Wang Juan = 納米金顆粒與氧化鋁複合物薄膜光學吸收譜中的尺寸和濃度效應 / 王娟. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 55-58). / Text in English; abstracts in English and Chinese. / Wang Juan = Na mi jin ke li yu yang hua lv fu he wu bo mo guang xue xi shou pu zhong de chi cun he nong du xiao ying / Wang Juan. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgment --- p.iii / Table of contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.ix / Chapter CHAPTER 1: --- Introduction --- p.1 / Chapter CHAPTER 2: --- Background --- p.3 / Chapter 2.1 --- Optical response of metal-particle/matrix composite system in an electronic field --- p.3 / Chapter 2.1.1 --- The concept of plasmon and the dielectric function of metal particle --- p.3 / Chapter 2.1.2 --- The concept of surface plasmon resonance --- p.4 / Chapter 2.2 --- The theories describing the optical absorption properties of metal particle/matrix composite system --- p.5 / Chapter 2.2.1 --- The Mie theory --- p.5 / Chapter 2.2.2 --- The Maxwell-Garnett (M.G.) effective medium theory --- p.6 / Chapter 2.3 --- Previous experimental works in the field --- p.7 / Chapter CHAPTER 3: --- Experimental and instrumentation --- p.8 / Chapter 3.1 --- Fabrication of the Au-nanoparticle /A12O3-matrix composite thin films --- p.11 / Chapter 3.1.1 --- Sputtering techniques and radio-frequency magnetron sputtering --- p.11 / Chapter 3.1.2 --- Experimental set up and the deposition process --- p.13 / Chapter 3.2 --- The chemical and structural characterizations of the films --- p.14 / Chapter 3.2.1 --- X-ray Photoelectron Spectroscopy (XPS) --- p.14 / Chapter 3.2.2 --- X-ray Diffraction (XRD) --- p.15 / Chapter 3.2.3 --- Transmission Electron Microscopy (TEM) --- p.17 / Chapter 3.3 --- The optical absorption measurement: UV spectrometer --- p.21 / Chapter CHAPTER 4: --- Results and discussions --- p.23 / Chapter 4.1 --- General description of the as-prepared samples --- p.23 / Chapter 4.1.1 --- Chemical composition of the films --- p.23 / Chapter 4.1.2 --- General microstructure of the films and the relationship between the deposition parameters --- p.25 / Chapter 4.2 --- The optical absorption: relationship between the SPR absorption and the microstructure --- p.27 / Chapter 4.2.1 --- The shifting of the surface plasmon resonance --- p.27 / Chapter 4.2.1.1 --- The size effect on the SPR frequency shifting --- p.27 / Chapter 4.2.1.2 --- The concentration effect on the SPR frequency shifting --- p.42 / Chapter 4.2.2 --- The broadening of the surface plasmon resonance: size dependence of the relaxation time of free electrons --- p.51 / Chapter CHAPTER 5: --- Conclusions --- p.53 / Appendix --- p.54 / Reference --- p.55

Chapter 1 briefly introduces the theoretical background of the association and dissociation of polymer chains or colloidal particles are briefly introduced, including thermodynamic consideration and viscoelastic effect on the formation of mesoglobular phase in dilute polymer solutions, as well as some basic theories and universal models of fractal aggregates. / Chapter 2 details the theories of static and dynamic laser light scattering (LLS) as well as the instrumental set-up. In addition, the invention and set-up of differential refractometer are briefly discussed. / Chapter 3 summarizes laser light-scattering (LLS) and stopped-flow studies of association of cyclic- and linear-poly( N-isopropylacrylamide) (c-PNIPAM and l-PNIPAM) chains in dilute aqueous solutions. Dynamic and static LLS results reveal that the heating leads to a microphase transition. Resultant structures of interchain aggregates depend on the heating rate and the chain structure. In comparison with l-PNIPAM chains, a slow heating of c-PNIPAM chains in the solution results in stable mesoglobules with a lower average aggregation number, a looser structure and a smaller average size (∼290 nm). The temperature-jump induced association of c -PNIPAM chains in the stopped-flow measurement reveals two kinetic stages; namely, the loose packing of contracted c-PNIPAM chains and further contraction-induced fragmentation of initially packed c-PNIPAM chains due to the lack of interchain entanglements. On the other hand, for l-PNIPAM chains, the intrachain contraction and interchain penetration/entanglement simultaneously occur as the temperatures increases, leading to larger and more compact aggregates whose size increases with the solution temperature. / Chapter 4 discusses the association of water-soluble PNIPAM-monolayer-protected gold particles in dilute dispersions induced by heating the dispersions to different final temperatures higher than the lower critical solution temperature (LCST) of PNIPAM chains via the slow and fast processes. LLS was used to trace and characterize the association process, supplemented by transmission electron microscopy (TEM) measurements. The slow heating-and-cooling cycle reveals that the association and dissociation of PNIPAM-protected gold nanoparticles can be easily induced by altering the solution temperatures and the association and dissociation are fully reversible. Fast heating the dispersion to three different temperatures reveals that both the aggregation rate and average aggregation number increase with the dispersion temperature. Furthermore, the fast heating leads to the formation of fractal aggregates. The fractal dimensions of such formed aggregates continuously increases as the time evolves, which can be ascribed to the simultaneous dissociation that leads to the restructuring and rearrangement of the aggregates, resulting in denser structures. It is interesting to note that the structure of aggregate always remains fractal during the whole process. / Chapter 5 shows how water-dispersible nanosized semiconductor CdS particles (quantum dots, QDs) can be synthesized with a protective layer of covalently grafting linear thermally sensitive PNIPAM chains as well as how these CdS particles can be induced into reversible association and dissociation via an alteration of the dispersion temperature. The formation and fragmentation of these QDs aggregates were systematically investigated by laser light scattering (LLS) and confirmed by transmission electron microscopy (TEM). There exists a hysteresis in one heating-and-cooling cycle. The CdS particles stabilized with shorter PNIPAM chains (Mn = 15,000 g/mol) can associate to form larger and denser spherical aggregates with a much higher aggregation number than those grafted with longer PNIPAM chains ( Mn = 31,000 g/mol) in the heating process. The dissociation (fragmentation) in the cooling process has two stages: initially, the aggregates dissociate as the temperature decreases, and then, the fragmentation stops over a wider temperature range before its final complete dissociation at a lower temperature. We attribute such a two-stage fragmentation to a balanced effect of inter- and intra-chain hydrogen bonding as well as to the hydrophobic interaction between PNIPAM chains and CdS particles. / In this Ph.D. thesis, temperature-induced association and dissociation of various polymeric systems were systematically investigated by a combination of static and dynamic laser light scattering (LLS), supplemented by other methods, such as stopped-flow temperature jump, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). / Ye, Jing. / Adviser: Wu Chi. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3533. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Chua Lai Fei Joseph. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references. / by Chua Lai Fei Joseph. / ACKNOWLEDGMENTS --- p.2 / ABSTRACT --- p.3 / Chapter CHAPTER 1: --- INTRODUCTION --- p.5 / Chapter 1.1 --- METALLIC GLASS --- p.5 / Chapter 1.2 --- SOLIDIFICATION PROCESS OF AN ALLOY --- p.7 / Chapter 1.2.1 --- COOLING PATH --- p.7 / Chapter 1.2.2 --- FREE VOLUME MODEL --- p.8 / Chapter 1.2.3 --- NUCLEATION --- p.9 / Chapter 1.2.4 --- LIQUID PHASE SEPARATION --- p.10 / Chapter 1.3 --- IDEAS ON SOME CHARACTERISTIC PARAMETER OF GLASS AND GLASS FORMING ABILITY OF AN METALLIC ALLOY --- p.11 / Chapter 1.3.1 --- CORRELATION FOR THE EXPANSION COEFFICIENT AND THE GLASS TRANSITION TEMPERATURE --- p.11 / Chapter 1.3.2 --- CORRELATION FOR THE GLASS FORMING ABILITY WITH CRYSTALLINE COMPOUNDS/SOLID-SOLUTIONS --- p.12 / REFERENCES --- p.13 / Chapter CHAPTER 2: --- EXPERIMENTAL --- p.17 / Chapter 2.1 --- SAMPLE PREPARATION --- p.17 / Chapter 2.2 --- EXPERIMENTAL DETAILS FOR ALPHA MEASUREMENT --- p.17 / Chapter 2.3 --- EXPERIMENTAL DETAILS FOR FINDING EQUILIBRIUM PHASES AND GLASS FORMING ABILITY OF AN ALLOY --- p.20 / Chapter 2.3.1 --- FINDING EQUILIBRIUM PHASES --- p.20 / Chapter 2.3.2 --- FINDING GLASS FORMING ABILITY --- p.21 / Chapter CHAPTER 3: --- CORRELATION FOR THERMAL EXPANSION COEFFICIENTS OF MOLTEN GLASS FORMING SYSTEMS --- p.28 / REFERENCES --- p.37 / Chapter CHAPTER 4: --- CORRELATION FOR THE GLASS FORMING ABILITY OF PD83.5-XCUXSI16.5 WITH CRYSTALLINE COMPOUNDS/SOLID- SOLUTIONS --- p.38 / Chapter 4.1 --- INTRODUCTION --- p.39 / Chapter 4.2 --- EXPERIMENTAL --- p.39 / Chapter 4.3 --- RESULTS --- p.41 / Chapter 4.4 --- DISCUSSION --- p.43 / REFERENCES --- p.54 / Chapter CHAPTER 5: --- CONCLUSION --- p.55

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Graduation date: 2004

Graduation date: 2004

By the investigation of the bulk metallic glass-forming liquids that have very low critical cooling rates, the thermodynamics of metallic glasses can be clarified. For studying thermodynamic properties, such as the specific heat capacity, calorimetry (DSC) is utilized and one of the most used instruments is the differential scanning calorimeter. In this study calorimetry was used to investigate the thermodynamics of the Pd������Ni������Cu������P������ alloy. The specific heat capacity of the liquid and crystalline state, enthalpy, entropy, as well as Gibbs free energy difference between the liquid and crystalline state were measured and evaluated in comparison with previous studies of the alloy. The Pd������Ni������Cu������P������ alloy is known as a metallic glass-forming alloy that has high ability for vitrification without crystallization. By observing the onset of heat flux of the exothermic reactions in the DSC, the time-temperature-transformation diagram can be constructed, and the diagram confirms the high ability for the vitrification for the sample. In addition, the effect of fluxing by B���O��� to reduce heterogeneous nucleation is determined by the TTT-diagram. The enthalpy change during the crystallization was directly measured in experiments in which the sample was held isothermally in the DSC. Both enthalpies, calculated from the specific heat capacity measurements and direct measured enthalpy exactly match each other. The very interesting effect in these experiments is an effect of heat treatment in the samples. Two glass transition temperatures can be noticeably recognized by scanning the exothermic event of the sample with the DSC. The material separates into two undercooled liquids. The two phases that are separated during heat treatment can be described by two different fragility parameters. / Graduation date: 2001

A large amount of research has been done in which the magnetocrystalline anisotropy energy for fcc Ni and bcc Fe was calculated based on the electronic structure of these elements. Unfortunately; the results of these studies don't agree with each other and also differ from the experimental observation. In a previous thesis the effects of numerical errors in the Brillouin zone integrations were investigated. The results of that work explain why different calculations give different results, but do not explain the difference with experiment. The conclusion was that the underlying bandstructure, which was calculated using standard approximations, was not correct. The bandstructure of these elements will be different when improved prescriptions for the exchange-correlation energy are used. There is, however, no clear indication along which lines this approximation should be improved. Here we have taken a different approach to change the bandstructure. We suspected that some important interactions between different atomic orbitals are either ignored or miscounted. In this work, we examined the sensitivity of the energy on the interaction between those orbitals and studied in detail the consequences of changes in some interaction parameters which gave rise to a large energy change. The main result of this work is a better understanding of the relation between changes in the electronic structure in k-space and the resultant change in the magnetocrystalline anisotropy energy. In addition, this work takes another step in trying to find a better understanding how the magnetocrystalline anisotropy energy relates to interactions between neighboring atoms. / Graduation date: 2000

Graduation date: 1995

Controlling the orientation and spatial distribution of discontinuous fibers in composite materials enables product properties to be tailored to anticipated use. Electric fields are already (albeit rarely) used to affect alignment in lignocellulosic (LC) fiber composites. The use of magnetic fields has not, however, been suggested or explored; this is apparently because LC fibers are essentially non-magnetic. The approach may offer, however, some considerable advantages, as long as ferromagnetism may be imparted to the fibers. In the present research several fiber modification processes were considered and two, electroless nickel plating and spray application of a coating containing nickel in suspension, were investigated in more depth. The latter was chosen to render highly engineered, elongated wood particles responsive to magnetic fields. Individual treated particles were suspended in viscous, newtonian silicone fluids and their rotation under the influence of a controlled magnetic field was video recorded. The magnetic torque on the particle was, under the above conditions, directly proportional to the fluid viscosity, to the particle's angular velocity and to a characteristic shape constant. The maximum of the specific magnetic torque (magnetic torque divided by the shape constant) was found to reflect the influence of field strength and particle Ni-treatment on rotation. Results were scaled to an arbitrarily chosen viscosity for comparison. The dependencies of the magnetic torque found in the present research compare with those theoretically predicted for ellipsoidal and cylindrical bodies. For field strengths ranging from 0.07T to 0.15T (below magnetic saturation) the magnetic torque increased almost linearly with increasing field strength. Magnetic torque was also found to increase nearly linearly with increasing bulk Ni-concentration (5g/kg - 50g/kg). Rotational motion was sometimes impeded at low field strengths and this was attributed to a permanent magnetic moment obtained by the particle. A coercive field strength of 7600A/m supported this hypothesis. Judiciously switched field polarity increased magnetic torque at small alignment angles. The present research indicates that orienting LC fibers with magnetic fields is possible and promising. To study dynamics of fiber motion in low viscosity fluids, such as air, a different experimental method is necessary; however, dependencies of the magnetic torque found in the present study still hold true. / Graduation date: 1993