IR Emissivity Tester

The infrared emissivity value is the ratio of the infrared energy actually emitted by the test object to its theoretical value. This value is between 0.000 and 1.000. If the emissivity can reach the theoretical full value without loss, it is called a black body. A blackbody is a perfect emitter because it theoretically emits 100% infrared energy, so it has an emissivity value of 1.000. An object that emits 60% of its theoretical infrared energy value is said to have an emissivity value of 0.600.

Infrared emissivity is applied to the analysis of ultra-thin coatings on the surface of metals, semiconductors and other materials, and the detection of non-destructive solid samples.

Sample Requirements

• The emissivity test requires that the sample should preferably be a disc, with a diameter between 2-7 cm (rectangular samples must ensure that the maximum size does not exceed 7 cm, and the minimum size is 2×2 cm), and the thickness is within 3 cm.
• Powder samples need to be compressed to obtain emissivity values. Emissivity spectrum testing can be done on powder samples (greater than 100 mg) and bulk samples.

Application

• For the characterization of new materials and biocomposites
• For measuring various properties of semiconductor materials

Instrument and Result Display

FAQ

Q1. Is the infrared emissivity of the material a constant value?

A. Most materials have variable emissivity values. The material being measured itself is the most important factor in surface emissivity, however it is not the only factor. Other factors, such as surface texture, degree of oxidation, microstructure, surface contamination, and plating, can affect the emissivity of a material. For example, the emissivity of molten steel is very different from that of solid steel; for another example, the emissivity of hot-rolled steel is different from that of cold-rolled steel. Another difficulty here is about the color of the material. Some metal laminations can be expressed in any color, but their emissivity value is fixed and not affected by color changes, but its expressive structure affects the emissivity value to a large extent. Typically materials with high gloss surfaces are less emissive than materials with low gloss surfaces.

Q2. The relationship between infrared emissivity and reflectivity.

A. In general, infrared energy manifests itself in three forms, namely emission, penetration and absorption.

Reflectivity + Transmittance + Absorptivity = 100%

If the target is opaque, its transmittance is 0. The above formula becomes: Reflectivity + Absorptivity = 100%.

If the target absorbs infrared energy (thermal energy), its temperature will rise. When an object is isothermal, it emits and absorbs the same amount of energy. Hence Absorptivity = Emissivity. The above formula becomes: Emissivity + Reflectivity = 100%.

Q3. What is the difference between emissivity value and emissivity spectrum?

A. 1. The two instruments are different. The emissivity spectrum is tested by an infrared instrument, which is an indirect method.

2. The data forms of the two are different. The emissivity value is only numerical, and the emissivity spectrum can provide a map. The abscissa is the wave number, and the ordinate is the percentage.

3. The emissivity value of different test ranges can only be tested according to the range of the instrument and cannot be changed. The emissivity spectrum can be selected for the test range.

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