Yukiko Takahashi

Firing condition for entire reactions of fluorides with water vapor in metalorganic deposition method using trifluoroacetate

To obtain the YBa 2 Cu 3 O 7-x (YBCO) film on buffered metal tapes, we have to fire films below 800°C and avoid formation of BaF 2 in the films which leads to low J c by metalorganic deposition using trifluoroacetate method. By estimating each process condition to reaction rate of fluorides with water vapor in precursor, we can established firing profile for YBCO film on buffered metal substrate at 725°C. With the profile, we can successfully obtained YBCO film on CeO 2 /YSZ/hastelloy, which has critical current density (J c ) of 1.72 MA/cm 2 (77 K, 0 T) and thickness of 1860 A.

Fabrication and characterization of a α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine/silica nanocomposite thin-layer membrane for detection of ppb-level heavy metal ions

A new detection membrane for filtration enrichment combined with colorimetric determination of Cd(II), Zn(II), Pb(II) and Cu(II) ions is presented. We have demonstrated the use of a dye nanoparticle coated test strip (DNTS) structured with a reagent layer for on-site analysis of trace metal ions. In this study, a [TMPyP/SA] DNTS coated with a nanocomposite layer (average thickness: 5.39 μm) of α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) and silica-SA on the top surface of a cellulose ester membrane filter was fabricated by a simple filtration of an aqueous TMPyP/silica-SA nanocomposite dispersion through a membrane filter. The nanocomposite formation of cationic TMPyP and negatively charged colloidal SA (9-80 nm) was based on electrostatic interaction and was confirmed in the 120-800 nm diameter range by a dynamic light scattering photometer (DLS). To optimize the DNTS nanocomposite layer, surface uniformity, mechanical strength, the percent retention of TMPyP, and sensitivity to Cd(II) detection for six DNTSs with five different types of silica were examined. A half[TMPyP/SA] DNTS with an average layer thickness of 2.60 μm, which was prepared by controlling the amount of TMPyP and SA, demonstrated the highest sensitivity to Cd(II) ion because it had the lowest background absorbance. In addition, factors that affected the percent retention of TMPyP, such as pH and TMPyP/SA ratio, were determined. More than 99% of the TMPyP was retained on a membrane filter at pH 7.8 with a TMPyP and SA concentration of 2 × 10(-5) M and 4 × 10(-5) wt%, respectively. Filtration enrichment of 100mL of an aqueous solution containing Cd(II), Zn(II), and Pb(II) at ppb levels was achieved by concentrating the metal ions in a nanocomposite layer (the effective TMPyP area was 1.77 cm(2), pH 10.2). The signaling surface changed from a brown color to green when the ions were captured. The percent extraction for metal ions on a half[TMPyP/SA] DNTS were estimated by TLC scanning and ICP-MS. It was observed that, when using the half[TMPyP/SA] DNTS, Cd(II) concentrations as low as 1 ppb were detectable at a filtration rate of 4.0-5.0 mL min(-1).

Preparation of bi-axially aligned YBa2Cu3O7−δ film on CeO2-buffered MgO by chemical solution deposition

Abstract We have succeeded in preparing in-plane aligned YBa 2 Cu 3 O 7− δ (Y123) film by chemical solution deposition (CSD) processing on CeO 2 (100)-buffered MgO (100) substrates. The CeO 2 buffer film was deposited on MgO (100) single crystalline substrate by pulsed laser deposition (PLD). For CSD coating, a homogeneous coating solution having a molar ratio of Y:Ba:Cu=1:2:3, was prepared by dissolving metal naphthenates in toluene. This solution was spin-coated both on the YSZ (100) and on the CeO 2 -buffered MgO (100) single crystalline substrates. The precursor films were calcined at 425°C and fired at various temperatures under low oxygen partial pressure ( p O 2 ). All Y123 films showed strong (00 n ) peaks, which correspond to c -axis orientation perpendicular to the substrates and their a / b -axes were in-plane aligned. We confirmed that CeO 2 buffer is usable for CSD processing. While the Y123 films on the YSZ reacted with the substrate forming BaZrO 3 phase and did not show sufficient superconducting properties. The T c,zero value of the Y123 film prepared on CeO 2 -buffered MgO substrate was 91.5 K and J c was 1.2×10 5 A/cm 2 at 77 K, 0 T.

YBCO thin films on multilayers prepared by all-chemical solution deposition processing

Abstract The chemical solution deposition (CSD) technique has been applied to prepare both YBa 2 Cu 3 O 7− δ (YBCO) and buffer layers on a YSZ substrate. Y 2 O 3 and CeO 2 were employed as the buffer layers, and it was confirmed that they grew epitaxially by the CSD method. Cross-sectional transmission electron microscope observations revealed that Y 2 O 3 grew up to the top of the film. Furthermore, the YBCO film on the Y 2 O 3 or CeO 2 /Y 2 O 3 layers were c -axis aligned and showed a good in-plane alignment. The transition temperature and the critical current density of the YBCO/Y 2 O 3 /YSZ multilayer were 89 K and 4×10 4 A/cm 2 at 77 K, 0 T, respectively.