Thermal diffusivity measurements on a single fiber with microscale diameter at very high temperature

摘要

The objective of this work is to measure the thermal diffusivity of single carbon and ceramic fibers at very high temperature. The difficulty of the measurement is due to the micrometric scale of the fiber (≈ 10μm) and the important range of temperature (700-2700 K). An original periodic technique is developed. Based on a 1D analytical direct models and using both magnitude and phase shift measurements, it allows accurate results from simulated experiments. A device is designed in order to maintain the fiber at uniform high temperature. A small perturbation is imposed by a laser beam and the temperature response is analysed. A complete study of the numerical identification allows an estimation of the uncertainty due to the numerical process. For a ± σ standard deviation on experimental measurements, the thermal diffusivity is estimated with a ± σ/80 uncertainty. Measurements on both low and high conductive materials validate the apparatus and the estimation method.