Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (p. 187-193). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Ionic colloidal crystals are here defined as multicomponent ordered colloidal structures stabilized by attractive electrostatic interactions. These crystals are colloidal analogues to ionic materials including zincblende, rocksalt, cesium chloride, and fluorite. A thermodynamic study revealed that the screening ratio, charge ratio, and monodispersity are critical parameters in ionic colloidal crystal (ICC) formation. Experimentally, small ordered regions were observed under ideal thermodynamic conditions. However, no larger crystalline regions were found in these samples. The kinetics of ICC formation was studied using a variety of computational techniques, including Brownian dynamics, Monte Carlo, and a Newton's method solver. These techniques have each elucidated properties and processing conditions that are important to crystallization. The Brownian dynamics and Monte Carlo simulations showed that the previous experiments were highly undercooled. Furthermore, a narrow crystallization window was found, demonstrating the need to create particle systems that meet the narrow parameter space where ICCs should be stable. Pair interaction potentials were evaluated for their accuracy using a Poisson-Boltzmann (PB) equation solver. The PB solver was also used to further refine crystalline formation energies so that systems can be more accurately tailored. A surprising result from the PB solver showed that the lowest formation energy occurs when the quantity of surface charges on both particles are equal. Although this result is not predicted by any colloidal pair potentials, it was verified experimentally. This further illustrates that thermal mobility in these systems can be sufficient to maintain a stable solution despite attractive electrostatic interactions. Tailoring particle systems to balance the thermal and electrostatic interactions should allow widespread crystallization. However, these conditions require highly monodisperse particles to be fabricated with controlled surface charge and sizes. Currently these particles are not widely available and further research in this area should aid in the full realization of the ICC concept. In conclusion, all results are integrated to predict which particle systems should be produced to allow the formation of large ordered structures. / by Garry R. Maskaly. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 59). / The platinum market is a material market of increasing interest, as platinum demand has grown faster than supply in recent years. As a result, the price of platinum has increased, causing end-user firms to experience material scarcity through the presence of these high prices. A significant driver of this demand growth for the last several decades is demand automotive sector, which is responsible for almost 60% of total primary platinum demand, due to the use of platinum in three way catalysts. Platinum is one of the materials utilized to catalyze reactions that prevent vehicle emissions from entering the atmosphere, which can have a severe impact on air quality. Two factors will likely contribute to the future growth of automotive platinum demand: the trend in increased use of platinum per vehicle, and expected growth in the number of automobiles produced and sold around the world. While the automotive market is relatively saturated in developed economies, automotive sales growth potential is particularly high in developing areas, such as BRIC countries. It follows that future growth in automotive platinum demand is likely to be significant. As such, the study aims to characterize the drivers of automotive platinum demand and to establish how this demand sector impacts the platinum market as a whole. This characterization is achieved through regression analysis and by utilizing a platinum market simulation model. / (cont.) The regression results indicate that the automotive platinum demand has historically been an inelastic one. Global automotive sales have indeed been a driver of platinum demand behavior. Regression on automotive sales in India, a BRIC country has high correlation with wealth as measured by GDP per capita. In the US and Japan, automotive sales show high autocorrelation and additional correlative relationships were not confirmed. Model results show that the automotive industry drives platinum price increases when there is a combination of low elasticity of platinum demand and large growth rates in the global automotive industry. Recent news about new technologies suggests that demand elasticity may increase, and the model suggests that higher elasticity would reduce the impact of automotive industry growth on the total demand for platinum. / by Christopher George Whitfield. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1991. / Includes bibliographical references (leaves 231-235). / by David Christophe Dunand. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references. / It is well known that the use of high-brightness LEDs for illumination has the potential to substitute conventional lighting and revolutionize the lighting industry over the next 10 to 20 years. However, successful penetration of this extremely large lighting market would require vast improvements in power conversion efficiencies, color index, light output per device and drastic reduction in cost. Quantum Dot white LED (QD WLED) technology may be one of the best choices, due to its higher energy efficiency, larger color render in index, better versatility and more importantly lower cost, compared to conventional blue LED plus YAG: Ce yellow phosphor technology. Due to the fundamental difference of the material structure, QD LEDs will win a steady position among existing white LED patents and a hybrid fabless plus IP business model has the best position to promote this technology to maximize its benefits and potential for the entire LED industry. / by Xinyue Zhao. / M.Eng.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994. / Includes bibliographical references. / by Toshihiko Koseki. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1991. / Includes bibliographical references (leaves 157-168). / by James Branch Schutz. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references. / In the 21st century, mankind faces problem of energy crisis through depletion of fossil fuels as well as global warning through the production of excessive greenhouse gases. Hence, there is an urgent need to look for new sources of renewable energy or ways to utilize energy more effectively. Solid state lighting (SSL) is a major area of research interest to use energy in a more efficient manner. Early light emitting devices (LEDs) were originally limited their use for low power indication lights. Later research produces high brightness LEDs (HB-LEDs) as well as blue color LEDs. This brings to reality of the entire visible light spectrum. White light is also made possible. As with other technologies, numerous obstacles will have to be surmounted in bringing LEDs from the laboratory to the marketplace. LEDs will also have to compete with established technologies such as incandescent and fluorescent lighting. This thesis will describe the current state of high powered LEDs, examine challenges faced by LEDs and look at future markets. Evaluation in the potential of LEDs for general illumination will be carried out through cost modeling and performance analysis. / by Ken, Li Fung Yuen. / M.Eng.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. / Includes bibliographical references. / Lithium manganese oxides have attracted wide attention as low-cost, nontoxic intercalation cathode materials for rechargeable lithium batteries. In this work, the stability of these compounds during synthesis and in use has been studied in several respects. (1) Phase stability of LiMnO2 polymorphs has been determined under the high temperature synthesis conditions. Effects of temperature, oxygen partial pressure, and dopant (Al) content on the phase stability have been discussed based on a possible stability mechanism. (2) The mechanism of improved cycling stability of electrochemically transformed spinel compared to conventional spinel has been identified. Atomic rearrangement from the ordered rocksalt to spinel type cation ordering results in an antiphase nanodomain structure, which becomes a ferroelastic domain structure during the cubic ---> tetragonal Jahn-Teller transformation, and thereby accommodates the transformation strains. (3) Al-doped spinels exhibit much improved capacity stability at elevated temperatures compared to undoped spinels. This effect has been discussed with respect to proposed mechanisms of Mn dissolution and capacity loss. (4) Magnetic properties are critically influenced by phase stability, cation ordering, and Mn valence in lithium manganese oxides. In the paramagnetic temperature regime, it has been observed that antiferromagnetic interactions between the Mn ions are strongest in the orthorhombic phase among LiMnO2 polymorphs having the average Mn valence of 3+, while decreasing Mn valence strengthens the antiferromagnetic interactions in LixMn2O4 spinel. At temperatures below the paramagnetic temperature regime, spin-glass behavior is observed in both LixMn2O4 and monoclinic LiMnO2 compounds, which is attributed to geometrical frustration due to structure ( cation ordering) and magnetic disorder due to a disordered distribution of Mn valence. As spin-glass behavior is commonly observed in both well-crystallized, conventional spinel and highly disordered, transformed spinel, magnetic characterization cannot easily be used to distinguish the two different spinels. / by Young Il-Jang. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014. / 220 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 122-127). / Bismuth Telluride and its solid solutions are currently front running thermoelectric materials because of their high figure of merit. When processed via mechanical alloying to obtain nanocrystalline structures, their efficiency is increased dramatically, due to enhanced phonon scattering at grain boundaries. However, the excess free energy of these interfaces renders them inherently susceptible to grain growth, therefore there is a need for materials with enhanced thermal stability. Despite this, little is known about the relevant processing science of these materials with respect to mechanical alloying and powder consolidation. This shortcoming is addressed here via systematic study of the processing-structure relationships that govern these processing operations. Firstly, during mechanical alloying, the primary mechanism of mixing between elemental constituents is revealed, as well as the limitations to subsequent grain refinement. The resultant behaviour is unique in the literature on mechanical alloying, due to the unusual thermal and thermodynamic properties of the compound and its elements, rendering deformation-induced heating effects especially prevalent. Next, during sintering operations of the powders, the kinetics of grain growth and porosity evolution were studied. By quantifying these processes, a thermal budget map for the nanocrystalline compound is constructed, to allow predictive powder and guidance of both processing and device operation at elevated temperatures. Finally, based on the improved understanding in processing science and thermal stability of these materials, a new class of thermally stable composites is engineered, with improved thermal stability, and hence enhanced thermoelectric properties. / by Samuel A. Humphry-Baker. / Ph. D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 37-39). / Local heat delivered by magnetic nanoparticles (MNPs) selectively attached to their target proteins can be used to manipulate and break up toxic or obstructive aggregates. We applied this magnetic hyperthermia treatment to the amyloid beta (A[beta]) peptide, which unnaturally folds and self-assembles forming amyloid fibrils and insoluble plaques characteristic of amyloidgenic diseases such as Alzheimer's disease. We demonstrate remote disaggregation of A[beta] aggregates using heat dissipated by ferrite MNPs in the presence of an alternating magnetic field (AMF). Specific targeting was achieved by MNP functionalization with a targeting peptide sequence that binds a hydrophobic domain of A[beta]. AMF parameters and MNP composition and size were tailored to maximize hysteretic power losses. Transmission electron microscopy image analysis and thioflavin T fluorescence spectroscopy were used to characterize the morphology and size distribution of aggregates before and after AMF stimulus. We found that the AMF stimulus is effective at destabilizing A[beta] deposits and causing a reduction in aggregate size. This targeting scheme has potential as a therapy for amyloidosis and as a minimally invasive tool for analyzing and controlling protein aggregation. / by Colleen Loynachan. / S.B.