A. James Clark School of Engineering

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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    EXPLORING AN ALTERNATIVE TECHNOLOGY FOR MANUFACTURING ELECTRONICS FOR EXTREME TEMPERATURES
    (2023) Patel, Mital; McCluskey, Patrick; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Within our increasingly digital world, there is a demand to integrate electronics into every industry to take advantage of applications in communication, optimization, and artificial intelligence. Relatively untapped areas for electronics implementation are the extreme environments where high temperatures (>300°C) are present. These environments are common within energy, automotive, and aerospace industry es. Current high temperature technologies limit reliable use of electronics to ~200°C. Emerging technologies, such as transient liquid phase (TLP) bonding, copper sintering, and thick films, have not yet demonstrated resilient operation above 300°C. Possessing various remarkable properties, diamond is a promising material that can be used in manufacturing electronic devices operable well above 500°C. Graphene and graphite additionally can serve as conductive material for circuitry or other electronic elements. The compatibility and versatility of these three materials demonstrate the potential for robust, all-carbon electronics for high temperature applications. Chemical vapor deposition (CVD), the predominant method of synthesizing diamond for electronics, involves very costly, long processes at extreme temperatures. A relatively underdeveloped, alternative method utilizes the pyrolysis of polymer precursors into diamond. This study aims to further explore this method using Poly(naphthalene-co-hydridocarbyne) (PNHC). The polymer synthesis, processing, and pyrolysis have been performed here, and the process parameters and outcomes at each step have been documented. Native graphite and graphene growth on diamond surfaces allows for the integration of conductive material on insulating diamond. Four known methods of diamond graphitization, assisted with the metal catalysts nickel, copper, and iron, have also been applied to support the fabrication of carbon-based electronics. Ultimately in this study, the synthesis of diamond has been unsuccessful, but multi-layer graphene has been grown on polycrystalline diamond with high sheet carrier concentration and mobility values of 1.0*1015 cm-2 and 629.1 cm2 Vs-1, respectively.
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    WATER, ION, AND GRAPHENE: AN ODYSSEY THROUGH THE MOLECULAR SIMULATIONS
    (2019) Wang, Yanbin; Das, Siddhartha; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Water is known as the most common and complicated liquid on earth. Meanwhile, graphene, defined as single/few layer graphite, is the first member in the 2-dimensional materials family and has emerged as a magic material. Interactions between water and graphene generate many interesting phenomena and applications. This thesis focuses on applying molecular dynamics (MD), a powerful computational tool, for investigating the graphene-water interactions associated with various energetic and environmental applications, ranging from the wettability modification, species adsorption, and nanofluidic transport to seawater desalination. A key component of one domain of applications involves a third component, namely salt ions. This thesis attempts that and discovers a fundamentally new way in which the behavior of ions with the air-water interfaces should be probed. In Chapter 1, we introduce the motivation and methods and the overall structure of this thesis. Chapter 2 focuses on how MD simulations connect the statistical mechanics theory with the experimental observations. Chapter 3 discusses the simulation results revealing that the spreading of a droplet on a nanopillared graphene surface is driven by a pinned contact line and bending liquid-surface dynamics. Chapter 4 probes the interactions between a water drop and a holey graphene membrane, which is prepared by removing carbon atoms in a circular shape and which can serve as catalyst carriers. Accordingly, chapter 5 studies the effects of various terminations on water-holey graphene interactions, showing that water flows faster and more thoroughly through the membrane with hydrophobic terminations, compared to that with hydrophilic terminations. In chapter 6, simulations describe the generation of enhanced water-graphene surface area during the water-holey-graphene interactions in presence of an applied time-varying force on the water drop. In chapter 7, we focus on the ion-water interaction at the water-air interface to fully understand the fluidic dynamics during any seawater desalination. Our research revisits the energetic change while ion approaches water-air interface and shows that the presence of ion at the interface enhances capillary-wave fluctuation. Finally, in chapter 8 we summarize the main findings of the thesis and provide the scope of future research.
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    Ultrafast nano-oscillators based on interlayerbridged carbon nanoscrolls
    (2011-07-25) Zhang, Zhao; Li, Teng
    We demonstrate a viable approach to fabricating ultrafast axial nano-oscillators based on carbon nanoscrolls (CNSs) using molecular dynamics simulations. Initiated by a single-walled carbon nanotube (CNT), a monolayer graphene can continuously scroll into a CNS with the CNT housed inside. The CNT inside the CNS can oscillate along axial direction at a natural frequency of tens of gigahertz. We demonstrate an effective strategy to reduce the dissipation of the CNS-based nano-oscillator by covalently bridging the carbon layers in the CNS. We further demonstrate that such a CNS-based nano-oscillator can be excited and driven by an external AC electric field, and oscillate at more than 100 GHz. The CNS-based nano-oscillators not only offer a feasible pathway toward ultrafast nano-devices but also hold promise to enable nanoscale energy transduction, harnessing, and storage (e.g., from electric to mechanical).