Partial electrical conductivity

The proportionality constant between the current and the electrochemical potential gradient is controlled by the partial electrical conductivity [Pg.546]

Electrical Conductivity. In order to conduct electricity, the working fluid must contain charged particles, ie, it must be partially ionised. 

Any property of a reacting system that changes regularly as the reaction proceeds can be formulated as a rate equation which should be convertible to the fundamental form in terms of concentration, Eq. (7-4). Examples are the rates of change of electrical conductivity, of pH, or of optical rotation. The most common other variables are partial pressure p and mole fraction Ni. The relations between these units... 

One feature of oxides is drat, like all substances, they contain point defects which are most usually found on the cation lattice as interstitial ions, vacancies or ions with a higher charge than dre bulk of the cations, refened to as positive holes because their effect of oxygen partial pressure on dre electrical conductivity is dre opposite of that on free electron conductivity. The interstitial ions are usually considered to have a lower valency than the normal lattice ions, e.g. Zn+ interstitial ions in the zinc oxide ZnO structure. 

A relatively high degree of corrosion arises from microbial reduction of sulfates in anaerobic soils [20]. Here an anodic partial reaction is stimulated and the formation of electrically conductive iron sulfide deposits also favors the cathodic partial reaction. 

If there is more than one type of carrier, i.e. electrons and positive holes, as in MWCNT, the contribution of each type of carrier should be taken into account. In that case, the total electrical conductivity is given by the sum of the partial conductivities. 

HC1 in ethyl alcohol causes a marked drop in the electrical conductivity, which is ascribed to the partial suppression of proton jumps resulting from the capture of protons from the (C2H5OH2)+ ions, thus ... 

Graphite bisulfates are formed by heating graphite with a mixture of sulfuric and nitric acids. In the reaction, the graphite planes are partially oxidized. There is approximately one positive charge for every 24 carbon atoms, and the HS04 anions are distributed between the planes, (a) What effect is this oxidation likely to have on the electrical conductivity (b) What effect would you expect it to have on the x-ray diffraction pattern observed for this material Refer to Major Technique 3 on x-ray diffraction, which follows this set of exercises. 

An interface between two immiscible electrolyte solutions (ITIES) is formed between two liqnid solvents of a low mutual miscibility (typically, <1% by weight), each containing an electrolyte. One of these solvents is usually water and the other one is a polar organic solvent of a moderate or high relative dielectric constant (permittivity). The latter requirement is a condition for at least partial dissociation of dissolved electrolyte(s) into ions, which thus can ensure the electric conductivity of the liquid phase. A list of the solvents commonly used in electrochemical measurements at ITIES is given in Table 32.1. 

The latter conclusion is reliably confirmed by experimental results [40] in which the studies of effect of the structure on the character of adsorption change in electric conductivity of monocrystal or partially reduced polycrystalline ZnO adsorbents were conducted. The comparative studies of the character and the value of response of electric conductivity in both types of adsorbents on adsorption of various atoms and molecular particles led the authors to conclusion on identical origin of both the mechanisms of electric conductivity and mechanisms of its adsorption induced change. 

Nevertheless, there is a whole series of experimental results enabling one to propose and substantiate a sufficiently general model consistently describing the effect of oxygen adsorption on electric conductivity of partially reduced oxides observed in experiments. Let us con sider these data. 

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". 

In our view the final verification was given to this conclusion in paper [66] in which simultaneous O2 adsorption on partially reduced ZnO and resultant change in electric conductivity was studied. It was established in this paper that the energies of activation of chemisorption and that of the change of electric conductivity fully coincide. The latter is plausible only in case when localization of free electron on SS is not linked with penetration through the surface energy barrier which is inherent to the model of the surface-adjacent depleted layer. 

On the basis of consideration of this model one can easily obtain expressions describing kinetics of the change in electric conductivity of sintered partially reduced oxide adsorbent during development of direct and inverse reaction described by expression (2.17). The consumption of superstoichiometric metal atoms which takes place during adsorption of O2 is described by equation... 

As it was mentioned in paper [48], expressions (2.44) and (2.45) perfectly describe experimental situation with kinetics of tiie change of electric conductivity of sintered and partially reduced ZnO film during adsorption and desorption of molecular oxygen. Expression (2.44) describes the kinetics of the change of a during adsorption of O2 on ZnO with the surface rich in donors due to photolytic decomposition of ZnO in vacuum fairly well [74]. 

---