Artículos de revistas
Properties of mesoporous tungstosilicic acid/titania composites prepared by sol-gel method
Fecha
2010-03-15Registro en:
Blanco, Mirta Noemi; Pizzio, Luis Rene; Properties of mesoporous tungstosilicic acid/titania composites prepared by sol-gel method; Elsevier Science; Applied Surface Science; 256; 11; 15-3-2010; 3546-3553
0169-4332
Autor
Blanco, Mirta Noemi
Pizzio, Luis Rene
Resumen
The tungstosilicic acid/titania composites were prepared by the sol–gel method. Titanium isopropoxide was used as titania precursor, and urea as a low-cost template. The tungstosilicic acid (TSA) was added in the same step as that in which titania hydrogel is formed. The TSA-modified samples only showed the
characteristic peaks of anatase phase of titanium oxide in the XRD patterns, indicating that the presence of TSA retarded the crystallization of the anatase phase and its transformation into the rutile phase. Spherical particles with sizes between 200 and 700 nm, formed by aggregation of nanoparticle aggregates (4–50 nm in size), were observed. The particle size increased when the TSA content was
raised and also increased slightly with the thermal treatment temperature. Mesoporous materials were obtained, with a mean pore diameter higher than 3.1 nm. Both the increase of the TSA concentration in the solid and the calcination temperature led to a decrease in the specific surface area of the samples. The
main heteropolyoxometallate species present in the composites is the [SiW12O40]
4 anion for the composites calcined up to 500 8C. The band gap energy decreased as a result of the introduction of TSA into the titania matrix, though it remained almost constant with the calcination temperature increase.