SURFACE AND PORE STRUCTURE CHARACTERIZATION BY NEUTRON-SCATTERING TECHNIQUES

Neutron scattering techniques can provide extensive information about the microstructure of porous materials and the properties of adsorbate s within the pores. This information is obtained from measurements of both coherent and incoherent scattering. Coherent scattering comprises diffraction and small angle scattering (SAS) and has a counterpart in X-ray scattering. Incoherent scattering arises from a unique interact ion of the neutron with the atomic nucleus and has no equivalent with either X-ray or light radiation. Here the application of small angle n eutron scattering (SANS) is reviewed with particular emphasis on two r ecent developments. The first concerns contrast variation methods to i nvestigate adsorption mechanisms, which include the capillary condensa tion of benzene in a mesoporous silica gel. The second concerns the ex amination of oriented anisotropic porous microstructures, as can occur in microporous carbon fibres. The applications of incoherent inelasti c and quasielastic scattering together with neutron diffraction are al so described. Here the investigation of the state of water in micro an d mesoporous silica gels with a model pore structure is illustrated. I t is shown that these techniques give evidence of a perturbed H-bonded structure of water due to confinement in pores. This affects both the diffusional behaviour and freezing properties of the water. (C) 1998 Elsevier Science B.V. All rights reserved.