Nanometer blue tungsten oxide for ceramic microsphere may be produced stably by adjusting other process parameters without inletting H2 or NH3. Then, observe the effect of reduction time on blue tungsten oxide. And it is found that:
The effect of reduction time on blue tungsten oxide is as follows: With the extension of reduction time, the oxygen index (O/W) shows a downward trend, and residual ammonia also shows a downward trend. But the effect of test temperature is much greater than the influence of reduction time. This is because ammonium paratungstate is cracked at high temperature to generate crystal water and NH3, and then turns into yellow tungsten oxide. When yellow tungsten is reduced at a lower temperature (600-700°C) under a hydrogen atmosphere, it can rapidly turn into blue tungsten oxide in a short time (5min). In a short period of time (10~25min), it can be converted into violet tungsten oxide and brown tungsten oxide, respectively. In addition, the feed rate mainly controls the reduction time. And the faster the feed rate is, the shorter the reduction time is.
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