Abstract
Metal oxide hollow fiber was prepared by combination of a polymer template and atomic layer deposition (ALD) technique. Polysulfone hollow fibers with outer and inner diameters of ~300 μm and ~200 μm, respectively, were used as a template to be deposited with metal oxides such as TiO2, Al2O3, and ZnO. In the ALD process, TiCl4, trimethylaluminum (TMA), diethylzinc (DEZ), and H2O were chosen as precursors. Then metal oxide thin films were directly deposited on the polysulfone hollow fiber at a relatively low temperature (room temperature and 100 oC). The optimal condition of ALD was investigated. The wall thickness of the nanotubes could be precisely controlled in molecular scale by tuning the cycle number of ALD. The relationship between thickness and strength of the metal oxide structure was studied. The coated hollow fibers were then heated to remove the polysulfone. TGA analysis was used to examine the parameters for removal of template, and SEM was used to confirm it. After removal of template, metal oxide hollow fiber structure with the walls composed of three dimensional interconnected nanotubes was obtained, and was named hollow fibrous nanotubes (HFNTs). The Crystallinity of TiO2 HFNTs at various temperatures was examined by X-ray diffraction (XRD), and their thermal stability was confirmed by SEM. VI The morphology and nanostructure were retained up to 800 oC for 2 h, which may be useful for high temperature applications. A continuous flow for photodegradation test of methylene blue (MB) in a nanoreactor system was conducted. The nanoreactor system consisted of three components: a nanoreactor, pipelines, and a circulation pump. A bundle of TiO2 hollow fibers were placed in a quartz tube, which acted as a cassette in the chamber of nanoreactor. The solution of MB flew through the nanoreactor continuously, circulated by a pump. The MB was decomposed by illuminating the nanoreactor with a UV light. Due to enhancement of the collision between the TiO2 surface and MB molecules and avoid the accumulation of byproduct, the efficiency of MB removal by the nanoreactor was much higher than that of bulk type reactors. Furthermore, in the continuous flow nanoreactor system, it was easy to recycle and reuse the photocatalysts without any separation step.