Emissivity of materials
All substances emit thermal radiation (at temperatures above absolute zero). Nevertheless, for any specific temperature and wavelength the total emitted thermal radiation is determined by the emissivity of the substances surface.
Emissivity of materials is defined as the ratio of the energy radiated from a substance’s surface to the energy radiated from an ideal emitter (blackbody emission/ black body radiation) under the same conditions. It is a value between 0 for an ideal reflector and 100% for an ideal emitter.
The surface emissivity can be altered by applying the appropriate coating, for example high emissivity black paint, black anodize or ultimately Acktar vacuum deposited black coatings (thin PVD films) that reach the nearly ideal infrared emitter with the value of 98.5%. The Blackest material with highest emissivity in the industry with a coating thickness of just 5 microns.
|% Emissivity of materials over wavelength range|
|Wavelength range||3-10 microns||3-30 microns|
|Emissivity Measuring Instrument||Bruker – FTIR||Devices and Services Emissometer|