The Geometrical Theory of Electron Diffraction and Analysis of Clay Mineral Diffraction Patterns
01 Jan 1967-pp 81-158
TL;DR: In a crystalline substance, the material particles (atoms, ions, or molecules) are distributed in a regular manner, forming the crystal structure as mentioned in this paper, and both the individual particles and their groupings alternate in three dimensions in such a way that their relative environments are the same throughout the structure.
Abstract: In a crystalline substance, the material particles (atoms, ions, or molecules) are distributed in a regular manner, forming the crystal structure. In this structure, both the individual particles and their groupings alternate in three dimensions in such a way that their relative environments are the same throughout the structure. Thus, any arbitrary point in the structure corresponds to a multitude of other points, identical to it and arranged in a definite sequence which varies with the particular structure. Any of these sets of identical points having the same relative spatial arrangement is a characteristic feature for a given structure and, under the name of a space lattice, serves as a means of describing the structure.
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TL;DR: The field of atomic-resolution transmission electron microscopy and its application to materials science is reviewed in this paper, where the statistical principles of quantitative image analysis and defect modelling are outlined for both HREM and STEM.
Abstract: The field of atomic-resolution transmission electron microscopy and its application to materials science is reviewed. This technique, whose spatial resolution is now about one Angstrom, is valuable wherever nanoscale characterization of materials is needed. The history of the subject is briefly outlined, followed by a discussion of experimental techniques. Resolution-limiting factors are summarized, together with the underlying theory of image formation. Seven promising approaches to super-resolution are reviewed. The statistical principles of quantitative image analysis and defect modelling are outlined for both HREM and STEM. Methods for obtaining defect energies from images are discussed. The review ends with a summary of some recent applications, including such topics as the Fullerenes, nanotubes, dislocation kink imaging, superconductors, atomic-resolution imaging of whole semiconductor devices, the study of atomic defects in mediating first-order phase transitions, collosal magnetoresistance, ceramic interfaces, quasicrystals, imaging of surfaces, glasses, catalysts and magnetic materials.
80 citations
TL;DR: In this paper, the idealized symmetry of 1:1 phyllosilicates is analyzed in detail, and the possible stacking sequences result from the different kinds of pairs of kaolinite layers.
Abstract: The idealized symmetry of kaolinite-type minerals (1:1 phyllosilicates) is analysed in detail. They can be considered as OD-structures consisting of three kinds of OD-layers. Each of them, taken separately, possesses higher symmetry than their combination. This explains the well-known tendency of kaolinite-type minerals to form a wide variety of ordered and disordered polytypes as well as twins. The possible stacking sequences result from the different kinds of pairs of kaolinite layers which are derived for dioctahedral, trioctahedral as well as 'monoctahedral' kaolinite-type minerals, the latter being defined as those in which the three octahedral positions are occupied by three different cations or two different cations and a void. The analysis makes use of a simple symbolism and a simplified pictorial representation. A brief summary of the most important terms and definitions of the theory of OD-structures is given in an Appendix.
54 citations
TL;DR: In this paper, a periodicity of 14 A is recognized as a typical modulation period in metakaolinite and different types of modulations, with periods in the range from ∼1.4d001 (9.47 A) to 2.89 A, form along the c*-axis.
Abstract: For the first time, a periodicity of 14 A is recognized as a typical modulation period in metakaolinite. Energy-filtered electron diffraction data confirm that dehydroxylation does not occur abruptly in kaolinite. The degree of ordering becomes much lower during the progression of dehydroxylation in metakaolinite than in kaolinite. However, different types of modulations, with periods in the range from ∼1.4d001 (9.47 A) to 2.9d001 (19.89 A), form along the c*-axis in metakaolinite. Modules (14.2 A= 2.1d001) that have a length that is approximately twice as long as the metakaolinite layer (6.86 A) are the most common. Presumably, the remnant oxygens and vacant anion sites rearrange to acquire stability in the layer structure, which builds modulations along the c*-axis in the metakaolinite.
40 citations
TL;DR: Clay mineral studies in the U.S.R., mainly since 1960, are summarized in this article, where electron diffrac- tion techniques especially have been developed and used extensively for simultaneous recording of DTA curves and other properties.
Abstract: Clay mineral studies in the U.S.S.R., mainly since 1960, are summarized. Electron diffrac- tion techniques especially have been developed and used extensively. Methods have been developed for simultaneous recording of DTA curves and other properties. Polytypism of phyllosilicates has been studied intensively by Zvyagin and others. Mucfi new information on the structure and morphol- ogy of halloysites has been obtained by electron-optical methods. Other clay minerals extensively studied include allophanes, kaolinites, chlorites ("donbassite" is preferred to "sudoite" for diocta- hedral varieties), alushtite (or tosudite), monothermite, and various zinc-bearing clays. Much attention has been given to physico-chemical and colloid-chemical properties. The natural occurrence and alteration of clays and clay minerals are described in weathering and oxidation zones, in soils, and in Recent and Ancient sediments. Primary clay minerals of hydrothermal origin are described.
12 citations