Novel application of anomalous small-Angle X-ray scattering to characterize inhomogeneities in materials

Significant changes in small-angle X-ray scattering intensity can be induced when the energy of incidental Xrays is tuned close to the vicinity of an absorption edge of an appropriate atom contained in the sample. This method enables us to offer new information with respect to the inhomogeneities in materials, for instance, the nature of GP zones in Al-based alloys, the decomposition process, the nature of the scattering tail in Cu-Ni-Sn alloys, and composition modulation in Fe-Ge alloys. The determination of the partial structural functions in ternary alloys and the specific volume ratio in multi-layers is also very useful. Since the interpretation of the small-angle X-ray scattering data, in principle, depends on the models used for theoretical calculation of the intensity, it is frequently found that more than two kinds of models can fit the experimental data equally well. The anomalous small-angle X-ray scattering data can provide an answer for such an inconvenience. In light of these advantages, the harmonious combination of small-angle X-ray scattering and the anomalous dispersion effect with the use of the intense white X-ray source of synchrotron radiation has emerged as a new and powerful method for characterizing the inhomogeneities in materials at a microscopic level. An attempt has been made in this review to present an extended introductory treatise on the novel application of anomalous small-angle X-ray scattering to characterization of inhomogeneities in materials with some selected examples in metallurgy and polymer science.