Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000. / Includes bibliographical references (leaves 56-57). / YBa2Cu3O7-x (YBCO) thin films were prepared on lanthanum aluminate (LAO) single crystals and buffered (5000 Y20 3, 500 Ce02) Ni-single crystal substrates by metal organic deposition (MOD) process. Glassy films were converted to epitaxial YBCO films, by heating in wet atmosphere of N2/02 mixture. A novel technique was used to determine the rate of conversion of films from glassy state to crystalline YBCO films. In this approach, the concentration of residual fluoride in the partially converted films was examined using fluoride ion selective electrode. Results obtained by this method were compared to results obtained by such methods as X-ray analysis and in-situ resistivity measurements. Analysis of data obtained by different methods showed that fluoride concentration measurement method is a fast and very accurate method. The influence of different factors on conversion rate was investigated by this approach, including high and low vapor pressure of water in the processing atmosphere, temperature and influence of substrate material on conversion. A simple model was proposed to describe the growth of crystalline YBCO film for diffusion controlled and reaction controlled growth kinetics. Results obtained by in-situ resistivity measurements were compared to results predicted by the model. The obtained data fits the model that describes interface reaction limited growth kinetics. / by Igor L. Seleznev. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997. / Includes bibliographical references (p. 87-88). / by Elicia M.A. Maine. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1988. / Includes bibliographical references. / by Jiro Kawamoto. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1997. / Includes bibliographical references. / Large gap joints are frequently encountered in the manufacturing of massive components as well as in the repairing of damaged parts. Several methods using powder interlayers to produce large clearance transient liquid phase (TLP) joints have been developed and investigated in this work. One of the methods was using a mixture of powders of the melting point depressant (MPD) and the base material, from which a great amount of MPD (>30 vol.%) usually has to be used to eliminate residual porosity. To reduce the MPD in the joint, the liquid infiltrated powder interlayer bonding (LIPB) process was developed. For a material system that has a large mutual solubility between the liquid and the solid at the bonding temperature, a protective coating on the particles of the base material was applied to avoid excessive dissolution and inhibit early diffusional solidification, which can block the infiltration paths and prevent full infiltration. Direct coating of the MPD on the particles of the base material proved highly effective in producing tough and strong joints for certain material systems. The classic liquid phase sintering (LPS) theory was adopted to explain the physical process as occurring in the powder interlayer during joining. Despite the general applicability of the theory, there are several other important factors have to be considered as well. For example, the reaction rate between the MPD and the base material can markedly affect the densification of a mixed powder interlayer. Fast growth of the intermetallic compounds as a result of reaction can significantly retard the liquid flow. For the infiltration process, kinetics of dissolution and diffusional solidification largely depend on the mutual solubility between the liquid (infiltrant) and the solid (powder interlayer). Dissolution is needed to open up closed pores in the powder interlayer. However, excessive dissolution is undesirable due to fast liquid saturation and subsequent diffusional solidification, which may prevent complete infiltration of the interlayer. A protective coating on the particles of the base material provides a way of reducing the dissolution rate, which facilitates full infiltration of the interlayer. The solubility factor is also crucial for direct coating of the MPD on the particles of the base material. Higher solubility of the base material in the MPD is preferred to maintain enough liquid for complete densification. Experiments were performed on joining the materials including titanium alloy, Ti- 6A1-4V, nickel base superalloy, Inconel 625, stainless steel, SS304, and commercially pure copper. Application of the particular joining process depends on careful choice of the MPD, the base powders as well as the geometry of the interlayers. / by Wei-Dong Zhuang. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / Includes bibliographical references. / One major efficiency limiting factor in thin film solar cells is weak absorption of long wavelength photons due to the limited optical path length imposed by the thin film thickness. This is especially severe in Si because of its indirect bandgap. This thesis invents a novel light trapping scheme, the textured photonic crystal (TPC) backside reflector, which can enhance path length by at least several hundred times the film thickness for sufficient absorption. Physical principles and design optimization of TPC are discussed in detail. Thin film Si solar cells integrated with the new back reflector are successfully fabricated and significant efficiency enhancement is demonstrated.The new back reflector combines a one-dimensional photonic crystal as a distributed Bragg reflector (DBR) and reflection grating. The DBR achieves near unity reflectivity in a wide omnidirectional bandgap completely covering the wavelengths needing light trapping, and the grating can diffract light into large oblique angles and form total internal reflection against the front surface of the cell. The unique combination of DBR and grating tightly confines light inside the cell, effectively changing the path length from the thickness of the cell to its width.The back reflector parameters and the antireflection coating are systematically optimized for thin film Si solar cells through simulation and experiments. A 2 [mu]m thick cell can achieve 54% efficiency enhancement using the optimized design.For proof of concept, the TPC back reflector is integrated with thick crystalline Si solar cells (675 [mu]m thick), which demonstrate external quantum efficiency enhancement up to 135 times in the wavelength range of 1000-1200 nm. / (cont.) To prove the theory on the intended application, top-contacted thin film Si solar cells integrated with the TPC back reflector are successfully fabricated using Si-on-insulator material through an active layer transfer technique. All cells exhibit strong absorption enhancement, similar to that predicted by simulation. The 5 [mu]m thick cells gained 19% short circuit current density improvement, despite machine problems during fabrication. The textured photonic crystal back reflector design can be applied directly to single and poly-crystalline Si solar cells, and its principle is broadly applicable to other materials systems. / by Lirong Zeng. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005. / Includes bibliographical references (leaf 29). / Vanadium oxide thin film cathodes were analyzed to determine whether smaller average grain size and/or a narrower average grain size distribution affects the capacity-rate performance in lithium-ion batteries. Vanadium oxide thin films were prepared by sputtering onto ITO-coated glass substrates and crystallized in a refined annealing process to generate diverse microstructures. Average grain size and grain size distribution were determined in SEM analysis. No significant difference was observed in capacity rate behavior with changes in microstructure. However, it is speculated that further in situ analysis may show different relative diffusion rates into grains of differing sizes is related to different microstructures. / by Robin M. Davis. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (leaves 77-83). / To novel ideas must correspond novel fabrication techniques, that enable the transfer of technologies from laboratories to the market. The success of microelectronics for example can not be separated from the success of the revolutionary manufacturing technology that has fed its expansion. The same is now true for nano- and biotechnologies that, to a large extent, have yet to find the technologies that will best answer their processing needs. The question is to find an approach that will enable the production of devices with the required resolution, complexity and versatility, together with the necessary reliability and potential for high-throughput. Supramolecular NanoStamping (SuNS), a DNA based lithography technique developed in our group, is trying to answer to this set of requirements. In this thesis, I present a new development in this lithography technique, expanding its application to a broad new range of substrates in a substrate-independent fashion. This work, which I conducted during the course of my master, proves the ability of SuNS to adapt to very diverse environments and applications. / by Sarah Thévenet. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998. / Includes bibliographical references (leaves 86-87). / by Akihiko Suwa. / S.M.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. / Includes bibliographical references (p. 106-110). / by Olivera E. Kesler. / Sc.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 37-38). / Shape memory alloys exhibit superelasticity and the shape memory effect by undergoing a diffusionless phase transformation between the austenite and martensite phases. Nickel-titanium alloys are currently the most common material used. However, due to their expensive cost, alternatives such as Cu-based alloys have been investigated. Cu-based alloys have exhibited the shape memory effect and have achieved 6-8% strain recovery. This work investigates Cu-Al-Ni- Mn shape memory alloys in the form of microwires with the potential application in smart textiles. Wire microstructure and composition, transition temperatures, and strain recovery were analyzed after the wires were subjected to varying annealing times and temperatures. These data were used to determine the ideal conditions to achieve the most shape memory and superelasticity. / by Keerti Shukla. / S.B.