Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (p. 89-95). / In this thesis, biodegradable block copolyesters were specifically designed and synthesized for their susceptibility to pressure-induced mixing. These baroplastic materials are capable of being processed and molded through the application of pressure at temperatures far below those needed in traditional melt-processing of biodegradable polyesters. Pressure molding at low temperatures reduces the danger of chain degradation during processing that is ubiquitous in biodegradable plastics. The compressible regular solution model (CRS), in combination with group contribution (GC) methods and pressure-volume-temperature (PVT) data, was used to predict the phase behavior and pressure-induced miscibility of several block copolymer systems. Small-angle neutron scattering (SANS) experiments confirmed that amorphous forms of the poly([epsilon]-caprolactone-ran-5 ethylene ketal [epsilon]-caprolactone)-block-poly(lactic acid) (PmCL-b-PLA) system exhibit pressure- induced miscibility, and small angle x-ray scattering (SAXS) revealed that the position of the upper disorder-to-order temperature (UDOT) in those systems is near the values predicted by the CRS model. / (cont.) Differential scanning calorimetry measurements suggest that poly(1,5-dioxepan-2-one)-block-poly(lactic acid) (PDXO-b-PLA), which was calculated as being more miscible than PmCL-b-PLA by the CRS model, resides in a mixed state at ambient pressure and temperature. The CRS predictions were found to be more accurate with component parameters derived directly from GC than from PVT data. Pressure processing of multiple systems at low temperatures was conducted, and the mechanical properties of these biodegradable baroplastics (bbps) were measured. Crystallinity plays a complex role in baroplastic behavior that has not been fully elucidated. The strain-to-break and modulus of the bbps is good, but somewhat reduced relative to solvent-cast or melt-processed samples. The tunability of the properties of bbps, combined with their low-temperature processability, make them promising candidates for biomedical materials and environmentally friendly plastics. / by Nathan Gary Lovell. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998. / Includes bibliographical references (leaves 74-77). / by Kevin M. Chun. / S.M.

Thesis: Ph. D., 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 (pages 199-215). / Bamboo is a unique lignocellulosic material with considerable potential in sustainable construction. Structural bamboo products are analogous to wood products, such as oriented strand board (OSB), but composed primarily of bamboo elements, as opposed to wood elements. Such products could extend the use of bamboo. The mechanical behavior of structural bamboo products in large part depends on that of bamboo tissue. In this thesis, the structure and mechanical properties of dry bamboo tissue are related. Cellular level models are developed and explored, with a focus on density. Density is a practical parameter: it corresponds to weight, and places bamboo in the broader context of cellular solids. Bamboo tissue is made up of parenchyma and vascular bundles, consisting of sclerenchyma fibers and vessels; the structure can be thought of as a fiber reinforced composite. There is a radial gradient in the volume fraction of vascular bundles as well as the fraction of quite solid sclerenchyma fibers within the vascular bundles, increasing from the inside to the outside of the culm wall. Longitudinal flexural properties (modulus of elasticity MOE and modulus of rupture MOR) and compressive strength increase with increasing sclerenchyma fiber volume fraction, indicating the mechanical importance of these fibers. The density also increases with increasing fiber volume fraction. Thus, these longitudinal mechanical properties increase with density. This suggests that in bamboo tissue density reflects the underlying sclerenchyma fiber volume fraction. For moso bamboo (Phyllostachys pubescens), the extrapolated cell wall longitudinal Young's modulus estimate from tests on small flexural specimens, 39.8 GPa, agrees well with the value of 36.6 GPa obtained from a simple cell wall model for the fibers. From mechanical tests of 3D printed models of bamboo parenchyma, an open-cell foam model seems appropriate for bamboo parenchyma. The densification of bamboo increases the longitudinal flexural properties, but natural bamboo at the same density of densified bamboo has higher properties. A multiscale model for wood OSB is adapted for bamboo OSB based on the natural tissue's structure and properties; this model gives a good description of the modulus of elasticity of bamboo OSB made with internode strands. / by Patrick G. Dixon. / Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004. / Includes bibliographical references (p. 125-132). / The advantages of directed printing make it the ideal fabrication tool for the ubiquitous electronic technologies of the future. However, direct printing techniques such as ink-jet technology, are currently limited to materials that can be processed in solution. We developed a novel micro-machined print head capable of expanding the capabilities of inkjet printing to metals and molecules that are suited for evaporative deposition. Deposition of metals is particularly desirable advantage of the proposed printer. We demonstrate arbitrary organic and metal patterns by printing, with the line width modulated by controlling the micro-machined shutter. With the challenges and solutions for ambient pressure printing are also studied. Additionally, the printer can be used for organic crystal formation, and controlled doping. In the second part of the thesis we examine charge trapping and storage in organic thin film devices. We demonstrate that by controlled doping, we can engineer charge storage in active organic electronic devices. Charge trapping in organic hetero-junction structures results in two distinct phenomena that both manifest as a memory behavior. Trapped charge can (1) increase the carrier mobility in organic structures, (2) generate current during the de-trapping process. Both processes are demonstrated in practical structures. / by Sung Hoon Kang. / S.M.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (leaves 81-87). / Research into novel vaccine methods is becoming increasingly important for the potential treatment of widespread diseases such as cancer, HIV, and malaria. Members of the Irvine laboratory have developed a hydrogel and particle-based injectable vaccine with the potential to treat such diseases. The vaccine aims to elicit a tailored immune response to a particular type of disease so as to destroy infected or cells in the body and/or develop immunological memory for future protection against the disease. The purpose of this paper is to analyze the feasibility of getting such a biomaterials-based novel vaccination method to the market. Topics such as application potential, efficacy, modes of delivery, storage, patent ability, and costs for producing the vaccine are explored. Finally, a suggested business strategy is outlined, through which value can be successfully obtained from the novel vaccine. / by Kathleen Renee Huffman. / M.Eng.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997. / Includes bibliographical references (leaves 69-74). / by Anna M. Lokka. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004. / Includes bibliographical references (leaf 30). / Packer elements are traditionally rubber seals that can operate under specified downhole conditions and provide a seal for either a short-term, retrievable, or a long-term, permanent, completion. In this case a retrievable 19.7cm (7-3/4") packer element for a high-pressure high-temperature (HPHT) environment was designed and tested. The element created a seal between the mandrel, or tubing, and the casing. At high temperature and pressure rubber needs to be contained so that it will create and maintain an energized seal. In this study only Aflas rubber was tested. Various backup systems were examined; some more traditional designs such as the carbon steel foldback ring were compared to more experimental ideas. Results of theoretical simulations were compared to actual test results in order to gain a greater understanding of element behavior. Experiments were also performed to study the process of element setting, which is difficult to observe due to the high pressures and temperatures required. In a related study alternative materials to rubber such as annealed high-conductivity oxygen-free copper were tested to determine if the properties could be applied for packer element applications. The most successful design was the foldback ring with an anti-extrusion PEEK ring under the gage ring. This design passed a liquid test at 134 MPa (19.5k psi) differential pressure and a gas test at 87.6 MPa (12.7k psi) differential pressure. New designs such as the split ring with mesh and the garter spring with mesh did not pass fixture tests but could be successful with further modifications. FEA was used as an analytical tool to create simulations of the element after a setting force is applied. The modeling was shown to correlate to the actual test results and therefore it would be a good tool to use in future studies. / by Stephanie Berger. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997. / Vita. / Includes bibliographical references (leaves 66-67). / by Anand Raghunathan. / M.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, February 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 131-144). / In this thesis we encounter the formulation of a rigorous theory of resonant Raman scattering in graphene, the calculation of the so-obtained Raman matrix element K2f,1o for the 2D Raman mode with the full inclusion of the matrix elements and a physically appealing bridge between theory and experiment by eschewing the problematic ascription of graphene with a finite thickness. Finally, we elucidate an experimental study of the Raman D and G modes of graphene and highly-defected pencil graphite over the visible range of laser radiation. Marking a departure from the usual practice for light scattering in semiconductors of including only the dynamics of the electrons and holes separately, we show via fourth-order quantum mechanical perturbation theory using a Fock state basis that for resonant Raman scattering in graphene the processes to leading order are those that involve the simultaneous action of the electrons and holes. Such processes are indeed an order of magnitude stronger than those prevalent in the literature under the double resonance [1, 2, 3] moniker. We translate our perturbation theoretic analysis into simple rules for constructing Feynman diagrams for processes to leading order and we thereby enumerate the 2D and D modes. Using expressions for the terms to leading order obtained from our theoretical treatment we proceed to evaluate the Raman matrix element [4] for the Raman 2D mode by using state-of-the-art electronic [5] and iTO phonon dispersions [6] fit to ab initio GW calculations. For the first time in the literature we include the variation of the light-matter and electron-phonon interaction matrix elements calculated via an ab initio density functional theory (DFT) calculation under the local density approximation (LDA) for the electronic wavefunctions. Our results for the peak structure, position and intensity dependence are in excellent agreement with experiments [7, 8, 9, 10]. Strikingly, our results show that depending on the combination of the input (polarizer) and output (analyzer) polarization of the laser radiation, very different regions of the phonon dispersion are accessed. This has a direct impact on the dominant electronic transitions according to the pseudo-momentum conservation condition satisfied by the scattering of an electron by a phonon ki = kf + q. Using sample substitution [11] we deconvolve the highly wavelength dependent response of the spectrometer from the Raman spectra of graphene suspended on an SiO2 - Si substrate and graphite for the D and G modes in the visible range. We derive a model that considers graphene suspended on an arbitrary stratified medium while sidestepping its problematic ascription as an object of finite thickness and calculate the absolute Raman response of graphene (and graphite) via its explicitly frequency independent Raman matrix element [K'2f10]2 vs. laser frequency. For both graphene and graphite the [K'2f10]2 per graphene layer vs. laser frequency rises rapidly for the G mode and less so for the D mode over the visible range. We find a dispersion of the D mode position with laser frequency for both graphene and graphite of 41 cm-YeV and 35 cm-YeV respectively, in good agreement with Narula and Reich 131 assuming constant matrix elements, the observed intensity follows the joint density states of the electronic bands of graphene. Finally, we show the sensitivity of our calculation to the variation in thickness of the underlying SiO2 layer for graphene. / by Rohit Narula. / Ph. D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, June 2003. / "June 2003." / Includes bibliographical references (leaf 44). / There is a surprising lack of good models for granular flow. In 2002, Bazant proposed a new stochastic kinematic model of granular drainage from a silo. The new model rests on the notion that flow in the silo is caused by the migration of extended regions of excess interstitial space upward from the orifice at the bottom. An implementation of this model with the purpose of simulating the behavior of particles in the silo was developed by the author, and several results were obtained using simulations carried out with this implementation. As regards particle streamlines, average velocity profiles, predictions of particle mixing and of particle diffusivity, it was found that qualitative and quantitative agreement with experiments was excellent, in particular for a specific version of the implementation. This version uses a self-correlated random walk to describe the motion of the excess interstitial space through the silo. The model can also be used to make predictions about many other features of the granular flow (such as granular temperature), that are not as accessible through experiment's, and for which empirical behavior is not well known. In particular, the implementation of the model developed in this work can be used to simulate three dimensional flow, whereas existing experimental techniques are limited to observing two dimensions. / R. Camilo Guáqueta. / S.B.