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Controlled Release of Alkalinity Using pH-Responsive Polymer CarriersMartin, Christopher S. 26 October 2016 (has links)
<p> Low groundwater pH is frequently cited as inhibiting the performance of in-situ bioremediation of chlorinated solvents at contaminated sites. A common method of pH control is injection of solutions containing alkalinity, but alternatives for prolonged, passive pH control are needed. This work explores pH-responsive hydrogel coatings on MgO nanoparticles as vehicles for controlled release of alkalinity. Chitosan cross-linked with glutaraldehyde was evaluated as a representative hydrogel coating. The effects of coating thickness and cross-linking on the rate of alkalinity release were experimentally evaluated using batch dissolution experiments. Dissolution rates were found to be up to an order of magnitude slower for coated particles than for uncoated particles. A diffusion model was developed for the dissolution rate of coated particles, and the model was able to account for the dissolution rate as a function of coating thickness over a range of pH.</p>
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Structural analysis and characterization of synthesized ordered mesoporous silicate (MCM-41) using small angle X-rays scattering and complementary techniquesAkinlalu, Ademola V. 29 September 2016 (has links)
<p> Mesoporous silicate have widespread potential applications, such as drug delivery, supports for catalysis, selective adsorption and host to guest molecules. Most important in the area of scientific research and industrial applications is their demand due to its extremely high surface areas (> 800<i>m</i><sup> 2</sup><i>g</i><sup>−1</sup>) and larger pores with well defined structures. </p><p> Mesoporous silicate (MCM-41) samples were prepared by hydrothermal method under various chemo-physical conditions and various experimental methods such as small angle X-rays scattering (SAXS), Nitrogen adsorption-desorption analysis at 77 K, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to investigate the changes in the structural morphology and subtle lattice parameter changes. With regards to the subtle changes in the structural characteristics of the synthesized mesoporous silicate, we seek to understand the electron density function changes as the synthesis parameter are varied from low molar concentration of ATAB/Si to higher concentration, the system becoming more acidity due to increase in the hydrolysis time of pH regulator as a result of increased production of ethanol and acetic acid and the changes due to extended reaction time. </p><p> This Ph.D. research tries to understand the influence of various parameters like surfactant-Si molar ratio, reaction time, and the hydrolysis of the pH regulator on the orderliness/disorderliness of the lattice order, lattice spacing and electron density function. The stages during synthesis are carefully selected to better understand where the greater influence on the overall structural morphology exist so as to be able to ne tune this parameter for any desired specification and application. </p><p> The SAXS measurement were conducted on a HECUS S3-Micro X-ray system at Rensselaer Polytechnic Institute, Troy, NY. while the data evaluation and visualization were carried in 3DView 4.2 and EasySWAXS software. The electron density functions were generated with a proprietary software called edens. </p><p> In this dissertation, the following observations have been revealed resulting from SAXS measurement. </p><p> 1. As one increases the hydrolysis duration of ethyl acetate, a gradual collapse of the lattice spacing of the mesoporous silcate MCM-41 is observed. We found from SAXS that there is a slight right shift of the spectra toward the higher q-values indicating that we are gradually losing orderliness in the lattice spacing and hexagonal structure of the mesoporous silica. Also, the intensity of the peak of second and third peaks are diminutive when compared to sample with shorter hydrolysis time. </p><p> 2. A comparison of the SAXS spectra for the different molar concentration sample reveals that the 0:5M samples shows a deteriorating structural characteristics as compared to the 0:25 and 0:75M samples respectively and a clear decrease in the (100) reflection planes. Also noticed is the slight rightward shift in the overall spectrum prole. This observation suggest that further analysis is needed so as to better understand the result. </p><p> 3. We establish that during MCM-41 synthesis, longer reaction time is needed to produce quality sample with well defined structurally characteristic for its intended application because according to spectrum for the sample with a longer reaction time (aging), a shift towards the lower q-values indicates that a sample with a larger lattice parameter and wall thickness but the intensities of its peak are diminishing when compared to the other of relatively shorter reaction time. </p><p> Other complementary techniques were used to corroborated the result obtained from SAXS. Nitrogen adsorption-desorption analysis at 77K was used to generate the isotherms while B.E.T method was used in conjunction with the isotherms to obtained the very important surface area information. SEM provide a visual structural morphology of the samples and FTIR gave the fingerprint detail of the bonds and vibration types between particle present.</p>
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Biotemplated resin and carbon nanomaterials for energy and environmental applicationsZhang, Geran. January 2018 (has links)
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 171-185). / The M13 bacteriophage had been shown to be a highly versatile toolkit for growing and assembling nanomaterials with technological importance. Inspired by the natural biomineralization process, much of the existing literature focused on genetically engineering the M13 viral capsid for interaction with inorganic materials, such as metals and oxides. In this thesis, the utility of the M13 toolkit was extended to the synthesis of organic and carbonaceous materials. Biotemplating of phenolic resins was extensively studied, with a particular focus on colloidal assembly and materials chemistry. Genetically engineered M13 bacteriophage was shown to be particularly apt at controlling the morphology and selfassembly of phenolic resin nanofibers. The properties of these nanomaterials could be simultaneously controlled by introducing additional molecular moieties using simple aqueous, organic chemistry, to enable their application as catalyst scaffolds and carbon dioxide sorbents. / Modification of the phenolic resin nanofibers with organosilicon moieties offered a direct route to nanoporous carbon nanofibers upon carbonization. The properties of these biotemplated carbon nanofibers could be tailored for specific applications by independently controlling morphology and carbon texture. Their practical utility was demonstrated by the rapid adsorption of small molecules with uptake values comparable to some highest values reported for carbon materials. High conductivity nanofibers could also be incorporated into lithium-sulfur batteries as interlayers to significantly improve electrochemical performance. New biotemplating approaches to the synthesis of some other inorganic nanomaterials such as zinc sulfide and noble metal nanomaterials were also demonstrated. Biotemplated zinc sulfide nanofibers were shown to be promising anode material for sodium-ion batteries, with potential for further study. / The facile synthesis of a range of noble metal nanowires opens up potential applications in catalysis and energy storage. / by Geran Zhang. / Ph. D. / Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
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Modification of solidification structures by pulse electric dischargingNakada, Masayuki January 1985 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985. / Bibliography: leaves 83-85. / by Masayuki Nakada. / M.S.
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Sol-gel derived tantalum oxide thin filmsSilverman, Lee Arnold, 1959- January 1987 (has links)
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Vita. / Bibliography: leaves 183-185. / by Lee Arnold Silverman. / Ph.D.
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Kinetics of deformation-induced transformation of dispersed austenite in two alloy systemsKuroda, Yukio January 1987 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Bibliography: leaves 89-92. / by Yukio Kuroda. / M.S.
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Finite element modeling of the human eyeChan, Venetia (Venetia V.) January 2001 (has links)
Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2001. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 37-38). / A three-dimensional finite element model was created to analyze the mechanical interactions between the various substructures within the human eye. During certain activities, mechanical interactions may lead to a resultant distribution of stresses within the eye that may in turn produce various retinal diseases. The entire eye was modeled using dynamic finite element analysis to incorporate the mechanical effects of all of the substructures on the retina. A set of mechanical properties for each substructure was determined from previously published studies. Saccadic motion was modeled in the normal human eye to determine the location and magnitude of peak stresses in the retina and optic nerve head during initial loading. After 0.6125 ms, stresses as high as 5.4 x 10⁷ Pa were reached. The peak stresses occurred in the portions of the retina and the optic nerve head close to the boundary between these two substructures. / by Venetia Chan. / S.B.
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Wetting of ceramic particulates with liquid aluminum alloysOh, Se-Yong January 1987 (has links)
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Bibliography: leaves 97-98. / by Se-Yong Oh. / Ph.D.
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Growth and characterization of high-purity and iron-doped photorefractive barium titanateSchunemann, Peter Gerard January 1987 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 71-75. / by Peter Gerard Schunemann. / M.S.
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X-ray photoelectron spectroscopy of silicate glassesTasker, G. William January 1987 (has links)
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographies. / by G. William Tasker. / Ph.D.
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