Browsing by Author "Khatiwada, Suman"

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    Electrodes with three dimensional current collectors and methods of making the same
    (2017-02-14) Galande, Charudatta; Singh, Neelam; Khatiwada, Suman; Ajayan, Pulickel M.; Rice University; United States Patent and Trademark Office
    In some embodiments, the present disclosure pertains to methods of forming electrodes on a surface. In some embodiments, the formed electrodes have a three-dimensional current collector layer. In some embodiments, the present disclosure pertains to the formed electrodes. In some embodiments, the present disclosure pertains to energy storage devices that contain the formed electrodes.
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    Hypervelocity impact studies of carbon nanotubes and fiber-reinforced polymer nanocomposites
    (2014-04-24) Khatiwada, Suman; Barrera, Enrique V.; Ajayan, Pulickel M; Padgett, Jamie E
    This dissertation studies the hypervelocity impact characteristics of carbon nanotubes (CNTs), and investigates the use of CNTs as reinforcements in ultra-high molecular weight polyethylene (UHMWPE) fiber composites for hypervelocity impact shielding applications. The first part of this dissertation is aimed at developing an understanding of the hypervelocity impact response of CNTs – at the nanotube level. Impact experiments are designed with CNTs as projectiles to impact and crater aluminum plates. The results show that carbon nanotubes are resistant to the high-energy shock pressures and the ultra-high strain loading during hypervelocity impacts. Under our experimental conditions, single-walled carbon nanotubes survive impacts up to 4.07 km/s, but transform to graphitic ribbons and nanodiamonds at higher impact velocities. The nanodiamonds are metastable and transform to onion-like nanocarbon over time. Double-walled carbon nanotubes retain their form and structure even at impacts over 7 km/s. Higher hypervelocity impact resistance of DWCNTs could be attributed to the absorption of additional energy due to relative motion between the layers in the transverse direction of these coaxial nanotubes. The second part of this dissertation researches the effect of reinforcement of carbon nanotubes and their buckypapers on the hypervelocity impact shielding properties of UHMWPE-fiber composites arranged in a Whipple Shield configuration (a shield design used for the protection of the international space station from hypervelocity impacts by orbital debris). Composite laminates were prepared via compression molding and nanotube buckypapers via vacuum filtration. Dispersed nanotubes were introduced to the composite laminates via direct spraying onto the fabric prior to composite processing. The experimental results show that nanotubes dispersed in polymer matrix do not affect the hypervelocity impact resistance of the composite system. Nanotube buckypapers, however, improve the impact resistance of the composite, owing to the collective dampening of the shock wave amplitudes by the interconnected nanotube network in a buckypaper. The location of the buckypaper inside the composite, its thickness, and its surface modification with metals, all affect its hypervelocity impact shielding properties. Buckypaper coated with nickel and placed on the top surface of the UHMWPE-fiber composite provides the best impact resistance. Physical properties such as high bulk speed of sound in the nanotubes, and a combination of high density and high bulk speed of sound in nickel make the nickel-coated buckypaper a good hypervelocity impact shielding material. In addition, an explorative study on the use of nanograin metals for hypervelocity impact shielding was conducted.
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    Methods of preventing corrosion of surfaces by application of energy storage-conversion devices
    (2017-05-02) Galande, Charudatta; Singh, Neelam; Khatiwada, Suman; Ajayan, Pulickel M.; Rice University; United States Patent and Trademark Office
    The present disclosure pertains to methods of protecting a surface (e.g., a metal surface) from corrosion by conformably attaching a hybrid device comprising at least one multilayer energy storage device and at least one energy conversion device. In some embodiments, the multilayer energy storage device is formed by the following steps: (1) applying a non-solid negative electrode current collector composition above the surface to form an negative electrode current collector layer above the surface; (2) applying a non-solid negative electrode composition above the negative electrode current collector layer to form an negative electrode layer above the negative electrode current collector layer; (3) applying a non-solid electrically insulating composition above the negative electrode layer to form an electrically insulating layer above the negative electrode layer; (4) applying a non-solid positive electrode composition above the electrically insulating layer to form a positive electrode layer above the electrically insulating layer; and (5) applying a non-solid positive electrode current collector composition above the positive electrode layer to form a positive electrode current collector layer above the positive electrode layer.