With the growing interest in high-flux solar sources, a need exists for simple, accurate, and inexpensive strategies to characterize their output radiative flux. In this paper, the irradiation output from a 10 kWe xenon lamp solar simulator is characterized by an inverse mapping technique that uses a custom radiometer and infrared camera, validated by a direct characterization method (heat flux gauge). The heat flux distribution is determined in a vacuum chamber using an easily obtainable graphite target and an inverse heat transfer model. The solar simulator produces peak fluxes in the range of 1.5–4.5 MW/m2 as measured directly by a heat flux gauge, and its output can be controlled using a variable power supply. Spectral measurements indicate that minor variations in the simulator’s output with respect to its current supply occur in the spectral range of 450–800 nm. The radiometer presented in this work allows for characterizing solar irradiation under practical conditions (e.g., inside a solar reactor) and thus accounts for deviations due to additional components, such as viewport effects. Additionally, it provides an inexpensive and efficient means of monitoring any deterioration in the performance of solar sources over time without the need for complex recalibration.
Manufacturing processes are often highly energy-intensive, even when the energy is primarily used for direct heating processes. The required energy tends to derive from local utilities, which currently employ a blend of sources ranging from fossil fuels to renewable wind and solar photovoltaics, among others, when the end manufacturing need is thermal energy. Direct solar-thermal capture provides a compelling alternative that utilizes renewable energy to reduce greenhouse gas emissions from industrial processes, but one that has rarely been employed to date. In this study, a 10 kW[Formula: see text] custom-built high flux solar simulator (HFSS) that closely approximates the solar spectrum produces a heat flux distribution with an adjustable peak between 1.5 and 4.5 MW/m[Formula: see text]. The HFSS system is coupled to a cold-wall chemical vapor deposition (CVD) system that is equipped to automate graphene synthesis while providing safe operation, precise control, and real-time monitoring of process parameters. A numerical heat transfer model of a thin copper substrate is derived and validated to compute the substrate’s temperature profile prior to the synthesis process. The peak substrate temperature is correlated to the HFSS supply current and vacuum pressure, as it serves as a critical design parameter during graphene synthesis. We report the synthesis of high-quality graphene films on copper substrates with an average Raman peak intensity ratio [Formula: see text] of 0.17. Backscattered electron microscopy reveals a characteristic grain size of 120 [Formula: see text]m, with an area ratio of 16 when compared to that of low-quality graphene on copper. The reported solar-thermal CVD system demonstrates the ability to produce a high-value product, namely, graphene on copper, directly from a renewable energy resource with process control and automation that enables synthesis under a variety of conditions.
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.
Mass production of graphene by plasma or thermal chemical vapor deposition consumes much energy, with potentially adverse effects on the environment. This work reports the use of a high-flux solar simulator that approximates the sun's spectrum and a cold-wall chemical vapor deposition reactor to demonstrate a renewable energy process for graphene growth. Synthesis of highquality (I D /I G = 0.13) AB-stacked bilayer graphene with greater than 90% coverage is achieved on commercial polycrystalline copper in a one-step process and a short time of 5 min. The graphene exhibits large grain sizes of up to 20 μm with spatial uniformity over a large area up to 20 mm in radius. The transmissivity and sheet resistance of the graphene films fall in the ranges of 92.8−95.3% and 2−4 kΩ/sq, respectively. Thus, direct solar capture provides a compelling option for graphene synthesis that can potentially decrease fabrication costs and environmental pollution.
Mass production of graphene by plasma or thermal chemical vapor deposition consumes much energy with potentially adverse effects on the environment. This work reports the use of a high-flux solar simulator that approximates the sun's spectrum and a cold-wall chemical vapor deposition reactor to demonstrate a renewable energy process for graphene growth. Synthesis of high-quality (I_{D}/I_{G} = 0.13) AB-stacked bilayer graphene with greater than 90% coverage is achieved on commercial polycrystalline copper in a one-step process and short time of 5 min. The graphene exhibits large grain sizes of at least 20 micron with spatial uniformity over a large area up to 20 mm in radius. The transmissivity and sheet resistance of the graphene films fall in the ranges of 92.8-95.3% and 2-4 kOhm/sq. Thus, direct solar capture provides a compelling option for graphene synthesis that can potentially decrease fabrication costs and environmental pollution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.