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Use of various MgO resources for high-purity Mg metal production through molten salt electrolysis and vacuum distillation

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Journal of Magnesium and Alloys 2023年第2期11卷 562-579页

作者： Hyeong-Jun Jeoung Tae-Hyuk Lee youngjae kim Jin-Young Lee Young Min kim Toru HOkabe Kyung-Woo Yi Jungshin Kang Korea Institute of Geoscience and Mineral Resources 124 Gwahak-ro Yuseong-guDaejeon 34132South Korea Department of Materials Science and Engineering Seoul National University1 Gwanak-roGwanak-guSeoul 08826South Korea Department of Resources Engineering University of Science and Technology217 Gajeong-ro Yuseong-guDaejeon 34113South Korea Korea Institute of Materials Science 797 Changwondae-roSeongsan-guChangwonGyeongnam 51508South Korea Institute of Industrial Science The University of Tokyo4-6-1 KomabaMeguro-kuTokyo 153-8505Japan School of Materials Science and Engineering Pusan National University2 Busandaehak-roGeumjeong-guBusan 44241South Korea

A green and effective electrolytic process was developed to produce high-purity Mg metal using primary and secondary resources containing Mg O as a feedstock. The electrolysis of various Mg O resources was conducted using a Cu cathode in MgF2– LiF – KCl molten salt at 1043 K by applying an average current of 1.44 A for 12.5 h. The electrolysis of calcined North Korean magnesite and seawater Mg O clinker yielded Mg alloys of MgCu2and(Cu) phases with current efficiencies of 89.6–92.4%. The electrolysis of oxidized Mg O-C refractory brick, aged ferronickel slag, and ferronickel slag yielded Mg alloys of MgCu2and(Cu) phases with current efficiencies of 59.3–92.3%. The vacuum distillation of Mg alloys obtained was conducted at 1300 K for 10 h to produce high-purity Mg metal. After vacuum distillation, Mg metal with a purity of above 99.994% was obtained. Therefore, this study demonstrates the feasibility of the production of high-purity Mg metal from various Mg O resources using a novel electrolytic process with a Cu cathode, followed by vacuum distillation.

关键词： High-purity magnesium Magnesium oxide resources Electrolytic process Metal cathode Vacuum distillation

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Time-resolved photoemission of infinitely periodic atomic arrangements:correlation-dressed excited states of solids

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npj Computational Materials 2020年第1期6卷 548-557页

作者： youngjae kim JaeDong Lee Department of Emerging Materials Science DGISTDaegu 42988Korea

A theory of the time-resolved photoemission spectroscopy(TRPES)is developed,which enables to explore the real-time electron dynamics of infinitely periodic crystalline *** the strongly correlated electron systems NiO and CuO,the early-stage dynamics of the valence band edge are found to be sharply contrasted between those in the spectra of *** provides a new dynamical insight to the Zaanen–Sawatzky–Allen(ZSA)classification scheme of correlated insulators and makes us assert that NiO dynamically behaves like the Mott–Hubbard insulator(MHI)and CuO like the charge transfer insulator(CTI).In the two-dimensional carbon layer graphene,the real-time electron dynamics of quantum-phase-dressed excited states,i.e.,due to the Berry phase and the pseudospin correlation,are investigated in an unprecedented way through the time-resolved angle-resolved photoemission spectroscopy(TR-ARPES).In particular,the dephasing dynamics of optically doped electrons and holes in the massless Dirac band,accompanying a field-induced gliding of the Dirac cone,are discovered.

关键词： resolved infinitely excited

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A Temporal Locality-Aware Page-Mapped Flash Translation Layer

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Journal of Computer Science & Technology 2013年第6期28卷 1025-1044页

作者： youngjae kim Aayush Gupta Bhuvan Urgaonkar National Center for Computational Sciences Oak Ridge National Laboratory IBM Almaden Research Center ACM IEEE Department of Computer Science and Engineering Pennsylvania State UniversityUniversity Park

The poor performance of random writes has been a cause of major concern which needs to be addressed to better utilize the potential of flash in enterprise-scale environments. We examine one of the important causes of this poor performance： the design of the flash translation layer （FTL） which performs the virtual-to-physical address translations and hides the erase-before-write characteristics of flash. We propose a complete paradigm shift in the design of the core FTL engine from the existing techniques with our Demand-Based Flash Translation Layer （DFTL） which selectively caches page- level address mappings. Our experimental evaluation using FlashSim with realistic enterprise-scale workloads endorses the utility of DFTL in enterprise-scale storage systems by demonstrating： 1） improved performance, 2） reduced garbage collection overhead and 3） better overload behavior compared with hybrid FTL schemes which are the most popular implementation methods. For example, a predominantly random-write dominant I/O trace from an OLTP application running at a large financial institution shows a 78% improvement in average response time （due to a 3-fold reduction in operations of the garbage collector）, compared with the hybrid FTL scheme. Even for the well-known read-dominant TPC-H benchmark, for which DFTL introduces additional overheads, we improve system response time by 56%. Moreover, interestingly, when write-back cache on DFTL-based SSD is enabled, DFTL even outperforms the page-based FTL scheme, improving their response time by 72% in Financial trace.

关键词： flash memory flash translation layer storage system

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N, P co-doped 3D porous carbon with self-assembled morphological control via template-free method for potassiumion battery anodes

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Rare Metals 2024年第9期43卷 4243-4252页

作者： Jeehoon Yu Dae Kyom kim Hong Geun Oh Seung-Keun Park youngjae Yoo Department of Advanced Materials Engineering Chung-Ang University

The larger ionic radius of potassium ions than that of lithium ions significantly limits the accomplishment of rapid diffusion kinetics in graphite electrodes for potassium-ion batteries （PIBs）,resulting in comparatively poor rate performance and cycle ***,we report a high-rate performance and cycling stability amorphous carbon electrode achieved through nitrogen and phosphorous *** as-prepared N,P co-doped carbon electrodes have distinct 3D structures with large surface areas,hierarchical pore architectures,and increased interlayer spaces resulting from the direct pyrolysis of supramolecular self-assembled aggregates without *** obtained electrode N3P1 exhibits a reversible specific capacity of 258 m Ah·g-1at a current density of 0.1A·g-1and a good long-term cycle performance (96.1%capacity retention after 800 cycles at 0.5 A·g-1).Kinetic investigations show that the N3P1 electrode with the welldeveloped porous structure and large number of surface defects exhibits capacitive-driven behavior at all scan rates,which may be attributed by N and P ***-situ transmission electron microscopy analyses in the fully discharged and charged states demonstrate structural stability and reversibility owing to the expanded interlayer *** suggested synthesis approach is simple and effective for producing heteroatom-doped carbon materials for PIBs and other advanced electrochemical energy storage materials.

关键词： 3D porous structures Amorphous carbons Nitrogen and phosphorous co-doping Potassium-ion batteries

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Probing the upper band gap of atomic rhenium disulfide layers

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Light(Science & Applications) 2018年第1期7卷 163-173页

作者： Krishna P.Dhakal Hyunmin kim Seonwoo Lee youngjae kim JaeDong Lee Jong-Hyun Ahn School of Electrical and Electronic Engineering Yonsei UniversitySeoul 03722Republic of Korea Companion Diagnostics&Medical Technology Research Group DGISTDaegu 42988Republic of Korea Department of Emerging Materials Science DGISTDaegu 42988Republic of Korea

Here,we investigate the ultrafast carrier dynamics and electronic states of exfoliated ReS2 films using time-resolved second harmonic generation(TSHG)microscopy and density functional theory(DFT)*** second harmonic generation(SHG)of layers with various thicknesses is probed using a 1.19-eV *** to~13 nm,a gradual increment is observed,followed by a decrease caused by bulk interferometric light *** addition of a pump pulse tuned to the exciton band gap(1.57 eV)creates a decay-to-rise TSHG profile as a function of the probe *** power and thickness dependencies indicate that the electron–hole recombination is mediated by defects and *** two photon absorptions of 2.38 eV in the excited state that are induced by pumping from 1.57 to 1.72 eV are restricted because these transitions highly correlate with the forbidden d–d intrasubshell orbital ***,the combined usage of a frequency-doubled pump(2.38 eV)with wavelength-variant SHG probes(2.60–2.82 eV)allows us to vividly monitor the variations in TSHG profiles from decay-to-rise to rise-to-decay,which imply the existence of an additional electron absorption state(s-orbital)at an approximate distance of 5.05 eV from the highest occupied molecular orbital *** observation was critically examined by considering the allowance of each electronic transition and a small upper band gap(~0.5 eV)using modified DFT calculations.

关键词： pump pumping transitions

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Efficient thermal management and all-season energy harvesting using adaptive radiative cooling and a thermoelectric power generator

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能源化学:英文版 2023年第9期84卷 496-501页

作者： Chanil Park Woohwa Lee Choyeon Park Sungmin Park Jaeho Lee Yong Seok kim youngjae Yoo Advanced Materials Division Korea Research Institute of Chemical Technology(KRICT)Daejeon 34114Republic of Korea Department of Mechanical and Aerospace Engineering University of CaliforniaIrvineCA 92617United States Department of Advanced Materials Engineering Chung-Ang UniversityAnseong 17546Republic of Korea

Passive daytime radiative cooling(PDRC) is useful for thermal management because it allows an object to emit terrestrial heat into space without the use of additional *** produce sub-ambient temperatures under direct sunlight,PDRC materials are designed to reduce their absorption of solar energy and to enhance their long-wavelength infrared(LWIR) *** recent years,many photonic structures and polymer composites have been studied to improve the cooling system of ***,in cold weather(i.e. during winter in cold climates),buildings need to be kept warm rather than cooled due to heat *** overcome this limitation,temperature-responsive radiative cooling is a promising *** the present study,adaptive radiative cooling(ARC) film fabricated from a polydimethylsiloxane/hollow SiO_(2) microsphere/thermochromic pigment composite was *** found that the ARC film absorbed solar radiation under cold conditions while exhibiting radiative cooling at ambient temperatures above 40℃.Thus,in outdoor experiments,the ARC film achieved sub-ambient temperatures and had a theoretical cooling power of 63.2 W/m~2 in hot *** also demonstrated that radiative cooling with an energy harvesting system could be used to improve the energy management of buildings,with the thermoelectric module continuously generating output power using the ARC ***,we believe that our proposed ARC film can be employed for efficient thermal management of buildings and all-season energy harvesting in the near future.

关键词： Thermal management Daytime radiative cooling Temperature-adaptive film Thermoelectric device Energy harvesting

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End-of-life batteries management and material flow analysis in South Korea

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Frontiers of Environmental Science & Engineering 2018年第3期12卷 55-67页

作者： Hyunhee kim Yong-Chul Jang Yeonjung Hwang youngjae Ko Hyunmyeong Yun Department of Environmental Engineering Chungnam National University Daejeon 34134 South Korea Waste to Energy Research Division Environmental Resources Research Department National Institute of Environmental Research Incheon 22689 South Korea Daejeon Green Environment Center Daejeon 34134 South Korea

Consumers increasingly have worn-out batteries as electrical and electronic equipment with new technical developments are introduced into the market and quickly replace older models. As a result, large amounts of end-of-life （EOL） or waste batteries are generated. Such batteries may contain a variety of materials that includes valuable resources as well as toxic elements. Thus, the proper recycling and management of batteries is very important from the perspective of resource conservation and environmental effect. The collection and recycling of EOL batteries is relatively low in South Korea compared to other countries, although an extended producer responsibility （EPR） policy was adopted for battery recycling in 2003. In this study, the management and material flow of EOL batteries is presented to determine potential problems and quantitative flow, based on literature review, site visits to battery recycling facilities, and interviews with experts in the Korea Battery Recycling Association （KBRA）, manufacturers, and regulators in government. The results show that approximately 558 tons of manganese-alkaline batteries, the largest fraction among recycling target items, was disposed in landfills or incinerators in 2015, while approximately 2,000 tons of batteries were recovered at a recycling facility by simple sorting and crushing processes. By raising environmental awareness, more diverse and effective collection systems could be established for consumers to easily dispose of EOL batteries in many places. Producers, retailers and distributors in South Korea should also play an important role in the collection of EOL batteries from consumers. Lithium-ion batteries from many electronic devices must be included in the EPR system for resource recovery.

关键词： End-of-life battery Recycling Material flow analysis (MFA)Extended producer responsibility (EPR)Resource recovery

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Biochemical Characterization of Soluble Acid and Alkaline Invertases from Shoots of Etiolated Pea Seedlings

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Journal of Integrative Plant Biology 2010年第6期52卷 536-548页

作者： Donggiun kim So Yun Park youngjae Chung Jongbum Park Sukchan Lee Taek-Kyun Lee Department of Biological Science Silla University South Sea Environment Research Department Korea Ocean Research and Development Institute Department of Life Science and Biotechnology Shin Gyeong University Department of Genetic Engineering Sungkyunkwan University

Soluble invertase was purified from pea （Pisum sativum L.） by sequential procedures entailing ammonium sulfate precipitation, DEAE-Sepharose column, Con-A- and Green 19-Sepharose affinity columns, hydroxyapatite column, ultra-filtration, and Sephacryl 300 gel filtration. The purified soluble acid （SAC） and alkaline （SALK） invertases had a pH optimum of 5.3 and 7.3, respectively. The temperature optimum of two invertases was 37 ℃. The effects of various concentrations of Tris-HCI, HgCI2, and CuSO4 on the activities of the two purified enzymes were examined. Tris-HCI and HgCI2 did not affect SAC activity, whereas 10 mM Tris-HCI and 0.05 mM HgCI2 inhibited SALK activity by about 50%. SAC and SALK were inhibited by 4.8 mM and 0.6 mM CuSO4 by 50%, respectively. The enzymes display typical hyperbolic saturation kinetics for sucrose hydrolysis. The Kms of SAC and SALK were determined to be 1.8 and 38.6 mM, respectively. The molecular masses of SAC shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting were 22 kDa and 45 kDa. The molecular mass of SALK was 30 kDa. Iso-electric points of the SAC and SALK were estimated to be about pH 7.0 and pH 5.7, respectively.

关键词： SAC Biochemical Characterization of Soluble Acid and Alkaline Invertases from Shoots of Etiolated Pea Seedlings

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Monitoring biofouling based on aerobic respiration in reverse osmosis system

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Journal of Environmental Sciences 2019年第4期31卷 247-256页

作者： youngjae Yu Keun-Young Park Jaehyun Jung Wonjung Song Jaehyeok kim Junhee Ryu Harshad Lade Jihyang Kweon Department of Environmental Engineering Konkuk University Department of Environment and Energy Sejong University Department of Laboratory Medicine Hallym University Medical Center

A monitoring method of biofouling in reverse osmosis(RO) system was proposed based on the fluorescent signal of resorufin, which is reduced by nicotinamide adenine dinucleotide released from viable cells during aerobic respiration. The fluorescent signal of resorufin reduced by planktonic cells and microorganisms of biofilm showed linearity, indicating its feasibility to monitor biofouling in a RO system. For the application of the method to the lab-scale RO system, the injection concentration of resazurin and the injection flow rate were optimized. Biofilm on RO membranes continuously operated in a lab-scale RO system was estimated by resorufin fluorescence under optimized detection condition. As a result,resorufin fluorescence on RO membrane showed a significant increase in which the permeability of RO system decreased by 30.48%. Moreover, it represented the development of biofilm as much as conventional biofilm parameters such as adenosine triphosphate,extracellular polymeric substances, and biofilm thickness. The proposed method could be used as a sensitive and low-cost technology to monitor biofouling without autopsy of membranes.

关键词： On-site monitoring Biofilm Aerobic respiration Resazurin reduction mechanism Resorufin fluorescence

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