研究目的
Investigating remote liquid temperature sensing with Raman spectroscopy using different evaluation methods for the OH stretching vibration band in water, ethanol, and ethanol/nitrogen mixtures from ambient to critical conditions.
研究成果
The IADS method is superior in pure fluids as well as mixtures, closely followed by the OHcenter method. These methods are applicable throughout the liquid-like temperature-range at supercritical pressures. The measurement approach is limited to the persistence of a hydrogen bond network in mixtures.
研究不足
The study is limited to the analysis of water, ethanol, and ethanol/nitrogen mixtures. The methods may not be applicable to other liquids or mixtures without hydrogen bond networks. The Gauss method fails to provide a reliable fitted function over the complete temperature range.
1:Experimental Design and Method Selection:
The study employs Raman spectroscopy to evaluate the temperature sensitivity of the OH stretching vibration in liquids and liquid-like supercritical fluids. Four different methods are applied to analyze the Raman OH-band.
2:Sample Selection and Data Sources:
Water, ethanol, and ethanol saturated with nitrogen are used as samples. These are pumped through a heated microcapillary system at elevated pressures.
3:List of Experimental Equipment and Materials:
A high precision high pressure syringe pump, a microcapillary system, a continuous wave laser operating at 532 nm, a fiber-coupled spectrometer, and a photodetector for phase-selective measurements.
4:Experimental Procedures and Operational Workflow:
The temperature is increased in 10 K steps from ambient temperature to the fluid’s boiling point or critical point. At each step, 32 spectra are recorded with 4 s integration time.
5:Data Analysis Methods:
The Raman OH-band is evaluated using four different methods to correlate the spectral features with temperature.
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