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Guest ions

Under near-equilibrium conditions the shape of this curve is related to two contributions, the compositional dependence of the configurational entropy of the guest ions, and the contribution to the chemical potential from the electron gas [31]. [Pg.366]

The configurational entropy of the mobile guest ions, assuming random mixing and a concentration x, residing in x° lattice sites of equal energy, is... [Pg.366]

JC° number of lattice sites occupied by mobile guest ions III. 4... [Pg.599]

Williams GR, Khan AI, O Hare D (2005) Mechanistic and Kinetic Studies of Guest Ion Intercalation into Layered Double Hydroxides Using Time-resolved, In-situX-ray Powder Diffraction 119 161-192 de Wolff FA, see Berend K (2003) 104 1-58... [Pg.227]

The concept of electrochemical intercalation/insertion of guest ions into the host material is further used in connection with redox processes in electronically conductive polymers (polyacetylene, polypyrrole, etc., see below). The product of the electrochemical insertion reaction should also be an electrical conductor. The latter condition is sometimes by-passed, in systems where the non-conducting host material (e.g. fluorographite) is finely mixed with a conductive binder. All the mentioned host materials (graphite, oxides, sulphides, polymers, fluorographite) are studied as prospective cathodic materials for Li batteries. [Pg.329]

Active template methodology. In this method, recently explored by Leigh et al. [16, 17], the rotaxane is formed via synthesis of the guest molecule in the presence of the macrocyclic host, where the guest ions or organic molecules play an active template role in promoting rotaxane formation. [Pg.161]

Fig. 7.2 Classification of intercalation compounds (a) host of chains weakly bonded together (b) three-dimensional host with one-dimensional lattice of sites for guest ions (c) layered host (two-dimensional host and two-dimensional lattice of sites) (d) three-dimensional host with three-dimensional lattice of sites. Fig. 7.2 Classification of intercalation compounds (a) host of chains weakly bonded together (b) three-dimensional host with one-dimensional lattice of sites for guest ions (c) layered host (two-dimensional host and two-dimensional lattice of sites) (d) three-dimensional host with three-dimensional lattice of sites.
These hosts consist of chains weakly bonded to one another. One example is a series of compounds of Mo and Se, in which cubes of Mo and Se are arranged in chains, and can accommodate guest ions between the chains (Chevrel and Sergent, 1982). In these compounds, it is possible to remove the intercalated ions and separate the chains in solution (Tarascon et al., 1985). [Pg.169]

Many layered compounds are made of close-packed anions, with transition metals in octahedral or trigonal prismatic sites, as shown in Fig. 7.5. Adjacent layers of anions are only weakly coupled together, and so various sizes of guest ions can be inserted between them. The kinds of site between these layers have already been illustrated in Fig. 7.1. [Pg.170]

Fig. 7.5 Layered structures. Guest ions can intercalate between the X-M-X sandwiches shown at the right. Within the sandwiches, the M atoms are coordinated in trigonal prisms or octahedra by the X atoms. Fig. 7.5 Layered structures. Guest ions can intercalate between the X-M-X sandwiches shown at the right. Within the sandwiches, the M atoms are coordinated in trigonal prisms or octahedra by the X atoms.
Thus measuring the cell voltage at equilibrium vs charge passed between the electrodes is equivalent to measuring the chemical potential as a function of x, the Li content of a compound like Li Mo Seg. Thermodynamics requires that p increase with concentration of guest ions, and so E decreases as ions are added to the positive electrode. [Pg.175]

Fig. 7.10 Voltage E and partial entropy dS/dn in Li MogSes. The theory for dS/dn is for a random distribution of guest ions, with no contribution to the entropy from the electrons. Data from Dahn et al. (1985). Fig. 7.10 Voltage E and partial entropy dS/dn in Li MogSes. The theory for dS/dn is for a random distribution of guest ions, with no contribution to the entropy from the electrons. Data from Dahn et al. (1985).
Experiments were performed with various LiAl-X LDHs, with X = Br, NO3 and ISO4. As with the intercalation process, the nature of the anion exerts a powerful influence on the reaction. In the case of sulfate, the deintercalation reaction does not go to completion - only 40% of the available lithium sulfate was released. The deintercalation reaction initially proceeds very quickly, but the process is then halted. The rate of deintercalation is NOs" > Cl > Br . This series does not correspond with data on the anion selectivity for intercalation into Al(OH)3, which is S04 > Cl" > Br" > NO3". Neither is there a correlation of the release data with the heats of hydration of the anions. The series observed arises because the intercalation and deintercalation processes are a balance of a number of factors, including interactions between the guest ions and the host matrix. [Pg.175]

The measured absolute frequencies for mixed crystals are different from those measured for the pure substance because the isolated guest ion is contained in a lattice with different structural parameters from its own. A step by step frequency change is observable for a progressive series of compounds 213). [Pg.103]

The factors which influence the rate of dissolution of iron oxides are the properties of the overall system (e. g. temperature, UV light), the composition of the solution phase (e.g. pH, redox potential, concentration of acids, reductants and complexing agents) and the properties of the oxide (e. g. specific surface area, stoichiometry, crystal chemistry, crystal habit and presence of defects or guest ions). Models which take all of these factors into account are not available. In general, only the specific surface area, the composition of the solution and in some cases the tendency of ions in solution to form surface complexes are considered. [Pg.298]

The switching efficiency of lumophore-spacer-receptor systems can be improved by using multiple receptor modules. The PET rate is increased in the device when free of guest ions since more than one site can provide the transiting electron. The simplest cases, such as 4, are those where the receptor units are well separated to prevent interdependent ion binding with an interposed lumophore to minimize the lumophore-receptor spacing for maximum PET rates. Besides this statistical effect, receptors may also cooperatively participate in PET. This may be the case in 5 and 6. ... [Pg.6]


See other pages where Guest ions is mentioned: [Pg.48]    [Pg.386]    [Pg.391]    [Pg.599]    [Pg.226]    [Pg.356]    [Pg.202]    [Pg.164]    [Pg.168]    [Pg.181]    [Pg.191]    [Pg.194]    [Pg.195]    [Pg.161]    [Pg.245]    [Pg.16]    [Pg.66]    [Pg.29]    [Pg.32]    [Pg.41]    [Pg.47]    [Pg.49]    [Pg.229]    [Pg.147]    [Pg.5]    [Pg.6]    [Pg.12]    [Pg.17]   
See also in sourсe #XX -- [ Pg.328 ]




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