Volatiles are fundamental to many aspects of kimberlite magmatism. However, the volatile compositions and concentrations are poorly defined. Enrichment of H in kimberlitic olivines, many of which are xenocrysts, suggests high water content, but the extent to which H exchanges between these xenocrysts and kimberlite magmas remains unclear. This study investigates zonation of H in kimberlite-hosted xenolith and macrocrystic olivines using Fourier transform infrared spectroscopy to constrain the extent of re-equilibration. Data show that, depending on locality, xenolith olivines exhibit either no H-zonation, or substantial H-depletion in their rims. Macrocrysts feature similar trends to xenolith olivines from the same intrusion. In terms of the rim:core ratio of H, strongly zoned olivines average ~0.5, whereas poorly zoned olivines average at ~0.9 (macrocrysts) or 1.0 (xenolith olivines). Locality-specific H-zonation could result from different magmatic thermal regimes, water concentrations, or ascent durations. If the magmas that contained weakly zoned olivines were anhydrous, their restricted zoning requires ascent durations (< 20 min at 1100 °C) that are considerably shorter than published estimates (~1-24 hr at 1100 °C). These findings suggest that elevated magmatic water concentrations minimized loss of H from olivine in these kimberlites, showing that non-equilibrated xenocrysts could indirectly record high water concentrations in the form of weak H-zonation. Strong H-depletion patterns in olivines from other kimberlites may reflect lower initial magmatic water concentrations, or loss of fluid to country rocks. Future studies could compare H-zonation to temperature and ascent rate estimates, and field relationships to better elucidate the causes of locality-specific H-zonation. An apparent correlation between diamond grade and H-zonation warrants further investigation. / This thesis includes an Electronic Appendix, available at http://dalspace.library.dal.ca

Thesis (Ph.D.) - University of St Andrews, April 2007.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第17974号 / 医博第3838号 / 新制||医||1001(附属図書館) / 80818 / 京都大学大学院医学研究科医学専攻 / (主査)教授 羽賀 博典, 教授 坂井 義治, 教授 千葉 勉 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Detailed understanding of bubbles growing on a solid surface is a fundamental requirement in many technological domains, with particular application to water electrolysis in relation to the present-day socio-economic significance of clean energy transition. Evolution of bubbles at the electrode surface greatly determines the overall efficiency and throughput of an electrolysis cell. Bubbles residing on the electrode surface creates resistance to the flow of electric current and reduces the active electro-catalytic area. Therefore, fast removal of the bubbles is desirable for efficient operation. With this motivation, this dissertation aims to build deeper understanding of the bubble dynamics during the pre-detachment and detachment stage. To this end, single hydrogen bubbles grown on microelectrodes are chosen as the object of study. Thermocapillary and electric forces acting on an electrolytic bubble are introduced and a thorough account of the forces acting on the bubble is taken. A dynamical model of the bubble motion is developed. By means mathematical and physical modeling of the forces, working mechanism is provided for a novel mode of bubble detachment, namely oscillatory bubble detachment. The model predictions of oscillation parameters are in good correlation with experimental observations. Furthermore, the equation of motion of the bubble is shown to undergo bifurcation thus providing mathematical reasoning behind the existence of different detachment modes. A deeper look is taken specifically at the oscillatory mode. The electrolyte flow velocity is computed and compared with PTV based measurements. Force variation during one oscillation cycle is characterized and correlated with relevant geometric and operational parameters. Based on dynamical conditions of the bubble motion, the surface charge at the bubble interface is quantified. The calculated values match with literature values from bubble electrophoresis experiments. A detailed look is also taken at the effect of electrode size on the thermocapillary effect. The temperature and flow velocity field in the electrolyte is computed for various electrode size. Additional details regarding the flow structure were found. The location of the interfacial temperature hotspot was quantified. The current density distribution along the electrode surface was found to be strongly non-uniform. The Marangoni and the hydrodynamic force acting on the bubble was quantified at various electrode sizes. Further a model was developed to approximate the thermocapillary effect of a bubble on a large electrode. The location of temperature hotspot was found to be different when compared to bubbles on a microelectrode. This influences the Marangoni flow structure and also the Marangoni force on the bubble. Overall, this dissertation provides a systematic framework for characterizing forces acting on the bubble and investigating the dynamics of the bubble motion, which adds to our current understanding of bubble evolution and, takes one step towards predictive detachment models.

This study has focused on solid oxide electrolyser cells for high temperature steam electrolysis. Solid oxide electrolysis is the reverse operation of solid oxide fuel cells (SOFC), so many of the same component materials may be used. However, other electrode materials are of interest to improve performance and efficiency. In this work anode materials were investigated for use in solid oxide electrolysers. Perovskite materials of the form L₁₋ｘSrｘMO₃ , where M is Mn, Co, or Fe. LSM is a well understood electrode material for the SOFC. Under electrolysis operation LSM performed well and no interface reactions were observed between the anode and YSZ electrolyte. LSM has a relatively low conductivity and the electrode reaction is limited to the triple phase boundary regions. Mixed ionic-electronic conductors of LSCo and LSF were investigated, with these materials the anode reaction is not limited to triple phase boundaries. The LSCo anode had adherence problems in the electrolysis cells due to the thermal expansion coefficient mismatch with the YSZ electrolyte. The LSCo reacted with the YSZ at the anode/electrolyte interface forming insulating zirconate phases. Due to these issues the LSCo anode cells performed the poorest of the three. The performance of electrolysis cells with LSF anode exceeded both LSM and LSCo, particularly under steam operation, although an interface reaction between the LSF anode and YSZ electrolyte was observed. In addition to the anode material studies this work included the development of solid oxide electrolyser tubes from tape cast precursor materials. Tape casting is a cheap processing method, which allows for co-firing of all ceramic components. The design development resulted in a solid design, which can be fabricated reliably, and balances strength with performance. The design used LSM anode, YSZ electrolyte, and Ni-YSZ cathode materials but could easily be adapted for the use of other component materials. Proper sintering rates, cathode tape formulation, tube length, tape thickness, and electrolyte thickness were factors explored in this work to improve the electrolyser tubes.

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