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- 摘要
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- 实验方案
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Pushing Boundaries: High Pressure, Supercritical Optical Floating Zone Materials Discovery
摘要： In this perspective review, we provide the rationale for utilizing supercritical fluids for solid state materials discovery in the context of recent advances in the field of high pressure synthesis. We discuss the importance of the transition from gas-like to solvent-like environments in which materials synthesis and crystallization is occurring, the appropriate conceptual frameworks for its impact on synthesis and directional solidification, and dispel popular myths. We provide an overview of materials that have been grown in single crystal form by the high pressure optical floating zone technique, report the first successful stable molten zone in an optical furnace at P = 300 bar, and show viability of the traveling solvent method even with high fluid pressures. Further, we report on some unexpected observations found in the highly dynamic synthesis environment of supercritical fluids, enabled by the ability to observe, in real time, materials behavior. Finally, we offer a perspective on the scientific domains opened by these new capabilities.
关键词： Single crystal growth,Materials discovery,Optical floating zone,High pressure synthesis,Supercritical fluids
更新于2025-09-23 15:19:57
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Carbon coated TiO2 nanoparticles prepared by pulsed laser ablation in liquid, gaseous and supercritical CO2
摘要： We report on the synthesis of TiO2 nanoparticles using nanosecond pulse laser ablation of titanium in liquid, gaseous and supercritical CO2. The produced particles were observed to be mainly anatase-TiO2 with some rutile-TiO2. In addition, the particles were covered by a carbon layer. Raman and X-ray diffraction data suggested that the rutile content increases with CO2 pressure. The nanoparticle size decreased and size distribution became narrower with the increase in CO2 pressure and temperature, however the variation trend was different for CO2 pressure compared to temperature. Pulsed laser ablation in pressurized CO2 is demonstrated as a single step method for making anatase-TiO2/carbon nanoparticles throughout the pressure and temperature ranges 5–40 MPa and 30–50 °C, respectively.
关键词： core-shell particles,pulsed laser ablation,nanoparticle size control,supercritical fluids
更新于2025-09-11 14:15:04
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Raman thermometry in water, ethanol and ethanol/nitrogen-mixtures from ambient to critical conditions
摘要： We present investigations into remote liquid temperature sensing with Raman spectroscopy using different evaluation methods for the OH stretching vibration band. Water, ethanol and ethanol saturated with nitrogen, all as liquids or liquid-like supercritical fluids, are pumped through a heated microcapillary system at elevated pressures. Raman spectra are recorded from the liquid inside the microcapillary and are evaluated with respect to the temperature sensitivity of the OH stretching vibration. The four approaches applied are (i) to evaluate the center position of the Raman OH-band, (ii) the integrated absolute difference spectrum, (iii) the intensity ratio of two regions of the OH-band, and (iv) the intensity ratio of two fitted Gaussian peaks. The temperature range investigated covers from ambient temperature to the component’s respective boiling temperature or critical temperature at sub- and supercritical pressures. Precision and robustness of the employed methods are characterized. It is shown that two out of the four methods feature temperature deviations smaller than 5 K at all pressures, and that one method can also be applied to liquid mixtures of ethanol and nitrogen. Applicability to other liquids and mixtures is discussed.
关键词： temperature sensing,supercritical fluids,OH stretching vibration,water,Raman spectroscopy,nitrogen,microcapillary,ethanol
更新于2025-09-04 15:30:14