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Effects of electrochemical synthetic conditions on surface property and photocatalytic performance of copper and iron-mixed p-type oxide electrodes

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Journal of Materials Science & Technology 2018年第9期34卷 1503-1510页

作者： Sun Hee yoon Dong Suk Han Unseock Kang Seung yo Choi Wubulikasimu Yiming Ahmed Abdel-Wahab Hyunwoong Park Chemical Engineering Program Texas A&M University at Qatar School of Energy Engineering Kyungpook National University Department of Mechanical Engineering Texas A&M University at Qatar

Earth-abundant copper and iron-mixed oxide（CuO/CuFeO_2; CFO） film electrodes are synthesized using an electrochemical deposition（ED） technique at two different ED potentials（-0.36 and-0.66 V vs saturated calomel electrode（SCE）; denoted as ED-1 and ED-2, respectively）. Then, their surface morphologies are compared, and the photo（electro）catalytic activities for the reduction of Cr（VI） are examined in aqueous solutions at pH 7 under simulated sunlight（AM 1.5 G; 100 mW cm（-2））. The degree of the electrical potential applied to the ED process significantly affects the thickness of the synthesized electrode film and the intensity ratio of the diffraction peaks of CuO（111） and CuFeO_2（012）. A 200 μm thick ED-2 sample with a distinct stacking of CuO on CuFeO_2 exhibits a larger broadband absorption spectrum than the 50-μm thick ED-1 with less separate stacking. Furthermore, the ED-2 sample has a higher intensity ratio of the diffraction peaks of CuO（111） and CuFe02（012） than ED-1. As-synthesized ED-2 samples produce larger photocurrents, leading to faster Cr（VI） reduction on the surface under given potential bias（-0.5 V vs SCE）or bias-free conditions. The energy levels（i.e., flatband potential） for the two samples are almost the same（only 10 mV difference）, presumably supposing that the enhanced photoactivity of the ED-2 sample for Cr（VI） reduction is due to the facilitated charge transfer. The time-resolved photoluminescence emission spectra analysis reveal that the lifetime（r） of the charge carriers in the ED-1 sample is 0.103 ns, which decreases to 0.0876 ns in the ED-2. The ED-2 sample synthesized at a high negative potential is expected to contribute greatly to the application of other solar-to-fuel energy conversion fields as a highly efficient electrode material.

关键词： Artificial photosynthesis Solar fuel Delafossites Morphology Charge transfer

Investigation of Domain Wall Velocity to External Fields for High-Quality Waveguide-Type Periodically Poled LiNbO_(3) Fabrication

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Journal of Rare Earths 2006年第Z1期24卷 131-135页

作者： Soo Woo Kwon Woo Seok Yang H M Lee Woo Kyung Kim Hang yong Lee Dae Ho yoon yo Seung Song Department of Materials Engineering Hankuk Aviation UniversityGoyang 412-791Korea Nano Bio-Photonics Team Korea Electronics Technology InstituteBundang 463-816Korea Department of Advanced Material Engineering Sungkyunkwan UniversitySuwon 440-746Korea

The Ti-doped waveguide-type periodically poled LiNbO_(3)(PPLN)were fabricated and the dependence of domain wall velocity on an external field applied for domain inversion was *** whole polarization reversal process was computer-controlled to regulate domain wall expansion at a feedback time shorter than 5μ*** coercive voltage and several values of excess voltage were applied on 500μm-thick wafers serially connected to a 1-MOhm external resistor which had an effect of the poling current reduction,*** deceleration of domain wall *** domain wall velocity is sensitive to the poling voltage,precisely speaking,to the excess *** domain wall velocities were 28.70,16.02 and 5.75μm·s^(-1)under poling field of 23.5,22.0 and 21.0 kV·mm^(-1),***,average duty cycle of PPLN is about 49.93%.

关键词： periodically poled lithium niobate coerciv field duty cycle domain wall velocity quasi phase matching

Hypothyroidism affects astrocyte and microglial morphology in type 2 diabetes

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Neural Regeneration Research 2013年第26期8卷 2458-2467页

作者： Sung Min Nam yo Na Kim Dae young yoo Sun Shin Yi Jung Hoon Choi In Koo Hwang Je Kyung Seong Yeo Sung yoon Department of Anatomy and Cell Biology College of Veterinary Medicine Research Institute for Veterinary Science Seoul National University Department of Biomedical Laboratory Science College of Biomedical Sciences Soonchunhyang University Department of Anatomy College of Veterinary Medicine Kangwon National University

In the present study, we investigated the effects of hypothyroidism on the morphology of astrocytes and microglia in the hippocampus of Zucker diabetic fatty rats and Zucker lean control rats. To induce hypothyroidism, Zucker lean control and Zucker diabetic fatty rats at 7 weeks of age orally received the vehicle or methimazole, an anti-thyroid drug, treatment for 5 weeks and were sacrificed at 12 weeks of age in all groups for blood chemistry and immunohistochemical staining. In the me- thimazole-treated Zucker lean control and Zucker diabetic fatty rats, the serum circulating triiodo- thyronine （T3） and thyroxine （＇I＂4） levels were significantly decreased compared to levels observed in the vehicle-treated Zucker lean control or Zucker diabetic fatty rats. This reduction was more prominent in the methimazole-treated Zucker diabetic fatty group. Glial fibrillary acidic protein im- munoreactive astrocytes and ionized calcium-binding adapter molecule 1 （Iba-1）-immunoreactive microglia in the Zucker lean control and Zucker diabetic fatty group were diffusely detected in the hippocampal CA1 region and dentate gyrus. There were no significant differences in the glial fibril- lary acidic protein and Iba-1 immunoreactivity in the CA1 region and dentate gyrus between Zucker lean control and Zucker diabetic fatty groups. However, in the methimazole-treated Zucker lean control and Zucker diabetic fatty groups, the processes of glial fibrillary acidic protein immunoreac- tive astrocytes and Iba-1 immunoreactive microglia, were significantly decreased in both the CA1 region and dentate gyrus compared to that in the vehicle-treated Zucker lean control and Zucker diabetic fatty groups. These results suggest that diabetes has no effect on the morphology of as- trocytes and microglia and that hypothyroidism during the onset of diabetes prominently reduces the processes of astrocytes and microglia.

关键词： neural regeneration astrocytes microglia diabetes hypothyroidism complications thyroid hormone obesity methimazole Zucker diabetic fatty rat grants-supported paper neuroregeneration

Effects of multi-dopants （Zn and Ho） in stabilizing spinel structure for cathode materials in lithium rechargeable batteries-Novel chelated sol-gel synthesis

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Particuology 2016年第1期14卷 87-95页

作者： R. Thirunakaran Taewhan Kim Won-Sub yoon CSIR-Central Electrochemical Research Institute Karaikudi 630 006 Tamil Nadu India Department of Energy Science Sungkyunkwan University Suwon 440-746 South Korea

Multi-doped spinels, namely LiMn204 and LiZnxHoyMn2 x yo4 （x=0.10-0.18; y= 0.02-0.10）, for use as cathode materials for lithium-ion rechargeable batteries were synthesized via sol-gel method, using lauric acid as the chelating agent, to obtain micron-sized particles. The physical properties of the synthesized samples were investigated using differential thermal analysis, Fourier-transform infrared spectroscopy, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy, energy-dispersive X-ray analysis, and electrochemical methods. XRD showed that LiMn204 and LiZnxHoyMn2_x y04 have high degrees of crystallinity and good phase purities. The SEM images of LiMn204 showed an ice-cube morphology with particles of size 1 μm. Charge-discharge studies showed that undoped LiMn2 O4 delivered the discharge capacity of 124 mA h/g with coulombic efficiency of 95% during the first cycle, whereas doped spinels delivered discharge capacities of 125, 120, and 127 mA h/g in the first cycle with coulombic efficiencies of 96%, 91%, and 91%, respectively.

关键词： Holmium Zinc Lauric acid Sol-gel Spinel cathode Lithium-ion battery

Synthesis and electrochemical properties of dual doped spinels LiNi_xAl_yMn_(2-x-y)O_4 via facile novel chelated sol–gel method as possible cathode material for lithium rechargeable batteries

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Journal of Energy Chemistry 2017年第1期26卷 101-114页

作者： R.Thirunakaran Gil Hwan Lew Won-Sub yoon CSIR-Central Electrochemical Research Institute Sungkyunkwan University Department of Energy Science

LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating *** synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis（TG/DTA）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,field-emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM） and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy（EIS） and differential capacity curves（dQ/dE）.Finger print XRD patterns of LiMnOand LiNiAlMnOfortify the high degree of crystallinity with better phase *** images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth（50nm） with ice-cube surface *** images of the spinel LiMnOshows the uniform spherical morphology with particle size of（100 nm） while low level of Al-doping spinel（LiNio.5Alo.05Mn1.45O4） displaying cloudy particles with agglomerated particles of（50nm）.The LiMnOsamples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 *** all four dopant compositions investigated,LiNiAlMnOdelivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle（capacity retention of 92%） over the investigated 10 *** impedance studies of spinel LiMnOand LiNiAlMnOdepict the high and low real polarization of 1562 and 1100 Ω.

关键词： Multi-doping Sol–gel method Behenic acid Differential capacity Spinel cathode

Sol-Gel Synthesis Using Novel Chelating Agent and Electrochemical Characterization of Binary Doped LiMn₂O₄ Spinel as Cathode Material for Lithium Rechargeable Batteries

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World Journal of Nano Science and Engineering 2016年第1期6卷 1-19页

作者： Ramasamy Thirunakaran Gil Hwan Lew Won-Sub yoon CSIR-Central Electrochemical Research Institute Karaikudi India Department of Energy Science Sungkyunkwan University Suwon Republic of Korea

LiMn2O4 and LiCuxCryMn2-x-yo4 (x = 0.50;y = 0.05 - 0.50) powders have been synthesized via sol-gel method for the first time using Myristic acid as chelating agent. The synthesized samples have been taken to physical ... 详细信息

LiMn2O4 and LiCuxCryMn2-x-yO4 (x = 0.50;y = 0.05 - 0.50) powders have been synthesized via sol-gel method for the first time using Myristic acid as chelating agent. The synthesized samples have been taken to physical and electrochemical characterization such as thermo gravimetric analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical characterization viz., electrochemical galvanostatic cycling studies, electrochemical impedance spectroscopy (EIS) and differential capacity curves (dQ/dE). XRD patterns of LiMn2O4 and LiCuxCryMn2-x-yO4 confirm high degree of crystallinity with good phase purity. FESEM image of undoped pristine spinel lucidly depicts cauliflower morphology with good agglomerated particle size of 50 nm while 0.5-Cu doped samples depict the pebbles morphology. TEM images of the spinel LiMn2O4 and LiCu0.5Cr0.05Mn1.45O4 authenticate that all the synthesized particles via sol-gel method are nano-sized (100 nm) with spherical surface and cloudy particles morphology. The LiMn2O4 samples calcined at 850℃ deliver the high discharge capacity of 130 mA·h/g with cathodic efficiency of 88% corresponds to 94% columbic efficiency in the first cycle. Among all four compositions studied, LiCu0.5Cr0.05Mn1.45O4 delivers 124 mA·h/g during the first cycle and shows stable performance with a low capacity fade of 1.1 mA·h/g cycle over the investigated 10 cycles.

关键词： Multi-Doping Sol-Gel Method Myristic Acid Differential Capacity Spinel Cathode