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Two-dimensionally hybridized nanostructures enabled by facile thermochemical processing for high-performance energy materials

  • Incheol Shin (신인철, 대학원 기계공학과 기계공학전공)

초록/요약

In the rapidly changing modern society, nanotechnology is one of the most important research areas. Nanomaterials are attracting attention in various research areas because of the unique physical and chemical properties of materials in the nanoscale, and many studies are also being conducted on ways to use nanomaterials for various applications. One example is the fabrication of nanostructures among methods being studied to use nanomaterials in various applications. Since nanomaterials have various physical properties depending on their structure, nanostructure fabrication has a tunable chemical and physical characteristic as an advantage and can achieve excellent results by forming it suitable for required experimental conditions. Due to the advantages mentioned above, the fabricated nanostructures are suitable for energy materials used in electrochemical energy conversion or energy storage systems. Nanostructures exist in several dimensions, including 1D, 2D, and 3D. Among these, in the case of 2D nanostructures, it is easy to develop into 1D and 3D nanostructures. Also, it has advantages of properties that can be adjusted through control of experimental parameters and excellent specific surface area. In addition, the 2D hybrid nanostructure can exhibit superior performance in a variety of applications such as an electrochemical electrode, energy generation material, an electromagnetic shielding material through the creation of synergy effects from the properties of the materials that are used to hybridize. For fabrication of the 2D hybrid nanostructure with such superior performance through the conventional process, it is necessary to meet the complicated experimental conditions, the experimental equipment that optimized to handling nanomaterials. Also, it is hard to fabricate a uniform structure with the same properties because nanomaterial is susceptible to experimental conditions. Additionally, the irregular growth tendency of nanomaterials in the synthesis of nanomaterials makes the fabrication of nanostructures more difficult. These limitations have the potential to impose excessive cost and burden on nanostructure research and slow the development of research. We intend to contribute to the development of the nanostructure research area by developing a process for synthesizing 2D hybrid nanostructures that are not significantly affected by the experimental environment through an easy thermochemical process.In this study, research was conducted to fabricate 2D hybrid nanostructure and use it as an energy material for various energy systems. Firstly, a high-performance energy conversion system was developed by fabricating a hybrid nanostructure of antimony telluride, a thermoelectric material, and carbon nanotubes. By connecting the antimony telluride particles with carbon nanotubes, it was possible to fabricate a hybrid energy conversion system with excellent electrical conductivity while maintaining thermoelectric performance. To maximize the thermoelectric performance, a thermopower wave process was adopted, and the shortcomings in energy generation time were solved by adding formaldehyde as a functional material. The maximum potential of 34.4mV and a power density of 1.1mW/cm2 were achieved and the increase in energy generation time was 1508%. Next, an energy storage system with excellent performance has been developed. The iron oxide nanowire structure was fabricated through a facile thermochemical process different from the conventional process, and research was conducted to use it as a supercapacitor electrode. In addition to the natural abundance, low price, and theoretical capacitance of conventional iron oxide, the iron oxide nanowire structure has the advantage of the high specific surface area resulting from the irregular and fine shape of structures. This excellent iron oxide nanowire structure was formed as a supercapacitor electrode by fabricating a 2D hybrid nanostructure with carbon paper and performing a Joule heating process. As a result of this research, the iron oxide nanowire structure fabricated by mechanical stirring at 80 degrees for 2 hours showed the highest specific capacitance result of 91675 F/m2 at a scan rate of 5 mV/s. This study presented several methods of fabricating 2D hybrid nanostructures through easy thermochemical processes, and through this, it will be able to contribute to the development of the nanostructure research area. In each of the researches covered in this paper, the fabricated 2D hybrid nanostructure was applied to the energy conversion system and the supercapacitor electrode, respectively, and it was suggested that the 2D hybrid nanostructure has high potential value as an energy material. Continuous research and development in the field of hybrid nanostructure research are expected to accelerate performance improvement in energy materials. In addition to the applications covered in this study, it is expected that it can be applied to various applications such as fire and heat sensors, electromagnetic shielding materials, battery electrodes, catalysts, etc., simply by making slight changes to the precursor and process.

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목차

Chapter 1. Introduction 1

Chapter 2. Enhanced Charge Generation of Thermopower Waves using Formaldehyde based on MWCNT@Sb2Te3@NC@COx Composite Structures 5
2.1. Introduction 5
2.2. Experimental 10
2.3. Result and discussion 14
2.4. Conclusion 30

Chapter 3. Iron Oxide nanowire structure for energy storage device 32
3.1. Introduction 32
3.2. Experimental 36
3.3. Result and discussion 40
3.4. Conclusion 53

Chapter 4. Conclusions 54

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