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‣ Thermodynamics and kinetics of ceramic/metal interfacial interactions

Arróyave, Raymundo, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 248 p.; 2606346 bytes; 5680171 bytes; application/pdf; application/pdf
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Ceramic/metal interfaces occur in a great number of important applications, such as ceramic/metal composites, microelectronics packaging, ceramic/metal seals, and so forth. Understanding the formation and evolution of such interfaces is therefore essential for the better design and optimization of these technologies. In this thesis, a methodology for the study of the thermochemical interactions at ceramic/metal interfaces, during both their formation and evolution, is proposed. Because of the importance of zirconia-based ceramics in increasingly important applications such as structural composites, thermal barrier coatings and Solid Oxide Fuel Cells, it was decided to illustrate the concepts developed in this thesis through the study of the interactions between zirconias and active metals. Semi-empirical thermodynamic models of all the phases likely to take part in the ceramic/metal interfacial interactions studied were developed. Phase diagram data and thermochemical information were critically assessed and use to adjust the thermodynamic parameters that allowed the description of the Ag-Cu-Ti, Cu-Ti-Zr, Ti-Zr-O, Cu-Ti-O and Cu-Zr-O systems. The thermodynamic models were used to predict the diffusion paths across zirconia/active metal interfaces through metastable phase diagrams calculations. Additionally...

‣ Chemical vapor deposition and functionalization of fluorocarbon-organosilicon copolymer thin films

Murthy, Shashi Krishna, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 122 p.; 3183608 bytes; 3183304 bytes; application/pdf; application/pdf
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Neural prostheses are micron-scale integrated circuit devices that are under development for the treatment of brain and spinal cord injuries. A key challenge in the fabrication of these silicon- based devices is the protection of the electronic components from the ambient body environment. There is a need for a biopassivation coating on these devices that is chemically inert and electrically insulating with good adhesion to the underlying silicon substrate. Fluorocarbon-organosilicon copolymers are of interest for this application because they have the desirable attributes of both fluorocarbon and organosilicon polymers, such as low dielectric constant, thermal stability, and good adhesion to silicon. Chemical vapor deposition (CVD) is an attractive synthetic technique for this application because it is single-step, requires no solvent, and allows conformal coatings to be deposited on substrates with complex topographies and small dimensions. Fluorocarbon-organosilicon copolymers have been synthesized by hot-filament CVD, a thermal CVD technique. Control over deposition rate and chemical structure is achieved by precursor choice and variation of filament temperature. Chemical characterization by infrared (FTIR), x-ray photoelectron (XPS)...

‣ Structure and properties of three powder metallurgically processed Al-Cu-Mg alloys

Petit, Jocelyn Irene
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 113 leaves; 8432568 bytes; 8432323 bytes; application/pdf; application/pdf
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by Jocelyn Irene Petit.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1980.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.; Includes bibliographical references.

‣ The synthesis, interfacial electrochemistry, ordering, and sintering of monodisperse TiO2 powders

Barringer, Eric A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 304 leaves; 15684786 bytes; 15684544 bytes; application/pdf; application/pdf
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by Eric A. Barringer.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1983.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE; Includes bibliographical references.

‣ Heat flow and material degradation during laser metal forming

Haidemenopoulos, Gregory N
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 146 leaves; 6469560 bytes; 6469318 bytes; application/pdf; application/pdf
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by Gregory N. Haidemenopoulos.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering and Dept. of Materials Science and Engineering, 1985.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING; Bibliography: leaves 144-146.

‣ Plastics and composites in automobiles : a technoeconomic assessment of causes and effects of innovation

Poggiali, Barbara
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 133 leaves; 7063389 bytes; 7063144 bytes; application/pdf; application/pdf
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by Barbara Poggiali.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987.; Vita.; Bibliography: leaves 123-132.

‣ Design and fabrication of a light emitting diode using a two-dimensional photonic crystal; Design and fabrication of a LED using a 2D photonic crystal

Erchak, Alexei A. (Alexei Andrew), 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: [ix], 52 leaves; 4353428 bytes; 4353184 bytes; application/pdf; application/pdf
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by Alexei A. Erchak.; Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.; Includes bibliographical references (leaves 51-52).

‣ Stress and deformation of thin films and patterned lines on substrates

Park, Tae-Soon, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 115 p.; 8320187 bytes; 8319944 bytes; application/pdf; application/pdf
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The thermomechanical response of thin films/lines on thicker substrates under internal loadings resulting from material mismatch is examined. As the well-known Stoney formula is limited to isotropic, blanket films that undergo only small deformations, proper interpretation of curvature-stress relationships for new film geometries and for new experimental testing techniques requires an extension of this analytical framework. Mismatch stresses in thin films/lines and consequent curvature evolution of the film/line-substrate system are investigated in realistic, complex geometries relevant to industrial trends, such as high line aspect ratio, multi-level structure, and large diameter wafers. A combined analytical and numerical method is presented to evaluate curvature and stress evolution in metal and dielectric lines in an interconnect structure on a Si substrate during fabrication steps and subsequent thermal loading. An engineering map based on a closed-form solution for volume-averaged thermal stresses in lines is developed for material selection and design optimization. Coherent gradient sensing (CGS), an optical, full-field and vibration-insensitive experimental method, is used to study large deformation behavior of thin film-substrate systems by measuring the gradient of out-of-plane displacement of deformed surfaces. Experimental results are discussed in terms of the limitation of the small deformation theory upon which the Stoney formula is predicated. In particular...

‣ Formation and processing of rheocast microstructures

Martínez-Ayers, Raúl Andrés, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 125 leaves; 5939357 bytes; 5955125 bytes; application/pdf; application/pdf
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(cont.) given slurry was proposed. The fluidity of rheocast A357 alloy slurries was contrasted with the fluidity of superheated liquid. Rheocast slurries with 37% solid particles,were found to flow about half as far as fully liquid alloy superheated 20⁰C above the liquidus.; The importance of semi-solid metal processing derives primarily from its ability to form high integrity parts from lightweight alloys. Since the discovery of the semi-solid metal microstructure, most part production was by reheating of billets which possessed a suitable microstructure ("thixocasting"). However, it is now apparent that there are significant advantages of forming semi-solid slurry directly from liquid alloy ("rheocasting") and efficient rheocasting processes have been engineered. In this work, experimental and analytical approaches were taken to study how non-dendritic microstructures form and evolve in Al-4.5wt%Cu alloy during the earliest stages of solidification. Experimental results showed that particles in quenched rheocast alloy were already spheroidal, and free of entrapped eutectic, after 5 seconds of solidification time. Spheroidal particles were also formed by reheating equiaxed dendrites of approximately 10 [micro]m radius above the eutectic temperature for 5 seconds...

‣ The synthesis and assembly of linear-dendritic rod diblock copolymers

Santini, Catherine Marie Bambenek, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 327 p.; 20066211 bytes; 20066011 bytes; application/pdf; application/pdf
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Dendrimers are three-dimensional, hyperbranched macromolecules that possess a uniform size and shape. Most dendrimers are spherical in shape; however, the shape of the dendrimer can be adjusting using the number and the position of the branching groups in the core. For example, dendritic rods have been prepared by assembling a dendron around each repeat unit of a linear polymer core, and hybrid-linear dendritic diblock copolymers have been prepared by attaching a dendron to the end functional group of a linear polymer. This linear block in the diblock copolymers also adds physical integrity and an assembly mechanism for arrangement of the polymer. Nonetheless, no one has combined the unique shape of the dendritic rod with that of the linear dendritic diblock copolymer. The objective of this research was to prepare a linear-dendritic rod diblock copolymer, and to examine its assembly behavior in solution, at the air/water interface, and in the bulk. These polymers consisted of a linear poly(ethylene oxide)-poly(ethylene imine) diblock copolymer around which poly(amido amine) branches were divergently synthesized. The dendritic branches were terminated with amine and ester groups, as well as alkyl chains of various lengths in order to "tune" the amphiphilic nature of the polymer.; (cont.) A fundamental change in the assembly behavior of the polymers was observed at generation 4.0 (eight end-groups). In solution...

‣ Fabrication and characterization of nanostructures from self-assembled block copolymers

Cheng, Joy, 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 109 p.; 11638378 bytes; 19891122 bytes; application/pdf; application/pdf
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Nanoscale magnetic dot arrays have attracted considerable interest, both for fundamental studies of micromagnetism and for possible applications in high-density magnetic data storage. Self-assembled block copolymers provide an alternative nanolithography technique to fabricate large-area nanomagnet arrays. Block copolymer thin films that micro-phase separate into periodic domains can be used as templates to define arrays of close-packed nanostructure, using a series of etching steps. Using polystyrene-polyferrocenyldimethyl-silane (PS-PFS), large-area polymer dots, silica dots and magnetic dots with periods of 56 nm were made using a series of plasma etching steps. Magnetometry techniques are used to characterize the bulk magnetic behavior of the dot arrays of Co, NiFe and pseudo spin valve structures. These dot arrays show strong magnetostatic interaction between the dots and within the dots. The self-assembly process is simple and low cost, however, the block copolymers typically have uncontrolled defects and lack long-range order. A topographically patterned substrate is used to guide the phase-separation in a subsequently deposited block copolymer film. The lateral dimensions of the patterns in the substrates, and interfacial interactions...

‣ Fabrication and characterization of wafer-level gold thermocompression bonding

Tsau, Christine H. (Christine Hsin-Hwa), 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 140 p.; 11630327 bytes; 11630133 bytes; application/pdf; application/pdf
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Packaging is an important aspect of microelectromechanical systems (MEMS) design. As MEMS devices traverse multiple energy domains, sometimes operating in hostile conditions, the need to maintain reliability and functionality makes packaging a challenging problem. Often, the package needs to be specially designed for each device. Given the typically low volume productions, the packaging cost can often exceed the device cost. One way to lower that cost is to package at the wafer-level. This thesis explores a low temperature wafer bonding technique: thermocompression bonding. This technique relies on the applied pressure and temperature to forge a bond. The pressure brings two surfaces into close proximity while the temperature reduces the pressure requirement to deform the surface asperities. In this work, gold thin film was used to bond two silicon substrates. The thesis discusses the fabrication process, its associated challenges, and provides guidelines to achievesuccessful bonding. Characterization of the process focused mainly on the effects of bonding temperature (260 to 300° C), pressure (1.25 to 120 MPa) and time (2 to 90 min). The resultant bond was quantified using a four-point bend-delamination technique. High bond toughness was obtained and the bond quality was found to improve with increases in the bond temperature and pressure. However...

‣ Synthesis and characterization of nanocrystalline alloys in the binary Ni-Co system/

Wu, Bruce Y. C., 1980
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 100 leaves; 3862057 bytes; 3860069 bytes; application/pdf; application/pdf
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Nanocrystalline Ni-Co alloys were synthesized using pulsed electrodeposition from a Watts-type bath, and the various plating parameters were systematically varied to examine their effect on the composition, quality, and structure of the resulting deposits. Increasing the pH of the plating bath and/or the average plating current density increased the Ni content of the deposits, but both of these parameters exhibited rather narrow processing windows for the preparation of high-quality deposits. The addition of saccharin during plating was observed both to reduce the crystallographic texture of the Ni-Co alloys and to refine the grain structure. Owing to the low stacking fault energy of Co, many of the alloy deposits exhibited a large density of nanoscale twins. The unique dual-scale grain and nano-twin structure found here caused apparent discrepancies in the grain size measured by XRD and by other microscopy techniques, and also resulted in unique trends in hardness. This thesis lays the groundwork for future tailoring of nanostructured alloys to explore how twins and stacking faults influence their strength and ductility.; by Bruce Y.C. Wu.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering...

‣ Computational study and analysis of structural imperfections in 1D and 2D photonic crystals

Maskaly, Karlene Rosera
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 232 p.; 12921362 bytes; 12931189 bytes; application/pdf; application/pdf
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Dielectric reflectors that are periodic in one or two dimensions, also known as 1D and 2D photonic crystals, have been widely studied for many potential applications due to the presence of wavelength-tunable photonic bandgaps. However, the unique optical behavior of photonic crystals is based on theoretical models of perfect analogues. Little is known about the practical effects of dielectric imperfections on their technologically useful optical properties. In order to address this issue, a finite-difference time-domain (FDTD) code is employed to study the effect of three specific dielectric imperfections in 1D and 2D photonic crystals. The first imperfection investigated is dielectric interfacial roughness in quarter-wave tuned ID photonic crystals at normal incidence. This study reveals that the reflectivity of some roughened photonic crystal configurations can change up to 50% at the center of the bandgap for RMS roughness values around 20% of the characteristic periodicity of the crystal. However, this reflectivity change can be mitigated by increasing the index contrast and/or the number of bilayers in the crystal. In order to explain these results, the homogenization approximation, which is usually applied to single rough surfaces...

‣ Fabrication and control of microfluidic devices for on-chip synthesis

Hsu, Byron B.
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 19 p.; 850255 bytes; 848034 bytes; application/pdf; application/pdf
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Introduction: In biological research today, there is great demand for synthesized biological compounds. The sequencing of the Human Genome has been completed, as well as that of many other organisms. Current work is now shifting towards the production of biological macromolecules. More specifically, this includes gene and genome synthesis from user-defined sequences. A series of A, T, G, and C nucleotides are specified in advance, and then constructed. Because of the error rates in perfectly synthesizing these specific DNA chains, it is more efficient to synthesize smaller oligonudeotide chains (oligos) and then allow them to self-assemble them into a larger oligos. These assembled chains are then brought together to form even longer chains, in a repeating process known as hierarchical assembly.; by Byron Hsu.; Includes bibliographical references (p. 19).; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.

‣ Homogeneous nucleation and growth of silicon powder from laser heated gas phase reactants

Marra, Robert A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 239 [i.e. 238] leaves; 10959698 bytes; 10959511 bytes; application/pdf; application/pdf
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by Robert A. Marra.; 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.

‣ Fabrication and application of patterned magnetic media

Yao, Guhua
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 70 leaves
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In order to overcome the superparamagnetism in thin film magnetic recording media, a novel magnetic medium, called patterned medium, is studied here as a potential candidate for the future hard disk storage application. Within the patterned medium, one bit is stored in one magnetic unit, which has to be prepared "to-precision" along the track at uniform periodicity. A variety of magnetic recording media will be introduced and compared first. Detailed discussion will be focused on the potential techniques for patterned media fabrication. IP environment, market competition and business models will be given at the end.; by Guhua Yao.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.; "September 2006."; Includes bibliographical references (leaves 66-70).

‣ Process development and characterization of an oxide dispersion stabilized nickel base superalloy

Smith, Charles Hubert
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 173 leaves
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by Charles Hubert Smith.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1982.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE; Includes bibliographical references.

‣ The design, manufacturing and use of economically friendly injection molds

Buchok, Aaron (Aaron J.)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 72, [10] leaves
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Much of the polymer manufacturing done today involves the process of injection molding. It can be difficult to gain experience in the art of designing and building tooling for this process outside of industry. The goal of this project is to simplify the process involved in the design of an injection mold to a level suitable for use by motivated undergraduate engineering students. Discussion is centered on the state of the art of mold building. A great deal of attention is also paid to the use of the Battenfeld Plus 250 injection molder and the use of Solidworks MoldTools as tools for the design and use of mold tooling. By following the design, manufacturing, and use of a mold, a great deal of insight into the process and work required to produce the plastic items that we use every day is provided.; by Aaron Buchok.; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.; Includes bibliographical references (leaf 71).

‣ Presentation and accessibility of surface bound ligands on amphiphilic graft copolymer films

Kuhlman, William A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 144 p.
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Amphiphilic comb-type graft copolymers comprising a poly(methyl methacrylate) (PMMA) backbone and short, polyethylene oxide (PEO) side chains, PMMA-g-PEO, are proposed to self-organize at the polymer/water interface, resulting in quasi-2D confinement of the backbone at the immediate surface. The branched architecture and amphiphilic chemistry of these polymers results in a dense PEO brush that resists cell adhesion. To facilitate specific cell-surface interactions, small biological molecules such as adhesion peptides can be selectively tethered to PEO chain ends. Quasi-2D confinement of the polymer backbone results in clustering of tethered epitopes on a length scale dictated by the backbone. The present work investigates two aspects of this polymer architecture on organization of tethered ligands: nanometer length-scale clustering through backbone 2D confinement, and tether length effects on the availability of tethered peptides for cell adhesion.; (cont.) To directly probe 2D confined polymer conformations, combs at the film/water interface were labeled with gold nanoparticles and observed by transmission electron microscopy. A 2D radius of gyration (Rg) was calculated by reconstructing nanoparticle-decorated chain trajectories, and compared with Monte Carlo simulations of a 2D melt of similarly broad length distribution. The 2D Rg calculated from observed conformations scaled with the number of backbone segments (N) as Rg - N.69-0.02 Monte Carlo simulations yielded a scaling exponent v = 0.67 + 0.03...