Report on the CCT Supplementary Comparison S1 of Infrared Spectral Normal Emittance/Emissivity

open9openHanssen, L; Wilthan, B; Filtz, J -R; Hameury, J; Girard, F; Battuello, M; Ishii, J; Hollandt, J; Monte, CHanssen, L; Wilthan, B; Filtz, J. R; Hameury, J; Girard, Ferruccio; Battuello, Mauro; Ishii, J; Hollandt, J; Monte, C

Métrologie des matériaux pour la photonique et l’énergie

Materials Science is an extremely wide and complex field in physics and chemistry. Many academic institutes and public or private research laboratories implement research in that field. However, very few National Metrology Institutes have developed skills in that area. LNE one of these institutes has developed a research program for addressing the most important and critical needs. This paper is intended to highlight with examples the contribution of the laboratory for helping industry and society and therefore the interest to amplify the basic and applied research in thermophysical and optical properties metrology for materials

Comparative study of radiometric and calorimetric methods for total hemispherical emissivity measurements

International audienceAccurate knowledge of infrared emissivity is important in applications such as surface temperature measurements by infrared thermography or thermal balance for building walls. A comparison of total hemispherical emissivity measurement was performed by two laboratories: the Laboratoire National de Métrologie et d'Essais (LNE) and the Centre d'Études et de Recherche en Thermique, Environnement et Systèmes (CERTES). Both laboratories performed emissivity measurements on four samples, chosen to cover a large range of emissivity values and angular reflectance behaviors. The samples were polished aluminum (highly specular, low emissivity), bulk PVC (slightly specular, high emissivity), sandblasted aluminum (diffuse surface, medium emissivity), and aluminum paint (slightly specular surface, medium emissivity). Results obtained using five measurement techniques were compared. LNE used a calorimetric method for direct total hemispherical emissivity measurement [1], an absolute reflectometric measurement method [2], and a relative reflectometric measurement method. CERTES used two total hemispherical directional reflectometric measurement methods [3, 4]. For indirect techniques by reflectance measurements, the total hemispherical emissivity values were calculated from directional hemispherical reflectance measurement results using spectral integration when required and directional to hemispherical extrapolation. Results were compared, taking into account measurement uncertainties; an added uncertainty was introduced to account for heterogeneity over the surfaces of the samples and between samples. All techniques gave large relative uncertainties for a low emissive and very specular material (polished aluminum), and results were quite scattered. All the indirect techniques by reflectance measurement gave results within ±0.01 for a high emissivity material. A commercial aluminum paint appears to be a good candidate for producing samples with medium level of emissivity (about 0.4) and with good uniformity of emissivity values (within ±0.015)

High-accuracy measurements of the normal specular reflectance

International audienc

Investigation of the directional emissivity of materials using infrared thermography coupled with a periodic excitation

International audienceThis article concerns the determination of the directional emissivity of materials. Several materials (conducting materials or dielectrics) are investigated and the influence of surface roughness is also considered. The experimental method used for the determination is based on the use of a periodic excitation and the recording of the surface temperature variations of the sample using infrared thermography. Several consecutive measurements are performed for emission angles varying from 0° (for the determinat ion of normal emissivity) to 85°. The experimental device developed (SPIDER instrument) is simple compared to existing devices but the variation of directional emissivity is limited to the spectral bandwith of the camera used

Experimental Determination of the Directional Emissivity of Materials Using a Periodic Thermal Excitation Coupled with Infrared Thermography

International audienceVariation of directional emissivity upon emission angle can be deduced theoretically from the complex refractionindex. Nevertheless, theoretical relations are only valid for perfectly smooth surfaces and homogeneous materials.Directional emissivity is generally nearly constant for emission angles lower than 60 degrees from the normalincidence, but strong variations are expected for angles higher than 60 degrees either for dielectric materials or forconducting ones. Many experimental devices were developed to determine directional emissivity of materials.Generally, these devices are quite complex and fail in measuring directional emissivity for angles greater than 80degrees. Thus, it is still difficult to point out deviations between theoretical and experimental values for highemission angles. Current work concerns the development of a device (SPIDER Instrument) allowing to determinedirectional emissivity of dielectric or conducting materials. The rear face of the sample is heated periodically.Temperature variations are recorded using a thermocouple. Sample surface temperature variations are recordedusing an infrared camera. By comparing at several frequencies and emission angles, the temperature amplitudesrecorded, it is possible to determine relative variations of directional emissivity. If directional emissivity is known ata given emission angle, then directional emissivity can be calculated at any emission angl

Experimental Determination of the Directional Emissivity of Materials Using a Periodic Thermal Excitation Coupled with Infrared Thermography

International audienceVariation of directional emissivity upon emission angle can be deduced theoretically from the complex refractionindex. Nevertheless, theoretical relations are only valid for perfectly smooth surfaces and homogeneous materials.Directional emissivity is generally nearly constant for emission angles lower than 60 degrees from the normalincidence, but strong variations are expected for angles higher than 60 degrees either for dielectric materials or forconducting ones. Many experimental devices were developed to determine directional emissivity of materials.Generally, these devices are quite complex and fail in measuring directional emissivity for angles greater than 80degrees. Thus, it is still difficult to point out deviations between theoretical and experimental values for highemission angles. Current work concerns the development of a device (SPIDER Instrument) allowing to determinedirectional emissivity of dielectric or conducting materials. The rear face of the sample is heated periodically.Temperature variations are recorded using a thermocouple. Sample surface temperature variations are recordedusing an infrared camera. By comparing at several frequencies and emission angles, the temperature amplitudesrecorded, it is possible to determine relative variations of directional emissivity. If directional emissivity is known ata given emission angle, then directional emissivity can be calculated at any emission angl

Uncertainty Assessment for Very High Temperature Thermal Diffusivity Measurements on Molybdenum, Tungsten and Isotropic Graphite

International audienceAbstract The French National Metrology Institute LNE has improved its homemade laser flash apparatus in order to perform accurate and reliable measurements of thermal diffusivity of homogeneous solid materials at very high temperature. The inductive furnace and the associated infrared (IR) detection systems have been modified and a specific procedure for the in situ calibration of the used radiation thermometers has been developed. This new configuration of the LNE’s diffusivimeter has been then applied for measuring the thermal diffusivity of molybdenum up to 2200 °C, tungsten up to 2400 °C and isotropic graphite up to 3000 °C. Uncertainties associated with these high temperature thermal diffusivity measurements have been assessed for the first time according to the principles of the “Guide to the Expression of Uncertainty in Measurement” (GUM). Detailed uncertainty budgets are here presented in the case of the isotropic graphite for measurements performed at 1000 °C, 2000 °C and 3000 °C. The relative expanded uncertainty (coverage factor k = 2) of the thermal diffusivity measurement is estimated to be between 3 % and 5 % in the whole temperature range for the three investigated refractory materials

Comparative distribution of the mRNAs encoding urotensin I and urotensin II in zebrafish

International audienceThe neural neurosecretory system of fishes produces two biologically active neuropeptides, i.e. the corticotropin-releasing hormone paralog urotensin I (UI) and the somatostatin-related peptide urotensin II (UII). In zebrafish, we have recently characterized two UII variants termed UIIα and UIIβ. In the present study, we have investigated the distribution of UI, UIIα and UIIβ mRNAs in different organs by quantitative RT-PCR analysis and the cellular localization of the three mRNAs in the spinal cord by in situ hybridization (ISH) histochemistry. The data show that the UI gene is mainly expressed in the caudal portion of the spinal cord and, to a lesser extent, in the brain, while the UIIα and the UIIβ genes are exclusively expressed throughout the spinal cord. Single-ISH labeling revealed that UI, UIIα and UIIβ mRNAs occur in large cells, called Dahlgren cells, located in the ventral part of the caudal spinal cord. Double-ISH staining showed that UI, UIIα and UIIβ mRNAs occur mainly in distinct cells, even though a few cells were found to co-express the UI and UII genes. The differential expression of UI, UIIα and UIIβ genes may contribute to the adaptation of Dahlgren cell activity during development and/or in various physiological conditions

Inter-laboratory comparison on thermal conductivity measurements by the guarded hot plate method between LNE and Institute VINCA

Institute VINCA, respectively French National Metrology Institute and Serbian Designated Institute for thermal properties metrology, on thermal conductivity measurements by the guarded hot plate method. The main objective was to validate the measurement capabilities of VINCA in terms of thermal conductivity in the temperature range from 10 degrees C to 50 degrees C by using the facility improved in the frame of the European project Eura-Thermal. The measurements were carried out on expanded polystyrene boards using guarded hot plate apparatuses (two-specimen GHP apparatuses) in accordance with the international standard ISO 8302. The measurement programme was defined taking into account the major characteristics of the guarded hot plate apparatuses used, such as specimen dimensions and temperature and thermal conductivity ranges. Specimens were machined by LNE from a same batch for both participants. Prior to the measurements, the homogeneity of the set of specimens, as well as the influence of a variation of density of the expanded polystyrene on the thermal conductivity measurements were studied by VINCA. The obtained results showed good agreement between the two laboratories, with relative deviations within the uncertainties of measurement. Also, the results validated the level of uncertainty assessed by VINCA for its thermal conductivity measurements to around 2.5 % (with a coverage factor of 2) between 10 degrees C and 50 degrees C