• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
• /
• pp.22-25
• /
• 1999

A well oriented Bi-2212 superconductor thick films were fabricated by screen printing with a Cu-free Bi-Sr-Ca-Cu-O powder on a copper plate and heat-treating at 820- $880^{\circ}C$for several minute in low oxygen pressure or are. At minute in low oxygen pressure of air. At , the printing layer partially melted by reaction between the Cu-free precursor by reaction between the Cu-free$870^{\circ}C$ precursor and CuO of the oxidizing copper plate. It is believed that the solid phase is Bi : Sr : Ca : Cu = 2 : 2 : 0 : 1. It is likely that the Bi-2212 superconducting phase is formed at Bi-2212 superconducting phase is formed at Bi-free phase/liquid interface by nucleation and grows.

• 한국세라믹학회지
• /
• 제34권8호
• /
• pp.897-907
• /
• 1997

Thin films of Bi4-xSmxTi3O12(0$\leq$x$\leq$2) were prepared on Pt/Ti/SiO2/Si(100) at $700^{\circ}C$ using spin-coating with sols derived from Bi-Sm-Ti complex alkoxides. From X-ray diffraction analysis, it was observed that Sm-substituted phases resembled ferroelectric Bi4Ti3O12 in structure. Variations of their lattice parameters depending on the amount of Sm-substitution showed that an anomalous structural distortion might exist at x=1. The grain sizes of the thin films decreased from 0.115 ${\mu}{\textrm}{m}$ to 0.078${\mu}{\textrm}{m}$ with increasing the amount of Sm-substitution. The dielectric constants and the remanent polarizations of the thin films decreased with increasing the amount of the Sm-substitution, which were related to decrease of the stereo-active Bi3+ ion contributing to polarization. However, these values were exceptionally high at x=1, compared to those of the other substituted phases. Such an anomaly suggests that the phase of x=1 has 1:1 chemical ordering between Sm and Bi in structure. The thin films of all compositions except x=2 showed ferroelectricity. The thin film of x=2 was paraelectric, whose grains were too fine to exhibit ferroelectricity.

• 한국초전도ㆍ저온공학회논문지
• /
• 제5권1호
• /
• pp.31-34
• /
• 2003

Bi-2223 superconducting wires with 55 filaments were fabricated by stacking, drawing process with different heat-treatment histories. Two kinds of powders were prepared. One was pre-annealed at 760-820 $^{\circ}C$ and low oxygen partial pressure, and the other was only calcined state. Before rolling process, round wires were pre-annealed at 760 -820 $^{\circ}C$ and in a low oxygen partial pressure. We confirmed that pre-annealing step was to transform Bi-2212 orthorhombic structure from Bi-2212 tetragonal structure and to reduce the formation of second phases at superconducting wire. However Bi-2223 phases were formed at higher pre-annealing temperature. Bi-2223 conductor was needed frequently annealing at low temperature because pre-annealing at precursor powder brought about decrease in workability. We could achieve highest Je of 6500 A/$\textrm{cm}^2$ at the tape using Bi-2212 orthorhombic phase by introduced slightly overheating at the 1st sintering process.

• 한국진공학회지
• /
• 제9권4호
• /
• pp.353-359
• /
• 2000

마그네트론 스퍼터링법으로 p형 ($Bi_{0.15}Sb_{0.85})_2Te_3$과 ($Bi_{1-x}Sb_x)_2Te_3$ 열전박막을 제조하여 스퍼터 증착 조건 및 $Sb_2Te_3$ 함량에 따른 열전특성을 분석하였다. Corning glass 기판을 10rpm으로 회전시키며 DC 스퍼터링법으로 $300^{\circ}C$에서 증착한($Bi_{0.15}Sb_{0.85})_2Te_3$ 박막은 $(Bi, Sb)_2Te_3$ 단일상으로 결정화가 완료되고 c축 우선배향성을 나타내었으며, 다른 조건으로 증착한 ($Bi_{0.15}Sb_{0.85})_2Te_3$ 박막보다 높은 185 $\mu$V/K의 Seebeck 계수를 나타내었다. p형(Bi$_{1-x}$ Sb$_{x}$)$_2$Te$_3$ (0.77$\leq$x$\leq$ 1.0) 박막에서는 Sb$_2$Te$_3$ 함량이 증가함에 따라 Seebeck 계수와 전기비저항이 감소하였으며($Bi_{1-x}Sb_x)_2Te_3$조성에서 $0.79\times10^{-3}W/K^2$-m의 최대 출력인자를 나타내었다.

• Journal of Electrochemical Science and Technology
• /
• 제10권4호
• /
• pp.424-432
• /
• 2019

Planar BiVO₄ and 3 wt% Mo-doped BiVO₄ (abbreviated as Mo:BiVO₄) film were prepared by the facile spin-coating method on fluorine doped SnO₂(FTO) substrate in the same precursor solution including the Mo precursor in Mo:BiVO₄ film. After annealing at a high temperature of 450℃ for 30 min to improve crystallinity, the films exhibited the monoclinic crystalline phase and nanoporous architecture. Both films showed no remarkably discrepancy in crystalline or morphological properties. To investigate the effect of surface passivation exploring the Al₂O₃ layer, the ultra-thin Al₂O₃ layer with a thickness of approximately 2 nm was deposited on BiVO₄ film using the atomic layer deposition (ALD) method. No distinct morphological modification was observed for all prepared BiVO₄ and Mo:BiVO₄ films. Only slightly reduced nanopores were observed. Although both samples showed some reduction of light absorption in the visible wavelength after coating of Al₂O₃ layer, the Al₂O₃ coated BiVO₄ (Al₂O₃/BiVO₄) film exhibited enhanced photoelectrochemical performance in 0.5 M Na₂SO₄ solution (pH 6.5), having higher photocurrent density (0.91 mA/㎠ at 1.23 V vs. reversible hydrogen electrode (RHE), briefly abbreviated as V_RHE) than BiVO₄ film (0.12 mA/㎠ at 1.23 V_RHE). Moreover, Al₂O₃ coating on the Mo:BiVO₄ film exhibited more enhanced photocurrent density (1.5 mA/㎠ at 1.23 V_RHE) than the Mo:BiVO₄ film (0.86 mA/㎠ at 1.23 V_RHE). To examine the reasons, capacitance measurement and Mott-Schottky analysis were conducted, revealing that the significant degradation of capacitance value was observed in both BiVO₄ film and Al₂O₃/Mo:BiVO₄ film, probably due to degraded capacitance by surface passivation. Furthermore, the flat-band potential (V_FB) was negatively shifted to about 200 mV while the electronic conductivities were enhanced by Al₂O₃ coating in both samples, contributing to the advancement of PEC performance by ultra-thin Al₂O₃ layer.

• 한국표면공학회지
• /
• 제29권6호
• /
• pp.621-627
• /
• 1996

$SrBi_{2x}TaO_9$ ferroelectric thin films were prepared on platinized silicon substrates using MOD proces, and crystallization behavior of the films was investigated with variation of the annealing temperature and Bi content x. Crystalline phase of bismuth layered perovskite structure was formed even by baking the films at $800^{\circ}C$ for 5 minutes in air, and was not changed by annealing at temperatures raning from $700^{\circ}C$ to $900^{\circ}C$ for 1 hour in oxygen ambient. When $SrBi_{2x}TaO_9$ thin films ($0.8\lex\ie1.6$) were annealed at $800^{\circ}C$, Preferred orientation of the films along c-axis was observed with $x\ge1.2$. With increasing Bi content x, surface morphology of the films was changed from equiaxed grains to elongated grains.

• 한국전기전자재료학회논문지
• /
• 제14권7호
• /
• pp.606-610
• /
• 2001

Bi-2212 HTS tube was fabricated by centrifugal forming and partial melting processes. Bi-2212 bulk tube has been optimized to achieve smooth surface and uniform thickness. The slurry was prepared in the mixing ratio of 10:1 between Bi-2212 powder and binder and initially charged into the rotating mold under the speed of 300~450 rpm. Heat-treatment was performed at the temperature ranges of 860~89$0^{\circ}C$ in air for partial melting. the HTS tube fabricated by centrifugal forming process at 89$0^{\circ}C$ under the rotating speed of 450 rpm was highly densified and the plate-like grains with more than 20${\mu}{\textrm}{m}$ were well oriented along the rotating axis. The measured Tc and J$_{c}$ at 10K on specimen heat treated at 89$0^{\circ}C$ was around 85 K and 1,200 A/$\textrm{cm}^2$ respectively.y.

• The Journal of Korean Physical Therapy
• /
• 제10권1호
• /
• pp.7-21
• /
• 1998

본 연구는 뇌졸중 환자들의 퇴윈 후 1개월까지의 물리치료 양상 및 기능변화와 이에 관련된 요인을 알아보기 위해 1996년 11월 1일 부티 1997년 3월 31일까지 약 4개월 간 부산시 및 대구시, 안동시 등에 소재하고 있는 10개 병원에서 물리치료를 시작한 뇌졸중환자 101명을 대상으로 물리치료를 시작한 시점. 1개월 후, 퇴원 시, 그리고 퇴원 후 1개월이 지난 시점까지 추적하여 기능변화를 평가하였다. 뇌졸중환자의 물리치료 시작 시점의 BI점수는 $27.18\pm23.7$이었고, PS점수는 $17.54\pm4.33$이었다. 물리치료 시작시점을 기준으로 할 때 입원 1개월 후의 BI점수 변화는 평균 21.39(P<0.001), 퇴원시는 37.47(P<0.001), 퇴원 1개월 후는 46.49 만큼 호전되었다(P<0.001). PS점수도 각각 -2.02, -4.52, 리고 -6.26만큼 호전되었다(P<0.001). 그리고 퇴원시에 비해 퇴원후의 변화도 BI점수는 9.01만큼, PS점수는 -1.73만큼 유의하게 호전되었다.(P<0.001). 물리치료 시작시점과 퇴원 시의 BI점수 변화와 유의한 관련이 있는 요인은 물리치료 시작시점의 BI점수와 연령으로 (p<0.05), 물리치료 시작시점의 BI점수가 낮고 연령이 40세 미만에서 기능호전이 컸다. 물리치료 시작시점과 종료시점 사이의 BI점수의 변화는 물리치료 시작시점의 BI점수, 퇴원 1개월 후에 적극적으로 물리치료를 받았는지의 여부, 연령 그리고 수술여부와 유의한 관련성이 있었다. (p<0.05). 즉, 무리치료 시작시점의 BI점수가 낮고, 퇴원 1개월 후에 적극적으로 물리치료를 받은 환자, 연령 40세 미만에, 그리고 수술을 받지 않은 환자에서 기능호전이 컸다. 퇴원시와 퇴원 1개월 후의 BI점수 변화와 관련 있는 변수는 퇴원시의 BI점수, 마비부위, 종교유무 이었는데, 퇴원시의 BI점수가 낮고 좌측마비환자이며 종교를 믿는 환자의 기능호전이 유의하게 컸다(p<0.05). 물리치료 시작시점과 퇴원시의 PS점수 변화와 유의한 관련이 있는 요인은 물리치료 시작시점의 PS점수와 연령이었는데(p<0.05), 물리치료 시작시점의 PS점수가 높고 40세 미만에서 기능호전이 컸다. 물리치료 시작시점과 종료시점 사이의 PS점수 변화와 관련 있는 분수는 물리치료 시작시점의 PS점수, 퇴원 1개월 후에 적극적으로 물리치료를 받았는지의 여부, 연령, 교육수준, 퇴원 후 물리치료 받은 기간, 수술여부 등이었다.(p<0.05). 즉, 물리치료 시작시점의 PS점수가 높고, 퇴원 1개월 후에 적극적으로 물리치료 받은 환자, 연령이 40세 미만, 학력이 높을수록, 퇴원 후 물리치료 받은 기간이 짧은 환자, 그리고 수술을 받지 않은 환자에서 기능호전이 컸다. 퇴원시와 퇴원 1개월 후의 PS점수의 변화는 퇴원시 PS점수가 높고, 학력이 높을수록, 퇴원 1개월 후에 적극적으로 물리치료를 받은 환자, 그리고 퇴원 후 물리치료 기간이 짧고, 남자에서 기능호전이 유의하게 컸다.(p<005). 이상의 결과를 요약하면, 뇌졸중환자의 물리치료 효과를 BI점수로 평가하면 물리치료 시작시점의 BI점수와 연령이 중요한 요인이고, PS점수로 평가하면 역시 물리치료 시작시점의 PS점수와 연령 그리고 교육수준이 중요한 요인으로 생각된다.

• 한국재료학회지
• /
• 제21권10호
• /
• pp.563-567
• /
• 2011

We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.

• Journal of Periodontal and Implant Science
• /
• 제46권4호
• /
• pp.220-233
• /
• 2016

Purpose: The aim of this study was to present new a model that allows the study of the bone healing process, with an emphasis on the biological behavior of different graft-to-host interfaces. A standardized "over-inlay" surgical technique combined with a differential histomorphometric analysis is presented in order to optimize the use of critical-size calvarial defects in pre-clinical testing. Methods: Critical-size defects were created into the parietal bone of 8 male Wistar rats. Deproteinized bovine bone (DBBM) blocks were inserted into the defects, so that part of the block was included within the calvarial thickness and part exceeded the calvarial height (an "over-inlay" graft). All animals were sacrificed at 1 or 3 months. Histomorphometric and immunohistochemical evaluation was carried out within distinct regions of interest (ROIs): the areas adjacent to the native bone (BA), the periosteal area (PA) and the central area (CA). Results: The animals healed without complications. Differential morphometry allowed the examination of the tissue composition within distinct regions: the BA presented consistent amounts of new bone formation (NB), which increased over time ($24.53%{\pm}1.26%$ at 1 month; $37.73%{\pm}0.39%$ at 3 months), thus suggesting that this area makes a substantial contribution toward NB. The PA was mainly composed of fibrous tissue ($71.16%{\pm}8.06%$ and $78.30%{\pm}2.67%$, respectively), while the CA showed high amounts of DBBM at both time points ($78.30%{\pm}2.67%$ and $74.68%{\pm}1.07%$, respectively), demonstrating a slow remodeling process. Blood vessels revealed a progressive migration from the interface with native bone toward the central area of the graft. Osterix-positive cells observed at 1 month within the PA suggested that the periosteum was a source of osteoprogenitor elements. Alkaline phosphatase data on matrix deposition confirmed this observation. Conclusions: The present model allowed for a standardized investigation of distinct graft-to-host interfaces both at vertically augmented and inlay-augmented sites, thus possibly limiting the number of animals required for pre-clinical investigations.