Abstract
Diamonds synthesis by a hot filament CVD (Chemical Vapor Deposition) method in a closed system was carried out as a pre-study under micro gravity. A gas mixture of 1.5 vol % ethanol and H2 was used for the starting gas. Temperature measurement and gas analysis by gas chromatograph in the chamber during the synthesis were carried out. Temperature profile and flow velocity in the chamber under micro gravity (5 X 10- 3 g) and normal one (1 g) were simulated with a numerical code. In the chamber used in this study (100 mm in diameter and 100 mm in height) quality of the synthesized diamonds became lower after 15 minutes in reaction, because oxygen radicals/ atoms might be consumed at that time. It was suggested by the calculation that the amount of atomic hydrogen near the substrate (the distance was 1 to 5 mm from the filament) under micro gravity was smaller by 1/100 than that under the normal one.
