Direct observation of homogeneous cavitation in nanopores

We report on the evaporation of hexane from porous alumina and silicon membranes. These membranes contain billions of independent nanopores tailored to an ink-bottle shape, where a cavity several tens of nanometers in diameter is separated from the bulk vapor by a constriction. For alumina membranes with narrow enough constrictions, we demonstrate that cavity evaporation proceeds by cavitation. Measurements of the pressure dependence of the cavitation rate follow the predictions of the bulk, homogeneous, classical nucleation theory, definitively establishing the relevance of homogeneous cavitation as an evaporation mechanism in mesoporous materials. Our results imply that porous alumina membranes are a promising new system to study liquids in a deeply metastable state.Comment: 14 pages , 4 figures. Source files also contain Supplemental Material (Doebele_HomogeneousCavitationMembranes_SM.pdf

Functionalization of glassy carbon electrode by amines electrochemical oxidation for micropollutants detection in water

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Phenylamide-oxime and phenylamide nanolayer covalently grafted carbon via electroreduction of the corresponding diazonium salts for detection of nickel ions

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Fractional Factorial Design Study on the Performance of GAC-Enhanced Electrocoagulation Process Involved in Color Removal from Dye Solutions

material

Evaporation process in porous silicon: cavitation vs pore-blocking

International audienceWe have measured sorption isotherms for helium and nitrogen in wide temperature ranges and for a series of porous silicon samples, both native samples and samples with reduced pore mouth so that the pores have an ink-bottle shape. Combining volumetric measurements and sensitive optical techniques, we show that, at high temperature, homogeneous cavitation is the relevant evaporation mechanism for all samples. At low temperature, the evaporation is controlled by meniscus recession, the detailed mechanism being dependent on the pore length and on the mouth reduction. Native samples and samples with ink-bottle pores shorter than one micrometer behave as an array of independent pores. In contrast, samples with long ink-bottle pores exhibit long-range correlations between pores. In this latter case, evaporation takes place by a collective percolation process and not by heterogeneous cavitation as previously proposed. The variety of evaporation mechanisms points to porous silicon being an anisotropic three dimensional pore network rather than an array of straight independent pores