The alkaline feed of crude sodium tungstate obtained from the caustic fusion of black tungsten ore was neutralized to a pH value near 9 to eliminate Si as routine, then the resulting feed was directly used as the external aqueous phase without eliminating P, As and Mo.

Through a single stage batch liquid membrane process at room temperature for 5 min under optimum operation conditions obtained by an orthogonal test, ammonium paratungstate directly crystallizes in the internal aqueous phase with 99.87% yield and the quality attained was the first grade of a national standard; meanwhile the pH value of the effluents was lowered to 6–7 in itself suitable for direct discharge and without W (VI) lost out of the raffinate. Finally, a continuous counter-current process of a single stage for a pilot plant was proposed.




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

Method using ammonia tungstate tungstic acid dissolved, add a boil deionized water. In the stirring, heating by ammonia, Ph value is 8, in the boiling solution by adding acetic acid, and then use the dilute nitric acid. The Ph value is adjusted to 2 ~ 4, continuing heating concentrated to a relative density of 1.5 ~ 2, stop heating, cooling and filtering. The filtrate is added with ethanol. Stir, settlement after filtration, crystal at 80 ℃ drying, pulverizing to obtain the product.

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.




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The crystallization of ammonium paratungstate tetrahydrate, ((NH₄)₁₀OH₂W₁₂O₄₂·4H₂O, APT·4H₂O) from aqueous ammonium tungstate solutions is a key unit operation in current tungsten powder production. Ammonium paratungstate hexahydrate (APT·6H₂O) can form under conditions where APT·4H₂O forms as well. Based on this information it was postulated that APT·6H₂O is metastable. Experiments were carried out to determine whether and under what conditions the hexahydrate is metastable.

It was found that the hexahydrate is metastable at a solution concentration of approximately 300-230 g/kg WO₃ and from approximately 90° to 96°C. APT·6H₂O is not formed when APT·4H₂O seeds are added prior to crystallization. It was found that the recrystallization of APT·6H₂O into APT·4H₂O is prompted by a decreasing water activity in solution during crystallization. The increase in solution temperature during isobaric crystallization also stimulates the recrystallization process. In industrial practice some residual crystals are always present in the crystallizer. Therefore, APT·6H₂O will not form during industrial crystallization.



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Tungsten copper heat sink is a composite of tungsten and copper. The coefficient of thermal expansion (CTE) of the composite can be designed by controlling the content of tungsten, matching that of the materials, such as Ceramics (Al2O3, BeO), Semiconductors (Si), Metals (Kovar), etc. The products are widely application in the fields such as radio frequency, microwave, high power diode packaging and optical communication system.

Tungsten copper heat sink is a heat base which is made of tungsten copper alloy. A heat base is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat bases are the heat exchangers used in refrigeration and air conditioning systems and the radiator (also a heat exchanger) in a car. Heat bases also help to cool electronic and optoelectronic devices, such as higher-power lasers and light emitting diodes (LEDs).

Advantages: High thermal conductivity, Excellent hermetic, Excellent size control, surface finish and flatness, Semi-finished or finished (Ni/Au plated) products available properties of WCu and MoCu heat materials.

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Copper tungsten rod (WCu) is the composite of tungsten and copper which own excellent performance of tungsten and copper. It is used widely in such industries as engine, electric power, electron, metallurgy, spaceflight and aviation.

Tungsten copper rod is a kind of round rod. Tungsten copper rod is a kind of composite material, which is manufactured by high-purity tungsten powder and high conductivity copper powder with the production process of isostatic pressing, sintering temperature and copper infiltrated

The manufacturing process is as follows: press the refractory metal, sinter the pressed compact at a high temperature, and infiltrate it with copper. All this is done under very closely controlled conditions. The result is a relatively hard material with superior arc and wear resistance, high physical Properties: at elevated temperatures, and good electrical and thermal conductivity.

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Copper tungsten alloy product is a sintered copper tungsten material manufactured by powder metallurgy. It forms dense composite offering hardness, wear resistance and a high softening temperature of tungsten combined with the good electrical conductivity of copper.

Copper tungsten alloy product is a pseudo-alloy of copper and tungsten. As copper and tungsten are not mutually soluble, the material is composed of distinct particles of one metal dispersed in a matrix of the other one. The microstructure is therefore rather a metal matrix composite instead of a true alloy.

The material combines the properties of both metals, resulting in a material that is heat-resistant, ablation-resistant, highly thermally and electrically conductive, and easy to machine.

Parts are made from the CuW alloy by pressing the tungsten particles into a desired shape, sintering the compacted part, then infiltrating with molten copper. Sheets, rods and bars of the alloy are available as well.

Commonly used copper tungsten alloy contains 10–50 wt.% of copper, the remaining portion being mostly tungsten. The typical properties of the alloy depend on its composition. The alloy with less wt.% of copper has higher density, higher hardness and higher resistivity. The typical density of CuW90 alloy, with 10% of copper, is 16.75 g/cm3 and 11.85 g/cm3 for CuW50 alloy. CuW90 has higher hardness and resistivity of 260 HB kgf/mm2 and 6.5 µΩ.cm than CuW50.

Copper tungsten may be used as an electrical contact material. In the most severe applications associated with power generation and transmission the switch may be totally immersed in oil. In these cases there is no advantage in using the tarnish resistant silver-based materials, as oxidation is prevented by the exclusion of air. Copper tungsten contacts are widely used in these cases, the selection of the grade used being dependent on the relative importance of conductivity and arc resistance.

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The causes of tungsten points’ ablation of car distributor as seen below:

7. Soft spring of tungsten points’ arm of distributor. If the tungsten points’ arm spring is much too soft, when the car operating at low speeds, the flashover condition remain normal; due to the high speed inertia effect of the engine, tungsten points’ closure is more slower when the car is operating at a high speed, and the off-fire phenomenon will occur, therefore, the car's exhaust pipe will issue a irregular sound like "sudden, sudden, sudden". Besides, tungsten points will appear rebound phenomenon after closing, and the appearance of spark will be more vulnerable, ultimately tungsten points will be ablated.

8. The ground capacitor is bad. Due to the weak spark, the flashover distance is shorter when test fire, therefore, when the engine is operating at no load, it will be more normal. But the car is instable in operation process, the carburetor will appear tempering phenomenon, and when the engine is working at high speeds, the exhaust pipe will sometimes shoot. So the arcs of tungsten points will increase, and ablate tungsten points eventually.

 

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The reasons of tungsten contacts ablation of car distributor as shown below:

7. The spring of tungsten contacts’ arm of distributor is too soft. If the tungsten contacts’ arm spring is too soft, flashover situation is still normal when the car running at low speeds; but when the car is working at a high speed, because of the high speed inertia effect of the engine, the closure of tungsten contacts is more slower, which appears off-fire phenomenon, so the car's exhaust pipe will issue a "sudden, sudden, sudden" irregular sound. Moreover, tungsten contacts after closure will appear rebound phenomenon, and the phenomenon make spark more vulnerable to emerge, and eventually tungsten contacts will be ablated.

8. Bad ground capacitor. When test fire, due to the spark is weak, and flashover distance is shorter, so the engine will be more normal when it is operating at no load. However, the car in working process is of instability, which would make carburetor appearing tempering phenomenon, and the exhaust pipe sometimes shooting when the engine is working at high speeds, make the arcs of tungsten contacts increase, eventually ablate tungsten contacts.


 

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Spherical crystal ammonium paratungstate is an important raw material for preparing high density and high property tungsten alloy, tungsten oxide calcinated by spherical crystal ammonium paratungstate after hydrogen reduction has high apparent density, flow ability and even green density. It can be used to produce high property tungsten heavy alloy which has high density, tenacity and ductility. For example, W-Ni-Fe high density alloy produced by the spherical crystal tungsten powder which the fisher particle size is less than 200mm will has high density and tenacity.

The preparation of spherical crystal ammonium paratungstate is still under investigation. At present, the main technology for producing spherical tungsten powder is plasma condensation method. The equipment required for this method is complicated and the producing cost is very expensive. Producing efficiency is unsatisfied, thus it can not be used for industrial production which is only under experiment. The study on ammonium paratungstate is mainly focused on its particle size, particle size distribution, loose density and flow ability.


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Tungsten powder is a powdered with polygon particle shape’s metal tungsten, its physical characteristics are as follows: chemical formula: W, molecular formula: 183.85, particle size: 2-0.5um, 4-6um, bulk ratio: 2.5-3.0g / cc. Tungsten powder CAS registry number is: 7440-33-7, which is raw materials of tungsten processed materials, tungsten alloys and tungsten products. Tungsten powder for oxygen and impurities content has certain requirements and commonly used tungsten powder particle size is 2-10um of average fsss size. In addition, in the tungsten powder’s specific surface, bulk density, tap density, etc. are also change at certain range. Tungsten powder classification is based on the purity and particle size. The figure is based on different size of tungsten powder, which is divided into 14 levels.

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