Molybdenum foil for solar arrays of spacecraft (satellites, spacecraft and space stations)
Molybdenum and molybdenum alloy is a kind of high temperature resistant material, can maintain high strength at high temperature. Molybdenum and its alloys also have high thermal conductivity and low thermal expansion coefficient, good shock resistance. Molybdenum also has good electrical conductivity and wear resistance.
Therefore, molybdenum and molybdenum alloys are widely used in the field of aerospace, including molybdenum foil used in the interconnecting solar arrays of space vehicles (satellites, spacecraft and space stations). However, the weldability of molybdenum is relatively poor and it will oxidize strongly at high temperature. This oxide film has no protective effect. For the interlinked materials of solar panels of aerospace vehicles, good weldability and electrical conductivity are indispensable.
In order to solve the above problems, people need to modify the surface of molybdenum foil by electroplating. Silver is known to have good brazing properties, so the surface of molybdenum foil is electroplated with silver to improve weldability and reduce or prevent oxidation of molybdenum.
There are natural oxides on molybdenum surface, mainly MoO3, which can interfere with the adsorption of coating. In addition, the formation of alloy between molybdenum and silver (solid solution) is very difficult, the solution to the difficulty of molybdenum foil plating silver is generally to use pre-plating or impact plating method on the surface of the first layer of thin metal (such as chromium, nickel, gold, rhodium, platinum, etc.), after high temperature heat treatment and then continue plating, the process is more cumbersome, silver coating and molybdenum foil combination is not good. Therefore, it is necessary to study a new technique of silver plating on molybdenum foil surface.
Metal plasma injection modification technology is a surface treatment technology developed in 1980s. It is to directly inject metal ions into the material to be modified to obtain a metal modified layer with high bonding strength and no obvious interface, so as to improve the conductivity of its surface. Therefore, the metal plasma injection technology can solve the problems of silver electroplating on the surface of molybdenum strip, including the existence of natural oxides on the surface of molybdenum strip and the difficult formation of solid solution of silver molybdenum.
