The purpose of this thesis has been the determination of the nature and cause of time-softening property of the lead-tin alloys in the solid solution range. An alloy of 19% tin, 81% lead was chosen as exhibiting the property to a degree suitable for observation of the accompanying phenomena. The investigation proceeded in three parts: (1) an observation of the time-softening property itself by means of series of hardness tests to determine the degree of change and the time required for its accomplishment; (2) a search for x-ray evidence of possible precipitation which might be apparent as a change in the lattice constant of the crystal; and (3) conductivity measurements as a further check on whether the solution concentration was changing. The results accordingly may be classified under the same three headings. The change in hardness of the lead-tin alloy under investigation is intimately related to its habit of precipitating some of the excess tin from the solid solution. Both the x-ray and the conductivity test results offer supporting evidence that precipitation does occur in conjunction with the softening effect. Apparently also the softening effect observed in the lead-tin alloy is a definite phenomenon distinct from the “over-aging” effect in which an alloy aged at high temperature increases rapidly in hardness until a certain critical hardness is reached, after which softening sets in. / M.S.

X-ray polycrystalline diffraction techniques are used to determined the defect structure in a commercial Cu-l1.55 at. %Be-O.23 at. %Co alloy during low temperature aging. The analysis of the X-ray diffraction patterns is aided by the computer modeling of the defects inside the crystals using an elastic model. The research is to provide more detailed understanding of the precipitate structures in the process of aging and the age hardening mechanism of the alloy. The diffraction profiles from samples aged for different times at 315°C are collected using a position sensitive proportional counter with eu 1(0:1 radiation. The hardness values of the samples are also measured. An elastic model for the coherent precipitates in anisotrpic matrix is developed according to Eshelby's treatment of transformed regions in an elastic continuum. The displacement fields generated by the precipitates in the surrounding matrix, obtained through the elastic model, are used to explain the (110) streaks near the Bragg reflection, and to calculate the powder diffraction patterns from the aged alloys. For the latter purpose, a general X-ray diffraction theory is developed, combining the work of Krivoglaz and Dederichs. The X-ray diffraction patterns are compared with existing TEM observations in the literature. The analysis of the diffraction patterns suggests that the precipitates in the early stage of aging (GP zones) can be the matrix constrained version of 7, the equilibrium phase, similar to an observation by Khatchaturyan and Laughlin on 7 and 7'. The quantitative calculation based on this model shows excellent agreement with experimental data for samples aged at 315°C. The averaged inter-precipitate spacing in the crystals for the optimally aged sample at 315°C is determined to be 200-300A. A simplified method of evaluating the thermal diffuse scattering and a method for calculating the diffuse scattering from polycrystalline materials with textures are also presented. / Ph. D.

Displacement fields from point-like defects are investigated by x-ray diffraction. The atomic volume changes in the interstitial compounds using crystallographic information has been found to correlate with the size of filled octahedral sites. Systematic correlations enable estimates to be made of the components of the dipole tensor for interstitials in octahedral sites for binary systems containing N, C, and 0 in V, Nb, Ta, Cr, Mo, W, and Fe lattices. X-ray diffraction analysis of the concentration and residual stress gradients in N implanted Mo crystals and Nb films show that the dominant source of internal strain arises from N located in octahedral sites. For Nb implanted at LNT, these distortion centers are aligned equally along three mutually perpendicular directions to maintain cubic symmetry. Large biaxial residual strains are developed after a 5at% implantation of N into Nb and Mo. Radiation damage is present as small vacancy and interstitial loops. A method was developed to obtain the orientation function for samples containing a fiber texture. A slit correction is included and the final results from this simplified approach are compared with the pole figure measured by direct x-scanning. Knowing the orientation function allows one to correct the integrated intensities to that for an ideal powder, thereby allowing thermal and static displacements to be obtained from textured samples. Anisotropic displacements about coherent Be rich GP zones were investigated in a Cull-at%Be alloy. The results indicate that the attenuation factor 2M which determines the relative integrated intensities of Bragg, quasiline, and static diffuse scattering can be expressed in a simplified form. Experimental data of 2M for aged Cu-Be samples show an anisotropy. The anisotropy increases with increasing aging time when the equiaxed-GP zones formed in the early stage collapse into platelike GP zones. / Ph. D.

M.S.

X-ray techniques were used extensively in this work to examine ceramic samples. The well known techniques including : (1) identification of phases and chemical species, (2) peak separation, (3) quantitative phase analysis, (4) intensity band simulation, and (5) line shape analysis, were applied to ceramic materials of silicon nitride, zirconia toughened alumina, fully and partially stabilized zirconia. A theoretical derivation of the x-ray intensity from a rough sample based on a statistical roughness model was carried out. The statistical model was then combined with the intensity band simulation technique to simulate the intensity band from a rough sample. The modified technique for intensity band simulation was used to determine the strain profile in the near surface regions of a flat and a rough fully stabilized zirconia samples. The results show that a compressive zone is present in the near surface region of each sample. A partially stabilized zirconia disk was examined using symmetrical and asymmetrical diffraction optics after a prolonged pin on disk wear test. The different diffraction optics provided different probe depths and revealed a depth gradient of the phase distribution. A general picture of the wearing process of ceramic components is described based on the examinations carried out in this work. / Ph. D.

An X-ray diffraction method has been developed which was able to describe the diffusion zone produced by annealing nickel plated copper specimens at 750 degrees and 850 degrees. The experimental X-ray diffraction data were first corrected for instrumental broadening and then used to compute concentration-penetration curves across the diffusion zone. the experimental curves are in general agreement with a new mathematical analysis and also the diffusion coefficients reported in the literature. / Master of Science

No description available.

Structures were determined for 48 new natural products and several related compounds by NMR methods. One new natural product and two unnatural product structures were determined by X-ray diffraction. Molecular mechanics calculations on two indoles related to the neurotransmitter serotonin and on some synthetic cyclophanes were used to gain information about their preferred conformations. Considerable time is wasted redetermining the structures of known natural products when they are encountered in new sources. To help alleviate this problem, a database which searches on proton NMR chemical shifts was developed.

Kwan Wing Tak. / On t.p., "3" is subscript following the word: Pb (Zr, Ti) O" in the title. / Title also in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves [96-100]). / Acknowledgement / Abstract / Chapter Chapter 1 --- Introduction --- p.1-1 / Chapter Chapter 2 --- Experimental Set-Up and Procedure / Chapter Section 2.1 --- General Description of Experiments --- p.2-1 / Chapter Section 2.2 --- High Temperature X-ray Diffraction Technique --- p.2-1 / Chapter Section 2.3 --- Sawyer-Tower Bridge --- p.2-3 / Chapter Section 2.4 --- Thermomechnical Analysis System(TMS) & Differential Scanning Calorimeter(DSC) --- p.2-4 / Chapter Section 2.5 --- Laser Experiment --- p.2-4 / Chapter Chapter 3 --- X-ray Experimental Results / Chapter Section 3.1 --- Investigation of PZT film on (100) MgO Single Crystal Substrate --- p.3-1 / Chapter Section 3.2 --- Investigaiton of PZT Bulk Materials by X-ray Diffractometer and Vacuum Chamber --- p.3-3 / Chapter Chapter 4 --- Experimental Data from TMS / Chapter Section 4.1 --- Experimental Details --- p.4-1 / Chapter Section 4. 2 --- Results --- p.4-2 / Chapter Chapter 5 --- "Measurement of Curie temperature using Ferroelectric Properties, Heat Capacity and Piezoelectric Properties of PZT" / Chapter Section 5.1 --- Investigation of the Ferroelectric Properties of PZT Bulk Material by Sawyer´ؤTower Bridge --- p.5-1 / Chapter Section 5.2 --- Investigation of the Heat Capacity of PZT Bulk Material by Differential Scanning Calorimeter (DSC) --- p.5-2 / Chapter Section 5.3 --- Investigation of Piezoelectric Properties of PZT Bulk Material by Laser Method --- p.5-3 / Chapter Section 5.4 --- Discussion of Results --- p.5-4 / Chapter Section 5.5 --- Data Summary --- p.5-5 / Chapter Chapter 6 --- Data Analysis and Discussion / Chapter Section 6.1 --- Analysis of Structural X-ray Data --- p.6-1 / Chapter Section 6.2 --- Analysis of TMS Data --- p.6-2 / Chapter Section 6.3 --- Discussion --- p.6-4 / Chapter Chapter 7 --- Conclusion --- p.7-1 / Reference

by Lee, Chun-Sing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 98-105). / Abstracts in English and Chinese. / Acknowledgements --- p.2 / Abstract --- p.3 / Table of Contents --- p.7 / List of Figures --- p.10 / List of Tables --- p.13 / Chapter Chapter 1 --- Introduction --- p.14 / Chapter 1.1. --- Ion implantation --- p.14 / Chapter 1.2. --- Scope of the thesis --- p.15 / Chapter Chapter 2 --- Background Theory --- p.17 / Chapter 2.1. --- Ion stopping --- p.17 / Chapter 2.2. --- The energy-loss process --- p.17 / Chapter 2.3. --- Kinematics of binary elastic collision --- p.20 / Chapter 2.4. --- Nuclear and electronic stopping --- p.21 / Chapter 2.5. --- Radiation Damage --- p.22 / Chapter 2.6. --- Spikes --- p.24 / Chapter 2.7. --- Topography of ion bombarded surface --- p.26 / Chapter Chapter 3 --- Equipment Reviews --- p.31 / Chapter 3.1. --- Metal Vapour Vacuum Arc Ion Source Implanter --- p.31 / Chapter 3.2. --- Atomic Force Microscopy --- p.34 / Chapter 3.3. --- Rutherford Backscattering Spectrometry --- p.37 / Chapter 3.4. --- X-ray Diffraction --- p.40 / Chapter Chapter 4 --- Study of Ion Beam Implanted Germanium by Atomic Force Microscopy and Rutherford Backscattering Spectrometry --- p.43 / Chapter 4.1. --- Introduction --- p.43 / Chapter 4.2. --- Experiments --- p.45 / Chapter 4.3. --- Results and discussion --- p.47 / Chapter 4.3.1. --- AFM --- p.47 / Chapter 4.3.2. --- RBS and ion channeling --- p.64 / Chapter 4.4. --- Conclusions --- p.71 / Chapter Chapter 5 --- Ion Beam Synthesised Cobalt Germanide Alloy by Metal Vapour Vacuum Arc Implantation --- p.73 / Chapter 5.1. --- Introduction --- p.73 / Chapter 5.2. --- Experiments --- p.74 / Chapter 5.3. --- Results and discussion --- p.74 / Chapter 5.3.1. --- XRD --- p.74 / Chapter 5.3.2. --- AFM --- p.78 / Chapter 5.3.3. --- RBS and ion channeling --- p.82 / Chapter 5.4. --- Conclusions --- p.87 / Chapter Chapter 6 --- Tip Artifacts in Atomic Force Microscope Imaging of Ion Bombarded Nanostructures on Germanium Surfaces --- p.89 / Chapter 6.1. --- Introduction --- p.89 / Chapter 6.2. --- Experiments --- p.90 / Chapter 6.3. --- Results and discussion --- p.90 / Chapter 6.4. --- Conclusions --- p.95 / Chapter Chapter 7 --- Conclusions --- p.96 / Bibliography --- p.98 / Publications --- p.105