http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
TFA-MOD법으로 제조된 다층 YBCO 박막의 미세구조 관찰
장석헌,임준형,이창민,황수민,최준혁,심종현,주진호,김찬중,Jang, Seok-Hern,Lim, Jun-Hyung,Lee, Chang-Min,Hwang, Soo-Min,Choi, Jun-Hyuk,Shim, Jong-Hyun,Joo, Jin-Ho,Kim, Chan-Joong 한국초전도학회 2008 Progress in superconductivity Vol.9 No.2
We fabricated $YBa_2Cu_3O_{7-x}$(YBCO) films on (00l) $LaAlO_3$ substrates prepared by metal organic deposition(MOD) method using trifluoroacetate(TFA) solution. The films with various thicknesses were prepared by repeating the dip-coating and calcining processes. The effects of film thickness on phase formation, microstructures, and critical properties were evaluated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The microstructure and resultant critical current($I_C$) and critical current density($J_C$) varied remarkably with film thickness: The ($I_C$) value increased from 39 to 160 A/cm-width as the number of coatings increased from one to four, while the corresponding $J_C$ was measured to be in the range of $0.84-1.21\;MA/cm^2$. Both the $I_C$ and $J_C$ decreased when an additional coating was applied due to microstructural degradation, indicating that the optimum thickness is in the range of $1.1-1.8\;{\mu}m$. The possible cause for the decrease in the $I_C$ and $J_C$ value for film thicker than $1.8\;{\mu}m$ include non-uniform thickness, increased surface roughness, and the poor formability of the YBCO phase and texture arising from the insufficient heat treatment time with respect to the increased thickness.
동시증착법에 의해 성장된 붕화마그네슘 박막의 증착속도에 따른 효과
박성창,강성구,정대길,정준기,임영진,김찬중,김철진,Park, Sung-Chang,Kang, Seong-Gu,Jeong, Dae-Gil,Chung, Jun-Ki,Lim, Yeong-Jin,Kim, Chan-Joong,Kim, Cheol-Jin 한국초전도학회 2008 Progress in superconductivity Vol.10 No.1
Magnesium diboride ($MgB_2$) is an inexpensive and simple superconductor. This material was first synthesized and its structure confirmed in 1953 but its superconducting properties were not discovered until 2001 when they caused great excitement. In this study, superconducting $MgB_2$ thin films on the r-$Al_{2}O_3$ substrates have been grown by the combination of radio frequency magnetron sputtering of B and thermal evaporation of Mg. The deposition conditions were varied by changing deposition rate. Before the co-deposition of Mg and B, the deposition rates of each element have been measured separately. The $MgB_2$ layers had 400nm in thickness and superconducting transition temperatures have been measured around $\sim$38.6K. Superconducting properties have been measured by PPMS, XRD, and SEM.
기계적 합금화 및 in-situ와 ex-situ의 혼합공정을 통한 C 도핑된 ex-situ $MgB_2$ 선재 제조
황수민,이창민,임준형,최준혁,박진현,주진호,전병혁,김찬중,Hwang, Soo-Min,Lee, Chang-Min,Lim, Jun-Hyung,Choi, Jun-Hyuk,Park, Jin-Hyun,Joo, Jin-Ho,Jun, Byung-Hyuk,Kim, Chan-Joong 한국초전도학회 2009 Progress in superconductivity Vol.10 No.2
We successfully fabricated C-doped ex-situ $MgB_2$ wires using two different methods such as mechanical alloying(MA) and combined process(CP) of in-situ and ex-situ. In the MA, the precursor powder was prepared with a mixture of $MgB_2$ and 1 at% C powders by planetary ball milling for 0-100 h. In the CP, on the other hand, C-doped $MgB_2$ powder was prepared with Mg, B, and C powders by in-situ process via compaction, sintering, and crushing. The powders prepared by two methods were loaded into Fe tube and then the assemblages were drawn by a conventional powder-in-tube technique. The MA treatment of C-added $MgB_2$ decreased the particles/grains size and resulted in C-doping into $MgB_2$ after sintering, improving the critical current density($J_c$) in high external magnetic field. For the C-doped $MgB_2$ wire by MA for 25 h, the $J_c$ was $4.1{\times}10^3A/cm^2$ at 5 K and 6.4 T, which was 5.9 times higher than that of pure and untreated $MgB_2$ wire. The CP also provided C-doping into $MgB_2$ and improved the $J_c$ in high magnetic field; the C-doped $MgB_2$ wire fabricated by CP exhibited a $J_c$ being 2.3 times higher than that of the ex-situ wire used commercial $MgB_2$ powder at 5 K and 6.0 T($2.7{\times}10^3A/cm^2\;vs.\;1.2{\times}10^3A/cm^2$).