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An Ising-like model to predict dielectric properties of the relaxor ferroelectric solid solution BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃ / An Ising-like model to predict dielectric properties of the relaxor ferroelectric solid solution BaTiO3 - Bi(Zn1/2Ti1/2)O3Jackson, Dennis L. 01 December 2011 (has links)
We developed a model to investigate the dielectric properties of the
BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) solid solution, which is a relaxor ferroelectric and exhibits long range disorder. The model uses ab initio methods
to determine all polarization states for every atomic configuration of 2 x 2 x 2
supercells of BT-BZT. Each supercell is placed on a lattice with an Ising-like
interaction between neighboring cell polarizations. This method allows us to
consider long range disorder, which is not possible with ab initio methods
alone, and is required to properly understand relaxor ferroelectric materials.
We analyze the Monte Carlo data for a single lattice configuration using the
multiple histogram method, and develop a modified histogram technique to
combine data from multiple lattice configurations. Our calculated values of
dielectric constant, specific heat, and polarization agree reasonably well with
experiment. / Graduation date: 2012
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Preparation and Characterization of Electrolyte Materials for Proton Conducting Fuel CellsGibson, Stephen B Unknown Date
No description available.
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The Terrestrial Biogeochemical Cycle of barium: A proposed study to examine barium flux in Mojave Desert dustKaur, Mehar 01 January 2013 (has links)
Barium is a relatively abundant element in the crustal environments, Ba quantities can range from anywhere between 200ppm to 900ppm. Most common forms of Ba-minerals found in the environment are barite (BaSO4), witherite (BaCO3) and hollandite (Ba2Mn8O16). Ba is a useful element; it is used in various industries as a component in drilling fluids, in medical research and in manufacturing of various substances such as glass, ceramics, printing paper etc. However high quantity of Ba can be potentially toxic for the human body and can impair plant growth. It is therefore, important to review the terrestrial biogeochemical cycle of Ba, which is less studied and less understood than the oceanic biogeochemical cycle of Ba. Additionally, terrestrial systems face a diverse climate and are not as stable as the oceanic systems. Due to this the terrestrial biogeochemical cycle of barium is continuously changing and is more dynamic than the oceanic cycle. By studying one part of the cycle, i.e. the interaction of Ba in the atmosphere with the geosphere in the Mojave desert, NV, I propose a study to test the hypothesis that occurrence of, Ba-mineral, barite, in desert soils is mainly driven by dust flux. The proposal includes methodology for dust collection, sample analysis using XRF, XRD and SEM.EDS techniques and potential budget and timeline. Evidence supporting this claim would suggest that dust transports such minerals, affects the soil chemistry of desert soils and the interaction of various terrestrial systems.
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Sulphate removal from industrial effluents through barium sulphate precipitation / Swanepoel H.Swanepoel, Hulde. January 2011 (has links)
The pollution of South Africa’s water resources puts a strain on an already stressed natural
resource. One of the main pollution sources is industrial effluents such as acid mine drainage
(AMD) and other mining effluents. These effluents usually contain high levels of acidity,
heavy metals and sulphate. A popular method to treat these effluents before they are released
into the environment is lime neutralisation. Although this method is very effective to raise the
pH of the effluent as well as to precipitate the heavy metals, it can only partially remove the
sulphate. Further treatment is required to reduce the sulphate level further to render the water
suitable for discharge into the environment.
A number of sulphate removal methods are available and used in industry. These methods can
be divided into physical (membrane filtration, adsorption/ion exchange), chemical (chemical
precipitation) and biological sulphate reduction processes. A literature study was conducted in
order to compare these different methods.
The ABC (Alkali – Barium – Calcium) Desalination process uses barium carbonate to lower
the final sulphate concentration to an acceptable level. Not only can the sulphate removal be
controlled due to the low solubility of barium sulphate, but it can also produce potable water
and allows valuable by–products such as sulphur to be recovered from the sludge. The toxic
barium is recycled within the process and should therefore not cause additional problems. In
this study the sulphate removal process, using barium carbonate as reactant, was investigated.
Several parameters have been investigated and studied by other authors. These parameters
include different barium salts, different barium carbonate types, reaction kinetics,
co–precipitation of calcium carbonate, barium–to–sulphate molar ratios, the effect of
temperature and pH. The sulphate removal process was tested and verified on three different
industrial effluents.
The results and conclusions from these publications were used to guide the experimental
work. A number of parameters were examined under laboratory conditions in order to find the
optimum conditions for the precipitation reaction to take place. This included mixing
rotational speed, barium–to–sulphate molar ratio, initial sulphate concentration, the effect of temperature and the influence of different barium carbonate particle structures. It was found
that the reaction temperature and the particle structure of barium carbonate influenced the
process significantly. The mixing rotational speed, barium–to–sulphate dosing ratios and the
initial sulphate concentration influenced the removal process, but not to such a great extent as
the two previously mentioned parameters. The results of these experiments were then tested
and verified on AMD from a coal mine.
The results from the literature analysis were compared to the experiments conducted in the
laboratory. It was found that the results reported in the literature and the laboratory results
correlated well with each other.
Though, in order to optimise this sulphate removal process, one has to understand the
sulphate precipitation reaction. Therefore it is recommended that a detailed reaction kinetic
study should be conducted to establish the driving force of the kinetics of the precipitation
reactions. In order to upgrade this process to pilot–scale and then to a full–scale plant,
continuous reactor configurations should also be investigated.
The sulphate removal stage in the ABC Desalination Process is the final treatment step. The
effluent was measured against the SANS Class II potable water standard and was found that
the final water met all the criteria and could be safely discharged into the environment. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.
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Sulphate removal from industrial effluents through barium sulphate precipitation / Swanepoel H.Swanepoel, Hulde. January 2011 (has links)
The pollution of South Africa’s water resources puts a strain on an already stressed natural
resource. One of the main pollution sources is industrial effluents such as acid mine drainage
(AMD) and other mining effluents. These effluents usually contain high levels of acidity,
heavy metals and sulphate. A popular method to treat these effluents before they are released
into the environment is lime neutralisation. Although this method is very effective to raise the
pH of the effluent as well as to precipitate the heavy metals, it can only partially remove the
sulphate. Further treatment is required to reduce the sulphate level further to render the water
suitable for discharge into the environment.
A number of sulphate removal methods are available and used in industry. These methods can
be divided into physical (membrane filtration, adsorption/ion exchange), chemical (chemical
precipitation) and biological sulphate reduction processes. A literature study was conducted in
order to compare these different methods.
The ABC (Alkali – Barium – Calcium) Desalination process uses barium carbonate to lower
the final sulphate concentration to an acceptable level. Not only can the sulphate removal be
controlled due to the low solubility of barium sulphate, but it can also produce potable water
and allows valuable by–products such as sulphur to be recovered from the sludge. The toxic
barium is recycled within the process and should therefore not cause additional problems. In
this study the sulphate removal process, using barium carbonate as reactant, was investigated.
Several parameters have been investigated and studied by other authors. These parameters
include different barium salts, different barium carbonate types, reaction kinetics,
co–precipitation of calcium carbonate, barium–to–sulphate molar ratios, the effect of
temperature and pH. The sulphate removal process was tested and verified on three different
industrial effluents.
The results and conclusions from these publications were used to guide the experimental
work. A number of parameters were examined under laboratory conditions in order to find the
optimum conditions for the precipitation reaction to take place. This included mixing
rotational speed, barium–to–sulphate molar ratio, initial sulphate concentration, the effect of temperature and the influence of different barium carbonate particle structures. It was found
that the reaction temperature and the particle structure of barium carbonate influenced the
process significantly. The mixing rotational speed, barium–to–sulphate dosing ratios and the
initial sulphate concentration influenced the removal process, but not to such a great extent as
the two previously mentioned parameters. The results of these experiments were then tested
and verified on AMD from a coal mine.
The results from the literature analysis were compared to the experiments conducted in the
laboratory. It was found that the results reported in the literature and the laboratory results
correlated well with each other.
Though, in order to optimise this sulphate removal process, one has to understand the
sulphate precipitation reaction. Therefore it is recommended that a detailed reaction kinetic
study should be conducted to establish the driving force of the kinetics of the precipitation
reactions. In order to upgrade this process to pilot–scale and then to a full–scale plant,
continuous reactor configurations should also be investigated.
The sulphate removal stage in the ABC Desalination Process is the final treatment step. The
effluent was measured against the SANS Class II potable water standard and was found that
the final water met all the criteria and could be safely discharged into the environment. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.
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Barium ion cavity qed and triply ionized thorium ion trappingSteele, Adam V. 17 November 2008 (has links)
Trapped cold ions are tools which we used to approach two very disparate areas of physics, strong coupling between Ba+ ions and optical resonators, and investigations of a low-energy nuclear isomer of 229-Th. The first part of this thesis describes our progress towards the integration of a miniature Paul (rf) ion trap with a high finesse (F=30000) optical cavity. Ba+ ions were trapped and cooled for long periods and a new scheme for isotope selective photoionization was developed. The second part of this thesis describes our progress towards controlled excitation of the low energy nuclear isomer of 229-Th, which may provide a bridge between the techniques of cold atomic and nuclear physics. As a step towards this goal, 232-Th3+ ions were confined in rf ions traps and cooled via collisions with a buffer gas of helium. A sophisticated scanning program was developed for controlling ion trap loading, tuning lasers, and running a CCD camera to look for fluorescence. The low-lying electronic transitions of Th3+ at 984 nm, 690 nm and 1087 nm were observed via laser fluorescence.
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Investigation of some electron and nuclear interactions in solidsStott, J. P. January 1967 (has links)
No description available.
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Stoichiometry and Deposition Temperature Dependence of the Microstructural and Electrical Properties of Barium Strontium Titanate Thin FilmsPena, Piedad 05 1900 (has links)
Barium Strontium Titanate (BST) was deposited on Pt/ZrO2 / SiO2/Si substrates using liquid source metal organic chemical vapor deposition. A stoichiometry series was deposited with various GrII/Ti ratios (0.658 to 1.022) and a temperature series was deposited at 550 to 700°C. The thin films were characterized using transmission electron microscopy.
Both series of samples contained cubic perovskite BST and an amorphous phase. The grain size increased and the volume fraction of amorphous phase decreased with increasing deposition temperature. The electrical and microstructural properties improved as the GrII/Ti ratio approached 1 and deteriorated beyond 1. This research demonstrates that BST thin films are a strong candidate for future
MOS transistor gate insulator applications.
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EFFECTS OF PROCESSING ON PTCR BARIUM TITANATE SYSTEMS WITH BARIUM OXIDE AND TITANIUM OXIDE ADDITIONS IN THE NEAR STOICHIOMETRIC REGIONSUBRAMANIAM, SRINIVAS 17 April 2003 (has links)
No description available.
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Topological Phases, Boson mode, Immiscibility window and Structural Groupings in Ba-Borate and Ba-Borosilicate glassesHolbrook, Chad M. January 2015 (has links)
No description available.
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