by Hon Wan Man = 鎂和硼化鎂複合材料的研究 / 韓韻文. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Hon Wan Man = Mei he peng hua mei fu he cai liao de yan jiu / Han Yunwen. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / Table of contents --- p.vi / List of tables --- p.x / List of figures --- p.xi / Chapter Chapter 1 --- Introduction --- p.1-1 / Chapter 1.1. --- Background --- p.1-1 / Chapter 1.1.1. --- Conventional and unconventional superconducting materials --- p.1-1 / Chapter 1.1.2. --- Type I and type II superconductors --- p.1-2 / Chapter 1.1.3. --- Critical Temperature and Magnetic Properties (M-H Loops) --- p.1-4 / Chapter 1.2. --- Magnesium Diboride MgB2 --- p.1-6 / Chapter 1.2.1. --- Introduction --- p.1-6 / Chapter 1.2.2. --- Potential application and recent work of MgB2 --- p.1-6 / Chapter 1.2.2.1. --- Thin films --- p.1-7 / Chapter 1.2.2.2. --- Wires and tapes --- p.1-8 / Chapter 1.2.2.3. --- Powders and single crystal --- p.1-8 / Chapter 1.2.3. --- Factors affecting critical temperature in MgB2 --- p.1-9 / Chapter 1.2.3.1. --- Critical temperature versus lattice constants --- p.1-9 / Chapter 1.2.3.2. --- Critical temperature versus pressure --- p.1-9 / Chapter 1.3. --- Mg-based metal matrix composites (Mg-MMCs) --- p.1-10 / Chapter 1.4. --- Objectives and approaches --- p.1-11 / Chapter 1.5. --- Thesis layout --- p.1-12 / Chapter 1.6. --- References --- p.1-13 / Figures --- p.1-16 / Tables --- p.1-20 / Chapter Chapter 2 --- Methodology and instrumentation --- p.2-1 / Chapter 2.1. --- Introduction --- p.2-1 / Chapter 2.2. --- Experimental procedures --- p.2-1 / Chapter 2.3. --- Samples fabrication --- p.2-2 / Chapter 2.3.1. --- Powder metallurgy method (P/M) --- p.2-2 / Chapter 2.3.2. --- Argon atmosphere tube furnace heat treatment --- p.2-3 / Chapter 2.4. --- Characterization --- p.2-3 / Chapter 2.4.1. --- Differential thermal analyzer (DTA) --- p.2-3 / Chapter 2.4.2. --- X-ray powder diffractometry (XRD) --- p.2-4 / Chapter 2.4.3. --- Hot mounting and polishing --- p.2-4 / Chapter 2.4.4. --- Scanning electron microscopy (SEM) --- p.2-5 / Chapter 2.4.5. --- Transmission electron microscopy (TEM) --- p.2-5 / Chapter 2.4.6. --- Vibrating sample magnetometer (VSM) --- p.2-6 / Chapter 2.5. --- References --- p.2-8 / Figures --- p.2-9 / Chapter Chapter 3 --- Effects of sintering temperature on Mg-MgB2 composites --- p.3-1 / Chapter 3.1. --- Introduction --- p.3-1 / Chapter 3.2. --- Experimental results --- p.3-1 / Chapter 3.2.1. --- DTA and XRD analyses --- p.3-1 / Chapter 3.2.2. --- Microstructures --- p.3-2 / Chapter 3.2.2.1. --- Green sample --- p.3-2 / Chapter 3.2.2.2. --- Sample sintered at 550°C --- p.3-3 / Chapter 3.2.2.3. --- Sample sintered at 600°C --- p.3-4 / Chapter 3.2.2.4. --- Sample sintered at 700°C --- p.3-4 / Chapter 3.2.2.5. --- Hexagonal platelets --- p.3-5 / Chapter 3.2.3. --- Superconducting behaviors --- p.3-5 / Chapter 3.2.3.1. --- Critical temperature (Tc) comparison --- p.3-5 / Chapter 3.2.3.2. --- Magnetization loops (M-H loops) --- p.3-6 / Chapter 3.3. --- Discussions --- p.3-7 / Chapter 3.4. --- Conclusions --- p.3-9 / Chapter 3.5. --- References --- p.3-10 / Figures --- p.3-11 / Tables --- p.3-20 / Chapter Chapter 4 --- Effects of composition on Mg-MgB2 composites --- p.4-1 / Chapter 4.1. --- Introduction --- p.4-1 / Chapter 4.2. --- Experimental results --- p.4-1 / Chapter 4.2.1. --- XRD results --- p.4-1 / Chapter 4.2.2. --- Microstructures --- p.4-2 / Chapter 4.2.2.1 --- Mg-0 wt % B (Pure Mg) sintered at 650。C --- p.4-2 / Chapter 4.2.2.2 --- Mg-47 wt % B sintered at 650°C --- p.4-2 / Chapter 4.2.2.3 --- Amount of B in Mg sample --- p.4-3 / Chapter 4.2.2.3.1. --- Overview of Mg-5 to 40 wt % B --- p.4-3 / Chapter 4.2.2.3.2. --- MgB2 phase in different composition (Mg-5 to 47 wt %B) --- p.4-4 / Chapter 4.2.2.3.3. --- MgO phase in different composition (Mg-0 to 30 wt % B) --- p.4-4 / Chapter 4.2.3. --- VSM results (Critical temperature Tc comparison) --- p.4-5 / Chapter 4.3. --- Discussions --- p.4-6 / Chapter 4.4. --- Conclusions --- p.4-8 / Chapter 4.5. --- References --- p.4-10 / Figures --- p.4-11 / Table --- p.4-18 / Chapter Chapter 5 --- Growth Mechanisms --- p.5-1 / Chapter 5.1. --- Introduction --- p.5-1 / Chapter 5.2. --- Brief summary of SEM result --- p.5-1 / Chapter 5.3. --- Growth Mechanism of MgB2 --- p.5-2 / Chapter 5.4. --- Comparison of MgB2 grain size by XRD result --- p.5-7 / Chapter 5.5. --- Stoichiometric Ratio of MgB2 in different temperature --- p.5-7 / Chapter 5.6. --- Growth of the MgB2 platelets --- p.5-8 / Chapter 5.7. --- Conclusions --- p.5-10 / Chapter 5.8. --- References --- p.5-11 / Figures --- p.5-12 / Table --- p.5-15 / Chapter Chapter 6 --- Conclusions and Future Works --- p.6-1 / Chapter 6.1. --- Conclusions --- p.6-1 / Chapter 6.2. --- Future works --- p.6-2 / Chapter 6.3. --- References --- p.6-4

New types of quantum interference oscillations in transverse magnetoresistance of single crystals of ultrapure magnesium are reported. These oscillations occur as a function of the angle of rotation when the current is passed along the [112̄0] direction and the magnetic field H(→) is rotated by ≲ 1° from [101̄0] towards the [0001] symmetry axis. In order to characterize the oscillations, extensive qualitative data were taken for fields up to 24 kG and for temperatures in the range of 1.4 K-4.2 K. It is shown that these angle-dependent oscillations have the same origin as the field-dependent interferometer oscillations first reported by Stark and Friedberg. Both types of oscillations arise from the electron quantum states on the coupled orbit network, which is obtained for H(→)∥[1010]. It is shown that high sensitivity of the oscillations and the background magnetoresistance (for H within →1° from [101̄0] to field inhomogeneity and crystal strain yields strong evidence for a new regime of quantum transport. In this regime, quantum phase coherence of the electrons extends over distances of the order of 0.1 mm, and coherence determines not only the oscillation amplitudes but also the background. The "stacked mirror" model of Stark and Reifenberger is not applicable in such a regime of transport. A rudimentary model is presented that seems to be in qualitative agreement with the data. However, band structure calculations firmly establish that the large oscillations arise from the symmetry breaking of the two interferometer lobes as the field is rotated away from [101̄0].

No description available.

Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed May 19, 2009) Graduate School of Engineering, Dept. of Chemical Engineering. Includes bibliographical references p. 271-281).

Thesis (Ph. D.)--University of Michigan, 1928.

Thesis (Ph. D.)--University of Michigan, 1926.

Thesis (Ph. D.)--University of Michigan, 1926.

Magnesium hydroxide, a stable flame retardant, can be obtained by mining or by the hydration of magnesium oxide. In this study, the effect of different hydrating agents on the pH of the hydrating solution, rate of hydration of MgO to Mg(OH)2 and product surface area were studied as a function of the temperature of hydration. Ammonium chloride, magnesium acetate, magnesium nitrate, nitric acid, acetic acid, water, magnesium chloride, sodium acetate and hydrochloric acid were used as hydrating agents. The hydration experiments were carried out in a water bath between 30 - 80 oC for 30 minutes. Dried MgO samples were introduced to the hydrating solution and the slurry was stirred at a constant speed. At the end of each experiment, the slurry was vacuum filtered, washed with water, dried at 200 oC and hand ground. The products were then characterized by TGA, XRF, XRD and BET surface area analyses. There was not a significant difference in the hydration behaviour of the hydrating agents up to 50 oC, where less than 10 % of magnesium hydroxide was formed. When compared to the hydration in water, all the hydrating agents with the exception of sodium acetate showed a significant increase in the degree of hydration. Sodium acetate formed the lowest amount of magnesium hydroxide, ranging between 1.2 and 12.2 % magnesium hydroxide. Hydrations performed in hydrochloric acid and magnesium nitrate formed the largest percentage (11.8 %) of magnesium hydroxide at 60 oC. Magnesium acetate, magnesium nitrate, magnesium chloride and hydrochloric acid seemed to be the most effective hydrating agents at 70 oC with the percentage magnesium hydroxide being formed ranging between 20.0 and 23.9 %. The amount of hydroxide formed doubled at 80 oC, with the largest percentage (56.7 %) formed from the hydration in magnesium acetate. The hydration reaction seemed to be dependent upon the presence of Mg2+ and acetate ions. It seemed that magnesium oxide hydration is a dissolution-precipitation process controlled by the dissolution of magnesium oxide. The results have also indicated that the pH and temperature of the hydrating solution strongly influence the degree of hydration. / Chemistry / M.Sc. (Chemistry)

Hydromagnesite, the most stable of the basic magnesium carbonates, can be obtained by mining or by synthesis. Existing synthetic procedures have certain drawbacks which include, undesirable environmental effluents or high pressure and/or temperature requirements. Due to the lack of information in the literature, the aim of this study was to develop a cost effective procedure for the synthesis of basic magnesium carbonate from Mg(OH)2, not hampered by the above mentioned drawbacks. Following an extensive investigation into various parameters that influenced the final product, a simple procedure, based on sparging CO2 through a slurry of magnesium hydroxide in water until the pH reached 7.5-8.5, was developed. The solid portion of the slurry is dried at 80 or 120°C to deliver an unidentified basic magnesium carbonate and hydromagnesite respectively. The products were characterised by XRD, TG-DTA, surface area determination, SEM and FT-IR. The rehydration characteristics of the products were also investigated. By combining the information obtained by each technique, valuable information could be obtained. The synthesised products were evaluated for flame retardant application, due to the demand of mineral flame retardants which could compete with Mg(OH)2 and AI(OH)3. Compared to the traditionally used halogenated flame retardants, the mineral flame retardants deliver non-toxic, non-corrosive decomposition products and contributes in suppressing the emission of smoke in a fire. Results indicated that the basic magnesium carbonates compared favourably to Mg(OH)2 and AI(OH)3 and presented several advantages in terms of flame retardant applications. Further tests will be necessary to accurately assess the flame retardant effect of the basic magnesium carbonates. The possibilities however seem promising. / Thesis (PhD (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted

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