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Abstract: X-ray diffraction patterns of ethanol confined in parallel-aligned channelsof approx. 10 nm diameter and 50 micrometer length in mesoporous silicon havebeen recorded as a function of filling fraction, temperature and for varyingcooling and heating rates. A sorption isotherm, recorded in the liquid state,indicates a three monolayer thick, strongly adsorbed wall layer and a capillarycondensed fraction of molecules in the pore center. Though the stronglyadsorbed film remains in an amorphous state for the entire temperature rangeinvestigated, the capillary condensed molecules reproduce the polymorphism ofbulk solid ethanol, that is the formation of either crystalline or glass-likestates as a function of cooling rate. The critical rate necessary to achieve avitrification in the mesopores is, however, at least two orders of magnitudesmaller than in the bulk state. This finding can be traced both to puregeometrical constraints and quenched disorder effects, characteristic ofconfinement in mesoporous silicon.



Author: Anke Henschel, Klaus Knorr, Patrick Huber

Source: https://arxiv.org/







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