Recursos de colección

DSpace at MIT (104.280 recursos)

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Materials Science and Engineering - Master's degree

Mostrando recursos 1 - 20 de 624

  1. Chemical vapor deposition (CVD) growth and optimal transfer processes for graphene

    Jo, Seong Soon
    Graphene has been regarded as a good candidate to make a breakthrough in various applications including electronics, sensors and spintronics due to its exceptional physical properties. To realize those practical applications, a high quality homogeneous wafer-scale graphene is required. Among various synthesis methods, chemical vapor deposition (CVD) has been a focus of attention as the most promising and cost-efficient deposition techniques, with advantages of its excellent repeatability and controllability, to produce large area graphene crystals on transition metal catalyst substrates. In particular, Cu with low carbon solid solubility is suitable to obtain uniform single layer deposition of graphene over large...

  2. Novel NOx sensing technology determining value by looking at patent potential and possible partnerships

    Watson, Whitney E
    Professor Michael Cima in MIT's Department of Materials Science and Engineering has developed a new approach for sensing NOx (nitric oxide and nitrogen dioxide), and Christophoros Vassiliou, a Masters of Engineering student in Electrical Engineering, is working with Cima on the development of the technology in the lab. The novelty of the electrochemical sensor is that it employs a molten alkali carbonate electrolyte as opposed to sensors with solid electrolytes, which are generally used. While the science of the sensor is still under development, Cima has targeted diesel engines for implementation. The purpose of this thesis was to assess the...

  3. Assessment of the micromorph tandem solar cell

    Wong, David Allen
    The bringing of high efficiency photovoltaics from extraterrestrial applications to terrestrial ones has begun to be realized. The micromorph tandem solar cell shows great promise as it boasts both high efficiency and low cost. The device consists of an amorphous top cell and a microcrystalline bottom cell. Optimization through high-rate silicon deposition, light trapping, and film growth make efficiencies of 15% possible. Current micromorph cells in the market are competitive in performance and cost to other similar technologies. This paper reviews the research progress and market penetration of this young but promising technology.

  4. Active hyperspectral imaging of chemicals on surfaces

    Myers, Travis R. (Travis Ray)
    Active hyperspectral imaging (HSI) is a promising technique for the detection of chemicals at standoff distances. In active HSI, a target is illuminated by a laser source at many different wavelengths and a camera obtains an image of the illuminated scene at each wavelength. In this research, the feasibility of hyperspectral imaging for the detection of particles on surfaces was demonstrated using potassium chlorate particles on car panels at distances of 5 m, 10 m, and 20 m. Using the Adaptive Cosine Estimation (ACE) algorithm which compares the observed reflectance spectra to a reference spectrum, potassium chlorate fingerprints are easily...

  5. In-situ investigation of the oxidation kinetics of Fe-12Cr-2Si using time-resolved transient grating spectroscopy

    Dennett, Cody Andrew
    The design and validation of new alloys for engineering applications is limited by the speed at which materials may be tested. In particular, there exist few methods by which the thermal, mechanical, and structural properties of materials may be monitored in conditions that are dynamically changing their microstructure. These conditions, such as heat treatments, radiation exposure, or corrosive environments, are common when material performance needs to be validated. To offset this lack of capability, new non-destructive experimental tools must be developed to facilitate on-line, realtime testing of materials undergoing some type of evolution. In this thesis, a flexible, all-optical methodology...

  6. In-situ investigation of the oxidation kinetics of Fe-12Cr-2Si using time-resolved transient grating spectroscopy

    Dennett, Cody Andrew
    The design and validation of new alloys for engineering applications is limited by the speed at which materials may be tested. In particular, there exist few methods by which the thermal, mechanical, and structural properties of materials may be monitored in conditions that are dynamically changing their microstructure. These conditions, such as heat treatments, radiation exposure, or corrosive environments, are common when material performance needs to be validated. To offset this lack of capability, new non-destructive experimental tools must be developed to facilitate on-line, realtime testing of materials undergoing some type of evolution. In this thesis, a flexible, all-optical methodology...

  7. Methodology for determining electronic transference numbers in molten sulfide melts

    Cann, Jaclyn L
    Electrolysis of molten copper (I) sulfide (Cu2S) in a sulfide-based electrolyte is being investigated for use as a direct path for copper extraction to replace the conventional process of smelting and electrorefining [1]. The allure of an electrolysis process for metals extraction can be enhanced by increasing its faradaic efficiency, through, for example, decreasing the electronic transference number of the electrolyte. This thesis compares two methods of determining the electronic transference number in Cu2S - barium sulfide (BaS) electrolytes to determine whether one or both methods are wellsuited for use with these high-temperature electrolytes. The first method is a stepped...

  8. Methodology for determining electronic transference numbers in molten sulfide melts

    Cann, Jaclyn L
    Electrolysis of molten copper (I) sulfide (Cu2S) in a sulfide-based electrolyte is being investigated for use as a direct path for copper extraction to replace the conventional process of smelting and electrorefining [1]. The allure of an electrolysis process for metals extraction can be enhanced by increasing its faradaic efficiency, through, for example, decreasing the electronic transference number of the electrolyte. This thesis compares two methods of determining the electronic transference number in Cu2S - barium sulfide (BaS) electrolytes to determine whether one or both methods are wellsuited for use with these high-temperature electrolytes. The first method is a stepped...

  9. Better multivalent battery materials through diffusion high-throughput computations

    Rong, Ziqin
    Accelerating the discovery of advanced materials is essential for human beings. However, the traditional trial-and-error way of developing materials is often very empirical and time- consuming. In 2011, the launch of Materials Genome Initiative marked a large-scale collaboration between computer scientists and materials scientists to deploy proven computational methods to predict, screen, and optimize materials at an unparalleled scale and rate. This thesis is based on this idea. Finding a suitable cathode material for Mg batteries has been one of the key challenges to the next-generation multi-valent battery technology. In this thesis, a high-throughput computation system is proposed to solve...

  10. Better multivalent battery materials through diffusion high-throughput computations

    Rong, Ziqin
    Accelerating the discovery of advanced materials is essential for human beings. However, the traditional trial-and-error way of developing materials is often very empirical and time- consuming. In 2011, the launch of Materials Genome Initiative marked a large-scale collaboration between computer scientists and materials scientists to deploy proven computational methods to predict, screen, and optimize materials at an unparalleled scale and rate. This thesis is based on this idea. Finding a suitable cathode material for Mg batteries has been one of the key challenges to the next-generation multi-valent battery technology. In this thesis, a high-throughput computation system is proposed to solve...

  11. Slurry based Three Dimensional Printing (S-3DP tm) of tungsten carbide cobalt

    Oliveira, Mark A. (Mark Anthony), 1977-
    by Mark A. Oliveira.

  12. Detection of Floating Grains in DC Aluminum Casting

    Joseph, Carolyn M
    Free-moving "floating" grains have been linked to macrosegregation in direct-chill (DC) aluminum castings. The presence of these grains in the sump of a solidifying ingot has been acknowledged based on measurements of cast microstructures and by recent work using a turbulent jet to suspend solute-poor grains and minimize macrosegregation.1,2 Experiments in this study were designed to sample grains from the mushy region of two ingots, one cast by the standard method and another stirred with a turbulent jet. Measurements of floating grain size, concentration, morphology, and chemical composition are reported. The observations from the standard ingot offer a point of...

  13. Photonic crystal enhanced LED for electroluminescence cooling

    Li, Zheng, S.M. Massachusetts Institute of Technology
    An light-emitting diode (LED) consumes low-entropy electrical power and emits incoherent photons. In this process, the lattice heat also contributes to the output power if the LED operates at voltages below the photon energy (qV < h[omega]). Therefore, an LED can potentially cool itself, and the phenomenon is referred to as electroluminescence cooling (ELC). Although researchers recently reported LEDs with net cooling in various wavelength, the cooling power was not sufficient to compensate the heat flux from the ambient and thus no temperature drop is observed. In this thesis, we design and fabricate a photonic crystal (PhC) enhanced unencapsulated LED...

  14. Analysis of wind direction fluctuations

    Friedman, Don G
    by Don G. Friedman.

  15. Adiabatic instability in the orthogonal cutting of steel.

    Lemaire, Joseph Carl
    Massachusetts Institute of Technology. Dept. of Metallurgy and Materials Science. Thesis. 1971. M.S.

  16. Numerically generating topology of the liner finish in internal combustion engines

    Wang, Renze, S.M. Massachusetts Institute of Technology
    Internal combustion (IC) engines are broadly utilized today. The friction caused by piston rings in IC engines contributes around 20% of the mechanical friction losses. The liner finish is the most critical parameter to define the tension and other design parameters of the piston rings for proper sealing. This work is focused on developing numerical approaches to generating liner finishes based on certain values of topology parameters. The generated surface is able to simulate the lubrication and dry contact behaviors of the original surface, so that the method is used to study the effects of various topology parameters on friction...

  17. Synthesis of functionalized few layer graphene via electrochemical expansion

    Jeon, Intak
    Single layer graphene is a nearly transparent two-dimensional honeycomb sp2 hybridized carbon lattice, and has received immense attention for its potential application in next-generation electronic devices, composite materials, and energy storage devices. This attention is a result of its desirable and intriguing electrical, mechanical, and chemical properties. However, mass production of high-quality, solution-processable graphene via a simple low-cost method remains a major challenge. Recently, electrochemical exfoliation of graphite has attracted attention as an easy, fast, and environmentally friendly approach to the production of high-quality graphene. This route solution phase approach complements the original micromechanical cleavage production of high quality graphite...

  18. Acid-base catalysts for polycondensation of acetaldehyde in flow

    Lusardi, Marcella R. (Marcella Rose)
    Acetaldehyde is used as a bio-oil model compound in a polycondensation reaction over two acid-base catalysts, pelletized Evonik P25 TiO₂ and an activated hydrotalcite-like compound (HTlc), to produce high molecular weight molecules in the transportation fuel range. The catalytic performance of these materials is evaluated in a gas phase, atmospheric flow system with a packed bed microreactor designed to mimic process conditions in one step of the overall bio-oil upgrading scheme. The HTlc is activated through calcination at 500 °C followed by rehydration in decarbonated H₂O, generating the active acid-base hydroxyl pairs. Materials are characterized through XRD, low temperature N₂...

  19. Electro-chemo-mechanical Studies of Perovskite-Structured Mixed Ionic-Electronic Conducting SrSni-₁₋xFexO₃₋x/₂₊[epsilon]

    Kim, Chang Sub, S.M. Massachusetts Institute of Technology
    High efficiency and fuel flexibility make solid oxide fuel cells (SOFCs) attractive. However, when operating at reduced temperatures, there is significant loss in efficiency, of which slow surface reaction kinetics at the cathode are most responsible. Previously, the mixed ionic and electronic conducting (MIEC) perovskite-structured SrSni-₁₋xFexO₃₋x/₂₊[epsilon] (STF) materials system was identified as a promising candidate for SOFC cathodes given rapid oxygen surface exchange kinetics. The exchange kinetics were correlated with the minority electron charge density in STF, which in turn depends on its defect chemistry and band structure. In this work, an alternate B site host cation, Sn, was selected...

  20. Multimaterial fiber microelectromechanical systems based on electrostrictive P(VDF-TrFE-CFE)

    Clayton, Jefferson (Jefferson Daniel)
    The miniaturization of electromechanical transducers using bulk and surface micromachining processes has enabled the deployment of microelectromechanical systems (MEMS) in a variety of applications, from cell phones and ink-jet printers to drug delivery devices. A recently developed approach for the fabrication of multimaterial fiber devices presents a unique opportunity to realize MEMS in a novel form. In this paper a thermally drawn MEMS fiber device based on P(VDF-TrFE-CFE) ferrorelaxor terpolymer is presented. Electromechanical actuation capabilities of this fiber device are established with a maximum strain of 0.78% and a maximum transverse deflection of 7[mu]m under an applied voltage of 300VDC....

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