Small-angle X-ray scattering (SAXS) study of porous anodic alumina—A new approach

Small angle X-ray scattering (SAXS) has been performed on porous anodic alumina prepared at 10, 20 and 30 V. These were prepared by two-step anodizing to have uniform through-thickness structure. The thickness of the membranes was of the order of 100–200 μm. The scattering has been explained on the basis of structure factor; the magnitude of scattering vectors (q) corresponding to well-established peaks being multiples of 2π/d, where d is the inter-pore distance. The usually studied form factor has not been found to play any profound role to determine the scattering response of anodic alumina. A large number of experiments have been performed with various geometries of the anodic alumina with respect to the incident beam. The scattering has been extremely anisotropic, where q always lies at about 90° with respect to the sample's normal. A deviation from this angle which is limited to about ±2° has been due to scatter of the pore axis with respect to sample's normal, which is caused by occasional pore turning, branching and annihilation events. The analysis and methodology adopted in this study has also been suggested as extremely useful for determining the orientation of high-aspect ratio objects in an anisotropic sample along with assessing the degree of misalignment.

► The SAXS spectra clearly suggest that form factor has almost negligible role in the analysis of the SAXS response of alumite membranes and structure factor predominates.
► A sample may be characterized by SAXS at any orientation between face-on and edge-on.
► Based on the present methodology and analysis SAXS response can be successfully exploited to study the mutual variation in the axis of the cylindrical objects.