Search

Your search keyword '"Gullapalli, Hemtej"' showing total 39 results
Start Over Author "Gullapalli, Hemtej"
39 results on '"Gullapalli, Hemtej"'

7. Stacked On-Chip Supercapacitors for Extreme Environments

Author

Baburaj, Abhijit, primary, Gullapalli, Hemtej, additional, Puthirath, Anand B., additional, Salpekar, Devashish, additional, Joyner, Jarin, additional, Kosolwattana, Suppanat, additional, Vajtai, Robert, additional, Ganguli, Babu, additional, and Ajayan, Pulickel M., additional

Published
2022
Full Text
View/download PDF

21. Graphene Growth via Carburization of Stainless Steel and Application in Energy Storage

Author

ARMY RESEARCH LAB ADELPHI MD, Gullapalli, Hemtej, Reddy, Arava L, Kilpatrick, Stephen, Dubey, Madan, Ajayan, Pulickel M, ARMY RESEARCH LAB ADELPHI MD, Gullapalli, Hemtej, Reddy, Arava L, Kilpatrick, Stephen, Dubey, Madan, and Ajayan, Pulickel M

Abstract

A modified version of the carburization process, a widely established technique used in the steel industry for case hardening of components, is used for the growth of graphene on stainless steel. Controlled growth of high-quality single- and few-layered graphene on stainless steel (SS) foils through a liquid-phase chemical vapor deposition (CVD) technique is reported. Reversible Li intercalation in these graphene-on-SS structures is demonstrated, where graphene and SS act as electrode and current collector, respectively, providing very good electrical contact. Direct growth of an active electrode material, such as graphene, on current-collector substrates makes this a feasible and efficient process for developing thin-film battery devices., Published in Small, v7 n12 p1697-1700, 2011.

Published
2011

22. Flexible ZnO-Cellulose Nanocomposite for Multisource Energy Conversion

Author

Instituto Potosino de Investigación Científica y Tecnológica - Advanced Materials Department, Kumar, Ashavani, Gullapalli, Hemtej, Balakrishnan, Kaushik, Botello Mendez, Andrés Rafael, Vajtai, Robert, Terrones, Mauricio, Ajayan, Pulickel M., Instituto Potosino de Investigación Científica y Tecnológica - Advanced Materials Department, Kumar, Ashavani, Gullapalli, Hemtej, Balakrishnan, Kaushik, Botello Mendez, Andrés Rafael, Vajtai, Robert, Terrones, Mauricio, and Ajayan, Pulickel M.

Abstract

Materials with the ability to harness multiple sources of energy from the ambient environment could lead to new types of energy-harvesting systems. It is demonstrated that nanocomposite films consisting of zinc oxide nanostructures embedded in a common paper matrix can be directly used as energy-conversion devices to transform mechanical and thermal energies to electric power. These mechanically robust and flexible devices can be fabricated over large areas and are capable of producing an output voltage and power up to 80 mV and 50 nW cm−2, respectively. Furthermore, it is shown that by integrating a certain number of devices (in series and parallel) the output voltage and the concomitant output power can be significantly increased. Also, the output voltage and power can be enhanced by scaling the size of the device. This multisource energy-harvesting system based on ZnO nanostructures embedded in a flexible paper matrix provides a simplified and cost-effective platform for capturing trace amounts of energy for practical applications.

Published
2011

23. Synthesis of Nitrogen-Doped Graphene Films for Lithium Battery Application

Author

RICE UNIV HOUSTON TX DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE, Reddy, Arava L, Srivastava, Anchal, Gowda, Sanketh R, Gullapalli, Hemtej, Dubey, Madan, Ajayan, Pulickel M, RICE UNIV HOUSTON TX DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE, Reddy, Arava L, Srivastava, Anchal, Gowda, Sanketh R, Gullapalli, Hemtej, Dubey, Madan, and Ajayan, Pulickel M

Abstract

We demonstrate a controlled growth of nitrogen-doped graphene layers by liquid precursor based chemical vapor deposition (CVD) technique. Nitrogen-doped graphene was grown directly on Cu current collectors and studied for its reversible Li-ion intercalation properties. Reversible discharge capacity of N-doped graphene is almost double compared to pristine graphene due to the large number of surface defects induced due to N-doping. All the graphene films were characterized by Raman spectroscopy, transmission electron microscopy and X-ray photoemission spectroscopy. Direct growth of active electrode material on current collector substrates makes this a feasible and efficient process for integration into current battery manufacture technology.

Published
2010

24. Flexible Piezoelectric ZnO-Paper Nanocomposite Strain Sensor

Author

Instituto Potosino de Investigación Científica y Tecnológica - Advanced Materials Department, Gullapalli, Hemtej, Vemuru, Venkata S. M., Kumar, Ashavani, Botello Mendez, Andrés Rafael, Vajtai, Robert, Terrones, Mauricio, Nagarajaiah, Satish, Ajayan, Pulickel M., Instituto Potosino de Investigación Científica y Tecnológica - Advanced Materials Department, Gullapalli, Hemtej, Vemuru, Venkata S. M., Kumar, Ashavani, Botello Mendez, Andrés Rafael, Vajtai, Robert, Terrones, Mauricio, Nagarajaiah, Satish, and Ajayan, Pulickel M.

Abstract

The fabrication of a mechanically flexible, piezoelectric nanocomposite material for strain sensing applications is reported. Nanocomposite material consisting of zinc oxide (ZnO) nanostructures embedded in a stable matrix of paper (cellulose fibers) is prepared by a solvothermal method. The applicability of this material as a strain sensor is demonstrated by studying its real-time current response under both static and dynamic mechanical loading. The material presented highlights a novel approach to introduce flexibility into strain sensors by embedding crystalline piezoelectric material in a flexible cellulose-based secondary matrix.

Published
2010

25. Supercapacitor Operating At 200 Degrees Celsius

Author

Borges, Raquel S., primary, Reddy, Arava Leela Mohana, additional, Rodrigues, Marco-Tulio F., additional, Gullapalli, Hemtej, additional, Balakrishnan, Kaushik, additional, Silva, Glaura G., additional, and Ajayan, Pulickel M., additional

Published
2013
Full Text
View/download PDF

29. Protecting copper from electrochemical degradation by graphene coating

Author

Singh Raman, R.K., primary, Chakraborty Banerjee, P., additional, Lobo, Derrek E., additional, Gullapalli, Hemtej, additional, Sumandasa, Madusha, additional, Kumar, Ashwin, additional, Choudhary, Lokesh, additional, Tkacz, Rachel, additional, Ajayan, Pulickel M., additional, and Majumder, Mainak, additional

Published
2012
Full Text
View/download PDF

31. Wetting transparency of graphene

Author

Rafiee, Javad, primary, Mi, Xi, additional, Gullapalli, Hemtej, additional, Thomas, Abhay V., additional, Yavari, Fazel, additional, Shi, Yunfeng, additional, Ajayan, Pulickel M., additional, and Koratkar, Nikhil A., additional

Published
2012
Full Text
View/download PDF

38. Review—Use of impedance spectroscopy for the estimation of Li-ion battery state of charge, state of health and internal temperature

Author

IRC, McCarthy, Kieran, Gullapalli, Hemtej, Ryan, Kevin M., Kennedy, Tadhg, IRC, McCarthy, Kieran, Gullapalli, Hemtej, Ryan, Kevin M., and Kennedy, Tadhg

Abstract

peer-reviewed, The rapid adoption of electric vehicles (EVs) and the evolving needs of portable electronic devices has intensified the need for enhanced state diagnosis of Li-ion batteries (LIBs). As the applications for LIBs continue to grow, so too does their operational requirements; ranging from faster charging and improved safety to optimized energy control and extended lifespan. In order to keep pace with the growing requirements of LIBs, improvements in the monitoring of battery states must be achieved. Although electrochemical impedance spectroscopy (EIS) has existed since the 1960's, its potential as a diagnosis tool has only received widespread attention in recent years. In this paper, a detailed review on the applicability of impedance measurements for the estimation of the vital battery parameters of state of charge (SOC), state of health (SOH) and internal temperature (IT) has been performed.

Catalog

Books, media, physical & digital resources
See catalog results