Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 34-35). / Previous studies of nanoporous gold have found that, during the coarsening process, the genus per characteristic volume of nanoporous gold has remained constant. Using a rolling-ball type algorithm, in which a test probe rolls over the surface to identify atoms, several test structures and a small-scale nanoporous structure were meshed. The genus was then calculated for each of these meshed structures. It was found that an algorithm that accounts for periodic boundary conditions is required for an accurate genus calculation. / by Ryan Rosario. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 31-32). / Nanogap devices have applications in single molecule sensing and single molecule transistors. Nanogap devices comprised of a gold nanowire with a nanoscale gap containing C₆₀ were fabricated using electromigration on a silicon substrate. Raman spectra were obtained for various features of this device in order to detect the presence of C6o and study its electronic properties. The 532 nm laser source showed Raman peaks at 300,522,930-980, 1570, 1900 and 2150 cm-¹ and the 632 nm laser source showed Raman peaks at 300, 522, 930-980, 1460, and 2124 cm-¹. The device feature (gold, C₆₀, silicon or combination thereof) responsible these peaks' presence in Raman spectra was determined. There was peak broadening present at long wavelengths for gold features in the Raman spectra taken using the 532 nm laser and for spectra using the 632 nm laser when C₆₀ is present in high concentrations. This is believed to be an effect of the creation of defects in the C60 lattice due to the presence of oxygen, resulting in Frenkel excitons becoming trapped. When the Frenkel excitons recombine, they emit light causing the photoluminescence at longer wavelengths. Peak broadening was also studied in devices comprised of a gold nanoparticle substrate with C60 spun cast onto the surface. Raman spectra of nanoparticle and nanogap devices shared similar features. / by Erin Perry. / S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 35-36). / As materials consumption increases globally, minimizing the end-of-life impact of solid waste has become a critical challenge. Cost-effective methods of quantifying and tracking municipal solid waste contents and disposal processes are necessary to drive and track increases in material recovery and recycling. This work presents an algorithm for estimating the average quantity and composition of municipal waste produced by individual locations. Mass fraction confidence intervals for different types of waste were calculated from data collected by sorting and weighing waste samples from municipal sites. This algorithm recognizes the compositional nature of mass fraction waste data. The algorithm developed in this work also evaluated the value of additional waste samples in refining mass fraction confidence intervals. Additionally, a greenhouse gas emissions model compared carbon dioxide emissions for different disposal methods of waste, in particular landfilling and recycling, based on the waste stream. This allowed for identification of recycling opportunities based on carbon dioxide emission savings from offsetting the need for primary materials extraction. Casework was conduced with this methodology using site-specific waste audit data from industry. The waste streams and carbon dioxide emissions of three categories of municipal waste producers, retail, commercial, and industrial, were compared. Paper and plastic products, whose mass fraction averages ranged from 40% to 52% and 26% to 29%, respectively, dominated the waste streams of these three industries. Average carbon dioxide emissions in each of these three industries ranged from 2.18 kg of CO₂ to 2.5 kg of CO₂ per kilogram of waste thrown away. On average, Americans throw away about 2 kilograms per person per day of solid waste. / by Jasper Z. Lienhard. / S.B.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016. / 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 93-98). / Electrochemical energy storage and conversion devices are important for the application of sustainable clean energies in the next decades. However, the slow kinetics of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) lead to great energy loss in many electrochemical energy devices, including polymer electrolyte membrane fuel cells (PEMFCs), water splitting electrolyzers, and rechargeable metal-air batteries, which hampers the development of new-energy applications such as electric vehicles. To increase the energy efficiency of ORR and OER processes, various catalysts have been studied for oxygen electrocatalysis, but they are still not active enough or not stable enough in developing commercial friendly electrochemical devices. In this work, systematic studies have been applied on two catalyst systems: Pt-metal (Pt-M) alloys for ORR and perovskite oxides for OER. The combination of electrochemical characterizations with transmission electron microscopy (TEM) techniques provides deeper insights on how the basic physical and chemical properties could influence the stability and activity of the catalysts. For Pt-M ORR catalysts, it is found that using transition metal with more positive dissolution potential or forming protective Pt-rich shell by mild acid treatment can improve their stability in acid electrolyte. While for perovskite oxide OER catalysts, it is found that a closer distance between O 2p-band and Fermi level leads to higher activity but lower stability at pH 7, due to the activation of lattice oxygen sites. Moreover, with the help of environmental TEM techniques, structural oscillations are observed on perovskite oxides in the presence of water and electron radiation, caused by the oxygen evolution after water uptake into the oxide lattice. Such structural oscillation is greatly suppressed if the formation and mobility of lattice oxygen vacancy is hampered. The various new activity and stability descriptors for oxygen electrocatalysis found in this work not only provided practical guidelines for designing new ORR or OER catalysts, but also improved our fundamental understandings of the interactions between catalysts and electrolyte. / by Binghong Han. / Ph. D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (leaves 58-59). / Consumer demand is hard to predict in any industry, let alone the automotive industry. Vehicle manufacturers try to produce according to what their customers want, but if these wants change, the company is faced with lots of unsold cars and a huge changeover cost. In order to help fight the problems of demand variability, automotive manufacturers have begun the move towards plant flexibility. This includes designing vehicles comprised of similar subassemblies and the development of flexible tooling. The hope is that multiple vehicles can be produced on the same line so if demand starts to fluctuate, they can change the production levels of their styles with minimal lead time. There are a number of different approaches to flexible tooling. One approach using programmable robotic repositionable tools (PRRT) is particularly promising because it can handle a large number of styles and requires low style specific reinvestment costs. This thesis examines the PRRT technology as well as other forms of flexible tooling to understand the conditions under which these approaches make the most economic sense. / (cont.) For this project an algorithm was developed to choose assembly tools based on subassembly characteristics, production levels, style counts, and flexibility approaches. The algorithm was connected to an already existing vehicle assembly model and two forms of economic analysis were performed. The first looked at the costs of using PRRT versus other forms of tooling for various product mixes. The second analyzed the potential cost savings when considering product changeover. The results indicated that the initial outlays for PRRTs cannot be justified even for a large number of styles unless multi-generational product changeover is also considered. However, PRRTs provide a cost effective flexible tooling option for plants producing multiple styles when considering product changeovers. / by Jeffrey C. Povelaites. / M.Eng.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 112-115). / Optical technologies are now ubiquitous in data communication, telecommunication, and computing networks for transmission distances beyond a few meters. The use of optical to transmit voice communication has changed the nature of the industry and been driving photonic component innovation for the past 30 years. Never before has the world demanded more data to run its collective everyday lives. Technological lifecycles have shortened and to keep pace with the rapidly increasing quantities and demands of data needs, firms are placing a stronger emphasis on the development of new technologies to replace old ones. The use of electrical interconnects has been the workhorse for data transmission for over a century and a new technology is poised to succeed it. Due to the limitation of current transmission medium, an adoption of new technology is inevitable and the question is when and what are the drivers? In this thesis, an analysis will be conducted to examine the adoption of optical interconnect cables in different lengths using different costs of new technology. These results will be used to understand how each driver affects the overall adoption of optical interconnect cables, the limitation of adoption, and a potential timeline of adoption for each length examined. / by Louisa Chiao. / M.Eng.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Ashok Murthy. / Sc.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017. / Cataloged from PDF version of thesis. Pages 160 and 161 are blank. / Includes bibliographical references. / The conformations of conjugated polymers can be altered by nearby environments. The intrapolymer conformation and interpolymer assemblies have a crucial impact on a variety of properties such as absorption, energy migration, and fluorescence. In this dissertation, the conformational changes and their effects on photophysics in different environments will be discussed. In Chapter 1, the basic principles to understand this thesis will be reviewed, including the processes of absorption and emission, exciton migration, the Langmuir-Blodgett technique, and interfacial phenomena. In Chapter 2, the conformational control and alignment of conjugated polymers at the air-water interface and how this alignment of polymers can lead to new emissive aggregates will be presented. The emission has the characteristics of excimers with the improved fluorescence quantum yields. The transfer of the aligned aggregates to glass substrates is attempted and these excimer films undergo reorganization upon exposure to solvent vapors, which triggers the fluorescence color change from yellow to cyan, leading to fluorescence-based chemical sensors. In Chapter 3, exciton migration to low-energy emissive traps at amphiphilic interfaces will be discussed. This chapter will deliver the design of interfaces and how the exciton migration can occur at the air-water interface and the hydrocarbon-water interface in lyotropic liquid crystals. To expand this interfacial exciton migration to more generalizable interfaces, Chapter 4 will show the fabrication of oil-in-water emulsions and how exciton migration in oil-in-water emulsion can produce distinct fluorescences between solution and interfaces. Chapter 5 will discuss the structural variations of novel functional conjugated polymers and how substituents can change the conformation of the polymer backbones. Additionally, how this conformational change affects the electronic and optical properties of polymers will be examined. / by Byungjin Koo. / Ph. D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006. / Includes bibliographical references (p. 71-74). / A business model was created in order to explore the commercial application of a bi-layer bone-ligament scaffold to the treatment of torn anterior cruciate ligaments (ACL) requiring replacement. The two main keys in producing the bone scaffold are triple co-precipitation of type-I collagen, chodroitin-6-sulphate, and calcium phosphate minerals and the use of lyophilization to create a network where all the materials are homogeneously dispersed and present in significant amounts. This process allows the creation of a porous network whose physical characteristics, mechanical properties, and material content can all be changed to create a scaffold that closely mimics natural bone. A collagen and chondroitin-6-sulphate scaffold is used for ligament regeneration. The ACL replacement market was chosen because it is one of the most commonly surgically repaired ligaments in the body and because all of the current treatments have drawbacks. / (cont.) The exercise of creating a business model made it clear that the commercial potential of starting a company that focused on marketing a direct ACL replacement scaffold would most likely not be successful mainly because surgeons would hesitate to use this product over current methods that are satisfactory and it would be difficult to separate our product from other newer methods which all boast similar advantages over current treatment options. However, the commercial potential of using the technology to create a scaffold for graft site morbidity in certain ACL replacement surgeries is large because there is no competition, and the implantation procedure for the surgeon would be simple. / by Jessica C. Li. / M.Eng.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (p. 49). / This paper explores a possible design for a CMOS compatible, athermal, optical waveguide. The design explored is a slot waveguide with light guided in the low index material. A design paradigm is proposed which shows the relationship between cross-sectional parameters and their impact on both the effective index of refraction and the thermo-optic coefficient of the device. Two materials choices were explored to serve as the low index material, poly(ether imide) (PI) and poly(methyl methacrylate) (PMMA). The slot waveguide with PI as the low index material had a simulated, device thermo-optic coefficient of -8.5 x 10-4K-1, and the slot waveguide with PMMA as the low index material had a simulated, device thermo-optic coefficient of 1.7 x 10-5K-1. / by Luis Enrique Fernandez. / S.B.