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Relaxation conductance

The experiments were conducted in a cell (Fig. 4.19) at residual gas pressure of less then 10" Torr kept constant during the measurements. The surface coverage in these experiments was only lO" - 10 %. In this case, after the atomic beam was terminated, relaxation of electric conductivity has not been observed even at elevated temperatures (100 -180 C), when surface mobility of adatoms increased considerably. At larger coverages of the target surface with adatoms, or at higher surface temperatures electric conductivity relaxed to its initial value (before... [Pg.248]

A method of characterising transport mechanisms in solid ionic conductors has been proposed which involves a comparison of a structural relaxation time, t, and a conductivity relaxation time, t . This differentiates between the amorphous glass electrolyte and the amorphous polymer electrolyte, the latter being a very poor conductor below the 7. A decoupling index has been defined where... [Pg.139]

The electrical properties of materials are important for many of the higher technology applications. Measurements can be made using AC and/or DC. The electrical properties are dependent on voltage and frequency. Important electrical properties include dielectric loss, loss factor, dielectric constant, conductivity, relaxation time, induced dipole moment, electrical resistance, power loss, dissipation factor, and electrical breakdown. Electrical properties are related to polymer structure. Most organic polymers are nonconductors, but some are conductors. [Pg.455]

Some examples of conductance relaxation measurements In a solution of tetraalkylammonlum-ealts are given. The results confirm convincingly the applicability of the sphere-ln-contlnuum model as a basic model for Ionic Interactions a complete treatment of Ionic processes can be given from the diffusion of Ions In a continuous medium. [Pg.153]

Conductance relaxation Is also shown to be critically dependent upon aggregation equilibria affecting non-conducting (ion-pairs) as well as Ionic species. The relaxation behavior In the presence of quadrupoles (ion-pair dimers) and triple Ions Is thoroughly analyzed. The experimental results show the potential of the field modulation techniques as a method for the Investigation of ionization processes, independent of conductance measurements. [Pg.153]

Figure 2. Reciprocal conductance relaxation times as a function of the square root of TBAP concentration in media and concentration range where conductance indicates a preponderance of the simple ions. TBAP in diphenyl ether (D— 3,55) at 318 ( ). TBAP in benzene-chlorobenzene (60 40 v/v D = 3, 55) at 298 (A). TBAP in benzene-chlorobenzene (60 40 v/v D = 3, 64) at 298 and 350 atm (2). TBAP in benzene-chlorobenzene (60 40 v/v D = 3, 36) at 323 (0). Figure 2. Reciprocal conductance relaxation times as a function of the square root of TBAP concentration in media and concentration range where conductance indicates a preponderance of the simple ions. TBAP in diphenyl ether (D— 3,55) at 318 ( ). TBAP in benzene-chlorobenzene (60 40 v/v D = 3, 55) at 298 (A). TBAP in benzene-chlorobenzene (60 40 v/v D = 3, 64) at 298 and 350 atm (2). TBAP in benzene-chlorobenzene (60 40 v/v D = 3, 36) at 323 (0).
Figure 3. Dependence of the reciprocal conductance relaxation time on TBA— salt concentration in media and concentration range where conductance indicates an important fraction of triple ions. TBA-bromide in benzene-nitrobenzene (3, 22 vol % D = 2, 90) at 298 ( ). TBA-picrate in benzene-chlorobenzene (16 vol % D = 2, 78) at 298 (0). Figure 3. Dependence of the reciprocal conductance relaxation time on TBA— salt concentration in media and concentration range where conductance indicates an important fraction of triple ions. TBA-bromide in benzene-nitrobenzene (3, 22 vol % D = 2, 90) at 298 ( ). TBA-picrate in benzene-chlorobenzene (16 vol % D = 2, 78) at 298 (0).
As a second example we turn to the analysis of the conductance relaxation observed in tetrabutylammonlun plcrate in benzene-chlorobenzene over the concentration range 0.1—2 x 10 M as shown in Figure 3. A qualitative, but important difference with the previous example is the linear relation between reciprocal relaxation time and total TBAP-concentratlon. [Pg.170]

Since the uncertainty of the numerical values in K3 makes the test of eq. 4b somewhat hazardous, the temperature, and pressure, dependence of the conductance relaxation was investigated. Temperature, and pressure, dependence of intercept and slope of the experimental reciprocal relaxation time vs. concentration is given in Table III. If the reciprocal relaxation time indeed is functionally described by eq. 14 b then we are able to calculate these temperature, and pressure, dependences from previously obtained experimental data. [Pg.172]

The temperature- and pressure-dependence of the conductance relaxation in TBAP solutions in benzene-chlorobenzene (16 vol%) corroborates importantly the description of the phenomena by eq. 14b implying an ionic recombination process between the triple ion and a simple ion. Apparently this picture is still in conflict with conductance data which who the presence of two kinds of triple ions. This discrepancy remains as yet unresolved. [Pg.172]

As for the permeability measurements, most techniques based on the analysis of transient behavior of a mixed conducting material [iii, iv, vii, viii] make it possible to determine the ambipolar diffusion coefficients (- ambipolar conductivity). The transient methods analyze the kinetics of weight relaxation (gravimetry), composition (e.g. coulometric -> titration), or electrical response (e.g. conductivity -> relaxation or potential step techniques) after a definite change in the - chemical potential of a component or/and an -> electrical potential difference between electrodes. In selected cases, the use of blocking electrodes is possible, with the limitations similar to steady-state methods. See also - relaxation techniques. [Pg.155]

Conduction relaxation is determined by the excess charge built up (or rather the capacitance C) and the resistance R over which this charge leaks away. See... [Pg.461]

I. Yasuda and T.J. Hikita, Precise determination of the chemical diffusion coefficient of calcium-doped lanthanum chromites by means of electrical conductivity relaxation, Electrochem. Soc., 141(5) (1995) 1268-1273. [Pg.525]

Figure 6.18. Arrhenius plots of mean conductivity relaxation times r and mean shear relaxation times (r,) for vitreous 0.4Ca(NO3)2 O.6KNO3. Inset shows ratio vs. temperature (Howell et al., 1974). Figure 6.18. Arrhenius plots of mean conductivity relaxation times r and mean shear relaxation times (r,) for vitreous 0.4Ca(NO3)2 O.6KNO3. Inset shows ratio vs. temperature (Howell et al., 1974).
Relaxations in such assumed circuits can proceed through two independent processes known as serial and parallel processes. Macedo et al. (1972) proposed on the basis that impedances (and not admittances) are additive in a series process, use of a dimensionless parameter, A/ = l/e, as appropriate for the analysis of conductivity relaxation. A/, therefore, is also resolved into real and imaginary parts as ... [Pg.267]

Tc is known as the conductivity relaxation time and represents the electric field (E) decay in an ionic glass (assuming the displacement vector to be a constant) and is defined by the relation ... [Pg.267]

Chapter 7. A.C. Conductivity conductivity relaxation times, has a magnitude of... [Pg.269]

Conductivity arises from ionic motions in response to the applied electrical field. The associated field fluctuations affect the nuclear spin relaxations of constituent spin bearing nuclei. Therefore, a direct correlation between the two - nuclear spin relaxation (NSR) and the conductivity relaxations - is to be expected. [Pg.282]

Further, as noted in chapter 6, (FIC glasses) Rt is very high and of the order of lO -lO " since ojc is very high. The decoupling index therefore is directly related to the differences in the behaviour of shear and conductivity relaxation times. Since both shear viscosity and conductivity obey the VTF equation, of the form,... [Pg.295]

Many important reactions, such as the conversion of atmospheric nitrogen and hydrogen into ammonia, are very slow and remain that way tmtil a catalyst (in this case iron oxide) is identified. In our bodies, enzymes can function as catalysts to speed up essential reactions. In order to tmderstand reaction mechanisms, chemists focus on discrete reaction steps and often need very short-term experimental methods to follow rates of individual reaction steps. For instance, Manfred Eigen and Leo De Maeyer (1955) used an electrical conductance relaxation method to measure the rate of the reaction... [Pg.1092]

Figure 4. Estimates of the potassium-conductance relaxation time, rn, from fits of eqs 2, 3, and 4 with XNa = 0 to admittance determinations at various membrane voltages, similar to those shown in Figure 3. Filled triangles are from fits of the average (AVE) of the real and imaginary parts of eight separate, successive admittance determinations at each voltage. Open circles and squares are from fits of 1 standard deviation added to ( + SD) or subtracted from ( — SD) the real and imaginary parts of the AVE admittance. Intact axon 87-39 in ASW + TTX(1 piM)at 12.5 °C. Figure 4. Estimates of the potassium-conductance relaxation time, rn, from fits of eqs 2, 3, and 4 with XNa = 0 to admittance determinations at various membrane voltages, similar to those shown in Figure 3. Filled triangles are from fits of the average (AVE) of the real and imaginary parts of eight separate, successive admittance determinations at each voltage. Open circles and squares are from fits of 1 standard deviation added to ( + SD) or subtracted from ( — SD) the real and imaginary parts of the AVE admittance. Intact axon 87-39 in ASW + TTX(1 piM)at 12.5 °C.
High mobilities of cations are characteristic of FIC glasses. The high values of mobilities seem to have been inherited by the FIC glasses from the supercooled state. Moynihan et al. (1971) were the first to note in their investigation of LiCl solutions that as the glass transition is approached, the ratio of shear relaxation time (r, ) (= /7/G00) (see also chapters 7 and 9 for more information on r) to the conductivity relaxation time (r ) (= /cr(0)) becomes very large (a factor of 5 to 10 orders of... [Pg.240]


See other pages where Relaxation conductance is mentioned: [Pg.189]    [Pg.173]    [Pg.107]    [Pg.398]    [Pg.1]    [Pg.256]    [Pg.78]    [Pg.20]    [Pg.586]    [Pg.184]    [Pg.240]    [Pg.242]    [Pg.243]    [Pg.243]    [Pg.281]    [Pg.294]    [Pg.295]    [Pg.410]    [Pg.411]    [Pg.242]    [Pg.243]    [Pg.243]    [Pg.281]   
See also in sourсe #XX -- [ Pg.170 ]




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