Macro Grain Ammonium Paratungstate formation conditions(Ⅱ)
- Category: Tungsten Information
- Published on Tuesday, 14 July 2015 14:37
2. Adding seed crystal and （NH4）2WO4 solution.
During the first nucleary, adding seed crystal will obtain ammonium paratungstate which has largest Fsss grain size and apparent density. Adding complete seed crystal will obtain ideal even ammonium paratungstate. After the nucleary of ammonium paratungstate, adding （NH4）2WO4 solution increase Fsss grain size and apparent density of ammonium paratungstate without changing distrubition of grain size. If the adding speed increases, micro ammonium paratungstate will be formed.
3.Mixture.
Increase the mixture speed, crystal formation rate is controlled by surface reaction instead of distribution. Ammonium paratungstate grain size varies in different mixture speed.
|
Speed |
Grain Size um |
|||||
|
rad/s |
<45 |
45-80 |
80-98 |
98-125 |
125-180 |
>180 |
|
0π |
53.5 |
21.0 |
9.0 |
8.8 |
7.5 |
0.2 |
|
2π |
12.4 |
33.1 |
32.2 |
18.3 |
4.0 |
0 |
|
3π |
36.8 |
50.5 |
7.3 |
4.4 |
1.0 |
0 |
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