Temperature Measurement: Christiansen Wavelength and Blackbody Reference

Rousseau, Benoı̂t; Brun, Jean-François; Meneses, D. De Sousa; Echegut, Patrick

doi:10.1007/s10765-005-6726-4

Cited by 71 publications

(34 citation statements)

References 10 publications

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“…Precise temperature measurements in the high temperature are never easy, and this topic would be for itself the subject of a review article. One can give some ideas about an elegant way, consisting of using the specific properties of the Christiansen point [47], which is generally observed in polar dielectric materials; for this point, standing just above the highest frequency LO mode, the refraction index is equal to 1 and the extinction one is very low. The reflectivity and transmittivity are near to zero, so emissivity is equal to 1 and the material acts as a blackbody for this wavenumber.…”

Section: High-temperature Instrumentationmentioning

confidence: 99%

Optical Spectroscopy Methods and High‐Pressure–High‐Temperature Studies

Polian

Simon

Pagès³

2010

Thermodynamic Properties of Solids

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This chapter aims to show how optical spectroscopies contribute to the study of vibrational properties under extreme conditions. Now, what do we mean by extreme conditions? We can take it in the other way and mention that ambient conditions have nothing more special as to permit life on earth -that is already not bad! From the point of view of physics, no particular property occurs at ambient conditions. On the contrary, most of the matter in the universe is under extreme pressure (P) and temperature (T), as it is in planets, stars, and more exotic objects. Studies at high pressure and high temperature are hence only the study of matter in its normal conditions. The reason why geoscientists are much interested in such studies is self-explanatory, but other fields are widely studied. The application of high pressure and high temperature enables to explore the repulsive part of the potential energy (fundamental physics), to provoke phase transformations thereby leading to new structures eventually metastable at ambient conditions (materials sciences), to orient chemical reactions in requested directions (chemistry), and even to crystallize proteins, that otherwise would not happen by using other techniques (biology). Another interest to work under variable conditions is that, obviously, more insight is given into the considered phenomenon, in that the pressure and/or temperature derivatives of the phenomenon become available, thus offering a more complete picture to achieve optimum understanding and/or modeling.There are mainly five experimental methods to probe the vibrational properties of matter: optical spectroscopies (of main interest here), ultrasonics (US), inelastic neutron scattering (INS, cf. Chapter 3), more recently inelastic X-ray scattering (IXS, cf. Chapter 4) -that was made possible due to the introduction of third generation synchrotron radiation facilities -and picosecond (PS) acoustics.INS and IXS are used to determine the dispersion of vibration modes, that is, acoustical as well as optical ones, over the whole Brillouin zone (BZ). The most stringent limitations are the needed sources (national-size ones, i.e., a nuclear reactor for INS and a monochromatized X-ray beam as delivered by a synchrotron for IXS), and a limitation to small momentum transfer (q < 0.1q BZB , where q is the magnitude of the wavevector and BZB is the BZ boundary). An additional limitation for INS is

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Section: High-temperature Instrumentationmentioning

confidence: 99%

Optical Spectroscopy Methods and High‐Pressure–High‐Temperature Studies

Polian

Simon

Pagès³

2010

Thermodynamic Properties of Solids

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“…Figure 3 shows the value of the experimental spectral emissivity (grey solid curves) acquired at T=900 K, thanks to an experimental set-up used in Ref. [11,12].…”

Section: Resultsmentioning

confidence: 99%

Modelling of the radiative properties of an opaque porous ceramic layer

et al. 2010

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Solid Oxide Fuel Cells (SOFCs) operate at temperatures above 1,100 K where radiation effects can be significant. Therefore, an accurate thermal model of an SOFC requires the inclusion of the contribution of thermal radiation. This implies that the thermal radiative properties of the oxide ceramics used in the design of SOFCs must be known. However, little information can be found in the literature concerning their operating temperatures. On the other hand, several types of ceramics with different chemical compositions and microstructures for designing efficient cells are now being tested. This is a situation where the use of a numerical tool making possible the prediction of the thermal radiative properties of SOFC materials, whatever their chemical composition and microstructure are, may be a decisive help. Using this method, first attempts to predict the radiative properties of a lanthanum nickelate porous layer deposited onto an yttria stabilized zirconium substrate can be reported.

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“…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.…”

Section: Surface-temperature Optical Measurementsmentioning

confidence: 99%

“…The exact location of this wavelength depends on the material but not on the temperature. It is linked to absorption mechanisms (lattice vibrations) occurring in the mid-infrared range [19]. The surface temperature of the ceramic sample is deduced from the radiative heat flux measured by pyrometry using Planck's function as follows:…”

Section: Surface-temperature Optical Measurementsmentioning

confidence: 99%

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

et al. 2010

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This study is a contribution to characterizations of non-isothermal ceramic samples, for mean temperatures higher than 1000 • C. The objective is to determine the infrared radiative emission, of materials often used as thermal barrier coatings, under realistic thermal boundary conditions. The problem is treated by both experimental and numerical approaches that reveal additional ways of investigation. Results from sintered zirconia and plasma-sprayed alumina are presented. The experimental bench, designed and built to perform emission measurements on semi-transparent ceramics at high temperature, is described. The numerical code used to solve coupled conduction-radiation heat transfers in semi-transparent media is introduced. Special attention is paid to calculation of radiative properties of plasma-sprayed samples characterized by their complex internal microstructure. Experimental and theoretical emission factors obtained from these kinds of ceramics samples are compared and analyzed. The influence of the inside temperature gradient on emission is discussed.

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Temperature Measurement: Christiansen Wavelength and Blackbody Reference

Cited by 71 publications

References 10 publications

Optical Spectroscopy Methods and High‐Pressure–High‐Temperature Studies

Optical Spectroscopy Methods and High‐Pressure–High‐Temperature Studies

Modelling of the radiative properties of an opaque porous ceramic layer

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

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