Dynamic and structural properties of confined phases (hydrogen, meth-ane and water) in MCM-41 samples (19A, 25A and 40A)

摘要

The structural and / or dynamic properties of confined phases (mainly hydrogen, methane and water) in MCM-41 samples (19 A, 25 A and 40 A) have been investigated by neutron diffraction (ND) and incoherent quasi-elastic neutron scattering (IQENS) respectively. A special interest concerns the temperature dependence of hte structural range order L_coher. and of hte translational mobility D_t which characterizes the molecular sorbate species. Abrupt variations of such structural (L_coher.) and dynamic (D_t) properties versus temperature are clear signatures of capillary phase transitions. A good illustration is the solidification at T=62 K of the confined methane phase in MCM-41 (PHI = 40 A). We have also investigated the structural and dynamic properties of the physisorbed film on the inner pore surface for hte hydrogen / MCM-41 (PHI = 24 - 25 A) system. A clear evidence of a solid physisorbed film i ncoexistence with a capillary liquid phase has been observed at T = 14.6 K.