Mobility, increase

Correlation between Mobility and Its Temperature Coefficient. For most species of ions in Table 4 it will be seen that the value of CJ is appreciably less than unity with rise of temperature the mobility increases... 

It is obvious, and verified by experiment [73], that above a critical trap concentration the mobility increases with concentration. This is due to the onset of intertrap transfer that alleviates thermal detrapping of a carrier as a necessary step for charge transport. The simulation results presented in Figure 12-22 are in accord with this notion. The data for p(c) at ,=0.195 eV, i.e. EJa—T), pass through a minimum at a trap concentration c—10. Location of the minimum on a concentration scale depends, of course, on , since the competition between thermal detrapping and inter-trap transport scales exponentially with ,. The field dependence of the mobility in a trap containing system characterized by an effective width aeff is similar to that of a trap-free system with the same width of the DOS. 

So far, the data mentioned were measured at 25° C as is usual in electrochemical practice. However, it should not be forgotten that the ion mobilities increase considerably with temperature (see the Smithsonian table of equivalent conductivities as different temperatures in the Handbook of Chemistry and Physics, 61st ed.), although with the same trends for the various ions therefore, the change in transference numbers remains small and shows a tendency to approach a value of 0.5 at higher temperatures. 

The dependences of electron mobility on medium density and on phase change are complex and poorly understood. In Ar, Kr and Xe, the mobility increases by a factor of about 2 in going from the liquid to the solid phase. This has generated speculation that long-range order is not necessary for high electron mobility. On the other hand, electron mobility in Ne increases from 10-3 to 600 cm2v 1s 1 on solidification at 25.5 K (see Allen, 1976). In liquid He, the electron mobility above the A-point (2.2 K) varies approximately inversely with the viscosity, consistent with the bubble model. Below the A-point, the mobility... 

In the study by Johnson et al. (1986) it was shown by Hall effect measurements that the sheet carrier density was decreased and the mobility was increased for a thin w-type layer following exposure to a hydrogen plasma at 150°C. To explain the mobility increase it was argued that donor-H complexes were formed and that the concentration of ionized scattering centers was thereby decreased. On the basis of semiempirical calculations, a structural model was suggested for the donor-H complex in... 

One of the major differences among the phases of water at the molecular level is the motions of the water molecules. Using the phase diagram (Figure 7), we can follow the effects of temperature and pressure on the molecular mobility of water. For example, if we hold pressure constant (say at 1 atm) and increase temperature, molecular mobility increases as we move from the solid to the liquid to the gas phase regions. Conversely, if we hold temperature constant (say at 100°Q and increase pressure, molecular mobility decreases as we move from the gas to the liquid phase region. 

Using the time-dependent aspect of state diagrams, Roos (2003) illustrated the effects of temperature, water activity, or water content on relaxation times and relative rates of mechanical changes in amorphous systems (Figure 36). This diagram can be considered as a type of mobility map, where mobility increases (relaxation time decreases) as temperature and/or water content/activity increases. Le Meste et al. (2002) suggested the establishment of mobility maps for food materials showing characteristic relaxation times for different types of molecular motions as a function of temperature and water content. 

In addition to methyl iodide the term iodomethane can be used. For purposes of classification the alkyl halides are to be regarded as esters. The halogen does not ionize and its mobility increases in the order chloride, bromide, iodide. 

Pulsed field gradient (PFG)-NMR experiments have been employed in the groups of Zawodzinski and Kreuer to measure the self-diffusivity of water in the membrane as a function of the water content. From QENS, the typical time and length scales of the molecular motions can be evaluated. It was observed that water mobility increases with water content up to almost bulk-like values above T 10, where the water content A = nn o/ nsojH is defined as the ratio of the number of moles of water molecules per moles of acid head groups (-SO3H). In Perrin et al., QENS data for hydrated Nation were analyzed with a Gaussian model for localized translational diffusion. Typical sizes of confining domains and diffusion coefficients, as well as characteristic times for the elementary jump processes, were obtained as functions of A the results were discussed with respect to membrane structure and sorption characteristics. ... 

A glass membrane in an electrolyte solution cannot be taken to be a homogeneous system in the direction perpendicular to the surface. When the membrane is in contact with the solution, water molecules can enter it and form a 5-100 nm thick hydrated layer [319]. The formation of this hydrated layer is actually a condition for good functioning of the glass electrode. The basic characteristics of the glass structure probably do not change in the hydrated layer, but the cation mobility increases considerably compared with the compact membrane interior... 

The M2j pyrogram of a typical brown coal (Figure 1 (A)) reveals the significant thermally-activated molecular mobility which occurs on heating from room temperature to 600 K. This has been shown to be the result of fusion of the extractable component of such coals (9 ). The reduction in molecular mobility (increase in above... 

In a parallel experiment, the extent of the reaction a is measured using the partial heat to a particular time divided by the total heat of the isotherm plus the residual heat of a subsequent 10°/min ramp. Figures 5 and 6 show the observed relationship of In a and In t to a. As expected for a similar degree of advancement a, the ionic mobility a increases with temperature. Similarly for the same value of a, the dipolar mobility increases. An increase in dipolar mobility corresponds to a shorter relaxation time. Thus t decreases as temperature increases. Somewhat unexpected, both In a and In t exhibit a nearly linear dependence on a. Curvature in the In a and In t versus a plot is most pronounced for small values of a and at the highest temperature. There is no evidence of a break in the In <7 or In T dependence on a which would indicate gel. 

When groups are inserted into the main chain, its regularity is disturbed and chain mobility increases (reduction of the enthalpy of melting as well as increase of the entropy of melting). Thus, polymers are formed that can be further processed from solution or in bulk. 

Little is known concerning the chemistry of nickel in the atmosphere. The probable species present in the atmosphere include soil minerals, nickel oxide, and nickel sulfate (Schmidt and Andren 1980). In aerobic waters at environmental pHs, the predominant form of nickel is the hexahydrate Ni(H20)g ion (Richter and Theis 1980). Complexes with naturally occurring anions, such as OH, SO/, and Cf, are formed to a small degree. Complexes with hydroxyl radicals are more stable than those with sulfate, which in turn are more stable than those with chloride. Ni(OH)2° becomes the dominant species above pH 9.5. In anaerobic systems, nickel sulfide forms if sulfur is present, and this limits the solubility of nickel. In soil, the most important sinks for nickel, other than soil minerals, are amorphous oxides of iron and manganese. The mobility of nickel in soil is site specific pH is the primary factor affecting leachability. Mobility increases at low pH. At one well-studied site, the sulfate concentration and the... 

For certain liquids like cyclohexene [158], o-xylene, and m-xylene [159], the mobility increases with increasing pressure (see Fig. 11). These results provided the key to understand the two-state model of electron transport. In terms of the model, AFtr is positive for example, for o-xylene, AFtr is +21 cm /mol. Since electrostriction can only contribute a negative term, it follows that there must be a positive volume term which is the cavity volume, Fcav(e). The observed volume changes, AFtr, are the volume changes for reaction (23). These can be identified with the partial molar volume, V, of the trapped electron since the partial molar volume of the quasi-free electron, which does not perturb the liquid, is assumed to be zero. Then the partial molar volume is taken to be the sum of two terms, the cavity volume and the volume of electrostriction of the trapped electron ... 

On lowering the temperature through Ty, a bandgap Eg = 0.1 eV appears in the FeB-ai(l) conduction band of Fig. 3 at Ep. The Hall coefficient increases as Rh exp(Ty/T), indicating that the charge-carrier density increases exponentially with T" , as in a normal semiconductor, and the Hall mobility increases from about 0.1 to 0.4 cm /Vs on lowering the temperature from Ty = 120 K to 77 K ... 

As the substrate temperature increases, the surface mobility increases and the structural morphology first transforms to that of Zone T, ie, tighdy packed fibrous grains having weak grain boundaries, and then to a hill density columnar morphology corresponding to Zone 2 (see Fig. 7). 

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