GB1330922A - Method of manufacturing diamonds - Google Patents

Abstract

1330922 Diamond TELEDYNE Inc 24 June 1971 [13 Aug 1970] 29778/71 Heading C1A Diamonds are prepared by placing a mixture of non-diamond carbon and a carbon solvent in a cylindrical reaction chamber, inserting a piston into said reaction chamber, applying pressure to said chamber by applying force to the piston, and heating the reacting chamber until the conditions in the chamber are above the m.p. of the solvent and above the diamond-graphite equilibrium of the carbon phase diagram, the pressure and temperature being maintained for a time sufficient to convert at least a portion of the graphite into diamond, the piston being advanced further into the chamber as the graphitediamond conversion occurs, so as to reduce the volume of the reaction chamber and compensate for the density difference between diamond and graphite whilst simultaneously ensuring that the pressure in the chamber remains above said diamond graphite equilibrium line. The carbon charge may be placed in a vessel 80, which is placed in the cylindrical reaction chamber 44, into which chamber the cylindrical piston 46 is inserted. The pressure is applied via load plate 48 and pressure plate 42, and the container may be heated by insulating one from the other with insulating layer 86 and applying a potential between the piston pusher 52 and the load plate. Preferably, the pressure in the chamber is maintained substantially constant by the advance of the piston by appropriate amounts. A pressure may be applied to the chamber which is no greater than 0À1 kilobar above the diamond-graphite equilibrium line, and such pressure is then maintained for a period of time sufficient to form diamond.