Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 90-94). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin-Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 150-152).

This thesis describes an electrochemical investigation of the processes occurring at the hydrogen evolving cathode during the industrial production of fluorine in molten KF–2HF. A 1A laboratory cell, designed for the purposes of the project, is described. Observations of the operation of this cell are reported. A comparison of a range of electrode materials is given, both with regard to electrochemical overvoltage and the bubbling releasing characteristics, for which photographic evidence is presented. In addition, measurements of the ohmic potential drop, caused by the presence of bubbles, were made for different bubble types. Included in the above is a description of any effects of metallic impurities present in the melt both on overvoltage and bubble release. A mechanistic study of hydrogen evolution on platinum is described and compared with the reaction at a mild steel electrode. A preliminary investigation into the use of parallel strand expanded metal electrodes was made and further photographic evidence presented.

Typescript, etc. / Digitized by Kansas State University Libraries

No description available.

No description available.

No description available.

The importance of energy storage worldwide is increasing with the use of renewable energy sources and electric vehicles. With the intermittent nature of wind and solar power, large-scale grid storage is an extremely important progression needed to reduce the use of fossil fuels. For this to become a reality, rechargeable batteries beyond existing Li-ion technologies need consideration. The development of such batteries requires improvement of understanding their component materials. Modern computer modelling techniques enable valuable insights into the fundamental defect, ion transport and voltage properties of battery materials at the atomic level. Atomistic simulation and ab initio density functional theory (DFT) techniques have been used to study a number of potential cathode materials for Na-ion and Mg batteries. Firstly, the olivine and maricite forms of NaFePO4 are considered in terms of their defect formation energies and Na ion diffusion. The atomistic study indicates that anti-site disorder is the most favourable type of intrinsic defect. The activation energies for Na-ion migration in the olivine and maricite materials are 0.4 eV and 1.6 – 1.8 eV respectively. Moreover, molecular dynamics (MD) studies reveal that there is only substantial Na-ion diffusion in the olivine structure, with diffusion coefficients (DNa) at 300 K of 7 x 10−13 cm2s−1 for maricite and 4 x 10−9 cm2s−1 for olivine NaFePO4. The presence of anti-site defects is shown to decrease Na+ diffusion within the olivine structure, which is of relevance to its rate behaviour. Secondly, the effect of lattice strain on ion transport and defect formation in olivine-type LiFePO4 and NaFePO4 is investigated as a means to enhance their ion conduction properties. It is predicted that lattice strain can have a remarkable effect on the rate performance of olivine cathode materials, with a major increase in ionic conductivity and decrease in blocking defectsat room temperature. Thirdly, DFT techniques have been used to examinesurface and grain boundary formation in P2-NaCoO2. The coordination lossexperienced by ions present at surfaces is found to influence the resultingsurface energy. Layered oxide cathode materials were further investigated byconsidering the effect of Mg2+ doping on P2-Na2 [Ni1 Mn2 ]O2. Na vacancy 333formation energies decreased with 10% Mg2+ doping on the Ni site and an increase in Na diffusion was predicted with MD calculations. This positive effect on Na ion conductivity is caused by displacement of the Mg ions from the transition metal layer and the resulting change in electrostatic potential. Finally, Mg ion conduction, doping and voltage behaviour of MgFeSiO4 were studied. The Mg-ion migration activation energy is relatively low for an olivine-type silicate, and MD simulations predict a diffusion coefficient (DMg) of 10−9 cm2s−1, suggesting favourable electrode kinetics. Partial substitution of Fe by Co or Mn could increase the cell voltage from 2.3 V vs Mg/Mg2+ to 2.8 - 3.0 V.

In this study, a deposition system called EAVD was made to deposite porous LSCF films used as cathode material in the solid oxide fuel cell (SOFC). The relation of deposition parameters to morphology was discussed. Porous La0.8Sr0.2Co0.2Fe0.8O3 films were successfully deposited on Corning glass and ceria substrates, and a pseudo-cubic perovskite phase was obtained after a post-calcination at 750¢J for 2 hrs. Deposition parameters, such as deposition time, deposition temperature, flow rate, voltage applied, different kinds of set-ups (downward spraying or upward spraying), were discussed. The obtained calcined films were characterized by X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). On the other hand, surface and cross-section morphology were examined using SEM. In the series using downward spraying system, deposition temperature and deposition time showed profound effect on morphology. With increasing the extent of these two factors, porous films were obtained. With decreasing the extent of these two factors, however, dense films were obtained. The effects of other parameters to morphology were less obvious. Under proper conditions, cauliflower-like films with high porosity were obtained. In the series using upward spraying system (vertical set-up), reticular films were successfully obtained using deposition temperature ranging from 275~320¢J, flow rate 1.0~1.5 ml/hr, and deposition time within 2 hrs. In the series of flow rate, the pores of reticular structure seemed to grow up with increasing flow rate. Under the condition of prolonged deposition (4 hrs), a stalactitc structure with micropores on it was obtained. The highly porous structures obtained in this study are very suitable for applications in gas sensor and electrodes in SOFC.

No description available.