Electrical conductivity concentration dependence

The electrical conduction process depends on several parameters, mainly on filler concentration. But filler morphology such as particle size and structure as well as filler-filler and filler-matrix interactions which determine the state of dispersion and filler orientation are key factors in determining the electrical properties. On the other hand, processing techniques also influence the electrical conductivity of... 

A question that some students ask is why, while water is not an electrical conductor, it is dangerous to expose damp hands or in general a damp body, to mains electricity, for example in a bathroom. The explanation is that dry skin has a resistance of 100 000 ohms or more, while wet skin may have a resistance of only 1000 ohms. Such a low resistance of the wet skin allows current to pass into the body more easily and give a greater electric shock. Note also that pure water should be contrasted with natural water (such as tap water), which has various substances dissolved in it, among which are electrolytes. Hence natural water has some electric conductivity, which depends on the concentration of the water in various electrolytes. Electrical conductivity measurements of natural waters are used to predict the salinity, major solute concentrations, and total dissolved solids concentrations of natural waters. 

Although the fluid electrical conductivity (Aq) depends on the electrolyte concentration and the surface charge density [2, 10] and the surface conductivity (2 ) may vary with the channel size... 

In recent years metallic particles have also been considered as fillers to increase the electrical and thermal conductivities of epoxy systems. The electrical and thermal conductivities of epoxy systems filled with metal (i.e. copper and nickel) powders have been studied (Mamunya et al., 2002). In this work it was shown that the composite preparation conditions allow the formation of a random distribution of metallic particles in the polymer matrix. The percolation theory equation holds true for systems with a random distribution of dispersed filler, while in contrast to the electrical conductivity, the dependence of thermal conductivity on concentration shows no jump in the percolation threshold region. 

Notice from eqs. (10.45) and (10.46) that the electric conductivity principally depends on the ionic concentration, but Oi = f (Ci,Di,T) and ty% = f Also, Ui is a macroscopicaUy measurable in terms of microscopic parameters [8]. Assume that the conductivity obeys the Arrhenius relationship so that... 

The electrical conductivity of conjugated potymers is strongly influenced by the presence of doping agents and can be varied several orders of magnitude by changing the dopant concentration [135]. Further, the electrical conductivity also depends on the specific dopant. For these reasons, the discussion of the electrical properties is divided into two parts. The first part corresponds to intrinsic conduction (pristine form) and the second is devoted to doped polymers. 

A., Brezesinski, T., Djerdj, 1., Wark, M., and Niederberger, M. (2006) Nonaqueous synthesis of uniform indium tin oxide nanocrystals and their electrical conductivity in dependence of the tin oxide concentration. Chem, Mater,... 

The reaction rate is increased by using an entraining agent such as hexane, benzene, toluene, or cyclohexane, depending on the reactant alcohol, to remove the water formed. The concentration of water in the reaction medium can be measured, either by means of the Kad-Eischer reagent, or automatically by specific conductance and used as a control of the rate. The specific electrical conductance of acetic acid containing small amounts of water is given in Table 6. 

The electrical conductivity in the solid state is determined by the product of the carrier concentration and the carrier mobility. In conjugated polymers both entities are material dependent and, i.e., are different for electrons and holes. Electrons or holes placed on a conjugated polymer lead to a relaxation of the surrounding lattice, forming so-called polarons which can be positive or negative. Therefore, the conductivity, o, is the sum of both the conductivity of positive (P+) and negative polarons (P ) ... 

The temperature dependence of electrical conductivity has been used [365] to distinguish between the possible structural modifications of the Mn02 yielded by the thermal decomposition of KMn04. In studies involving additives, it is possible to investigate solid-solution formation, since plots of electrical conductivity against concentration of additive have a characteristic V-shape [366]. 

Above a critical hller concentration, the percolation threshold, the properties of the reinforced rubber material change drastically, because a hller-hUer network is estabhshed. This results, for example, in an overproportional increase of electrical conductivity of a carbon black-hUed compound. The continuous disruption and restorahon of this hller network upon deformation is well visible in the so-called Payne effect [20,21], as represented in Figure 29.5. It illustrates the strain-dependence of the modulus and the strain-independent contributions to the complex shear or tensUe moduli for carbon black-hlled compounds and sUica-hUed compounds. 

We outline experimental results and provide theoretical interpretation of effect of adsorption of molecular oxygen and alkyl radicals in condensed media (water, proton-donor and aproton solvents) having different values of dielectric constant on electric conductivity of sensors. We have established that above parameter substantially affects the reversible changes of electric conductivity of a sensor in above media which are rigorously dependent on concentration of dissolved oxygen. 

Derivation of simple and unambiguous quantitative relations between the signal amplitude of a sensor, i.e., the value of the change of electric conductivity, work function, etc. and concentration of detected traces of admixture in the medium under study is also important for successful development of the sensor measuring technique. Theoretical considerations given in this book show that such relations exist in most simple form. The purpose of experiment consists in statistical substantiation that these dependencies rigorously hold at proper conditions. 

Commenting on above we should mention that initial expressions (1.59) - (1.63) are valid for disordered systems with exponentially broad spectrum of local values of electric conductivity. Due to existing dependence of 0 on over long times in our case the broad preadsorption spread in can grow narrow. At specific ratios between parameters of the absorbate-adsorbent system it can either vanish at all or there is a notable concentration of leveled-off barriers being formed with the fraction higher than the threshold one Xe- The straightforward analysis of each specific case characterized by a certain relationships between parameters of the system enables one easily obtain conditions... 

As for equilibrium values of as and P they are mainly dependent on relations between such parameters of the systems as initial electric conductivity of adsorbent, concentration of chemisorbed particles, reciprocal position of the energy levels of absorbate and adsorbent. Thus, during acceptor adsorption in case of small concentration of adsorption particles one can use (1.82) and (1.84) to arrive to expressions for equilibrium values of ohmic electric conductivity and the tangent of inclination angle of VAC ... 

Fig. 1.14. The qualitative profile of dependencies of equilibrium values of electric conductivity (curve /) and the tangent of inclination angle of VAC Ps (curves 2, 3) as a function of concentration of chemisorbed acceptors 2 - Inoj) 4co > a/2 3 - Inob co < o/2...

We used polycrystalline films of ZnO and Sn02 as adsorbents. The films were deposited from the water suspension of respective oxides on quartz substrates. These substrates contained initially sintered contacts made of platinum paste. The gap between contacts was of about lO" cm. All samples were initially heated in air during one hour at T 500 C. We used purified molecular oxygen an acceptor particle gas. H and Zn atoms as well as molecules of CO were used as donor particles. We monitored both the kinetics of the change of ohmic electric conductivity and the tangent of inclination angle of pre-relaxation VAC caused by adsorption of above gases and the dependence of stationary values of characteristics in question as functions of concentrations of active particles. 

The results mentioned together with data outlined in Section 1.11 indicate that adsorption induced change in electric conductivity of sintered and partially reduced oxide is mostly dependent on adsorption related change in concentration of stoichiometric metal atoms which are responsible for dope electric conductivity rather than by charging of the surface of adsorbent due to transformation of radicals of O2 and O". 

The kinetic equation describing the change in concentration of conductivity electrons and consequently the time dependence of electric conductivity has the following shape... 

The regular availability of linear dependence between above values enabled us to substantiate two methods of detection the stationary and the kinetic one. The very names of these methods indicate that the first one makes it feasible to use the stationary values of adsorption-induced changes in electric conductivity of adsorbent to judge concentration of the particles detected. The second method enables one to obtain the same information using the measurements of initial kinetics of the change of electric conductivity. 

The dependence of the initial velocity of changes in the electrical conductivity of Au/ZnO being acted upon by He on the surface concentration of Au (curve 2) also has its clear maximum at some point of 2 10 atoms/cm. The fact that peaks of curves / and 2 are abscissaspaced apart almost an order of magnitude engages our attention, i.e. we see that there is no direct correlation between the secondary emission currents and the sensitivity of Au/ZnO film to metastable atoms. 

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