2015年11月10日星期二

Blue Tungsten Oxide Producing Tungsten Oxide Process Requirement

When blue tungsten oxide has same quality, the reduction process plays an important role at tungsten powder particle size. In producing fine tungsten powder must be strictly controlled reduction of temperature, hydrogen flow rate, hydrogen gas humidity, the thickness of the material layer, through hydrogen speed and direction, as they will influence fine tungsten powder producing.

Firstly, hydrogen-way requirements, generally speaking, there are two ways through hydrogen: cis hydrogen and inverse hydrogen. When the hydrogen reduction reaction at low temperatures and low humidity conditions, following hydrogen flow direction to push the boat along will obtain fine tungsten powder which is better than using inverse hydrogen way produce tungsten powder.

For another requirement is the reduction temperature, the higher reducing temperature the faster response, the more intense vapor transport, resulting in crystalline powder. And tungsten powder will agglomerate and coarse. Therefore, during the reaction the temperature should use low starting point, warmed gently heating system. Because the reduction temperature is low, heating will not so fast, so the water for the reaction is not too much which is in favor of the producing fine tungsten powder.


Blue Tungsten Oxide Producing Tungsten Oxide Quality Requirement

The quality of blue tungsten oxide has some effect on producing fine tungsten powder, so in order to make more good quality and performance fine tungsten powder, choosing good quality blue tungsten oxide will be the important section.
Firstly, quality blue tungsten oxide are very strict at blue tungsten oxide impurity content, alkali metal, for example, impurities usually is oxygen carriers, and that will delay the oxygen residence time in the powder layer, enhanced chemical vapor migration process, thereby enhancing the tungsten powder particle size.

Secondary, the requirement of blue tungsten oxide particle size, different blue tungsten oxide  particle size at temperature of 800 ℃ through hydrogen the blue tungsten oxide particle size is no the same. The study found that coarse blue tungsten conducive to the production of fine tungsten powder, because coarse particles have good ventilation during reduction and it will help to rule out reducing water vapor.

Finally, the requirements of blue tungsten oxide volatiles, blue tungsten containing different amounts of residual volatiles NH4 and H2O, these volatiles will produce water which will make hydrogen more humidity when blue tungsten oxide reducing tungsten powder. And this is not good for producing fine tungsten powder.


2015年11月6日星期五

Blue Tungsten Oxide To Γ-Tungsten Oxide‘s Reduction Reaction Process

Learn blue tungsten oxide (blue tungsten) phase component is good for producing good performance tungsten powder preparation, according to investigate the phase composition, selecting the raw materials and control of the production process can be more clear which can be producing good performance tungsten powder. Blue tungsten oxide during the restore reaction the main phase component of it is mainly β- tungsten oxide (WO2.9), γ- tungsten oxide (WO2.72), tungsten dioxide (WO2) and tungsten powder.

First discussing the reduction process there are from blue tungsten oxide to γ- tungsten oxide. According to research data shows that the main phase components of β- tungsten oxide are rough and surface has cracks. As the development of reaction the oxygen atoms decrease and vacancy increase, the β-tungsten oxide restore to γ- tungsten oxide. And γ-tungsten oxide surface roughness is further increased, further increases cracks, particle morphology is needle-like and short rod, its irregular, but these structures favor the reduction reaction. γ- tungsten oxide particle morphology depends on reduction temperature, heating rate, material thickness and other factors.


Calcine Temperature Influence Blue Tungsten Oxide Particle Size

The study found that the calcine temperature for blue tungsten oxide fisher particle size has little effect. It is generally believed that during calcine process due to stress crystals and crystal phase change weight, resulting in cracks or broken into particles of irregular particles, but basically maintained the original APT particle dimensions. Blue tungsten fisher particle size only reflect the particle size dimensions, closely related to APT particle, blue tungsten fisher particle size therefore determined by the APT particle size.

In-phase component ATB and W20O58 which has different size,at 800 ℃ condition reducing found blue tungsten oxide fisher particle size has a significant impact on  the reduction of tungsten powder. In the case of blue tungsten surface area substantially the same situation, W20O58 phase component blue tungsten oxide fisher particle size from 7.9um to 12.94um, tungsten powder particle size is reduced from 1.7um to 0.99um. The ATB phase component blue tungsten fisher particle size from 6.22um increase to the 14.00um, the tungsten powder particle fisher particle size from 1.25um down to 1.12um.