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

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.

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

Typescript (photocopy). / Digitized by Kansas Correctional Industries

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

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

Graduation date: 1999

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.

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.

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