Издательство СО РАН

Издательство СО РАН

Адрес Издательства СО РАН: Россия, 630090, а/я 187
Новосибирск, Морской пр., 2




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Поиск по журналу

Химия в интересах устойчивого развития

2005 год, номер 2

Preparation of Nanocrystalline WO3 and MoO3 by Different Sol-Gel Methods

Y. Dimitriev1, R. Iordanova2, M. Mancheva2 and D. Klissurski2
1University of Chemical Technology and Metallurgy, Kl. Ohridski bl. 8, Sofia 1756 (Bulgaria)
2Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences,
G. Bonchev str., bl. 11, Sofia 1113 (Bulgaria), E-mail: reni-11@abv.bg
Страницы: 185-189


Two sol-gel methods for the preparation of WO3 and MoO3 nanopowders were used in this work: i) an ion-exchange reaction and ii) an oxidizing reaction (M+H2O2). The phase and structural transformations undergone by colloidal solutions of tungsten acid (i) and peroxotungsten and peroxomolybdic acids (ii) as a function of thermal treatment were investigated by X-ray diffraction (XRD) and infrared spectroscopy (IR). Depending on the methods used, different phases were obtained: crystalline hydrates, amorphous and nanocrystalline products. The tungsten trioxide hydrates were prepared by the ion exchange method, crystallization in m-WO3 occurring above 300oC. The tungsten sample being formed in the oxidizing reaction remained amorphous up to 300oC; above 300oC, m-WO3 crystallized. The particle size of m-WO3 was 15nm irrespective of the methods applied. IR analysis showed that amorphous tungsten network was built by distorted WO6 units without participation of peroxo groups (O22-). The preparation of MoO3 nanopowders by an oxidizing reaction was also studied. Crystallization of MoO3 was found to start earlier (200oC), leading to completely crystallized o-MoO3 at 300 oC. The amorphous state of the product was detected at 100oC only. Comparative analysis of the methods applied showed the oxidizing method to be more suitable for obtaining nanoparticles.