Overview of materials and coatings emission coefficient control methods

Abstract

The emissivity of a coating and materials determines the intensity of radiation heat exchange on the surface of the object under study. Therefore experimental determination is important to ensure the necessary thermal protection characteristics of structures. The article considers methods of emissivity control, which are currently regulated by the main standards ASTM E408-13, ISO 9050:2003, C835-06, C1371-15. The methods of experimental determination of the emissivity can be divided into two large groups: optical and thermal. Spectrometric is the most widespread optical method. The technique of spectrometric research in determining the curve of specular reflection, measured in a wide range of wavelengths at an angle of incidence of the radiation close to normal. Based on the obtained results, the average value of the normal and hemispherical emissivity of the surface is calculated. Among the thermal methods of experimental determination of the emissivity the following have become widespread: radiation, calorimetric, regular mode method, and the method of continuous heating at a constant rate. The stationary systems with a wide range of research temperatures and portable express devices for control at temperatures close to room temperature are used to measure the emissivity. In stationary systems for measuring the emissivity, which apply thermal methods, heat fluxes between the object under investigation and some emitter, as well as the temperature of the structure elements, are usually determined. But these methods cannot be used in the control of products. Therefore, it is promising to develop a method for measuring the emissivity which will non-destructive and in same do not require additional standard samples for comparations. Keywords: express control, emissivity, emissometers, spectrophotometers, reflectometers