X-ray Diffraction Profiles Modeling Method for Layered Structures Reconstruction: Nanoclay Structural Verification

Abstract

The nanoclay properties find a large environmental application domain as depolluant, ion exchanger, natural geological barrier for industrial and radioactive waste confinement, clay-based nanocomposite for drug delivery, and more. Layered materials, such as nanoclay, present rather complex structures whose classical characterization requires a complementarity between several analysis methods to decipher the effects of interstratification (and its cause) on the intrinsic functional properties. The appearance of defects related to the layers stacking mode, which differ in their thickness and/or their internal structure are directly related to the reactivity of the mineral’s surface. During the last decades, and with the development of computer codes, the modeling of X-ray diffraction profiles has proven to be an important tool that allows detailed structural reconstruction. The quantitative XRD analysis, which consists of the comparison of experimental (00l) reflections with the calculated ones deduced from structural models, allowed us to determine the optimal structural parameters describing interlamellar space (IS) configuration, hydration state, cation exchange capacity (CEC), layer stacking mode, and theoretical mixed-layer structure (MLS) distribution. This chapter will review the state of the art of this theoretical approach as a basic technique for the study of nanoclays. The basic mathematical formalism, the parameters affecting the theoretical models, and the modeling strategy steps will be detailed in concrete examples.