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The Structural Study of InN Thin Films Grown on Different Substrates by Using RF Sputtering Method
Weizhen HE,박세정,김형국,황윤회,이익재 한국물리학회 2010 새물리 Vol.60 No.4
We prepared the InN thin films by using RF sputtering on various substrates to investigate the structural characteristics of InN and to find an optimum condition of growing high-quality InN thin film on each substrate. The structural analysis of films deposited on Al₂O₃ (0001), Si (100), Pt(200)/TiO₂/SiO₂/Si, MgO (100) and GaAs (100) is reported by measuring x-ray diffraction and scanning electron microscopy. The InN thin films usually have wurtzite structure. At a certain growth condition, we could get the high quality InN on each substrates except Pt (100). Through atomic force microscopy measurement, it was observed that the InN thin films with c-axis preferred orientation have smoother surface than those with several orientations. It was also found that the thermal expansion coefficient of substrates is also important to get high quality InN thin film.
He, Weizhen,Atabaev, Timur Sh.,Kim, Hyung Kook,Hwang, Yoon-Hwae American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.35
<P>TiO<SUB>2</SUB> nanoparticle-based dye-sensitized solar cells (DSSCs) were modified by depositing a layer of a long-persistent phosphor, SrAl<SUB>2</SUB>O<SUB>4</SUB>:Eu<SUP>2+</SUP>,Dy<SUP>3+</SUP>, on top of the TiO<SUB>2</SUB> nanoparticle layer to prepare working electrodes of the DSSCs. SrAl<SUB>2</SUB>O<SUB>4</SUB>:Eu<SUP>2+</SUP>,Dy<SUP>3+</SUP> red-shifted the short UV wavelengths into the main absorption range of the dye commonly used in DSSCs. The SrAl<SUB>2</SUB>O<SUB>4</SUB>:Eu<SUP>2+</SUP>,Dy<SUP>3+</SUP> layer also acted as a light-scattering layer to reduce the loss of visible light. Incident photon to current conversion efficiency measurements showed that the application of such phosphor materials enhanced light-harvesting. The open-circuit voltage was found to be higher in the modified DSSCs. The electrons produced by the SrAl<SUB>2</SUB>O<SUB>4</SUB>:Eu<SUP>2+</SUP>,Dy<SUP>3+</SUP> particles contribute to the reduction of I<SUB>3</SUB><SUP>–</SUP> to I<SUP>–</SUP>, leading to a lower I<SUB>3</SUB><SUP>–</SUP> concentration in the electrolyte. This reduces the recapture of electrons injected in the conduction band of TiO<SUB>2</SUB> by triiodide ions and promotes the open circuit voltage. The performance of the modified DSSC device was improved compared with the cell using a working electrode without this phosphor layer. An overall 13% improvement in conversion efficiency of modified DSSCs was achieved due to the presence of the phosphor layer.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-35/jp307954n/production/images/medium/jp-2012-07954n_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp307954n'>ACS Electronic Supporting Info</A></P>
Advantages of using Ti-mesh type electrodes for flexible dye-sensitized solar cells
He, Weizhen,Qiu, Jijun,Zhuge, Fuwei,Li, Xiaomin,Lee, Jae-Ho,Kim, Yang-Do,Kim, Hyung-Kook,Hwang, Yoon-Hwae IOP Pub 2012 Nanotechnology Vol.23 No.22
<P>We used Ti meshes for both the photoanodes and counter electrodes of dye-sensitized solar cells (DSSCs) to improve the flexibility and conductivity of the electrodes. These mesh type electrodes showed good transparency and high bendability when subjected to an external force. We demonstrated the advantages of cells using such electrodes compared to traditional transparent conducting oxide based electrodes and back side illuminated DSSCs, such as low sheet resistance, elevated photo-induced current and enhanced sunlight utilization. Nanotube layers of different thicknesses were investigated to determine their effect on the photovoltaic parameters of the cell. The overall efficiency of the best cells was approximately 5.3% under standard air mass 1.5 global (AM 1.5 G) solar conditions. Furthermore, the DSSCs showed an efficiency of approximately 3.15% due to the all Ti-mesh type electrodes even after illumination from the back side.</P>
The fabrication of TiO2 mesoporous thick films by employing a pre-embedded ZnO nanorods support.
He, Weizhen,Qiu, Jijun,Park, Se-Jeong,Lee, Jea-Ho,Kim, Yang-Do,Kim, Hyung-Kook,Hwang, Yoon-Hwae American Scientific Publishers 2009 Journal of Nanoscience and Nanotechnology Vol.9 No.12
<P>TiO2 mesoporous films with a thickness more than 2 microm were synthesized through the evaporation-induced self-assembly approach. In order to prevent the formation of cracks due to the strain during the calcination, we employed the ZnO nanorod arrays as a pre-embedded support, which were obtained from an aqueous solution method. The spaces between ZnO nanorods were filled with TiO2 sol-gel by a dip-coater. Then ZnO nanorods embedded in the thick film were eliminated by a wet chemical etching method and the left spaces were refilled by the TiO2 sol-gel. As a result, a dense and thick TiO2 mesoporous film was obtained. The resultant materials were characterized in detail by using small angle X-ray diffraction (SAXRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy methods (TEM).</P>
Wang, Weizhen,Zhang, Juan,Hu, Honghong,Yu, Baojun,He, Jintong,Yao, Tingting,Gu, Yaling,Cai, Zhengyun,Xin, Guosheng Asian Australasian Association of Animal Productio 2022 Animal Bioscience Vol.35 No.11
Objective: Inosine monophosphate (IMP) is a key factor that imparts of meat flavor. Differences in the IMP content in the muscles were evaluated to improve chicken meat quality. Methods: For this study, the IMP content was detected by high performance liquid chromatography. The gene expression profiles of Jingyuan chickens with different feeding patterns and different sexes were analyzed by RNA-sequencing (RNA-seq). Results: Breast muscle IMP content in free-range chickens was extremely significantly higher than that of caged chickens (p<0.01). Breast muscle IMP content in hens was also higher than that of cocks, but the difference was not significant. Correlation analysis showed that the breast muscle IMP content in caged hens and cocks was negatively correlated with the shear force, and the breast muscle IMP content in free-range hens was significantly negatively correlated with the shear force (p<0.05). The two key genes associated with IMP synthesis in chickens with different feeding patterns were glutamate-ammonia ligase (GLUL) and phosphodiesterase 10A (PDE10A). Bioinformatics analysis revealed that the GLUL and PDE10A genes are involved in glutamine biosynthesis and purine salvage pathways respectively. In addition, GLUL expression was positively correlated with the IMP content in caged and free-range chickens, and PDE10A expression was significantly positively correlated with the IMP content in caged and free-range chickens (p<0.05). Conclusion: These findings will facilitate the comprehension of the deposition of IMP in the muscles and thereby aid the process of selection and breeding of good quality local chickens.
Reinforcement Analysis of Rigid Hangers for Existing Old Arch Bridges: A Case Study of Ling Bridge
Shuai Yuan,Weizhen Chen,Fan Yang,Tiantao He,Guoxian Liu 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.6
Ling Bridge, built in 1936, is an old half-through riveted steel arch bridge with rigid hangers and a fl oating deck system. The eff ects of various factors, such as temperature, vehicle load, and crowd load, have caused large additional stresses on the rigid hangers. According to the inspection in 2011, the bridge was in a dangerous state. Therefore, improving the structural strength of the bridge and prolonging the service life for another 40 years while protecting the cultural relic were major problems. This study analyzes rigid hangers on the premise that the reinforcement schemes of other bridge components have been determined. First, the damage situation, material properties and mechanical behaviors of old hangers are evaluated. Second, an appropriate reinforcement method is proposed. Third, mechanical and fatigue analyses are conducted on the new structures to prove the rationality of the reinforcement method. For the undemolished old structures, a fracture assessment of existing damage is performed to obtain the evolution laws and ensure safety. Finite element calculations and fatigue fracture analyses show that the proposed reinforcement method for the hanger system can reduce all hangers’ stresses eff ectively to prolong service life and protect the cultural relic.
Qiu, Jijun,Li, Xiaomin,He, Weizhen,Park, Se-Jeong,Kim, Hyung-Kook,Hwang, Yoon-Hwae,Lee, Jae-Ho,Kim, Yang-Do IOP Pub 2009 Nanotechnology Vol.20 No.15
<P>Well-aligned ultralong ZnO nanorod arrays with a length of 10 µm have been synthesized on glass substrates using a preheating hydrothermal method. The diameter of the nanorods is in the range from 50 to 80 nm, and the aspect ratio and alignment can be simply controlled by varying the preheating time. Based on the evolution of aspect ratio with preheating time, a possible growth mechanism was proposed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the nanostructures are well oriented with the <I>c</I>-axis perpendicular to the substrate. The photoluminescence (PL) spectrum of the as-grown ZnO nanostructure reveals a near-band-edge (NBE) emission peak and a yellow emission, and the origin of yellow emission was confirmed to be from the absorbed hydroxyl group. The ultralong nanorod arrays made in solution have a desirable diameter, length, density and orientation for ordered nanodevice applications. </P>
Lim, Jae-Min,He, Weizhen,Kim, Hyung-Kook,Hwang, Yoon-Hwae Korea Photovoltaic Society 2013 Current Photovoltaic Research Vol.1 No.2
We report here flexible dye-sensitized solar cells (DSSC) based on Ti-mesh electrodes that show good mechanical flexibility and electrical conductivity. $TiO_2$ nanotube arrays prepared by electrochemical anodizing Ti-mesh substrate were used as photoanode. A Pt-coated Ti-mesh substrate was used as counter electrode. The photoanodes were modified by coating a $TiO_2$ porous layer onto the $TiO_2$ nanotubes in order to increase the specific surface area. To increase the long term stability of the DSSCs, a gel type electrolyte was used instead of a conventional liquid type electrolyte. The DSSC based on $33.2{\mu}m$ long porous $TiO_2$ nanotubes exhibited a better energy conversion efficiency of ~2.33%, which was higher than that of the DSSCs based on non-porous $TiO_2$ nanotubes.
Jae-Min Lim,Weizhen He,Hyung-Kook Kim,Yoon-Hwae Hwang 한국태양광발전학회 2013 Current Photovoltaic Research Vol.1 No.2
We report here flexible dye-sensitized solar cells (DSSC) based on Ti-mesh electrodes that show good mechanical flexibility and electrical conductivity. TiO2 nanotube arrays prepared by electrochemical anodizing Ti-mesh substrate were used as photoanode. A Pt-coated Ti-mesh substrate was used as counter electrode. The photoanodes were modified by coating a TiO2 porous layer onto the TiO2 nanotubes in order to increase the specific surface area. To increase the long term stability of the DSSCs, a gel type electrolyte was used instead of a conventional liquid type electrolyte. The DSSC based on 33.2 μm long porous TiO2 nanotubes exhibited a better energy conversion efficiency of ~2.33%, which was higher than that of the DSSCs based on non-porous TiO2 nanotubes.