http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Kim, Young-Kuk,Ahn, Si-Hyun,Chung, Kookchae,Cho, Young-Sang,Choi, Chul-Jin The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.4
<P>Effects of large copper deficiency and surface modification on the photoluminescence of CuInS<SUB>2</SUB> nanocrystals were explored. The large copper deficiency improved PL intensity due to the enhanced internal defect-related emission. Surface modification of copper deficient nanocrystals by simply refluxing with zinc acetate and fatty acid resulted in more than 10 times improvement in the photoluminescence intensity and a large blueshift of the photoluminescence spectra. The uniformity in size/shape distribution after surface modification was attributed to the origin of shrinkage in Stokes shift from ∼600 meV to ∼300 meV in Cu<SUB>0.2</SUB>InS<SUB>2</SUB>/ZnS nanocrystals. Furthermore, the contribution of lattice strain to this large blueshift in emission wavelength in Cu<SUB>0.2</SUB>InS<SUB>2</SUB>/ZnS nanocrystals was proposed and tested with the CdS shell layers. The electronic process underlying the large enhancement of PL intensity was studied with time-resolved and temperature-dependent photoluminescence. This drastically enhanced photoluminescence after surface modification was attributed to the efficient reduction of non-radiative recombination originated from surface trap states, the activation energy of which was estimated to be 85 meV.</P> <P>Graphic Abstract</P><P>The electronic processes underlying the large enhancement of photoluminescence from CuInS<SUB>2</SUB> nanocrystals by copper deficiency and surface modification were explored. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm13170b'> </P>
Optimization of Nominal Mixing Ratio of Mg to B in Fabrication of Magnesium Diboride Bulk
Yun Zhang,Cheng Lu,Si Hai Zhou,Kookchae Chung,Wen Xian Li IEEE 2009 IEEE transactions on applied superconductivity Vol.19 No.3
<P>In this paper bulk magnesium diboride (Mg<SUB>x</SUB>B<SUB>2</SUB>) with x varying from 0.9 to 1.3 was prepared by solid state reaction. The Mg:B mixing ratio for ideal MgB<SUB>2</SUB> is 1:2. The samples were sintered at 800degC for 60 h. Quantitative X-ray diffraction (XRD) analysis was performed to obtain the lattice parameters, the microstrain, and the weight fraction of impurities using the Rietveld refinement method. It has been found that the fraction of pure MgB<SUB>2</SUB> phase increases from x = 0.9 to x = 1.1, and then decreases with further increases in x. Mg<SUB>1.1</SUB>B<SUB>2</SUB> exhibits the highest critical current density, J<SUB>c</SUB>, over other samples in both low fields and high fields. A direct correlation between J<SUB>c</SUB> and connectivity indicates that better connectivity, caused by smaller amounts of impurities, results in the best J<SUB>c</SUB> in Mg<SUB>1.1</SUB>B<SUB>2</SUB>.</P>
Jaimoo Yoo,Young-Kuk Kim,Kookchae Chung,Jaewoong Ko,Xiaolin Wang,Shi Xue Dou Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>MOD solutions for YBCO coated conductors were synthesized with fluorine-free Y & Cu precursor. The fluorine content in the precursor solution was significantly reduced and a fast calcination profile was realized. A crack-free & thick precursor film was successfully obtained just after less than 2 hours of calcination in wet O<SUB>2</SUB> atmosphere. Optimization of the precursor solution with Sm addition enables further improvement of thickness and uniformity of precursor films. The calcinated precursor film was successfully converted to dense and uniform YBCO film after annealing in wet Ar/O<SUB>2</SUB> atmosphere. The measured critical current value was about 273 A/cm-w (J<SUB>c</SUB> ~ 3.8 MA/cm<SUP>2</SUP>), and well-developed microstructure was confirmed. Also discussed are recent developments in the reel-to-reel processing using the precursor solution with low fluorine-content. It was shown that employing fluorine-free Y & Cu precursor solution enabled uniform and fast processing of YBCO coated conductors.</P>
Chemical Modification of Precursor Solution for Long Length YBCO Coated Conductor Fabrication
Yoo, Jaimoo,Kim, Young-Kuk,Chung, Kookchae,Ko, Jaewoong,Hong, Gye-Won,Lee, Hee-Gyoun,Kim, Jin-Heung,Chung, Hyungsik,Wang, X L,Dou, S X Institute of Physics Publishing Ltd 2006 Journal of Physics: Conference Series Vol.43 No.-
<P>Long length MOD processing of YBCO conductor requires high performance precursor solution without degradation during the process. In this study, effect of chemical modification of precursor solution on MOD processing was investigated to meet the requirement. Highly stable YBCO precursor solution was synthesized with PVP (polyvinylpyrrolidone) and crack-free thick precursor film was successfully fabricated. However, annealed YBCO film shows porous microstructures originated from large HF gas generation from thick films and residual carbon from additives. Reduction of fluorine content is required to densify microstructures. In order to reduce fluorine content, F-free Cu-precursor solution was synthesized. YBCO film with J<SUB>c</SUB>&equal;0.8MA/cm<SUP>2</SUP> was grown on buffered RABiTS tape. Annealed YBCO film still contains pores and further reduction of pores is required to improve critical current (I<SUB>c</SUB>)</P>