Synthetic process for gem grade diamond

Abstract

A synthetic process for gem grade diamond comprises the following steps: (1) placing an assembled synthetic block in a high pressure chamber of a cubic press; after pressurizing the synthetic block to a final pressure of 90-95 MPa at one time, maintaining the pressure; when the pressure rises to 40-50% of the final pressure, starting heating and enabling the heating power to rise to 4-5 kw within 10-15 s; after preserving the heat of the synthetic block for 3-5 min, increasing the heating power to 9-10 kw for heat preservation; (2) after preserving the heat of the synthetic block for 5-10 h, entering a continuous heat preserving and pressure maintaining stage after continuous temperature increasing, heat preserving, pressure increasing and pressure maintaining; (3) after continuous heat preservation, stopping heating and cooling the synthetic block to room temperature; releasing the pressure when the temperature is halved; finishing the process till the pressure is released to normal pressure. The synthetic process for the gem grade diamond is especially suitable for multi-crystal-seed synthetic processes, can reasonably supply enough carbon source according to the growing speeds of crystal seeds in the control process and can enable the crystal seeds to stably grow for a long time without being affected by spontaneous nucleation to synthesize large particle size and inclusion-free high-quality diamond single crystal; the crystal is colorless and transparent and the quality of the crystal is good; the synthetic process for the gem grade diamond can realize mass production and low production cost.

Description

technical field [0001] The invention belongs to the technical field of diamond synthesis, and in particular relates to a synthesis process of gem-grade diamond. Background technique [0002] Synthetic diamond is an extreme functional material with a wide range of uses. It has the highest hardness, the largest thermal conductivity, the smallest compressibility, the widest light transmission band, the fastest sound speed, and high carrier mobility. , are widely used in industry, science and technology, national defense, medical and other fields. In particular, the successful synthesis of gem-level large-grain single crystals has greatly broadened the application fields of diamond, such as high-precision machining for high-hardness materials, optical materials, and wide-bandgap semiconductor materials. [0003] At present, the synthesis technology of gem-grade diamond single crystal generally adopts the high temperature and high pressure temperature gradient method developed b...

AI Technical Summary

Problems solved by technology

[0006] In order to achieve commercial production of high-quality gem-grade diamonds, that is, mass production, the current synthesis process still has the following problems: 1. The initial pressure control is segmented control: that is, the pressure is first increased from room temperature to a lower pressure, along the The growth line of abrasive grade diamond slowly raises the pressure to the growth point of diamond while heating up, avoiding the growth area with more diamond nucleation, which cannot fully meet the needs of commercial gem-grade diamond, because gemstones are grown by high temperature, high pressure and temperature gradient methods. High-purity diamond uses high-purity graphite as the carbon source. Under high temperature and high pressure, the carbon source graphite is quickly transformed into small diamonds on the spot. The carbon of the diamond is dissolved into the solvent catalyst alloy, and the carbon of the molten metal finally reaches a temperature lower than that of the carbon source. Precipitate on the seed crystal surface to achieve the purpose of continuous growth. If the carbon supply in the early stage cannot meet the supply, commercial production cannot be realized; The expansion of the seed crystal will increase the ability of the carbon source to receive the carbon source, and the constant pressure cannot ensure sufficient carbon source to migrate to the seed crystal, and the carbon supply is insufficient, resulting in poor quality of the growing gem-grade diamond crystal; 3. In terms of temperature, the early stage The temperature is greatly increased: when the initial seed crystal is small, the area to receive the carbon source is limited, and the increase in temperature will cause the crystal seed to not completely absorb the diffused carbon source, resulting in spontaneous nucleation; 4. In the later stage of synthesis, the temperature Start pressure relief after a complete stop: the temperature in the synthesis chamber drops too fast, and the elastic recovery ability of the pressure transmission medium is weakened. At this time, the phenomenon of blasting is easy to occur when the pressure is relieved at high pressure, and the production cost increases.

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