Browsing by Subject "graphene"
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Item Additive Manufacturing of Carbon Fiber and Graphene – Polymer Composites using the technique of Fused Deposition Modelling(University of Texas at Austin, 2016) Girdis, Jordan; McCaffrey, Matthew; Proust, GwénaëlleAdding micro or nano-carbon reinforcements to polymers enhances their mechanical and electrical properties. In this paper, the effects of the addition of short carbon fibres (SCF) and graphene into acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) polymer to create composite filaments for fused deposition modelling (FDM) are investigated. After creating carbon polymer composite filaments, using a commercial 3D printer, samples were printed and tested for mechanical and electrical properties. The measured values for these composites were compared to those obtained for pure ABS and pure PLA. It was found that by using only 2% SCF it was possible to achieve a 22% increase in tensile strength with no significant impact on printability. With addition of graphene, PLA was made to be conductive. These results show the feasibility of developing new materials for 3D printing that will create structurally sound and conductive designs.Item Density functional study of graphene on insulating substrates(2009-08) Jadaun, Priyamvada; Banerjee, Sanjay; Sahu, Bhagawan R.; Fiete, GregoryThis is a study of the structural and electronic behavior and properties of graphene on α-quartz and α-sapphire using Density Functional Theory. We construct initial structures using the above 2 substrates, place a layer of graphene on them and subsequently allow the atoms to relax. After relaxation we study any structural changes, band structures, density of states, charge density to determine the electronic properties of the entire structure. Eventually this study will help in the search for good substrates for graphene based transistors.Item Metaplastic and energy-efficient biocompatible graphene artificial synaptic transistors for enhanced accuracy neuromorphic computing(Springer Nature Limited, 2022-07-28) Kireev, Dmitry; Liu, Samuel; Jin, Harrison; Xiao, T. Patrick; Bennett, Christopher H.; Akinwande, Deji; Incorvia, Jean Anne C.CMOS-based computing systems that employ the von Neumann architecture are relatively limited when it comes to parallel data storage and processing. In contrast, the human brain is a living computational signal processing unit that operates with extreme parallelism and energy efficiency. Although numerous neuromorphic electronic devices have emerged in the last decade, most of them are rigid or contain materials that are toxic to biological systems. In this work, we report on biocompatible bilayer graphene-based artificial synaptic transistors (BLAST) capable of mimicking synaptic behavior. The BLAST devices leverage a dry ion-selective membrane, enabling long-term potentia- tion, with ~50 aJ/µm 2 switching energy efficiency, at least an order of magni- tude lower than previous reports on two-dimensional material-based artificial synapses. The devices show unique metaplasticity, a useful feature for gen- eralizable deep neural networks, and we demonstrate that metaplastic BLASTs outperform ideal linear synapses in classic image classification tasks. With switching energy well below the 1 fJ energy estimated per biological synapse, the proposed devices are powerful candidates for bio-interfaced online learning, bridging the gap between artificial and biological neural networks.Item MnNiCoO4/N-MWCNT Nanocomposite Catalyst with High Selectivity in Membraneless Direct Formate Fuel Cells and Bifunctional Activity for Oxygen Electrochemistry(2015-02) Yu, Xingwen; Manthiram, Arumugam; Yu, Xingwen; Manthiram, ArumugamItem PRINTING HYDROPHOBIC STAINLESS STEEL GRAPHENE COMPOSITES(University of Texas at Austin, 2023) O'Donnell, M.; Budan, J.; McGuire, J.; Jalagam, P.; Kulkarni, Achyuth; Ansell, T.Y.Hydrophobic surfaces have low surface energies, which prevents water droplets from wetting the surface. Metals typically have high surface energies leading to highly wettable, hydrophilic behavior. Nano-structuring metallic surfaces could be a way of making a metallic surface hydrophobic potentially leading to improved corrosion resistance, drag reduction, etc. 3Dprinting a metal matrix nanocomposite maybe a scalable method to fabricate hydrophobic metals. Graphene nanoplatelets (GNP) were mixed with 316L stainless-steel (SS) powder and printed on a selective laser melting platform. The composite samples included 0, 1, 2, and 3 vol% GNP. Initial printing jobs ran into some issues that were addressed by adding a vibration source and aluminum foil to the inside of the powder hopper. Additionally, energy density was set higher than 60 J/mm3 to avoid lack of fusion issues. Printing of small and large plates of composite samples was performed at energy densities starting from 60 J/mm3 going up to 100 J/mm3 . As-printed composite sample surfaces consistently exhibited hydrophobic behavior with contact angles exceeding 90°. After polishing, the surfaces exhibited hydrophilic behavior. What is compelling; however, is that while contact angles for pure SS was as expected, i.e., angles < 80°, the composite samples showed angles between 80° and 90°, drawing closer to 90° with an increase in GNP.Item Thermodynamic Synthesis of Solution Processable Ladder Polymers(2015-11) Lee, Jongbok; Rajeeva, Bharath Bangalore; Yuan, Tianyu Y.; Guo, Zi-Hao; Lin, Yen-Hao; Al-Hashimi, Mohammed; Zheng, Yuebing; Fang, Lei; Zheng, Yuebing; Zheng, YuebingThe synthesis of a carbazole-derived, well-defined ladder polymer was achieved under thermodynamic control by employing reversible ring-closing olefin metathesis. This unique approach featured mild conditions and excellent efficiency, affording the ladder polymer backbone with minimum levels of unreacted defects. Rigorous NMR analysis on a C-13 isotope-enriched product revealed that the main-chain contained less than 1% of unreacted precursory vinyl groups. The rigid conformation of the ladder-type backbone was confirmed by photophysical analysis, while the extended rod-like structure was visualized under scanning tunneling microscope. Excellent solubility of this polymer in common organic solvents allowed for feasible processing of thin films using solution-casting techniques. Atomic force microscopy and grazing incident X-ray scattering revealed a uniform and amorphous morphology of these films, in sharp contrast to the polycrystalline thin films of its small molecular counterpart.Item Twisted Physics(The Texas Scientist, 2020) The Texas Scientist