Tungsten Oxide

The performance of tungsten oxide materials will directly affect the reduction behavior of tungsten powder and the final product performance. Therefore, on which material is most suitable for the production of ultrafine tungsten powder has been the subject of much attention in material science workers. Blue tungsten oxide and purple tungsten oxide is the main raw material for production of ultrafine tungsten powder, blue tungsten oxide originated in the last century 70's, mainly WO 2.90 , W 20 O 58  and ammonium tungsten bronze (ATB) mixture. Purple Tungsten oxide is a kind of tungsten oxide product developed in recent years in China. Its phase composition is WO 2.72  or W 18 O 49 . Blue tungsten is present through hydrogen reduction of raw materials prepared by tungsten powder is the most widely used, as long as the conditions of low temperature, dry hydrogen, high hydrogen flow, thin material layer, producing ultrafine tungsten powder method can restore t...

Blue tungsten oxide  is one of the important raw materials for making tungsten powder. As an important intermediate of tungsten in modern industry, it has been popular for many years.  The commom methods of preparing blue tungsten oxide are APT closed calcination method and hydrogen mild reduction method etc. Although they have been popularized for many years, they have more or less some environmental safety factors. As a result, people have never abandoned the quest for a more effective and environmentally friendly method for producing blue tungsten oxide. APT autoreduction method is an upgraded version of the APT hydrogen mild reduction method. What's different between them is that the APT autoreduction method does not add hydrogen or ammonia into the reacting furnace, instead, the heating temperature is increased to 600°C -800°C. APT decomposes hydrogen under high temperature....

Blue Tungsten Oxide is one of the important raw materials for making tungsten powder. Compared with yellow tungsten, blue tungsten oxide is considered to be an upgraded version of yellow tungsten oxide because of its good activity, large surface area, easy to dope and maintain original crystal shape. And it’s widely used. There are three main methods for making blue tungsten, APT closed calcination method, APT hydrogen light reduction method, intrinsic reduction method. APT closed calcination is one of the most widely used methods. APT closed calcination method is the most used to produce blue tungsten oxide production. The characteristics of APT closed calcination method is: use thermal decomposition of ammonia or a small amount of ammonia into the reducing agent, thermal decomposition temperature fluctuations in the range of 550 °C - 700 °C,  high yield, stable quality, which is composed of 70%W 20 O 58  blue tungsten oxide, 30WO 3 ...

Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. In China, there are three main methods for preparation of the blue tungsten oxide: APT closed calcination method, APT mild hydric reduction method and intrinsic reduction method. And the APT closed calcination method is the most used method. APT closed calcination method always keeps the furnace system with positive pressure in the heating process, preventing the air from entering the furnace. By this way, ammonia from APT pyrolysis splits into hydrogen and nitrogen. And in the weak reductive atmosphere, the blue tungsten oxide is produced. The entire process is confined in a rotary calciner. The usage and control of rotary calciner need cautious operation, as it is the main carrier of APT closed calcination process. Rotary hearth furnace is a rotary calciner with high automation, of which the ring-shaped bottom can be rotated. Generally it is divided into two sections to con...

Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. Compared with yellow tungsten oxide, blue tungsten oxide with its high activity, large surface area, easy doping, original crystalline shape is seen as an upgraded version of the Yellow tungsten oxide. Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. In China, there are three main methods for preparation of the blue tungsten oxide: APT closed calcination method, APT mild hydric reduction method and intrinsic reduction method. And the APT mild hydric reduction method is the most used method. The whole preparation process reacts in a multi-tube furnace of which the heating zone is divided into three parts. In the furnace tube, the heated APT•5H2O installed on the heat resistant boat is decomposed. Feeding a small amount of hydrogen into the furnace tube can keep the reducing atmosphere. Decomposed gas product and waste ...

The performance of tungsten oxide materials will directly affect the reduction behavior of tungsten powder and the final product performance. Therefore, on which material is most suitable for the production of ultrafine tungsten powder has been the subject of much attention in material science workers. Blue tungsten oxide and purple tungsten oxide is the main raw material for production of ultrafine tungsten powder, blue tungsten oxide originated in the last century 70's, mainly WO 2.90 , W 20 O 58  and ammonium tungsten bronze (ATB) mixture. Purple Tungsten oxide is a kind of tungsten oxide product developed in recent years in China. Its phase composition is WO 2.72  or W 18 O 49 . Blue tungsten oxide is present through hydrogen reduction of raw materials prepared by tungsten powder is the most widely used, as long as the conditions of low temperature, dry hydrogen, high hydrogen flow, thin material layer, producing ultrafine tungsten powder method can ...

In addition to the blue tungsten oxide form affects tungsten powder particle size, the process parameters also affect the size of tungsten powder. Influence of process parameters on the tungsten powder particle size is mainly hydrogen mode, heating systems and hydrogen influence humidity. There are two kinds of hydrogen modes, one is cis hydrogen mode and the other is inverse hydrogen. The study found that cis hydrogen mode reduction of tungsten powder particle size is significantly thinner than the inverse hydrogen mode. ATB phase blue tungsten powder at low temperature with cis hydrogen mode can producing tungsten powder particle size thinner, narrow distribution, and the nature the better.  In heating system, the researchers found that heating from a low temperature and the heating process more gentle process are good for the producing fine tungsten powder. At the same time hydrogen humidity also impact on the tungsten powder particle size, at the same other proces...

Learning blue tungsten oxide (BTO) phase morphology, size and uniformity, help to improve the performance blue tungsten oxide, so that it can be applied in more areas. To produce blue tungsten oxide is boat loading ammonium paratungstate (APT) to the hot zone and during the process to control the hydrogen flow, temperature and holding time these three parameters to produced blue tungsten oxide. By using hydrogen reduction method to produce blue tungsten oxide and the surface of it has a large number of cracks and voids star, breakage obviously, it has lost the characteristics of hexagonal grains, forming a loose rule like appearance. Blue tungsten oxide surface has cracks is due to a large amount of water molecules and ammonium molecules which is produced from APT decomposition during the reaction. So the crystal inside of APT will cause inner stress to make crystal lattice mutation, resulting in cracks. At the same time, the external hydrogen to penetrate APT inside promoted deep...

After analysis using blue tungsten oxide to produce tungsten powder by cyclic oxidation found the tungsten powder particle size is small, and good performance. From the experimental data show that after the first reduction tungsten powder‘s specific surface area is 0.119m2 / g which is 1.95times to blue tungsten oxide’s. From this we can see that tungsten powder particle size is smaller than the blue tungsten oxide and distribution is more concentrated, but there is a certain amount of coarse particles of tungsten powder.  In the second reduction which is using obtained tungsten powder in the air restore to tungsten trioxide then using hydrogen to make the second reduction. And the tungsten powder which obtained from the second reduction is finer. Comparing tungsten powder of the first reduction and the second reduction find in the second reduction there has more fine tungsten powder than first reduction, its particle size distribution is more uniform, but there are a small nu...

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. There...

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, th...

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 (WO 2.9 ), γ- tungsten oxide (WO 2.72) , tungsten dioxide (WO 2 ) 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...

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 ...

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...

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 volat...

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 inc...

After studies showed a major factors influence blue tungsten oxide (BTO) performance was particle size and production process. The process production conditions including baking temperature, hydrogen flow and baking time. On one hand, under the certain baking temperature, the particle will grow up and the crack will more rough when hydrogen flow decease.  But on the other hand when hydrogen flow increase, the particle will finer and uniform. This is mainly because of increased pressure and permeation of hydrogen will change the internal stress of particle, such stress can lead to lattice distortion, resulting in cracking particles. Therefore, the particles tend to rupture and produce a fine particle powder. Baking time also is an important factor for producing fine blue tungsten oxide. The long baking time, the bigger particle and surface crack of blue tungsten oxide. The experiments show, baking solution temperature at 400 ~ 500 ℃, baking time for 30 to 40 minutes, the hydrogen...

With the development of science and technology, there are more stringent on quality requirements of blue tungsten oxide. The particle size and morphology of blue tungsten oxide are an important factor affecting the performance of it. After studies show that the raw materials and producing process are important factors affecting blue tungsten oxide particle size. Firstly, the raw materials, if it has small particle size then using small raw material to produce blue tungsten oxide the particle of it will finer. Besides the blue tungsten oxide particle will more uniform.Secondly is producing process. The main factors which influence particle size is baking temperature, hydrogen flow and baking time and so on. Effect of baking temperature is at the beginning the crack will increase with the baking temperature increase, besides the rule crystal turn to irregularity small particle. But when the reaction reach to a certain degree the blue tungsten oxide particle crack will decrease with the...

Fine tungsten powder is an important raw material for producing tungsten carbide powder, to improve the performance of carbide tungsten is necessary to reduce or eliminate the coarse tungsten powder particles. Otherwise it will cause tungsten carbide cracks, fracture and other phenomena in the course. After studies the process of using blue tungsten oxide as raw material to produce fine tungsten powder research found that by using exceptionally pure ammonium paratungstate calcinate in ammonia to get blue tungsten and then go through the cyclic oxidation producing fine tungsten powder, and the tungsten powder properties is better which is less coarse. Producing process as follows: 1. Slow heating exceptionally pure ammonium paratungstate which is in ammonia to 600 ℃, when the temperature reach 600℃for 10min heat preservation to produce  blue tungsten oxide. 2. To obtain tungsten powder by restoring blue tungsten oxide in hydrogen. 3. The obtained tungsten powder slowly heating ...

Oxygen index have certain impact on the performance and morphology of blue tungsten oxide, researcher determination of oxygen index of blue tungsten oxide by weight method. After experimental data analysis found that the baking temperature has great impact on oxygen content and the color of blue tungsten oxide. When baking temperature at 350 ~ 500 ℃, the oxygen index between 2.96-2.90. Changing the baking temperature, the color and oxygen content of blue tungsten oxide also will change and surface gloss index has varying degrees of change. At 350 ℃, blue tungsten oxide ’s color is yellow-blue and has high oxygen index, matte. As the temperature increases, blue tungsten oxide gradually be reduced, when the baking temperature reaches at 450 ℃blue tungsten oxide’s color translated into blue-black and surface of it has metal light, oxygen index of 2.94. When baking temperature reached 500 ℃, oxygen index of 2.90, blue tungsten oxide color is blue-black. As the temperature continues to ri...