Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O.

Ammonium paratungstate is produced separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO₃, tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.

When concentrating an ammoniacal solution of tungstic acid (i.e. hydrous WO₃), the product obtained is ammonium paratungstate. Below 50 °C, the hexahydrate is formed, whereas when the temperature of the solution is above 50 °C, the pentahydrate or heptahydrate is formed. The former crystallizes as triclinic plates or prisms, whereas the latter as pseudorhombic needles.


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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.

Component of ammonium metatungstate is listed as below:

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Ammonium metatungstate is a source of high purity, water soluble tungsten which is essentially free of alkali and other metallic impurities. Ammonium metatungstate is very versatile and can be used as catalysts, capacitors, nuclear shielding, flame retardants, corrosion inhibitors raw materials, but also excellent raw materials in the preparation of ultra fine tungsten powder, tungsten heavy alloy powder, phosphotungstic acid, arsenic acid, silicon tungstate.

It is also used as a raw material for the production of tungsten catalysts for a variety of reactions including oxidation, hydroxylation, hydrogenation, and polymerization. Suitable carriers can be impregnated with alkali-free solutions of tungsten and processed to remove the water and ammonia. Such catalysts are used by the petrochemical industry.

Other applications include: 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).



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Ammonium paratungstate is a white, finely divided, crystalline material. It is produced by evaporation of purified ammonium tungstate solution to obtain pure paratungstate crystals. Controls of time, temperature, concentration and PH, determine the quality and physical characteristics of the ammonium paratungstate crystals.

Ammonium paratungstate is used as a source for high-purity tungsten oxides, tungsten metal powders, carbides, or as a laboratory reagent. Also tungsten powder including tungsten trioxide, tungsten blue oxide. Those powders are then used to make numerous products including wire, cutting tools, billets, welding electrodes, mining tools and many others. There are alloy series too, such as tungsten carbide alloy blade, alloy drill, alloy molds, etc.; and other wear, pressure, temperature and other machinery and equipment components. Also used in the manufacture ammonium metatungstate and other tungsten compounds as additives for the petrochemical industry. Other applications are in the fields of absorbent gels, coloring agent in the porcelain industry and the catalyst industry. 


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Ammonium paratungstate is a white crystalline salt of ammonium and tungsten, it is insoluble in water. Its shape is like sheet or needle. Ammonium paratungstate is used as a source for high-purity tungsten oxides, tungsten metal powders, carbides, or as a laboratory reagent. Also tungsten powder including tungsten trioxide, tungsten blue oxide. Also used in the manufacture ammonium metatungstate and other tungsten compounds as additives for the petrochemical industry.

Ammonium metatungstate is a tungsten chemical in the form of highly soluble hydrated crystals, solubility is 303.99/loogH:O when 20℃. It is white or slightly yellow crystals which has no harmful components and slightly acidic. Ammonium metatungstate is very versatile and can be used as catalysts, capacitors, nuclear shielding, flame retardants, corrosion inhibitors raw materials, but also excellent raw materials in the preparation of ultra fine tungsten powder, tungsten heavy alloy powder, phosphotungstic acid, arsenic acid, silicon tungstate. It can also 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).


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Tungsten element is more effective shielding and good machinable so that it is widely used in medical as collimator.Compare to lead ,tungsten is much more environmentally friendly and higher density which means smaller parts for the same weight.in neutron,X-ray and gamma ray optics,the collimator is a device that filters a stream of rays so that only those traveling parallel to a specified direction are allowed through.according to the use of lenses it is not yet possible to focus radiation with such short wavelengths into an image as is routine with electromagnetic radiation at optical or near optical wavelengths however tungsten collimator could be used in neutron ,X-ray and gamma-ray.

Tungsten shielding can be used the following medical areas:
Multileaf collimators
Radio guided surgery
Gamma probe
Medical isotope transport and containment
Radiotherapy machines
Computerized tomography scanners
Single-photon emission tomography
Positron emission tomography
Computerized tomography and X-Ray security machines
Oncology treatment systems
Oncology instruments
Radioactive syringe protection

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The energy dispersive X-ray detector consists of a multi-element detector and two collimator slits. The detector is a cryogenically cooled high-purity Ge-detector with 23 crystals arranged in a semi-annular array, which is comprised by tungsten shielding.
 
The 23 detector crystals are equally spaced in steps of 8.2°, covering azimuthal angles from 0° to 180°. The detectors are in orthogonal pairs, allowing simultaneous measurement of 11 sets of orthogonal q-vector components. Tungsten shielding is hiding in detector to control the direction of energy dispersive. This design is intended to improve the determination of strain tensor components and permits the measurement of crystallographic texture with a single detector set-up. The multi-element arrangement is also an advantage when the average grain size in the sample is comparable with the beam dimension. In this case, reflections can vanish for certain azimuthal angles. Element 23 at 180° is symmetrical to element 1 at 0° and is used for detector alignment.

The photograph is showing the tungsten shielding is hided in the 23 detector crystals.  

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After the removal of the deposition matrix or vacuum annealing treatment, the subsequent cooling process is not well controlled, it leads to the generation of transverse cracks on the deposition layer surface which along the vertical axial direction of tungsten tube.

Cause of tungsten tube surface transverse cracks as follows:

During cooling deposition, the deposition substrate shrink which would lead to the deposition of tungsten tube generate uneven deformation and subsequent release of residual stress.

When cooling deposition is completed, the deposition matrix contraction will cause the adjacent tungsten atoms deformed. As the further deformation of tungsten tube decreases, elastic deformation occurs.

After removing the deposit matrix, the gradual release of elastic deformation in tungsten tube inside will change the state of the surface stress, resulting in residual compressive stress decreases and even turn into the residual tensile stress. When the residual tensile stress exceeds the strength to withstand, depositing tungsten tube surface will produce transverse cracks.

 

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On the market today , for tungsten carbide end mill, the well accepted common coatings comprise Titanium Nitride (TiN), Titanium Carbon Nitride( TiCN) and Aluminum Titanium Nitride (AlTiN) , as well as Titanium Aluminum Nitride (TiAlN).

Since the coatings like AlTiN and TiSAlN have extra aluminum content,which are more effective at evacuating heat, they are more popular in end mill applications. Specially ,both TiAlN and AlTiN is a thin film coating that was delveloped from Titanium Nitride. It is recommended that when machining aluminum, brass, plastics and other nonferrous materials it is better to use AlTiN or TiAlN coated end mill with polished flutes to prevent edge buildup.


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Since the TiAlN is a thin film coating that was developed from Titanium Nitride with more aluminum content, TiAlN coated tungsten carbide end mills are more effective in heat removing and higher heat resistance.



During the milling processes, the temperature of the cutting edge could soar up to 1800°F , which would make tungsten carbide end mill suffer from damaging effects of heat. However, with the TiAlN coating, the aluminum in the coating provides a gaseous aluminum oxide layer for the cutting edge. In addition, the dry machining is recommended, as the heat is removed so well into the chips with TiAlN coating, and the high-speed or hard milling is also ideal match with TiAlN coated tungsten carbide end mill.

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