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Flux-pinning Properties of YBa2Cu3O7−x Multilayered Films with Y2O3 and ZnO Nanoparticle Inclusions
강병원,위창환,Duc Hai Tran,Witha Berlian Kesuma Putr,황태종,김동호 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.11
We investigated the flux-pinning properties of YBa2Cu3O7−x (YBCO) films in which Y2O3 and ZnO nanoparticles were uniformly embedded by using the pulsed laser deposition (PLD) technique. Y2O3 and ZnO nanoparticles with average sizes of 10–30 nm and with different densities by changing the number of nanoparticle layers were introduced in a YBCO matrix in the form of a multilayered structure. The total thickness of the YBCO superconducting layers was kept to be 250 nm. Dilute doping was found to be effective for both Y2O3 and ZnO nanoparticles. For Y2O3 doping, critical current density (Jc) enhancements over a wide range of fields were obtained in 1- and 5-layer doped samples, while weak Jc enhancements and a better field dependence of Jc were found in the YBCO film with 1 layer of ZnO. Based on an analysis of surface morphology, the transition temperature (Tc), and Jc, we discuss the difference between the two types of nanoparticles as flux-pinning centers.
Mg(B1−xCx)2 단결정의 윗임계자기장의 온도 의존성에 대한 연구
강병원,박민석,이현숙,정명화,이성익 한국물리학회 2009 새물리 Vol.58 No.6
We investigated the temperature dependence of the upper critical field of Mg(B1−xCx)2 single crystals by using transport measurements. We found that the upper critical field, Hc2(T), of doped MgB2 single crystals increased for both H //c and H//ab as C was introduced. Accordingly, the Hc2(T) anisotropy systematically decreased with increased C doping. This may be due to a decrease in the anisotropy of the σ-band, which decrease is caused by the C introduction. 보론의 일부를 탄소로 치환한 MgB2 단결정을 제작하여 전기수송 특성을 측정하고 윗임계자기장의 변화를 연구하였다. 탄소가 첨가됨에 따라 자기장이 c축과 나란하게 가해진 경우와 수직으로 가해진 경우 모두 윗임계자기장이 증가하였는데 이는 이론에서 예측한 결과와 잘 부합되었다. 특히 자기장이 c축에 수직으로 가해진 경우에는 탄소 첨가량이 많을수록 절대영도에서의 윗임계자기장이 증가하였다. 결과적으로 윗임계자기장의 이방성의 값과 온도 의존성이 탄소의 첨가량이 증가할수록 체계적으로 감소하여 탄소가 10% 첨가된 경우 윗임계자기장의 이방성은 매우 약한 온도 의존성을 나타내었다.
강병원,박민석,이현숙,이성익 한국초전도학회 2010 Progress in superconductivity Vol.12 No.1
We have studied the anisotropy of the London penetration depth of carbon doped MgB2 single crystals, which was obtained from reversible magnetization measurements with the magnetic field both parallel and perpendicular to the c-axis. Similar to the pure MgB2, the anisotropy of the upper critical field H γ decrease with temperature while the anisotropy of the London penetration depth λ γ slowly increases with temperature. However, the temperature dependence of H γ is drastically reduced and the value of λ γ becomes nearly ~1 as C is introduced. These results indicate that C substitution increases impurity scattering mainly in the σ bands. The temperature dependence of the anisotropies agree well with the theoretical predictions with impurity scattering.
Effect of SiC buffer layer on flux pinning property of MgB2 tapes
강병원,Witha B.K. Putri,강원남 한국물리학회 2019 Current Applied Physics Vol.19 No.6
In this paper we aimed at investigating the flux pinning property of MgB2 films on hastelloy tapes which are buffered on various thicknesses of SiC layers. We have observed that the increase in thickness of the SiC buffer layer is very closely related with the systematic improvement of the field dependence of the critical current densities (Jc) of MgB2 tapes while the values of Jc decreased. According to the analysis of the pinning force density (Fp), there exist two pinning sources both in the pure MgB2 and in the MgB2 film with the thinnest SiC buffer layer. On the while, the pinning source observed in the MgB2 films with thicker SiC buffer layers appears to be different from those previously mentioned. The different pinning behaviors of MgB2 films may suggest that there be an additional pinning center working on the MgB2 films with thick SiC buffer layers. The microstructural analyses of MgB2 films confirmed that intra-granular defects and columnar grain boundaries may be a dominant pinning mechanism in the pure MgB2 and the MgB2 film with 170 nm-thick SiC buffer layer. For the MgB2 films with thicker SiC buffer layers, carbon diffusion into the MgB2 film, which is defined by the Auger electron spectroscopy, may be the origin of the additional pinning mechanism.
(±)-2-[p-(1-Oxo-2-isoindolinyl)phenyl]butyric acid (인도부펜)의 합성
강병원,마정주,최홍대,윤호상 동의대학교 기초과학연구소 1992 基礎科學硏究論文集 Vol.2 No.1
A convenient method for the synthesis of indobufen, which is a potent antiinflammatory agent, was described. Ethyl 2-phenylbutyrate(4) was prepared by Friedel-Crafts reaction of benzene with ethyl α-chloro-α-(methylthio)acetate(1) followed by ethylation and desulfurization of the resultant ethyl 2-(methylthio)phenylacetate(2). Ethyl 2-(p-aminophenyl)butyrate(6) was prepared by nitration of (4) and successive reduction of ethyl 2-(p-aminophenyl) butyrate(5). Indobufen was obtained by condensation reaction of (6) with phthalic anhydride followed by reduction and hydrolysis of the resultant ethyl 2-[p-(1,3-dioxo-2-isoindolinyl)phenyl]butyrate(7).
Al 첨가가 $MgB_2$ 단결정의 비등방성에 미치는 영향에 대한 연구
강병원,이현숙,박민석,이성익,Kang, Byeong-Won,Lee, Hyun-Sook,Park, Min-Seok,Lee, Sung-Ik 한국초전도학회 2008 Progress in superconductivity Vol.9 No.2
We have studied superconducting properties of $Mg_{1-x}Al_xB_2$ single crystals from reversible magnetization measurements. It was found that the upper critical fields $H_{c2}$ were decreased for both H // c and H // ab as Al is substituted for Mg. As a result, the large anisotropy of $H_{c2}$ observed in pure $MgB_2$, which is considered as one of the characteristics of two-gap superconductor, was decreased with Al doping. On the other hand, the irreversibility fields $H_{irr}$ were increased for x = 0.1 and were significantly decreased for x = 0.2. In contrary to the anisotropy of $H_{c2}$, the anisotropy of $H_{irr}$ was increased as Al concentration increases.
Anisotropy of the Upper Critical Fields in Al-Substituted MgB2 Single Crystals
강병원,김헌정,Hyun-Sook Lee,이성익 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
The temperature dependence of the upper critical fields, Hc2, was deduced from magnetization measurements of high- quality Mg1..xAlxB2 single crystals along the two main crystallographic directions. We found that the strong temperature dependence of the anisotropy of Hc2 ( H = Hab c2=Hc c2) in pure MgB2 was drastically affected by Al doping. H(T) systematically decreased and as a result, H for x = 0.2 became nearly temperature independent. The diminished temperature dependence of H with Al doping is attributed to an enhanced anisotropic impurity scattering, which makes the bands less anisotropic.
Comparison Between Al and C Substitutions in the Upper Critical Field of MgB_2 Single Crystals
강병원,박민석,이현숙,정명화,이성익 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.3
The effect of Al and C substitutions on the upper critical fields H_(c2), of MgB_2 single crystals has been investigated. Despite similar suppression of the transition temperature T_c with increasing Al and C concentrations, the effects of the two substitutions on H_(c2) are totally different. C substitution considerably increases H_(c2)(T) while Al substitution decreases H_(c2)(T). Based on the parameters obtained by fitting experimental data to the dirty-limit two-gap theory, we discuss the difference between the two substitutions in terms of impurity scattering.
Effect of Al Doping on the Irreversible Magnetization of MgB2 Single Crystals
강병원,이현숙,박민석,이성익 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
We studied the temperature and the eld dependences of the irreversibility elds Hirr and the critical current density Jc of Mg1-xAlxB2 single crystals for x up to 0.2. The magnetic investigation revealed that the values and the eld dependences of Jc and Hirr were enhanced for x = 0.1, indicating a stronger pinning due to Al doping. On the other hand, for the heavily-Al-doped sample (x = 0.2), Jc and Hirr were reduced compared to the values for pure MgB2. We also found that the anisotropy of Hirr (= Hab irr/Hc /irr) increased with increasing Al doping, which may be due to a weakening of the inter-plane coupling as Al is substituted for Mg.