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Depolarization mitigated in ferroelectric Hf_(0.5)Zr_(0.5)O_(2)ultrathin films(<5 nm)on Si substrate by interface engineering

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Journal of Advanced Ceramics 2024年第3期13卷 282-292页

作者： Se Hyun Kim Younghwan Lee Dong Hyun Lee Geun Hyeong Park Hyun woo Jeong Kun Yang yong Hyeon Cho Young yong Kim Min Hyuk Park Department of Materials Science and Engineering College of EngineeringSeoul National UniversitySeoul 08826Republic of Korea Research Institute of Advanced Materials College of EngineeringSeoul National UniversitySeoul 08826Republic of Korea Inter-university Semiconductor Research Center College of EngineeringSeoul National UniversitySeoul 08826Republic of Korea Pohang Accelerator Laboratory Pohang University of Science&TechnologyPohang 790784Republic of Korea

(Hf,Zr)O_(2)offers considerable potential for next-generation semiconductor devices owing to its nonvolatile spontaneous polarization at the ***,scaling this material to sub-5 nm thickness poses several challenges,including the formation of an interfacial layer and high trap *** particular,a low-k SiO_(2)interfacial layer is naturally formed when(Hf,Zr)O_(2)films are directly grown on a Si substrate,leading to high depolarization fields and rapid reduction of the remanent *** address these issues,we conducted a study to significantly improve ferroelectricity and switching endurance of(Hf,Zr)O_(2)films with sub-5 nm thicknesses by inserting a TiO_(2)interfacial *** deposition of a Ti film prior to Hf_(0.5)Zr_(0.5)O_(2)film deposition resulted in a high-k TiO_(2)interfacial layer and prevented the direct contact of Hf_(0.5)Zr_(0.5)O_(2)with *** findings show that the high-k TiO_(2)interfacial layer can reduce the SiO_(2)/Si interface trap density and the depolarization field,resulting in a switchable polarization of 60.2μC/cm^(2)for a 5 nm thick Hf_(0.5)Zr_(0.5)O_(2)***,we propose that inserting a high-k TiO_(2)interfacial layer between the Hf_(0.5)Zr_(0.5)O_(2)film and the Si substrate may offer a promising solution to enhancing the ferroelectricity and reliability of(Hf,Zr)O_(2)grown on the Si substrate and can pave the way for next-generation semiconductor devices with improved performance.

关键词： ferroelectric charge trapping hafnia depolarization

Tailoring local structures of atomically dispersed copper sites for highly selective CO_(2) electroreduction

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Carbon Energy 2024年第4期6卷 79-90页

作者： Kyung‐Jong Noh Byoung Joon Park Ying Wang Yejung Choi Sang‐Hoon You yong‐Tae Kim Kug‐Seung Lee Jeong woo Han Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)PohangGyeongbukRepublic of Korea Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)PohangGyeongbukRepublic of Korea Pohang Accelerator Laboratory(PAL) Beamline DivisionPohangGyeongbukRepublic of Korea

Atomically‐dispersed copper sites coordinated with nitrogen‐doped carbon(Cu–N–C)can provide novel possibilities to enable highly selective and active electrochemical CO_(2) reduction ***,the construction of optimal local electronic structures for nitrogen‐coordinated Cu sites(Cu–N_(4))on carbon remains ***,we synthesized the Cu–N–C catalysts with atomically‐dispersed edge‐hosted Cu–N_(4) sites(Cu–N_(4)C_(8))located in a micropore between two graphitic sheets via a facile method to control the concentration of metal ***‐hosted Cu–N_(4)C_(8) catalysts outperformed the previously reported M–N–C catalysts for CO_(2)‐to‐CO conversion,achieving a maximum CO Faradaic efficiency(FECO)of 96%,a CO current density of–8.97 mA cm^(–2) at–0.8 V versus reversible hydrogen electrode(RHE),and over FECO of 90%from–0.6 to–1.0 V versus *** studies revealed that the micropore of the graphitic layer in edge‐hosted Cu–N_(4)C_(8) sites causes the d‐orbital energy level of the Cu atom to shift upward,which in return decreases the occupancy of antibonding states in the*COOH *** research suggests new insights into tailoring the locally coordinated structure of the electrocatalyst at the atomic scale to achieve highly selective electrocatalytic reactions.

关键词： atomic local structure density functional theory electrochemical CO_(2)reduction metal nitrogen‐doped carbon single‐atom catalyst

Performance of pulsed plasma thruster at low discharge energy

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Plasma Science and Technology 2024年第4期26卷 122-132页

作者：李鸿俊林泽豪胡浩俊吴文东陈爱虹杜德扬 Department of Physics Faculty of ScienceUniversity of MalayaKuala Lumpur 50603Malaysia Faculty of Engineering The University of Nottingham Malaysia CampusSemenyih 43500Malaysia Faculty of Engineering Multimedia UniversityCyberjaya 63100Malaysia

As the size of satellites scales down, low-power and compact propulsion systems such as the pulsed plasma thruster(PPT) are needed for stabilizing these miniature satellites in orbit. Most PPT systems are operated at 2 J or more of discharge energy. In this work, the performance of a PPT with a side-fed, tongue-flared electrode configuration operated within a lower discharge energy range of 0.5-2.5 J has been investigated. Ablation and charring of the polytetrafluoroethylene propellant surface were analyzed through field-effect scanning electron microscopy imaging and energy-dispersive X-ray spectroscopy. When the discharge energy fell below 2 J, inconsistencies occurred in the specific impulse and the thrust efficiency due to the measurement of the low mass bit. At energy ≥2 J, the performance parameters are compared with other PPT systems of similar configuration and discussed in depth.

关键词： pulsed plasma thruster low discharge energy performance parameters

An easily misdiagnosed and rare cause of traumatic back pain: bilateral renal infarction caused by traumatic bilateral renal artery dissection

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World Journal of Emergency Medicine 2023年第2期14卷 155-157页

作者： woo sung Choi sung Youl Hyun Jae-Hyug woo Jung Han Hwang yong Su Lim Department of Emergency and Critical Care Medicine Gachon University Gil Medical CenterGachon University College of MedicineIncheon 21565Republic of Korea Department of Traumatology Gachon University Gil Medical CenterGachon University College of MedicineIncheon 21565Republic of Korea Department of Interventional Radiology Gachon University Gil Medical CenterGachon University College of MedicineIncheon 21565Republic of Korea

Dear editor,The incidence of renal infarction in patients admitted to the emergency department(ED) is approximately 0.004%.[1]Among patients with renal infarction, bilateral renal involvement has been reported in 28.6... 详细信息

关键词： traumatic infarction admitted

High efficiency and stable solid-state fiber dye-sensitized solar cells obtained using TiO_(2) photoanodes enhanced with metal organic frameworks

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Journal of Energy Chemistry 2022年第4期31卷 458-466页

作者： Jae Ho Kim Hyun woo Park sung-Jun Koo Daseul Lee Eunyeong Cho yong-Ki Kim Myunghun Shin Jin woo Choi Hee Jung Lee Myungkwan Song Department of Energy and Electronic Material Korea Institute of Materials Science(KIMS)797 Changwon-daeroSungsan-guChangwonGyeongsangnam-do 51508Republic of Korea Composites Research Division Korea Institute of Materials Science(KIMS)797 Changwon-daeroSungsan-GuChangwonGyeongsangnam-do 51508Republic of Korea School of Electronics and Information Engineering Korea Aerospace UniversityGoyang-cityGyeonggi-do 10540Republic of Korea

Solid-state fiber dye-sensitized solar cells(SS-FDSSCs) have been the subject of intensive attention and development in recent years. Although this field is only in its infancy, metal–organic frameworks(MOFs) are one such material that has been utilized to further improve the power conversion efficiency of solar cells. In this study, MOF-integrated DSSCs were shown to have potential in the development of solar cell devices with efficiency comparable to or better than that of conventional solar cells. The power conversion efficiency(PCE) of SS-FDSSCs was improved by embedding MOF-801 into a mesoporous-TiO_(2)(mp-TiO_(2)) layer, which was used as a photoanode in SS-FDSSCs, which are inherently flexible. The PCE of the MOF-integrated SS-FDSSCs was 6.50%, which is comparable to that of the reference devices(4.19%).The MOF-801 enhanced SS-FDSSCs decreased the series resistance(R_(s)) value, resulting in effective electron extraction with improved short-circuit current density(J_(SC)), while also increasing the shunt resistance(R_(sh)) value to prevent the recombination of photo-induced electrons. The result is an improved fill factor and, consequently, a higher value for the PCE.

关键词： Photoanode Metal organic frameworks Solid-state electrolyte Dye-sensitized solar cells Fiber-shaped solar cells

Effect of silicon carbide-based iron catalyst on reactor optimization for non-oxidative direct conversion of methane

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Journal of Energy Chemistry 2023年第6期81卷 519-532,I0012页

作者： Eun-hae Sim sung woo Lee Jin Ju Lee Seung Ju Han Jung Ho Shin Gracia Lee sungrok Ko Kwan-Young Lee yong Tae Kim C1 Gas&Carbon Convergent Research Center Korea Research Institute of Chemical TechnologyDaejeon 34114Republic of Korea Department of Chemical and Biological Engineering Korea University145 Anam-roSeoul 02841Republic of Korea Department of Chemical and Biomolecular Engineering Yonsei University50 Yonsei-roSeoul 03722Republic of Korea Chemical Data-Driven Research Center Korea Research Institute of Chemical TechnologyDaejeon 34114Republic of Korea Prospective Tech.Exploring Section Basic Chemical R&D centerLottechemical Corp.Daejeon 34059Republic of Korea Department of Advanced Materials and Chemical Engineering University of Science and Technology(UST)Gajeong-dongYuseongDaejeon 34113Republic of Korea

The conversion of methane to olefins,aromatics,and hydrogen(MTOAH)can be used to stably obtain hydrocarbons when the effect of the catalytic surface is optimized from the reaction engineering *** this study,Fe/Si C catalysts were packed into a quartz tube *** catalytic surfaces of Si C and the impregnated Fe species decreased the apparent activation energies(E_a)of methane consumption in the blank reactor between 965 and 1020℃.Consequently,the hydrocarbon yield increased by 2.4times at 1020℃.Based on the model reactions of ethane,ethylene,and acetylene mixed with hydrogen in the range of 500-1020℃,an excess amount of Fe in the reactor favored the C-C coupling reaction over the selective hydrogenation of acetylene;consequently,coke formation was favored over the hydrogenation *** gas-phase reactions and catalyst properties were optimized to increase hydrocarbon yields while reducing coke *** 0.2Fe catalyst-packed reactor(0.26 wt%Fe)resulted in a hydrocarbon yield of 7.1%and a coke selectivity of<2%when the ratio of the void space of the postcatalyst zone to the catalyst space was adjusted to be≥*** on these findings,the facile approach of decoupling the reaction zone between the catalyst surface and the gas-phase reaction can provide insights into catalytic reactor design,thereby facilitating the scale-up from the laboratory to the commercial scale.

关键词： Non-oxidative methane conversion Ethylene Aromatic Methane pyrolysis Fe/SiC Coke resistance Catalytic reactor

PUB22 and PUB23 U-box E3 ubiquitin ligases negatively regulate 26S proteasome activity under proteotoxic stress conditions

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Journal of Integrative Plant Biology 2022年第3期64卷 625-631页

作者： Min yong Ahn Dong Hye Seo woo Taek Kim Department of Systems Biology Division of Life ScienceYonsei UniversitySeoul 03722Korea Institute of Life Science and Biotechnology Yonsei UniversitySeoul 03722Korea

The mechanism regulating proteasomal activity under proteotoxic stress conditions remains ***,we showed that arsenite-induced proteotoxic stress resulted in upregulation of Arabidopsis homologous PUB22 and PUB23 U-boxE3 ubiquitin ligases and that pub22 pub23 double mutants displayed arsenite-insensitive seed germination and root growth ***22/PUB23 downregulated 26 S proteasome activity by promoting the dissociation of the 19 S regulatory particle from the holo-proteasome complex,resulting in intracellular accumulation of UbG76 VGFP,an artificial substrate of the proteasome complex,and insoluble poly-ubiquitinated *** results suggest that PUB22/PUB23 play a critical role in arsenite-induced proteotoxic stress response via negative regulation of 26 S proteasome integrity.

关键词： Arabidopsis thaliana proteotoxic stress sodium arsenite U-box E3 ligases PUB22/23 26S proteasome complex

Superior electrocatalytic negative electrode with tailored nitrogen functional group for vanadium redox flow battery

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Journal of Energy Chemistry 2023年第3期78卷 148-157,I0005页

作者： Min Gu Kang wook Ahn Joonhee Kang Shin Ae Song Kiyoung Kim Ju Young woo yong-Cheol Jeong Bonwook Koo Dae Soo Jung sung Nam Lim Micro/Nano Scale Manufacturing Group Korea Institute of Industrial Technology143 HanggaulroSangrok-guAnsan-siGyeonggi-do 15588Republic of Korea Department of Energy Systems Engineering Soonchunhyang University22 Soonchunhyang-roShinchang-myeonAsan-siChungcheongnam-do 31538Republic of Korea Department of Nanoenergy Engineering Pusan National UniversityBusan 46241Republic of Korea Department of Nano Fusion Technology Pusan National UniversityBusan 46241Republic of Korea Energy Storage Materials Center Energy&Environmental DivisionKorea Institute of Ceramic Engineering&Technology(KICET)101 Soho-roJinju-siGyeongsangnam-doRepublic of Korea

Development of electrodes with high electrocatalytic activity and stability is essential for solving problems that still restrict the extensive application of vanadium redox flow batteries(VRFBs).Here,we designed a novel negative electrode with superior electrocatalytic activity by tailoring nitrogen functional groups,such as newly formed nitro and pyridinic-N transformed to pyridonic-N,from the prenitrogen-doped *** was experimentally confirmed that an electrode with pyridonic-N and nitro fuctional groups(tailored nitrogen-doped graphite felt,TNGF) has superior electrocatalytic acivity with enhanced electron and mass *** functional theory calulations demonstrated the pyridonic-N and nitro functional groups promoted the adsorption,charge transfer,and bond formation with the vanadium species,which is consistent with expermental *** addition,the V2+/V3+redox reaction mechanism on pyridonic-N and nitro functional groups was estabilised based on density functional theory(DFT) *** TNGF was applied to a VRFB,it enabled enhanced-electrolyte utilization and energy efficiencies(EE) of 57.9% and 64.6%,respectively,at a current density of 250 mA cm^(-2).These results are 18.6% and 8.9% higher than those of VRFB with electrode containing graphitic-N and pyridinicN ***,TNGF-based VRFB still operated with an EE of 59% at a high current density of300 mA cm^(-2).The TNGF-based VRFB exhibited stable cycling performance without noticeable decay of EE over 450 charge-discharge cycles at a current density of 250 mA cm^(-2).The results of this study suggest that introducing pyridonic-N and nitro groups on the electrode is effective for improving the electrochemical performance of VRFBs.

关键词： Tailored nitrogen functional group Pyridonic-N Nitro Negative electrode Density functional theory Vanadium redoxﬂow batteries

Segmented tomographic evaluation of structural degradation of carbon support in proton exchange membrane fuel cells

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Journal of Energy Chemistry 2022年第11期31卷 359-367,I0010页

作者： Jung A.Hong Min-Hyoung Jung sung yong Cho Eun-Byeol Park Daehee Yang Young-Hoon Kim Sang-Hyeok Yang woo-sung Jang Jae Hyuck Jang Hyo June Lee sungchul Lee Hu Young Jeong Young-Min Kim Department of Energy Science Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Fuel Cell Core Parts Development Cell Hyundai Mobis Co.Ltd.Uiwang 16082Republic of Korea Electron Microscopy&Spectroscopy Team Korea Basic Science Institute(KBSI)Daejeon 34133Republic of Korea Graduate School of Semiconductor Materials and Devices Engineering Ulsan National Institute of Science and Technology(UNIST)Ulsan 44919Republic of Korea

The variation of the three-dimensional(3D)structure of the membrane electrode of a fuel cell during proton exchange cycling involves the corrosion/compaction of the carbon *** increasing degradation of the carbon structure continuously reduces the electrocatalytic performance of proton exchange membrane fuel cells(PEM-FCs).This phenomenon can be explained by performing 3D tomographic analysis at the ***,conventional tomographic approaches which present limited experimental feasibility,cannot perform such evaluation and have not provided sufficient structural information with statistical significance thus ***,a reliable methodology is required for the 3D geometrical evaluation of the carbon ***,we propose a segmented tomographic approach which employs pore network analysis that enables the visualization of the geometrical parameters corresponding to the porous carbon structure at a high *** approach can be utilized to evaluate the 3D structural degradation of the porous carbon structure after cycling in terms of local surface area,pore size distribution,and their 3D *** geometrical parameters of the carbon body were demonstrated to be substantially reduced owing to the cycling-induced *** information enables a deeper understanding of the degradation phenomenon of carbon supports and can contribute to the development of stable PEM-FC electrodes.

关键词： Electron tomography Fuel cell Proton exchange membrane Membrane electrode assembly Carbon corrosion