Compare fluoride (WF6) CVD (Chemical Vapor Deposition) to Chloride CVD findings, which shows that fluoride CVD tungsten tube has advantages as follows:

Low impurity content. Most metal fluoride having a boiling point over 1000 ℃. Therefore, at a constant temperature (about 20-28 ℃), in WF₆ evaporation stage, WF₆ is able to separate with most of other associated impurities.

Reduction reaction: WF₆ + H₂ → W + 6HF (125Kj/mol)

At a standard atmospheric pressure, the reaction can be achieved when the reaction temperature is above 300 ℃; at the temperature of 600 ℃, the equilibrium constant of the reaction is close to 1.

Because of the low reaction temperature for the reaction, it is possible to use ordinary heating equipment (such as stainless steel equipment, etc.), which makes the production of the heating equipment and actual operation easier. That is to say, the choice of fluoride CVD method for preparing tungsten tube is relatively plentiful.


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Because the tungsten tube prepared by CVD (chemical vapor deposition) owns many advantages, so it has attracted many metallurgical industry and other stakeholders’ attentions.

Advantages of CVD:

Compared to the powder metallurgy process, CVD process is more simplified and stable, and the tungsten tube can be achieved by one-time forming, thus the sintering, pressing, forging and other processes can be avoided.

With fast deposition speed and high efficiency. Because the refractory metal owns large atomic radius, high melting point and other characteristics, so it is not improper to adopt PVD (Physical Vapor Deposition) and other preparation technology ---with low deposition efficiency.

Good rolling and sputtering plating. Thus the deposited product can be obtained with complex shape, compact microstructure or large size. It is also easy to implement the film layer deposition on the pipe inwall or container inwall. It can even achieve the multilayer film deposition and multi-component alloy layer deposition.

The deposited film is of high purity, good density and multi-component alloy layer ingredient can be precisely controlled.


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Reactant gas: WF₆

Reducing gas: H₂

Deposition matrix: copper tube;

Atmospheric conditions: at atmospheric pressure;

CVD (Chemical Vapor Deposition) tungsten tube productive process:

First, at a constant temperature, heating WF₆ and wait for gasification, then pass WF₆ into the mixing gas chamber until it mixes with hydrogen fully, and then pass them into the reaction chamber.

Heating the copper tube until the temperature is up to the desired deposition temperature.

WF₆ and H₂ set off a chemical reaction on the surface of copper tube; WF₆ is reduced to W atom. And the W atom will gather nucleation and grow at the copper surface, eventually forming tungsten deposits---tungsten tube.

Chemical reaction formula of WF₆ and H₂ reaction is as follows:

WF₆+ H₂→ W + 6HF (125Kj / mol)

Using gas absorption device to absorb the residual gas of WF₆ and H₂, and HF discharged from reaction chamber.


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Great advances have been made in the production of X-rays, chiefly by the employment of very heavy currents. The exposures necessary for producing radiographs of the thorax have been reduced from minutes to fractions of a second.

To make this possible, much attention has been devoted to the target or anti-kathode, which is the critical part of the tube, for here it is that the focus of the kathode stream strikes, and the energy of the bombarding electrons is transformed into X-radiation.

A special target of tungsten has been introduced, that is being largely used by manufacturers of X-ray tubes. The tungsten is in the form of a thick button brazed into a solid block of copper, in some cases weighing as much as half a pound; this forms a lasting and efficient target, even when heavy currents are used for considerable periods of time, as is often necessary when using X-rays for therapeutic purposes.

The adaptation of tungsten for this purpose is an example of the great value that lies hidden in the rare and little-known elements, and doubtless other instances of a similar nature will develop as the metals become available.

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