In this work a new spectroelectrochemical method based on an inductively coupled plasma atomic emission spectrometry has been developed and used to measure the elementary dissolution rates of Fe, Cr, Ni, Mn, Mo, and Cu simultaneously during linear scan voltammetry of a 304 stainless steel in the active region. Simultaneous dissolution was observed for all elements with the exception of copper, which appeared in solution at a potential approximately 100 mV more positive. The Tafel slopes for Fe, Cr, Ni, and Mn partial dissolution rates were measured around the corrosion potential and found to be identical within experimental error, between 59 and 68 mV/decade. The anodic dissolution of copper in acidic chloride and sulfate solutions was used to establish the quantitative relationship between the concentration transients and the dissolution rate. The residence time distribution of the electrochemical flow cell was determined using galvanostatic pulses of copper or stainless steel dissolution. The experimental residence time distribution could be approximated to a high degree of accuracy at both long and short times by a log-normal distribution. The effect of the residence time distribution on the shape of partial elemental current transients during linear scan voltammetry was investigated by numerical simulation.

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Oxygen 18 O tracer diffusion in Czochralski-grown mullite single crystals is investigated along [010] and [001]. Oxygen diffusion coefficients range between ϳ5 ؋ 10 ؊20 m 2 /s (1250°C) and ϳ9 ؋ 10 ؊18 m 2 /s (1525°C). The data does not show any significant anisotropy. The values of the activation enthalpy (4.5 eV) and of the activation entropy ((3.4 ؎ 1.6)k B , where k B is the Boltzmann constant) suggest that the atomic transport occurs via thermally activated vacancies.

Self-diffusion studies of boron in polycrystalline TiB2 were carried out as a function of temperature, using a specially designed experiment with stable B10 tracers, B−enriched11 TiB2 samples, and secondary ion mass spectrometry for depth profiling. The diffusivities were extracted from the isotope depth profiles in the range between 950 and 1600 °C. They obey an Arrhenius behavior with an activation enthalpy of about ΔH=2.2 eV and a preexponential factor of D0=4×10−12 m2/s. Interpolation of the diffusivities to the melting point of 3225 °C reveals a very low value of about D(Tm)≈10−15 m2/s, which reflects the covalent bonds present in the material. A possible explanation for the low values obtained for D0 and ΔH is the assumption of a diffusion mechanism via vacancies, where in addition to thermal vacancies a substantial concentration of structural vacancies are present. The possible influence of grain boundaries and of the anisotropic crystal structure on the results is discussed together with crystallographic diffusion paths.