Zirconium oxide (ZrO₂) is widely used as the thermal barrier coating in turbines and engines. Accurate emissivity measurement of ZrO₂ coating at high temperatures, especially above 1000 °C, plays a vital role in thermal modelling and radiation thermometry. However, it is an extremely challenging enterprise, and very few high temperature emissivity results with rigorously estimated uncertainties have been published to date. The key issue for accurately measuring the high temperature emissivity is maintaining a hot surface without reflection from the hot environment, and avoiding passive or active oxidation of material, which will modify the emissivity. In this paper, a novel modified integrated blackbody method is reported to measure the high temperature normal spectral emissivity of ZrO₂ coating in the temperature range 1000 °C to 1200 °C and spectral range 8 μm to 14 μm. The results and the associated uncertainty of the measurement were estimated and a relative standard uncertainty better than 7% (k = 2) is achieved.

The tungsten–carbon (WC) peritectic, with a liquidus temperature near to 3020 K, shows promise as a high-temperature reference fixed point. It appears that the WC phase is a discrete phase with full stoichiometry of the components W and C, in which impurities cannot be dissolved. In this paper we describe the use of Thermo-Calc software to derive the liquidus and solidus temperatures versus the impurity concentration for the impurities V and Si. It is found that the liquidus is univariant, whereas the solidus is invariant. Additionally, the transition curves between the solidus and the liquidus are modeled. The liquid fraction at the liquidus point is found to be less than 1; in contrast, it is unity for metal–carbon eutectics. Measurements are presented for a series of melting and freezing curves for two WC fixed-point cells. The Gibbs phase rule requires segregation of a fourth compound phase, involving the impurity in question, at the solidus point. The observations confirm that during supercooling, impurities are trapped in compound phases consisting of the impurity together with W and/or C, encapsulating the impurity, and resulting in a flat freezing plateau characteristic of the pure system. Finally, an expression for the melting temperature, as a function of the liquid fraction, is derived, spanning the temperature range from an initial melting temperature to the liquidus temperature. Within this range just free impurities are involved.

The bidirectional reflectance distribution function (BRDF) can effectively characterize the reflectance properties of a target, which can be used to correct infrared remote sensing data and improve the accuracy of remote sensing measurements. When the surface temperature changes, the reflectance characteristics of the target usually change, and it is necessary to carry out BRDF measurements under variable temperature conditions. In this paper, a variable-temperature infrared BRDF measurement system based on a robotic arm is developed to realize high-resolution wide-temperature region measurement of BRDF. To improve the measurement accuracy, the shaping optical path was used to expand the laser beam, combined with the laser level to accurately adjust the three-dimensional coordinates of the robotic arm, and the dichotomy method is used to calibrate the detector nonlinearly. A portable heater suitable for the mechanical arm corner mechanism is developed, and fast and high-precision temperature control is realized by proportional integral derivative (PID) control. The specular and diffuse BRDF distributions were measured at room temperature to verify the effectiveness of the system. The BRDF distribution of SUS314 stainless steel samples with different roughness is measured during two temperature increases from 20 °C to 1000 °C, and the changing rule of BRDF under variable temperature environment is summarized, which provides technical support for evaluating the optical properties of high-temperature materials and improving the measurement accuracy of remote sensing data.

Extensive studies of platinum–carbon eutectic alloy based high temperature fixed point cells have shown that this alloy has extremely good metrological potential as a temperature reference. However, it's possible adoption as an accepted reference standard means that its eutectic temperature value will soon be agreed with an uncertainty less than most radiation thermometry scales at that temperature. Thus it will lack credibility if used as a future scale comparison artefact. To avoid this, the fixed-point cell can be deliberately doped with an impurity to change its transition temperature by an amount sufficient to test the accuracy of the scales of the institutes, involved in the comparison. In this study dopants of palladium and iridium were added to platinum–carbon to produce ternary alloy and quaternary alloy fixed-point cells. The stability of these artefacts was demonstrated and the fixed-point cells were used to compare the ITS-90 scales of NIM and NPL. It was found that the fixed point temperatures could be changed by an appreciable amount while retaining the stability and repeatability required for comparison artefacts.