Abstract
Nanocrystalline fibrous TiO2 (anatase) was prepared by electrostatic spinning from ethanolic solution of Ti(IV) butoxide, acetylacetone, and poly(vinylpyrrolidone) employing the Nanospider industrial process. These titania fibers were smoothly converted into cubic titanium oxynitride, TiOxNy fibers (a = 4.1930 angstrom) during 4 h at 600 degrees C in ammonia atmosphere.
The obtained material is convertible back into TiO2 fibers by heat treatment in air at 500 degrees C. The TiO2 fibers, which were reformed in this way, contain anatase as the main phase.
Their follow-up reaction with NH3 at 600 degrees C/2 h leads to a less crystalline oxynitride material with a approximate to 4.173 A, which is close to that of cubic TiO. Three subsequent cycles of this transformation were demonstrated.
The described conversions are specific for electrospun anatase fibers only. At the same experimental conditions, other forms of nanocrystalline anatase do not react with ammonia yielding cubic phases.