Layered-type structure

Crystal chemistry ofTa and Nb fluorides - Compounds with layered-type structures... 

A further decrease in the X Me ratio, to 4, leads to linkage of the octahedral units by sharing more than one ligand so as to achieve coordination saturation. Sharing of two vertexes (two comers of the each octahedron) leads to the formation of compounds with layered-type structures. 

Layered-type structure, 92-100 Lewis acidity, 15 Liquid - liquid extraction collective, 276-277 counter-current scheme, 272 equipment, 273 extractants, 279-281 mechanism, 274-276 multistage counter-current, 271 multistage cross-current, 270 one-stage process, 270 principals, 267-269 process performance, 282-283 process schemes, 277,278, selective, 277-278 with 2-octanol, 284-291... 

The layer-type structures and chemical nature of the constituents of the bismuth and thallium-based cuprate superconductors - notably the lone-pair stereochemistry of Bis+, variable valence of copper, and considerable exchange among some of the cation sites - combine to make structural non-ideality, nonstoichiometry, and phase intergrowth the rule rather that the exception in these families of materials. These features, as well as the probable metastability of the phases (and possibly all high-temperature oxide superconductors), also contribute to the difficulties typically encountered in preparing single-phase samples with reproducible properties and compositions. 

In this work, we have focused on strong surface preference with only mutual transition between the symmetrical and asymmetrical layer-type structures. SSL theory and MC simulation are further applied to investigate the self-assembled morphology of diblock copolymers confined in the nanopore. MC simulation shows that the Niayer of the concentric cylinder barrel changes with respect to the extent of frustration between the exterior radius Rex and the bulk lamellar period L0. Simultaneously, the predictions of SSL theory also show that both... 

A novel class of crystalline, microporous aluminophosphate phases has been discovered. It represents the first class of molecular sieves with framework oxide compositions free of silica. The new class of materials encompasses some fourteen reported three-dimensional microporous framework structures, and six two-dimensional layer-type structures. The three-dimensional structures include structural analogues of the zeolites sodalite and erionite-offre-tite. The novel phases can be synthesized hydro-thermally in the presence of organic amines and quaternary ammonium templates. The template is entrapped or clathrated within the crystallizing aluminophosphate network. After thermal decomposition of the template the three-dimensional molecular sieves have the general composition of Al303 1.0 ... 

Crystal chemistry qfTa and Nb fluorides—Compounds with layered-type structures 97... 

Such layer type structures are present in mica, (OH)2KMg3(AlSi3Oj0) and talcum, (OH)2Mg3(Si4Oi0) which are characterized by the ease in which they split into layers. 

The advance of a reaction interface, once established, into regions of almost perfect crystal, in preference to the appearance of new centres of decomposition in the bulk material, indicates that the reaction contributes to fiuther decomposition by generating conditions that were not present originally. This is a form of autocatalysis. The crystal structure may, however, influence the direction and rate of advance, e g. along layers in layer-type structures. Distortion of the structure adjacent to the reaction zone may lead to destabilization, or reaction may produce surfaces which act as a catalyst for further reaction, e.g. the particles of metal product formed during decompositions of metal carboxylates [18,59,73 and Chapter 16] provide active surfaces for anion breakdown. If a decomposition takes place in several stages, the stability of an intermediate may determine the overall reaction rate [22,79]. 

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