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Formation Mechanism of chunky Graphite and Its Preventive Measures

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Journal of Materials Science & Technology 2008年第3期24卷 289-295页

作者： Hideo Nakae Sanghoon jung Ho-chul Shin Department of Materials Science and Engineering Waseda University National Institute of AIST corporate Res.and Dev.Div. Hyundai.Kia Motors

The formation mechanism of chunky graphite has been reviewed and studied. The study consisted of a unidirectional solidification method, a small droplet method and a furnace cooling method. Four kinds of iron samples were prepared, namely, the pure Fe-c, Fe-c-S, Fe-c-ce and Fe-c-Si-ce alloys, and three kinds of nickel samples, namely the Ni-c, Ni-c-S and Ni-c-Mg alloys. The results of the unidirectional solidification of the Ni-c alloys showed that spheroidal graphite is not observed in the continuous solidified region, in which only flake-like graphite is observed, while spheroidal graphite is usually observed in the quenched liquid region. The existence of spheroidal graphite in the solidified phase is recognized only in the discontinuous growth mode of the Ni-c-Mg alloy solidified at 150 mm/h. This means that the spheroidal graphite is directly crystallized from the melt and entrapped by the flake-like chunky graphite that is formed by the continuous growth mode. In the small droplet method, a small piece of the Fe-c or Fe-c-ce sample was melted on a pure graphite plate then cooled at a different cooling rate in a He-3%H2 atmosphere. The graphite in the Fe-c-ce alloy is usually spherical. Nevertheless, the graphite morphology of the final solidified area changed from spherical to chunky and chunky to ledeburite with an increase in the cooling rate. This means that the chunky graphite is formed in the residual liquid region by the solidification into Fe-graphite system. The sample was cooled in a furnace, and the graphite morphology changes from spherical to chunky and chunky to ledeburite with the decrease in the Si content. These phenomena can be confirmed by the cooling curves of these samples.

关键词： chunky graphite Spheroidal graphite Solidification cooling curve

High-Throughput Pb Recycling for Perovskite Solar cells Using Biomimetic Whitlockite

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Energy & Environmental Materials 2023年第3期6卷 170-176页

作者： jung Sug Hong Hee jung kim chang Hwun Sohn Oh Yeong Gong Jin Hyuk choi kang Hee cho Gill Sang Han ki Tae Nam Hyun Suk jung Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Korea School of Advanced Materials Science and Engineering Sungkyunkwan UniversitySuwon 16419Korea

Pb contamination in aquatic environments causes severe pollution;therefore,harmless absorbents are *** this study,we report a novel synthesis of whitlockite(WH,ca_(18)Mg_(2)(HPO_(4))_(2)(PO_(4))_(12)),which is the second most abundant biomineral in human bone,and its application as a high-performing Pb^(2+)***(HAP)and WH are prepared via a simple precipitation *** Pb2+absorption performance and mechanism of the synthesized biominerals are investigated in aqueous solutions at neutral *** results demonstrate that WH exhibits an excellent Pb2+absorption capacity of 2339 mg g^(−1),which is 1.68 times higher than the recorded value for ***,the absorbed Pb^(2+) ions are recycled into high-purity PbI_(2).This is employed as a precursor for the fabrication of perovskite solar cells(PScs),resulting in a conversion efficiency of 19.00%comparable to that of commercial PbI2 powder(99.99%purity).Our approach provides an efficient way to remove Pb^(2+)ions from water and reuse them in the recycling of PScs.

关键词： Pb absorption Pb recycling perovskite solar cells water purification whitlockite

A rare combination injury of type III Monteggia fracture dislocation and ipsilateral epiphyseal fracture of distal radius in children. Is there a probability of missing the Monteggia component？

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chinese Journal of Traumatology 2015年第1期18卷 51-53页

作者： k.c. kapil Mani Arun Sigdel Anuj jung Rayamajhi Department of Orthopedics Civil Service Hospital Minbhawan Kathmandu Nepal Department of Anaesthesiology Civil Service Hospital Minbhawan Kathmandu Nepal

combined type III Monteggia fracture dislocation and ipsilateral distal radial epiphyseal fracture is a very rare injury. Because of difficulty in performing the proper clinical evaluation of a child in an acute injury state, one of the components of this combined injury may be missed. We report a ten- year-old male child with this kind of injury where the Monteggia lesion was initially missed at the emergency department. Later we found the combined epiphyseal fracture of distal radius and Monteggia lesion in the ipsilateral side of the same limb which was managed by closed reduction and k-wire fixation. Bony union as well as wrist and elbow motion was complete 3 months after surgical intervention.

关键词： Radius fracture Monteggia's fracture child

Microfluidic dual loops reactor for conducting a multistep reaction

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Frontiers of chemical Science and Engineering 2018年第2期12卷 239-246页

作者： Si Hyung Jin Jae-Hoon jung Seong-Geun Jeong Jongmin kim Tae jung Park chang-Soo Lee Department of chemical Engineering Chungnam National University Daejeon 34134 Korea Lotte chemical R&D center Daejeon 34110 Korea Department of chemistry Chung-Ang University Seoul 06974 Korea

Precise control of each individual reaction that constitutes a multistep reaction must be performed to obtain the desired reaction product efficiently. In this work, we present a microfluidic dual loops reactor that enables multistep reaction by integrating two identical loop reactors. Specifically, reactants A and B are synthesized in the first loop reactor and transferred to the second loop reactor to synthesize with reactant c to form the final product. These individual reactions have nano-liter volumes and are carded out in a stepwise manner in each reactor without any cross-contamination issue. To pre- cisely control the mixing efficiency in each loop reactor, we investigate the operating pressure and the operating frequency on the mixing valves for rotary mixing. This microfluidic dual loops reactor is integrated with several valves to realize the fully automated unit operation of a multistep reaction, such as metering the reactants, rotary mixing, transportation, and collecting the product. For proof of concept, cdSeZn nanopartieles are successfully synthesized in a microfluidic dual loops reactor through a fully automated mukistep reaction. Taking all of these features together, this microfluidic dual loops reactor is a general microfluidic screening platform that can synthesize various materials through a multistep reaction.

关键词： microfluidics multistep reaction rotary mixing nanoparticle

Porous Microspheres comprising coSe2 Nanorods coated with N-Doped Graphitic c and Polydopamine-Derived c as Anodes for Long-Lived Na-Ion Batteries

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Nano-Micro Letters 2022年第7期14卷 118-139页

作者： Jae Seob Lee Rakesh Saroha jung Sang cho Department of Engineering chemistry Chungbuk National UniversityCheongjuChungbuk 361-763Republic of Korea

Metal–organic framework-templated nitrogen-doped graphitic carbon(NGc)and polydopaminederived carbon(PDA-derived c)-double coated one-dimensional coSe_(2) nanorods supported highly porous threedimensional microspheres are introduced as anodes for excellent Na-ion batteries,particularly with long-lived cycle under carbonate-based electrolyte *** microspheres uniformly composed of ZIF-67 polyhedrons and polystyrene nanobeads(φ=40 nm)are synthesized using the facile spray pyrolysis technique,followed by the selenization process(P-coSe_(2)@NGc NR).Further,the PDA-derived c-coated microspheres are obtained using a solution-based coating approach and the subsequent carbonization process(P-coSe_(2)@PDA-c NR).The rational synthesis approach benefited from the synergistic effects of dual carbon coating,resulting in a highly conductive and porous nanostructure that could facilitate rapid diffusion of charge species along with efficient electrolyte infiltration and effectively channelize the volume ***,the prepared nanostructure exhibits extraordinary electrochemical performance,particularly the ultra-long cycle life *** instance,the advanced anode has a discharge capacity of 291(1000th cycle,average capacity decay of 0.017%)and 142 mAh g^(-1)(5000th cycle,average capacity decay of 0.011%)at a current density of 0.5 and 2.0 A g^(-1),respectively.

关键词： Spray pyrolysis Sodium-ion batteries cobalt selenide nanorods Porous microspheres Dual carbon coating

Sand-polished kapton film and aluminum as source of electron transfer triboelectric nanogenerator through vertical contact separation mode

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International Journal of Smart and Nano Materials 2020年第1期11卷 38-46页

作者： Ravi kumar cheedarala jung Il Song Research Institute of Mechatronics Department of Mechanical EngineeringChangwon National UniversityUichang-guChangwon CityS.Korea

contact electrification is a direct triboelectrification method for producing current through charge transfer when two different differentiated materials have brought into *** the first time,we developed a simple triboelectric nanogenerator(TENG)where the electronic charges were realized through contact separation mode between sand-polished kapton(SPk)and Al ***,we demonstrated the energetic interfacial contact between these surfaces and observed satisfactory output *** novel SPk-TENG produced 40 V and 2.8μA,of open-circuit voltages(V_(oc))and short-circuit currents(Isc)at 4 Hz,***,the SPk-TENG was dramatically increased up the performance of TENG,up to 40% of V_(oc) and 42% of I_(sc),with respect to the kapton film because the mobility of electrons is very high on the device surface compared to the other pristine kapton *** fabricated SPk-TENGs were good candidates for satisfying the need for alternative contact separation mode TENGs.

关键词： kapton contactelectrification k-Al TENG SPk-Al TENGs electron transfer mechanism

Disordered Structure and Reversible Phase Transformation from k-Birnessite to Zn-Buserite Enable High-Performance Aqueous Zinc-lon Batteries

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Energy & Environmental Materials 2024年第3期7卷 100-111页

作者： Nibagani Naresh Suyoon Eom Sang Jun Lee Su Hwan Jeong Ji-Won jung Young Hwa jung Joo-Hyung kim Department of Materials Engineering and convergence Technology Gyeongsang National University(GNU)Jinju 52828South Korea School of Material Science and Engineering(ceramic Engineering) Gyeongsang National University(GNU)Jinju 52828South Korea School of Materials Science and Engineering University of Ulsan(UOU)Ulsan 44776South Korea PLS-ⅡBeamline Division Pohang Accelerator Laboratory(PAL)Pohang 37673South Korea

The layeredδ-MnO_(2)(dMO)is an excellent cathode material for rechargeable aqueous zinc-ion batteries owing to its large interlayer distance(~0.7 nm),high capacity,and low cost;however,such cathodes suffer from structural degradation during the long-term cycling process,leading to capacity *** this study,a co-doped dMO composite with reduced graphene oxide(Gc-dMO)is developed using a simple cost-effective hydrothermal *** degree of disorderness increases owing to the hetero-atom doping and graphene oxide *** is demonstrated that layered dMO and Gc-dMO undergo a structural transition from k-birnessite to the Zn-buserite phase upon the first discharge,which enhances the intercalation of Zn^(2+)ions,H_(2)O molecules in the layered *** Gc-dMO cathode exhibits an excellent capacity of 302 mAh g^(-1)at a current density of 100 mAg^(-1)after 100 cycles as compared with the dMO cathode(159 mAhg^(-1)).The excellent electrochemical performance of the Gc-dMO cathode owing to co-doping and graphene oxide sheets enhances the interlayer gap and disorderness,and maintains structural stability,which facilitates the easy reverse intercalation and de-intercalation of Zn^(2+)ions and H_(2)O ***,Gc-dMO is a promising cathode material for large-scale aqueous ZIBs.

关键词： aqueous zinc-ion batteries birnessite buserite disordered structure phase transformation

Determination of diffusion coefficient by image-based fluorescence recovery after photobleaching and single particle tracking system implemented in a single platform

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Journal of Innovative Optical Health Sciences 2021年第2期4卷 93-101页

作者： Donghee Lee Jeonghoon Lee jung kyung kim Department of Genetics Cell Biology and Anatomy University of Nebraska Medical CenterOmahaNE 68198USA School of Mechanical Engineering kOREA TEcH Cheonan 31253Republic of Korea School of Mechanical Engineering and Department of Integrative Biomedical Science and Engineering Graduate School Kookmin University Seoul 02707Republic of Korea

Fluorescence recovery after photobleaching(FRAP)and single particle tracking(SPT)techni-ques determine the diffusion coefficient from average diffusive motion of high-concentration molecules and from trajectories of low-concentration single molecules,*** dif-fusion coefficients measured by FRAP and SPT techniques for the same biomolecule on cell membrane have exhibited inconsistent values across laboratories and platforms with larger dif-fusion coefficient determined by FRAP,but the sources of the inconsistency have not been investigated ***,we designed an image-based FRAP-SPT system and made a direct comparison between FRAP and SPT for diffusion coefficient of submicron particles with known theoretical values derived from Stokes-Einstein equation in aqueous *** combined iFRAP-SPT technique allowed us to measure the diffusion coefficient of the same fluorescent particle by utilizing both techniques in a single platform and to scrutinize inherent errors and artifacts of *** results reveal that diffusion coefficient overestimated by FRAP is caused by inaccurate estimation of the bleaching spot size and can be corrected by simple image *** iFRAP-SPT technique can be potentially used for not only cellular membrane dynamics but also for quantitative analysis of the spatiotemporal distribution of the solutes in small scale analytical devices.

关键词： Diffusion coefficient fluorescence recovery after photobleaching(FRAP) single particle tracking(SPT)

Protective effect of hydrogen sulfide on oxidative stress-induced neurodegenerative diseases

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Neural Regeneration Research 2020年第2期15卷 232-241页

作者： Rubaiya Tabassum Na Young Jeong Junyang jung Department of Anatomy and cell Biology College of MedicineDong-A UniversitySeo-guBusanKorea Department of Medicine Graduate SchoolDong-A UniversitySeo-guBusanKorea Department of Anatomy and Neurobiology College of MedicineKyung Hee UniversityDongdaemun-guSeoulKorea

Hydrogen sulfide is an antioxidant molecule that has a wide range of biological effects against oxidative stress. Balanced oxidative stress is also vital for maintaining cellular function in biological system, where reactive oxygen species are the main source of oxidative stress. When the normal redox balance is disturbed, deoxyribonucleic acid, lipid, and protein molecules are oxidized under pathological conditions, like diabetes mellitus that leads to diabetic peripheral neuropathy. In diabetes mellitus-induced diabetic peripheral neuropathy, due to hyperglycemia, pancreatic beta cell(β cell) shows resistance to insulin secretion. As a consequence, glucose metabolism is disturbed in neuronal cells which are distracted from providing proper cell signaling pathway. Not only diabetic peripheral neuropathy but also other central damages occur in brain neuropathy. Neurological studies regarding type 1 diabetes mellitus patients with Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis have shown changes in the central nervous system because high blood glucose levels(HbA1 c) appeared with poor cognitive function. Oxidative stress plays a role in inhibiting insulin signaling that is necessary for brain function. Hydrogen sulfide exhibits antioxidant effects against oxidative stress, where cystathionine β synthase, cystathionine γ lyase, and 3-mercaptopyruvate sulfurtransferase are the endogenous sources of hydrogen sulfide. This review is to explore the pathogenesis of diabetes mellitus-induced diabetic peripheral neuropathy and other neurological comorbid disorders under the oxidative stress condition and the anti-oxidative effects of hydrogen sulfide.

关键词： Alzheimer's disease amyotrophic lateral sclerosis antioxidant diabetic peripheral neuropathy DNA oxidation hydrogen sulfide mitochondrial dysfunction oxidative stress Parkinson's disease reactive oxygen species