics are compounds of a metal and silicon. One example is molybdenum disilicide (MoSi2), commonly used in high temperature furnaces. With its high strength and toughness, and excellent surface smoothness, zirconia is used in knives and scissors.

Product Specifications

Specialty ceramics are valued for their extreme hardness and high resistance to wear, heat, cold, and corrosion. Product specifications include color, density, porosity, thermal conductivity, coefficient of expansion, dielectric strength, dielectric constant, dielectric loss tangent, flexural strength, hardness, volume resistance, maximum use temperature, thermal expansion, specific heat, and compressive strength.

Standards

There are two major organizations that develop and maintain standards for specialty ceramics. ASTM International, formerly the American Society for Testing and Materials (ASTM), does so through tis Advanced Ceramics Committee (C28). The International Organization for Standardization (ISO) Technical Committee 206 (fine ceramics) also maintains several standards on specialty ceramics, including ISO 15165, which describes a classification system for fine ceramics.

References

Image Credit:

materion.com