Facile Synthesis of Poly(3,4-ethylene dioxythiophene) Intercalated Potassium Va...

2022 Fall meeting & Academic Presentation of the Korean Electrochemical Society, BEXCO BUSAN, Korea (2022)

Yong Yeol Park, Se Hun Lee, Ok Sung Jeon, Young Pyo Jeon, Dongpyo Hong, Seoyoung Kang, Sang Yoon Park, Yuanzhe Piao

Abstract
Since lithium-ion batteries (LIBs) have problems such as, high prices (lithium, 70.66 $ kg-1) by lack of raw material reserves (lithium, 13 million tons), and intrinsic safety issues by flammability/toxicity.
Therefore, research on aqueous zinc ion batteries (AZIBs) with characteristics such as abundant reserves (Zinc, 280 million tons), eco-friendliness, and high stability is in the spotlight. The vanadate, one of the representative cathode materials of AZIBs, can indicate high capacity in a multivalent state, have abundant reserves, and have a layered structure, which facilitates intercalation/de-intercalation of zinc ions into the lattice of vanadate. Recently, many studies have been reported on vanadate having the structure of MxV6O16 * nH2O containing cationic metal ions & water molecules that can provide a pillar & lubricant effect. However, these vanadates still have some challenges to overcome. First, most of the methods for synthesizing vanadates with the structure of MxV6O16 * nH2O use the hydrothermal method, which is difficult to scale-up and requires a long reaction time. Second, it is necessary to solve the problem of low conductivity, which is an inherent problem of vanadium-based compounds. In this study, we synthesized one-dimensional (ID) structured potassium vanadete nanofibers (PVNF) in a relativey short reaction time compared to hydrothernal methods using the sonochemical method. In addition, to further improve electrical cinductivity, a composite (E-PVNF) in which a PEDOT is inseted between PVNF layers was designed. The synthesized PVNF and E-PVNF have a 1D morphology, so the rate capability can be improved by short ion pathways and large active areas in the device. In particular, the E-PVNF was avle to further widen the distance between the PVNF layers from 0.81 nm to 0.94 nm by intercalating a PEDOT. Such a wide interlayer distance of E-PVNF enables a faster ion diffusion and shows excellent rate capability.

Analogue of electromagnetically-induced transparency based on magnesium-ferri...

The Korean Physical Society, BEXCO BUSAN, Korea (2022)

Tae-Han Kim, Yongbin Bang, Sang Yoon Park and Bo Wha Lee

Abstract
Electromagnetically-induced transparency (EIT) within a wide avsorption profile is due to the quantum destructive interference of two different transition channels in three-level atomic systems. EIT-like effects of metamaterials also arise due to the near-field coupling between adjacent resonators and the estructive interference between bright and dark modes , or between bright and bright modes. The analogy of EIT effect in magnesium-ferrite metamaterials is characterized by employing a 3D finite-difference time-domain (FDTD) simulation. The magnesium-ferrite metamaterials consist of a cross resonator (CR) on the upper side and a disk resonator (DR) on the lower side of polymide substrate, respectively. The analysis of the FDTD simulation revealed the dynamics of electromagnetic field. the near field couplings of CR and DR, and the EIT- like spectral features of our designed magnesium-ferrite metamaterials as functions of the asymmetric parameter and polarization angle.
At the special asymmetric parameter, the group index and the group delay are reached up to 6485 and 238.4 ps at 0.729 THz, respectively. Moreover, the figure of merit of 416 and th Q-factor of 644 are also obtained. These results may give a physical understanding of various potential applications such as slow-light devices, THz sensors, tunable switching, etc. in THz regime.

Dough-type zinc air battery with self-humidifying system

The Korean Electrochemical Society, ICC JEJU, Korea (2022)

Ok Sung Jeon, Yong Yeol Park, Eun Seo Ko, Se Hun Lee, Dong Pyo Hong, Young Pyo Jeon, Jun Yong Song, Sang Yoon Park

Abstract
Advances in battery technology have encouraged researchers to develop a suitable source of power. Researchers have recently focused on flexibility and portability to apply versatile fields and devices. While the current most commercial system of the market is based on lithium ion batteries, it has significant limitations to reach to the level of achievement that has never been paralleled due to its mature stages of technology. Furthermore, as known, subsequent battery explosion accidents require the development of next-generation batteries with higher stability. For these reasons, new battery systems of zinc air battery are renewed subjects. It had larger energy density, lower prices and more cost-efficient than post-lithium ion technology. On the other hand, Zn-air batteries still have many problems to solve. One significant barrier is its drying out system. Drying out of electrolyte led to decrease ionic conductivity permanently. While proceeding works has been focused on the electrodes and outward appearance such as flexible type or solid-state batteries to increase performance and application, we focused on solving the problem arising from drying out of electrolyte without external devices or systems. In addition, increasing moldability of zinc-air battery to extend application. Utilizing sodium alginate as electrolyte component, we discovered that gum-type zinc-air battery can be manufactured and show self-humidifying property. It was controlled the composition of electrolyte to optimize the tendencies of water adsorption and drying out to have less impact on performance. It shows new concept of development of zinc-air battery system and possibility of increasing durability.

Synthesis of Conducting Polymer Intercalated Ammonium Vanadate Nanofiber Compos...

The Korean Electrochemical Society, ICC JEJU, Korea (2022)

Se Hun Lee, Ok Sung Jeon, Young Pyo Jeon, Yong Yeol Park, Sang Yoon Park

Abstract
The zinc-ion batteries (ZIBs) using aqueous electrolytes are a promising energy storage device. In the field of ZIBs, vanadate-based cathode materials are attracting attention because of their high charge storage capacity by the layered structure and multiple valences, however, in order to have high charge/discharge cycle stability and high-rate capability, obstacles such as low electrical conductivity and trapping of diffusion ions within crystal structure still remain a problem to be solved. Here we report the synthesis of Poly(3,4-ethylenendioxythiophene) (PEDOT) intercalated ammonium vanadate nanofiber (AVNF) composites by oxidative polymerization of 3,4-ethylene dioxythiophene (EDOT) with V2O5 as a host material in intercalation. Morphologies and electrochemical analyses of two different samples AVNF, PEDOT/AVNF (E-AVNF)) were compared. Upon intercalation, the interplanar spacing of AVNF and E-AVNF expand from 7.82Å to 10.27Å respectively. The resulting E-AVNF (1.9ൈ10-2 S/cm) show improved conductivity which compared to the AVNF (5.1ൈ10-3 S/cm). The cation and conducting polymers co-intercalated vanadate nanofiber (E-AVNF) cathode exhibited a reversible capacity of 344 mAh g-1 at a current density of 0.5 A g-1 and 155 mAh g-1 even at an extremely high current density of 20 A g-1, demonstrating excellent rate capability. The E-AVNF cathode also showed high cycle stability, maintaining 92% of its initial specific capacity after 1000 cycles at 20 A g-1. This study can be a steppingstone to take a step closer to the next generation of ZIBs that will replace LIBs.

Keywords: Aqueous zinc-ion battery, Vanadate, Intercalation, Conducting polymer, Nanofiber, Sonochemical method

Neutron Endurance of the Al2O3 on the Reduced-activation Ferritic/Martensitic St...

Korean Physical Society Fall Meeting 2021, Online conference (2021)

Hyun Seo Yang. Sang-hwa Lee, Young-ku Jin, Jooohwan Ha, Dongpyo Hong, Ok Sung Jeon, Tae Han Kim, Yong Yeol Park, Dong min Kim and Young Joon Yoo, Sang Yoon Park

Abstract
국제핵융합실험로 (International Thermonuclear Experimental Reactor)를 구성하는 요소들은 중성자 조사와 수소 동위원소 투과에 의해 결함이 발생한다. 중수소(2H)와 삼중수소(3H)는 핵융합발전에 필요한 연료이며, 삼중수소를 재생산하기 위해 6Li(n,α)3H 반응을 일으키기 위한 TBM(Test Blanket Module)이 개발되었다. 이러한 이유로 TBM 구성요소들은 중성자에 노출되기 때문에, 저방사화를 위해 개발된 RAFM (Reduced-Activation Ferritic/Martensitic) 강으로 구성되며, 이는 또한 수소동위원소 투과에도 노출되어 있다.
Al2O3은 압축의 강도, 내마모성, 화학적 안정성, 그리고 수소에 대한 낮은 용해도를 갖기 때문에 수소동위원소 투과도를 낮추기 위한 투과방지막 소재로써 적합하다. 최근에는, Al2O3에 점결함이 발생할 경우, PRF (Permeation Reduction Factor)를 변화시킬 수 있음이 DFT 계산결과로 보고되었다.
따라서, 중성자 조사에 따른 Al2O3의 결함발생과 수소동위원소 투과도의 상관관계를 분석하는 것이 필요하다. 본 연구에서는 Al2O3의 중성자조사결함과 충돌열에 의한 Al2O3/RAFM의 열변형률을 계산하였다.

Neutron Endurance of the Al2O3 on the SS316L

International Conference on Advanced Materials and Devices, Jeju, Korea (2021)

Hyun Seo Yang. Sang-hwa Lee, Young-ku Jin, Jooohwan Ha, Dongpyo Hong, Ok Sung Jeon, Tae Han Kim, Yong Yeol Park, Dong min Kim and Young Joon Yoo, Sang Yoon Park

Abstract
ITER (International Thermonuclear Experimental Reactor) components are facing the defects of materials by neutron irradiation and hydrogen isotope permeation. The hydrogen isotopes, which are deuterium (2H) and tritium (3H), are the most promising fusion fuel and dissolve and penetrate most metals, causing embrittlement, destroying materials. The TBM (Test Blanket Module) is attached for the reproduction of tritium by 6Li(n,α)3H reaction, and constructed by RAFM (Reduced-Activation Ferritic/Martensitic) steel, which is for the low activation.
The Al2O3 (Alumina), reinforcement has compressive strength, wear resistance, chemical stability, and low solubility for hydrogen. These properties revealed that the Al2O3 is suitable as a hydrogen permeation barrier to improve the PRF (Permeation Reduction Factor). As following the first-principle calculation, the point defects in Al2O3 are performing as a hydrogen trapping factor, while varying the PRF.
It is necessary to quantify the neutron irradiation damage of the Al2O3 and RAFM steel. We calculated displacement per atom and strain by neutron collision heating to evaluate the strain due to the difference of the thermal expansion coefficient of Al2O3 and RAFM steel.

Enhanced Smith-Purcell radiation in frequency independent dielectric grating

2012 IEEE 13th International Vacuum Electronics Conference, IVEC 2012

Bera A., Barik R.K., Min S.-H., Kwon O., Baek I., Kim S., Sattorov M.A., Park G.-S.

Abstract
In this paper we show that the Cerenkov radiation in artificial dielectric (metamaterial) noticeably increases Smith-Purcell radiation (SPR) intensity from the metamaterial grating if the two radiation condition is properly matched. We compare the radiated field intensity from lamellar metal grating and metamaterial grating and found that radiated field intensity of metamaterial grating is more intense than radiated field intensity of lamellar grating. © 2012 IEEE.

Effect of surface roughness of high current density nano-particle cathode for te...

2012 IEEE 13th International Vacuum Electronics Conference, IVEC 2012

Barik R.K., Tanwar A.K., Baek I.K., Eom K., Bera A., Sattorov M.A., Min S.H., Kwon O.J., Park G.S.

Abstract

High current density dispenser cathode is critical need for used in high power terahertz devices. Recently scandate cathode using nanoparticle offers very high current density more than 100 A/cm 2. Fabrication of this kind of cathode is challenging issue due to its nano dimension of the particle size. One of the critical parameter is surface roughness of the emission surface. We develop dispenser cathode using tungsten nano-particle of average particle diameter 50 nm, spherical morphology and uniform phase. In this paper we explain the effect of surface roughness on the emission current density of the dispenser cathode. © 2012 IEEE.

Experimental study on 0.1 THz clinotron

2012 IEEE 13th International Vacuum Electronics Conference, IVEC 2012

Sattorov M., Khutoryan E., Lukin K., Park G.-S., Bera A., Barik R., Kwon O., Min S.-H., Sharma A., Tanwar A.

Abstract

A multimode theory of resonant backward wave oscillator with inclined electron beam Clinotron is introduced. The mechanism of the efficiency enhancement due to mode interaction is unveiled through numerical simulation. The experimental setup for 0.1 THz Clinotron is being developed and the details of each part will be presented. © 2012 IEEE.

Irradiative damage characterization of a lysozyme during high-power THz ablation...

International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz

Eom K.H., Peltek S.E., Popik V.M., Jeong Y.U., Kwon O.S., Park W.Y., Lee W.S., So J.H., Park G.S.

Abstract

High-power pulsed THz waves which are generated by free electron laser near 2.2 THz are found to induce the nondestructive ablation of lysozyme. The peak electric field strength exposed on the sample is estimated over 10 kV/cm. The aerosol phase nanoparticles (ablated lysozyme) size is measured using real-time condensation particle counter, and the ablated lysozyme is analyzed using MALDI-TOF mass spectrometry to characterize irradiative damage during THz ablation process. The mass spectrum of ablated lysozyme shows no difference with control, but the sample remaining on the substrate shows thermal oxidation. These results confirm the nondestructive THz ablation of lysozyme; they suggest possible THz biological application such as mass spectrometry or electrospray using high-power pulsed THz waves. © 2012 IEEE.