Conduction plane increase

The incorporation of nanocarbons in hierarchical composites can also result in large improvements in their electrical conductivity, and to a lesser extent in their thermal conductivity. For ceramic fibers both in-plane and out-of-plane electrical conductivities are increased by several orders of magnitude [41], whereas for CF the improvement is significant only perpendicular to the fiber direction due to the already high conductivity of the fiber itself [46]. The out-of-plane electrical conductivity of CNT/CF/epoxy composites is approaching the requirements for lightning strike protection in aerospace composites, thought to be around 1 10 S/m. Yet further improvements are required, as well as the evaluation of other composite properties relevant for this application, such as maximum current density and thermal conductivity. 

The onset of high electrical conductivity with increasing volume fraction of metallic particles has also been of interest in relation to theoretical treatments which consider the factors which control formation of a continuous disperse phase of randomly distributed particles. In pursuance of such work, the distribution of metallic particles was studied experimentally by quantitative microscopy of polished plane sections. A marked increase in conductivity was observed when the fractional volume loading of silver particles in Bakelite reached 0.36-0.38 ( 3). 

Figure 3 presents the variation of the electrophoretic mobility with the dimensionless distance X when a sphere moves perpendicularly towards a conducting plane. The solid line represents the results from the bipolar coordinate method and the dash curve is the approximate results from the reflection method. A good agreement between the results from the both methods is attained. The electrophoretic velocity of the sphere decreases monotonically with increasing X and is expected to vanish as the particle... 

The conducting ions, such as Na, populate the planes between the spinel blocks. For optimum two-dimensional ion conduction in these planes, it is preferable that not all the available sites be occupied by the mobile cations. As the temperatures increases, the mobile ions in these conducting planes become disordered and occupy positions at random. The ionic mobility of the Na in these planes is higher in the /J structure than it is in the / " structure because of the particular configuration of the bridging oxygen ions that act as obstacles to ionic motion within the plane. Na ion conduction is anisotropic and two-dimensional within these conduction planes for both the p and structures. No ionic conduction exists in a direction perpendicular to the conduction plane. 

A macrocyclic resorcin[4]arene with four hydrophobic substituents in the axial position provides an ion-conducting molecular pore by tail-to-tail dimerization.Because the pore size and characteristics of the entry way are defined explicitly by the molecule, only one conductance level is observed. The relatively simple structure is amenable to systematic structural modifications and is, therefore, appropriate in establishing the structure-function relationships. When a methyl ether derivative of cholic acid was employed as the axial substituent,the conductance was increased by 50% to 9.9 pS, compared with the value 6.1 pS observed for 1 with simple alkyl substituents. The cation and anion selectivity ratio Pk/Pc was 20 for 2. showing a significantly larger selectivity factor compared to 8 for 1. A hydrophilic molecular plane of methoxy substituents certainly contributes to the increase of conductance and a higher cation and anion selectivity by the arrangement of a more hydrophilic environment at the central pore. Both ion channels exhibited moderate preferences compared to Na by a facior of ca. 3. The aromatic moiety provides a weak electric field... 

As expected from their structures, the elements are poor conductors of electricity solid F2 and CI2 have negligible conductivity and Br2 has a value of 5 X 10 ohm cm just below the mp. Iodine single crystals at room temperature have a conductivity of 5 x 10 ohm cm perpendicular to the be layer plane but this increases to 1.7 x 10 ohm cm" within this plane indeed, the element is a two-dimensional semiconductor with a band gap g 1.3eV (125kJmol" ). Even more remarkably, when crystals of iodine are compressed they become metallic, and at 350kbar have a conductivity of 10" ohm" cm", The metallic nature of the conductivity is confirmed by its negative temperature coefficient. 

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