Surface and pore structure characterisation by neutron scattering techniques

Neutron scattering techniques can provide extensive information about the microstructure of porous materials and the properties of adsorbates 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 interaction of the neutron with the atomic nucleus and has no equivalent with either X-ray or light radiation. Here the application of small angle neutron scattering (SANS) is reviewed with particular emphasis on two recent developments. The first concerns contrast variation methods to investigate adsorption mechanisms, which include the capillary condensation of benzene in a mesoporous silica gel. The second concerns the examination of oriented anisotropic porous microstructures, as can occur in microporous carbon fibres. The applications of incoherent inelastic and quasielastic scattering together with neutron diffraction are also described. Here the investigation of the state of water in micro and mesoporous silica gels with a model pore structure is illustrated. It 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.