Electrical conductivity Percolation

Low-frequency conductivity data [37] obtained along this 45°C isotherm are illustrated in Fig 2. The initial oscillatory variation in the conductivity for a > 0.9 can be assigned to variations in AOT partitioning among dimers and other low aggregates and reverse micelles, as reverse micelles are nucleated by added water (brine). These variations will be discussed in greater detail in another publication. The key behavior for the purposes of this exposition is the onset of the electrical conductivity percolation at a = 0.85. The conductivity increases two orders as a decreases from 0.85 to 0.70, and as shown in the inset, the conductivity increases another two orders as a a decreases from 0.7 to 0.3. 

Water proton self-diffusion exhibits a break point and begins to increase at a = 0.85. In the case of AOT self-diffusion, a breakpoint also occurs, but AOT self-diffusion continues to slow as a decreases further. These breakpoints in both water and AOT selfdiffusion behavior at a = 0.85 coincide with the breakpoint in electrical conductivity illustrated in Fig. 1, where the onset of electrical conductivity percolation occurs. At a = 0.7 two more breakpoints in the water proton and AOT self-diffusion are seen. Water proton self-diffusion increases more markedly and AOT self-diffusion beings to increase markedly. 

Yuen et al. 2008 (43) MWCNT CVD CNT Company, Incheon, Korea As-received In situ method Ex situ method CNT Loading levels 0.25 to 4.76 wt% Film Bulk Film Bulk Electrical Conductivity Percolation threshold 0.25 wt% for in situ prepared composites Percolation threshold 0.74 wt% for ex situ prepared composites EMI SE (2-18 GHz) 32.06 dB at 2.18 GHz for bulk composite prepared by in situ method 58.73 dB at 14.84 GHz for 10 layers of stacked composite film prepared by in situ method Higher EMI shielding effectiveness of layered composite attributed to energy loss by multi-reflections in the layered composites... 

Reasonably low electrical conductivity percolation threshold, i.e., 6.0 wt%/5.4 volume % of PANI.DBSA content can evidently be achieved here (with value oit = 3.6 and R = 0.99 for blends based on NBR 48 ACN wt%). 

PCL/PLA 70/30 MWCNT and carboxylic MWCNT PCL phase and interface Unfunctionalized MWCNT is located exclusively in the PCL phase, while carboxylic MWCNT is located in the PCL phase and at the interface. The reinforcing and compatibilization effect of nanotubes results in a higher improvement in electrical conductivity and mechanical properties compared to pure blend. Improved phase stability and lower rheological and electrical conductivity percolation threshold were observed Wu et al. 2009... 

In addition to percolation in reverse microemulsions being driven by field variables such as (disperse phase) volume fraction, temperature, and salinity, cosurfactant concentration appears also to suffice. Low-frequency electrical conductivity for the aqueous acrylamide-AOT-tol-uene reverse microemulsion system is illustrated in Fig. 6 [42]. The cosurfactant concentration = 1-2% (w/w) is annotated with the arrow (Op) in Fig. 6 and corresponds to the approximate onset of electrical conductivity percolation. The percolation threshold in conductivity occurs at ip = 3.09%. 

Critical behavior of, and electrical conductivity percolation in, microemulsions is much dependent on the dynamics of stick/ collisions between droplets of oil (water) present in oil-in-water (water-in-oil) microemulsions (see Chapter 5). Sticky collisions refer to collisions that bring assembly cores into contact. During the time of contact matter may be transferred from one assembly to another. Such collisions occur in systems with strong attractive interactions between assemblies. 

PANI-CSA PMMA Electrical conductivity percolation occurs at 0.04-0.07 wt% mechanical percolation appears to be at 1 wt% 1104... 

Electrical conductivity in nanotube-polymer composites exhibits percolation-type behavior, where the presence of interconnected nanotube network results in a dramatic increase of the electrical conductivity. Physical parameters of composite materials such as electrical conductivity, percolation threshold v ), and critical exponent (t) have been intensively studied to achieve polymer-CNT conductive composites at low filler concentrations. However, as already mentioned, numerous studies show that the percolation threshold and conductivity depend strongly on the polymer type and synthesis method, aspect ratio of CNTs, disentanglement of CNT agglomerates, uniform spatial distribution of individual CNTs, and degree of alignment. 

---