서울대 차세대융합기술연구원

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Publications

Conferences

Green Synthesis of SiOx/C Anode Materials for Lithium-Ion Batteries Using Sustai...

The Korean Physical Society, DCC DAEJEON, Korea (2023)

Hyun Seo Yang, Yong Yeol Park, Yong Joon Lee, Seo Young Kang, Ye Rim Kim, Dong Pyo Hong, Ok Sung Jeon, Se Hun Lee, and Young Joon Yoo, Sang Yoon Park

Abstract
In the past, research on replacing graphite, which is used as the anode material for lithium-ion batteries, has primarily focused on solving the low energy density problem. However, due to emerging environmental concerns, it is necessary to conduct research in a direction that minimizes environmental hazards during the material development process, rather than solely focusing on performance. In this study, we introduce SiOx/C produced through the NaCl salt-assisted synthesis method, which can address environmental destruction and hazards, as well as complicated preparation processes, while improving electrochemical performance. The starting material for this synthesis method is rice husk. During the synthesis process, excess NaCl is added to the rice husks, which serves three main purposes: catalytic graphitization, activation of carbon, and formation of amorphous silica. Additionally, the NaCl used in this process can be infinitely and repeatedly reused through dissolution in water after the reaction is complete. As a result, the lithium-ion batteries that use rice husk-derived SiOx/C produced through our salt-assisted method exhibit a high initial charge/discharge capacity of 422.05/915.93 mAh∙g-1 at 0.05 A∙g-1 and high cycle stability over 500 cycles.
Analysis of thermal and electromagnetic shielding properties based on copper/...

The Korean Physical Society, DCC DAEJEON, Korea (2023)

Tae-Han Kim, In-Sung Lee, Yong Bin Bang Young Pyo Jeon, Jun Yong Song, Young Joon Yoo, and Sang Yoon Park

Abstract
In this study, we investigated the thermal and electromagnetic interference shielding properties of copper/diamond composites by varying the size and volume fraction of the diamond particles and the thickness of the interlayer material using 3D finite-difference time-domain (FDTD) simulations.
Copper coated diamond particles have shown great promise for improving the thermal and mechanical properties in semiconductor packaging materials. In addition to these advantages, Cu-coated diamond particles may also have the potential to provide the function of electromagnetic shielding effectiveness due to their electrical conductive properties. These versatile functions of copper/diamond composites can be beneficial to reduce the cost of packaging process and increase the performance of recent advanced semiconductor chips
Enhanced dielectric properties of Be-doped magnesium oxide nanopowder

The Korean Physical Society, DCC DAEJEON, Korea (2023)

Eun Jung Lee, Gyung Hyun Kim, So Yeon Kwon, Yun Ju La, Sang-hwa Lee, Sang Yoon Park, and Young Joon Yoo

Abstract
Among metal oxide, magnesium oxide (MgO) has been widely used in many fields as one of the most important ceramic materials, owing to its applicability in areas such as catalysis, adsorption, refractory ceramic synthesis, nanoelectronics, optoelectronic and sensing devices, and superconducting products. However, it has a relatively low dielectric constant compared to other metal oxide semiconductors which restricts the range of its bandgap and applicability. Here we report the Be-doped magnesium oxide nanopowder showing increased dielectric constant of 10.4 as the Be ion was substituted to 5% without breaking the cubic crystalline structure of MgO.
A sample of MgO powder doped with Be ions was prepared using the Pechini method. The X-ray diffraction showed that the crystal structure of the doped MgO was maintained with very small lattice constant differences. The bonding structure in the lattice of the sample was identified through X-ray photoelectron spectroscopy, and the change in the bonding structure according to the amount of substitution was identified. The dielectric properties of the samples were analyzed as a function of frequency at room temperature. The real and imaginary parts of the dielectric constant were studied as a function of frequency and composition. It was confirmed that the dielectric constant increased as the Be ions were substituted. We suggest that improving the low dielectric properties of pure MgO can enable the application of MgO to wide bandgap and high voltage applications simultaneously.
Low leakage current metal-insulator-metal structure based on beryllium ...

The Korean Physical Society, DCC DAEJEON, Korea (2023)

So Yeon Han, Min Ji Lee, Hak Ji Lee, Ju Sang Park, Young Pyo Jeon, Young Joon Yoo, and Sang Yoon Park

Abstract
Beryllium oxide (BeO) is believed to be an attractive material for use in upcoming industries such as semiconductors, spacecraft, aircraft, and rocket technologies due to its high bandgap energy, melting point, thermal conductivity, and dielectric constants. The most common method used to produce BeO is the Pechini method. Pechini synthesis has successfully been adapted to 100 different mixed oxide compounds, including perovskite powders and metal oxide films, since the method was introduced. However, limitations of conbentional Pechini techniques include a lack of morphology controls for the thin film process due to the viscosity of the gel precursor and the inhomogeneous nucleation that occurs during polyesterification and sintering, respectively. Our approach is a novel method to create BeO insulting layer based on a two-step spin-coating innovation of the conventional Pechinisynthesis method. The surface morphology and the crystal structure of BeO thin films were observed to be dependent on the citric acid/beryllium sulfate ratio and the sintering temperature, respectively. Finally, the leakage current of a plannal metal-insulator-metal device consistingof Au/Ti/BeO thin film/Ti/Au electrodes was determined to perform low leakage current
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.

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