• 제목/요약/키워드: T1-1223

검색결과 14건 처리시간 0.028초

Tl-1223 다결정 초전도체의 자기적 특성 (Magnetic properties of polycrystalline Tl-1223 superconductor)

  • 백련;이준호;김영철;정대영
    • Progress in Superconductivity
    • /
    • 제6권1호
    • /
    • pp.41-45
    • /
    • 2004
  • Polycrystalline Tl-1223 superconductors with a chemical composition of (Tl, Pb, Bi)TEX>$ (Sr, Ba)<_2$$Ca_2$$Cu_3$$O_{x}$ were synthesized by the solid state reaction method. The optimum chemical composition was $Tl_{0.8}$ $Pb_{0.2}$ $Bi_{0.2}$ $Sr_{1.8}$ $Ba_{0.2}$ $Ca_{2.2}$ $Cu_3$$O_{x}$ And the optimum sintering temperature and time were $905^{\circ}C$ and 7.5h, respectively. The sample was evaluated for their superconducting properties by magnetization measurement. The critical temperature $T_{c}$ is 120 K and the critical current density $J_{c}$ (T=5K, 0T) is estimated to be ∼ $10^{5}$ A/$\textrm{cm}^2$ for $Tl_{0.8}$ $Pb_{0.2}$ $Bi_{0.2}$ $Sr_{1.8}$ $Ba_{0.2}$ $Ca_{2.2}$$Cu_3$$O_{x}$ .

  • PDF

Enhanced Densification in Tl-1223/Ag Tapes Prepared Using Pretreated Precursors

  • 정대영;백상민;김봉준;김영철;박기곤
    • Progress in Superconductivity
    • /
    • 제3권2호
    • /
    • pp.198-212
    • /
    • 2002
  • The effects of reacted precursors on phase evolution, microstructure, $J_{c}$ and junctional characteristic of the inter-granular contacts were investigated in Ag-sheathed T1-1223 tapes prepared using three kinds of reacted precursors, and compared to those in the tape prepared using an unreacted precursor The precursors were prepared by heat-treating a mixture of Sr-Ba-Ca-Cu-O, $Tl_2$$O_3$, PbO and $Bi_2$$O_3$ powders at $805^{\circ}C$ (precursor I ), $840^{\circ}C$ (precursor II ) and $905^{\circ}C$(precursor III) for 20 min. Tl-1223 phase content, grain size and J\ulcorner in the tapes appeared to increase in an order of precursors I, II and III Compared to tapes prepared using an unreacted precursor, the tapes prewar ed using precursors II and III revealed reduced pore and impurity densities and an enhanced texture. Also characteristic of inter -granular contacts and fraction of strong-links were improved. The improved properties are attributed to enhanced densification resulting from using the reacted precursors.s.

  • PDF

고온 초전도체 $Hg_{1-x}\;Tl_{x}\;Ba_{2}(Ca_{0.86}\;Sr_{0.14})_{2}\;Cu_{3}\;O_{8+\delta}$의 고분해능 TEM에 의한 구조 관찰 (High Resolution TEM Observations in $Hg_{1-x}\;Tl_{x}\;Ba_{2}(Ca_{0.86}\;Sr_{0.14})_{2}\;Cu_{3}\;O_{8+\delta}$ Superconductors)

  • 이확주;류현;허남회;박용기
    • Applied Microscopy
    • /
    • 제25권4호
    • /
    • pp.124-131
    • /
    • 1995
  • 이상과 같은 실험결과를 다음과 같은 요약할 수 있다. 1) $Hg_{1-x}\;Tl_{x}\;Ba_{2}(Ca_{0.86}\;Sr_{0.14})_{2}\;Cu_{3}\;O_{8+\delta}$의 구조는 Hg-1223과 같은 구조를 이루며 Hg 위치에 T1이 치환되어 있음을 알 수 있다. 2) 격자상수는 탈륨이 증가할수록 감소하는 경향을 나타냈으나 x=0.25 시료에서는 현저히 감소됨을 보였다. 3) x=0.25 시료에서는 적층 결함 1234구조가 1223구조와 intergrowth함을 보였고 불순물 상이 다소 나타났다. 4) 탈륨이 증가할 수록 보다 치밀하고 결함이 없는 안정된 조직을 보였다. 5) 모든 시료가 관찰 도중 전자빔에 대하여 손상되었으나 탈륨의 양이 증가할 수록 손상에 대한 저항이 커져 보다 안정된 상을 보였다.

  • PDF

Effect of weak interlayer coupling on critical fluctuation in high $T_c$ superconductors

  • Kim, Jin-Tae;Kang, W.N.;Chung, S.H.;Ha, D.H.;Yoo, K.H.;Kim, M.S.;Lee, Sung-Ik;Park, Y.K.;Park, J.C.
    • Progress in Superconductivity
    • /
    • 제1권1호
    • /
    • pp.1-8
    • /
    • 1999
  • The magnetization and/or resistivity of high $T_c$ superconductors ($YBa_2Cu_3O_{7-\delta}$(YBCO) single crystal, $Bi_2Sr_2CaCu_2O_8$ (Bi-2212) single crystal, $Tl_2Ba_2CaCu_2O_8$ (Tl-2212) film, $HgBa_2Ca_2Cu_3O_8$ (Hg-1223) film) have been measured as a function of magnetic field H and temperature T. The extracted fluctuation part of the magnetization and conductivity exhibits a critical behavior consistent with the three-dimensional XY model. The dynamic critical exponent z does not sensitively vary with a type of the superconductors. The value of z ranges from 1.5 to $1.8{\pm}0.1$. However, the static critical exponent ${\nu}$ is the most largely increased in Tl-2212 that has a weaker interlayer coupling strength than YBCO; the value of ${\nu}$ is 0.669, 0.909, 1.19, and 1.338 for YBCO, Bi-2212, Hg-1223, and Tl-2212 respectively. The results indicate that the weak interlayer coupling along the c-axis of high $T_c$ superconductors near $T_c$ does not influence the dynamic critical exponent z (the same value of superfluid $^4He$), but significantly increases the static critical exponent ${\nu}$.

  • PDF

Comparison of microstructures in T1-1223/Ag tapes with different chemical compositions and J$_c$'s

  • Jeong, D.Y.;Kim, H.K.;Lee, H.Y.;Cha, M.K.;Ha, H.S.;Oh, S.S.;Tsuruta, T.;Horiuchi, S.
    • 한국초전도학회:학술대회논문집
    • /
    • 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
    • /
    • pp.280-290
    • /
    • 1999
  • The microstructures of a Tl$_{0.8}Pb_{0.2}Bi_{0.2}Sr_{1.6}Ca_2Cu_3O_{9+{\delta}}$/Ag tape (tape I ) with J$_c$ of 17,600 A/cm$^2$ at 77 K and 0 T and three Tl$_{0.8}Pb_{0.2}Bi_{0.2}Sr_{1.8}Ba_{0.2}Ca_{2.2}Cu_3O_{9+{\delta}}$/Ag tapes with J$_c$'s of 9,300 (tape II), 16,700 (tape III) and 25,200 A/cm$^2$ (tape IV)prepared using the powder-in-tube method and an in-situ reaction method, were investigated using scanning electron microscopy and high-resolution transmission electron microscopy, and compared each other. ln the tape preparation, an intermediate rolling process was incorporated during final heat-treatment for the last tape, but not for the rest of the tapes. The microstructural analysis revealed clear differences in grain-texturing, crystallographic defects and impurity phases, depending on the chemical composition of the tape. Tendency of directional grain-alignment increased in an order of tapes I, II III and IV. In tape IV, T1-1223 grains are textured, at least in local regions. In crystallographic defects, while stacking faults were prevalent in the former composition, dislocations and voids were frequently observed in the latter. Also impurity phases were appeared to be more abundant in the former than in the latter. The relationship between 1,and the microstructure in the tapes was attempted to explain in a term of grain-linking.

  • PDF

Synthesis of 6-[2-(Benzoxazol-2-ylmethylamino )ethoxy]-1-Alkyl­1 H-lndole-2-Carboxylic Acid and Inhibitory Activity on $\beta$-Amyloid Aggregation

  • Lee, Sun-Mi;Jeon, Raok
    • Archives of Pharmacal Research
    • /
    • 제28권11호
    • /
    • pp.1219-1223
    • /
    • 2005
  • 6-[2-(Benzoxazol-2-ylmethylamino)ethoxy]-1-alkyl-1H-indole-2-carboxylic acids were designed and synthesized as $\beta$-amyloid (A$\beta$) fibril assembly inhibitors. Their inhibitory activity on A$\beta$, aggregation was evaluated by thioflavin T assay although their activities were insignificant.

청심온담탕의 면역조절 효과 (Immuno-Regulatory Effects of Cheongsimondam-tang)

  • 박민철;진재호;정한솔;이광규
    • 동의생리병리학회지
    • /
    • 제16권6호
    • /
    • pp.1223-1229
    • /
    • 2002
  • The purpose of this research was to investigate the effect of Cheongsimondam-tang(CSODT) on the activity of immune cell and anti-carcinogenic effect of mouse leukemia cell. The addition of CSODT(1 ㎍/ml) enhanced the proliferation of cultured-splenocytes and thymocytes. And also administration of CSODT(500 ㎍/kg) accelerated subpopulation of splenic and thymic T lymphocytes especially CD4/sup +/-T/sub H/ cells in BALB/c mice. CSODT treatment decreased cell proliferation and increased apoptotic cell death of cultured-L1210 leukemia cells, and induced apoptosis in addition to decreased mitochondrial transmembrane potential (ΔΨm) of transplanted-L1210 cells in vivo. These results suggest that CSODT have a cellular immuno-regulatory effect and anti-cancer property action.

음성의 청각특성을 이용한 화자식별시스템의 성능향상에 관한 연구 (On a Performance Improvement of Speaker Recognition by using the Auditory Characteristics of Speech)

  • 이윤주;오세영배재옥배명진
    • 대한전자공학회:학술대회논문집
    • /
    • 대한전자공학회 1998년도 추계종합학술대회 논문집
    • /
    • pp.1223-1226
    • /
    • 1998
  • The pre-emephasis filter as the conventional method emphasizes all components of high frequency that reflects the speaker characteristics. However this filter don't show the auditory characteristics of speaker's speech. In order to emphasize the perceptual characteristics, we propose the speaker recognition system that uses the perceptual weighting as the preprocessor because the Auditory characteristic of human is sensitive to the formant peaks. This filter has the characteristcs that both deemphasizes the low-formants and emphasizes the high formants. As a result of the proposed method, we improve the total recognition rate 1.7% better than the conventional method.

  • PDF

Sol-gel 법에 의한 고온 초전도체 $YBa_2Cu_3O_{7-{\sigma}}$ 선재 합성에 관한 연구 (High Tc Superconductor Fiber $YBa_2Cu_3O_{7-{\sigma}}$ Synthesized by the Sol-gel Process)

  • 최진호;유종석;김배환;홍승태
    • 대한화학회지
    • /
    • 제33권3호
    • /
    • pp.326-331
    • /
    • 1989
  • Sol-gel법으로 고온 초전도체인 $YBa_2Cu_3O_{7-{\sigma}}$의 세선을 제작하였다. Y, Ba, Cu 질산염을 1:2:3의 몰비로 수용액을 제조한 후 구연산 수용액을 첨가하고, 암모니아 수용액을 첨가하여 pH를 $5.8{\sim}6.2$로 조절함으로써 균일한 colloid sol을 제조할 수 있었다. 이를 358K 로 가열하면 점차 점도가 증가하면서 gel화 반응이 진행되고 이 gel화 반응이 완결되기 전에 구연산염 precursor gel fiber를 임의의 길이 및 두께로 뽑을 수 있었다. 이 precursor를 1223K, $Po_2$=1atm. 하에서 8시간 열처리한 후 723K로 서냉하고 13시간 동안 annealing 하여 약 95K에서 전기저항이 급격히 감소($T_c$, onset), 약 82K에서는 저항 0($T_c$, offset)을 나타내었고 액체질소 비등점에서 Meissner-effect를 보임으로써 초전도체 임을 확인하였다.

  • PDF