Research & Development

Diamond sintering requires the application of extreme heat and pressure. Typically, diamond is sintered at a temperature of around 1400°C (2550°F). At room pressure, these extreme temperatures would cause the diamond to revert to graphite. Maintaining extremely high pressure during the sintering process allows the diamond to remain in its natural form (see figure). This typically requires pressures of around 60 kbar (nearly 1,000,000 psi)—the equivalent of a 240 km (160 mile) high column of granite.

To achieve these extremely high temperatures and pressures simultaneously, US Synthetic uses proprietary cubic press technology. The cubic press consists of six large pistons, each of which is capable of supplying several thousand tons of force. Each piston pushes on a small tungsten carbide anvil, which in turn compresses a cubic pressure cell that contains the raw materials (carbide and diamond crystals). As soon as the cubic press reaches the desired pressure, electric current flows through a resistance heater embedded in the pressure cell to generate the required high temperatures. These conditions are maintained long enough to ensure complete diamond-to-diamond bonding of the individual crystals.