Percolation mechanism

Measurement of adsorption/desorption, percolation, mechanical stability and adhesion characteristics of active carbons prepared in ordinary laboratory conditions and then the application of models of steady-state systems with random fluxes to the complexes of measured parameters. 

As with VT, identifying conduction pathways with bond valence maps provides accurate predictions for ionic conductors (both crystalline and amorphous) with a percolation mechanism of conductivity, but is less successful when modeling proton conductors. 

From their findings they concluded that for tosylate-doped thick PPy films, transport of small cations is very fast and is responsible for PPy reduction and delamination. This cationic transport in the film follows a percolation mechanism and, according to their view, good protection requires optimization of the percolation length, i.e. not too high a polymer conductivity, which implies an extended percolation system, but a percolation... 

Shklovskii, B.I. 1972. Percolation mechanism of electrical conduction in strong electric fields. Fiz Tekh Poluprovodn (Leningrad) 6 2335 [Sov Phys Semicond 6 1964, 1973]. 

Mohamed et al. [149] evaluated the use of several types of sulfosuccinate anionic surfactants in the dispersion of MWCNTs in NR latex matrices. Sodium l,5-dioxo-l,5-bis(3-phenylpropoxy)-3-((3-phenylpropoxy)carbonyl) pentane-2-sul-fonate showed the best dispersion capabihty and improved the electrical conductivity of the resulted composites. These results have significant implications in the development of new materials for aerospace applications because the filler s dispersiou directly influences the properties of the final material. Jo et al. [150] obtained pristine MWCNt-Ti02 nanoparticles filled with NR-CllR and epoxidized NR-CUR, concluding that the second blend proved higher thermal conductivity because the epoxy branches in ENR and the functionalized MWCNT form a stronger network. Conductivity in CNTs reinforced with rubber-based blends can be improved when reaching a critical concentration of the filler known as the percolation threshold, when a continuous network structure is formed. Thankappan Nair et al. [151] discussed the percolation mechanism in MWCNT-polypropylene-NR blends. 

There are two distinguishable mechanisms of the electrical conduction in such heterogeneous mixtures. One is the percolation mechanism, and the other is the electron tunneling mechanism. 

Rong MZ, Zhang MQ, Zheng YX, Zeng HM, Friedrich K (2001) Improvement of tensile properties of nano-Si02/PP composites in relation to percolation mechanism. Polymer 42 (7) 3301-3304... 

IS measurements have been performed in the 253-333 K temperature range and the results from the measurement at 293 K are shown in Figure 3-43. The Argand diagram consists of two semidrcles which can be understood and represented by a best fit of the data to an ideal Debye resistance (/ 2)/capadtance (C2) parallel link (lower frequency process 2) in series with an additional Cole-Cole resistance (Ri)/CPE (constant phase element) parallel link (higher frequency process 1). From the fit data, a Cole-Cole parameter a = 2/3 results which is very typical for percolation mechanisms. The Ohmic part is the same for both processes Ri = and so = 2/ ,. The spedfic conductivity processes have Oi = 02 = 3.23 X 10 Q" m at 293 K. Since both processes are thermally... 

One recent development in the static immersion testing from Newman et al. [116] originated with Bengough and May [JJ5]. Recent experimentation [116] involved exposing samples of alpha-brass in NaCl solutions with additions to simulate the local environment in crevices or otherwise inhibited transport. Under these severe conditions, dealloying can be shown to occur without an applied potential and may be reduced or eliminated by addition of arsenic to the alloy. The authors suggest that these results support the percolation mechanism with surface diffusion for dealloying rather than mechanisms that rely on formation of metastable phases or disproportionation of the less noble element. 

Enhanced barrier performance is provided by montmorillonite as the polymer is degraded. The concentration of montmorillonite increases as a function of the degradation of the polymer. This provides added barrier protection. The polymer is in a melt form when thermal degradation occurs. Evaluations of the surface of the polymer-clay nanocomposite samples as a function of thermal degradation indicate that the montmorillonite is concentrated further by a percolation mechanism, presumably by the gas escaping from the sample and forcing the montmorillonite particles to the surface [2], Analysis of the change in montmorillonite concentration as a function of temperature for polypropylene-clay nanocomposites supports this mechanism [30]. 

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