Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987. / Bibliography: leaves 151-155. / by Walter Wilhelm Focke. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (p. 103-106). / This thesis presents fabrication process improvements for a RF MEMS resonator for the purpose of improving the quality factor (Q) and extending the frequency range. The process changes include the use of conformable contact lithography (CCL) and chlorine-based dry etching for improved fine-feature patterning and Moiré -based alignment techniques to allow for a non-self-aligned process. The resulting control over feature size and structure are expected to improve Q and enable higher frequency resonators. A CCL process utilizing moir6 alignment marks is described. An automated Moiré -based alignment system using Labview software is presented which demonstrates sub-100 nm alignment accuracy for a single alignment mark. A full-wafer alignment experiment is described that demonstrates average pattern placement errors of ... for the x- and y-directions respectively. The experimental limitations are analyzed and suggested improvements to the system are detailed. Chlorine dry etching experiments are conducted in order to produce a straight sidewall etch through the "stack" of resonator materials (chrome, aluminum nitride, and molybdenum). A combination of Cl₂/0₂, Cl₂/Ar, and CF₄0₂ plasmas at low pressure (2 mTorr), high microwave/source power (500W), and a moderate DC bias (-150V) demonstrates a straight sidewall angle (>80⁰ measured from horizontal) with no undercut for all layers of the stack. RF resonators fabricated with these process modifications are presented. An average overlay error of 55 nm (110 nm min-max) is recorded for 11 devices located closest to the line between the alignment marks in an aligned release of the resonators. The design modifications enabled by the new process are described and the prospect for higher-frequency devices and higher-Q device performance is discussed. / by Mark Sakai. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (leaves 25-26). / Advances in nanochemistry will drive the development of technologies at the scale of 1 - 100 nm. Principles of biology are used for the self-assembly of structures and devices at this scale. The Ml 13 bacteriophage, a virus employed in phage-display libraries, serves as a scaffold for nanoscale structures. Phage are functionalized with inorganic materials, and controlled placement of phage at the nanoscale may lead to useful devices. Substrates patterned with dip-pen nanolithography (DPN) serve as templates for the deposition of phage. On gold substrates, 16-mercaptohexadecanoic acid (MHA) is deposited to form patterned lines. After surface passivation and activation chemistry, phage are deposited and adhere to the patterned substrate. Images from atomic force microscopy support that phage are covalently coupled to MHA lines and that cobalt precipitates on patterned phage. / by David S. Gray. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 33-35). / The electronics manufacturing industry has been experiencing a fast-changing landscape with recent legislations targeting the supply chains for the 3TG minerals: tin, tantalum, tungsten, and gold mined from the Democratic Republic of Congo. These minerals exhibit unique properties that are crucial to their role in the manufacturing process and functionality of many electronic products such as computers, cell phones, and printers. This work focuses on using a bottom up model to quantify conflict mineral content within LaserJet printers and uses a market analysis to compare the conflict mineral composition between various IT products in order to obtain a measurement of impact the conflict minerals have in their respective IT product. On the global scale, the model estimates the market share of tin, tungsten, tantalum, and gold in printers to be 1.44%, 0.083%, 0.017%, and 16.5%, respectively. These results indicate a strong potential and improvement for the development of redefined materials selection processes for manufacturers of IT products in using alternative solutions or substitute materials. Current work in this field shows that it is imperative for future work to focus on decreasing the market share of these conflict minerals and shifting manufacturing focus to developing new conflict-free electronic products. / by Jason S. Lee. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2001. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 41). / A method was devised for quenching undercooled samples of Fe-12Cr-16Ni. The samples were levitated in a magnetic field as a way of containerless processing. They were dropped onto a nucleation trigger and then into a quenching bath. This process was successful in producing quenched samples , but the layer of In-Ga wetting their surface showed problematic in the analysis of the samples. Data shows that double recalescence was observed in a few cases. SEM proved inconclusive and was not sensitive enough to detect the small chemical variations expected in the dendrites. Also, across the entirety of the sample there was no significant partitioning of Cr or Ni. / by Nicole Zacharia. / 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. / The short-wave infrared region (SWIR; 1000-2000 nm) has excellent properties for in vivo imaging: low autofluorescence, reduced scattering, and little light absorption by blood and tissue. However, broad adoption of SWIR imaging in biomedical research is hampered by the availability of versatile and bright contrast materials. Quantum dots (QDs) are bright, compact SWIR emitters with narrow size distributions and emission spectra, qualities that make them ideal for labeling and multiplex SWIR imaging. Nevertheless, SWIR QDs have limited applications due to the shortcomings of established ligand systems. Established ligands result in QD probes with limited colloidal stability, large size and broad size distribution, or all three limitations. To address these limitations, we turned to polymeric ligands, beginning with the polymeric imidazole ligand (PIL) initially developed for visible-emitting CdSe/CdxZn₁₋xS QDs with L-type native ligands. We studied ligand exchange with PIL and InAs/CdSe/CdS SWIR QDs with native X-type ligands in a variety of conditions but only saw limited exchange. Our results combined with reports in the literature suggest that the mechanism of X-to-L ligand exchange is not amenable to polymeric ligands. These results led us to the concept of ligand-type matching: for straightforward exchange, QD native ligands should be the same type as the binding groups on the polymer. Thus, we synthesized InAs/CdSe/ZnS with L-type native ligands, which exchanged readily with PIL to produce probes with (<14 nm hydrodynamic diameter, Hd). We also synthesized a new ligand that is compatible with oleate-capped QDs: the polymeric acid ligand (PAL), which features carboxylic acids as the binding group and PEG₁₁ chains to solubilize the QD-ligand construct. We exchanged PAL with oleate-capped PbS and PbS/CdS QDs, resulting in compact probes ( <11 nm Hd) with narrow size distribution. The small size and narrow size distribution of these constructs are preserved for several months when stored in isotonic saline solution in air, addressing the size and stability limitations of existing ligand systems for SWIR QDs. Our constructs are bright in vivo and to demonstrate their suitability for imaging, we performed whole-body imaging as well as lymphatic imaging, including visualization of lymphatic flow. / by Daniel Mauricio Montana Fernandez. / Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. / Includes bibliographical references (leaves 92-93). / by Gaël Gioux. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1989. / Includes bibliographical references (leaves 152-155). / by Scot Anthony Arnold. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1983. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Vita. / Includes bibliographical references. / by Ronald Joseph O'Malley. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 151-160). / As consumption in the US grows, so does concern about sustainable materials usage. Increasing recycling is a key component within a broad arsenal of strategies for moving towards sustainable materials usage. There are many barriers to increasing recycling; one that is problematic is compositional uncertainty in the scrap stream. Repeated recycling compounds this problem through the accumulation of tramp elements in the material stream over time. Pertaining to the available operational and technological strategies that exist to mitigate accumulation, this thesis addresses the following questions: 1) How effective are these strategies at mitigating accumulation? 2) Under what conditions do upgrading technologies provide a cost efficient and environmentally effective improvement to the composition of recycled scrap streams? To answer these, a method was developed combining dynamic material flow analysis with optimal allocation of those materials into production portfolios using blending models. This methodology thus captured 1) the flow of EOL scraps, 2) how the economics of production are affected by changes in technology, and 3) a characterization of how recycling parameters influence accumulation in recycled streams. Using this methodology, optimal allocation was found to be an effective strategy for mitigating accumulation, for example, iron in the scrap stream was 69% less when compared to the value projected by conventional statistical methods. Two upgrading technology cases were examined using the time-dependent methodology developed: shredding, sorting, and dismantling of aerospace scraps and fractional crystallization. / (cont.) Case results indicate that the time-dependent value of these technologies relies on whether or not the scrap stream is compositionally or availability constrained. These values were compared to analysis that does not consider repeated recycling (time-independent). Results show that undervaluing will occur in a regime where scrap availability is constrained and there is significant compositional accumulation occurring, a regime that may very well represent the reality faced by aluminum secondary producers in the US. / by Gabrielle G. Gaustad. / Ph.D.