The micro-structure of lactose powder compacts studied by small-angle and ultra small-angle X-ray scattering

The objective was to derive indications of the microstructure of lactose powder compacts was studied by small-angle and ultra small-angle X-ray scattering experiments (SAXS/USAXS). Measurements were performed on a series of lactose powder compacts formed at four different pressures in the interval 300–1000 MPa. Porod analyses of the 1-D scattering profiles, i.e. intensity vs. magnitude of scattering vector ( q ), enabled accurate determinations of the specific surface area. From these, the interparticle contact area was estimated and compared to the compact tensile strength. Measures of the volume fraction and sizes of the voids were obtained from a fit of a model of polydisperse cylindrical pores. These were found to be approximately disc-shaped, with one dimension significantly smaller than the other two. The scattering data were consistent with an isotropic distribution of pores. The void volume fractions, void sizes and specific surface areas showed anti-correlating trends with the pressure applied. • SAXS used in a novel way to study microstructure in lactose powder compacts. • Reliable values of surface area and SAXS determined porosity. • USAXS used to indicate shape of pores. • Linking particle contact area, mechanical strength and SAXS determined porosity.