High-Temperature Thermal Diffusivity Measurements Using a Modified Ångström's Method With Transient Infrared Thermography

Abstract

This work reports a method to measure thermal diffusivity of thin disk samples at high temperatures (900 -1150K) using a modified Angstrom's method. Conventionally, samples are heated indirectly from the surroundings to reach high temperatures for such measurements, and this process is time-consuming, typically requiring hours to reach stable temperatures. In this work samples are heated directly in a custom instrument by a concentrated light source and are able to reach high steady-periodic temperatures in 10 mins, thus enabling rapid thermal diffusivity characterization. Further, existing Angstrom's methods for high temperatures use thermocouples for temperature detection that are commonly attached to samples via drilling and welding, which are destructive to samples and introduce thermal anomalies. In this work we use an infrared camera calibrated to 2000 C for non-contact, non-destructive and data-rich temperature measurements. We present an image analysis approach to process the IR data that significantly reduces random noise in temperature measurements. We extract amplitude and phase from processed temperature profiles and demonstrate that these metrics are insensitive to uncertainty in emissivity. Previous studies commonly use regression approaches for parameter estimation that are ill-posed (i.e., non-unique solutions) and lack rigorous characterization of parameter uncertainties. Here, we employ a surrogate-accelerated Bayesian framework and a 'No-U-Turn' sampler for uncertainty quantification. The reported results are validated using graphite and copper disks and exhibit excellent agreement within 5% as compared to reference values obtained by other methods.

Solar–Thermal Production of Graphitic Carbon and Hydrogen via Methane Decomposition

“…The custom-built solar simulator consists of a 10 kW e xenon short-arc lamp (Superior Quartz Products, SX100003), an ellipsoidal reflector, and a variable DC power supply with a supply current range of 100–200 A. This lamp type closely resembles the AM 1.5 solar standard spectrum, , and its controllable photonic output can reproduce natural variations of insolation (e.g., sunrise/sunset and clouds) for testing real-world scenarios . See the Supporting Information for additional details and the solar simulator’s heat flux characterization.…”

Graphitic surface layer formation on organic substrates for electronics using a concentrated solar simulator

“…A concentrated light source (i.e., high flux solar simulator) is used to locally heat a polymer sample with a significantly larger spot size compared to IR lasers, to avoid forming discontinuous graphene structures. This light source is normally used as a platform for various experiments [17] ranging from solar fuels and commodities production [18], photovoltaic device testing [19], and high-temperature material processing [20] and characterization [21]. For photovoltaic device testing, the concentrated light source is usually operated in a controllable flash mode with flashes lasting from few to a hundred milliseconds [19].…”