LAUSR

An attempt has been made to combine small-angle scattering of X-rays or neutrons with scanning electron microscopy in reciprocal space, in order to establish a structural analysis method covering a wide range of sizes from micro- to macro-scales. A system with a binary contrast, in which scattering objects with a homogeneous density are dispersed in vacuum (or air), is considered. A topological surface image, detected by secondary electron emission, is converted by means of a Fourier transform into a two-dimensional scattering amplitude in reciprocal space. The method was first tested by studying a dilute system of monodisperse SiO2 particles, with respect to calibrations for brightness inversion, noise reduction and two-dimensional Fourier transform, to obtain a scattering amplitude that agrees well with the analytical amplitude for a spherical particle. Secondly, the microstructure of a carbon-supported Pt catalyst for polymer electrolyte fuel cell applications was examined with the combined method, covering length scales from 10 µm down to nanometres. After two-dimensional Fourier transformation, the secondary electron emission images with low magnification are able to overcome the limitation of the minimum wavenumber (q min) detectable by ultra-small-angle scattering.