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

P7.110Thu 811:10-14:00Novel ice structures in carbon nanopores: pressureenhancement effect of confinementMalgorzata Sliwinska-Bartkowiak, 1 Monika Jazdzewska, 1 Liangliang Huang, 2 andKeith Gubbins 21 A. Mickiewicz University in Poznan, Faculty of Physics, Umultowska 85 61-614, Poznan,Poland2 Department of Chemical and Biomolecular Eng., Raleigh, United States of AmericaWater confined in a nanoscale environment exhibits unique properties and has been the subjectof much attention. It is frequently observed that phase changes that only occur at high pressuresor low temperatures in the bulk phase occur in the confined phase at pressures that are ordersof magnitude lower (bulk phase pressure in equilibrium with the confined phase) and at normaltemperatures. The structure of confined ice could be a further example of the quasi-high pressureeffect in confinement. We report experimental results on the structure and melting behavior ofice confined in multi-walled carbon nanotubes and ordered mesoporous carbon CMK-3, whichis the carbon replica of a SBA-15 silica template. The silica template has cylindrical mesoporeswith micropores connecting the walls of neighboring mesopores. The structure of the carbonreplica material CMK-3 consists of carbon rods connected by smaller side-branches, with quasicylindricalmesopores of average pore size 4. 9 nm and micropores of 0. 6 nm. Neutron diffractionand differential scanning calorimetry have been used to determine the structure of the confined iceand the solid-liquid transition temperature. The results are compared with the behavior of waterin multi-walled carbon nanotubes of inner diameters of 2. 4 nm and 4 nm studied by the samemethods. For D 2 O in CMK-3 we find evidence of the existence of nanocrystals of cubic ice andice IX; the diffraction results also suggest the presence of ice VIII, although this is less conclusive.We find evidence of cubic ice in the case of the carbon nanotubes. For bulk water these crystalforms only occur at temperatures below 170 K in the case of cubic ice, and at pressures of hundredsor thousands of MPa in the case of ice VIII and IX. These phases appear to be stabilized by theconfinement.110