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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. [ABSTRACT FROM AUTHOR]

Zirconium oxide (ZrO 2 ) is widely used as the thermal barrier coating in turbines and engines. Accurate emissivity measurement of ZrO 2 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 ZrO 2 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 stacking order plays a critical role in the electronic and optical properties of two-dimensional materials. It is however of great challenge to achieve large-size and homogeneous bilayer crystals with precisely controlled stacking orders. Here, we demonstrate an optimized chemical vapor deposition strategy to grow MoSe 2 bilayers with controlled AA or AB stacking sequences. Reverse gas flow effectively suppresses the random nucleation centers, leading to uniform growth of the second layer of MoSe 2 on the first monolayer. A customized temperature profile selectively activates the growth of the MoSe 2 bilayer with different stacking orders: the AA stacking MoSe 2 bilayer tends to form at 810 °C, and the AB stacking MoSe 2 bilayer prefers to grow at a higher temperature of 860 °C. A series of characterization methods confirm that MoSe 2 bilayers with different stacking orders exhibit distinct crystal structures and physical properties. Our results demonstrate a robust and effective route for the controllable synthesis of transition metal dichalcogenide bilayers, which will benefit the development of two-dimensional materials and van der Waals heterostructures.