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.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001. / Includes bibliographical references (leaves 124-126). / Tubular hydroforming is gaining importance in the automotive industry by enabling parts consolidation, weight reduction and performance enhancement. While current automotive applications use almost exclusively mild steel, other advanced steel and aluminum alloys are being discussed for use in the future. This thesis evaluates the economics of hydroforming three representative materials - mild steel, dual phase 600 steel and aluminum 5754 - using technical cost modeling. Costs are analyzed for the entire hyclroforming value stream, from coiled metal sheets to hydrofonned components, for both geometrically equivalent and functionally equivalent hydroformed components. Design conditions of constant load to failure and constant defection are used to derive functional equivalence. Results show that manufacturing costs are most sensitive to the maximum calibration pressure required for hydroforming. While the costs of processing aluminum components are less than those of functionally equivalent steel components, greater aluminum raw material costs of lead to greater total component costs compared to steel. Substitution of advanced materials is not as cost effective a weight reduction strategy as increasing section diameter and thinning walls of mild steel components, assuming no package constraints. / by Bruce A. Constantine. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017. / 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 (page 31). / Both biological and synthetic materials crosslinked via metal coordinate dynamic chemistry display interesting advanced behavior. In particular, coordinate networks have been shown to form self-healing, self-assembling, and stimuli-responsive behaviors through its tunable optical and mechanical properties as well as its ability to for dynamic networks. However, while the majority of research has focused on characterization of bulk coordinate networks, coordinate complexes have also been shown to be useful in molecular film formation [1 and 2]. This study investigates the mechanical and optical properties of tannic acid and 4 arm catechol polyethylene glycol based coordinate network films. It shows that these films can contribute to energy dissipation and undergo pH-induced optical shifts when used as coatings on soft hydrogels. It also provides evidence that the molecular architecture of the network formers may have considerable effect on the properties and behavior of coordinate network films. Ultimately this work lays the foundation for further investigation of the underlying mechanisms and engineering potential of coordinate network based films. / by Rebecca Anne Gallivan. / S.B.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 165-181). / The route to enhanced functionality in electronic and magnetic devices is often through materials engineering and the use of new materials structures. Oxides, in particular, exhibit a wide range of highly tunable properties due to the interplay of lattice, orbital, charge and spin degrees of freedom. Recently, a new paradigm for epitaxy has been studied, where two oxide phases self-assembled into a vertical columnar morphology, with epitaxially strained interfaces perpendicular to the substrate. Through appropriate materials selection and strain tuning, the interfaces in these vertically aligned nanocomposites exhibit exciting properties such as high conduction at interfaces, enhanced ferroelectricity and magnetoelectric coupling, which are often absent or occur at a lower magnitude in single phase materials. In particular, magnetoelectric multiferroics, materials that exhibit two or more ferroic orders (such as ferromagnetism and ferroelectricity) and also exhibit electric field control of magnetism, have been widely explored, due to their utility in realizing novel low power multifunctional devices. Few materials exhibit robust room temperature multiferroicity, and thus vertical nanocomposites such as BiFeO₃-CoFe₂O₄ (BFO-CFO) which consist of magnetic CFO pillars in a matrix of ferroelectric BFO coupled via strain provide an exciting path to create artificial magnetoelectric multiferroics. In this thesis, we explore the magnetic, multiferroic and magnetoelectric properties of BFOCFO nanocomposites. Exploiting the rich strain tunability of BFO, we utilize different ways to modulate the structure of BFO in the BFO-CFO nanocomposites. Using different crystal substrates, we demonstrate that the presence of CFO offers additional parameters by which to tune the structure of BFO. In order to enable reliable device use, we need to understand and control the various interactions in BFO-CFO system. We demonstrate that composition tuning is an effective way to systematically tune the anisotropy of the magnetic pillars, thereby controlling their magnetostatic interactions. We probe the magnetoelectric coupling between the BFO and CFO phases by using Scanning Probe microscopy. By demonstrating tunability of the ferroelectric and magnetic phase of BFO-CFO nanocomposites and exploring the quantification of magnetoelectric coupling at the nanoscale, this thesis could enable intelligent design and optimization of the multiferroic and magnetoelectric properties in oxide nanocomposites. / by Shuchi Ojha. / Ph. D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2013. / "June 2013." Cataloged from PDF version of thesis. / Includes bibliographical references (pages 36-37). / Approximately 62.8 trillion kJ are consumed annually worldwide in the manufacturing process of traditional clay tiles. With this in mind, the goal of this project was to develop an eco-friendly alternative to clay tiles that maintain the ASTM building code standards. Through experimentation, a fly ash tile was produced that consumes 99% less energy in the manufacturing process than commercial clay tiles. The final product is a fly ash tile composed of two classes of fly ash, water, and several additives to strengthen the material. Standard ASTM tests were conducted. This fly ash tile is an energy efficient clay-tile alternative that excels in many mechanical properties. / by Jaclyn Schein. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003. / Includes bibliographical references (p. 135-139). / by Michael J. Tarkanian. / S.M.