Growth Mechanism of Tungsten Oxide Nano Flower

When the temperature is gradually raised above 800 ° C, tungsten will not be evaporated because the melting point of tungsten is 3420 ° C. While the tungsten oxide has a boiling point of 800 ° C, the tungsten oxide will sublimate to vapor tungsten oxide. At the same time, it will follow the gas-solid reaction model model, tungsten oxide nano flower structure growth mechanism is as follows:

（1）In an aerobic environment, when the temperature is gradually increased, the tungsten metal particles are oxidized at high temperatures, and the surface is rapidly oxidized to a tungsten oxide layer.

（2）When the temperature is higher than 800 ° C, the tungsten oxide layer will sublimate and exist as a tungsten oxide gas particle layer over the substrate. Due to the sublimation of the tungsten oxide layer, the tungsten metal particles will once again be exposed to the oxygen atmosphere, again being oxidized and sublimated into tungsten oxide gas particles, so the volume of tungsten metal particles will gradually decrease. At the same time tungsten oxide gas particles will be cooled above the substrate and deposited again on the surface of and around the tungsten metal particles to form tungsten oxide nanorods that are preferentially grown along the plane. As the holding time increases, the tungsten oxide gas particle concentration above the substrate increases and the length of the nanorods increases.

（3）When the temperature drops below 800 ° C, the tungsten oxide layer will no longer sublimate and the volume of tungsten metal particles will no longer decrease. Tungsten oxide gas particles will continue to be deposited on the tungsten metal particles and the substrate, so that the length of the nanorods slightly increases to form a nano flower structure with tungsten as the core and tungsten oxide nanorods as the shell.

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