Clustering ionic

As in other ionomers, the ion exchange sites in "Nafion" membranes are observed to aggregate and form clusters. Ionic clustering in "Nafion" membranes has been indicated by a variety of physical studies including dielectric relaxation (1), small angle x-ray scattering (1-4), neutron scattering (4), electron micro-... 

It is noteworthy that besides highly dispersed palladium clusters, ionic Pd was also detected by ESR in Pd/Li-AbOa catalysts prepared by anchoring PdCb onto alumina modified with butyl lithium. These catalysts were highly active and selective in the hydrodechlorination of substituted aromatic compounds. The coexistence of Pd and Pd° in the Pd/Li-AbOa catalysts suggests the possible formation of mixed metal ion - metal nanocluster ensemble sites. 

The encaged clusters considered in this chapter are almost exclusively metal carbonyls and metals (including bimetallics). llte encaged metal carbonyls that have been most investigated include [Rh (CO)i6], [Ir4(CO)i2], and the isomers of [Ir (CO),d the crystal structures of the iridium clusters are shown in Figure 4-6. Some of the most thoroughly characterized encaged metal dusters have been made from these metal carbonyls. Brief mention is made of metal oxide and also nonmetal clusters ionic dusters are scarcely considered. Synthesis, characterization, reactivity, and catalytic and other properties are considered for these materials. 

EPR metal carbonyl clusters ionic clusters structure and environment of duster in zeolite Useful for diaraderization of spe-des having unpaired electrons due to its high sensitivity, very small percentages of total metal loading are measurable. 

X-ray diffraction metal carbonyl clusters ionic clusters metal clusters structure of duster Strudural information (bond lengths and coordination numbers around a given metal atom) based on radial eledron distribution from X-ray data RED gives only metal-metiil, not metal-support or metal-adsorbate contributions. 

Small-angle neutron scattering gave peaks which corresponded to crystalline CFj groups and to structures containing clustered ionic groups with assodated water molecules. The crystalline peaks disappeared in samples quenched from the melt. The number of water molecules per ionic group was deduced from the scattered intensity and rose from 1.7 in room-temperature-dried samples to 20 in boiled samples. 

Figure 1. Schematic representation of the physical network structure of TPEs of the segmented copolymer type. Knots in block copolymers (i) amorphous domains (phase segregation) (ii) crystalline domains (crystallization) - lamellae (folded chain block) and micelles (fringed micelle) (iii) ionic aggregates, clusters (ionic bonding) the rectangular...

A gas phase ionic cluster can be described as a core ion solvated by one or more neutral atoms or molecules... 

Ayotte P, Bailey C G, Weddle G FI and Johnson M A 1998 Vibrational spectroscopy of small Br (Fl20) and I Fl20) clusters infrared characterization of the ionic hydrogen bond J. Phys. Chem. A 102 3067-71... 

Pisani [169] has used the density of states from periodic FIP (see B3.2.2.4) slab calculations to describe the host in which the cluster is embedded, where the applications have been primarily to ionic crystals such as LiE. The original calculation to derive the external Coulomb and exchange fields is usually done on a finite cluster and at a low level of ab initio theory (typically minimum basis set FIP, one electron only per atom treated explicitly). 

After being formed as a spray, many of the droplets contain some excess positive (or negative) electric charge. Solvent (S) evaporates from the droplets to form smaller ones until, eventually, ions (MH+, SH+) from the sample M and solvent begins to evaporate to leave even smaller drops and clusters (S H+ n = I, 2, 3, etc,). Later, collisions between ions and molecules (Cl) leave [M + H]" ions, which proceed on into the mass analyzer. Ion yield can be enhanced by including a volatile ionic compound (e.g., ammonium acetate) in the initial solution before it reaches the spraying zone. 

The carbon black in semiconductive shields is composed of complex aggregates (clusters) that are grape-like stmctures of very small primary particles in the 10 to 70 nanometer size range (see Carbon, carbon black). The optimum concentration of carbon black is a compromise between conductivity and processibiUty and can vary from about 30 to 60 parts per hundred of polymer (phr) depending on the black. If the black concentration is higher than 60 phr for most blacks, the compound is no longer easily extmded into a thin continuous layer on the cable and its physical properties are sacrificed. Ionic contaminants in carbon black may produce tree channels in the insulation close to the conductor shield. 

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