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CVD 법에 의한 Si ( 111 ) 기판에 YBaCuO 계 초전도 박막의 제조
양석우,김영순,신형식 ( Suk Woo Yang,Young Soon Kim,Hyung Shik Shin ) 한국공업화학회 1997 공업화학 Vol.8 No.4
화학증착법을 통하여 650℃의 증착온도와 0.0126Torr의 산소분압인 증착조건에서 원료물질로 β-diketonates 킬레이트 화합물을 사용하여 Si(111) 및 SrTiO₃(100) 기판에 YBa₂Cu₃Oy 고온 초전도 박막을 제조하였다. SrTiO₃(100)기판에서 제조된 박막의 T_(c.onset)과 T_(c.o)는 각각 91K와 87K로 나타났다. 또한, Si(111)기판에서 제조된 박막의 T_(c.onset)은 91K였지만 T_(c.o)는 액체질소 비등점(77.3K)에서는 보이지 않았다. SrTiO₃(100)에 증착된 초전도 박막은 치밀하고 2차원적으로 배열된 미세구조를 갖고 있는 반면, Si(111)에 증착된 초전도 박막은 상대적으로 기공이 많으며 무질서한 미세구조를 형성하였다. Superconducting YBa₂Cu₃Oy thin films were prepared at the deposition temperature of 650℃ under oxygen partial pressure of 0.0126Torr on Si(111) and SrTiO₃(100) substrates by chemical vapor deposition technique using β-diketonates of Y, Ba and Cu as source materials. The thin film fabricated on SrTiO₃(100) had a T_(c.onset) of 91 K and T_(c.o) of 87 K. The thin film prepared on Si(111) had a T_(c.onset) of 91 K but didn`t have a T_(c.o) at liquid nitrogen boiling point(77.3 K). Dense and two-dimensionally well alligned microstructure was developed for the film deposited on SrTiO₃(100) substrate whereas a relatively porous and randomly distributed microstructure was developed for the film prepared on Si(111) substrate.
양석우,이나영,김소열,Suk Woo Yang,Na Young Lee,So Youl Kim 대한안과학회 2006 대한안과학회지 Vol.47 No.9
Purposes: To evaluate the effect of cycloplegia on the visual acuity and stereopsis according to the refraction and age. Methods: This study included 112 eyes of 56 patients, which were divided into three groups according to the refraction. The best corrected visual acuity and stereopsis were compared between without and with cycloplegia in all groups according to age. Results: After cycloplegia, at near, naked visual acuity decreased in 0.53 logMAR, average and stereopsis also deceased from 93 seconds to 343 seconds. At far, the naked and best corrected visual acuity had less decreased than near visual acuity. At near, there was no significant difference on the degree of decreased visual acuity and stereopsis according to refraction, but in emmetropic patients, the visual acuity at near significantly decreased. Patients younger than ten years old had more decreased visual acuity at near compared with older than forty-five years old. Conclusions: After pupil dilatation, there significant decreased near visual acuity and stereopsis, there was little change at far. The degree of decreased vision was different according to the refraction and age, therefore it would be helpful to explain the anticipating result.
발화합성법에 의한 YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6+x</sub> 초전도 선재의 제조
양석우,이영민,김영순,박정식,김찬중,홍계원,신형식,Yang, Suk-Woo,Lee, Young-Min,Kim, Young-Soon,Park, Jeong-Shik,Kim, Chan-Joong,Hong, Gye-Won,Shin, Hyung-Shik 한국공업화학회 1998 공업화학 Vol.9 No.7
$YBa_2Cu_3O_{6+x}(Y123)-Ag$ 초전도 선재를 0/20 wt%의 은(Ag)을 첨가한 발화합성분말과 고상반응분말을 사용하여 플라스틱 압출법으로 제조하였다. 플라스틱 압출법은 분말제조, 플라스틱 paste 제조, 다이 압축, binder 소각 및 소결공정을 포함한다. 양질의 초전도체를 제조하려면 원료물질이 균질하고 미세한 분말이어야 한다. 0/20 wt%를 첨가한 $Y_2O_3-BaCO_3-CuO$ precursor 분말을 발화합성(PS)법과 고상반응(MM)법으로 제조하였다. 원료분말이 Y123 초전도상으로 전이되는 생성속도를 공기중에서 여러온도와 시간별로 반응시켜 알아보았다. 발화합성법으로 제조한 분말이 고상반응법으로 제조한 분말보다 Y123상으로 빠르게 전이되었다. 이것은 PS법으로 제조한 분말이 미세한 크기와 균질한 화학적 조성으로 인해 Y123상으로 빠른 전이를 한 것이기 때문이다. 플라스틱 압출법으로 제조한 Y123-Ag 초전도 선재의 임계전류밀도($J_c$)는 원료분말의 특징에 따라 $150{\sim}230A/cm^2$값을 나타내었다. 은을 20 wt.% 첨가한 발화합성분말로 제조한 선재의 $J_c$는 $230A/cm^2$이었다. $YBa_2Cu_3O_{6+x}(Y123)-Ag$ high-Tc superconducting wires were fabricated by plastic extrusion technique using pyrophoric synthetic and mechanical mixing powder with and without Ag addition(20 wt.%). This method involves powder preparation, plastic paste making, die extrusion, binder burn-out and the sintering process. In order to fabricate a good-quality superconducting body, it is required to use homogeneous and fine-size power as a starting materials. $Y_2O_3-BaCO_3-CuO$ precursor powders with/without Ag addition were prepared both by pyrophoric synthetic(PS) and mechanical mixing(MM) method of raw powders. The formation kinetics of the powder mixtures into Y123 phase was investigated at various temperatures and times in air atmosphere. The powder prepared by PS method was more easily converted into a Y123 phase than the MM powder. The fine size and good chemical homogeneity of the powder prepared by PS method is attributable to the fast formation into a Y123 phase. The critical current density($J_c$) of the Y123-Ag superconducting wires made by plastic extrusion method were in the range of $150A/cm^2{\sim}230A/cm^2$. depending on the charateristics of starting material powders. $J_c$ of the wire prepared by pyrophoric synthetic powder with 20 wt.% Ag addition was $230A/cm^2$.