Diamonds are not only considered valuable, but also virtually indestructible. They are one of the hardest natural materials in our universe. Consequently it is not surprising that producing diamond foils has become a key area in materials science research, particularly as these layers feature extreme hardness and wear resistance, exceptional chemical inertness and maximum thermal conductivity. Unfortunately, coating substrates directly with crystalline diamond is only possible on a limited range of materials.
Over several days, the diamond foils are produced in a test reactor in which a 40-micrometre thick diamond layer – approximately the thickness of a human hair – is grown on a silicon disc with a diameter of 30 centimetres. The diamond foils are produced in a low-pressure atmosphere of hydrogen and two percent methane under wires which are heated to 2000 degrees Celsius. After the coating process, a short pulse laser is used to introduce a circular fracture site with a diameter of 28.5 centimetres into the diamond surface. This makes it possible to separate the deposited layer as a very smooth diamond foil from the silicon substrate.
This procedure has opened up a whole new range of other possible applications. Virtually any substrate material can be coated with diamond film by means of a suitable joining technique. The extremely hard and smooth diamond foils can, for example, protect component surfaces against wear and tear. Research has already shown that diamond foils can give 100% protection for water turbines which are exposed to erosion from sand.
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