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Choi, Jaeyoo,Jung, Yeonsu,Yang, Seung Jae,Oh, Jun Young,Oh, Jinwoo,Jo, Kiyoung,Son, Jeong Gon,Moon, Seung Eon,Park, Chong Rae,Kim, Heesuk American Chemical Society 2017 ACS NANO Vol.11 No.8
<P>As practical interest in flexible/or wearable power-conversion devices increases, the demand for high-performance alternatives to thermo-electric (TE) generators based on brittle inorganic materials is growing. Herein, we propose a flexible and ultralight TE generator (TEG) based on carbon nanotube yarn (CNTY) with excellent TE performance. The as prepared CNTY shows a superior electrical conductivity of 3147 S/cm due to increased longitudinal carrier mobility derived from a highly aligned structure. Our TEG is innovative in that the CNTY acts as multifunctions in the same device. The CNTY is alternatively doped into n- and p-types using polyethylenimine and FeCl3, respectively. The highly conductive CNTY between the doped regions is used as electrodes to minimize the circuit resistance, thereby forming an all-carbon TEG without additional metal deposition. A flexible TEG based on 60 pairs of n- and p-doped CNTY shows the maximum power density of 10.85 and 697 mu W/g at temperature differences of 5 and 40 K, respectively, which are the highest values among reported TEGs based on flexible materials. We believe that the strategy proposed here to improve the power density of flexible TEG by introducing highly aligned CNTY and designing a device without metal electrodes shows great potential for the flexible/or wearable power-conversion devices.</P>
최재유(Choi, Jaeyoo) 담화·인지언어학회 2021 담화와 인지 Vol.28 No.2
This paper describes cognitive neural network and conceptual blending theory, showing that literary research has a place in cognitive linguistic studies. These cognitive mechanisms say that the mind is inherently embodied, that thought is mostly unconscious and that abstract concepts are largely metaphorical. I raise some questions of cognitive unconsciousness and metaphors, conceptual blending and more spaciously within cognitive operations, I try to review the cognitive linguistic metaphoric system in Fitzgerald’s novel, The Great Gatsby. The society in-Fitzgerald’s novels is not always beautiful and friendly to man, but more often indifferent and hostile to him. In a highly industrialized modern world, man cannot but feel an extreme sense of confrontation, conflicts, and alienation between man and society as well as man and man. There exist various aspects between idealism and materialism by giving many characters in The Great Gatsby. Moral was destroyed by the pursuit of physical pleasure, and only the sense of emptiness and boredom was prevalent. As a consequence of analyzing the novel, this study asserts that critical thoughts in consilience raise questions as to our fundamental principles and give them fresh creative theories.
Jo, Kiyoung,Choi, Jaeyoo,Kim, Heesuk The Royal Society of Chemistry 2017 Journal of Materials Chemistry C Vol.5 No.22
<P>Modulating the electrical properties of transition metal dichalcogenides (TMDs) is of fundamental importance for applications in nanoelectronic devices and can be achieved through the exfoliation of a bulk material into nanosheets or controlled doping. In this study, the simultaneous exfoliation and n-doping of a TMD,<I>i.e.</I>, MoS2, is achieved for the first time<I>via</I>a solution process using benzyl viologen (BV) and hydrazine. The MoS2sample exfoliated by the BV molecules has an average thickness of 2.68 nm and a lateral size of 200-900 nm, indicating bi- or tri-layered MoS2nanosheets. These nanosheets have an electrical conductivity (2.28 × 10<SUP>−1</SUP>S m<SUP>−1</SUP>) that is higher by one order of magnitude than that of bulk MoS2due to the effective n-doping by BV molecules. As a proof of concept, the thermoelectric properties of the exfoliated MoS2-BV nanosheets are characterized, which reveals an enhanced Seebeck coefficient (−360 μV K<SUP>−1</SUP>) due to quantum confinement by successful exfoliation. The electrical conductivity and Seebeck coefficient are the highest values among those of MoS2nanosheets previously prepared by a solution-process. This newly proposed strategy for simultaneous exfoliation and doping can be used to control the electrical properties of MoS2, thus showing great potential for further development of 2D TMD-based electronic and energy devices.</P>
Laser-based three-dimensional manufacturing technologies for rechargeable batteries
Moldovan Dan,Choi Jaeyoo,Choo Youngwoo,김원식,Hwa Yoon 나노기술연구협의회 2021 Nano Convergence Vol.8 No.23
Laser three-dimensional (3D) manufacturing technologies have gained substantial attention to fabricate 3D structured electrochemical rechargeable batteries. Laser 3D manufacturing techniques offer excellent 3D microstructure controllability, good design flexibility, process simplicity, and high energy and cost efficiencies, which are beneficial for rechargeable battery cell manufacturing. In this review, notable progress in development of the rechargeable battery cells via laser 3D manufacturing techniques is introduced and discussed. The basic concepts and remarkable achievements of four representative laser 3D manufacturing techniques such as selective laser sintering (or melting) techniques, direct laser writing for graphene-based electrodes, laser-induced forward transfer technique and laser ablation subtractive manufacturing are highlighted. Finally, major challenges and prospects of the laser 3D manufacturing technologies for battery cell manufacturing will be provided.
Park, Kyung Tae,Choi, Jaeyoo,Lee, Bora,Ko, Youngpyo,Jo, Kiyoung,Lee, Young Mo,Lim, Jung Ah,Park, Chong Rae,Kim, Heesuk The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.40
<P>As future thermoelectric generators (TEGs) require flexibility and mass-producibility, the demand for high-performance TEGs based on printed thermoelectric (TE) materials is growing. Herein, we have rationally designed a bracelet-type TEG structure where the carbon nanotube (CNT) ink is printed in the in-plane direction of a flexible cable and the device is operated in the out-of-plane direction of the heat source. This is the first report to fabricate a flexible TEG by printing the TE ink on a curved surface. For printing the CNT ink on a curved surface, the viscosity, dispersibility, and TE performance of the CNT ink have been fundamentally studied. Especially, the mechanism of the solvent effect on the dispersion and viscosity of the CNT ink during planetary ball milling has been clarified. The flexible TEG based on 60 pairs of n- and p-doped CNT ink shows the maximum power output of 1.95 μW at a temperature difference of 30 K, which is one of the highest power outputs for flexible TEGs based on CNT inks. The ease of installment of the bracelet-type TEG on heat sources with various shapes and its ability to harvest waste heat in the out-of-plane direction of the heat source has great potential as flexible/or wearable power conversion devices.</P>