Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / Includes bibliographical references (leaves 202-210). / by Gerd Johan Maria Norga. / Sc.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1983. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Mica Grujicic. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (leaves 33-34). / Titanium-tantalum (Ti-Ta) alloys are likely to have a high biocompatibility and corrosion resistance that renders them novel materials of interest for biomedical applications[7, 14, 2]. With high strength and a low elastic modulus, Ti-Ta alloys have attracted attention as candidates for such uses as hip replacements[2]. A current challenge impeding use of these alloys is that, with a melting temperature of 3269 K, homogeneous alloys involving Ta are difficult to produce by conventional melting practice[3]. The objective of this work was to, as most structural changes occur via diffusion, gain insight into this matter through determination of the interdiffusivity in Ti-Ta alloys. A scanning electron microscope was utilized to perform energy dispersive x-ray analysis on Ti-Ta alloy samples in the range of 20 to 60 weight percent (wt %) Ta. A computational model that employed Fick's Second Law was used to extract interdiffusivity values from the data. Interdiffusivity values, which ranged from 4.0. 10-13-Tfor 20 wt % Ta to 3.0. 0-14- for 60 wt % Ta, exhibited a systematic variation with composition. The interdiffusion coefficient was seen to decrease with increasing weight fraction Ta. / by Jennifer C. Dibbern. / S.B.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001. / Includes bibliographical references (p. 123-129). / In this thesis, we investigated the mechanical behavior of small volume structures, with specific application to thin metal films and patterned metal lines on substrates. The first part of this investigation dealt with the elastoplastic behavior of interconnect lines during thermal cycling. A robust computational method was developed to predict volume-averaged stresses in unpassivated and passivated lines in response to changes in temperature, as a function of line geometry, material properties and thermal history. The computational model also facilitated the extraction of substrate curvature. In addition, a simple analytical method was developed to allow extraction of volume-averaged stresses in unpassivated lines upon yielding due to thermal stresses, via experimental curvature methods. The second part of the investigation involved the systematic nanoindentation of a wide range of FCC single crystals and polycrystals, in bulk and thin film form. For shallow (</= 100 nm) depths, the experimentally obtained P-h curves displayed elastic loading portions alternated with inelastic displacement bursts, for all specimens. The bursts were attributed to dislocation nucleation and motion within the crystal, which occurred when stresses underneath the indenter tip approached the critical shear strength of the material. Theories of dislocation activity were confirmed with planar TEM photos of nanoindented Cu films. In order to examine the atomistics of such phenomena, an experimental 2-D atomic simulation was developed, via an extension of the classical soap bubble raft, to simulate elastic contact and defect nucleation at low loads. Dislocation nucleation inside crystals of low defect density, ostensibly requiring stresses on the order of the theoretical shear strength, was found to occur under blunt indenters, providing a mechanistic justification for bursts observed during nanoindentation experiments. Finally, the experimental nanoindentation results for thin films were analyzed in the context of elastoplastic indentation, incorporating elastic loading and inelastic bursts. Stiffnesses thus obtained were found to increase as film thickness decreased, displaying a similar trend to literature thin film strength values obtained via substrate curvature methods. / by Andrew Gouldstone. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 48-50). / The understanding of the brain would be revolutionized by a tool that can measure intra- and extra-cellular electrical potentials on a parallelized scale, without disrupting the neural physiology. Existing technologies do not sufficiently carry out these functions. Using a thermal drawing process (TDP), multimaterial fibers comprised of polymer-metal composites can be fabricated to create flexible, microelectrode arrays. These fibers can be further processed after the TDP, using selective etching to reduce the diameter of the probe. These devices have been implanted and have been used to record neural activity in vivo while evoking minimal tissue response. Additionally, electrodeposition of biocompatible metals onto the fiber-electrode tips can be implemented to increase the signal-to-noise ratio (SNR). Here, I describe the electroplating of gold onto the fiber-tips of tin and tin-indium electrodes, which were drawn using TDP. By adjusting the electrodeposition conditions, the electrode tip geometries can be tuned to optimize the interface between the device tips and neuronal membranes. / by Christina M. Tringides. / S.B.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995. / Includes bibliographical references (leaves 32-33). / by Christopher S. Rice. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1995. / Includes bibliographical references (leaves 113-116). / by Fanqi Gan. / M.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004. / Includes bibliographical references (leaves 19-20). / Self-assembling peptides are quickly proving themselves useful in tissue engineering and most recently, electronics. Self-assembling peptides have been shown to form a network of nanofibers that can be used in scaffold research or as templates for nanowires. However, self-assembling peptides have not been widely studied and further research is needed to fully understand the properties and organization of the peptide hydrogels. Much research has been conducted with single cell type scaffolds; however, the next step is to develop multiple cell type scaffolds. In addressing this next step, I studied mixtures of in-solution peptides using atomic force microscopy to characterize nanofiber formation. My results showed that when RID12 peptide was introduced into a mixture with RAD16 peptide, there was a decrease in the average fiber length. Increasing the percentage of RID12 resulted in a further decrease in fiber length. Presumably, RID12 interacts with RAD16, thereby disrupting fiber elongation. Further research is necessary to understand this interaction. / by Devon Charlton. / S.B.

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.