Specialty Ceramics

Specialty ceramics include nitrides, borides, carbon or graphite, silicides and other specialized non-metallic compounds. Specialty ceramics are sometimes called fine ceramics, advanced ceramics, engineered ceramics, technical ceramics, and high performance ceramics. Specifications for a specialty ceramic include color, density, porosity, thermal conductivity, coefficient of expansion, dielectric strength, dielectric constant, dielectric loss tangent, flexual strength, hardness, volume resistancy, maximum use temperature, thermal expansivity, specific heat, and compressive strength. Specialty ceramics are valued for their extreme hardness, high resistance to wear, heat, cold, and corrosion. Ceramic supply services may provide assistance with concepts, manufacturing costs, manufacturing techniques and material considerations.

There are many types of specialty ceramics. With high thermal conductivity and excellent electrical insulation properties, aluminum nitride (AlN) is used in substrates for electronic packages, heat sinks, and turbine blades. 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. Like a graphite lubricant, 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). Aluminum oxide (alumina or Al2O3) ceramics have a high temperature service limit, relatively low cost, and are easily machined. 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.

ASTM International (formerly called the American Society for Testing and Materials (ASTM), Advanced Ceramics Committee (C28) develops standards for specialty ceramics. The International Organization for Standardization (ISO) Technical Committee 206 (fine ceramics) maintains several standards on specialty ceramics, including ISO 15165, which describes a classification system for fine ceramics.

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