Method of making diamonds

摘要

Diamonds are produced by subjecting carbon to high temperatures and pressures in the presence of a metal of the elements in Group VIII of the Periodic Table or manganese, tantalum or chromium or alloys thereof wherein the metal or alloy is molten or in solid solution and wherein the temperature and pressure are selected to lie for each metal or alloy at a point in the diamond zone of the diamond/graphite equilibrium diagram closely adjacent the high temperature side of the equilibrium line and above the cube region, maintaining the temperature constant over a period of time sufficent to allow the diamonds to form, then reducing the temperature and pressure and recovering the diamonds. In Fig. 2 the line AB represents the diamond graphite equilibrium line for a nickel-chromium catalyst consisting of 80% Ni and 20% Cr. The cube region is the area between AO and CD. Operation is in the shaded area between EF and DB. With a small vessel the pressure is raised to P1, where it is kept while the temperature is raised to T1; after stabilization the temperature is quickly raised to T2, e.g. in 1-3 seconds where it is held for a few hours to allow diamonds to form. In a large vessel, after the pressure is raised to P2, the temperature is raised as quickly as possible to T3 and held there until the system reaches equilibrium. It is then cooled to T2 and held as before. If desired, the temperature may be raised first and then the pressure increased until a point in the shaded area is reached. Specifications 830,210, 874,291 and 971,157 are referred to.