2015年10月19日星期一

The Important of Blue Tungsten Oxide Hydrogen Reduction Process

Using blue tungsten oxide producing tungsten powder is generally taken the ammonium paratungstate or tungsten trioxide as raw material by weak hydrogen reduction. Blue tungsten oxide particle size is not a important factors in determining the tungsten powder particle size. The hydrogen reduction process of tungsten blue is the ultimate effect in determining tungsten powder particle size. Different reduction process parameters of blue tungsten oxide hydrogen reduction method will lead to different tungsten powder particle size and specific surface area. Because in the whole process of the blue tungsten to tungsten is chemical vapor migration, so the intermediate phase can form a relatively complete small faceted surface crystals.

Crystal formation and size depends on the speed of the water vapor formed and the speed of discharged from the difference material layer. So the water vapor concentration has a significant impact on the tungsten powder particle size. It is shown that when temperature lower than 600 ℃ and leading in small humidity hydrogen make reduction reaction, it will producing finer tungsten powder. Therefore, when using hydrogen reduction of blue tungsten oxide producing fine tungsten powder should be strictly controlled reduction process conditions.



The Current Situation of Doping Blue Tungsten Oxide Producing Tungsten Wire

Blue tungsten oxide is widely used in industrial processes mainly because of blue tungsten has many advantages such as high chemical activity, good doping effect, large surface area, reducing efficiency. China added K, Si, AI and other alkali metal oxides to produce tungsten wire is applied from the mid-1970s to the present.

But using blue tungsten oxide technology manufacture tungsten wire not only require a lot of money and equipment, and it also will bring great problems at repression which will cause tungsten blanks low yield, increased production costs. At the part of adding blue tungsten oxide pickling process will produce Hydrofluoric acid and it will lead to contamination the environment. So that subsequent processing pickling process more complex.

From the process is applied to the industries to now it has being developed and improved, for example, controlling the temperature when APT reduction the blue tungsten, tungsten powder ingredients doped est.. At present, the process has been able to meet the needs of electric light source industry basically. And not-acid washing of blue tungsten oxide process has also made a great progress, so that the improvement of the quality of tungsten blanks, decrease production costs.



2015年10月9日星期五

Blue Tungsten Oxide And Purple Tungsten Oxide


At present, the production of ultra-fine tungsten powder, use purple tungsten and tungsten blue two kinds of raw materials exist simultaneously, and therefore these two materials were compared, hydrogen reduction experiments under the same conditions, compare the restored tungsten powder particle size and uniformity of the difference to determine exactly what kind of material is more suitable for the production of ultra-fine tungsten powder. From the microscopic structure and the reduction mechanism of both raw materials analyzed two kinds of raw materials caused by the tungsten powder particle size reduction of hydrogen production and uniformity of the reasons for the differences.


Tungsten oxide reduction process, the particle size will usually change. Currently, the main theoretical explanation W powder particle size reduction process variations have two:
1) growth mechanism of chemical vapor migration. Tungsten and their oxides in contact with steam, will generate a volatile hydrated tungsten oxide (WO2 (OH) 2), evaporated to a homogeneous gas phase reduction reaction occurs with the H2, the reduction product of metal tungsten has been deposited on the nucleation of on the grain, so that the tungsten powder particles grow. This process is the reaction rate, the reduction product forms and materials will change significantly compared.
2) solid-phase local chemical reaction. Solid tungsten oxide contact occurs with H2 gas - solid reaction of oxygen atoms with the gradual removal of lattice rearrangement. This process is slow reaction rate and the reduction product form does not changed.


2015年10月8日星期四

Ammonium Paratungstate Preparing Blue Tungsten Oxide Affecting Factors

Ammonium paratungstate preparing blue tungsten oxide affecting factors are listed as below:
1.Temperature. As the temperature going up, grain size of blue tungsten oxide changes a little and irregularly. It turns out the effect of temperature is not obvious. Oxide content and ammonia content fall down.

2.Feeding speed. Feeding speed mainly controls the reduction time. The faster the feeding speed is, the shorter the reduction time. As the prolong of reduction time, oxide and ammonia content reduces. But the temperature has larger influence than reduction time. Ammonium paratungstate cracks into crystal water and ammonia under high temperature and turns into yellow tungsten oxide. Yellow tungsten oxide which is under hydrogen reduction and turns into blue tungsten oxide.

3.Speed of rotary furnace. As the speed of rotary furnace goes up, blue tungsten oxide grain size will be more even. It is because material gets more contact with furnace and the heating surface is bigger. It increase the uniformity and distribution of grain size of blue tungsten oxide.