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Part I discusses the development of an aluminum-magnesium-silicon alloy that may combine strength, extrudability, favorable corrosion resistance with low cost and scrap compatibility. The first part of the study determined the effects of small composition, heat treatment and mechanical processing changes on the ambient temperature tensile properties of the alloy. A combination of magnesium and silicon of about 2%, 1% copper, 0.2% chromium and 0.1% vanadium can produce a T6 alloy with significant higher strength, fatigue and corrosion fatigue properties for both ingot and extrusion than those of 6061 but with only a modest increase in cost. The new alloy has been designated as AA6069. The second part of the study determined the T6 properties of 6069 alloy. The tensile test results of cold and hot extrusions of hollow, solid bars, and high pressure cylinders indicate that the T6 properties ranged from 55-70 ksi (380-490 MPa) UTS, 50-65 ksi (345-450 MPa) yield strength, and 10-18% elongation. It also appears that the fracture toughness and general corrosion resistance in saline environment are comparable or better than those of 6061 T6. Part II attempted to evaluate the formation, formability, thermal and mechanical properties of semi-solid A356, A357 and modified aluminum silicon semi-solid alloys. The semi-solid alloy microstructure was produced in this study by purely thermal treatment rather than conventional and expensive electromagnetic or mechanical stirring. Three heat-up stages in semi-solid treatment were evaluated. Stage I is related to the heating of the alloy in the solid state. Stage II is related to the eutectic reaction. Stage III is related to the heating of the semi-solid slurry. Stage II requires the longest time of the three heat-up stages due to the endothermic reaction on heating. An increase of furnace temperature can greatly reduce the time of stage II. The atmosphere (vacuum, air, argon) of the semi-solid treatment does not appear to greatly affect the T6 properties of semi-solid alloys. The microstructure and T6 properties of semi-solid A356 do not appear sensitive to the homogenization treatments before semi-solid treatment. The porosity of semi-solid ingots and pressed parts increases as the cooling rate decreases in unformed and subsequent-to-moderate pressure forming. The T6 properties basically appear sensitive to voids, with a degradation of properties as the void concentration increases. The formability of A357 may be improved as the spheroidal particle size decreases. Hence, formability may improve with decreasing ingot grain size. The mechanism of coarsening of the solid phase at isothermal temperatures is related to Ostwald ripening and/or "merging" of particles. The mechanical properties of die-casting parts show that the method of thermal treatment to produce a spheroidal microstructure is an effective method for industrial production of semi-solid aluminum-silicon alloys. / Graduation date: 1997

Thesis (M. Eng. Sc.)--University of Adelaide, Dept. of Chemical Engineering,1991. / Includes bibliographical references (leaf 95).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 141-143).

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Cressler, John; Committee Member: Papapolymerou, John; Committee Member: Shen, Shyh-Chiang; Committee Member: Steffes, Paul; Committee Member: Zhou, Hao Min. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 57-58.

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 56-57.

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

In boron doped silicon, optical excitation of bound holes from the ground state to the various excited states of the neutral acceptor impurity leads to an absorption line spectrum. By applying an external strain, the degeneracies of the acceptor ground state and the four lowest "observable" excited states were determined and were found to only partially agree with theory (Schechter 1962). By applying a uniform electric field to compensated samples, the "Stark effect" for the acceptor states was observed. The Stark shift of the excited states is second order in the field as predicted by Kohn (1957) from symmetry considerations. The Stark broadening of the acceptor absorption lines was attributed to an unresolved partial removal of degeneracy of the excited states. The absorption line broadening mechanisms (phonon, dislocation, concentration, ionized impurity) were determined from new halfwidth measurements, which corrected an earlier study (Colbow 1963). The ionized impurity broadening is caused by the screened Coulomb "internal fields" of nearby ionized impurities which are present in uncompensated samples at temperatures greater than 50°K. A new theory of this broadening contribution (Cheng 1966) is in reasonable agreement with experiment; the earlier theory of the same effect (Colbow 1963) is shown to be inadequate. The effects of compensation on the boron absorption spectrum were measured and attributed to the unscreened Coulomb fields of ionized impurities present because of the compensation. The properties of a weak new absorption line which appeared in the compensated spectrum are described. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

by Cheung Wing-yiu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [170-185]). / ACKNOWLEDGMENT --- p.I / abstract --- p.II / contents --- p.IV / figure captions --- p.C-1 / table captions --- p.C-10 / photo captions --- p.C-11 / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Novel Silicon-Based Materials Structures - Background and Perspectives --- p.2 / Chapter 1.2 --- Light Emission from Porous Silicon --- p.3 / Chapter 1.2.1 --- Quantum size effect --- p.7 / Chapter 1.2.2 --- Chemical luminescence model --- p.9 / Chapter 1.3 --- Germanium Silicon Alloy --- p.11 / Chapter 1.3.1 --- Formation of germanium silicon alloy by ion implantation --- p.16 / Chapter 1.4 --- Scope of this Work --- p.19 / Chapter CHAPTER 2 --- EXPERIMENTAL METHODS --- p.20 / Chapter 2.1 --- Preparation of Porous Silicon Layers --- p.20 / Chapter 2.1.1 --- Anodization --- p.21 / Chapter 2.1.2 --- Post - anodization treatments --- p.25 / Chapter 2.2 --- Preparation of Germanium Silicon Alloy --- p.27 / Chapter 2.2.1 --- Ion implantation --- p.27 / Chapter 2.2.2 --- Thermal treatment --- p.27 / Chapter 2.3 --- Characterization Methods --- p.28 / Chapter 2.3.1 --- Microscopy studies --- p.28 / Chapter 2.3.2 --- Structural studies --- p.30 / Chapter 2.3.3 --- Compositional studies --- p.31 / Chapter 2.3.4 --- Electron spin resonance --- p.32 / Chapter 2.3.5 --- Optical methods --- p.36 / Chapter 2.3.6 --- Electrical measurements --- p.38 / Chapter 2.3.6.1 --- Spreading resistance profiling --- p.38 / Chapter 2.3.6.2 --- Other electrical measurements --- p.40 / Chapter CHAPTER 3 --- POROUS SILICON - RESULTS --- p.41 / Chapter 3.1 --- General observation of on the Appearance of Samples --- p.41 / Chapter 3.2 --- Formation Current Voltage Characteristics --- p.41 / Chapter 3.3 --- Surface Morphology --- p.52 / Chapter 3.4 --- Electron Spin Resonance --- p.56 / Chapter 3.5 --- Composition Characteristics --- p.68 / Chapter 3.6 --- Optical Characteristics --- p.72 / Chapter 3.6.1 --- Infra-red transmittance studies --- p.72 / Chapter 3.6.2 --- Photoluminescence --- p.74 / Chapter 3.7 --- Electrical Properties --- p.82 / Chapter CHAPTER 4 --- POROUS SILICON - DISCUSSION --- p.84 / Chapter 4.1 --- Formation Properties --- p.84 / Chapter 4.2 --- Structural Properties --- p.87 / Chapter 4.3 --- Paramagnetic Centres in Porous Silicon --- p.88 / Chapter 4.4 --- Compositional Properties --- p.93 / Chapter 4.5 --- Photoluminescence --- p.95 / Chapter 4.6 --- Electrical Properties --- p.105 / Chapter 4.7 --- Summary --- p.106 / Chapter CHAPTER 5 --- GERMANIUM SILICON ALLOY - RESULTS --- p.108 / Chapter 5.1 --- Structural Characteristics --- p.108 / Chapter 5.1.1 --- Defect structure --- p.109 / Chapter 5.1.2 --- Crystal structure --- p.115 / Chapter 5.2 --- Optical Characteristics --- p.127 / Chapter 5.3 --- Electrical characteristics --- p.129 / Chapter 5.3.1 --- Spreading resistance profiling --- p.129 / Chapter 5.3.2 --- Other electrical measurements --- p.138 / Chapter CHAPTER 6 --- GERMANIUM SILICON ALLOY - DISCUSSION --- p.142 / Chapter 6.1 --- Structure Analysis --- p.142 / Chapter 6.2 --- Optical Properties --- p.146 / Chapter 6.3 --- Electrical Properties --- p.147 / Chapter 6.4 --- Summary --- p.150 / Chapter CHAPTER 7 --- CONCLUSIONS --- p.152 / Chapter 7.1 --- Porous Silicon --- p.152 / Chapter 7.2 --- Germanium Silicon Alloys --- p.154 / Chapter CHAPTER 8 --- FURTHER WORK --- p.156 / Chapter 8.1 --- Porous Silicon --- p.156 / Chapter 8.2 --- Germanium Silicon Alloys --- p.156 / APPENDIX / Chapter I --- SPECTRA OF GERMANIUM SILICON ALLOY --- p.A1 / Chapter 1.1 --- Rutherford Backscattering Spectra --- p.A2 / Chapter 1.2 --- Spreading Resistance Depth Profile --- p.A8 / Chapter II --- PUBLICATIONS --- p.A14 / BIBLIOGRAPHY --- p.A15