Electrospun Tungsten Oxide Nanofibers: Fabrication and Characterization
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0915-R06-15
Electrospun Tungsten Oxide Nanofibers: Fabrication and Characterization Guan Wang1, Xianrong Huang1, Xiaoqing Yang2, Pelagia-Irene Gouma1, and Michael Dudley1 1 Materials Science and Engineering, Stony Brook University, Stony Brook, NY, 11790 2 Brookhaven National Lab, Upton, NY, 11973 ABSTRACT Tungsten oxide nanofibers have been successfully fabricated in a way based on electrospinning technique. A DMF solution of Poly(Vinyl Acetate)(PVAc, Mw=500,000) was mixed with tungsten isopropoxide to form a viscous precursor solution. Composite nanofibers were obtained by electrspinning this viscous solution. By calcination of the composite fibers, pure tungsten oxide nanofibers were obtained with controllable diameters of around 100 nm. Morphology of the fibers has been characterized by SEM and TEM. The relationship between solution concentration and ceramic nanofiber morphology has been studied. The detailed structure evolution process has been investigated by synchrotron based in-situ XRD. Specific phases of the oxide nanofibers at various calcination temperatures have been obtained from the in-situ XRD spectrum. INTRODUCTION Conductimetric sensors based on semiconducting oxides have been the preferred low cost detectors for reducing gases. The operating principle of these devices is associated primarily with the adsorption of the gas molecules on the surface of semiconducting oxides inducing electric charge transport between the two materials, which changes the resistance of the oxide [1]. In recent researches, there is an increasing trend in the chemical sensing to utilize nanostructured materials as gas sensing elements [2-4], because the use of nanoparticles, nanobelts, and nanofibers in gas sensing can offer very high specific surface areas and unique structural features that are expected to promote the sensitivity of the oxide materials to gaseous components as well as affecting the temperature dependence on sensing. The bulk tungsten oxide exhibits a wide spectrum of fascinating properties, such as catalytic activity, photochromism, electrochromism, semiconductivity [5-6]. These effects are bound up to the features that make a material sensible to gases by modifying the surface conduction bands. This modification comes from a change in the number of free electrons when a gas molecule interacts with a surface layer [7]. Nanoscaled tungsten oxides prepared by sol-gel process have proved to have enhanced sensitivity for the detection of gases such as NOx and NH3. The specificity of the sensors can also be improved [7-9]. However, the traditional sol-gel methods can only prepare discrete nano-scale tungsten oxide crystallites. And there is lack of effective method for the preparation of continuous one-dimensional nanostructured tungsten oxide. Electrospinning represents a relatively simple and versatile method for generating fibular mesostructures [10-12]. This process involves in the production of continuous one-dimensional nanofibers under the electrostatic force of the charges on the surface of a liquid
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