Preparation of Tungsten Copper Bias Filter by Chemical Vapor Deposition

Tungsten is widely regarded as the most promising fusion device due to its high melting point, excellent thermal conductivity, low sputtering yield and high self-sputtering threshold, low vapor pressure and low tritium retention facing the plasma material. However, the density of tungsten is very brittle and difficult to process. The preparation of tungsten on the heat sink material by coating technology can overcome these disadvantages.

Tungsten coating technology is the material preparation technology, but also the material connection technology, made by direct deposition of tungsten coating on the heat sink material to face the plasma components. The main coating preparation techniques are plasma spraying (PS), chemical vapor deposition (CVD), physical vapor deposition (PVD) and other means.

Some scholars have proposed a thick tungsten coating material prepared by chemical vapor deposition, reduction of tungsten hexafluoride by hydrogen gas, the base material deposited tungsten coating; purity of tungsten hexafluoride and hydrogen were greater than 99.9% and 99.99%; The ratio of tungsten hexafluoride to hydrogen is from 1: 2 to 1: 5. The deposition temperature range is from 500 ℃ to 700 ℃, the deposition rate is 0.4mm / h-1mm / h and the thickness of tungsten coating is equal to or greater than 1mm.

Tungsten copper gradient material and pure copper or CuCrZr alloy by thermal diffusion or brazing connection. Before deposition, the substrate material is polished, washed, dehydrated and dried.

As a tungsten coating facing the plasma material, chemical vapor deposition can reach a thickness of 1 mm to 5 mm. High deposition rate, up to 1mm / h; high chemical purity, can reach more than 99.99%; high density coating, more than 99%; coating in the columnar crystal perpendicular to the substrate direction, high thermal conductivity, room temperature greater than 170Wm / K; coating hardness. In addition it is possible to produce thick tungsten coated parts on complex shaped substrates.

Using pure tungsten coating - adapting layer - copper base material method, the adapting layer can solve the problem of mismatch of thermal expansion coefficient between tungsten and copper, and reduce the thermal stress of the coating and the substrate.

The research shows that the chemical vapor deposition method can be used for the first wall and the divertor module of the thermonuclear fusion device. The tungsten coating material has very high thermal shock resistance and thermal fatigue resistance. It can withstand more than 5MW / m² Steady high heat load.

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