Layered Mineral Structures and their Application in Advanced Technologies
This volume covers the topics related to the 13th EMU School ‘Layered Mineral Structures and their Application in Advanced Technologies’. All of the selected topics, the school, and this volume are thus aimed at providing an in-depth knowledge of the complex field of layered materials, with an attempt to address several fundamental aspects, which range from crystal chemistry and structure to layer packing disorder, from surface properties to the description of the most advanced experimental techniques useful in the characterization of layered materials. Layered materials, because of their particular atomic arrangement, are commonly characterized by physical and chemical properties of great interest in numerous technological and environmental processes and applications, as better detailed in the body of this volume. Most of these properties play a significant role in Earth sciences, environmental sciences, technology, biotechnology, material sciences and many other scientific areas. The surface properties of layered materials control important interaction processes, such as coagulation, aggregation, sedimentation, filtration, catalysis and ionic transport in porous media. Layered minerals also control many aspects of Earth's rheology, i.e. the movement of geological masses, at least as far down as the lower crust. Given this frameset, it should be no surprise that the extremely large field of investigation of these materials can, and in most of the cases must, be approached from several different viewpoints. However, providing full coverage of the immense literature devoted to all the topics above may be impractical, if not impossible.
Advanced techniques to define intercalation processes
Published:January 01, 2011
Annibale Mottana, Luca Aldega, 2011. "Advanced techniques to define intercalation processes", Layered Mineral Structures and their Application in Advanced Technologies, M.F. Brigatti, A. Mottana
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Intercalation is the inclusion or reversible insertion of a guest chemical species (atom, ion, molecule) in a virtually unchanged host-crystal structure. Any type of layer-structured material may give rise to intercalated compounds, the guest species being artificially inserted or naturally included between the host sheets without loss of their planarity. Layer silicates, in particular, may be considered intercalated structures where interlayer guest species and complexes are inserted between the silicate layers. The most common guest species is H2O, which is generally present under natural conditions in intercalated layer silicates such as smectites, vermiculite and halloysite.
Past research focused attention on the swelling/shrinking behaviour of intercalated compounds with respect to H2O, and also on the non-stoichiometric, heterogeneous complexes formed from organic liquids such as ethylene glycol and glycerol. The unique combination of layer-silicate features (small crystal size, large surface area) and the small concentrations required to effect a change in the matrix, both coupled with the advanced characterization techniques available, have generated much interest. This interest extends to the special field of nanocomposites, and of graphene, which is also an intercalated layered structure. In general, any guest material inserted into an interlayer space causes a modification in the structure, with spacing-size changes in a particular crystallographic direction (d value). First, a brief introduction on conventional and synchroton-based X-ray techniques used to define crystal size and thickness is given. Then, the peak-broadening approach by conventional X-ray diffraction (XRD) techniques, such as the Scherrer method is presented. Further on, the crystallinity measurements and the Bertaut-Warren-Averbach (BWA) method used in the MudMaster program are described. A short summary is presented of the grazing-incidence diffraction (GIXRD) technique. Finally, additional and complementary information from X-ray absorption spectrometry (XAS), such as short-range order, and detailed local information on atomic positions by angle-resolved X-ray absorption near-edge stucture (AXANES), polarized extended X-ray absorption fine structure (P-EXAFS), and near-edge extended absorption fine structure (NEXAFS) spectroscopies are analysed and discussed. Examples of the applications of these methods to clay minerals, micas and graphene are given.