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Multi-element stream sediment reconnaissance in the Hess River region of the Eastern Yukon has outlined an extensive area characterized by anomalously high molybdenum values. An accessible region in the Hess Mountains, within the high molybdenum zone, was selected for detailed study of trace element levels in stream sediment, rock, soil and vegetation. In view of the frequently observed relationship between high forage molybdenum concentrations and the incidence of copper deficiency in cattle, molybdenum concentrations in plant species likely to be consumed by caribou and moose were of particular interest. High sediment molybdenum values are characteristic of catchments underlain by dark shales and less commonly dark limestone. These rocks and associated soils are rich in molybdenum. Concentrations in vegetation growing on anomalous shaly soils are characteristically low, while most plants growing on soils derived predominantly from limestone are molybdenum-rich. The Mo-Cu status of vegetation on limey soils is typically within the range associated with molybdenum induced hypocuprosis in cattle. Low molybdenum uptake by plants on soils derived from shales likely reflects the unavailability of the molybdate anion, resulting from its adsorption onto clay minerals and sesquioxides under acidic conditions prevalent in these soils. In neutral to mildly basic environments, typical of dark limestone soils, molybdenum adsorption is greatly decreased, and therefore molybdenum is relatively available to plants. In the detailed study area soil pH values are typically similar to pH levels in associated stream water. Therefore by combining stream sediment molybdenum concentrations with stream pH data, catchments likely to contain molybdenum-rich vegetation can be predicted. Unfortunately stream pH values were not obtained in the regional survey. In view of the apparent rarity of dark limestone throughout the Eastern Yukon, however, molybdenum-rich vegetation is not likely to be particularily widespread. Wildlife in this area, therefore, is probably not significantly affected by molybdenum induced copper deficiency. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

My work presents a novel approach to fabricate binder free three-dimensional carbon nanotubes/sulfur (3DCNTs/S) hybrid composite by a facile and scalable method increasing the loading amount from 1.86 to 8.33 mg/cm2 highest reported to date with excellent electrochemical performance exhibiting maximum specific energy of ~1233Wh/kg and specific power of ~476W/kg, with respect to the mass of the cathode. Such an excellent performance is attributed to the fact that 3DCNTs offers higher loading amount of sulfur, and confine polysulfide within the structure. In second part of the thesis, molybdenum disulfide (MoS2) is typically studied for three electrochemical energy storage devices including supercapacitors, Li-ion batteries, and hybrid Li-ion capacitors. The intrinsic sheet like morphology of MoS2 provides high surface area for double layer charge storage and a layered structure for efficient intercalation of H+/ Li+ ions. My work demonstrates the electrochemical analysis of MoS2 grown on different substrates including copper (conducting), and carbon nanotubes. MoS2 film on copper was investigated as a supercapacitor electrode in three electrode system exhibiting excellent volumetric capacitance of ~330F/cm3 along with high volumetric power and energy density in the range of 40-80 W/cm3 and 1.6-2.4 mWh/cm3, respectively. Furthermore, we have developed novel binder-free 3DCNTs/ MoS2 as an anode materials in half cell Li-ion batteries. The vertically oriented morphology of MoS2 offers high surface area and active electrochemical sites for efficient intercalation of Li+ ions and demonstrating excellent electrochemical performance with high specific capacity and cycling stability. This 3DCNTs/ MoS2 anode was coupled with high surface area southern yellow pine derived activated carbon (SYAC) cathode to obtain hybrid 3DCNTs/ MoS2 || SYAC Li-ion capacitor (LIC), which delivers large operating voltage window of 1-4.0V with excellent cycling stability exhibiting capacitance retention of ~80% after 5000 cycles.

LD2668 .T4 1962 P34

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