The laser-pulse method is a well-established nonsteady-state measurement technique for measuring the thermal diffusivity, a, of solid homogeneous isotropic opaque materials. BNM-LNE has developed its own bench based on the principle of this method in which the thermal diffusivity is identified according to the "partial time moments method." Uncertainties of thermal diffusivity by means of this method have been calculated according to the ISO/BIPM "Guide to the Expression of Uncertainty in Measurement." Results are presented for several cases (Armco iron, Pyroceram 9606) in the temperature range from 20 to 800 • C. The relative expanded (k = 2) uncertainty of the thermal diffusivity determination is estimated to be from ±3 to ±5%, depending on the material and the temperature.

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A new experimental device for normal spectral emissivity measurements of coatings in the infrared spectral range from 1.38 μm to 26 μm and in the temperature range from 550 K to 1250 K is presented. A Fourier transform infrared spectrometer (FTIR) is used for the detection of sample and blackbody spectral radiation. Sample heating is achieved by a fiber laser with a scanning head. Surface temperature is measured by two methods. The first method uses an infrared camera and a reference coating with known effective emissivity, the second method is based on the combination of Christiansen wavelength with contact and noncontact surface temperature measurement. Application of the method is shown on the example of a high-temperature high-emissivity coating. Experimental results obtained with this apparatus are compared with the results performed by a direct method of Laboratoire National d’Essais (LNE) in France. The differences in the spectra are analyzed.

An infrared reflectometer has been designed by BNM-LNE (Bureau National de Métrologie-Laboratoire National d'Essais) to measure the spectral directional hemispherical reflectance of solid materials at ambient temperature. For opaque materials, the spectral directional emissivity can be calculated from the measured reflectance. The reflectance can be measured from 0.8 to 14 µm in five directions with an angle of 12 • , 24 • , 36 • , 48 • , and 60 • with respect to the normal to the surface of the sample. The optical arrangement to collect the reflected flux is based on the Coblentz arrangement (hemispherical mirror). In fact, four mirrors cut in an hemisphere are used to collect the flux reflected by the sample. This optical arrangement was chosen to limit the angle of incidence of rays on the detector (38 • instead of 90 • for the Coblentz arrangement). The final expanded uncertainty (level of confidence 95%) of the reflectance is estimated to be about ±0.03 for wavelengths between 0.8 and 10 µm and ±0.04 for wavelengths over 10 µm. The values of the spectral reflectance measured on a black paint and on a white ceramic tile are compared to those measured by the two laboratories PTB (Physikalisch Technische Bundesanstalt) and NIST (National Institute of Standards and Technology). The results validate the measurements performed at BNM-LNE.

An apparatus has been designed to measure, using a calorimetric technique, the total hemispherical emissivity of opaque solid materials from −20 to 200 • C. The originality of the technique is the use of two samples and thermal guard rings in order to ensure one-dimensional heat flow in each sample and to reduce heat-loss corrections. Two temperatures are measured in each sample at two distances from the surface, and the surface temperature of each sample is linearly extrapolated. The mean total hemispherical emissivity of the two samples is calculated using a model that considers the main surfaces radiating in the chamber. Unwanted heat losses are evaluated and corrected. The facility design, model of calculation, evaluation of corrections, and uncertainty assessment are described. The measurement technique was validated by comparison to results from a study using another technique. The expanded uncertainty (k = 2) of the total hemispherical emissivity is between ±0.005 and ±0.03.