Thick ceramic coatings deposited by plasma spraying techniques are widely used as heat, wear and corrosion resistant coatings at high temperature. The characterization of the thermal diffusivity and the thermal conductivity of these materials is especially important for coatings used in aeronautics, automotive and power generation industries. It is therefore necessary to have a reference facility for the measurement of these thermal properties over a wide range of temperature with reliable measurement uncertainties. LNE reference diffusivimeter, which is used for several years for measuring thermal diffusivity of homogeneous materials, is based on the principle of the rear-face flash method. This method is not convenient for the study of coatings or multilayered materials. The existing LNE facility has been thus set-up in order to enable the determination of the thermal diffusivity from the temperature of the front face or the rear face of the tested specimen. It also allows to measure simultaneously the thermal diffusivity and thermal effusivity of these coatings at high temperature by front-face flash method. This method has been first validated from room temperature to 1 400 °C by comparing the obtained results of thermal diffusivity of two wellknown homogeneous materials (Armco iron and Poco graphite) with those determined by using rear-face technique. The measured thermal diffusivity values have relative deviation of less than 3.5% depending on temperature and materials, with an expanded uncertainty less than 5.5%. The front-face laser flash method has then been applied to the determination of thermal conductivity of chromium oxide coating deposited on iron alloy substrate from 23°C to 800°C, by using simultaneous measurements of thermal diffusivity and thermal effusivity. The results were compared to thermal conductivity values determined by indirect method from thermal diffusivity, specific heat and density. The thermal conductivity values measured by using both methods are in good agreement, with a relative deviation of less than 7%, and are within the range of uncertainty of measurement.

At high temperatures (from 600 °C to 962 °C), the uncertainty of calibration by comparison of industrial platinum resistance thermometers and thermocouples is limited by the instability and the reliability of the standard platinum resistance thermometer and by the lack of uniformity of the temperature in the operating volumes of furnaces equipped with comparison blocks. To improve the performances of such calibrations by comparison, we studied the possibility to connect simultaneously several pressure-controlled heat-pipes filled with different working fluids to the same pressure control system. The experimental apparatus, called “temperature amplifier”, is composed of two heat-pipes filled with Sodium and water. This paper is a progress report on this study and presents the relevant uncertainties.

The work presented in this paper is part of a European project (Euramet 732) consisting in materialising the International Temperature Scale (ITS-90) between 83,805 8 K and 1 234,93 K. The French part of the project was done around two research topics. The first topic aimed at reducing the uncertainties affecting the materialisation of specific fixed points [Triple point of argon (83,805 8 K), triple point of mercury (234,315 6 K), freezing point of aluminum (933,473 K)]. The second axis consisted in developing a generator of temperature based on the techniques of adiabatic calorimetry at the indium point (429,748 5 K). Results from these studies either regarding the control of heat exchange or regarding the modeling of the impurities influence on the phase transition, could be extrapolated at the other fixed points. The technological innovations elaborated within the framework of this work could be also adapted to higher temperature ranges.

Cone calorimeter is one of the basic test bench for fire behaviour tests on materials. It is used to measure heat release rate of materials under heat flux by thermochemical method. This method is complex and uses a large number of parameters. Test method is nowadays standardized and some of measured parameters are used for material ranking in some regulations. It is therefore essential to determine test bench uncertainty. This paper presents uncertainty calculation applied to the test method and an example of it application to a set of fire behaviour tests on a material.

Calibration of the industrial pyrometers in the temperature range between 1 000 °C and 3 000 °C requires a blackbody cavity source which temperature is measured using a reference pyrometer. The use of such blackbody cavity source is imposed by the characteristics of the pyrometers to be calibrated, because of the large field-of-view (usually of the order of 10 mm to 30 mm), which is not compatible with the dimensions of the fixed points used to calibrate reference pyrometers. The reference pyrometer and the pyrometer under the calibration can also have very different spectral characteristics. The filter’s transmission bandwidth of the reference pyrometer filter is generally of the order of 20 nm, but it can reach several hundred nanometers for the pyrometer under calibration. An unbiased comparison of the two instruments can be only obtained with a transfer blackbody cavity with emissivity equal to 1. The different spectral and spatial characteristics of the compared pyrometers require a determination of the effective emissivity of the cavity and a determination of the radial profile of surfaces intercepted by the field-of-view of pyrometers. The high temperature furnace Thermogauge HT-9500 LNE-Cnam has been characterized for use as a transfer cavity. For this, the longitudinal and radial gradients in the cavity have been measured by various methods. The effective emissivity of the cavity was calculated. An estimate of the corrections and uncertainties associated with non-unit emissivity are presented in this article.

Nowadays, there are few high level metrological devices able to measure accurately the regular reflectance in the infrared region. The Laboratoire national de métrologie et d’essais (LNE) has developed an apparatus designed for the absolute measurement of this parameter in the infrared using the goniometer technique. This method is well appropriate for the measurement of spectral regular reflectance of materials with flat, non-scattering and high reflectivity surfaces such as mirrors. The apparatus works in a wide part of the infrared region (from 1 µm to 16 µm) and can operate in the visible and near infrared spectrum too. Mirror alignments, detection system and concentricity of opto-mechanics elements were optimized to reach uncertainties going from 0,001 to 0,015 depending on the wavelengths.

The Cr-C eutectic and peritectic phase transitions have been observed at nominal temperatures of respectively 1 742 °C and 1 826 °C. Despite some advantages compared to many other temperature fixed points, as the good reproducibility of the peritectic phase transition, suitability for contact thermometry, or the low price of the material, the Cr-C has not been extensively investigated. Only a few papers have been published mainly focusing on the difficulties encountered during the construction of the cells. In this paper, the characterisation of two Cr-C fixed point cells, from their construction, to the ITS-90 temperature determinations at the eutectic and the peritectic phase transitions is summarised. The reproducibility of the melting plateaus and their sensitivity to the carbon proportion in the mixture are discussed.

The LCM (LNE-Cnam joint laboratory) has improved the metrological performance of a standard facility for accurate measurements of the enthalpy of fusion and specific heat in the temperature range [23 °C, 1000 °C]. The metrological approach was to modify a commercial Calvet calorimeter in order to lower the uncertainty of measurement and to insure the metrological traceability of the measurements to the SI units, in particular by designing a new calibration system. This new reference facility and the associated measurement method have been validated by measuring the enthalpies of fusion of pure metals (indium, tin and silver). The results obtained on the three tested pure metallic materials are in very good agreement with data obtained by other National Metrology Institutes.