How Prepare Pyrochlore Type Tungsten Oxide ?(二)

Current hydrothermal method has been widely used in the synthesis of inorganic materials and material handling, compared to other methods have many advantages: a relatively simple equipment required for the reaction, and water and heat control has significant operational and adjustable degeneration; hydrothermal method particularly suitable for the synthesis of a special structure, a new specialty compounds and concentrations of condensed matter, rules-oriented and crystalline perfection of preparing a crystalline material balance defects; under hydrothermal conditions, the solution viscosity decreased, diffusion and mass transfer process more smoothly, active reactant has greatly improved, and thus can replace some of the hydrothermal synthesis temperature solid phase reaction, and promoting, the development of low-temperature synthetic chemistry.

In 1989, Sweden's Amberg, who for the first time by hydrothermal prepared a pyrochlore type tungsten oxide cubic system, the phase is a hydrothermal method in the study of pH = 3.0 synthetic magnesium tungstate in occasional crystals obtained using, parsed too known to be W2O6 • H2O (ie H2W2O7). Kenneth et al., 1992 reported a more detailed preparation conditions of the hydrothermal synthesis of crystalline tungsten oxide and its relationships, found in a pH range of 3.5 to 4.5 is obtained pyrochlore-type structure, at a pH of between 1.3 to 2.0 The resulting structure is hexagonal. Whereas at pH between 2.0 to 3.5 to obtain a pyrochlore type and hexagonal mixed phase, if the pH is greater than 5 are not precipitate the product. Guo et al., 1995 by hydrothermal synthesis using HCl to adjust the pH value of 6.0 was also prepared a pyrochlore-type oxide, tungsten, and the material has good electrochemical characteristics, indicating that factors pyrochlore type hydrothermal synthesis of tungsten oxide Many, wherein the pH of the environment is likely to be the most important factor.

Research on China Hydrothermal Method tungsten oxide pyrochlore type rarely, the method is slightly different: Within a pH range of 2.5 to 4.5 is obtained pyrochlore type superfine powder of pure tungsten oxide phase at pH get between 0.5 and 2.0 is hexagonal tungsten oxide. Studies have shown that while in the temperature range of 130 ~ 200 ℃ of the prepared powder grain size difference is not more than 5nm, the temperature can increase the grain size is slightly reduced, but little effect on the concentration of hydrochloric acid used in grain size. Powder aggregates mainly in the form of, EP-MA morphology shown in Figure 2, show the particle size analysis, the powder particle size 2 ~ 100μm bimodal distribution between the average particle diameter is large, and the powder for one month After the reunion phenomenon is more pronounced.

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
Tungsten & Molybdenum Information Bank: http://i.chinatungsten.com
Tungsten News & Tungsten Prices, 3G Version: http://3g.chinatungsten.com
Molybdenum News & Molybdenum Price: http://news.molybdenum.com.cn

• < Prev
• Next >