Doping kinetic effects

Boltzmann term, 1078 computer simulation. 1161 current density, 1078, 1081 current potential relation, 1082 doping, 1073 effect of light on, 785 -/junction, 1081 electrode kinetics of, 170 electrodeposition on, 1344... 

Fichtner et al studied the kinetic effects of Mg(AlH4)2 doped with 2 mol% TiCl3 and mechanically milled for up to 100 minutes. The studies showed that the peak decomposition temperature was reduced in the presence of the titanium dopant. The starting point of the first decomposition step shifted to lower temperatures however, complete dehydrogenation to MgH2 still requires heating to -200 °C. 

In the fabrication of microporous hollow-fiber membrane, the development of membrane pores can be correlated to thermodynamic and kinetic effects of the polymer dope. When additives were introduced into the polymer dope, two significant effects transpired. First, instantaneous demixing would occur, which was due to the thermodynamic enhancement of phase separation by reducing the miscibility of the solution dope with the nonsolvent. Second, the increased viscosity of the solution would cause kinetic hindrance against the phase separation process, which resulted in a delay of solution demixing [45]. 

Additional information concerning the mechanisms of solid—solid interactions has been obtained by many diverse experimental approaches, as the following examples testify adsorptive and catalytic properties of the reactant mixture [1,111], reflectance spectroscopy [420], NMR [421], EPR [347], electromotive force determinations [421], tracer experiments [422], and doping effects [423], This list cannot be comprehensive. Electron probe microanalysis has also been used as an analytical (rather than a kinetic) tool [422,424] for the determination of distributions of elements within the reactant mixture. Infrared analyses have been used [425] for the investigation of the solid state reactions between NH3 and S02 at low temperatures in the presence and in the absence of water. 

References to a number of other kinetic studies of the decomposition of Ni(HC02)2 have been given [375]. Erofe evet al. [1026] observed that doping altered the rate of reaction of this solid and, from conductivity data, concluded that the initial step involves electron transfer (HCOO- - HCOO +e-). Fox et al. [118], using particles of homogeneous size, showed that both the reaction rate and the shape of a time curves were sensitive to the mean particle diameter. However, since the reported measurements refer to reactions at different temperatures, it is at least possible that some part of the effects described could be temperature effects. Decomposition of nickel formate in oxygen [60] yielded NiO and C02 only the shapes of the a—time curves were comparable in some respects with those for reaction in vacuum and E = 160 15 kJ mole-1. Criado et al. [1031] used the Prout—Tompkins equation [eqn. (9)] in a non-isothermal kinetic analysis of nickel formate decomposition and obtained E = 100 4 kJ mole-1. 

C. Shen and N.M. Kostic. Kinetics of photoinduced electron-transfer reactions within sol-gel silica glass doped with zinc cytochrome c. Study of electrostatic effects in confined liquids. J. Am. Chem. Soc. 119, 1304-1312 (1997). 

For moderately doped substrates, when the surface is free of oxide the change of potential is mostly dropped in the space charge layer and in the Helmholtz double layer. The reactions are very sensitive to geometric factors. The reaction that is kinetically limited by the processes in the space charge layer is sensitive to radius of curvature, while that limited by the processes in the Helmholtz layer is sensitive to the orientation of the surface. Depending on the relative effect of each layer the curvature effect versus anisotropic effect can vary. 

The liquid-phase reaction kinetics of doped molecules in silica nanomatrixes was conducted using the metalation of meso-tetra (4-Ai,Ai,Ai-trimethylanilinium) porphyrin tetrachloride (TTMAPP) with Cu(II) as a model. To demonstrate the effect of the silica nanomatrix on the diffusion, pure silica shells with varied thickness were coated onto the same silica cores, which doped the same amount of TTMAPP molecules. The Cu(II) from the suspension could penetrate into the silica nanomatrixes and bind to the TTMAPP. The reaction rate of TTMAPP metalation with Cu(II) was significantly slower than that in a bulk solution. The increase in the thickness of the silica resulted in a consistent decrease of reaction rates (Fig. 8). 

A. Andreasen, Effect of Ti-doping on the dehydrogenation kinetic parameters of lithium aluminum hydride , J. Alloys Compd. 419 (2006) 40-44. 

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