Small Angle X-ray Scattering (SAXS) is a powerful technique to measure particle size in nanomaterials. In general the technique measures and models diffuse X-ray scattering at very low angle caused by electron density fluctuations in the material under study. In the case of particle size measurements the electron density fluctuation is caused by the presence of particles and their surrounding voids within the sample. The scattering can be interpreted by modeling the particle size, calculating the expected data, and refining the model such that the calculated data best matches the experimental curve.
Palladium (Pd) on silica is a well known heterogeneous catalyst in many industrial processes, such as hydrogenation. An extremely important parameter for controlling the activity of the catalyst is its particle size. Figure 1 depicts the SAXS data collected from a Pd on silica catalyst using Rigaku's Ultima IV multipurpose diffraction system configured for SAXS measurements.
Figure 2 displays the calculated SAXS data from the final particle size distribution model refined to fit the experimentally collected data.
Figure 3 shows the final particle size distribution used to calculate the refined data.