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Jeong Hyeongwon,SHARMA BHARAT,Jo Seungyeon,Kim Yo Han,Myung Jae-Ha 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.4
LSM–ScSZ composite electrode for solid oxide fuel cells (SOFCs) cathode application has been investigated for its oxy- gen reduction reaction (ORR) performance. The composition and sintering temperature of LSM–ScSZ were controlled to determine the optimized microstructure of the LSM–ScSZ electrode layer, considering its length of triple-phase boundaries (TPBs), and transfer of oxygen for cathode reaction. The electrochemical impedance spectroscopy (EIS) method with an equivalent circuit model was introduced to characterize the specifi c impedance of each sample. The results demonstrated that volume ratio of LSM:ScSZ = 6:4 sintered at 1200 °C sample showed the lowest total impedance of 0.031 Ω cm 2 at 900 °C operating temperature, compensating slightly increased high-frequency impedance ( R HF ) of TPBs region with drastically improved the active surface of LSM area and their connectivity, which correspond to middle- and low-frequency impedance ( R MF and R LF ) value, respectively. This study suggests an integrated approach in the development of the SOFCs cathode design with the proper compositional ratio and sintering process via using commercial materials.
Synergistically Enhanced Oxygen Evolution Catalysis with Surface Modified Halloysite Nanotube
Hyeongwon Jeong,Bharat Sharma,Jae-ha Myung The Korean Electrochemical Society 2023 Journal of electrochemical science and technology Vol.14 No.1
Synergistically increased oxygen evolution reaction (OER) of manganese oxide (MnO<sub>2</sub>) catalyst is introduced with surface-modified halloysite nanotube (Fe<sub>3</sub>O<sub>4</sub>-HNTs) structure. The flake shaped MnO<sub>2</sub> catalyst is attached on the nanotube template (Fe<sub>3</sub>O<sub>4</sub>-HNTs) by series of wet chemical and hydrothermal method. The strong interaction between MnO<sub>2</sub> and Fe<sub>3</sub>O<sub>4</sub>-HNTs maximized active surface area and inter-connectivity for festinate charge transfer reaction for OER. The synergistical effect between Fe<sub>3</sub>O<sub>4</sub> layer and MnO<sub>2</sub> catalyst enhance the Mn<sup>3+</sup>/Mn<sup>4+</sup> ratio by partial replacement of Mn ions with Fe. The relatively increased Mn<sup>3+</sup>/Mn<sup>4+</sup> ratio on MnO<sub>2</sub>@FHNTs induced 𝜎<sup>*</sup> orbital (e<sub>g</sub>) occupation close to single electron, improving the OER performances. The MnO<sub>2</sub>@FHNTs catalyst exhibited the reduced overpotential of 0.42 V (E vs. RHE) at 10 mA/cm<sup>2</sup> and Tafel slope of (99 mV/dec), compared with that of MnO<sub>2</sub> with unmodified HNTs (0.65 V, 219 mV/dec) and pristine MnO<sub>2</sub> (0.53 V, 205 mV/dec). The present study provides simple and innovative method to fabricate nano fiberized OER catalyst for a broad application of energy conversion and storage systems.
기체 중심 동축형 분사기의 접선방향 유입구 지름 변화에 따른 액체 가진 연구
오석일 ( Sukil Oh ),박구정 ( Gujeong Park ),김성주 ( Seongju Kim ),이형원 ( Hyeongwon Lee ),윤영빈 ( Youngbin Yoon ),최정열 ( Jeong-yeol Choi ) 한국액체미립화학회 2017 한국액체미립화학회지 Vol.22 No.2
It is important to study on the combustion instability to develop liquid rocket engines for preventing lower combustion effi-ciency and destruction of combustion chamber. There are many researches on simplex injector with liquid pulsation to solve this problem. In real rocket engine system, however, they use coaxial injectors. Therefore, research on coaxial injector with liquid pulsation is essential. In this study, we investigate dynamic characteristics of gas centered swirl coaxial injector varying tangential inlet diameter. A mechanical pulsator was used to generate an excitation in the liquid flow, and the response char-acteristics of the injector were confirmed. As tangential inlet diameter increased, mass flow rates increased and spray angle decreased. As tangential inlet diamter decreased, gain decreased because the pressure fluctuation in the injector manifold rarely passed through the inlet. Additionally, it was confirmed that a sufficiently small tangential inlet served as a damper.
( Hye-jin Ahn ),( Jong-gil Seo ),( In-hye Kang ),( Hyeongwon Choi ),( Youngsook Son ),( Kyung Sook Kim ),( Ki-heon Jeong ),( Min Kyung Shin ) 대한피부과학회 2017 대한피부과학회 학술발표대회집 Vol.69 No.2
Background: Sodium lauryl sulfate (SLS) is a common detergent known to cause inflammatory reactions in skin. Cutaneous allergic inflammation can be modulated by neurotransmitters of sensory nerve fibers, such as substance P (SP) and calcitonin gene-related peptides. Objectives: We investigated the viability and cell-cell adhesion in SLS-treated human keratinocytes under pretreatment, co-treatment, and posttreatment with SP. Methods: Real-time PCR was performed 24 h after SLS treatment to determine the inflammatory responses in human keratinocytes treated with 100nM SP. SP decreased both IL-1β and TNF-α mRNA expression in this study. Next, we examined actin filaments and its related protein E-cadherin, which is an important junctional protein in epithelial cells. Results: At low SLS doses (2.5~10μM), cytotoxicity was reduced in SP pretreatment (approximately 10%) and SP co-treatment(approximately 5%). However, no significant changes were detected when normal human keratinocytes (NHKs) were treated with SP after the SLS-mediated toxicity, suggesting that SP pretreatment may have a protective effect against SLS-induced irritation. SP-treated cells showed organized actin filaments and increased expression of E-cadherin. These results suggest that SP could strengthen cell-cell junctions by increasing the expression of junctional components under simultaneous treatment with SLS. Conclusion: We suggest that low dose of SP has protective effect against the SLS-induce