Method for emissivity measurement of semitransparent coatings at ambient temperature

Abstract

Coatings deposited on a material surface are effective way of changing its surface properties. For increasing or decreasing radiation heat transfer, coatings with high or low emissivity are used. Measurement of spectral emissivity is a fundamental step to effective use of coatings for this application. Up to now the measurement methods are focused on bulk samples and mainly opaque ones. Here we present a method enabling measurement of emissivity of semitransparent coating itself, although it is deposited on a substrate. The method is based on measurement of transmittance and reflectance using an integration sphere system and Fourier transform infrared (FTIR) spectrometer for samples with two different coating thicknesses deposited on transparent substrates. Measured transmittance of the coating indicates spectral regions of potential emissivity differences using different substrates. From all the measured values, spectral emissivity can be characterized for different coating thicknesses. The spectral range of the method is from 2 μm to 20 μm. The measurement is done at ambient temperature enabling measurement of samples sensitive to heating like biomedical or nanocoatings. The method was validated on known bulk samples and an example of semitransparent coating measurement is shown on high-temperature high-emissivity coating.

Modeling the Melting Threshold of Mo Films Upon Ultrashort Laser Irradiation

“…Radiation losses due to the emissivity of the front surface of the thin film [Honnerová 2017] was neglected. The energy loss by thermal radiation during the simulation time (up to melting) is negligibly small as compared to the energy absorbed by the film and dissipated in the film-substrate system.…”

Symbolic Monte Carlo method applied to the identification of radiative properties of a heterogeneous material

“…The coverage factor k was taken equal to 2 in order to have an extended absolute uncertainty with a confidence interval of 95%. A quasi-similar approach was proposed by [14] for the evaluation of emissivity from transmittance and reflectance measurements at ambient temperature. In the present work, absolute experimental uncertainties were estimated at 0.01.…”

Measurement of core temperature through semi-transparent polyamide 6 using scanner-integrated pyrometer in laser welding

“…Spectrometers with integration spheres are used in this work. The equipment is described in Honnerova et al [24]. Beforehand the samples are dried for four hours at a temperature of 80°C in order to meet the same conditions as for welding.…”