Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 72-74). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Lau, Fong Ting. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 73-77). / Abstracts in English and Chinese. / ABSTRACT --- p.III / 摘要 --- p.IV / PUBLICATIONS CORRESPOND TO THIS THESIS --- p.V / ACKNOWLEDGEMENT --- p.VI / TABLE OF CONTENTS --- p.VIII / LIST OF FIGURES --- p.X / LIST OF TABLES --- p.XII / Chapter CHAPTER I. --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Unique Properties of Gold Nanoparticles Possess --- p.1 / Chapter 1.1.2 --- Synthesis of Gold Nanoparticles --- p.3 / Chapter 1.1.3 --- Aggregation or Agglomeration of Gold Nanoparticles --- p.4 / Chapter 1.1.4 --- Fabrication of Well-ordered Structures Using Gold Nanoparticles --- p.6 / Chapter 1.2 --- Objective --- p.7 / Chapter 1.3 --- Organization --- p.9 / Chapter CHAPTER II. --- ARCHITRCTURE OF AUTOMATED MICRO-ROBOTIC SPOTTING SYSTEM --- p.10 / Chapter 2.1 --- Micro-sized Capillary Probes --- p.12 / Chapter 2.1.1 --- Importance of Fabrication of Micron-sized Capillary Probe Tip --- p.12 / Chapter 2.1.2 --- Experimental Procedure of Fabrication of Capillary Probe --- p.14 / Chapter 2.1.3 --- Experimental Result of Fabrication of Capillary Probe --- p.15 / Chapter 2.2 --- Programmable X-Y-Z Manipulator --- p.16 / Chapter 2.3 --- Programmable Hydraulic Syringe Pump --- p.16 / Chapter 2.4 --- CCD Video Microscope System --- p.17 / Chapter 2.5 --- Chapter Conclusion --- p.17 / Chapter CHAPTER III. --- MANIPULATION OF UNMODIFIED GOLD NANOPARTICLES BY DIELECTROPHORESIS --- p.18 / Chapter 3.1 --- Methodology of Manipulation of Gold Nanoparticles --- p.18 / Chapter 3.1.1 --- Self-assembly of Crystals by Capillary Force Induced by Solvent Evaporation --- p.19 / Chapter 3.1.2 --- Position Control by Dielectrophoretic (DEP) Force --- p.21 / Chapter 3.2 --- Experimental Preparation and Setup --- p.22 / Chapter 3.2.1 --- Microelectrodes Fabrication --- p.22 / Chapter 3.2.2 --- Circuit --- p.23 / Chapter 3.2.3 --- Injection of Solution by Microspotting Technique --- p.24 / Chapter 3.3 --- Experimental Procedure --- p.24 / Chapter 3.4 --- Experimental Result --- p.24 / Chapter 3.4.1 --- Process of Crystal Formation by Combining the Capillary Force and DEP --- p.24 / Chapter 3.4.2 --- Position of Crystal Formed between Microelectrodes --- p.25 / Chapter 3.4.3 --- Yield of Crystal Formed between Microelectrodes by Varying Voltage Applied --- p.27 / Chapter 3.5 --- Surface Analyses --- p.29 / Chapter 3.5.1 --- Scanning Electron Microscopy and Energy-Disperse X-ray Spectroscopy Analysis --- p.30 / Chapter 3.5.2 --- Atomic Force Microscope Analysis --- p.31 / Chapter 3.6 --- Possibilities served as Humidity Sensors --- p.33 / Chapter 3.7 --- Chapter Conclusion --- p.35 / Chapter CHAPTER IV. --- THEORETICAL ANALYSES OF GOLD NANOPARTICLES MANIPULATION --- p.37 / Chapter 4.1 --- Structure of Gold nanoparticles - Presence of Stabilizing Ions --- p.37 / Chapter 4.2 --- Theoretical Force Analysis Acting on Gold Nanoparticles --- p.39 / Chapter 4.2.1 --- Governing Equations --- p.39 / Chapter 4.2.2 --- Experimental Analysis --- p.45 / Chapter 4.3 --- Concentration of Gold Nanoparticles in Gold Colloidal Solution --- p.47 / Chapter 4.4 --- Chapter Conclusion --- p.48 / Chapter CHAPTER V. --- MODIFICATION OF GOLD NANOPARTICLES SURFACE --- p.50 / Chapter 5.1 --- Working Principle of Surface Modification of Gold Nanoparticles --- p.50 / Chapter 5.2 --- Criteria of Choosing the Adsorbed Molecules for Chemisorption --- p.52 / Chapter 5.3 --- Experimental Procedures of Surface Modifications --- p.54 / Chapter 5.4 --- Experimental Result of Surface Modification of Gold Nanoparticles --- p.58 / Chapter 5.4.1 --- Effect of Concentration of Dodecanethiol --- p.58 / Chapter 5.4.2 --- Stability of Surface Modified Gold Nanoparticles --- p.59 / Chapter 5.5 --- Chapter Conclusion --- p.61 / Chapter CHAPTER VI. --- MANIPULATION OF MODIFIED GOLD NANOPARTICLES BY DIELECTROPHORESIS --- p.62 / Chapter 6.1 --- Experimental Setup --- p.62 / Chapter 6.2 --- Experimental Result --- p.63 / Chapter 6.2.1 --- Comparison between Modified and Unmodified Gold Nanoparticles --- p.63 / Chapter 6.2.2 --- Manipulation Experiments using Different Frequency --- p.64 / Chapter 6.3 --- PDMS Microfluidic Channel System --- p.68 / Chapter 6.3.1 --- System Design --- p.68 / Chapter 6.3.2 --- Fabrication --- p.68 / Chapter 6.4 --- Chapter Conclusion --- p.69 / Chapter CHAPTER VII. --- CONCLUSION --- p.71 / BIBLIOGRAPHY --- p.73

ZrN has been identified as a candidate material for use as an inert matrix fuel host for the transmutation of plutonium and minor actinides. These materials will be subjected to large amounts of different types of radiation within the nuclear reactor core. The types of radiation include fission fragments and alpha-particles amongst others. Recent studies suggest that nanocrystalline material may have a higher radiation tolerance than their polycrystalline and bulk counterparts. Some studies have shown that swift heavy ion irradiation may also significantly modulate hydrogen and helium behaviour in materials. This phenomenon is also of considerable practical interest for inert matrix fuel hosts, since these materials accumulate helium via (n,) reactions and will also be subjected to irradiation by fission fragments. The aim of this investigation is therefore to study the effects of fission fragment and alpha particle irradiation on nanocrystalline ZrN. In an effort to simulate the effects of fission fragments on nanocrystalline zirconium nitride different layers (on a Si substrate) of various thicknesses (0.1, 3, 10 and 20 μm) were irradiated with 167 MeV Xe, 250 MeV Kr and 695 MeV Bi ions to fluences in the range from 31012 to 2.61015 cm-2 for Xe, 1×1013 to 7.06×1013 cm-2 for Kr and 1012 to 1013 cm-2 for Bi. The purpose of this irradiation is to simulate the effects of fission fragments on nanocrystalline ZrN. In order to simulate the effects of alpha particles and the combined effects of alpha particles and fission fragments on nanocrystalline ZrN it was irradiated with 30 keV He to fluences between 1016 and 5×1016 cm-2, 167 MeV Xe to fluences between 5×1013 and 1014 cm-2 and also 695 MeV Bi to a fluence of 1.5×1013 cm-2. He/Bi and He/Xe irradiated samples were annealed at temperatures between 600 and 1000 °C. The different irradiated layers were subsequently analysed via X-ray diffraction (XRD), μ-Raman, transmission electron microscopy (TEM) and nano indentation hardness testing (NIH) techniques. XRD, TEM, μ-Raman and NIH results indicate that ZrN has a very high tolerance to the effects of high energy irradiation. The microstructure of nanocrystalline ZrN remains unaffected by electronic excitation effects even at a very high stopping power. TEM and SEM results indicated that post irradiation heat treatment induces exfoliation at a depth that corresponds to the end-of-range of 30 keV He ions. Results from He/Xe irradiated samples revealed that electronic excitation effects, due to Xe ions, suppress helium blister formation and consequently the exfoliation processes. He/Bi samples however do not show the same effects, but this is possibly due to the lower fluence of Bi ions. This suggests that nanocrystalline ZrN is prone to the formation of He blisters which may ultimately lead material failure. These effects may however be mitigated by electronic excitation effects from certain SHIs.

This thesis describes the characterization of the particle size distribution of cellulose nanocrystals (CNC), the synthesis and characterization of fluorescent CNCs, and the development of a fluorescence microscopy method to probe the distribution of fluorescent CNCs in polymer composites. In this thesis, several methods are used to characterize the size of CNC particles. Size distribution measurements by single particle counting methods (Transmission electron microscopy, Atomic force microscopy) are compared to an ensemble method, Dynamic lighting scattering (DLS) and differences between the various methods will be discussed. The effect of sonication on the CNC size distributions measured by AFM and DLS is examined. Furthermore, a reliable and reproducible method for re-dispersing dry CNC powder will be explored in this chapter since CNC is often stored in a dry environment due to its stability. Rhodamine B isothiocyanate (RBITC) and 5-(4,6-dichlorotriazinyl) amino fluorescein (DTAF) were selected for labelling CNCs. These dyes have the advantage of being cheap and readily available and compatible with relatively simple synthetic chemistry. The photophysical properties of all dye labeled CNCs were studied in more detail than in previous studies. The focus is on understanding the most appropriate labeling efficiency to maximize the ability to detect individual CNCs while minimizing the amount of dye used to avoid modifying the CNC properties. The characterization methods include ensemble methods such as UV-Vis absorption and scattering measurements, fluorescence spectroscopy and single molecule methods such as Total internal reflection fluorescence microscopy (TIRFM), Atomic force microscopy (AFM) and correlated TIRFM/AFM measurements. All of these methods have their advantages and disadvantages. After characterization, the most suitable dye labeled CNC sample was selected for development of a fluorescence microscopy method to characterize CNC distribution in CNC/polymer composites. The dye labeled CNC has been incorporated into polyvinyl alcohol (PVA) films and studied by fluorescence microscopy. These experiments demonstrated that the level of CNC agglomeration varies significantly for different film preparation methods, indicating that fluorescence microscopy is a useful and easily accessible method for optimizing film preparation. The self-quenching of the dye in the film was also measured and discussed and is an important consideration for choice of the dye loading and CNC content in the films.

Cellulose nanocrystals (CNCs) are rod-shaped nanoparticles derived from cellulose, the most abundant polymer in the world. CNCs are as strong as Kevlar™, have a high aspect ratio (traditional nanoparticles are spherical) and thus, a higher surface area, which makes them ideal for use in nanocomposites. In addition, CNCs are considered the only safe nanomaterial according to Health Canada. In this thesis, CNCs were used to produce nanocomposites via in situ semi-batch emulsion polymerization. The target application for these nanocomposites was as pressure sensitive adhesives (PSAs). In the past, CNCs have been blended with polymers rather than added in situ. Emulsion polymerization is considered a more sustainable method to synthesize polymers compared to say, solution polymerization. However, adhesives synthesized using this method tend to have a lower shear strength due to poor gel network formation. As a result, conventional emulsion-based PSAs suffer from the inability to increase certain adhesive properties (e.g., tack and peel strength) while simultaneously increasing shear strength. In this thesis, we demonstrate how the use of CNCs via in situ emulsion polymerization overcomes this classic problem. Two polymer systems were tested: isobutyl acrylate (IBA)/n-butyl acrylate (BA)/methyl methacrylate (MMA) and 2-ethylhexyl acrylate (EHA)/BA/MMA. The use of CNC with IBA, a relatively hydrophilic monomer, rather than with EHA, a highly hydrophobic monomer, resulted in the simultaneous improvement of tack, peel strength and shear strength of the PSA films. Dynamic mechanical analysis (DMA) also indicated improved storage and loss moduli with increasing CNC content, further supporting the reinforcing effect of the CNCs within the PSA. EHA followed similar trends as IBA for conversion, particle size, viscosity, pH, glass transition temperature and gel content. On the other hand, the use of CNC with EHA yielded less improvement in adhesive properties due to poor dispersion of the CNCs because of the hydrophobic repulsion by the EHA.

No description available.

Cellulose nanocrystals (CNCs) are an ideal reinforcing agent for polymer nanocomposites because they are lightweight, nano-sized, and have a high elastic modulus. To date, using cellulose nanocrystals in common matrices has been generally unsuccessful due to their hydrophilicity and incompatibility with hydrophobic polymers. To overcome the poor compatibility, we have grafted poly(methyl methacrylate) (PMMA) onto the surface of the nanocrystals for the first time using a one-pot, aqueous in-situ “grafting from” polymerization reaction with ceric ammonium nitrate initiator to produce poly(methyl methacrylate)-grafted-cellulose nanocrystals (PMMA-g-CNCs). We compared the compounding of CNCs and modified CNCs with PMMA using two processing methods; melt mixing and wet ball milling. We examined the morphological, mechanical and rheological behaviour of the nanocomposites and found that ball milled composites had lower mechanical and rheological performance compared to melt mixed composites for both CNCs and modified CNCs. Additionally, we found that high (>1 wt. %) loadings of CNCs had a positive effect on the performance of nanocomposites, while low loadings of CNCs and all loadings of PMMA-g-CNCs had no net effect on the performance of the nanocomposites compared to the control. The morphology of nanocomposites showed some agglomeration in the samples with CNCs, but more pronounced agglomeration in samples with PMMA-g-CNCs. This is consistent with the decreased rheological and mechanical behaviour of composites with PMMA-g-CNCs compared with CNCs. / Thesis / Master of Applied Science (MASc)

No description available.