Thermal - Heat Resistance | Characteristics of Fine Ceramics | FINE CERAMICS WORLD


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Heat Resistance

Conventional ceramics, including bricks and tiles, are well known for their ability to withstand high temperatures. Nonetheless, Fine Ceramics (also known as “advanced ceramics”) are more heat resistant than these materials by far. While aluminum begins to melt at approximately 660^oC (approx. 1,220^oF), alumina Fine Ceramics only begin to melt or decompose at temperatures above 2,000^oC (approx. 3,632^oF).

Applications: Engine components and foundry / smelting components.

Heat and Thermal Shock Resistance

The heat resistant properties of Fine Ceramics are measured by the temperatures at which they begin to melt, and by their levels of thermal shock resistance. Thermal shock resistance refers to a material's ability to withstand rapid changes in temperature. Silicon nitride, a particularly heat tolerant material, displays superior resistance to thermal shock, as tested by heating the material to 550^oC (1,022^oF) and then rapidly cooling it by dropping it into water. Silicon nitride is thus suitable for applications involving extreme temperature variations, and in high-temperature industries such as metal manufacturing and energy generation.

Thermal Shock Resistance (Water Immersion Test)
Image : Thermal Shock Resistance (Water Immersion Test) Silicon Nitride550°C, Silicon Carbide400°C, Zirconia300°C, Alumina200°C (Measuring method / JIS R 1648-2002)

Image : Thermal Shock Resistance (Water Immersion Test) Silicon Nitride550°C, Silicon Carbide400°C, Zirconia300°C, Alumina200°C (Measuring method / JIS R 1648-2002)

For more information, please see Excerpt of Graph Values.

Image : Testing method of thermal shock resistance Test piece 3×4×35mm, Water30ﾟC / 80ﾟC

Testing Thermal Shock Resistance

A material's thermal shock resistance is determined by the difference between the peak temperature of the Fine Ceramic which was heated, rapidly cooled, and then fractured, and that of the cooling media. Stresses are generated by temperature differences between the interior and surface of a test piece, which occur during rapid cooling. When these stresses exceed the strength of the Fine Ceramic, fracturing occurs. These temperature differences are determined by the thermal conductivity of ceramics, as well as the coefficient of heat transfer between the Fine Ceramic and the cooling media. In addition, the stresses generated are determined by multiplying Young's modulus, the coefficient of thermal expansion, and the temperature differences between the interior and surface of the Fine Ceramic.