Characterization and thermal stability of cobalt-modified 1-D nanostructured trititanates

• Published in: Journal of solid state chemistry 2009-01, Vol.182 (1), p.172-181
• Main Authors: Morgado, Edisson, Marinkovic, Bojan A., Jardim, Paula M., de Abreu, Marco A.S., Rizzo, Fernando C.
• Format: Article
• Language: English
• Subjects: 1-D nanomaterials; ABSORPTION; Anatase; CALCINATION; Cobalt; COBALT COMPOUNDS; COBALT IONS; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; CRYSTAL STRUCTURE; ELECTRON DIFFRACTION; Exact sciences and technology; Growth from solutions; HYDROTHERMAL SYNTHESIS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ION EXCHANGE; LAYERS; Materials science; Methods of crystal growth; physics of crystal growth; NANOTUBES; Physics; QUANTUM WIRES; RUTILE; SODIUM COMPOUNDS; Solid surfaces and solid-solid interfaces; SURFACE AREA; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Thermal expansion; thermomechanical effects and density; THERMAL GRAVIMETRIC ANALYSIS; Thermal properties of condensed matter; Thermal properties of crystalline solids; Thermal transformation; TiO 2; Titanate; TITANATES; TITANIUM OXIDES; X-RAY DIFFRACTION
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2008.10.008

One-dimensional (1-D) nanostructured sodium trititanates were obtained via alkali hydrothermal method and modified with cobalt via ion exchange at different Co concentrations. The resulting cobalt-modified trititanate nanostructures (Co-TTNS) were characterized by TGA, XRD, TEM/SAED, DRS-UV–Vis and N 2 adsorption techniques. Their general chemical formula was estimated as Na x Co y /2H 2− x − y Ti 3O 7 · nH 2O and they maintained the same nanostructured and multilayered nature of the sodium precursor, with the growth direction of nanowires and nanotubes along [010]. As a consequence of the Co 2+ incorporation replacing sodium between trititanate layers, two new diffraction lines became prominent and the interlayer distance was reduced with respect to that of the precursor sodium trititanate. Surface area was slightly increased with cobalt intake whereas pore size distribution was hardly affected. Besides, Co 2+ incorporation in trititanate crystal structure also resulted in enhanced visible light photon absorption as indicated by a strong band-gap narrowing. Morphological and structural thermal transformations of Co-TTNS started nearly 400 °C in air and the final products after calcination at 800 °C were found to be composed of TiO 2-rutile, CoTiO 3 and a bronze-like phase with general formula Na 2 x Ti 1− x Co x O 2. Co 2+ incorporation in 1D-trititanate crystal nanostructure (Co-TTNS) causes reduction in interlayer distance by comparison with its sodium precursor (Na-TTNS) and leads to enhanced visible light photon absorption efficiency due to a strong band-gap narrowing.