Abstract: A cubic boron nitride cluster comprises a core (10) and an overgrown region, the overgrown region containing a plurality of cubic boron nitride crystallites (12) extending outwards from the core (10). The majority of the cubic boron nitride crystallites (12) have a cross-sectional area which increases as the distance from the core (10) increases. A method of producing cubic boron nitride clusters is also provided.

Abstract: The invention provides a mass of crystals, particularly diamond crystals, having a size of less than 100 microns and in which mass the majority of the crystals are faceted single crystals. The invention further provides a method of producing such a mass of crystals which utilizes crystal growth under elevated temperature and pressure conditions, the supersaturation driving force necessary for crystal growth being dependent, at least in part, on the difference in surface free energy between low Miller index surfaces and high Miller index surfaces of the crystals. Preferably, the method is carried out under conditions where the Wulff effect dominates.

Abstract: The invention provides a mass of crystals, particularly diamond crystals, having a size of less that 100 microns and in which mass the majority of the crystals are faceted single crystals. The invention further provides a method of producing such a mass of crystals which utilises crystal growth under elevated temperature and pressure conditions, the supersaturation driving force necessary for crystal growth being dependent, at least in part, on the difference in surface free energy between low Miller index surfaces and high Miller index surfaces of the crystal. Preferably, the method is carried out under conditions where the Wulff effect dominates.

Abstract: A diamond cluster includes a core and an overgrown region containing a plurality of diamond crystallites extending outwards from the core, the majority of the crystallites having a cross-sectional area which increases as the distance of the crystallite from the core increases. Generally, at least 80% of the crystallites have a cross-sectional area which increases as the distance of the crystallite from the core increases. Furthermore, a method of producing a plurality of the diamond clusters includes the stops of providing a source of carbon, providing a plurality of growth center particles, each comprising a bonded mass of constituent particles, producing a reaction mass by bringing the carbon source and growth center particles into contact with a solvent/catalyst, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth, and recovering a plurality of diamond clusters from the reaction mass.

Abstract: A method of making a bonded, coherent material comprising a mass of crystals, preferably diamond crystals, in a matrix is provided. The steps include providing a source of the crystals of the type to be grown and which are substantially free of macroscopically faceted surfaces, producing a reaction mass by bringing the source crystals into contact with a suitable solvent/catalyst, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth in the reaction zone of a high temperature/high pressure apparatus to produce the material and removing the material from the reaction zone, the conditions of crystal growth being chosen such that the source crystals are converted to crystals having developed macroscopic facets of low Miller index. Preferably the conditions of elevated temperature and pressure used are such that the Wulff effect dominates.

Abstract: Diamond crystals may be grown by providing a source of diamond crystals, providing a plurality of growth centers defined by diamond crystals, mixing the source and growth center diamond crystals with a solvent/catalyst in particulate form to form a reaction mass, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth, and recovering the diamond crystals. The necessary supersaturation of carbon is achieved in the solvent/catalyst, at least in part, and preferably predominantly, by a selection of the particle size difference between the source crystal and the growth centers. The mass of diamond crystals produced by this method has a high concentration of twinned diamonds.

Abstract: A method of making a bonded, coherent material comprising a mass of diamond crystals in a matrix, which optionally contains another phase. The method includes the steps of providing a source of diamond crystals, providing a plurality of diamond centers defined by diamond crystals, producing a reaction mass by bringing the source and growth centers into contact with a solvent/catalyst, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth in the reaction zone of a high temperature/high pressure apparatus to produce the material, and removing the material from the reaction zone. The method is characterized by providing the necessary supersaturation of carbon in the solvent/catalyst, at least in part and preferably predominantly, by a selection of particle size difference between the source crystal and the growth centers. The mass of diamond crystals in the matrix of the bonded, coherent material of the invention has a high concentration of twinned diamonds.

Abstract: A method of producing diamond crystal growth on a seed crystal is provided. The method includes the steps of providing a seed crystal containing at least one twin plane and re-entrant growth surfaces associated therewith and applying high temperature/high pressure synthesis conditions to the seed crystal to cause diamond growth to occur preferentially on the re-entrant surfaces. The diamond growth on the seed crystal results in a diamond crystal being produced which has an aspect ratio greater than 1.

Abstract: A method of producing an abrasive compact, particularly a diamond abrasive compact, is provided. The method uses conventional compact manufacture conditions and is characterized by the mass of abrasive particles which is used. This mass has an average particle size of less than 20 and consists of particles having at least three different average particle sizes.

Abstract: The invention provides a method of making an abrasive compact using conventional compact synthesis conditions. The method is characterized by the use of an ultra-hard abrasive particle mass comprising at least 25 percent by mass of ultra-hard abrasive particles having an average particle size in the range 10 to 100 microns, and consisting of particles having at least three different average particle sizes, and at least 4 percent by mass of ultra-hard abrasive particles having an average particle size of less than 10 microns. The abrasive compact is preferably a diamond compact.

Abstract: A saw comprises a support such as a metallic disc-shaped blank and a working portion bonded to the periphery of the blank. The working portion comprises a mass of abrasive particles held in a polymeric matrix and has a bonding surface through which it is bonded to the support and a working surface. Examples of suitable polymeric matrices are rubber, polyurethane and nylon.

Abstract: A wire saw comprises a wire rope to which a plurality of cutting elements are secured in spaced relationship along its length. The cutting elements comprise a cylindrical metal sleeve, the central portion of which is swaged so that the inner surface grips the rope securely. Brazed to each end of the sleeve is a ring of a thermally stable diamond compact. The edges of the rings provide cutting edges for the element.

Abstract: A rotatable crown for a rotary drill comprising a working end and an opposite end for engagement in a drill rod, stringer or adaptor coupling, the working end having a cutting face and a plurality of discrete, spaced, elongate cutting elements located in the cutting face, each cutting element:(1) being of square or rectangular cross-section;(2) presenting a cutting point which is defined by a corner of the element;(3) having a longitudinal axis which extends behind the cutting face; and(4) being made of thermally stable abrasive compact.The crown has particular application for the drilling of substrates having a compressive strength of at least 180 MPa such as Paarl granite, Norite Gabbro and Reef Quartzite.