Analysis Of The Dynamics Of Water Confined In M-S-H Based On The Quasi-elastic Neutron Scattering Spectra

Neutron scattering is an experimental technique to reveal microstructure and behavior of materials,since neutrons have some special properties as follows:neutrons bear with no net electric charge,but with magnetic moment;neutrons are highly penetrating and non-destructive;neutrons are so sensitive that distinguish light element and isotopes.The China Spallation Neutron Source（CSNS）,a major national scientific device,will be operated in the near future and will have applications in condensed physics,chemistry,material science,life science and nanotechnology.In this work,magnesium-silicate-hydrate（M-S-H）cement is the experimental material.There are two kinds of water in the cementitious system.One is bound water that is immobile.The other one is constrained water that is mobile.Two components vary for time,temperature,additives and so on,which control the physical properties of cement paste,including mechanical properties and durability.In this work,Jump-Diffusion and Rotation-Diffusion Model（JRM）is used to fit the quasi-elastic neutron scattering（QENS）spectra from M-S-H.Five extracted parameters of JRM describing the dynamics of water confined in these cementitious systems are obtained:the Debye-Waller factor A,the index of immobile water C,the self-diffusion coefficient D_t,the average residence time between two jumpsτ₀ and the rotational diffusion constant D_r.The extracted parameters and their composed parameters illustrate that there is a crossover phenomenon of confined water at220-230 K.Comparing with the fitting result of QENS spectra from calcium-silicate-hydrate（C-S-H）,we can reveal the dynamics of confined water in different kinds of pores in cement furthermore.At the same time,we simulate hydrogen and water storage in single-walled carbon nanotubes（SWNT）,in order to study dynamical behavior of water in confinement spaces.