Oxygen transport in tetragonal Pr2NiO4+d has been investigated using molecular dynamics simulations in conjunction with a set of Born model potentials. Oxygen diffusion in Pr2NiO4+d is highly anisotropic, occurring almost entirely via an interstitialcy mechanism in the a–b plane. The calculated oxygen diffusivity has a weak dependence upon the concentration of oxygen interstitials, in agreement...

Monte Carlo simulations using crystal chemical constraints have been used to elucidate the copper diffusion mechanisms in copper-doped zinc sulfide. Relaxation around the ZnSuCu S interface allows facile copper diffusion, particularly in the 22x presence of substitutional oxygen or sulfur vacancies. Copper diffusion is responsible for the brightness degradation in this electroluminescent materi...

The solid state reaction of CUWO4-2 formation from CuO and WO3 was studied by the contact method in air and nitrogen. The results showed that the reaction is governed by the diffusion of the W 6 + and 0 2 _ ions and that the rate determining step is the diffusion of oxygen ions in the reaction product. This is in agreement with the defect structure of copper tungstate, an n-type semiconductor w...

An accurate and rapid method for determining the diffusion coefficients of electrochemically active gases in electrolytes is described. The technique is based on chronoamperometry where transient currents are measured and interpreted with a Cottrell-related equation. The diffusion coefficients of oxygen were determined for NaCl solutions varying from 0.085 to 0.846 M within the temperature rang...

Oxygen coulometric titration has been applied to measure chemical diffusion in La0 45r0 2CoO36 between 700 and 1000°C. The transient current response to a potentiostatic step has been transformed from the time domain to the frequency domain. The equivalent circuit used to fit the resulting impedance data contains the element that describes the finite-length diffusion of oxygen into the sample s...

Oxygen transfer through a cotton plug follows Fick's law of diffusion. The apparent diffusion constant decreases as the density of cotton packing is increased. Formulas are derived which relate oxygen transfer to cotton-plug dimensions. Calculations indicate that the dimensions of a cotton plug can affect both the maximal oxygen uptake rate and the gas composition inside a shaken flask. In some...

Using in situ atomic-resolution electron microscopy observations, we report observations of the oxide growth during the oxidation of stepped Cu surfaces. Oxidation occurs via direct growth of Cu(2)O on flat terraces with Cu adatoms detaching from steps and diffusing across the terraces. This process involves neither reconstructive oxygen adsorption nor oxygen subsurface incorporation and is rat...

Output characteristics of fuel cells are affected by a large number of parameters such as geometry, dimensions, construction materials and conditions of supplying fluids. In this paper a mathematical model followed by a two-dimensional numerical approach has been presented to study the fuel cell parametrically. Effect of oxygen concentration at gas diffusion layer entrance, temperature and ...

Several oxygen adducts are formed when oxygen is diffused into the interplanar spacings of solid -Fe II Pc suspended in water. The constraints imposed by the solid matrix induce formation of interesting oxygen adducts which cannot be synthesized by regular solution chemistry. One of the oxygen adducts exhibits low-spin to high-spin transition with considerable thermal hysteresis.