Stability of Electrode-Electrolyte Interfaces during Charging in Lithium Batteries

In this thesis we study the growth of a Li electrode-electrolyte interface in the presence of an elastic prestress. In particular, we focus our interest on Li-air batteries with a solid electrolyte, LIPON, which is a new type of secondary or rechargeable battery. Theoretical studies and experimental evidence show that during the process of charging the battery the replated lithium adds unevenly to the electrode surface. This phenomenon eventually leads to dendrite formation as the battery is charged and discharged numerous times. In order to suppress or alleviate this deleterious effect of dendrite growth, we put forth a study based on a linear stability analysis. Taking into account all the mechanisms of mass transport and interfacial kinetics, we model the evolution of the interface. We find that, in the absence of stress, the stability of a planar interface depends on interfacial diffusion properties and interfacial energy. Specifically, if Herring-Mullins capillarity-driven interfacial diffusion is accounted for, interfaces are unstable against all perturbations of wavenumber larger than a critical value. We find that the effect of an elastic prestress is always to stabilize planar interfacial growth by increasing the critical wavenumber for instability. A parametric study results in quantifying the extent of the prestress stabilization in a manner that can potentially be used in the design of Li-air batteries. Moreover, employing the theory of finite differences we numerically solve the equation that describes the evolution of the surface profile and present visualization results of the surface evolution by time. Lastly, numerical simulations performed in a commercial finite element software validate the theoretical formulation of the interfacial elastic energy change with respect to the planar interface.

The far-field spatial coherence of Gaussian Schell-model beam in turbulence in terms of position vectors

Spatial coherence properties of beam produced by Gaussian Schell-model source when the beam is propagating through atmosphere have been analyzed in terms of position vectors. New expressions for cross-spectral density of optical field and spectral degree of coherence as well as radiant intensity have been developed. Numerical results illustrated in this paper indicate the coherence degradation suffered from atmospheric turbulence and their directional dependence. (C) 2007 Elsevier GmbH. All rights reserved.

Evaluación del impacto radiológico ambiental de una industria NORM

[ES]El proceso de soldadura más común es la soldadura por arco metálico con electrodos revestidos. A veces ese revestimiento contiene materiales radiactivos de origen natural (NORMs). En España los electrodos más utilizados son los recubiertos de rutilo mezclado con otros materiales. El rutilo contiene algunos radionúclidos naturales detectables, por lo que puede ser considerado como un NORM. Este trabajo principalmente se centra en la aplicación de la metodología expuesta en la Guía de Seguridad 11.3 del Consejo de Seguridad Nuclear (Metodología para la evaluación del impacto radiológico en las industrias NORM), como una herramienta para obtener las dosis en una fábrica que produce este tipo de electrodo y evaluar el impacto radiológico en una instalación específica. Para ello, se aplicaron en dicha instalación los pasos requeridos por la metodología para su cumplimiento. Se analizaron los beneficios inherentes al estudio y se identificaron las zonas de radiación más altas así como la posición de los trabajadores. Habiendo hecho uso de evaluaciones de dosis llevadas a cabo con anterioridad por otros procedimientos, métodos de simulación, se establecieron las pautas de protección radiológica a seguir para el cumplimiento de dicha guía, mediante la colocación de dosímetros personales y monitores de radiación.

Exotic species and genetically modified organisms in aquaculture and enhanced fisheries: ICLARM's position

This article contains a discussion paper on the use of exotic species and genetically modified organisms in aquaculture and enhanced fisheries, together with a summary of ICLARM's (International Center for Living Aquatic Resources Management, Philippines) current position on this important topic.