Ion-conducting properties

In the sol-gel procedure for the preparation of hybrids, polymeric acid catalysts such as poly (styrene sulfonic acid) were also used instead of hydrogen chloride [14]. The polymeric acid catalyst was effective for the preparation of hybrids at a similar level to that of hydrogen chloride catalyst. In some cases, the increased modulus was observed due to the higher extent of reaction. No difference was observed in morphologies between the hybrids prepared with polymeric and small molecule acid catalysts. The method using polymeric acid catalyst may depress the ion-conductive property, characteristic to the mobile acidic small molecules. Polymeric catalyst may also influence the rheology of the resulting hybrids. 

Ion-conductive properties of anion-trapping-type organoboron polymer electrolytes was evaluated after adding lithium salts (Fig. 3). In these systems, ionic conductivity of 3.05 X 10 s 5.22 X 10 6Scm 1 was observed at 50°C. This indicates... 

A variety of organoboron polymer electrolytes were successfully prepared by hydroboration polymerization or dehydrocoupling polymerization. Investigations of the ion conductive properties of these polymers are summarized in Table 7. From this systematic study using defined organoboron polymers, it was clearly demonstrated that incorporation of organoboron anion receptors or lithium borate structures are fruitful approaches to improve the lithium transference number of an ion conductive matrix. 

Table 1 Ion-Conductive Properties of Organoboron Polymer Electrolytes ...

We have also investigated the ion conductive properties ofa series of neutralized ILs, prepared by neutralization of amines with equimolar amounts of Bransted... 

Some ion conductive properties of lithium salt/ IL solutions are summarized in Table 3.17. Generally, the ionic conductivity of ILs containing lithium salts are lower than those of pure ILs, even though the addition of lithium salt increases the net number of ions in the system, due to smaller formula weight of lithium. According to the literature, the major reason for these phenomena may be the increase in viscosity and Tg (some specific values are shown in Table 3.17). The aggregation oflithium ions in ILs, which causes the decrease in the effective carrier ion number, might be another reason for the decrease in ionic conductivity. 

The fast, ion conduction properties of a-Agl is a result of the large anionic radius of I- and the low cationic radius of Ag+, immersed in a cubic structure containing 42 vacant sites between octahedral and tetrahedral sites. Because of this fact, Ag+ has a high mobility in this cubic structure [22],... 

On the other hand, the theoretical performance of concentration electrochemical cells, based on perovskite materials with protonic and oxygen ion conduction properties, has been described as well [191]. Besides, a sensor for the detection of oxidizable gases that employs the production of a non-Nemstian electrode potential, using zirconia as the solid electrolyte, has been developed [192],... 

In this chapter we review the development of liquid crystalline materials on the basis of ionic liquids. Self-organization behavior and ion-conductive properties of these anisotropic materials are described. 

In the 20 century, many kind of conducting ion species from monovalent to tetravalent ions have been discovered as well as a large number of host crystal lattices. Although some binary rare earth oxides for solid electrolytes have also been investigated, their ion conducting properties were, unfortunately, not enough except the ceria-based materials. 

For example, a solid polymer electrolyte is a solution of a lithium salt in a PEO matrix the ionic conductivity of such material is due to the mobility of lithium cations and their anions in an electric field. The objective of the electrolyte system is to provide mechanical integrity and ion-conducting properties. PEO is a semicrystalline polymer at room temperature and has an exceptional property to dissolve with high concentration of a wide variety of dopants. 

Our studies of chemically prepared catalyst powders in gas diffiision electrodes have demonstrated that conducting polymer supported catalysts can provide similar current densities to commercial carbon supported catalysts. They indicate that with further optimization, the ion conducting properties of certain polymer support catalysts may allow them to exceed the performance of carbon supported catalysts. However, it is clear that substantial improvements in the stability of the polymer support materials will have to be made before applications in fuel cells can be realized. 

The propensity for oxyethylene groups to interact with interlayer cations has also been used to produce the intercalation of poly(methyl methacrylate) (PMMA) and polyethylene (PE). For example, PEO-PMMA (170) or PEG-PE (171) block copolymers have been intercalated in montmorillonite, resulting in blend nanocomposites with interesting mechanical and ion-conductivity properties. 

Okura, T. Yamashita, K Umegaki, T. (1996). Na -ion conduction properties of glass-ceramic Narpsio in the Y-Sm mixed system. Phosphorus Research Bulletin, 6,237-240. 

Among these phases, there may be mentioned BiWOe ( = 1), SrBi2Nb209 ( = 2), and Bi4Ti30i3 (n = 3). The main functionalities are based on their ferroelectric [25] or ion-conducting properties [26]. 

Althongh the electrolyte of a fuel cell would have been chosen for its ion conducting properties, it will always be able to support very small amounts of electron conduction. The sitnation is akin to minority carrier conduction in semicondnctors. Probably more important in a practical fuel cell is that some fuel will diffuse from the anode through the electrolyte to the cathode. Here, because of the catalyst, it will react directly with the oxygen, producing no current from the ceU. This small amount of wasted fuel that migrates through the electrolyte is known as fuel crossover. 

The NASICON structure is capable of accommodating considerable compositional variation and a large number of related compounds have been studied in order to try an improve the lithium ion conducting properties. There have been two distinct approaches to this. One approach has been to try and reduce the temperature of the structural transition and reduce the barrier to ion mobility and so access a compound that shows fast lithium conductivity under ambient conditions. An alternative strategy is to adjust the number of mobile cations and vacant sites in order to increase the conductivity of the cations in the higher temperature, disordered phase. Both approaches have had considerable success in both illuminating the mechanism for ion motion in the structure and in changing the physical properties towards those of a useful fast ion conductor. 

Lanthanum molybdate, LaiMoiOg, has been reported to exhibit fast oxide ion conducting properties comparable with the conventional zirconia and ceria compositions. This compound presents a different crystal structure from all known oxide electrolytes, and consists of isolated [Mo04] units in a three-dimensional matrix of [LaiO]" " . La2Mo209 undergoes a reversible phase transition from the non-conductive monoclinic a-form to the highly conductive cubic -form at approximately 580 °C. Powder X-ray diffraction (XRD) of the phases a and fl are practically identical, because the structural phase transition a is actually a transition from a static to dynamic distribution of the oxygen defects... 

Good ion conduction property at complicated and changeable surrounding conditions, especially for the parameters of temperature and humidity. A minimum ion conductivity of 10" S/cm at room temperature is necessary. 

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