Violet Tungsten Oxide Cycle Reduction to Produce Micro Tungsten Powder

Fine and uniformity tungsten powder are key point for producing carbide, and micron and submicron tungsten carbide powder is useful to producing carbide. According to the relevant academic report found that single tungsten oxide can produce submicron or micron tungsten powder. Using violet tungsten oxide (VTO) producing fine tungsten oxide not only the process of it is simple as well as process parameters are easy to control and also equipment are not complex etc. Producing process as follows:

1. VTO were first reduction in hydrogen, along a first temperature of 640 ℃, the second temperature of 760 ℃, third temperature of 860 ℃, when the temperature reaches 860 ℃ heat preservation for 20min.
2. in the air at 500 ℃ making tungsten powder to oxidation with slowly heated for the first time, then heat preservation for 10min.
3. Replace the first step and second to continuous cycle reduction reaction.
4. Using alcohol on the analytical results above steps were dispersed pattern, then using BT-9600 laser particle size analyzer and JXA-840A electron probe scanner to analysis particle size and morphology of samples.

Tungsten Oxide Materials Application

Tungsten oxide has good physical and chemical properties, so it can be widely applied in many different fields. Its ultra-fine powder has a strong absorptive capacity of the electromagnetic wave, so it can apply in solar energy field which can be an absorbing material, and in the military field it is an important stealth material. And tungsten oxide has a special catalytic properties in the fuel cell can be used as the anode electrode catalytic materials, as well as can be low-temperature superconducting materials, but also often doped with TiO₂ as a photocatalyst and so on. Tungsten oxide film based on tungsten oxide powder material having a broader application, it can transform it presents color when giving appropriate optical radiation or using electric field. And this is photochromic or electrochromic. And at present these technologies are widely used in electrochromic windows, large information displays, and automotive mirrors and so on. Meanwhile tungsten oxide for NO_X, H₂S, NH and other gases are highly sensitive, so as a sensitive material of the sensor can be used for detection of food, medicines, and other exhaust. Tungsten oxide active apply in different fields, so the study of the tungsten oxide still continue to carry out, and it has also become one of the most potential for development of materials.

Purple Tungsten Oxide Production Manufacture Process

Purple tungsten oxide using the APT as raw materials,which is during at the closed furnace in the industry. Under certain conditions, adding NH3 during calcination, and the NH3 will decompose H2 and N2, it will form a wet hydrogen atmosphere furnace in the stove, so that APT under mild reducing atmosphere, gradually decompose, generating purple oxide reduction. There are many factors in the process of preparing purple tungsten, one by the hydrogen reduction of tungsten oxide mechanisms apparent hydrogen greater humidity, the temperature required to obtain the higher tungsten purple, so choose the calcination temperature should be 770 ~ 815 ℃, Second, in the calcination process feed speed, tube speed, NH3 traffic and others factors affect the production of tungsten purple in varying degrees. In the preparation of tungsten purple we should to coordinate various relationships in order to produce a single phase purple tungsten. Its chemical equations are: 3 [5 (NH4) 2O · 12WO3 · 5H2O] = 2w18O49 + 40H2O + 35H2 + 15N2. Comprehensive variety of experimental results can be obtained tungsten production purple optimum parameters are as follows:

Temperature/℃	Delivery Rate/(kg.min-1)	Furnace tube rotational speed（r.min-1）	NH3 Rate of Flow/(m3.h-1)
790~850℃	0.55	2.0	0.7

Particle Size and Bulk Specific Gravity of Blue Tungsten Oxide

By using SEM to observer the particle size and bulk specific gravity of blue tungsten oxide discover that baking temperature between 400 ~ 500 ℃ blue tungsten oxide particles more uniformly. When baking temperature at 400 ~ 500 ℃ can obtain fsss particle average of 11.9 ~ 12.0um, bulk specific gravity of blue tungsten oxide 2.49 ~ 2.50 g / cm². When baking temperature at 400 ℃, blue tungsten oxide average fsss particle size is 12.0um and bulk specific gravity is 2.50g / cm². when the baking temperature is 450 ℃, the fsss particle size is 11.9um, bulk specific gravity is 2.50 g / cm². 

The solution temperature baking at 500 ℃, Fei particle size of 12.0um, bulk specific gravity of 2.49 g / cm².
Analyzing the above data can be found, baking temperature between 400 ~ 500 ℃ the particle size distribution curve is quite the same and the particle are uniformity. Within each temperature range, the particle size distribution fluctuates within a region, each particle size distribution mainly between 10 ~ 40um and the bulk specific gravity fluctuation is not great. At the same time at different temperatures, the average diameter of blue tungsten oxide particle size also has a corresponding effect. The higher the temperature the blue tungsten particle size will be increased, but the impact is not obvious.

temperature（℃）	400	450	500
Fsss （um）	12.0	11.9	12.0
bulk specific gravity（g/cm2）	2.50	2.50	2.49