Arrhenius-type behavior

The relationship between the ionic conductivity oi and the temperature T can either be derived from the diffusivity D or the mobility u assuming Arrhenius-type behavior ... 

The objective is to determine the parameters and their standard errors by the Gauss-Newton method for each temperature and then check to see if the parameter estimates obey Arrhenius type behavior. 

Because JPS is limited by reaction kinetics and mass transport a dependency on the HF concentration cHf and the absolute temperature Tcan be expected. An exponential dependence of JPS on cHf has been measured in aqueous HF (1% to 10%) using the peak of the reverse scan of the voltammograms of (100) p-type electrodes. If the results are plotted versus 1/7) a typical Arrhenius-type behavior... 

Fig. 4.10 Critical current density JPS of (100) oriented silicon electrodes for different HF concentrations plotted versus the inverse absolute temperature 1/71 Arrhenius-type behavior, with an activation energy of 0.345 eV, is observed.

Sorption, diffusion, and permeation are processes activated by heat and, as expected, follow an Arrhenius type behavior. Thus, we can write... 

It should be emphasized that the reaction is occurring under thermal conditions at a temperature defined by the helium buffer gas. Measuring rate constants k as a function of temperature yields activation energies Ea and pre-exponential factors A for the reaction, assuming Arrhenius-type behavior ... 

Fast relaxation processes ( , 0) show a Williams-Landel-Ferry (WLF) type temperature dependence which is typical for the dynamics of polymer chains in the glass transition range. In accordance with NMR results, which are shown in Fig. 9, these relaxations are assigned to motions of chain units inside and outside the adsorption layer (0 and , respectively). The slowest dielectric relaxation (O) shows an Arrhenius-type behavior. It appears that the frequency of this relaxation is close to 1-10 kHz at 240 K, which was also estimated for the adsorption-desorption process by NMR (Fig. 9) [9]. Therefore, the slowest relaxation process is assigned to the dielectric losses from chain motion related to the adsorption-desorption. 

Example 5.3.2 demonstrates how the heat of adsorption of reactant molecules can profoundly affect the kinetics of a surface catalyzed chemical reaction. The experimentally determined, apparent rate constant Ikj/Ki) shows typical Arrhenius-type behavior since it increases exponentially with temperature. The apparent activation energy of the reaction is simply app = E2 - AHadsco = - A//adsco (see Example 5.3.2), which is a positive number. A situation can also arise in which a negative overall activation energy is observed, that is, the observed reaction rate... 

In the opinion of the authors this equation may be considered as the Arrhenius-parallel emerging at high temperatures. Noteworthy is the difference from the classical Arrhenius equation recalled in the introduction. There is an extensive evidence for the crossover from the VET- to the Arrhenius-type behavior on heating above the melting temperature. " However, the analysis of high resolution experimental data for glass forming liquids indicate also the... 

Arrhenius-type behavior and strong if v(T) is close to the latter. neutron spectroscopy. The data cover a frequency or time-... 

Much stronger dependences were observed as a function of the temperature. All systems investigated exhibited an Arrhenius-type behavior for the critical shear rate... 

A third indentation test parameter of fundamental importance is temperature. In several studies of the temperature dependence of hardness, an activated process becomes apparent from Arrhenius-type behavior. Calculation of the activation energies associated with thermal softening is characteristic of the activated processes governing plastic flow in crystals. " Thus, the role played by the crystal structure in determining micro- and low-load hardness values must be a major one since, apart from its effect on lattice energy, the actual arrangement of the ions in a ceramic crystal is important in determining the ease of plastic flow. This aspect of ceramic hardness and its potential applications is discussed in Chapter 3. 

Battery life is also related to temperature (Arrhenius-type behavior). The optimal temperature for the use of stationary batteries ranges from 20°C to 30°C, although temperatures from -40°C to 50°C can be tolerated. At higher temperatures, the rated capacity is more available but promotes self-discharge and reduces battery cycle life. 

Life on float service has been found to be related to temperature (Arrhenius-type behavior), as plotted in Fig. 23.44. The growth rate constant k is plotted for several different types of grid alloys used for the telephone system. At 25°C the time to reach 4% growth, an upper limit before the battery s integrity is impaired, is calculated to be 13.8 years for PbSb, 16.8 years for PbCa, and 82 years for pure lead. ... 

Plotted in Figure 19 is against inverse temperature for ethene homopolymerizations at 2000 bar and very low initiation rates. " Arrhenius-type behavior of Ctr,M is clearly seen. The slope to the straight line yields the difference in the activation energies for CT to monomer and propagation. With EaC p) being known from SchweeTs work, the experimental value of EA(Qr,M) yields EA(fetr,M) = (74 8) kj mol" which is remarkably close to a(Vm) = 83 kjmol" estimated by Heuts et from ab initio quantum mechanical calculations for the transfer reaction between an ethyl radical and ethene. 

The oxide ion conductivity exhibits an Arrhenius-type behavior (Fig. 2.2). For YSZ, no oxygen potential dependence is observed over a wide oxygen partial pressure range applicable to solid oxide fuel cells. For electron and hole conductivities, the oxygen potential dependence is given by the following equation ... 

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