8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Thu 811:10-14:00P7.91Experimental study of ice premelting in porous matrix ofsynthetic opalVitaly Podnek, 1 Vitaly Voronov, 1 Evgenii Gorodetskii, 1 Elena Pikina, 1 and VladimirKuzmin 11 Oil & Gas Research Institute of the Russian Academy of Sciences, Gubkin str. 3,119333, Moscow, Russian FederationWe investigated temperature dependence of enthalpy and heat capacity of ice premelting (a meltingbelow bulk melting temperature) [1] in a porous matrix of two-generation synthetic opal in a temperaturerange from 160 K to 280 K. The porous opal matrix is formed by dense (fcc) packing ofnearly mono-sized spheres of amorphous silicone dioxide with diameter of an order of some hundredsnanometers which are in turn formed by fractal packing of primary (first generation) spheresin diameter of an order of some nanometers. On the temperature dependence of apparent heatcapacity of ice in the opal matrix are presented two well-separated Kelvin peaks correspondingto melting of ice in interstices formed by first (small) and second (large) generation opal particlesrespectively. The excess heat capacity in temperature interval between the Kelvin peaks correspondsto ice premelting on surface of large spherical opal particles, near the contacts betweenthem and on grain boundaries between ice crystallites. Experimental results are analyzed withinCahn-Dash-Fu theory of ice melting in a closely packed system of mono-sized spherical particles[2]. This theory considers gradual melting of ice in porous media as a consequence of interfacialand grain boundary melting combined with curvature-induced Kelvin depression of the meltingpoint. Our data shows that ice premelting in porous matrix of synthetic opal represents an idealobject for experimental verification of the CDF theory.[1] J. G. Dash, A. W. Rempel and J. S. Wettlaufer, Rev. Mod. Phys. 78, 699 (2006).[2] J. W. Cahn, J. G. Dash and H. Fu, J. Crystal Growth 123, 101 (1992).91