Intercrystalline amorphous phase

The establishment of phase diagrams for polymer electrolyte systems where the stable regions of the various crystalline phases and the intercrystalline amorphous phase are defined, determining the relationship between these and their characterisation as a function of temperature and composition of the electrolyte, is therefore extremely useful, e.g. in predicting the ionic conduction behaviour of electrolytes. These phase diagram studies were initiated because ionic conductivity studies showed considerable variations as a function of several experimental parameters, such as thermal history." ... 

Usually, the thicknesses of the lamellar polymer crystals and intercrystalline amorphous zones do not exceed a few tens of nanometers. Semicrystalline polymers are in fact Nature s nanocomposites self-assembled nanocomposite materials in which a combination of crystals and rubbery amorphous phase may coexist, resulting in the remarkable ductility and toughness of these materials. Another consequence of the relatively small thickness of polymer crystals and the high surface energy of their basal surfaces is a strong dependence of melting temperature on the crystal thickness. 

The lack of methods for a fast and reliable assessment of membrane quality is still one of the outstanding issues in zeolite-membrane development. The usual meaning of the term quality relates to the ability of the membrane to carry out a given separation with a reasonable flux therefore, a system-specific property and a universal membrane quality test do not exist. In general, specihc permeation measurements at different temperatures, either of single gases (or vapors) or of multicomponent mixtures in the gas or liquid (pervaporation) phase, provide extremely useful information on the effective pore structure of the membrane, on the existence of intercrystalline defects, and amorphous material and permeation fluxes, as well as information about the main transport controlling effect (adsorption or diffusion). 

Figure 8.4 (a) Schematic diagram of an oriented polymer consisting of an amorphous region (A), intercrystalline bridges (B), crystalline blocks (C) and tie molecules (TM) with volume fractions a -h b H- t = 1. (b) Parallel combination of two phases, (c) Phases TM and S after removal of constraint. 

It is evident that the aluminum released from the framework upon hydro-thermal treatment remains in the sample, either as an intracrystalHne oxidic or cationic aluminum species or as intercrystalline material, i.e., as a separate crystalline or amorphous aluminum oxide phase [77-79]. Typical signals appear in the Al MAS NMR spectra of Y zeolites upon hydrothermal dealumination (Fig. 4). A line at 0 ppm associated with octahedrally coordinated aluminum is indicative of hydrated cationic species [79-82]. Amorphous oxidic aluminum species, which are subject to large second-order quadrupolar... 

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