We report experimental results on the structure and melting behavior of ice confined in multi-walled carbon nanotubes and ordered mesoporous carbon CMK-3, which is the carbon replica of a SBA-15 silica template. The silica template has cylindrical mesopores with micropores connecting the walls of neighboring mesopores. The structure of the carbon replica material CMK-3 consists of carbon rods connected by smaller side-branches, with quasi-cylindrical mesopores of average pore size 4.9 nm and micropores of 0.6 nm. Neutron diffraction and differential scanning calorimetry have been used to determine the structure of the confined ice and the solid-liquid transition temperature. The results are compared with the behavior of water in multi-walled carbon nanotubes of inner diameters of 2.4 nm and 4 nm studied by the same methods. For D(2)O in CMK-3 we find evidence of the existence of nanocrystals of cubic ice and ice 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 crystal forms only occur at temperatures below 170 K in the case of cubic ice, and at pressures of hundreds or thousands of MPa in the case of ice VIII and IX. These phases appear to be stabilized by the confinement.
The crystal and magnetic structures of TlFeS 2 and TlFeSe 2 chalcogenides are studied by neutron diffraction in the temperature range 10-300 K. The investigated compounds feature monoclinic crystal sym metry with the C2/m space group. Antiferromagnetic ordering occurs in TlFeS 2 and TlFeSe 2 at the Néel tem perature T N = 210(5) and 295(5) K, respectively. The temperature dependences of magnetic moments, Fe-Fe bond lengths, and unit cell volume are established. The coefficients of thermal expansion for the paramag netic and antiferromagnetic phases are calculated.
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