Preparing W18O49 with the Aid of Microwave Irradiation

Monoclinic W₁₈O₄₉ can be successfully prepared by the annealing of WO3 · H2O, which is synthesized by microwave irradiation, at the temperature of 600°C. This kind of preparation method can improve the production efficiency effectively. It is simple, time-saving and green.

Microwave is an electromagnetic wave with a frequency of 300 KHz-300 MHz. This kind of electromagnetic wave has a wavelength of 1 mm-1 m. It has properties of penetration, reflection, absorption and selective heating. As a spread medium and a kind of calefaction energy source, microwave irradiation is applied in the field of chemistry.

As for the application of microwave irradiation in the field of chemistry, it is a gradual process, which is as follows:

1. In 1967, Williams reported the experimental results of accelerating some chemical reactions with microwave, which extended the technology of microwave irradiation to the field of chemistry.

2. In 1986, R.N. Gedye et al. carried out chemical reactions such as esterification and hydrolysis in microwave oven. Therefore, microwave began to be used in synthetic chemistry.

3. Since then, microwave technology has been applied in various fields of chemistry gradually.

The former heating technology is a kind of external heating technology. The surface of the object has to be heated first, so as to complete the internal heating of the object through the heat energy. Different from that, microwave irradiation is a kind of internal heating technology. After the sample absorbs microwave, the instant deep heating function will be realized. High energy will be produced by the thermal movements between molecules.

Microwave irradiation is a heating technology that has the advantages of fast heating, energy saving and environmental protection. As a new technology, it is applied in the preparation of inorganic nano materials and ultrafine powder, improving the production efficiency effectively.

WO₃ · H2O was synthesized by microwave irradiation, and then monoclinic W₁₈O₄₉ is successfully prepared by annealing WO₃ · H2O at 600°C. This is a simple preparation method of W₁₈O₄₉ with high efficiency.

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