DETERMINAÇÃO DE CENTROS DE COR EM FIBRAS DE TIO2 E DE TIO2 CONTENDO PERCURSORES DE TUNGSTÊNIO USANDO O SISTEMA CIELA*B*

Abstract

Optical properties concern a material's response to interaction with electromagnetic radiation, for example, visible and ultraviolet light, heat, X-rays, radio waves, gamma rays and infrared radiation. Each of these varieties is distinguished by the frequency of oscillation of the fields. Visible light is concentrated in a small region of the electromagnetic spectrum, more specifically in the range between 0.4 μm to 0.7 μm. Radiation near the lower limit has a violet appearance and radiation near the higher limit has a reddish appearance. When light interacts with a solid, a part of the radiation is transmitted through the medium, a part is absorbed and a part is reflected at the interface. Materials capable of transmitting light with little absorption and reflection are transparent. Materials capable of transmitting light, but in a diffuse manner, dispersed within the material, are translucent and opaque materials are impenetrable to the transmission of visible light. The absorption or emission of electromagnetic radiation can be linked to electron transitions, which occurs due to the existence of different states between energy levels. In this work, we examine the visual perception of different colors when mixing tungsten precursors (H₂WO₄ and Na₂WO₄.2H₂O) with TiO₂. The fibers of TiO₂, TiO₂/WO₃ and TiO₂/Na₂WO₄.2H₂O were obtained by electrospinning and, characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and colorimetric tests. The results indicate that the optical properties were influenced by the calcination temperature and intensified the absorption of light by the fibers.