A 13C and 6Li variable temperature NMR study of 2-ethylbutyllithium/lithium 2-ethyl-1-butoxide mixed aggregates formed from reacting 2-ethyl-1-butanol with 2-ethylbutyllithium in two O/Li ratios of 0.2/1 and 0.8/1. The 0.2/1 sample resulted in two 2-ethylbutyllithium/lithium 2-ethyl-1-butoxide mixed aggregates and seven lithium hydride/lithium 2-ethyl-1-butoxide mixed aggregates. The lithium hydride mixed aggregates were also studied using selective 1H decoupling experiments. The 0.8/1 sample resulted in six 2-ethylbutyllithium/lithium 2-ethyl-1-butoxide mixed aggregates and five lithium hydride/lithium 2-ethyl-1-butoxide mixed aggregates. A low temperature 13C NMR spectroscopy study of n-pentyllithium indicated three aggregates, most likely a hexamer, an octamer, and a nonamer. A low temperature 13C NMR study of an 0.2/1 O/Li ratio sample of n-pentyllithium mixed with 1-pentanol resulted in three n-pentyllithium/lithium n-pentoxide aggregates mixed aggregates along with the three n-pentyllithium aggregates. 13C NMR data for this mixture gave inconclusive results whether or not lithium hydride/lithium alkoxide mixed aggregates were present in the sample.

Electrochemical behavior of electrolytic manganese dioxide (EMD), chemically prepared battery grade manganese dioxide (BGM), titanium dioxide (TiO2), lithium iron phosphate (LiFePO4) and lithium manganese phosphate (LiMnPO4) in aqueous lithium hydroxide electrolyte has been investigated. These materials are commonly used as cathodes in non-aqueous electrolyte lithium batteries. The main aim of the work was to determine how the electroreduction/oxidation behavior of these materials in aqueous LiOH compares with that reported in the literature in non-aqueous electrolytes in connection with lithium batteries. An objective was to establish whether these materials could also be used to develop other battery systems using aqueous LiOH as electrolyte. The electrochemical characteristics of the above materials were investigated by subjecting them to slow scan cyclic voltammetry and determining the charge/discharge characteristics of Zn/cathode material-aqueous LiOH batteries. The products of electroreduction/oxidation were characterized by physical techniques using X-ray diffraction (XRD), scanning electron micrography (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), Thermogravimetric analysis (TG) and infra-red spectrometry (IR). The reduction of ã-MnO2 (EMD) in aqueous lithium hydroxide electrolyte is found to result in intercalation of Li+ into the host structure of ã-MnO2. The process was found to be reversible for many cycles. This is similar to what is known to occur for ã-MnO2 in non-aqueous electrolytes. The mechanism, however, differs from that for reduction/oxidation of ã-MnO2 in aqueous potassium hydroxide electrolyte. KOH electrolyte is used in the state-of-art aqueous alkaline Zn/MnO2 batteries. Alkaline batteries based on aqueous KOH as the electrolyte rely upon a mechanism other than K+ intercalation into MnO2. This mechanism is not reversible. This is explained in terms of the relative ionic sizes of Li+ and K+. The lithium-intercalated MnO2 lattice is stable because Li+ and Mn4+ are of approximately the same size and hence Li+ is accommodated nicely into the host lattice of MnO2. The K+ ion which has almost double the size of Li+ cannot be appropriately accommodated into the host structure and hence the K+ -intercalated MnO2 phase is not stable. Chemically prepared battery grade MnO2 (BGM) is found to undergo electroreduction/oxidation in aqueous LiOH via the same Li+ intercalation mechanism as for the EMD. While the Zn/BGM- aqueous LiOH cell discharges at a voltage higher than that for the Zn/EMD- aqueous LiOH cell under similar conditions, the rechargeability and the material utilization of the BGM cell is poorer. The cathodic behavior of TiO2 (anatase phase) in the presence of aqueous LiOH is not reversible. In addition to LiTiO2, Ti2O3 is also formed. The discharge voltage of the Zn/TiO2- aqueous LiOH cell and material utilization of the TiO2 as cathode are very low. Hence TiO2 is not suitable for use in any aqueous LiOH electrolyte battery. LiFePO4 (olivine-type structure) as a cathode undergoes electrooxidation in aqueous LiOH forming FePO4. However the subsequent reduction forms not only the original LiFePO4 but also Fe3O4. Thus the process is not completely reversible and hence LiFePO4 is not a suitable material for use as a cathode in aqueous battery systems. LiMnPO4 (olivine-type structure) undergoes reversible electrooxidation in aqueous LiOH forming MnPO4. The charge/discharge voltage profile of the Zn/MnPO4-aqueous LiOH cell, its coulombic efficiency and rechargeability are comparable to that of the cell using ã-MnO2. EMD and LiMnPO4 both have the potential for use in rechargeable batteries using aqueous LiOH as the electrolyte. Recommendations for further developmental work for such batteries are made.

This thesis is focused on the mechanisms for corrosion andhydriding of Zircaloy. Special attention is paid tomicrostructural characterisation by cross sectionaltransmission electron microscopy of the oxide layer formed.Three main topics have been treated in this work: (i)Pre-transition oxides were investigated with the purpose ofevaluating if it is possible to predict post-transitionbehaviour of different alloys. (ii) The reason for the commonlyobserved accelerated corrosion of Zircaloy in the presence oflithium hydroxide was investigated by studying the phasetransformation of differently stabilised zirconium oxides andby corrosion studies. (iii) Pre-hydrided Zircaloy-2 was studiedto investigate the influence of hydrogen on the oxidationbehaviour. Characterisation of pre-transition oxides formed onzirconium alloys, has been accomplished with the aim ofdetermining if there are any differences in the properties(morphology, pores, cracks and phases) of the oxide layersformed which might explain the differences in corrosionbehaviour later in life. Four Zircaloy-2 versions and oneZircaloy-4 version were tested in an autoclave at 288° Cfor 20h and 168h and at 360˚C for 96h. Based on thecharacterisation of pre-transition oxide layers only small orno differences were found between the different alloycompositions, thus it is not possible to predict long-timecorrosion behaviour by studying pre-transition oxides. However,large differences were found between the two test temperatures.The higher oxidation temperature results in increased oxidationrates and larger oxide grains, the columnar grains are a factorof 3-4 longer, and the equiaxed grains have an almost doubledmaximum diameter. The fraction of columnar grains andtetragonal phase also increases with temperature. The reasonfor the difference in morphology between the two temperaturesis not fully understood, but the results show that acceleratedtesting at elevated temperatures may be a questionableapproach. One of the Zircaloy-2 samples was also anodicallyoxidised. The oxide layer formed only contains equiaxed grainsand phase analysis shows both monoclinic and tetragonal phasesare present. Oxidation tests of Zircaloy-2 and Zircaloy-4 in water andlithiated water at 360 ° C show that the pre-transitionoxidation rate is not affected by the presence of LiOH, but thetransition occurs earlier and the post-transition oxidationrate is increased. The oxidation rate correlates with thedensity of cracks in the oxide layer and the morphology of theoxide grains. The oxides formed have a layered structure andfor samples oxidised in LiOH solution the inner protectivelayer is thin. The effect of LiOH is suggested to be the resultof partial dissolution of the oxide and subsequentincorporation of lithium ions during adissolution-precipitation process. Newly formed oxide isprobably more hydrous, and the grain boundaries areparticularly liable to dissolution. The increased concentrationof LiOH within cracks and pores could reach the detrimentallevels necessary for dissolution. This is supported by theinsensitivity in the pre-transition region to both thecompositions of the alloy and to the environment. The alloycomposition influences the microstructure of the oxide layer,and thereby the resistance to accelerated corrosion rate inlithiated water. The hydrogen pickup ratio follows the weightgain, not the oxidation rate, up to the second transition. Whenthe protective oxide layer is degraded the hydrogen pickupratio increases markedly. To evaluate if hydrogen is a cause for or a consequence ofaccelerated corrosion, pre-transition oxidation tests ofZircaloy-2 have been performed with hydrogen present in threedifferent states: i) Hydrogen in solid solution in thezirconium alloy, corresponding to the initial oxidation priorto precipitation of hydrides. ii) Uniformly distributedhydrides simulating a situation in whish hydrides starts toprecipitate and iii) Massive surface hydride claimed to be themain cause of accelerated oxidation. Based on the resultsobtained, it is concluded that the oxidation of massivezirconium hydride resembles the oxidation of zirconium metal.This fact clearly shows that accelerated oxidation of zirconiumalloys cannot be due solely to the presence of a massivehydride layer, but also requires a combined effect offorexample interfacial roughness and hydride precipitation. <b>Keywords:</b>Zircaloy, Zirconium alloys, Oxidation, Oxidelayer, Pre-Transition, Hydriding, Pre-Hydrided, Hydrides,Lithium Hydroxide (LiOH), Lithiated Water, Dissolution, CrossSectional TEM

<p>This thesis is focused on the mechanisms for corrosion andhydriding of Zircaloy. Special attention is paid tomicrostructural characterisation by cross sectionaltransmission electron microscopy of the oxide layer formed.Three main topics have been treated in this work: (i)Pre-transition oxides were investigated with the purpose ofevaluating if it is possible to predict post-transitionbehaviour of different alloys. (ii) The reason for the commonlyobserved accelerated corrosion of Zircaloy in the presence oflithium hydroxide was investigated by studying the phasetransformation of differently stabilised zirconium oxides andby corrosion studies. (iii) Pre-hydrided Zircaloy-2 was studiedto investigate the influence of hydrogen on the oxidationbehaviour.</p><p>Characterisation of pre-transition oxides formed onzirconium alloys, has been accomplished with the aim ofdetermining if there are any differences in the properties(morphology, pores, cracks and phases) of the oxide layersformed which might explain the differences in corrosionbehaviour later in life. Four Zircaloy-2 versions and oneZircaloy-4 version were tested in an autoclave at 288° Cfor 20h and 168h and at 360˚C for 96h. Based on thecharacterisation of pre-transition oxide layers only small orno differences were found between the different alloycompositions, thus it is not possible to predict long-timecorrosion behaviour by studying pre-transition oxides. However,large differences were found between the two test temperatures.The higher oxidation temperature results in increased oxidationrates and larger oxide grains, the columnar grains are a factorof 3-4 longer, and the equiaxed grains have an almost doubledmaximum diameter. The fraction of columnar grains andtetragonal phase also increases with temperature. The reasonfor the difference in morphology between the two temperaturesis not fully understood, but the results show that acceleratedtesting at elevated temperatures may be a questionableapproach. One of the Zircaloy-2 samples was also anodicallyoxidised. The oxide layer formed only contains equiaxed grainsand phase analysis shows both monoclinic and tetragonal phasesare present.</p><p>Oxidation tests of Zircaloy-2 and Zircaloy-4 in water andlithiated water at 360 ° C show that the pre-transitionoxidation rate is not affected by the presence of LiOH, but thetransition occurs earlier and the post-transition oxidationrate is increased. The oxidation rate correlates with thedensity of cracks in the oxide layer and the morphology of theoxide grains. The oxides formed have a layered structure andfor samples oxidised in LiOH solution the inner protectivelayer is thin. The effect of LiOH is suggested to be the resultof partial dissolution of the oxide and subsequentincorporation of lithium ions during adissolution-precipitation process. Newly formed oxide isprobably more hydrous, and the grain boundaries areparticularly liable to dissolution. The increased concentrationof LiOH within cracks and pores could reach the detrimentallevels necessary for dissolution. This is supported by theinsensitivity in the pre-transition region to both thecompositions of the alloy and to the environment. The alloycomposition influences the microstructure of the oxide layer,and thereby the resistance to accelerated corrosion rate inlithiated water. The hydrogen pickup ratio follows the weightgain, not the oxidation rate, up to the second transition. Whenthe protective oxide layer is degraded the hydrogen pickupratio increases markedly.</p><p>To evaluate if hydrogen is a cause for or a consequence ofaccelerated corrosion, pre-transition oxidation tests ofZircaloy-2 have been performed with hydrogen present in threedifferent states: i) Hydrogen in solid solution in thezirconium alloy, corresponding to the initial oxidation priorto precipitation of hydrides. ii) Uniformly distributedhydrides simulating a situation in whish hydrides starts toprecipitate and iii) Massive surface hydride claimed to be themain cause of accelerated oxidation. Based on the resultsobtained, it is concluded that the oxidation of massivezirconium hydride resembles the oxidation of zirconium metal.This fact clearly shows that accelerated oxidation of zirconiumalloys cannot be due solely to the presence of a massivehydride layer, but also requires a combined effect offorexample interfacial roughness and hydride precipitation.</p><p><b>Keywords:</b>Zircaloy, Zirconium alloys, Oxidation, Oxidelayer, Pre-Transition, Hydriding, Pre-Hydrided, Hydrides,Lithium Hydroxide (LiOH), Lithiated Water, Dissolution, CrossSectional TEM</p>

科学研究費補助金 研究種目:基盤研究(A)(2) 課題番号:07558177 研究代表者:菅井 秀郎 研究期間:1995-1997年度

This master's thesis deals with alkaline battery characteristics and it has special consideration of nickel-cadmium cells. There are three main experimental parts in this paper. First one is concerned with positive electrode materials properties and is aimed to investigate impact of magnesium ions formed into nickel hydroxide electrode structure. Second part deals with battery charging/discharging and response measurement tool design. National Instruments hardware PXI modules for data acquisition was used and program in LabView environment was made. Last one is concerned with nickel-cadmium cell properties changes during increased temperature stressing. Investigation of cell self-charge changes during lithium hydroxide addition into electrolyte was made.