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 flow 1.51ml / min, will obtain more crack and uniform fine blue tungsten oxide particle.

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Ammonium metatungstate, also known as AMT, is a tungsten chemical in the form of highly soluble hydrated crystals, solubility is 303.99/loogH:O when 20℃, aqueous fairly stable. It is white or slightly yellow crystals which has no harmful components and slightly acidic. It is being used more frequently with the development of tungsten industry.

Its great solubility can be matched into 1.3-2.1 aqueous solution which can meet the demand of tungsten containing catalyst. Normally in order to reduce diffusion resistance, tungsten concentrate in solution should be lower. When producing doped tungsten powder, tungsten concentrate should be higher which can be achieved through adjust, so that it can reduce heat exhaustion. During the producing process, ammonium metatungstate can be pyrolysised to obtain highly active pyrolysate. Doped tungsten trioxide made from this process can be used to conduct hydrogen reduction. 


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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 temperature increase. While baking temperature at 400 ℃ blue tungsten oxide particles is uniformly but with the temperature rises, the uniformity of the particles is decline and the particles have grown.

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Ammonium metatungstate can be used as reagents for chemical analysis such as for chemical diagnosis; source material for the preparation of high purity tungsten trioxide used as a thin film substrate for certain semiconductor devices; high purity source material for research in tungsten chemistry; source material for DENOX catalysts industry; as a precursor to a variety of POM (polyoxometalates). Ammonium metatungstate applied in the manufacture of various petrochemical catalysts, It's the basic raw material of W-base catalyzer used in oil refinery.  

It has different classes listed as below:

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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 deepening and expanding of cracks. Because of this crack APT generating vacancies and in baking time it caused partial intense contractions to make further fragmentation then to produce a fine particle powder.

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It is known that tungsten carbide hardness and toughness is affected by the WC grain size. For the finer grain size could be adopted in tungsten carbide cutting tools for light to medium-heavy roughing cuts, whereas the much tougher carbides- the coarse grain size over 8 μm, instead of cutting, they are applied in forming dies. In terms of medium grain size leads to a balance between hardness and toughness and are likely to be used for heavier rough cutting. Specially, if the grain size varies from 0.5μm to 1μm, it falls into micrograin carbides, with which the tungsten carbide cutting tools could offer more wear resistance, sharper cutting edge and better surface finish for hardened steels machining.


With nowadays cutting-edge technology, a hard tungsten carbide adopts using “ultrafine” WCpowder with less than 1% Co binder could offer moderate fracture toughness.

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Tungsten anti-scatter collimators (also referred to as anti-scatter septa or grid), which is comprised by tungsten shielding, are used in CT X-ray equipment used for medical imaging, but also non-medical X-ray applications such as cargo scanners at (air)ports.

CT scanners consist of an x-ray source opposite an arc-shaped array of detectors. The collimator is located immediately in front of the detectors to protect them from scattered X-rays. Ideally, each detector in a CT scanner measures intensity of X-rays that reach the detector after traveling along a straight-line path from the X-ray source to the detector.

The commonly known tungsten anti-scatter collimator is comprised of thin plates formed from tungsten shieldling, which is suitable X-ray absorbing material. These tungsten plates are focused at the x-ray focal spot and generally located between columns of detectors (z-direction) but not between rows of detectors. This collimator is referred to as a "1D" anti-scatter collimator. In multi-slice scanners it has been found more advantageous to have shielding between both columns and rows of detectors; both directions are focusing to the X-ray source. This type is called a "2D" anti-scatter collimator.

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Tungsten heavy alloy is a composite metal alloy with up to 97% tungsten and 3% binding agents. Tungsten alloy often appears as a shield against x-ray and gamma-ray. It is also used for radiation shielding or as a collimator to focus radiation beams onto a target. In fact, these shields work so well that they have been used for many years by engineers that require radiation shielding or collimators. This is because tungsten alloy shielding has very high density,virtually 60% denser than lead. Hence, it provides superior attenuation characteristics for x-ray and gamma radiations.

There are many features of tungsten material is a preferred choice for radiation shielding. Here are some of the main features:
Tungsten has high effective in blocking harmful X-ray and gamma radiation.
Tungsten is nontoxic.
Tungsten is thinner and even lighter than lead shields.
Tungsten is not only easy to sterilize but is also easy to clean.
It is dimensionally stable up to 1000C.
Tungsten is hard, durable and easily machined with conventional tools.

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After the study found that factors which affecting the violet tungsten oxide particle sizes have material (APT) particle size and production process conditions. Production process conditions include reducing temperature, heating rate, water vapor and hydrogen pressure ratio, material thickness and reaction time.
Firstly, the influence factor is water vapor and hydrogen partial pressure ratio, which are water vapor and hydrogen partial pressure ratio increases and the size of products larger. This is mainly due to the formation of hydrogen gas to form a volatile humidity hydrous tungsten oxide, tungsten oxide which is easy to cover the finer particles, so that the particle size increases. Second, the impact factor is heating rate, after experiment found that to produce fine particles the heating speed should not too fast. When the reduction in a tube furnace, the heating rate depends on the furnace temperature gradient and push the boat speed, hence reducing the furnace temperature gradient and push the boat speed are conducive to obtain fine particles of violet tungsten oxide. Thirdly, the reduction temperature influence violet tungsten oxide particle size. When the temperature increase the particle is grouping up. At the same time the reducing time also impacts on violet tungsten particles, the greater the reduction reaction of the longer particle size. Finally, the thickness of the material layer, the material thickness is larger, the larger the particle size of the product.



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With the development of research, the ultra-fine particles as a new material have been widely used in modern industry and science. Violet tungsten oxide (VTO) has special properties and structure so get a lot of favor in the producing ultrafine tungsten powder. During producing tungsten powder not only process conditions is important but the raw marital particle size is also an important factors. Therefore, to study the factors which influence violet tungsten particle size is very important.

Producing violet tungsten oxide is through boatload an amount of ammonium paratungstate and pushes it into the reduction furnace hot zone. At the same time add a certain proportion of hydrogen and steam mixture to heat at a certain temperature, after a period heat preserving then cooling to obtain.

During the reaction, the factors that influence the violet tungsten oxide grain size are the raw material (APT) particle size and production process conditions. Production process conditions include reducing temperature, heating rate, water vapor and hydrogen pressure ratio, material thickness and reaction time. The study showed that, the relationship between violet tungsten oxide and raw material particle size is raw materials get smaller the particle size is smaller.



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