Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / Includes bibliographical references (leaf 54). / Twenty - first opportunities for Gigascale Integration will be governed in part by a hierarchy of physical limits on interconnect. Microprocessor performance is now limited by the poor delay and bandwidth performance of the on - chip global wiring layer. This thesis is envisioned as a critical showstopper of electronic industry in the near future. The physical reason behind the interconnect bottleneck is the resistive nature of metals. The introduction of copper in place of aluminum has temporarily improved the interconnect performance, but a more disruptive solution will be required in order to keep the current pace of progress, optical interconnect is an intriguing alternative to metallic wires. Many - core microprocessors will push performance per chip from the 10 gigaflop to the 10 teraflop range in the coming decade. Pin limitations, the energy cost of electrical signaling, and the non - scalability of chip - length global wires are significant bandwidth impediments. Silicon nanophotonic based many core architecture are introduced in order to meet the bandwidth requirements at acceptable power levels. / by Zhoujia Xu. / 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 147-157). / The long-term goal of my Ph.D. study has been controlling the self-assembly of various materials using state-of-the-art nanofabrication techniques. Electron-beam lithography has been used for decades to generate nanoscale patterns, but its throughput is not high enough for fabricating sub-10-nm patterns over a large area. Templated block copolymer(BCP) self assembly is attractive for fabricating few-nanometer-scale structures at high throughput. On an unpattermed substrate, block copolymer self-assembly generates dense arrays of lines or dots without long-range order. Fortunately, physical features defined by electron lithography can guide the self-assembly of block copolymer. In our previous work, the orientation of cylindrical phase block copolymer was controlled simply by changing the distance between physical features, and resulting polymer patterns were analyzed by an image analysis program. Here, we first demonstrated high throughput sub-10-nm feature sizes by applying the same approach to a cylindrical morphology 16kg/mol PS-PDMS block copolymer. The half-pitch of the PDMS cylinders of this block copolymer film is 9 nm, so sub-10-nm structures can be fabricated. We also applied the similar approach to a triblock terpolymer to achieve dot patterns with square symmetry. To achieve a more complex pattern, electron-beam induced cross-linking of a block copolymer and second solvent-annealing process was used. By using this method, a line-dot hybrid pattern was achieved. Despite that the block copolymer self-assembly area had been heavily studied, researchers had yet to ascertain how to design nanostructures to achieve a desired target pattern using block copolymers. To address this problem, we developed a modular method that greatly simplifies the nanostructure design, and using this method, we achieved a circuit-like block-copolymer pattern over a large area. The key innovation is the use of a binary set of tiles that can be used to very simply cover the desired patterning area. Despite the simplicity of the approach, by exploiting neighbor-neighbor interactions of the tiles, a complex final pattern can be formed. The vision is thus one of programmability of patterning by using a simple instruction set. This development will thus be of interest to scientists and engineers across many fields involving self-assembly, including biomolecule, quantum-dot or nanowire positioning; algorithmic self-assembly; and integrated-circuit development. We applied this concept - controlling the assembly of materials using nanostructures - to a different material, protein. Single-molecule protein arrays are useful tools for studying biological phenomena at the single-molecule level, but have been developed only for a few specific proteins using the streptavidin-biotin complex as a linker. By using carefully designed gold nanopatterns and cysteine-gold interaction, we developed a process to make single-molecule protein arrays that can be used for patterning a broad range of proteins. / by Jae-Byum Chang. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994. / Includes bibliographical references (leaves 174-180). / by Ambuj D. Sagar. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 78-80. / by Adebisi Oladimeji Oladipupo. / Sc.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, June 2005. / Includes bibliographical references (p. 38-39). / In this thesis, the chemical/mechanical properties and biocompatibility of gelatin were investigated to produce a gelatin scaffold for the release of bone morphogenetic proteins (BMPs) from composite particles. This delivery system, designed to regenerate bone, holds much promise as an alternative to bone grafts. The chemical properties of gelatin were examined through zeta potential measurements, swelling studies, optical microscopy, environmental scanning electron microscopy (ESEM), and collagenase degradation. Compressive tests and mercury porosimetry were performed to study the mechanical and structural properties of the scaffold. The biocompatibility of the scaffold was determined through cell optical imaging and DNA quantification studies. Based on findings of this research, the material choices were made and the synthesis method for the gelatin scaffold was developed. Gelatin A, 300B, derived from bovine collagen, with an isoelectric point of [approx.] 9, was selected. Crosslinking was accomplished by reacting 10 w/v% glutaraldehyde with 10 w/v% gelatin solution. The most effective crosslinking condition was found to be 5 hours at room temperature. Glycine rinses were conducted to cap any non- reacted (toxic) aldehyde groups, and the necessary length of time was found to be at least 48 hours at 37⁰C. Finally, based on pore size distribution and mechanical stability, an optimal lyophilization method was developed with initial freezing at -20⁰C for 1 day, followed by lyophilization of the scaffold for 1-2 days. In terms of mechanical properties of the gelatin and amount of protein delivered, the most effective loading of poly(lactic-co-glycolic acid)/apatite/protein composite particles was found to be 10% of the mass of the gelatin. / by Elizabeth A. Hager. / S.B.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / by Andrew Gouldstone. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Vita. / Bibliography: v. 2, leaves 324-359. / by Steven Anthony Gedeon. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Includes bibliographical references. / (cont.) The elastic anisotropy and yield surfaces are fully characterized, and numerical equations are developed to allow the simple evaluation of the effect of geometric and material properties on the mechanical behavior of hollow-sphere foams. The analysis indicates that at relative densities of 10%, hollow-sphere foams have theoretical moduli and strengths that are three times those of existing metallic foams, and this increases to a factor of ten at relative densities below 5%. Several concepts are presented to allow the incorporation of defects into the model, including random packing, variations in bond size, and variations in sphere relative thickness. Finally, the performance of hollow-sphere foams is compared to other low-density engineering materials on a structural basis; hollow-sphere foams offer a beneficial alternative. / Metal foams are low-density materials with multifunctional attributes that make them appealing for numerous uses, including thermal insulation, heat sinks, acoustic insulation, energy absorption devices (crash protection), lightweight structural sandwich panels (as the core material), and vibration damping devices. Metallic foams are commercially available as closed-cell and open-cell foams. Unfortunately, the mechanical behavior of closed-cell metallic foams is far below that which the theory suggests; at low relative densities, the mechanical properties of closed-cell foams are an order of magnitude less than expected. It is shown that defects such as cell wall curvature, cell wall corrugation, and density variations account for a large fraction of the degradation in properties. Hollow-sphere foams offer a solution to the problem of degraded performance in closed-cell foams because ideal spheres can be bonded into a relatively defect-free structure. This thesis focuses on the development of constitutive models to describe the mechanical behavior of this new class of materials; such models are critical in determining whether or not hollow-sphere metallic foams provide an alternative to existing closed-cell metallic foam materials. The uniaxial compression behavior of single hollow spheres is first studied to determine the significant geometric and material parameters of hollow-sphere foams. Detailed constitutive models of the behavior of hollow-sphere foams are developed using finite element simulations of simple cubic, body-centered cubic, and face-centered cubic sphere packings. / by Wynn Steven Sanders. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / In title on t.p., superscript "TM" follows "S-3DP". / Includes bibliographical references. / GRIN lenses with vertical index variation and radial index variation have been successfully fabricated using S-3DPTM. Two silica-based material systems, A1203-SiO₂ and BaO-SiO₂, have been studied and used for the fabrication of GRIN lenses. Aluminum nitrate was dissolved in water to provide the dopant salt solution for S-3DPTM. The pre-sintering treatment at 1000 ⁰Cfor 24 hours in. vacuum (-5x10-6 torr) was used to remove the hydroxyl groups that cause bubbles during sintering. The sintering condition for the A1203-SiO₂ material system was found to be 1650 ⁰C for 30 minutes in vacuum. Two alumina-doped silica GRIN lenses with vertical index variation, Design 1.63 [percent] max and Design 2.5 [percent] max, were fabricated with effective focal lengths of 10.00 cm and 6.10 cm, respectively. An alumina-doped silica GRIN lens with radial parabolic index variation also was fabricated with effective focal lengths of 63.75 cm in the x direction and 52.50 cm in the y direction. The BaO-SiO₂ material system, which has a 2.4 stronger index changing ability than the A1203-SiO₂ material system, also was developed. Barium acetate was used as the dopant source. The pre-sintering treatment was found to be 900 ⁰C for 18 hours in air to convert barium acetate to barium oxide. The sintering condition was found to be 1725 ⁰C for 10 minutes in vacuum. A barium oxide-doped GRIN lens with radial parabolic index variation was fabricated. Its effective focal length was measured to be 14.63 cm in the x direction and 11.14 cm in the y direction. The barium oxide concentration profiles were measured. The theoretical focal lengths were calculated and compared with the effective focal lengths. / by Hong-Ren Wang. / Ph.D.

Thesis (S.M.)--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 (p. 109-116). / Shifts in global and political climates have led industries worldwide to search for more environmentally sound processes that are still economically viable. The steel industry is studying the feasibility of molten oxide electrolysis, a novel process by which molten iron and gaseous oxygen are the products; no carbon dioxide is produced at the site of the electrolysis cell. The research presented in this thesis focuses on the anodic reaction and the preliminary development of an inert anode, as well as investigations into the mechanism of the oxygen evolution reaction. Various elements have been considered with the platinum group metals possessing the best combination of physical properties to serve as the inert anode. Cyclic voltammetry at 1575°C was used to compare the candidates. Iridium yielded the highest current density at a given overpotential followed by rhodium and platinum regardless of the composition of the electrolyte. Speculation as to metal oxide intermediate phases formed and mechanisms for the oxygen evolution reaction are discussed. Notably, the basicity of the molten aluminosilicate electrolyte was found to greatly influence the rate of oxygen gas evolution as evidenced by the linear dependence of the current density on optical basicity. This is crucial for the design of a full-scale electrolysis cell as improved kinetics of the anodic reaction will yield higher throughput and/or enhanced power efficiency. Combining our finding of the relationship between current density and basicity with previous authors' contributions on the effect of partial pressure of oxygen, we argue that to a first approximation, the magnitude of the current density is governed by the concentration of free oxide ions and by the partial pressure of oxygen in the headspace above the melt. / (cont.) Lastly, to, in part, address the disparate natures of the interests of steelmakers, glassmakers, geochemists, and electrochemists, the difficulties in performing electrochemical measurements at extremely high temperatures (~1600°C), and the absence of a comprehensive review of the last sixty years of work on oxygen evolution from molten silicates, this thesis is intended to serve as an essential guide for future work in this field. / by Andrew J. Gmitter. / S.M.