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An examination of point defects and atomic diffusion in siliconMonson, Tyrus K. 25 July 1995 (has links)
The self-interstitial defect is commonly regarded as important in regulating diffusion
in silicon. A review of the literature reveals that the scientific bases for invoking the
self-interstitial defect are weak, while an alternate defect, the vacancy cluster, has been
largely ignored. One argument which has been used to establish dominance of the self-interstitial
defect over vacancies is based upon attempts to model gold diffusion.
Possible behavior of vacancies are considered, and the past analysis is found to be
inconclusive. Another argument which has been presented as evidence for presence of
silicon self-interstitials is based on observations of type "A" swirl defects. These defects
are amenable to interpretation in terms of solidification theory, without need to invoke
the interstitial point defect. Two experiments were designed to demonstrate influence
of heat treatments upon gold diffusion in electronic grade silicon crystal when the heat
treatment was performed prior to gold deposition. Results are interpreted in terms of
Ostwald ripening of vacancy clusters retained in the crystal from high temperature
processing. / Graduation date: 1996
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Factors affecting the movement and distribution of fluoride in aquifersUsunoff, Eduardo Jorge. January 1988 (has links)
This dissertation presents the results of laboratory experiments in which essential aspects of the movement of F- in saturated media have been addressed. The interactions between F-solutions and quartz, vermiculite, and kaolinite were studied through batch and column experiments. Quartz was found to react slightly with F⁻ , giving data described by a quasi-linear isotherm. Vermiculite adsorbed only minute amounts of F. A large uptake of F⁻ by kaolinite was measured. Ion exchange F⁻ by 0H⁻. may not have been the exclusive mechanism operating under the experimental conditions. The kinetics of the dissolution of fluorite (CaF₂) were investigated by means of batch and column tests. There appears to be a relationship between the dissolution rate and the mean flow velocity. Solution pHs greater than 5-6 may accelerate the dissolution process. For temperatures between 15 and 30°C, the dissolution is characterized by an activation energy of about 7 Kcal/mole, which would indicate that both surface reaction and transport are the rate-limiting step. The percolation of columns containing quartz, vermiculite, and kaolinite with multi-component solutions (including F⁻) resulted in a late breakthrough of F⁻ when compared with that of the other species. Circulation of distilled water led to an almost complete recovery of the F⁻ injected, which exited the column with relative concentrations greater than 1. When the packing included fluorite and distilled water was flushed through the column for 2 days, a concentration of F⁻ of about 1.3 pprn was rapidly reached and remained constant throughout the run. Multivariate analysis techniques (factor and correspondence analyses) were applied to data from two aquifers known to carry high F-waters. Although helpful in discriminating major and minor associations of species, none of those techniques could help unravel the behavior of F⁻ in the study aquifers. It is suggested that laboratory and field studies be continued and that, for the successful modeling of the movement and distribution of F⁻ in aquifers, non-linear source/sink terms should be included in the pertinent differential equation governing the transport of solutes.
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Whisker growth in electro-plated tin on copper. / 電鍍錫在銅質底材上晶鬚生長的硏究 / Whisker growth in electro-plated tin on copper. / Dian du xi zai tong zhi di cai shang jing xu sheng chang de yan jiuJanuary 2001 (has links)
by Chan To = 電鍍錫在銅質底材上晶鬚生長的硏究 / 陳濤. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Chan To = Dian du xi zai tong zhi di cai shang jing xu sheng chang de yan jiu / Chen Tao. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Content --- p.v / Chapter Chapter 1 --- INTRODUCTION / Chapter 1.1 --- Lead-free movement and the problem of whisker --- p.1-1 / Chapter 1.2 --- Properties of tin and tin-copper intermetallics --- p.1-2 / Chapter ´Ø --- Tin --- p.1-2 / Chapter ´Ø --- Tin-copper intermetallics --- p.1-2 / Chapter 1.3 --- Literature Review of Whisker --- p.1-4 / Chapter 1.3.1 --- Feature of the whisker --- p.1-4 / Chapter 1.3.2 --- Conditions prone to whisker growth --- p.1-8 / Chapter 1.3.3 --- Growth mechanism of the whisker --- p.1-10 / Chapter 1.3.4 --- Methods to prevent or remove whisker --- p.1-11 / Chapter 1.4 --- Motivation & Aims of Studies --- p.1-12 / Chapter Chapter 2 --- EXPERIMENTAL & INSTRUMENTATION / Chapter 2.1 --- Sample Preparation --- p.2-1 / Chapter ´Ø --- Electroplating process --- p.2-1 / Chapter 2.2 --- Instrumentation --- p.2-6 / Chapter 2.2.1 --- Scanning Auger Microscope (SAM) analysis --- p.2-6 / Chapter ´Ø --- Experimental conditions --- p.2-9 / Chapter ´Ø --- Sample preparation for Auger analysis --- p.2-10 / Chapter ´Ø --- Depth profile analysis --- p.2-11 / Chapter ´Ø --- Mapping --- p.2-11 / Chapter ´Ø --- Line scan --- p.2-12 / Chapter 2.2.2 --- X-ray diffractometer (XRD) --- p.2-12 / Chapter 2.2.3 --- Scanning Electron Microscope (SEM) --- p.2-13 / Chapter Chapter 3 --- INFLUENCE OF CATHODIC/ANODIC ELECTROCHEMICAL CLEANING ON THE WHISKER GROWTH / Chapter 3.1 --- Introduction --- p.3-1 / Chapter 3.2 --- Theory --- p.3-2 / Chapter ´Ø --- Reactions occurring at the anode/cathode --- p.3-3 / Chapter 3.3 --- Sample description --- p.3-5 / Chapter 3.4 --- Results and discussion --- p.3-5 / Chapter ´Ø --- Surface morphology before electroplating --- p.3-5 / Chapter ´Ø --- Whisker observation --- p.3-7 / Chapter 3.5 --- Summary --- p.3-18 / Chapter Chapter 4 --- INFLUENCE OF COPPER CONCENTRATION IN THE PLATING BATH ON COPPER DIFFUSION AND WHISKER FORMATION / Chapter 4.1 --- Introduction --- p.4-1 / Chapter 4.2 --- Theory and Literature Review --- p.4-2 / Chapter ´Ø --- Diffusion kinetic --- p.4-2 / Chapter ´Ø --- Influence of solute atoms --- p.4-5 / Chapter 4.3 --- Sample description --- p.4-6 / Chapter 4.4 --- Results and discussion --- p.4-6 / Chapter ´Ø --- SEM observations --- p.4-6 / Chapter ´Ø --- Cross-sectional analysis --- p.4-8 / Chapter ´Ø --- Surface and depth profile analysis --- p.4-15 / Chapter ´Ø --- XRD analysis --- p.4-21 / Chapter 4.5 --- Summary --- p.4_24 / Chapter Chapter 5 --- ANNEALING EFFECT ON THE WHISKER GROWTH / Chapter 5.1 --- Introduction --- p.5-1 / Chapter 5.2 --- Theory and Literature Review --- p.5-2 / Chapter 5.3 --- Sample description --- p.5-3 / Chapter 5.4 --- Results and discussion --- p.5-4 / Chapter ´Ø --- SEM whisker observation --- p.5-4 / Chapter ´Ø --- Cross-sectional Auger analysis --- p.5-4 / Chapter ´Ø --- Surface and depth profile analysis --- p.5-16 / Chapter 5.5 --- Summary --- p.5-27 / Chapter Chapter 6 --- FORMATION MECHANISM OF THE STRIATION ON WHISKER / Chapter 6.1 --- Introduction --- p.6-1 / Chapter 6.2 --- Results and discussion --- p.6-2 / Chapter ´Ø --- Texture of the striation --- p.6-2 / Chapter ´Ø --- Time evolution in the surface morphology --- p.6-6 / Chapter ´Ø --- Stage of whisker growth --- p.6-6 / Chapter 6.3 --- Summary --- p.6-12 / Chapter Chapter 7 --- CONCLUSIONS & FUTURE STUDIES / Chapter 7.1 --- Conclusions --- p.7-1 / Chapter 7.2 --- Future studies --- p.7-3 / Reference
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Photon correlation spectroscopy studies of mutual diffusion in aqueous t-butyl alcoholEuliss, Gary W. January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
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Chloride penetration into concrete structures exposed to the marine atmosphereUnknown Date (has links)
Chloride ions present in the marine atmosphere contained in marine aerosols is
investigated for a relationship with chloride that accumulated into concrete. Chloride
profiles are conducted on several concrete mixes containing fly ash, silica fume, and slag,
with water to cementitious ratios of 0.35, 0.41, and 0.47. The chloride accumulation in
concrete samples exposed to the environment is investigated with relation to the chloride
deposition from the marine atmosphere measured via the wet candle test. Results indicate
a possible relationship for the total accumulated chloride in the concrete with the
accumulated chloride deposition (wet candle). Over the exposure periods, concrete
specimens with 50% slag addition and 0.47 w/cm had the lowest average rates of chloride
accumulation for deposition under 100 g/m2day. Chloride accumulation was lower in
concrete containing 20% fly ash and 8% silica fume with 0.35 w/cm for chloride deposition
rates over 200 g/m2day. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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Diffusion of selected radionuclides through Hanford Trench 8 soil materialSchwab, Kristen E. 17 October 2003 (has links)
Shallow land burial in vadose zone sediment at the Hanford Site in Washington is being
considered for the disposal of Category 3 low-level waste. A series of column
experiments were conducted to evaluate and model the performance of the soil
surrounding the trench encasement material for iodine-129 and technetium-99 by
evaluating the mobility of these nuclides through the surrounding Trench 8 soil. These
experiments were designed to determine effective diffusion coefficients for ¹²⁷I and ⁹⁹Tc
through the following system: from contaminated soil into uncontaminated soil. The
tests were performed at two different soil moisture contents to evaluate the effects of soil
moisture content on diffusion. This thesis describes the experimental methods and
presents the diffusion results for this media type. It was found that as the moisture
content increased the diffusion increased by an order of magnitude (iodine 4% and 7%
moisture content soil effective diffusion coefficients were 8.90E-08 and 1.84E-07 cm²/s
respectively, and technetium 4% and 7% moisture content soil diffusion coefficients were
7.61E-08 and 1.45E-07 cm²/s respectively). These results, in combination with other
diffusion systems results, will allow the development of release models and contaminant
migration models that can be used to estimate the long-term fate of dose-controlling
radionuclides that are or will be buried in solid waste burial trenches. / Graduation date: 2004
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Single and multiple rates of nonequilibrium diffusive mass transfer at the laboratory, field, and regional scales in the Culebra Member of the Rustler Formation, New MexicoFleming, Sean W. 27 October 1998 (has links)
Graduation date: 1999
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Production of bioethanol from wheat straw hydrolysate using reverse membrane bioreactor (rMBR) / Bioetanol produktion från vetehalm hydrolysat med användning av omvänd membranbioreaktorKhin San, Jessica January 2018 (has links)
The second-generation bioethanol production in which lignocellulosic material is used as feedstock faces some difficulties. Lignocellulosic materials have to be pretreated prior to fermentation. In the pretreatment stages several inhibitory compounds, which can negatively affect the metabolic and physiologic activity of the microorganism used, Saccharomyces cerevisiae, are released. Moreover, wild strains of Saccharomyces cerevisiae cannot co-utilize the hexose and pentose saccharides present in the lignocellulosic substrate. In this study, reverse membrane bioreactor (rMBR) was applied to address the difficulties faced in the secondgeneration ethanol production. Semi-synthetic medium and pretreated wheat straw slurry containing different level of glucose, xylose and inhibitor concentrations were fermented in rMBR using genetically-modified xylose-consuming S. cerevisiae. The diffusion rate of different substrates and metabolites during fermentation were measured and analyzed. The results showed that the application of rMBR facilitated simultaneous utilization of hexose and pentose sugars and enhanced the cell tolerance of the inhibitor present in the medium.
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Concrete diffusivity and its correlation with chloride deposition rate on concrete exposed to marine environmentsUnknown Date (has links)
The aim of this study was to investigate the diffusion of chloride ions into concrete samples that were exposed in scenarios that simulate the splash, tidal, atmospheric, and immersed portions of a marine structure. To study the atmospheric deposition, the project also investigated the relationship between chloride ion deposition on the wet candle and its accumulation into concrete samples. Results from the wet candle experiment indicated that between 2% and 45% of the chlorides deposited per square meter of exposed area could be found within the concrete samples. After 6 months, slag G1a blocks showed the most resistance to chloride penetration in the tidal and splash simulations. After 10 months of exposure, fly ash samples had the slowest rates of diffusion in the tidal simulation while the fly ash + silica fume samples and the slag samples measured similar rates of diffusion within the tidal zone. After 90 days of curing, cylinders composed of 20% fly ash & 8% silica fume measured the highest average resistivity values and were found to be less vulnerable to chloride ion penetration than the 20% fly ash and the 50% slag concrete through rapid migration tests. / by Victor Anthony Echevarria. / Thesis (M.S.C.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
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Correlation of Chloride Diffusivity and Electrical Resistance for Cracked ConcreteUnknown Date (has links)
The durability of Reinforced Concrete (RC) structures in the Marine environment is
causing serious concern in the structural infrastructure. Reinforced concrete structures,
exposed to aggressive environments, are expected to last with little or no maintenance for
long periods of time. However, one of the most serious environmental exposures that
causes degradation is Chloride Diffusion, due to shrinkage, atmospheric corrosion, and
tide-induced wet and dry conditions at the air-water interfaces of coastal structures.
Therefore, chloride diffusivity, which correlates with the electrical resistivity, has a
significant impact on the durability of concrete. Concrete chloride diffusivity has been
experimented by multiple agencies and researchers on sound concrete, but there is a
considerable need for investigation of the durability of cracked concrete in the marine
environment. The two test methods carried out are presented: Standardized American Society for Testing
and Materials (ASTM) C1202 for Rapid Chloride Permeability (RCP) and ASTM D257
for Surface Resistivity (SR), and Nordtest (NT) Build 492 for Rapid Chloride Migration
(RCM) and Bulk Resistivity (BR) for both sound (uncracked) and cracked (micro and
macro) concrete. The limitations of the ASTM method, due to measurements before the
steady-state migration is reached, does not account for leakage in cracked concrete, and the
heating of the specimen due to higher current that increase the conductivity are indicated.
The Rapid Chloride Migration test provides for the non-steady state of diffusion. Again,
Bulk Resistivity, in contradistinction to Surface Resistivity is more accurate for cracked
concrete. The correlation betweeen RCM-BR are plotted. Chloride Permeability/Migration
is an important parameter that governs the Durability of Concrete.
The principal contribution is the highlighting of the inadequacy of the current widely used
standard ASTM C1202 for diffusivity testing, and the need for revision with further
investigation. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
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