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The advantages of CVD diamond growth include the ability to grow diamond over large areas and on various substrates, and the fine control over the chemical impurities and thus properties of the diamond produced. Unlike HPHT, CVD process does not require high pressures, as the growth typically occurs at pressures under 27 kPa (3.9 psi). [51] [60]
InCent-LGD has three core research groups dedicated to different aspects of lab-grown diamond technology: [5] High Pressure High Temperature (HPHT) Group: This group focuses on the HPHT method of diamond growth, which simulates the natural diamond formation process by subjecting carbon to high pressure and high temperature.
The growth rate for 5 carats (1.0 g) type Ib (yellow, nitrogen-rich) crystals using Fe–Ni catalyst reaches as high as ~20 mg/h towards the end of 100 h growth cycle, i.e. crystals of 5 carats (1.0 g) to 6 carats (1.2 g) can be grown in less than 100 h.
In the HPHT diamond-growing method that was used by Gemesis, carbon, in graphite form, was placed in a cylindrical "core". A tiny CVD seed diamond was placed at the bottom of the cylinder. The graphite was then subjected to extreme pressure, 850,000 lbf/in² (5.9 GPa) and temperature, 3,000 °F (1,650 °C) for four days.
Apollo Diamond (defunct, assets sold in 2011 to Scio Diamond) [1] ALTR Created Diamonds [2] De Beers (Lightbox) [3] Diamond Foundry [4] Gemesis (now a non-producing reseller called Pure Grown Diamonds) [5] Scio Diamond Technology Corporation [6] (colorless) Tairus [7] WD Lab Grown Diamonds [8]
CVD diamond growth typically occurs under low pressure (1–27 kPa; 0.145–3.926 psi; 7.5–203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically include hydrogen as well, though the amounts ...
The hardness of synthetic diamond (70–150 GPa) is very dependent on the relative purity of the crystal itself. The more perfect the crystal structure, the harder the diamond becomes. It has been reported that HPHT single crystals and nanocrystalline diamond aggregates (aggregated diamond nanorods) can be harder than natural diamond. [25]
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