702,120 research outputs found

    The Lady in the Harbor and the Lady in Albany

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    Commemorating the 100 year anniversary of Kate Stoneman\u27s entrance into legal practice in the State of New York, the first women to achieve this milestone, Hon. Sol Wachtler hails the achievements of the Task Force on Women and relays its future plans about how, in its continued pursuing of equality, it will help eradicate sexual biases still persisting in the legal industry

    Gelation of n3p3[nh(ch2)3si(oet)3]6-n [x]n x = nh(ch2)3si(oet)3, nch3(ch2)3cn and oc6h4(ch2)cn, n = 0 or 3 at the liquid/air/interface

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    Indexación: ScieloThe compounds N3P3[NH(CH2)3Si(OEt)3]6 (1), N3P3[NH(CH2)3Si(OEt)3]3[NCH3(CH2)3CN]3 (2) and N3P3[NH(CH2)3Si(OEt)3]3 [HOC6H4(CH2)CN]3 (3) undergo slow gelation at the interface oil/air at low temperatures to give perfect gels G1, G2 and G3 respective ly. TEM analysis reveals nanoparticles of silica with mean size of about 10 nm. Pyrolysis under air at 800 °C of these gels affords a mixture of mainly Si5(PO4)6O, SiP2O7 and SiO2. Gelation and pyrolysis products were characterized by IR, solid-state NMR, TEM, SEM-EDAX microscopy and X-ray diffraction. The sol-gel process in the interface liquid /air is discussed in comparison with the usual sol-gel solution process.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072010000300031&nrm=is

    Modification of the Charge ordering in Pr1/2_{1/2}Sr1/2_{1/2}MnO3_{3} Nanoparticles

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    Transport and magnetic properties have been studied in two sets of sol-gel prepared Pr1/2_{1/2}Sr1/2_{1/2}MnO3_{3} nanoparticles having average particle size of 30 nm and 45 nm. Our measurements suggest that the formation of charge ordered state is largely affected due to lowering of particle size, but the ferromagnetic transition temperature (TCT_{C}) remains unaffected.Comment: Accepted in J. Appl. Phy

    Nanostructured titanium dioxide thin film for dye-sensitized Solar cell applications

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    Nanostructured Titanium Dioxide (TiC^) thin film for Dye-Sensitized Solid State Solar Cell (DSSSC) application has been synthesized using sol-gel method and deposited onto silicon and glass substrates using spin coating technique. The optimized annealing temperature and sol-gel concentration were obtained a| 500°C and 0.2M, respectively. Basically, there were four properties studied; surface morphology, structural, electrical and optical properties. Field Emission Scanning Electron Microscopy (FE-SEM) / Scanning Electron microscopy (SEM) were carried out to observe the changes in surface morphology whenever there are changes on the parameters. X-Ray Diffractions (XRD) characterization of the samples was taken to examine the TiC>2 crystalline phases and the intensity of nanocrystalline particles in the thin film. I-V measurement using two-point probe equipment was used to observe the electrical properties which include the measuring of the sheet resistance, the resistivity and the conductivity of the TiC>2 thin film. The optical properties were observed using UV-Vis-NIR spectrophotometer. The thin film transmittance and the band gap energy were also observed using this spectrophotometer. At the end of this research, uniform and homogeneous TiC>2 thin film has successfully prepared. By controlling the sol-gel concentration, a transparent TiC>2 thin film has been developed which has high transmittance property of above 80%. The TiC>2 thin films which were annealed at a temperature of 500°C and prepared at 0.2M of sol-gel precursor concentration gave the optimum results. By adding TiC>2 nanopowder, the surface area and porosity of TiC>2 thin film is improved, thus good candidate to use in DSSSC application

    The sol–gel route: A versatile process for up-scaling the fabrication of gas-tight thin electrolyte layers

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    Sol–gel routes are often investigated and adapted to prepare, by suitable chemical modifications, submicronic powders and derived materials with controlled morphology, which cannot be obtained by conventional solid state chemistry paths. Wet chemistry methods provide attractive alternative routes because mixing of species occurs at the atomic scale. In this paper, ultrafine powders were prepared by a novel synthesis method based on the sol–gel process and were dispersed into suspensions before processing. This paper presents new developments for the preparation of functional materials like yttria-stabilized-zirconia (YSZ, 8% Y2O3) used as electrolyte for solid oxide fuel cells. YSZ thick films were coated onto porous Ni-YSZ substrates using a suspension with an optimized formulation deposited by either a dip-coating or a spin-coating process. The suspension composition is based on YSZ particles encapsulated by a zirconium alkoxide which was added with an alkoxide derived colloidal sol. The in situ growth of these colloids increases significantly the layer density after an appropriated heat treatment. The derived films were continuous, homogeneous and around 20 μm thick. The possible up-scaling of this process has been also considered and the suitable processing parameters were defined in order to obtain, at an industrial scale, homogeneous, crack-free, thick and adherent films after heat treatment at 1400 °C

    Synthesis by sol–gel route of oxyapatite powders for dense ceramics : applications as electrolytes for solid oxide fuel cells

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    Solid oxide fuel cells have considerable interest in recent years, because of their high efficiency and environmentally friendly nature. Such systems required oxygen-conducting electrolytes and now the most common electrolyte is yttria stabilized zirconia (YSZ). This compound exhibits high oxide ion conductivity at elevated temperatures (850–1000 °C). However, this high working temperature causes problems in terms of materials selection and lifetime. One solution is to develop new oxide ions conductors exhibiting high oxide ion conductivity at intermediary temperatures (700–800 °C). Recent work has identified Ln10−xSi6O26±z (Ln = rare earths) as a good fast oxide ion conductor. Undoped and doped Ln10−xB6O26±z (B = Si or Ge) oxides are currently prepared by solid-state methods. In that work, we propose a sol–gel process to synthesize powders of La9.33Si6O26 type-silicated apatites. The main advantage is to decrease the crystallization temperature in ,comparison to the conventional methods, allowing the synthesis of reactive powders with nanometric particles size. These oxides are synthesized using silicon alkoxide and lanthanum nitride as precursors. In the litterature, no study refers to the synthesis of mixed oxides with silicon alcoxides. However, there are several studies on sol–gel synthesis of glasses with this precursor. In this study, several processing parameters have been investigated (the hydrolysis ratio, the concentration of metallic precursors in the sol and the role of organic compounds) in order to synthesize pure phases after the decomposition of the sols. Pure powders of La9.33Si6O26 type-silicated apatites are obtained at 800 °C. These powders were used to prepare ceramics. Several processing parameters as morphology of powders (agglomeration, particle sizes) and, heating profiles have been studied on the densification. Dense ceramics (90–95%) have been prepared at temperatures around 1400 °C. The used of sol–gel powders allow the decrease of the sintering temperature of about 200 °C

    The synthesis of thermochemically stable single phase lanthanum titanium aluminium oxide

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    Lanthanum titanium aluminium oxide (LaTi2Al9O19, LTA) synthesized by solid state reaction has been proven to be a promising thermal barrier material. However, LTA synthesized via solid state reaction requires a high processing temperature of at least 1500 °C for 24 h. In this paper, single phase LTA was synthesized by sol–gel at a lower temperature (1350 °C) and the process parameters, phase composition, and relative thermal properties were investigated. Two-step calcination was used to obtain fine LTA powders. According to X-ray diffraction, the best calcination temperature of sol–gel synthesized LTA is 1350 °C. XRD results also showed the thermochemical stability of sol–gel synthesized LTA, which does not react with Al2O3 up to 1500 °C, to be excellent. Compared to LTA synthesized by solid state reaction, sol–gel synthesized LTA has higher coefficients of thermal expansion (CTEs) which are circa 10.2×10−6 °C−1 at 950 °C, related to the size dependent characteristic of CTEs. Therefore, sol–gel synthesized LTA can be a promising candidate as a thermal barrier material on Ni-based superalloys
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