Santiago-Aviles, Jorge J

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Author: Ramos, Idalia ×

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  • Publication
    Tin oxide micro/nano fibers from electrostatic deposition
    (2006-02-01) Wang, Yu; Aponte, M.; Leon, N.; Ramos, Idalia; Furlan, Rogerio; Pinto, N.; Santiago-Aviles, Jorge J
    SnO2 micro/nano fibers in the rutile structure were synthesized using electrospinning and metallorganic decomposition techniques. Fibers were electrospun using two different precursor solutions, one based on SnCl4 and the other on C22H44O4Sn. The fibers were sintered in air for two hours at 400, 500, 600, 700 and 800ºC. SEM, AFM, XRD, XPS and Raman microspectrometry were used to characterize the sintered fibers. The results showed that the fibers were composed of SnO2 and that the SnCl4 precursor led to better results in terms of uniformity/continuity of the fibers.
  • Publication
    Detection of Moisture and Methanol Gas Using a Single Electrospun Tin Oxide Nanofiber
    (2007-09-01) Wang, Yu; Ramos, Idalia; Santiago-Aviles, Jorge J
    This letter reports the fabrication of a gas sensor based on a single tin oxide nanofiber made from dimethyldineodecanoate tin using electrospinning and metallorganics decomposition techniques. The fabricated sensor has been used to detect moisture and methanol gas. It showed high sensitivity to both gases and the response times of the complete testing system are in the range of 108–150 s for moisture, and 10–38 s for methanol gas, respectively.
  • Publication
    Electronic Transport Properties of Incipient Graphitic Domains Formation in PAN Derived Carbon Nanofibers
    (2004-03-01) Wang, Yu; Ramos, Idalia; Santiago-Aviles, Jorge J; Furlan, Rogerio
    The carbon nanofibers used in this work were derived from a polyacrylonitrile (PAN)/N, N-dimethyl formamide (DMF) precursor solution using electrospinning and vacuum pyrolysis techniques. Their conductivity, σ, was measured at temperatures between 1.9 and 300 K and transverse magnetic field between -9 and 9 T. Zero magnetic field conductivity σ(0,T) was found to increase monotonically with the temperature with a convex σ(0,T) versus T curve. Conductivity increases with the external transverse magnetic field, revealing a negative magnetoresistance at temperatures between 1.9 and 10 K, with a maximum magnetoresistance of - 75 % at 1.9 K and 9 T. The magnetic field dependence of the conductivity and the temperature dependence of the zero-field conductivity are best described using the two-dimensional weak localization effect.
  • Publication
    Pyrolysis Temperature and Time Dependence of Electrical Conductivity Evolution for Electrostatically Generated Carbon Nanofibers
    (2003-03-01) Wang, Yu; Santiago-Aviles, Jorge J; Furlan, Rogerio; Ramos, Idalia
    Carbon nanofibers were produced from polyacrylonitrile/N, N-Dimethyl Formamide (PAN/DMF) precursor solution using electrospinning and vacuum pyrolysis at temperatures from 773-1273 K for 0.5, 2, and 5 h, respectively. Their conductance was determined from I – V curves. The length and cross-section area of the nanofibers were evaluated using optical microscope and scanning probe microscopes, respectively, and were used for their electrical conductivity calculation. It was found that the conductivity increases sharply with the pyrolysis temperature, and increases considerably with pyrolysis time at the lower pyrolysis temperatures of 873, 973, and 1073 K, but varies, less obviously, with pyrolysis time at the higher pyrolysis temperatures of 1173 and 1273 K. This dependence was attributed to the thermally activated transformation of disordered to graphitic carbons.
  • Publication
    Optical Bandgap and Photoconductance of Electrospun Tin Oxide Nanofibers
    (2007-11-01) Wang, Yu; Ramos, Idalia; Santiago-Aviles, Jorge J
    Optical and photoconductive properties of transparent SnO2 nanofibers, made from C22H44O4Sn via electrospinning and metallorganic decomposition, were investigated using Fourier transform infrared and ultraviolet (UV)/visible spectrometry and the two-probe method. Their optical bandgap was determined from their UV absorption edge to be 3.95–4.08 eV. Their conductance responds strongly to UV light for a wavelength of 254 nm: in air its steady-state on-to-off ratios are 1.31–1.56 (rise) and 1.25–1.33 (fall); its 90% rise and fall times are 76–96 and 71–111 s, respectively. In a vacuum of about 10−4 torr, its on-to-off ratios are higher than 35.6 (rise) and 3.4 (fall), respectively, and its 90% rise and fall times are longer than 3×104 s.