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2 Solar Cells
Published in R D Tomlinson, A E Hill, R D Pilkington, Ternary and Multinary Compounds, 2020
As-grown Cu-rich CIS film was studied using TEM [6], RBS and AES showed that Cu2Se had segregated to the surface of the CIS layer. TED patterns demonstrated the existence of a three-dimensional crystallographic relationship between the pseudo-cubic Cu2Se and pseudo-cubic CIS with [011]Cu2Se‖[011]CIS and (111)cu2Se‖(111)CIS. A chemical reaction which is resulting in a three dimensional crystallographic relationship between the starting material and the product is called “topotactic reaction”. Fig. 5 shows a high resolution TEM micrograph of the interface between Cu2Se and CIS. These are obvious from the lattice image showing a spacing of 6.7 Å which is characteristic to the Cu2Se and the one showing a lattice spacing of 3.3 Å which is characteristics to the CIS. We can also observe a lattice image of CIS region with a period double that of the bulk (=6.7 Å) near the interface between the Cu2Se and CIS layers.
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Published in Chad A. Mirkin, Spherical Nucleic Acids, 2020
Robert J. Macfarlane, Matthew R. Jones, Byeongdu Lee, Evelyn Auyeung, Chad A. Mirkin
One approach to achieve more complex lattices would be the topotactic insertion of a third nanoparticle component into a preformed binary SL. Topotactic transitions are structural changes to a crystalline solid, where the final lattice is related to the initial lattice by one or more crystallographically equivalent, orientational relationships [26]. Here, we use the term “topotactic intercalation” to describe the insertion of NPs into a binary SL at predefined positions while preserving the symmetry and quality of the initial structure. More simply, a two-component “parent” SL is synthesized using the previously established design rules, then appended with a third “daughter” NP component (Fig. 56.1), analogous to the insertion of lithium atoms into a preexisting metal oxide [27]. This strategy both circumvents many of the possible kinetic structures that could arise from trying to assemble all three NP components simultaneously and provides a means to alter bonding interactions between particles postsynthetically. Herein, we generate five distinct ternary NP SLs by topotactic insertion of particles at programmable positions in a unit cell. Moreover, we demonstrate that these SLs can be reversibly switched between the two-component parent and three-component daughter SLs by raising and lowering the solution temperature.
Polymer Single Crystal Fibers
Published in Menachem Lewin, Jack Preston, Handbook of Fiber Science and Technology, 2017
The different types of solid state polymerization reactions have been discussed in detail by Wegner [11], and his terminology has been adopted in this chapter. The solid state reactions that are relevant to the preparation of polymer single crystal fibers are termed either “topochemical” or “topotactic,” depending on the detailed nature of the reaction. These terms are used to describe reactions that can take place in organic crystals such as single crystals of fiber-forming monomers. In such monomer crystals the molecules are generally separated sufficiently far that they are not able to react. However, if there is sufficient mobility that the molecules are able to move to within about 0.3 nm of each other by diffusion or rotation, then a solid state reaction may occur. Examples [19–21] of such systems in which monomer single crystals can undergo solid state polymerization have been given by Wegner [11], The most important reactions for the formation of good polymer single crystals are topochemical reactions whereby, as Wegner [11] pointed out, “there is a direct transition from the monomer molecules to polymer chains without destruction of the crystal lattice and without the formation of non-crystalline intermediates.”
Experience in Decontamination of Naval Reactor Plants
Published in Nuclear Technology, 2020
B. A. Gusev, I. S. Orlenkov, L. N. Moskvin, N. G. Sandler, A. A. Efimov, А. M. Aleshin, V. V. Krivobokov, V. N. Vavilkin
The composition morphology has a four-layer structure.11–13 A two-layer oxide film is formed directly on the corrosive steel surface. The above layer is a local epitaxic layer of magnetite. The underlying layer is a topotactic layer of nonstoichiometric magnetite, including the oxides of alloying elements. These two layers form a protective corrosion film that is incorporated into the base metal structure.14
Understanding the fundamentals of TiO2 surfaces
Published in Surface Engineering, 2022
The reactive facets of the anatase and rutile due to their relatively high surface energy grow fast as a result of the minimization of the total surface energy of crystals, so that they commonly constitute a very small fraction of the surface area of the final crystals or in fact disappear [49]. The following basic synthesis strategies of clearly faceted titania polymorphs have been used: hydrothermal, solvothermal, and nonhydrolytic methods of wet chemistry, gas oxidation routes, topotactic transformations, crystallization transformations from amorphous TiO2, and epitaxial growth [49]. So far, for anatase crystals, the production of low index facets ({101} [668–685], {001} [49,674,681,682,686,687], {100} [42,661,688–695], {010} [661,684,689,692,693,696–705] and {110} [705,706] and high-index facets ({103}, {105}, {107}, {201}, {401}, {301}, and {106}) [683,700,707–709] has been realized. For rutile crystals the {110} [710–717], {011} [718–720], {001} [718,721] and {111} [351,720,722–725] facets have been grown [49]. Among these different synthesis methods, the hydrothermal and solvothermal methods of wet chemistry have been most extensively used to manipulate the nucleation and growth behaviour of crystals in a given environment. It has been shown experimentally and theoretically that the selective adsorption of appropriate capping agents (organic molecules, inorganic ions, or their mixtures) allows there to be a substantial decrease in the surface energies of different surfaces [41,44,49,209,726–732]. This consequently leads to controlled growth rates along different orientations and, therefore, to the formation of targeted-shaped crystals with tunable percentages of high reactive facets [49]. The theoretical basis on which the appropriate capping agents are chosen is related to the change of the surface energy of a facet before and after the adsorption of capping agents [49]. The equilibrium Wulff shapes obtained for the simulations of anatase [38] and rutile [39], as shown in Figure 48a,b (left panel), respectively, were calculated for vacuum conditions at absolute zero temperature.