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반용융 성형가공한 SiCp / AZ91HP Mg 복합재료의 피로 및 내마모 특성
하홍수,김명균,안선규,임병수,김영직 ( Hong Soo Ha,Myoung Gyun Kim,Sun Kyu Ahn,Byeong Soo Lim,Young Jig Kim ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.5
N/A The effect of size and mass fraction of SiC particulate on the fatigue and wear have been investigated for semi-liquid formed SiCp/AZ91HP Mg composites. In the study, different particulate sizes of 7, 20, 50 ㎛ were prepared with various mass fraction for sample preparation. By tension-tension fatigue tests, whose procedures are standardized in ASTM standard 647E-93, the da/dN vs. ΔK curves were obtained. Also, the crack propagation paths were observed by optical microscope. As a result of wear test, specific wear loss is decreased with increasing mass fraction and particulate size. Specific wear loss of 30 mass% 50 ㎛ SiC reinforced Mg composite is compared to SKD11. (Received July 21, 1997)
내부 확산법에 의한 Nb$_3Sn$ 초전도 선재에서 부분 가열이 초전도 특성에 미치는 영향
하동우,오상수,하홍수,이남진,권영길,류강식,Ha, Dong-Woo,Oh, Sang-Soo,Ha, Hong-Soo,Lee, Nam-Jin,Kwon, Young-Kil,Ryu, Kang-Sik 한국초전도저온공학회 2000 한국초전도저온공학회논문지 Vol.2 No.2
There is the possibility that internal tin processed Nb$_3Sn$ wires are locally heated during the drawing process and the jacketing process. It is important to know the variations in J$_c$ of internal tin processed Nb$_3Sn$ wires caused by local heating. Internal tin processed Nb$_3Sn$ rods were cold worked to 2.28 mm, using the appropriate reduction ratio, and then cut into several pieces. At this stage, wires were locally 50 mm heat zone heated up to 360$^{\circ}C$. The locally heated Nb$_3Sn$ wires were drawn to a final diameter size of 0.81 mm. Others were cold worked successively to 0.81 mm and locally heated with the same conditions. 2 types of locally heat treated wires were wound on Ti-6Al-4V barrels and heat treated for the Nb$_3Sn$ reaction. Local heating of internal tin processed Nb$_3Sn$ wires after the J$_c$ of these wires. However, local heating at an intermediate stage of the drawing process caused a decrease in J$_c$. When the local heating temperatures were higher than melting point of Sn, non-Cu J$_c$'s decreased significantly. A Sn-Cu alloyed boundary appeared after local heating over the melting point of Sn, and caused work hardening and a decrease in the workability.
RABiTS 위에 PLD 방법으로 증착된 YBCO 초전도 박막 선재의 제조
고락길,정준기,하홍수,김호섭,송규정,박찬,문승현,유상임,김영철,Ko Rock-Kil,Shi Dongqi,Chung Jun-Ki,Ha Hong-Soo,Kim Ho-Soup,Song Kyu-Jeong,Park Chan,Moon Seung-Hyun,Yoo Sang Im,Kim Young-Cheol 한국초전도학회 2004 Progress in superconductivity Vol.6 No.1
YBCO coated conductor is one of the most promising materials as a new generations wire especially for practical power applications. In this work, $YBa_2$$Cu_3$$O_{7}$ -$\delta$/(YBCO) coated conductors (CC) were deposited by pulsed laser deposition (PLD) from buffer layers to superconducting layer on hi-axially textured metal tape. The oxide multilayer buffered substrate of architectures of $CeO_2$/$YSZ/Y_2$$O_3$ was fabricated by PLD at steady status. Then YBCO layer was deposited on RABiTS substrate by stationary and reel-to-reel (R2R) continuous process and we compared with deposition conditions of both processes. The degree of texture of each layer was investigated using X-ray diffraction including $\theta$-2$\theta$ scans, $\omega$-scans and $\Phi$-scans analysis. Their surface morphology was observed by scanning electron microscopy (SEM). The FWHM of the X-ray $\Phi$-scans and $\Phi$-scans indicated that YBCO and buffer layers closely replicate the in-plane and out-of-plane texture of metal tape. Critical current (Ic) at 77 K, self-field of 75.8 A/cm-width, critical temperature (Tc) of 85 K, and critical current density (Ic) of 3.7 MA/$\textrm{cm}^2$ were measured from coated conductor deposited by stationary process. And coated conductor deposited by R2R continuous process had Ic of 57.5 A/cm-width, Tc of 86.5 K and Jc of 2.0 MA/$\textrm{cm}^2$. The film also exhibits a homogeneous and dense surface morphology.
연속 공정 PVD 방법에 의한 Coated Conductor 제조
고락길,정준기,김호섭,하홍수,송규정,박찬,유상임,문승현,김영철,Ko, Rock-Kil,Chung, Jun-Ki,Kim, Ho-Sup,Ha, Hong-Soo,Shi, Dongqi,Song, Kyu-Jeong,Park, Chan,Yoo, Sang-Im,Moon, Seung-Hyun,Kim, Young-Cheol 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.11
Continuous physical vapor deposition (PVD) method is one of many processes to fabricate long length coated conductor which is required for successful large-scale application of superconducting power devices. Three film deposition systems (pulsed laser deposition, sputtering, and evaporation) equipped with reel-to-reel(R2R) metal tape moving apparatus were installed and used to deposit multi-layer oxide thin films. Both RABiTS and IBAD texture templates are used. IBAD template consists of CeO$_2$(PLD)/YSZ(IBAD) on stainless steel(SS) metal tape, and RABiTS template has the structure of CeO$_2$/YSZ/Y$_2$O$_3$ which was continuously deposited on Ni-alloy tape using R$_2$R evaporation and DC reactive sputtering in a deposition system designed to do both processes. 0.4 m-long coated conductor with Ic(77 K) of 34 A/cm was fabricated using RABiTS template. 0.5 m and 1.1 m-long coated conductor with Ic(77 K) of 41 A/cm and 26 A/cm were fabricated using IBAD template.
SmBCO 초전도 층착을 위한 RABiTS상의 CeO<sub>2</sub> 단일 버퍼 연구
김태형,김호섭,이남진,하홍수,고락길,하동우,송규정,오상수,박경채,Kim, Tae-Hyung,Kim, Ho-Sup,Lee, Nam-Jin,Ha, Hong-Soo,Ko, Rock-Kil,Ha, Dong-Woo,Song, Kyu-Jeong,Oh, Sang-Soo,Park, Kyung-Chae 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.6
As a rule, high temperature superconducting coated conductors have multi-layered buffers consisting of seed, diffusion barrier and cap layers. Multi-buffer layer deposition requires longer fabrication time. This is one of main reasons which increases fabrication cost. Thus, single buffer layer deposition seems to be important for practical coated conductor process. In this study, a single layered buffer deposition of $CeO_2$ for low cost coated conductors has been tried using thermal evaporation technique. 100 nm-thick $CeO_2$ layers deposited by thermal evaporation were found to act as a diffusion layer. $1\;{\mu}m-thick$ SmBCO superconducting layers were deposited by thermal co-evaporation on the $CeO_2$ buffered Ni-5%W substrate. Critical current of 90 A/cm was obtained for the SmBCO coated conductors.
초전도 테이프 제작을 위한 니켈기판 상의 산화물 박막 증찰
김호섭,고락길,정준기,하홍수,송규정,박찬,Kim, Ho-Sup,Shi, Dongqui,Ko, Rock-Kil,Chung, Jun-Ki,Ha, Hong-Soo,Song, Kyu-Jeong,Park, Chan 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.12
High temperature superconducting coated conductor has a structure of <protecting layer>/<superconducting layer>/<buffer layer>/<metallic substrate>. The buffer layer consists of multi-layer, this study reports the deposition method and optimal deposition conditions of YSZ(Yttria-stabilized zirconia) layer which plays a important part in preventing the elements of substrate from diffusing into the superconducting layer. YSZ layer was deposited by DC reactive sputtering technique using water vapor for oxidizing deposited elements on substrate. To investigate optimal thickness of YSZ film, four YSZ/CeO$_2$/Ni samples with different YSZ thickness(130 nm, 260 nm, 390 nm, and 650 nm) were prepared. The SEM image showed that the surface of YSZ layer was getting to be rougher as YSZ layer was getting thicker and the growth mode of YSZ layer was columnar grain growth. After CeO$_2$ layer was deposited with the same thickness of 18.3 nm on each four samples, YBCO layer was deposited by PLD method with the thickness of 300 nm. The critical currents of four samples were 0, 6 A, 7.5 A, and 5 A respectively. This shows that as YSZ layer is getting thicker, YSZ layer plays a good role as a diffusion barrier but the surface of YSZ layer is getting rougher.
위상차를 갖고 변화하는 자기장과 전류가 동시에 가해진 $Sm_1Ba_2Cu_3O_{7-\delta}$ Coated Conductor의 자기이력 손실
이상무,정예현,곽기성,이준규,유재은,염도준,김호섭,하홍수,오상수,Lee, Sang-Moo,Jung, Ye-Hyun,Kwak, Ki-Sung,Rhee, Joon-Kyu,Yoo, Jae-Un,Youm, Do-Jun,Kim, Ho-Sup,Ha, Hong-Soo,Oh, Sang-Soo 한국초전도학회 2009 Progress in superconductivity Vol.10 No.2
The magnetic field profiles near the surface of a $Sm_1Ba_2Cu_3O_{7-\delta}$ coated conductor(CC-tape) under magnetic field and current that were applied simultaneously with phase differences ${\phi}s$ were measured using scanning Hall probe method. Measurements were carried out along the elliptic load lines with $\phi=90^{\circ}\;and\;45^{\circ}$ for some $B_{peak},\;I_{peak}$ values. From the measured field profiles, sheet current density J(x, $B_a,\;I_a$) and magnetic flux density $B_0(x,\;B_a,\;I_a)$ profiles in the CC-tape were calculated. Using these J(x, $B_a,\;I_a$) and $B_0(x,\;B_a,\;I_a)$ profiles, we estimated the hysteresis energy loss Q in the CC-tape. The estimated Qs, together with our previous results for $\phi=0^{\circ}$ from [9], were compared with theoretical values based on Brandt's calculation.
Y<sub>2</sub>Ba<sub>1</sub>Cu<sub>1</sub>O<sub>x</sub>공정을 이용한 TFA-MOC YBCO 박막 공정 개발
임준형,장석헌,김규태,이진성,윤경민,하홍수,주진호,나완수,Lim, Jun-Hyung,Jang, Seok-Hern,Kim, Kyu-Tae,Lee, Jin-Sung,Yoon, Kyung-Min,Ha, Hong-Soo,Joo, Jinho,Nah, Wansoo 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.2
YBCO film was synthesized by using a new approach to the TFA-MOD method. In the fabrication process, $Y_2Ba_1Cu_1O_x\;and\;Ba_3Cu_5O_8$ powders were used as precursors (the so called '211 process'), instead of Y-, Ba-, and Cu-based acetates, and dissolved in trifluoroacetic acid followed by calcining and firing heat treatment. Consequently, we successfully fabricated YBCO film and evaluated the phase formation, texture evolution, and critical properties as a function of the calcining and firing temperature and humidity, in order to explore its possible application in coated conductor fabrication. The films were calcined at $430-460^{\circ}C$ and then fired at $750-800^{\circ}C\;in\;a\;0-20\%$ humidified $Ar-O_2$ atmosphere. We observed that $BaF_2$ phase was effectively reduced and that a sharp and strong biaxial texture formed under humidified atmosphere leading to increased critical properties. In addition, we found that the microstructure varied significantly with the firing temperature: the grain grew further, the film became denser, and the degree of texture and phase purity varied as the firing temperature increased. For the film fired at $775^{\circ}C$ after calcining at $460^{\circ}C$, the critical current was obtained to be 39 A/cm-width (corresponding critical current density is $2.0\;MA/cm^2$ which was probably attributed to such factors as the enhanced phase purity and out-of-plane texture, the moderate film density and grain size, and crack-free surface.