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Marie Carlson,Bengt Jacobsson 서강대학교 동아연구소 2016 TRaNS(Trans –Regional and –National Studies of Sou Vol.4 No.1
This contribution is about a female transnational student from Turkey, Hafize, studying for four years at an Islamic Malaysian university. She was interviewed during the research project “Transnational Student Mobility in Higher Education in Asia”, a multi-sited ethnographic project containing six sub-studies aiming to illuminate student voices and the impact of cultural processes on student-inhabited transnational spaces, identity negotiations, and networks. Through a bottom-up perspective, and with life story as the principal method, the project illustrates processes of social change and relations between the individual and society. Questions are posed about, inter alia, the motivations and reasons that may be identified in the educational stories. Hafize’s narrative is discussed as a relational and contextual story, in which family relations and the significance of education, gender, ethnicity, religion, and socio-economic and political situations intersect. Education is given different meanings: instrumental and reflexive as well as emotional aspects. Turning points and the concept of capital, especially social and emotional capital, are addressed. Hafize’s family of eight siblings is deeply involved in serial reciprocity, a tightly bonded network supporting all the children in their efforts to study. Hafize’s story is substantially gendered and ‘ethnified’– areflexive emotional identity project, in which education and religion are given high priority. In Turkey secularist legislation was an obstacle. The studies abroad provided possibilities for selfdevelopment but tempered with some limitations.
Synthesis and electrochemical properties of polyaniline nanofibers by interfacial polymerization.
Manuel, James,Ahn, Jou-Hyeon,Kim, Dul-Sun,Ahn, Hyo-Jun,Kim, Ki-Won,Kim, Jae-Kwang,Jacobsson, Per American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.4
<P>Polyaniline nanofibers were prepared by interfacial polymerization with different organic solvents such as chloroform and carbon tetrachloride. Field emission scanning electron microscopy and transmission electron microscopy were used to study the morphological properties of polyaniline nanofibers. Chemical characterization was carried out using Fourier transform infrared spectroscopy, UV-Vis spectroscopy, and X-ray diffraction spectroscopy and surface area was measured using BET isotherm. Polyaniline nanofibers doped with lithium hexafluorophosphate were prepared and their electrochemical properties were evaluated.</P>
Guerrero, Antonio,Garcia-Belmonte, Germà,Mora-Sero, Ivan,Bisquert, Juan,Kang, Yong Soo,Jacobsson, T. Jesper,Correa-Baena, Juan-Pablo,Hagfeldt, Anders American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.15
<P>Impedance spectroscopy offers access to all the different electronic and ionic processes taking place simultaneously in an operating solar cell. To date, its use on perovskite solar cells has been challenging because of the richness of the physical processes occurring within similar time domains. The aim of this work is to understand the general impedance response and propose a general equivalent circuit model that accounts for the different processes and gives access to quantitative analysis. When the electron-selective contacts and the thickness of the perovskite film are systematically modified, it is possible to distinguish between the characteristic impedance signals of the perovskite layer and those arising from the contacts. The study is carried out using mixed organic lead halogen perovskite (FA(0.85)MA(0.15)Pb(I0.85Br0.15)(3)) solar cells with three different electron-selective contacts: SnO2, TiO2, and Nb2O5. The contacts have been deposited by atomic layer deposition (ALD), which provides pinhole-free films and excellent thickness control in the absence of a mesoporous layer to simplify the impedance analysis. It was found that the interfacial impedance has a rich structure that reveals different capacitive processes, serial steps for electron extraction, and a prominent inductive loop related to negative capacitance at intermediate frequencies. Overall, the present report provides insights into the impedance response of perovskite solar cells which enable an understanding of the different electronic and ionic processes taking place during device operation.</P>
Kim, Jae-Kwang,Lim, Du-Hyun,Scheers, Johan,Pitawala, Jagath,Wilken, Susanne,Johansson, Patrik,Ahn, Jou-Hyeon,Matic, Aleksandar,Jacobsson, Per The Korean Electrochemical Society 2011 한국전기화학회지 Vol.14 No.2
In this study we have investigated the Li-ion coordination, thermal behavior and electrochemical stability of N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ($Py_{14}TFSI$) with lithium bis(trifluoromethanesulfony)imide (LiTFSI) doping intended for use as electrolytes for lithium batteries. The ionic conductivity is reduced and glass transition temperature ($T_g$) increases with LiTFSI doping concentration. Also, the electrochemical stability increases with LiTFSI doping. A high LiTFSI doping could enhance the electrochemical stability of electrolytes for lithium batteries, whereas the decrease in the ionic conductivity limits the capacity of the battery.
김재광,임두현,Johan Scheers,Jagath Pitawala,Susanne Wilken,Patrik Johansson,안주현,Aleksandar Matic,Per Jacobsson 한국전기화학회 2011 한국전기화학회지 Vol.14 No.2
In this study we have investigated the Li-ion coordination, thermal behavior and electrochemical stability of N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py_14TFSI) with lithium bis(trifluoromethanesulfony)imide (LiTFSI) doping intended for use as electrolytes for lithium batteries. The ionic conductivity is reduced and glass transition temperature (T_g) increases with LiTFSI doping concentration. Also, the electrochemical stability increases with LiTFSI doping. A high LiTFSI doping could enhance the electrochemical stability of electrolytes for lithium batteries, whereas the decrease in the ionic conductivity limits the capacity of the battery.
Kim, J. K.,Scheers, J.,Ryu, H. S.,Ahn, J. H.,Nam, T. H.,Kim, K. W.,Ahn, H. J.,Cho, G. B.,Jacobsson, P. Royal Society of Chemistry 2014 Journal of Materials Chemistry A Vol.2 No.6
We designed a novel layer-built rechargeable lithium ribbon-type battery intended for textile or cloth based applications. The ribbon-type battery, 2.4 mm (or 1 mm) wide and 10 cm long, is composed of a double layer LiFePO4 cathode and an amorphous silicon nanofilm. The double layer LiFePO4 and amorphous silicon electrodes were prepared using the doctor blade method and a vertical deposition technique, respectively. The structure and morphology of the LiFePO4 and the silicon thin film were characterized by Rietveld refinement, SEM and TEM. At room temperature the ribbon-type battery exhibited an initial discharge capacity of 166.4 and 132.7 mA h g (1) at 0.5 and 1 C-rate, respectively. A reasonably good cycling performance and high coulombic efficiency under the high current density of 1 C-rate could be obtained with the Si/LiFePO4 ribbon-type battery. Also, a high volumetric capacity of 336 mA h cm (3) at 0.5 C-rate was achieved, which makes the ribbon-type battery suitable for practical use.
Kim, Jae-Kwang,Manuel, James,Lee, Min-Ho,Scheers, Johan,Lim, Du-Hyun,Johansson, Patrik,Ahn, Jou-Hyeon,Matic, Aleksandar,Jacobsson, Per The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.30
<P>A thin flexible polypyrrole-lithium iron phosphate (PPy-LiFePO<SUB>4</SUB>) based cathode has been fabricated. A slurry containing carbon black, a binder and the active material prepared by direct polymerization of pyrrole on the surface of LiFePO<SUB>4</SUB> (LFP) was spread on an Al/carbon film substrate by the doctor blade method. Transmission electron micrographs reveal that PPy nanoparticles form a web like structure over the surface of LFP particles. After doping with lithium ions the PPy network becomes conducting. When evaluated as a cathode of 180 μm thickness together with a gel polymer electrolyte and a lithium anode, the charge–discharge performance reveals that the electrochemical properties of LFP are influenced to a considerable extent by the PPy. The cells show high initial discharge capacities of 135 and 110 mA h g<SUP>−1</SUP> for 0.041 (<I>C</I>/10) and 0.21 (<I>C</I>/2) mA cm<SUP>−2</SUP>, respectively, and high active material utilization. Furthermore the cells exhibit stable cycle properties even at 0.21 mA cm<SUP>−2</SUP> with a low capacity fade per cycle (∼0.3%).</P> <P>Graphic Abstract</P><P>The flexible polypyrrole-LiFePO<SUB>4</SUB> electrode was prepared on an aluminum/carbon substrate by a doctor blade method. The pyrrole was polymerized on the surface of LiFePO<SUB>4</SUB> and doped by an electrochemical reaction. The 180 μm PPy-LFP/aluminium/carbon cathode was fabricated with a polymer gel electrolyte for high flexibility thin batteries. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm30965c'> </P>