Browsing by Author "Tiwary, Chandra S."

Now showing 1 - 6 of 6
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    3D Macroporous Solids from Chemically Cross-linked Carbon Nanotubes
    (Wiley, 2014) Ozden, Sehmus; Narayanan, Tharangattu N.; Tiwary, Chandra S.; Dong, Pei; Hart, Amelia H.C.; Vajtai, Robert; Ajayan, Pulickel M.
    Suzuki reaction for covalently interconnected 3D carbon nanotube (CNT) architectures is reported. The synthesis of 3D macroscopic solids made of CNTs covalently connected via Suzuki cross-coupling, a well-known carbon-carbon covalent bond forming reaction in organic chemistry, is scalable. The resulting solid has a highly porous, interconnected structure of chemically cross-linked CNTs. Its use for the removal of oil from contaminated water is demonstrated.
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    A thermally-invariant, additively manufactured, high-power graphene resistor for flexible electronics
    (IOP, 2017) Michel, Monica; Biswas, Chandan; Tiwary, Chandra S.; Saenz, Gustavo A.; Hossain, Ridwan F.; Ajayan, Pulickel; Kaul, Anupama B.
    Solution processed two-dimensional (2D) layered materials and their integration with additive manufacturing techniques, such as ink-jet printing, is a facile approach for incorporating these exotic materials into device platforms for flexible electronics. In this work, graphene ink formulations are successfully utilized toward the design and fabrication of high-power resistive structures that are printed on both rigid and flexible substrates and have the potential to deliver close to 10 W of power. A near-flat, negative temperature coefficient of resistivity (TCR) is measured with an activation energy E a ~ 2.4 meV for electron hopping, which is 100×  lower compared to E a values for high TCR materials. The TCR and E a values are amongst the lowest reported for 2D layered material systems. The thermal-invariance of resistivity for such high-power graphene printed resistors is attractive for applications, for example to provide a stable heating source for flexible electronics over extreme thermal environments. The transport characteristics of the ink-jet printed features is modeled as a composite structure in order to explain the thermal response which appears to be mediated via defects in the sonicated graphite, and correlates well to inferences made from Raman spectroscopy and transmission electron microscopy analysis conducted on the printed graphene structures. In order to fabricate such functional structures with ink-jet printing, the active nozzle number, printing passes, and annealing conditions are shown to play an important role to determine line resolution, and also dictate the morphological and electronic transport characteristics of the printed graphene features.
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    Atomically thin gallium layers from solid-melt exfoliation
    (AAAS, 2018) Kochat, Vidya; Samanta, Atanu; Zhang, Yuan; Bhowmick, Sanjit; Manimunda, Praveena; Asif, Syed Asif S.; Stender, Anthony S.; Vajtai, Robert; Singh, Abhishek K.; Tiwary, Chandra S.; Ajayan, Pulickel M.
    Among the large number of promising two-dimensional (2D) atomic layer crystals, true metallic layers are rare. Using combined theoretical and experimental approaches, we report on the stability and successful exfoliation of atomically thin “gallenene” sheets on a silicon substrate, which has two distinct atomic arrangements along crystallographic twin directions of the parent α-gallium. With a weak interface between solid and molten phases of gallium, a solid-melt interface exfoliation technique is developed to extract these layers. Phonon dispersion calculations show that gallenene can be stabilized with bulk gallium lattice parameters. The electronic band structure of gallenene shows a combination of partially filled Dirac cone and the nonlinear dispersive band near the Fermi level, suggesting that gallenene should behave as a metallic layer. Furthermore, it is observed that the strong interaction of gallenene with other 2D semiconductors induces semiconducting to metallic phase transitions in the latter, paving the way for using gallenene as promising metallic contacts in 2D devices.
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    Bacteria as Bio-Template for 3D Carbon Nanotube Architectures
    (Springer Nature, 2017) Ozden, Sehmus; Macwan, Isaac G.; Owuor, Peter S.; Kosolwattana, Suppanat; Autreto, Pedro A.S.; Silwal, Sushila; Vajtai, Robert; Tiwary, Chandra S.; Mohite, Aditya D.; Patra, Prabir K.; Ajayan, Pulickel M.
    It is one of the most important needs to develop renewable, scalable and multifunctional methods for the fabrication of 3D carbon architectures. Even though a lot of methods have been developed to create porous and mechanically stable 3D scaffolds, the fabrication and control over the synthesis of such architectures still remain a challenge. Here, we used Magnetospirillum magneticum (AMB-1) bacteria as a bio-template to fabricate light-weight 3D solid structure of carbon nanotubes (CNTs) with interconnected porosity. The resulting porous scaffold showed good mechanical stability and large surface area because of the excellent pore interconnection and high porosity. Steered molecular dynamics simulations were used to quantify the interactions between nanotubes and AMB-1 via the cell surface protein MSP-1 and flagellin. The 3D CNTs-AMB1 nanocomposite scaffold is further demonstrated as a potential substrate for electrodes in supercapacitor applications.
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    Fluorine and hydrogen-based adhesive compositions and methods of making the same
    (2021-11-16) Chipara, Alin C.; Chipara, Mircea; Tiwary, Chandra S.; Ajayan, Pulickel M.; Rice University; The Board of Regents of The University Of Texas System; United States Patent and Trademark Office
    Embodiments of the present disclosure pertain to adhesive compositions that include a fluorinated molecule and a hydrogen-containing molecule that are non-covalently associated with one another. The molecules may be non-covalently associated with one another through dipole-dipole interactions that create a fluorine-hydrogen electronegativity difference between at least some of the fluorine atoms of the fluorinated molecule and at least some of the hydrogen atoms of the hydrogen-containing molecule. The fluorinated molecule and the hydrogen-containing molecule may be in different phases, such as a liquid phase for one molecule and a solid phase for the other molecule. Additional embodiments pertain to methods of enhancing an adhesiveness of a surface by applying an adhesive composition of the present disclosure to the surface. Further embodiments pertain to methods of making the adhesive compositions by mixing a fluorinated molecule with a hydrogen-containing molecule such that the molecules become non-covalently associated with one another.
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    Spontaneous hydrogen production using gadolinium telluride
    (Cell Press, 2023) Kumbhakar, Partha; Parui, Arko; Dhakar, Shikha; Paliwal, Manas; Behera, Rakesh; Gautam, Abhay Raj Singh; Roy, Soumyabrata; Ajayan, Pulickel M.; Sharma, Sudhanshu; Singh, Abhishek K.; Tiwary, Chandra S.
    Developing materials for controlled hydrogen production through water splitting is one of the most promising ways to meet current energy demand. Here, we demonstrate spontaneous and green production of hydrogen at high evolution rate using gadolinium telluride (GdTe) under ambient conditions. The spent materials can be reused after melting, which regain the original activity of the pristine sample. The phase formation and reusability are supported by the thermodynamics calculations. The theoretical calculation reveals ultralow activation energy for hydrogen production using GdTe caused by charge transfer from Te to Gd. Production of highly pure and instantaneous hydrogen by GdTe could accelerate green and sustainable energy conversion technologies.