GB1334863A - Method of producing polycrystalline diamonds - Google Patents

Abstract

1334863 Synthetic diamond INSTITUT FIZIKI VYSOKIKH DAVLENY AKADEMII NAUK SSSR 27 Nov 1970 [4 Jan 1970] 56622/70 Heading C1A Polycrystalline synthetic diamond is produced by subjecting carbonaceous material to a pressure of at least 80 K.bar and a temperature of at least 1200‹ C. in the presence of a metal catalyst in a reaction chamber provided with heating means and with means for conducting heat from within the chamber to a heat sink outside the chamber whereby the heat of crystallization is conducted from the chamber. Preferably the catalyst in reaction chamber 1 is in the form of a rod 4 placed in the carboncontaining material, the cross-sectional area of said rod being not greater than 0À04 of the cross-sectional area of the reaction chamber in the plane transverse to the direction of maximum heat withdrawal. In a preferred arrangement the inside of the reaction chamber is in thermal contact with the apparatus for creating high pressure and temperature, particularly cooled sections 2, so that said apparatus acts as the heat sink. The heat of crystallization is preferably removed at a rate of at least 25 cals./min. In the preferred embodiment shown in Fig. 1, the rod 4 of metal catalyst acts as the means for conducting heat from the chamber being arranged to contact the carbonaceous material so that one end of the rod is in the centre of the reaction chamber and one end is in contact with cooled sections 2. In an alternative embodiment, Fig. 2, the carbonaceous material 3 is surrounded with an envelope of insulating material 5 having a heat conduction rate not lower than that of graphite, said envelope forming the walls of the reaction chamber 1. The envelope may be made of hexagonal boron nitride or boron carbonitride. The carbonaceous material used may be spectrally pure graphite.