Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001. / Includes bibliographical references (p. 151-154). / The factors dictating the minimum feature size in Slurry-based Three Dimensional Printing (S-3DPTM) of ceramics have been examined, focusing on effects related to the polymeric binder system polyacrylic acid (PAA, MW 60000) and its interaction with the ceramic powder bed. Methods for retrieving structures characteristic of the minimum feature, referred to as the "binder primitive," and for characterizing the size and shape of the binder primitive have been developed. Impact-related spreading of the printed binder droplets has been found to play little or no role on the primitive structure. Two dominant factors controlling primitive width were however identified. The first is wetting-induced spreading of the printed binder solution on the surface of the powder bed. The spreading process is halted prior to completion by infiltration of the printed liquid into the pore space. The role this factor plays thus depends on wetting properties and the relative rates of spreading and infiltration. The spreading and infiltration rates were modeled, and a means of predicting the maximum extent of spreading was developed. The second factor controlling minimum feature size is adsorption of the polymeric binder molecules from solution onto the surface of the ceramic particles during infiltration of the printed binder solution. This effectively filters the polymer from solution, resulting in a progressive decrease in concentration as the binder solution penetrates deeper into the pore space of the powder bed, which serves to limit the primitive size. / (cont.) This was confirmed via the generation of adsorption isotherms for PAA on A1203, SiO2, and TiO2 surfaces and correlating adsorption to measured primitive size in each of these systems, and by correlating the trend of primitive size with specific surface area of the powder in the high affinity A1203 - PAA system. A general model for predicting the combined effects of spreading and adsorption in the PAA-A1203 system was developed, and suggestions for future directions based on this research have been made. / by Richard K. Holman. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (p. 68-70). / The crude oil supply crisis the world is facing today along with the disastrous global warming caused primarily as a result the green house gases, has heightened the need for an eco-friendly and renewable energy technology. Solar cells, with their ability to convert the free and gigantic energy supply of the sun into electricity, are one such attractive choice. In this thesis, a study of the use of new technologies for enhanced solar cell performance based on conversion efficiency is carried out by first understanding the mechanism of selected major solar cell types, followed by an analysis of external or internal factors that affect their performance. One new technology under investigation to boost solar cell efficiency is the introduction of nanorod/wire structures into existing designs. This report discusses this approach in detail, highlighting beneficial characteristics offered and also looking into the structure realization through advanced nanostructure processing techniques. Finally, having a complete technology background at hand, various potential markets for new solar cell technologies are examined. / by Bertha Tan. / M.Eng.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 76-80). / The possible use of programmable integrated circuit interconnect vias using an indirectly heated phase change material is evaluated. Process development and materials investigations are examined. Devices capable of multiple cycles between on/off states for reconfigurable applications have been successfully demonstrated in a standard CMOS-compatible technology. Building computer chips with these vias would create a new kind of field programmable gate array (FPGA), whereby the design can be reconfigured depending on its application. The phase change reprogrammable-via is nonvolatile, unlike SRAM-based technology. It also has a relatively low on-state resistance and occupies less real estate on the chip. As the "switches" are placed at the metallization level, it provides flexibility for the designer to place them. Programmable-via can operate at a relatively low voltage compared to FLASH-based technology. Similar to the case of antifuses, programmable-via interconnect structures are projected to be radiation hard. However, the most challenging part of implementation is the circuit design. Issues such as integration of materials and design with current tools need to be overcome. A lack of expert personnel in this area also makes the implementation of programmable-via FPGAs complicated. The market for FPGA is promising due to the attraction of the programmable logic market. An intellectual Property (IP) analysis indicates there exist a significant new space for exploration in this area. The best-suited business model is as a new start-up that demonstrates feasibility and develops intellectual property. The potential commercialization of such technology is also discussed. Although this concept is promising result, more research is needed to show the reliability and feasibility of such a technology in complex circuits. It will take some time before this approach can be considered for production. / by Chee Ying Khoo. / M.Eng.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994. / Includes bibliographical references (leaves 151-153). / by Rizwan Mahmood Gul. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Vita. / Includes bibliographical references (p. 93-103). / Essential to the emergence of spin-based electronics is a source of highly polarized electron spins. Conventional ferromagnets have at best a spin polarization P-50%. Europium monoxide is a novel material capable of generating a highly spin-polarized current when used as a tunnel barrier. EuO is both a Heisenberg ferromagnet (Tc=69 K) and a semiconductor. Exchange splitting of the conduction band creates different tunnel barrier heights for spin-up and spin-down electrons, thus filtering the spins during tunneling. High-quality EuO films at the monolayer level is necessary for efficient spin-filtering. Because non-ferromagnetic, insulating Eu20 forms more readily, growth of an ultra-thin, high-quality film is quite challenging, which restricted previous studies of EuO to bulk form. EuO films were grown by reactive thermal evaporation, and various thin film characterization techniques were employed to determine the structural, optical, and magnetic properties, even on the thickness scale needed for tunneling (<3 nm). The film properties closely matched those of bulk EuO, though the Tc for ultra-thin films was found to be reduced from bulk value, in agreement with theoretical prediction. / (cont.) Controlling the smoothness and chemical nature of the inter-faces between EuO and metallic electrodes was found to be of critical importance, as proven by careful interfacial chemical and magnetic analysis at the monolayer level, using x-ray absorption spectroscopy, magnetic circular dichroism, and diffuse x-ray resonance scattering techniques. EuO was successfully prepared as the barrier in Al/2.5 nm EuO/Y tunnel junctions. By fitting the current-voltage characteristics of these junctions to tunneling theory, exchange splitting in an ultra-thin layer of EuO was quantitatively determined for the first time, and complete spin filtering yielded total spin polarization, P=100%. In an alternative approach, P was directly measured using the superconducting Al electrode as a spin detector. Spin-filtering in EuO barriers was also observed in magnetic tunnel junctions (MTJs), in which a ferromagnetic electrode was the spin detector. In Cu/EuO/Gd MTJs a tunnel magnetoresistance (TMR) of 280% was measured by changing the relative alignment of magnetization of EuO and Gd, which is the largest TMR measured using a spin-filter barrier. Co/A1203/EuO/Y junctions, in which the A1203 barrier magnetically decoupled Co and EuO, also showed substantial TMR. Its matching band gap (1.1 eV) and compatibility with Si open up the novel possibility of using EuO to inject highly polarized spins into Si-based semiconductors. / by Tiffany S. Santos. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 45-47). / A stamped nanoparticle array patterning technology integrating interference lithography, self assembly and soft lithography is assessed. This technology is capable of parallel patterning of nanoparticles at a large scale. Among several possible applications of this technology, potential for Deoxyribonucleic Acid detection is specifically investigated. Attaching DNA to nanoparticles through a probe molecule changes the local dielectric environment and hence affects surface plasmon resonance. However, the projected plasmon peak shift is not significant. Another detection method is described here to create a visible optical DNA sensor with a tolerable increase in cost relative to existing technologies. Intellectual property issues are also discussed for this technology. / by Zongbin Wang. / M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003. / Includes bibliographical references (p. 106-113). / Microphase-separating copolymers have been shown to possess the electrical properties of a polymer liquid and the mechanical properties of a solid. In the past, these materials had to be produced via anionic methods that are not easily scalable. To circumvent this problem, two approaches were adopted. In one, atom transfer radical polymerization (ATRP) was used to create the block copolymer, poly(oligo(oxyethylene) methacrylate)-b-poly(butyl methacrylate) [POEM-b-PBMA], which when doped with LiCF₃SO₃ (lithium triflate) exhibited good conductivity at room temperature ([sigma] [approximately] 3 x 10⁻⁶ S/cm at 23C̊). The other approach used free radical techniques to prepare the graft copolymer, POEM-g-PDMS, starting with commercially available high molecular weight poly(dimethyl siloxane) [PDMS] monomethacrylate-terminated macromonomer. When doped with lithium triflate this material exhibited a conductivity of [sigma] [approximately] 8 x 10⁻⁶ S/cm at 23° C.This material was found to be stable up to [approximately] 300° C and flow resistant below an applied pressure of [approximately] 60 psi. In an effort to achieve single-ion conduction by Li⁺, the anionic charge was incorporated into the polymer backbone as a carboxylate. To prevent undesirable ion-pairing interactions two approaches were adopted: (1) tethering the anionic charge outside the conducting block of a block copolymer; (2) reacting the Lewis acid BF3 with the carboxylate to delocalize the negative charge. Both approaches produced materials with T[sub]Li⁺ = 1 while retaining conductivity ([sigma] <[or equal to] 7 x 10⁻⁶ S/cm) nearly identical to that observed in salt-doped systems. The self-doped electrolytes, however, demonstrated the ability to deliver stable currents at high drain rates, suggesting that immobilizing the anion improves rate capability. 100% solid-state cells consisting of lithium anodes, thin-film, fully-dense, vanadium oxide cathodes and microphase-separating copolymer electrolytes were operated for hundreds of cycles at discharge rates as high as [approximately] 1.5 C. Such batteries are conservatively projected to possess energy densities of 173 Wh/kg or 337 Wh/L. A design exercise optimizing a multilayer, thin-film battery configuration with the materials studied in this investigation speculated that specific energies exceeding 400 Wh/kg or 700 Wh/L may be attainable. The use of inexpensive materials and scalable processes in a simple design is expected to keep the cost of production low. / by Patrick E. Trapa. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1992. / Includes bibliographical references (leaves 140-142). / by John Edward Moalli. / Sc.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / Includes bibliographical references (p. 79-85). / In an effort to improve control and design in organic crystallization, the effect of solvent on polymorph selection has gained tremendous interest in recent years. In this thesis, molecular simulation techniques are used to gain insight into the solvent effect on glycine crystallization in water-methanol mixtures. We report the validation of the Optimized Potential for Liquid Simulations (OPLS) force field and parameters with modified Lennard-Jones parameters for hydrogens attached to a-carbon in glycine zwitterion. Solution and interface simulations in water and 50% v/v water-methanol solutions reveal the mechanism through which methanol additive results in the crystallization of the least stable [Beta]-glycine polymorph. Free energy calculations through the Umbrella Sampling method show an increased stability of the centrosymmetric dimer structure ([alpha]-glycine growth unit) in the presence of the methanol additive. Even though the dimer structure is more stable in water-methanol mixtures, a higher fraction of glycine monomers were observed in water-methanol mixtures. It is revealed through thermodynamic arguments that a drastic decrease in solubility results in a higher fraction of glycine monomers in water-methanol mixtures. It was hypothesized in previous studies that the presence of monomer units docking onto the (010) interface of [alpha]-glycine inhibits further growth due to exposed ammonium groups at the interface. The effect of solvent on crystal growth inhibition is explored by the interface simulations of a-glycine in water-methanol mixtures. When the monomer units are docked onto the interface, water is shown to be more effective than methanol in inhibiting crystal growth of (010) interface of [alpha]-glycine. This study sheds light on the role played by the solvent on glycine polymorph selection in water-methanol solutions. / by Srihanth Patala. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 51-52). / Carbon Black-doped Polydimethylsiloxane (CB-PDMS) can be used as a pressure sensing material due to its piezoresistive properties. The sensitivity of such a sensor is in part dependent on the stiffness of the material. A closed-cell CB-PDMS foam is being explored as a possible flexible, lightweight, and waterproof underwater sensing material for use in unmanned underwater vehicles and other hydrodynamic sensing purposes. The percolation threshold for conduction through the CB-PDMS foam is theorized, and a number of different concentrations based on the theorized threshold are explored in order to determine the optimum weight percent of Carbon Black dopant to achieve a high sensitivity, low stiffness sensing CB-PDMS foam. Sinusoidal mechanical pressure patterns were applied and voltage response measured. An optimum dopant weight percent out of the concentrations tested was found at 5.5 wt% CB-PDMS. / by Jessica A. Herring. / S.B.