The epitaxial growth of ice on single-crystalline substrates |
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| Affiliation: | 1. Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali, Università di Bologna, via Terracini 28, 40131, Bologna, Italy;2. Centro di Studi sulla Corrosione e Metallurgia “A. Daccò”, University of Ferrara, Via G. Saragat, 4/a, 44122 Ferrara, Italy;3. Centre Interuniversitaire de Recherche et d''Ingénierie des Matériaux, Université de Toulouse, 4 allée Emile Monso, 31030 Toulouse, France;4. Synchrotron SOLEIL, L''Orme des Merisiers, 91190 Saint-Aubin, France;5. TRACES lab (CNRS UMR5608), Université de Toulouse, allées Antonio-Machado, 31058 Toulouse, France;6. Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, viale Risorgimento 4, 40136 Bologna, Italy;7. Dipartimento di Ingegneria Industriale, Università di Bologna, viale Risorgimento 4, 40136 Bologna, Italy;8. Dipartimento di Beni Culturali, Università di Bologna, via degli Ariani 1, 48121 Ravenna, Italy;1. School of Chemistry and Physics, University of KwaZulu-Natal, P/Bag X54001, Westville, Durban, South Africa;2. Department of Pure and Industrial Chemistry, Faculty of Physical Sciences, University of Nigeria, Nsukka 410001, Enugu State, Nigeria;1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun, 130022, PR China;2. School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei, 230026, PR China;1. Faculty of Physics, Saint-Petersburg State University, 1 Ulyanovskaya str., St. Petersburg, 198504, Russia;2. ITMO University, 49 Kronverksky Pr., St. Petersburg, 197101, Russia;3. St. Petersburg State University of Civil Aviation, Pilotov Str. 38, St. Petersburg, 196210, Russia |
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| Abstract: | Epitaxial deposits of ice crystals have been formed on the basal (0001) faces of hexagonal AgI, PbI2, CuS, CdI2 and brucite, on the (001) face of freshly-cleaved muscovite, on the (010) face of orthorhombic HgI2, on the (001) face of orthorhombic iodine, on the (100) face of V2O5and on the rhombohedral faces of calcite. The temperature at which ice crystals first appear on a particular substance is very close to the threshold temperatures at which an aerosol of the same substance nucleates a cloud of supercooled water droplets.The crystals appear preferentially at cleavage and growth steps on the substrate surface, provided that these exceed ~ 0.1μ in height and preserve their parallel orientation irrespective of the direction of the step.Thin, hexagonal ice plates, growing on the basal plane of covellite (CuS), show interference colours which give a measure of their thickness. Commonly, the ice crystals increase appreciably in diameter with no discernible change of thickness, suggesting that molecules arriving on the upper surface are not assimilated but migrate over the surface and are built in at the crystal edges. Crystals usually thicken on touching a neighbouring crystal; coloured growth fronts are then seen spreading out across the crystal surface from the point of contact.Detailed measurements on AgI, PbI2, CuS and CdI2 show that, for a given substance, there is a well-defined critical temperature above which ice crystals can appear only if the air exceeds saturation relative to liquid water, but below which ice forms directly from the vapour phase provided that the supersaturation relative to ice exceeds 12 per cent for silver iodide and slightly different values for the other substrates. These critical supersaturations are required for growth at the edges of steps; ice appears on the flat parts of the substrate only at much higher supersaturations (> 100 per cent). |
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