Overall investigation of the behavior of water/ice in almost and partially filled nanopores of SBA-15 silica by neutron diffraction technique

A neutron diffraction technique is used to study the structural characterization of water/ice in mesoporous sba-15 silica with 86°a nanopore diameter. different filling factors of the silica pores were considered over a wide temperature range. neutron diffraction data for the almost-filled case, with a filling factor of 0.95, which undergoes a temperature change of 300-100k, shows a main asymmetric triplet peak 1.74°a^-1. using five symmetric functions, we found an excellent fit with the whole range of data sets for the triplet. interestingly, each of these functions is directly linked to the position of the different ice components and shows a systematic variation of peak parameters. as a complementary experiment, data analysis of the partially-filled cases, with filling factors of 0.6 (300-130 k) and 0.4 (300-100 k), show characteristics that are markedly different from those of the filling factor 0.95. the nucleation temperature for all cases is reduced and different ice structures, along with their temporal order, have been detected for confined water. further investigations confirm that for different filling factors, there are different amounts of hexagonal, cubic and disordered ice components. surprisingly, data analysis proved the reversibility of the whole nucleation process, although the formation/melting of the ice in the main body of the pore showed the expected hysteresis.