The crystallization/freezing and melting phenomena are critical in processing of chemicals and materials. Although melting is a very fundamental problem, the mechanism behind it has not been completely answered satisfactorily. Hence its study becomes very important. Perfect crystals do not exist; therefore it is very important to include the effect of defects in the above mentioned processes. The purpose of this work is to employ molecular simulation to further extend the understanding of theories of melting with respect to defects. We studied the melting and freezing process for a model system of copper with and without defects. We studied point defects (1, 2, 4, 8 vacancies and 1, 2, 4, 8 interstitials), line defects (edge dislocation) and surface defects (grain boundary) using molecular dynamics simulations. Constant stress-constant temperature ensemble with atmospheric pressures is employed. Various properties like average volume, density, potential energy and total energy are obtained as a function of temperature for each system. Most of the properties vary linearly before and after the phase transitions. During the transition process they show a dramatic change. This change is a sign of phase transition. The phase transition temperatures obtained from the single phase simulations are not the true melting (or freezing) points as there is some amount of superheating (or supercooling). Coexistence phase simulations are also done for the case of copper with no defects to find the true melting point. Most of the literature dealing with melting/crystallization on the basis of atomistic simulation does not include the influence of the presence of defects. Thus this work has a bearing on the various theories of melting.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xix, 130 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 98-101).

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Thesis (Ph. D. in Chemical Engineering)--University of California, Berkeley, Sept. 1960. / Also issues as UCRL-9213. Includes bibliographical references (leaves 233-239).

This work describes methods for making dynamic observations of the effects of electron beam heating, in a range of applications to semiconductors. The studies were based on the use of the time resolved reflectivity (TRR) method, in which the reflectivity of the specimens surface is measured during the heating cycle. The best experimental conditions for this technique have been identified and several applications are described in detail. Studies were made of epitaxial regrowth of amorphous layers created by ion implantation into silicon. The TRR method was applied using red and infra-red wavelengths, to characterize the regrowth kinetics, paying special attention to the influence of electrically active dopants. The results demonstrate that doping has a large effect on the regrowth process, for reasons which are related to both electrical and structural factors. The use of isothermal electron beam heating for annealing silicon-on-sapphire (SOS) specimens was investigated. In these studies, the TRR technique was applied to measurement of the temperature of the specimens and to observation of epitaxial recrystallization of amorphous layers created by self-implantation. In SOS films the amorphous layers could be at the surface or buried beneath a thin single crystal layer, and these cases resulted in different regrowth behaviour. TRR methods using green and red probe wavelengths proved to be sensitive to the type of crystallization, as well as the rate at which it occurs. They should also help to identify the best conditions for improvement of the crystal quality of SOS films. TRR was also used to examine heating of silicon-on-insulator materials by swept line electron beams. Temperature distributions were evaluated by measuring the reflectivity of a small area as the electron beam passed through it and the effects of various changes in the heating conditions were explored. Studies were made of zone melting recrystallization by observing the abrupt reflectivity changes which occur when silicon melts or freezes. In future work, TRR techniques could be developed to allow detailed investigation of the recrystallization process in structures intended for seeded recrystallization.

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The U.S. glass industry is a $28 billion enterprise and millions of tons of glasses are melted each day by different heating techniques, such as conventional oil fired furnaces or via electrical heating. The share of electrical heating is bound to rise steadily because it is cleaner and more energy efficient. Due to this situation molybdenum will play a significant role in electrical glass melting, since it is the most frequently used electrode material to deliver the electricity into the glass melts. Although it has a high melting point, high electrical and thermal conductivity and a low coefficient of expansion, molybdenum electrodes fail because of lack of sustainability during the glass melting process. Melt reaction with electrodes is the fundamental barrier to higher melting temperatures. Glass manufacturers have suggested that the need for better performance of molybdenum electrodes will see a rapid advancement in the use of electric heating system in the U.S. This work first focused on post-mortem analysis on used molybdenum electrodes with and without the current load in order to establish failure mechanisms for molybdenum during glass melting. It was determined that service life of molybdenum electrodes are limited by poor oxidation and corrosion resistance of molybdenum with redox reactions. Various studies have shown that the failure mode for molybdenum electrodes is a complex phenomenon. It depends on chemical composition of the electrode, current density and frequency, and chemical composition of the glass melt, specifically polyvalent ions that may be present in the melt. In this work, the MoSiB coating was validated as a promising protection for molybdenum from oxidation attack. Several molybdenum and molybdenum based-alloy electrodes were tested in different molten glasses in the remelter furnace to optimize the structural characteristics that are needed in Mo electrodes. Moreover, the quantitative data and fundamental knowledge gained in this work is being applied for molybdenum electrode production to extend its service life and also improve its quality.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

The main material of electric arc furnace steel makers is scrap steel. The scrap steel was melted and reduced into molten steel and the substance of lower melting and boiling points are concentrated in fly ash. The ash collected by dust collector contains also, other than organic pollutants like polycyclic aromatic hydrocarbons, (PAHs), inorganic heavy metal pollutants, such as zinc, cobalt and lead. It is found that the content of zinc and cobalt in the ash are exceeding statutory standard of 5 mg/L and 1 mg/L. They are hazardous industrial waste.In the Steel Basic Industry Collected Dust Storage Extending Review Operation Key Point as amended on July 1, 2010 by Environmental Protection Administration, all the steel mills shall complete treatment of the stored collected dust before June 30, 2014 and no further storage will be permitted. Due to the fact that domestic capacity of treating collected dust is insufficient to meet the statutory requirements, the final treatment and disposition of collect duct has become a serious question to the steel mills.In this research, we press the dust collected in the process of arc furnace steel making into ingot and place into arc furnace for further melting and refining. Under temperature of 1600 ¢Jpart of the heavy metal is gasified and returned to waste gas and become collected dust and part of Silicon Dioxide and Magnesium Oxide are sintered into slag and turn the hazardous industrial waste into recycled industrial waste for further utilization, so that they may be disposed. After melting treatment, the collected dust, the regenerated dust has the zinc compound content increased to 13.45% and therefore increases the recycling value of collected dust. In this process, Iron Oxide is reduced 9.41% which can be turned into steel billet (product) and Silicon Dioxide and Magnesium Oxide are reduced 2.67% and were turned into slag.Results of this research indicated that after melting treatment of collected dust, it will be reduced 0.26% and is therefore good for waste reduction.

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