PREPARATION OF AL2O3 COATED PVA AND PVP NANOFIBERS AND AL2O3 NANOTUBES BY ELECTROSPINNING AND ATOMIC LAYER DEPOSITION

One dimensional nanomaterials, nanofibers have attracted great attention in the recent decades due to their excellent chemical, mechanical, electrical, optical and magnetic properties. In this work poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) polymer fibers were prepared by electrospinning from their aqueous solutions. Onto the polymer nanofibers Al2O3 layers were deposited by ALD. The film growth of 50 nm thick layers was done at 50 degrees C, trimethylaluminium (TMA) and water were used as precursors. Consecutively, the polymer core template of the oxide layers was removed to obtain metal oxide nanotubes. The removal took place in two ways: by heating or by dissolution. In order to be able to remove the polymer completely by the annealing process, the thermal properties of the as-prepared polymer nanofibers were analyzed by TG/DTA and the annealing temperature (550 degrees C) was determined. For the removal of the core from the composite fibers by dissolution, the nanocomposites were immersed in water at 60 degrees C. The polymer nanofibers, the core/shell nanocomposites and the nanotubes were all investigated by SEM-EDX, XRD and FT-IR methods. The SEM pictures revealed the obtained fibrous structure of the polymers after the electrospinning It also showed the similar and unchanged fibrous morphology of the nanocomposites after the ALD, and continued the as-prepared nanotube mats after the removal of the polymer templates. Based on the XRD results, the Al2O3 nanotubes obtained by both template dissolution and by annealing were amorphous. By analyzing the FT-IR spectra, it was concluded that the removal of the templates was successful and pure oxide nanotubes were obtained.