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You searched for +publisher:"Clemson University" +contributor:("Dr. Apparao M. Rao, Committee"). Showing records 1 – 3 of 3 total matches.

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Clemson University

1. Mallineni, Sai Sunil Kumar. Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications.

Degree: PhD, Physics and Astronomy, 2018, Clemson University

Two-dimensional (2D) materials have been intriguing physicists and material scientists for more than two decades due to their unique physical properties that emerge from phenomena such as charge confinement, heat flow in a 2D plane, etc. For example, graphene exhibits room temperature quantum Hall effect, quantized optical transmittance, non-local hot carrier transport, and Klein tunneling. Building on such fundamental phenomena, my work focuses on biomolecular sensing, energy generation, and storage using 2D materials such as graphene, graphene oxide, boron nitride, and 2D titanium carbide. Chapter 1 provides an introduction to 2D materials and their current status and their applications. In Chapter 2, the effects of nitrogen dopants in graphene are investigated for its possible applications as a selective permeable membrane. Specifically, I investigated theoretically and confirmed experimentally the influence of nitrogen dopant configuration (viz., graphitic, pyridinic, and pyrrolic) on selective gas permeability of graphene. The N-dopants in non-graphitic configurations (pyridinic and pyrrolic) showed selective permeability to O2 unlike graphitic N-dopants. These results implied that N-doped graphene could potentially be used as an O2 selective permeable membrane in devices such as Li-air batteries. In addition to the use of high surface area 2D materials in energy storage as discussed in Chapter 2, I also demonstrated the use of 2D materials (particularly, graphene and titanium carbide) for energy generation as described in Chapter 3 using novel “triboelectric nanogenerators (TENGs)”. Notably, in Chapter 3 I provide blueprints for flexible and wearable TENGs that can be directly integrated with textiles, automobiles, and ocean wave energy harvesters. Lastly, in Chapter 3 I demonstrate new strategies for additive manufacturing of 2D material-based TENGs that convert mechanical energy into electricity and wirelessly transmit it for storage in batteries and capacitors. In Chapter 4, the use of novel 2D nanomaterials such as graphene, graphene oxide, and boron nitride for bio-sensing applications is demonstrated. In particular, the fundamental interactions of aromatic amino acids viz., tyrosine, tryptophan, and phenylalanine with 2D materials were studied using a comprehensive array of tools including Raman spectroscopy, cyclic voltammetry, and photoluminescence spectroscopy. In summary, my work epitomizes the unique electronic and optical properties of 2D materials and their use in a variety of sensors and sustainable energy devices. Advisors/Committee Members: Dr. Apparao M Rao, Committee Chair, Dr. Ramakrishna Podila, Co-Chair, Dr. Terry M Tritt, Dr. Goutam Koley.

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APA (6th Edition):

Mallineni, S. S. K. (2018). Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2124

Chicago Manual of Style (16th Edition):

Mallineni, Sai Sunil Kumar. “Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications.” 2018. Doctoral Dissertation, Clemson University. Accessed November 25, 2020. https://tigerprints.clemson.edu/all_dissertations/2124.

MLA Handbook (7th Edition):

Mallineni, Sai Sunil Kumar. “Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications.” 2018. Web. 25 Nov 2020.

Vancouver:

Mallineni SSK. Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications. [Internet] [Doctoral dissertation]. Clemson University; 2018. [cited 2020 Nov 25]. Available from: https://tigerprints.clemson.edu/all_dissertations/2124.

Council of Science Editors:

Mallineni SSK. Two-dimensional Nanomaterials for Renewable Energy Generation and Sensing Applications. [Doctoral Dissertation]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_dissertations/2124

2. Childress, Anthony. Graphene Foam and Helically Coiled Carbon Nanotubes as Electrodes in Energy Storage Devices.

Degree: PhD, Physics and Astronomy, 2018, Clemson University

Since their inception, carbon nanomaterials have been exploited for use in energy storage. The discovery of carbon nanotubes and the later isolation of graphene opened new avenues in electrode research for batteries and electric double layer capacitors (EDLCs). Their combination of flexibility, mechanical robustness, and electronic conductivity make them ideal for use as active materials and additives. My research has focused on the synthesis and implementation of helical carbon nanotubes (HCNTs) for supercapacitors and few-layer graphene in the form of graphene foam (GF) for aluminum-ion batteries. The presence of defects and dopants was controlled in each system to determine how they relate to the performance of the electrode materials. For each material, Raman spectroscopy served as a key analytical tool. Over the past two decades, the Raman modes of carbon nanotubes and graphene have been well characterized and their relation to various aspects of the graphitic lattice such as defect density, dopant type, and lattice constants have been determined. I used these characteristics to correlate material properties to electrode performance. In the first chapter, I give an overview of the properties and energy storage applications of graphene and carbon nanotubes. The second chapter concerns the basic information needed to understand the electrochemical and spectroscopic methods used to analyze the samples, as well as the instrumentation and equipment used for measurements. In the third chapter, I discuss graphene foam cathodes as used in aluminum-ion batteries. For the graphene foam studies, the methods of producing the foams and Al-ion battery components were optimized before beginning electrochemical characterization, and are described in section 3.1.2. The intercalation process of the chloroaluminate anions was studied by in situ Raman spectroscopy applied to charge/discharge cycling of the cells. The role of surface defects and nitrogen dopants in the performance of few-layer graphene was studied using this method and correlated to performance using several electrochemical techniques. The fourth and final chapter details my work with HCNTs. I first synthesized them using chemical vapor deposition methods which are commensurate with scalable processing, as described in section 4.2. They were prepared for electrochemical testing in two forms: vertically aligned arrays of various heights on metal substrates and freestanding entangled carpets known as buckypapers. They were then characterized spectroscopically and electrochemically and found to possess superior performance to that of linear carbon nanotube analogues. The HCNT buckypapers were also found to be superior scaffolds for polymer composites by virtue of retaining a greater mass loading of polymer, leading to improved capacitance. Advisors/Committee Members: Dr. Apparao M. Rao, Committee, Chair Dr. Ramakrishna Podila, Dr. George Chumanov, Dr. Terry Tritt.

Subjects/Keywords: batteries; carbon nanotubes; electrochemistry; graphene; Raman spectroscopy; supercapacitors

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APA (6th Edition):

Childress, A. (2018). Graphene Foam and Helically Coiled Carbon Nanotubes as Electrodes in Energy Storage Devices. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2159

Chicago Manual of Style (16th Edition):

Childress, Anthony. “Graphene Foam and Helically Coiled Carbon Nanotubes as Electrodes in Energy Storage Devices.” 2018. Doctoral Dissertation, Clemson University. Accessed November 25, 2020. https://tigerprints.clemson.edu/all_dissertations/2159.

MLA Handbook (7th Edition):

Childress, Anthony. “Graphene Foam and Helically Coiled Carbon Nanotubes as Electrodes in Energy Storage Devices.” 2018. Web. 25 Nov 2020.

Vancouver:

Childress A. Graphene Foam and Helically Coiled Carbon Nanotubes as Electrodes in Energy Storage Devices. [Internet] [Doctoral dissertation]. Clemson University; 2018. [cited 2020 Nov 25]. Available from: https://tigerprints.clemson.edu/all_dissertations/2159.

Council of Science Editors:

Childress A. Graphene Foam and Helically Coiled Carbon Nanotubes as Electrodes in Energy Storage Devices. [Doctoral Dissertation]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_dissertations/2159

3. Zhu, Jingyi. Defects in Graphene: Electrochemical, Magnetic, and Optical Properties.

Degree: PhD, Physics, 2016, Clemson University

Graphene has attracted tremendous attention due to its unique proper- ties, such as its two-dimensional structure, zero-band-gap, and linear dispersion relation of its electronic band structure, which are all very interesting from a fundamental standpoint. In addition, its ultra-light weight, high surface area, exceptional electrical and thermal conductivities, as well as robust mechanical strength portends huge potential in diverse applications. Defects in the otherwise perfectly hexagonal lattice of graphene lead to lattice symmetry breaking, and the emergence of new fundamental properties of graphene. Therefore, to understand the role of defects in graphene and further to control the fundamental characteristics of graphene through quantity and configuration of defects (or defect-engineering), it is essential to develop effective synthesis methods. This thesis describes such synthesis methods and the role of controlled defects on the electrochemical, magnetic, as well as the optical properties of graphene. Following the first two introductory Chapters, in Chapter 3 I describe the effects of vacancies and dopants on the electrochemical properties of graphene. Carbon is an excellent electrode material in high-energy and high-power density supercapacitors (SCs) due to its economic viability, high-surface area, and high stability. Although graphene has high theoretical surface area, and hence high double layer capacitance, the net amount of energy stored in graphene-SCs is much below the theoretical limits due to two inherent bottlenecks: i) their low quantum capacitance, and ii) limited ion-accessible surface area. We demonstrate that properly designed defects in graphene effectively mitigates these bottlenecks by drastically increasing the quantum capacitance and opening new channels to facilitate ion diffusion in the otherwise inaccessible interlayer gallery space in few layer graphene. Our results support the emergence of a new energy paradigm in SCs with 150% enhancement in double layer capacitance beyond the theoretical limit. Furthermore, we demonstrate defect engineering in graphene foams as an example of prototype bulk SCs with energy densities of 500% higher than the state-of-the-art commercial SCs without compromising the power density. Chapter 4 focuses on the magnetic properties of graphene when a dopant, such as a sulfur atom, is incorporated into the hexagonal framework of graphene. Bulk graphite is diamagnetic in nature, however, graphene is known to exhibit either a paramagnetic response or weak ferromagnetic ordering. Although many groups have attributed this magnetism in graphene to defects or presence of unintentional magnetic impurities, compelling evidence to pinpoint origin of magnetism in graphene was lacking. To address this issue, we systematically studied the influence of entropically necessary intrinsic defects (e.g., vacancies, edges) and extrinsic dopants (e.g., S-dopants) on the magnetic properties of graphene. We found that the saturation magnetization of graphene… Advisors/Committee Members: Dr. Apparao M. Rao, Committee Chair, Dr. Jian He, Dr. Shiou-Jyh Hwu, Dr. Mark E. Roberts.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Zhu, J. (2016). Defects in Graphene: Electrochemical, Magnetic, and Optical Properties. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1809

Chicago Manual of Style (16th Edition):

Zhu, Jingyi. “Defects in Graphene: Electrochemical, Magnetic, and Optical Properties.” 2016. Doctoral Dissertation, Clemson University. Accessed November 25, 2020. https://tigerprints.clemson.edu/all_dissertations/1809.

MLA Handbook (7th Edition):

Zhu, Jingyi. “Defects in Graphene: Electrochemical, Magnetic, and Optical Properties.” 2016. Web. 25 Nov 2020.

Vancouver:

Zhu J. Defects in Graphene: Electrochemical, Magnetic, and Optical Properties. [Internet] [Doctoral dissertation]. Clemson University; 2016. [cited 2020 Nov 25]. Available from: https://tigerprints.clemson.edu/all_dissertations/1809.

Council of Science Editors:

Zhu J. Defects in Graphene: Electrochemical, Magnetic, and Optical Properties. [Doctoral Dissertation]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_dissertations/1809

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