Thesis (Ph. D.)--University of Sydney, 2007. / Title from title screen (viewed 15 January 2009). Includes five published papers co-authored by Yu, Mai, Zang and others. Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Department of Mechanical Engineering, School of Aerospace, Mechanical and Mechatronic Engineering, Faculty of Engineering and Information Technologies. Includes bibliographical references. Also available in print form.

Graphene has grabbed enormous research attention due to its multiple unique properties. These properties, however, can be strongly influenced by lattice imperfections. Aberration corrected transmission electron microscopy (AC-TEM) is one of the leading methods to image two-dimensional materials at the atomic level. This thesis addresses the issue of structure and dynamics characterization of dislocations and grain boundaries (GBs) in graphene with single atom sensitivity using the state-of-the-art AC-TEM in Department of Materials, University of Oxford. My first goal is to understand the interaction between dislocation and the edge of graphene. When a dislocation is located near an edge, a decrease in the rippling and increase of the in-plane rotation occurs relative to the dislocations in the bulk. The increased in-plane rotation near the edge causes bond rotations at the edge of graphene to reduce the overall strain in the system. Dislocations are highly stable and remain fixed in their position even when located within a few lattice spacings from the graphene edge. With the aid of an in situ heating holder, the high temperature behavior of dislocations is then investigated. Control of temperature enables the differentiation of electron beam induced effects and thermally driven processes. An analysis of the dislocation movement shows both climb and glide processes, including new complex pathways for migration and large nanoscale rapid jumps between fixed positions in the lattice. The improved understanding of the high temperature dislocation movement provides insights into annealing processes in graphene and the behavior of defects with increased heat. The in situ heterogeneous nucleation and growth of graphene are also studied within the AC-TEM. The growth mechanism consists of alternating carbon cluster attachment and indentation filling to maintain a uniform growth front of lowest energy. The highly polycrystalline graphene seed is found to evolve with time into a higher order crystalline structure. The motion of GBs is discontinuous and mediated by both bond rotation and atom evaporation. These results provide insights into the formation of crystalline seed domains that are generated during bottom-up graphene synthesis. Finally, the formation, reconfiguration and annihilation of GB loops are demonstrated. It is shown that the GB loop cannot fully relaxed under electron beam irradiation with its terminal state being isolated dislocations far apart from each other. Line defects composed of several adjacent excess-atom defects can be found during the reconfiguration process. This work gives detailed information about the stability and behavior of large GB loops in two dimensional materials.

Kou, Xiaoshan = 納米金的形成和顏色 / 寇曉珊. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 165-177). / Text in English; abstracts in English and Chinese. / Kou, Xiaoshan = Na mi jin de xing cheng he yan se / Kou Xiaoshan. / Abstract --- p.i / 摘要 --- p.iv / Acknowledgement --- p.vi / Table of Contents --- p.viii / List of Figures --- p.xi / List of Tables --- p.xviii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Noble metal nanostructures and their surface plasmon resonances --- p.1 / Chapter 1.2 --- Applications of noble metal nanostructures --- p.13 / Chapter 1.3 --- Thesis outline --- p.20 / Chapter 2 --- Characterization Techniques and Instrumentation --- p.23 / Chapter 3 --- Growth of Large-Aspect-Ratio Gold Nanorods --- p.26 / Chapter 3.1 --- Overview --- p.26 / Chapter 3.2 --- Synthesis of surfactants and gold nanorods --- p.30 / Chapter 3.3 --- Surfactant effects on the growth of gold nanorods --- p.32 / Chapter 3.4 --- Summary --- p.54 / Chapter 4 --- Tailoring Plasmonic Properties of Gold Nanorods --- p.56 / Chapter 4.1 --- Overview --- p.56 / Chapter 4.2 --- Anisotropic shortening of gold nanorods --- p.60 / Chapter 4.3 --- Transverse overgrowth on gold nanorods --- p.70 / Chapter 4.4 --- Comparison between shortened and overgrown gold nanorods --- p.81 / Chapter 4.5 --- Summary --- p.97 / Chapter 5 --- Gold Bipyramids --- p.99 / Chapter 5.1 --- Overview --- p.99 / Chapter 5.2 --- FDTD calculation on gold bipyramids and nanorods --- p.101 / Chapter 5.3 --- Growth of gold bipyramids --- p.108 / Chapter 5.4 --- Shortening of gold bipyramids --- p.115 / Chapter 5.5 --- Comparison of the oxidation behaviors between gold bipyramids and nanorods --- p.125 / Chapter 5.6 --- Summary --- p.127 / Chapter 6 --- End to End Assembly of Gold Nanostructures --- p.129 / Chapter 6.1 --- Overview --- p.129 / Chapter 6.2 --- Experimental methods --- p.131 / Chapter 6.3 --- Assembly of gold nanorods --- p.132 / Chapter 6.4 --- Assembly of gold nanorod-nanosphere pairs --- p.135 / Chapter 6.5 --- Assembly of gold bipyramid-nanosphere pairs --- p.138 / Chapter 6.6 --- Control experiments --- p.140 / Chapter 6.7 --- Summary --- p.143 / Chapter 7 --- Shape- and Size-Dependent Refractive Index Sensitivities of Gold Nanoparticles --- p.145 / Chapter 7.1 --- Overview --- p.145 / Chapter 7.2 --- "Growth of gold nanospheres, nanocubes, nanobranches, nanorods, and bipyramids" --- p.147 / Chapter 7.3 --- Refractive index sensitivities measurement --- p.149 / Chapter 7.4 --- Refractive index sensitivities of gold nanoparticles --- p.149 / Chapter 7.5 --- Summary --- p.159 / Chapter 8 --- Conclusions --- p.161 / References --- p.165

Philosophiae Doctor - PhD / This work entails the preparation of various polyanilines with different morphologies and their application in photovoltaic solar cells. Zinc oxide (ZnO) with one-dimensional and flower-like morphology was also prepared by microwave irradiation and used as electron acceptors in photovoltaics devices. The morphological, structural, spectroscopic and electrochemical characteristics of these materials were determined by scanning electron microscopy (SEM), X-Ray diffraction (XRD), Raman, Fourier-transformed infrared spectroscopy (FTIR), ultraviolet and visible spectroscopy (UV-Vis), photoluminescence(PL), thermal gravimetric analysis (TGA) and cyclic voltammetry (CV) experiments. Devices fabricated from these materials were characterized under simulated AM 1.5 at 800 mW. / South Africa

Zinc oxide (ZnO) crystal with a direct wide band gap (3.37 eV) and large excition binding energy (60 meV) is one of the most potential semiconductors in numerous application fields such as room-temperature UV-Iaser, light-emitting- diode (LED), photocatalyst, gas sensor, solar cell, piezoelectric device, etc. In past decades, different methods have been investigated to produce a variety of different shapes of nano and submicron ZnO nanostructures. Among them, the ZnO nanobelts (NBs) with a rectangular cross section have unique optoelectronic properties due to its unusual shape and structure. It is well demonstrated by recent success in field-effect transistor, nanoresonator, and spintronics applications of the ZnO NBs. Two-dimensional (2D) nanostructures such as nanosheets (NSs) and thin films have also great potential for unique purposes where a large uniform coverage at nanoscale is essential. One of the conventional methods for synthesis of the ZnO nanostructures is vapour transport and condensation process at high temperature, in some cases up to 1400°C. Such an extreme condition for vaporization of precursor could induce many oxygen defects on surface of the ZnO nanobelts. These specific defects hinder progress to the applications of ZnO in optoelectronic and lasing devices. In this respect, mild processing is strongly demanded for the synthesis of the ZnO nanoparticles. In terms of low energy consumption and simplicity, soft- solution process based on hydrothermal reactions at low temperature (under 100°C) is a green chemical procedure. However, there are only few reports on the synthesis of the ZnO NBs and NSs due to their unusual growth habit against typical growth rate of the ZnO crystal. Here we are reporting a developed simple, low cost and high yield hydrothermal technique to synthesis layered basic zinc acetate (LBZA) NBs and also a novel rapid microwave-assisted hydrothermal technique to grow LBZA NSs only in 2 minutes. Growth procedures are followed by pyrolytic decomposition to produce nanocrystalline NBs and NSs. SEM and AFM results revealed that the morphology and quantity of the nanobelts and nanosheets are strongly temperature and pH dependent. In addition, results showed that as-grown LBZA nanostructures could be easily transformed to corresponding ZnO nanostructures through pyrolytic decomposition without.

Magister Scientiae - MSc / The objective of this research was to develop highly efficient and yet effective MnO2 electrode materials for supercapacitors applications. Most attention had focussed on MnO2 as a candidate for pseudo-capacitor, due to the low cost of the raw material and the fact that manganese is more environmental friendly than any other transition metal oxide system. The surface area and pore distribution of MnO2 can be controlled by adjusting the reaction time. The MnO2 synthesised under optimum conditions display high capacitance, and exhibit good cycle profile. This work investigates the ways in which different morphological structures and pore sizes can affect the effective capacitance. Various -MnO2 were successfully synthesised under low temperature conditions of 70 oC and hydrothermal conditions at 120 oC. The reaction time was varied from 1 to 6 hours to optimise the conditions. KMnO4 was reduced by MnCl.H2O under low temperature, whereas MnSO4.4H2O, (NH4)2S2O8 and (NH4)2SO4 were co-precipitated under hydrothermal conditions in a taflon autoclave to synthesise various -MnO2 nano-structures. / South Africa

No description available.

The objective of this thesis is to present a modelling and simulation study for the mechanics of PNs with an emphasis placed on the unique features of PNs due to the piezoelectric and small scale effects.

Thesis (Ph.D.) -- University of Texas at Arlington, 2008.

Thesis (Ph. D.)--Missouri University of Science and Technology and University of Missouri--St. Louis, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 28, 2008) Thesis completed as part of a cooperative degree program with Missouri University of Science & Technology and the University of Missouri--St. Louis. Includes bibliographical references (p. 129-142).