Diamond prodn - from graphite, compensating for density difference in transformation by reducing reaction chamber vol

摘要

Reaction chamber vol. is reduced when graphite-diamond transformation sets in, compensating for difference in density between graphite and diamond, in process for diamond prodn. in which a mixt. of graphite and solvent for C, e.g., 60% Fe, 40% Ni alloy, are introduced into a cylindrical reaction chamber where press. is exerted by means of a piston, chamber is heated until temp. and press. conditions are above solvent m.pt. and above diamond-graphite equilibrium line of C phase diagram and maintained until at least part graphite is converted. Pref. press. is exerted until a predetermined press. is reached which is just above, pref. =0.1 kilobar over, diamond-graphite equilibrium line.