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Abstract. Neutron diffraction and NMR relaxation studies have been made of water/ice in mesoporous SBA-15 silica with ordered structures of cylindrical mesopores with a pore diameter ∼8.6 nm, over the temperature range 180 K to 300 K. Both measurement show similar depressed freezing and melting points due to the GibbThomson effect,The neutron diffraction measurements for fully filled pores show, in addition to cubic and hexagonal crystalline ice, the presence of a disordered water/ice component extending a further 50 to 80 K, down to around or below 200 K. NMR relaxation measurements over the same temperature range show a free induction decay that is partly Gaussian and characteristic of brittle ice but that also exhibits a longer exponential relaxation component. An argument has been made (Liu et al., 2006;Webber et al., 2007) to suggest that this is an observation of ice in a plastic or rotationally mobile state, and that there is a fully-reversible inter-conversion between brittle and plastic states of ice as the temperature is lowered or raised. More recent detailed NMR measurements are also discussed, that allow the extraction of activation enthalpies and an estimate to be made of the equilibrium thickness, as a function of temperature, if the the assumption is made that the plastic component is in the form of a layer at the silica interface. The two different techniques suggest a maximum layer thickness of about 1.0 to 1.5 nm.

Small-angle neutron-scattering (SANS) measurements have been made for a series of aerosol-OT (A0T)-stabilised water-in-oil microemulsions. The intensity pattern has been used to extract a value for the radius of the water core, rw, using D,O to provide the required contrast profile. In heptane the radii are found to follow an approximately linear relationship with respect to the [D,O]/[AOT] concentration ratio, R. At 20 OC, and R = 20, the structure of the water-droplet system is dependent on the hydrocarbon chain length of the oil medium. The experimental SANS patterns show increasing discrepancies with a fitted function based on monodisperse spheres as the length of the alkane chain is increased from n-heptane to n-dodecane. This effect is attributed to polydispersity and indicates that the droplet-size distribution within these microemulsion systems is much larger than had previously been thought.Previous studies by photon correlation spectroscopy 2-4 and 13