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Kam Yuen Kwan = 利用散射及反衝粒子飛行時間譜儀及其他表面分析儀器就LiTaO3對質子及鋰離子交換後改變之研究 / 甘婉君. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Kam Yuen Kwan = Li yong san she ji fan chong li zi fei xing shi jian pu yi ji qi ta biao mian fen xi yi qi jiu LiTaO3 dui zhi zi ji li li zi jiao huan hou gai bian zhi yan jiu / Gan Wanjun. / Acknowledgements --- p.i / Abstract --- p.iii / Table of contents --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Definition of Ferroelectrics --- p.1 / Chapter 1.2 --- Common Properties of Ferroelectrics --- p.2 / Chapter 1.3 --- Polarization --- p.2 / Chapter 1.4 --- Lithium Tantalate (LiTa03) --- p.7 / Chapter 1.4.1 --- Crystal Structure --- p.8 / Chapter 1.4.2 --- Pyroelectric Effect --- p.9 / Chapter 1.4.3 --- Determination of Polarity --- p.10 / Chapter 1.4.4 --- Proton Exchange --- p.11 / Chapter 1.4.5 --- Reverse Exchange --- p.12 / Chapter 1.4.6 --- Applications --- p.13 / Chapter 1.5 --- Emerging Attentions in Surface Properties of Smart Materials --- p.14 / Chapter 1.6 --- Difficulties in Surface Studies of Ferroelectric and Related Smart Materials --- p.15 / Chapter 1.7 --- Recent Developments of TOF-SARS in Our Research Group and Its Applicability on LiTa〇3 --- p.16 / Chapter 1.8 --- Objectives of the Present Thesis Work --- p.17 / Chapter 1.9 --- Organization of the Thesis --- p.17 / Chapter 1.10 --- Reference --- p.18 / Chapter Chapter 2 --- Ion Exchange Processes and Sample Prepartion --- p.20 / Chapter 2.1 --- Fundamental of Ion Exchange Technique --- p.20 / Chapter 2.2 --- Sample Preparation --- p.22 / Chapter 2.2.1 --- Starting Material --- p.22 / Chapter 2.2.2 --- Proton Exchange Procedures --- p.23 / Chapter 2.2.3 --- Reverse Exchange Procedures --- p.23 / Chapter 2.3 --- Reference --- p.24 / Chapter Chapter 3 --- Time-of-Flight Ion Scattering and Recoiling Spectrometry (TOF-SARS) --- p.26 / Chapter 3.1 --- Introduction --- p.26 / Chapter 3.1.1 --- Physics in Elemental Analysis --- p.26 / Chapter 3.1.2 --- Physics in Structural Analysis --- p.29 / Chapter 3.2 --- Instrumentation --- p.32 / Chapter 3.2.1 --- Vacuum Chamber --- p.33 / Chapter 3.2.2 --- Pumping System --- p.35 / Chapter 3.2.3 --- Sample Manipulator --- p.35 / Chapter 3.2.4 --- Pulsed Ion Beam Line --- p.36 / Chapter 3.2.5 --- Detectors and Associated Electronics --- p.37 / Chapter 3.3 --- Reference --- p.39 / Chapter Chapter 4 --- Other Surface Science Tools Used in This Work --- p.41 / Chapter 4.1 --- Fourier Transform Infrared Spectroscopy (FTIR) --- p.41 / Chapter 4.1.1 --- Principle of FTIR --- p.41 / Chapter 4.1.2 --- Experiment --- p.42 / Chapter 4.1.3 --- Attenuated Total Reflectance (ATR) Mode of FTIR --- p.44 / Chapter 4.2 --- X-Ray Photoelectron Spectroscopy (XPS) --- p.45 / Chapter 4.2.1 --- Basic Principle of XPS --- p.45 / Chapter 4.2.2 --- Experimental Set Up --- p.48 / Chapter 4.3 --- Elastic Recoil Detection (ERD) --- p.49 / Chapter 4.3.1 --- Basic Theory of ERD --- p.49 / Chapter 4.3.2 --- Experimental Set Up --- p.50 / Chapter 4.4 --- Scanning Electron Microscope (SEM) --- p.51 / Chapter 4.4.1 --- Working Principle of SEM --- p.52 / Chapter 4.4.2 --- Experimental Set Up --- p.52 / Chapter 4.5 --- Reference --- p.53 / Chapter Chapter 5 --- Results and Discussions --- p.54 / Chapter 5.1 --- ERD Results on Incorporation of Protons --- p.54 / Chapter 5.2 --- XPS Results on Proton Exchange and Reverse Exchange --- p.56 / Chapter 5.3 --- FTIR Results on Proton Exchange and Reverse Exchange --- p.57 / Chapter 5.4 --- SEM Results on Domain-Inversion Induced by Proton Exchange --- p.59 / Chapter 5.5 --- TOF-SARS Results on Enhancement of Ion-induced Electron Emission by Proton Exchange --- p.61 / Chapter 5.5.1 --- Typical TOF-SARS Spectra - Data from Molybdenum Sample (Mo) Holder --- p.61 / Chapter 5.5.2 --- Virgin LiTa03 (0001) --- p.62 / Chapter 5.5.3 --- Possible Mechanism for the Variation of O(S) and the Electron Emission Yield --- p.65 / Chapter 5.5.4 --- The Use of O(S) Peak to Calculate the Potential Built Up upon a Change of Temperature --- p.67 / Chapter 5.5.5 --- TOF-SARS Data from the Proton and Lithium-ion Exchanged LiTa03 (0001) --- p.69 / Chapter 5.5.6 --- Plausible Mechanisms of Enhancement of Ion-induced Electron Yield induced by Proton Exchange --- p.70 / Chapter 5.6 --- Additional Discussions of the TOF-SARS Data on LiTa03 and Other Relevant Experiments --- p.75 / Chapter 5.6.1 --- Additional Discussion of the Nature of the Electron Peaks --- p.75 / Chapter 5.6.2 --- Additional Experiments on Azimuthal Angle (δ) Scans --- p.77 / Chapter 5.6.2.1 --- Data from Platinum (Pt) (111) as a Reference Test --- p.77 / Chapter 5.6.2.2 --- Azimuthal Angle Dependence of Ion-induced Electron Emission from Proton-ion Exchanged LiTa03 (0001) --- p.78 / Chapter 5.7 --- Reference --- p.80 / Chapter Chapter 6 --- Conclusion --- p.83 / Chapter Chapter 7 --- Appendix --- p.86 / Chapter 7.1 --- Caption --- p.86 / Chapter 7.2 --- Figures --- p.90

Abstract not available

Surface-analysis and treatment apparatus have been variously designed, manufactured, developed, and commissioned or re-commissioned, for characterising the surfaces and efficiency of positron moderators based around 3 µm thick polycrystalline-tungsten foil. These include XPS and AES, based around a CLAM2 hemispherical analyser, electron-beam heating, ion bombardment, mass spectroscopy, UHV sample mounting, UHV manipulation, gas-handling lines, and entry-lock apparatus. The CLAM2 electron spectrometer is additionally adapted for operation as a bipolar charged-particle spectrometer. All control software, and much data-analysis software, is implemented in Labview. Apparatus and techniques for safely storing, handling, transferring into vacuum, and manipulating in vacuo, a nominally 1 mCi 22Na, UHV-compatible positron source, are designed, constructed, and implemented. The efficacy of cleaning and surface-analysis apparatus are demonstrated, with some limitations and instrument malfunction identified, and solutions implemented. Methods for passivating positron-trapping states in polycrystalline tungsten are proposed, based on the current understanding of positron moderation and trapping. Improved moderator geometries have been designed and an alternative, simpler, and easier to implement solid-gas moderator proposed.

There is a large number of measurement techniques that is used for a surface inspection and a characterization of different types of materials. One of these techniques is a contact potential difference (CPD) scanning technique. In this project a non-vibrating contact potential difference (nvCPD) method is utilized to measure a work function and a topographical structure of a sample surface. A sample is mounted on a spindle that rotates at high speed. A nvCPD sensor detects work-function variations during movement above the sample surface. There are certain factors that create difficulties during the measurement process. A nonplanar sample surface, the spindle wobble and an incline of a mounted sample impede the safe (without impacting the surface) scanning at a close distance. The goal of this thesis was to implement a height sensor as a feedback device to dynamically control and adjust a CPD sensor flying height. Since a CPD signal is inversely proportional to the flying height, minimization of this height will enhance the signal magnitude, the signal-to-noise ratio and the resolution of measurements.

Open cell metal foams are a type of engineered material can be characterized by high porosity, high strength to weight ratio, tortuous flow paths and high surface area to volume ratio. It is the structure that gives the metal foams the characteristics that make them well suited for many application including heat exchangers. In this work, the structure of open celled metal foams is quantitatively characterized using an image analysis based method in order to predict the evaporative heat transfer of the metal foam using the fluid permeability. Several image processing algorithms were developed to quantitatively characterize the porosity, surface area per unit volume and the tortousity of metal foams from digital images of the cross sections of the material, and an expression was used to calculate the fluid permeability. An algorithm was developed to partion the pore space in the digital images so that individual cells within the structure could also be quantitatively characterized. Tools were also developed to predict the structure of open celled foam processed using the sacrificial template method by digitally constructing microstructures based the particle packing of the sacrificial templating material.

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The instability of flows around hump and dip imperfections is investigated. The mean flow is calculated using interacting boundary layers, thereby accounting for viscous/inviscid interaction and separation bubbles. Then, the two-dimensional linear instability of this flow is analyzed, and the amplification factors are computed. Results are obtained for several height/width ratios and locations. The theoretical results have been used to correlate the experimental results of Greening and Walker. The observed transition locations are found to correspond to amplification factors varying between 7.4 and 10, consistent with previous results for flat plates. The method accounts for Tollmien-Schlichting waves, the shear layer instability, and their interaction. Separation is found to increase significantly the amplification factor. / Master of Science

The surface chemistry of two systems of block copolymers was studied using angular dependent X-ray Photoelectron Spectroscopy poly(dimethyl (XPS). Surface concentration siloxane-b-sulfone)/polysulfone profiles of [PDMS/PSF] blends cast at several rates of solvent evaporation, and cast on several substrates were measured. Surface concentration profiles of poly(styrene-butadiene-styrene) poly(styrene-isoprene-styrene) [SIS] triblock [SBS] and copolymers cast at several rates of solvent evaporation, and cast from two different solvents were also measured. The concentration profile analyses were made using three different XPS quantification techniques. The PDMS/PSF systems were analyzed using the peak area ratio, and the SBS and SIS copolymers were analyzed using both the Cls shakeup to main ratio, and spectral measurements of the valence band. The results of this study indicate a variation in surface concentration as well as concentration gradient for different sample preparation routes. The variations can be explained by considering the rate of film formation (kinetics), polymer - solvent interactions, and polymer - substrate interactions. However, in both systems the lower surface energy copolymer block (siloxane block, or diene block) preferentially segregated to the surface for all of the sample preparation routes stUdied. / Master of Science