A Preparation Method of Plasma-Facing Tungsten Coating in Fusion Reactor

Nowadays, the International Thermonuclear Experimental Reactor (ITER) has been built in France. The plasma-facing material is an urgent problem to be solved for ITER and future commercial fusion reactors. It is directly related to whether commercial power generation in fusion reactors can be realized in the future.

A large number of studies have proved that the previously recognized and optional plasma-oriented materials are tungsten, molybdenum, the alloys of the both, and C/C composite materials. Today, tungsten materials are considered to be plasma-oriented. The best candidate material for the material, the good compatibility of tungsten and plasma has been confirmed, while tungsten has high melting point, no co-deposition with bismuth and low corrosion rate, so the plasma-facing material in the future fusion reactor would be tungsten materials.

For high-power, steady-state fusion reactors, real-time removal of high heat loads is a necessary condition for safe operation of the first wall, which not only imposes stringent requirements on plasma-oriented materials but also on heat sink materials. In future fusion reactors, the heat sink material is generally selected from copper alloy or low activation steel. Tungsten has a large difference in thermal expansion coefficient from copper alloys and low-activated steels, which poses considerable difficulties in preparing tungsten coatings on copper alloys or low-activated steels.

In order to solve the above technical problems, the researchers proposed a method for preparing a plasma-facing tungsten coating in a fusion reactor using carbonyl tungsten as a precursor, using tungsten carbonyl as a precursor on the surface of the copper alloy, using plasma enhanced metal organic vapor deposition. The method comprises preparing a tungsten coating, wherein the copper alloy is a matrix or a heat sink material.

The CuCrZr alloy was processed into a sample size of 50 mm x 50 mm x 5 mm. Before deposition, it was polished by grinding paper No. 150, No. 600, No. 800, No. 1000, No. 1500, and then polished. Then, the deposited surface was degreased with acetone, ultrasonically washed with anhydrous ethanol, and dehydrated and dried. The sample was placed on the heating seat of the reactor, the substrate temperature was controlled at 200 ° C, the reactor pressure was constant at 100 Pa, the carbonyl tungsten gas flow rate was 1.5 mL / s and the temperature was controlled at 80 ° C. After 5 h of deposition, the constant temperature was maintained for 3 h.

This preparation method of plasma-facing tungsten coating has the following characteristics:

(1) The forming area is large, and when depositing in the reactor, the tungsten carbonyl is present in the form of a gas, and as long as the volume of the reactor is large, a large-area tungsten coating can be prepared under the condition that the process is satisfied; (2) Low deposition temperature: tungsten carbonyl has the characteristics of easy decomposition and volatilization at low temperature (melting point is 150 ° C); (3) the prepared plasma-facing tungsten coating has uniform thickness and high density, and carbonyl tungsten decomposes and volatilizes at low temperature. It is pyrolysis at the atomic level; (4) the purity of the coating is high, the carbonyl tungsten has a purifying effect in the volatilization and pyrolysis process; (5) the deposition rate is fast, the plasma is used in the deposition process, and the plasma is passed through the plasma, and promotes the pyrolysis of tungsten carbonyl, thereby greatly increasing the activity of tungsten carbonyl, resulting in an increase in deposition rate. Due to the above characteristics, plasma enhanced metal organic chemical vapor deposition can effectively prepare a tungsten coating that meets the requirements, so this method can be widely used to prepare plasma-oriented materials in a fusion reactor.

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