Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (leaves 35-37). / Implicit, explicit and spectral algorithms were used to create Allen-Cahn and Cahn-Hilliard phase field models. Individual terms of the conservation equations were approached by different methods using operator splitting techniques found in previous literature. In addition, dewetting of gold films due to surface diffusion was modeled to present the extendability and efficiency of the spectral methods derived. The simulations developed are relevant to many real systems and are relatively light in computational load because they take large time steps to drive the model into equilibrium. Results were analyzed by their relevancy to real world applications and further work in this field is outlined. / by Matthew Dane Handler. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Leaves 87 and 88 blank. / Includes bibliographical references. / Supercritical Water Oxidation (SCWO) is a promising technology for destroying highly toxic organic compounds present in aqueous waste streams. Organic wastes that have been identified as possible targets for destruction by SCWO include EPA-regulated organic wastes, organic components of DOE mixed low-level radioactive wastes, and DOD chemical weapons stockpiles. SCWO capitalizes on the properties of water in the supercritical phase to affect spontaneous and rapid oxidation of hydrocarbons to form CO2, H2O, and, depending on the species of heteroatom present in the organic waste, one or more acids. HCl, H2SO4, and H3PO4 are the acids most frequently encountered in SCWO process streams. The formation of acids in SCWO feeds at high temperatures and pressures under highly oxidizing conditions leads to severe corrosion of the process unit for even the most corrosion resistant constructional alloys. Currently, the existence of a constructional material that can withstand the extremely aggressive conditions present in all sections of the SCWO process stream for all candidate organic wastes is extremely unlikely. Previous attempts to identify such materials have proved unsuccessful. This has led to more fundamental research addressing physical chemistry, electrochemistry, and corrosion phenomena in aqueous systems under hydrothermal conditions. This review addresses this research as it pertains to SCWO technology, and based on these findings, discusses potential methodologies for reducing corrosion damage in SCWQ systems. Currently, it appears that proper selection and/or development of construction materials in conjunction with precise control of feed stream chemistry may be a promising option for corrosion control in SCWO process environments. / by Christopher R. Sydnor. / S.M.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003. / Includes bibliographical references (leaves 46-48). / Synthetic sheet polarizers have a wide range of purposes, primarily in liquid crystal displays (LCD), in particular those with anti-glare and contrast-enhancing applications. Current polarizers do not perform to their full potential due to "leakage" in the red and blue parts of the spectrum, where light in the axis of polarization is inefficiently transmitted at wavelengths along the edge of the visible light spectrum. The absorption peaks can be spread to absorb light at the outer visible wavelengths by adding dichroic dyes to correct the blue (400-450 nm range) or red leakage (620-660 nm). This project covers experimentation to determine the value of these process additions and to further the understanding of the new mechanisms and the improvements they bring. This new polarizer is still in the technology development phase, but could be commercialized with these advances, giving 3M a competitive advantage in the current polarizer industry and in new applications which demand high durability and truer blacks. / by Stephanie K. Dalquist. / M.Eng.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 121-129). / This thesis describes the development of a novel in vitro model of monocytes transmigration under flow and use in the study of early molecular events of atherogenesis. In this work, we focused on how endothelial dysfunction, specifically mediated by disturbed flow from atherosusceptible regions of the vasculature, is both communicated to recruited monocytes as they reside in the subendothelial matrix, and how reciprocally, monocytes may exacerbate the endothelial dysfunctional state. We built and integrated our in vitro model to a unique flow apparatus that can precisely replicate atheroprone and atheroprotective shear stress waveforms. We carefully characterized the model that relies on a fibronectin-coated collagenous matrix seeded with a confluent monolayer of endothelial cells co-cultured with THP- 1 monocytes under flow. We used the model to draw biological insight from endothelial:monocyte co-cultures under flow. We found that monocytes preferentially accumulate on endothelial monolayers exposed to atheroprone flow. We also observed the upregulation of IL-1[beta] in endothelial cells exposed to atheroprone flow when co-cultured with monocytes but not in endothelial cells alone, in each of three independent experiments; yet the aggregated results are not statistically relevant due to variability. Flow-driven dysfunctional endothelium recruits and interacts with monocytes that soon after transmigration become dysfunctional foam cells. Our novel in vitro model that congregates endothelial cells, monocytes and flow responds to the pressing need to understand the interplay between these protagonist cells during atherogenesis, and allowed us to define further monocyte- and flow-mediated transition of endothelium from normal to dysfunctional to diseased states. Harnessing the power of a versatile platform of transmigration under flow may foster the discovery of novel targets for atherogenesis and the development of original therapeutic strategies. / by Alexis S. Turjman. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references. / Biological systems inherently posses the ability to synthesize and assemble nanomaterials with remarkable precision, as evident in biomineralization. These unique abilities of nature continue to inspire us to develop new approaches of nanobiotechnology to integrate advanced materials into medicine and electronics. Particularly, peptides are believed to play an important role in biotemplating and biological self-assembly. In order to understand the interface between inorganic materials and peptides and realize biological self-assembly, this work adopted M13 virus as a model system. The genetic engineering of M13 viruses enables us to grow various nanomaterials and achieve virus monolayer assembly on charged polyelectrolyte multilayers. The fundamental understanding and new discoveries obtained by this work can mature into an engineering discipline demonstrating that biological approaches may represent a new paradigm to provide novel technological advantages. The use of a biological template for a nanostructured battery electrode ramps up the device's performance and scales down its overall size. This work presents a new way of exploiting biological entities for the bottom-up assembly of battery devices by utilizing biological self-assembly and biotemplating. Viruses are genetically engineered such that they function as a toolkit for constructing the battery. / by Ki Tae Nam. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Mark Gregory Steckel. / M.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (leaf 22). / This work builds on the initial design of a polymer microchip for controlled-release drug delivery. Currently, the microchip employs a nonbiodegradable sealant layer, and the new design aims to fabricate it only of biodegradable parts. Experiments were conducted to evaluate two potential designs that are fabricated via lamination, and a final design was proposed based on the results. Design 1 sought to replace the sealant directly with a PLA backing layer, but the laminated backing layer was found to leak in 14C-dextran release experiments. Design 2 used a laminated film instead of the original injected membrane. The laminated film was optimized to a 200- [mu]m thick poly(D,L-lactic-co-glycolic acid) 2A membrane, and the film-laminated microchip was shown to release 14C-dextran within a 40-day period. The final proposed design was based on Design 2, which demonstrated more potential as a future means of drug delivery. / by Jina Kim. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (v. 2, p. 343-355). / Previous experimental research into ancient pottery production has proven that potters can produce vessels with varying materials properties, such as thermal shock resistance and permeability. These properties are differentially useful for certain tasks, such as cooking or water-cooling. In certain cases, such as the use of shell temper in North America, an improvement in thermal shock resistance seems to provide an explanation for why the new temper was adopted along with the introduction of a new food type -- maize. It remains an unanswered question, however, whether potters in a large variety of situations were choosing to alter their production techniques or materials to produce pots intended for different functions that exhibit different materials properties. I investigated this question by applying techniques and concepts from materials science, anthropology, and archaeology. This combination of materials science and social science was pioneered by Heather Lechtman and Dorothy Hosler, and is called the "materials approach." My research focuses specifically on pottery production in the Middle Balsas Region of Guerrero, Mexico, from approximately 300 BC to AD 1300. I investigated whether potters in the Middle Balsas were using different production techniques or raw materials for vessels that were intended for specific functions. I chose the Middle Balsas Region as the geographical focus for my research because little systematic archaeological investigation has focused on that area, especially in the Late Preclassic and Classic periods (300 BC-AD 900). In order to gather appropriate data, I mapped, surface collected, and excavated at three Middle Balsas sites. I then categorized the pottery and analyzed a selected portion via thin section analysis/petrography. / (cont.) The combination of field work and laboratory analyses that I used provided me with data on the production techniques practiced by Middle Balsas potters and allowed me to identify what wares and vessel shapes were characteristic of various time periods. I determined that Middle Balsas potters produced a consistent set of wares and vessel shapes made from a variety of clay sources, and that the clays I identified in their vessels always contained a consistent volume fraction of non-plastic inclusions. The majority of the clays used in these vessels naturally contain the high levels of non-plastic inclusions identified. When the clays did not contain this volume fraction of inclusions, the potters added a sand temper to the clays to reach their "ideal" volume fraction. The consistency that I identified in the production of Middle Balsas pottery lasted over one thousand years, which is unusual in Mesoamerica. I suggest that this production pattern may have occurred because a small number of potters who used a specific, shared technique made the vessels for the entire community. / by Jennifer L. Meanwell. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (p. 127-134). / Grain boundaries are known to play a role in many important material properties including creep resistance, ductility and cracking resistance. Although the structure and properties of individual boundaries are important, the overall behavior of the material is determined largely by the connectivity of grain boundaries in the microstructure. Grain boundary networks may be studied in the framework of percolation theory by classifying boundaries as special or general to the property of interest. In standard percolation theory, boundaries are randomly assigned as special or general; however, this approach is invalid in realistic grain boundary networks due to the requirement for crystallographic consistency around any closed circuit in the microstructure. The goal of this work is to understand the effects of these local constraints on the connectivity and percolation behavior of crystallographically consistent grain boundary networks. Using computer simulations and analytical models, the behavior of crystallographically consistent networks is compared to that of randomly-assembled networks at several different length scales. At the most local level, triple junctions and quadruple nodes are found to be preferentially coordinated by special and general boundaries, leading to nonrandom network topologies that are quantified using topological parameters. / (cont.) Although the properties of the simulated microstructures, including connectivity length and average cluster radius of gyration, are described by the same scaling exponents as in standard percolation theory, the amplitude prefactors in the scaling relationships are changed as a result of the crystallographic constraint. The percolation threshold, an important parameter in microstructural design, is also found to differ from that of standard percolation theory by as much as ±0.05. Although all of the simulated grain boundary networks studied here are distinctly nonrandom, no two cases have the same behavior, the details of which depend strongly on the specific microstructural model. Therefore, a unified approach for locally correlated percolation problems is developed that allows the effects of the requirement for crystallographic consistency to be compared directly from system to system. This new approach can be extended beyond the study of grain boundary networks to include other locally-correlated percolation problems. / by Megan E. Frary. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student submitted PDF version of thesis. / Includes bibliographical references (p. 175-179). / The dewetting of solid metal polycrystalline films to form metal nanoparticles occurs by the nucleation and growth of holes in the film. For typical films on flat substrates, this process is not well-controlled and results in nanoparticles with nonuniform spatial and size distributions. Topographic substrates consisting of di-periodic inverted pyramid arrays and mono -periodic v-groove gratings of oxidized silicon were used to modulate the surface curvature of as-deposited polycrystalline gold films and control the dewetting process. The morphology of films dewetted on topographic substrates was found to depend on the both the relative geometry of the substrate and film thickness. Relatively thick films dewetted out of the pits and grooves prior to breaking up into particles while thinner films pinched off to form particles in the pits and grooves. If the pits or grooves were far apart, the pinch off also resulted in particles forming on the mesas between the pits. If the pits or grooves are close together, all the material pinches off into the topography. In the case of the inverted pyramids, this resulted in spatially ordered arrays of nanoparticles with narrow size distributions. A model that explains and predicts the effect of the relative geometry was developed based on competition between curvaturedriven evolution of the film-atmosphere interface and the dewetting of the film-substrate interface. It was also found that particles in both types of topographic substrates are strongly crystallographically oriented both out of the plane of the substrate and in the plane of the substrate despite the lack of an epitaxial relationship with the amorphous template. / (cont.) During the solid-state dewetting process, the growth of holes in the film is accompanied by material accumulation along the edge of the hole. Investigation of the dewetting edge at early stages revealed that the accumulation occurs unevenly in individual grains. Electron backscatter diffraction revealed that the unevenness is not due to grain orientation. / by Amanda L. Giermann. / Ph.D.