Experimental and Theoretical Determination of Spectral Heat Flux Emitted by a Ceramic Under Axial Temperature Gradient

Experimental and Theoretical Characterization of Emission from Ceramics at High Temperature: Investigation on Yttria-Stabilized Zirconia and Alumina

“…Therefore, we must consider the concept of the emission factor for STMs which is a volume property, instead of emissivity considered as a surface property for opaque materials. In a previous study, we already discussed the relevance of using this factor for temperature optical measurements [17]. The purpose is quite different here; it appears more convenient to compare the spectral emission behavior of various samples in terms of the spectral emission factor instead of the spectral intensity.…”

“…2 is composed of the radiative heating system, the optical assembly for forwarding emitted radiation from the sample toward the measurement device which is a Fourier transform spectrometer (FTIR). For more details, the reader may refer to [17,18]. Samples are small disks of 30 mm in diameter and are all 1 mm thick; they are irradiated on one face only, called the forward side.…”

“…3) in such a way that radiation measured by the FTIR between 2.7 µm and 15 µm comes only from the sample. According to spatial heat flux measurements performed with a Gardon fluxmeter [18] and presented in Fig. 3, the incident flux from the radiative heat source is homogeneous within 5 % to 1.25 MW · m −2 on a circular area of about 18 mm of diameter.…”

“…Surface temperatures are determined with a Christiansen pyrometry technique [17,19] for which the principle is as follows. The complex refractive index of a material is n ν = n ν +ik ν ; n ν and k ν depend on the wave frequency ν and on the material electrical properties.…”

“…Samples are obtained by sintering zirconia powder with the addition of a pore-forming material. Consequently, pores are spherical and their radius distribution d(r ) is perfectly known and centered on 10 µm [18]. σ ι and p i are, respectively, the scattering coefficient and the phase function for particles of each radius calculated by the Mie theory.…”