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Lotus, A.F.,Kang, Y.C.,Walker, J.I.,Ramsier, R.D.,Chase, G.G. Elsevier 2010 Materials science and engineering B. Advanced Func Vol.166 No.1
Zinc oxide nanofibers doped with aluminum oxide were prepared by sol-gel processing and electrospinning techniques using polyvinylpyrrolidone (PVP), zinc acetate and aluminum acetate as precursors. The resulting nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy, and current-voltage (I-V) properties. The nanofibers had diameters in the range of 60-150nm. The incorporation of aluminum oxide resulted in a decrease in the crystallite sizes of the zinc oxide nanofibers. Aluminum oxide doped zinc oxide (AOZO) nanofibers exhibited lower bandgap energies compared to undoped zinc oxide nanofibers. However, as the aluminum content (Al/(Al+Zn)x100%) was increased from 1.70at.% to 3.20at.% in the electrospinning solution, the bandgap energy increased resulting in lower conductivity. The electrical conductivity of the AOZO samples was found to depend on the amount of aluminum dopant in the matrix as reflected in the changes in oxidation state elucidated from XPS data. Electrospinning was found to be a productive, simple, and easy method for tuning the bandgap energy and conductivity of zinc oxide semiconducting nanofibers.
Temperature-induced changes in morphology and structure of TiO2–Al2O3 fibers
J.S. Tobin,A.J. Turinske,N. Stojilovic,A.F. Lotus,G.G. Chase 한국물리학회 2012 Current Applied Physics Vol.12 No.3
Electrospinning of a sol-gel and polymer mixture is used to produce titania-alumina (TiO2-Al2O3) fibers with diameters ranging from 200 to 800 nm. These composite metal-oxide fibers were calcined at various temperatures and their morphology is studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The decrease in the average diameter of the fibers with increasing temperature is observed. Powder X-ray diffraction (XRD) reveals that up to 800 ℃ the composite fibers have anatase titania structure whereas at 900 ℃ the fibers exhibit mixture of anatase and rutile phases. It is found that specific surface area decreases as a function of temperature in the 700-900 ℃ range. The change in phase (anatase-to-rutile) and the increase in crystallite size occur simultaneously. The presence of smaller amount of amorphous alumina in the primarily titania-based structure seems to play the role in stabilizing the anatase phase.