This thesis describes the transport properties observed in thermally treated graphite oxide (GO), which holds promise as an economical route to obtaining graphene. Graphene is a material consisting of a single atomic plane of carbon atoms and was first isolated as recently as 2004. Several isolation techniques have been investigated, including mechanical exfoliation, chemical vapor deposition, and the reduction (by various methods) of chemically synthesized graphite oxide. Two fundamental questions are pursued in this work. The first is concerned with the maximum electrical conductivity that can be achieved in atomically thin reduced graphite oxide samples (rGO). As produced, GO is insulating and of little use electronically. By heating and exposure to reducing atmospheres, however, the conductivity can be increased. Through the lithographic definition and fabrication of four-point contact structures atop microscopic samples of GO, the resistance of the sample can be monitored in situ as the reduction process takes place. It was discovered that the resistance of few-layer GO could be decreased by an order of magnitude when heated to 200 °C and subsequently cooled back to room temperature in forming gas. Final resistivities were on the order of 0.5 Ω-cm. An ambipolar field effect was observed in the thermally treated samples, with resistance decreasing by up to 16 % under a substrate bias of ±20 V. Mobilites were inferred to be on the order of 0.1 cm²/V-s. It was also found that the presence of forming gas during reduction decreased the resistance of the GO samples by roughly one half. The second question that this work begins to answer is concerned with the distance that electrons can travel in such thermally-reduced GO before spin-randomizing scattering. The answer can be elucidated with the aid of magnetoresistance measurements using ferromagnetic contacts to inject a spin-polarized current through the sample. The observation of the magnetoresistive effect with the contacts separated by a certain distance can be taken as evidence of a spin coherence length in the material of at least that distance. Though this experiment has not yet been carried out, progress has been made toward its possibility; specifically in the fabrication and characterization of independently switchable magnetic contacts. By exploiting magnetic shape anisotropy, contact pairs have been fabricated and demonstrated to differ in magnetic coercivity by up to 8 Oe. / Graduation date: 2011

Lithium-ion battery is attractive for various applications because of its high energy density. The performance of Li-ion battery is influenced by several properties of the electrode materials such as particle size, surface area, ionic and electronic conductivity, etc. Porosity is another important property of the electrode material, which influences the performance. Pores can allow the electrolyte to creep inside the particles and also facilitate volume expansion/contraction arising from intercalation/deintercalation of Li+ ions. Additionally, the rate capability and cycle-life can be enhanced. The following porous electrode materials are investigated. Poorly crystalline porous -MnO2 is synthesized by hydrothermal route from a neutral aqueous solution of KMnO4 at 180 oC and the reaction time of 24 h. On heating, there is a decrease in BET surface area and also a change in morphology from nanopetals to clusters of nanorods. As prepared MnO2 delivers a high discharge specific capacity of 275 mAh g-1 at a specific current of 40 mA g-1 (C/5 rate). Lithium rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template. It has a well crystalline structure with a broadly distributed mesoporosity but low surface area. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g-1 is obtained at a discharge current of 30 mA g-1. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g-1 at a discharge current density of 30 mA g-1. Solid solutions of Li2MnO3 and LiMO2 (M=Mn, Ni, Co, Fe and their composites) are more attractive positive electrode materials because of its high capacity >200 mAh g-1.The solid solutions are prepared by microemulsion and polymer template route, which results in porous products. All the solid solution samples exhibit high discharge capacities with high rate capability. Porous flower-like α-Fe2O3 nanostructures is synthesized by ethylene glycol mediated iron alkoxide as an intermediate and heated at different temperatures from 300 to 700 oC. The α-Fe2O3 samples possess porosity with high surface area and deliver discharge capacity values of 1063, 1168, 1183, 1152 and 968 mAh g-1 at a specific current of 50 mA g-1 when prepared at 300, 400, 500, 600 and 700 oC, respectively. Partially exfoliated and reduced graphene oxide (PE-RGO) is prepared by thermal exfoliation of graphite oxide (GO) under normal air atmosphere at 200-500 oC. Discharge capacity values of 771, 832, 1074 and 823 mAh g -1 are obtained with current density of 30 mA g-1 at 1st cycle for PE-RGO samples prepared at 200, 300, 400 and 500 oC, respectively. The electrochemical performance improves on increasing of exfoliation temperature, which is attributed to an increase in surface area. The high rate capability is attributed to porous nature of the material. Results of these studies are presented and discussed in the thesis.