The history of cultivating diamonds in Chinese laboratories

As De Beers announced its entry into the cultivating diamond jewelry industry market in 2018, China's cultivating diamond source industry ushered in a new life. Through independent research and development, overcoming the technical barriers of catalyst formulations and equipment, innovating and synthesizing large particles of "jewelry diamonds" ( Also known as "jewel-grade diamonds"), it has realized the bulk supply of gem-grade cultivated diamonds with the largest grains, the best grade, and controllable color.

5.19ct near-colorless lla type laboratory cultivated diamond

Perseverance, innovation and breakthrough

China's first artificial fine-grained diamond was born in 1963. It was developed by the Institute of Geochemistry of the Chinese Academy of Sciences, the Indoor Research Institute of the Chinese Academy of Sciences, the Zhengzhou Sanma Research Institute, and the Academy of Geological Sciences. In the following forty years, although technology has continued to improve, there are many synthetic diamond magazines, showing yellow, brown, and opaque. The products are in the middle and low grade, and they are not up to gem level.

2005-The State Key Laboratory of Superhard Materials of Jilin University synthesized a 4mm type IIa diamond. Although the diamond particles are larger, the purity is not extremely high.

2014-Cultivated colorless synthetic diamonds with extremely high purity.

2019-Developed synthetic large particles of "jewelry diamonds".

The high-temperature, high-pressure, and large-size carat-grown diamond independently developed by China is equivalent to the DE grade of natural diamonds in color, and the clarity is equivalent to the VVS-SI grade of natural diamonds, realizing a gem with large grain size, excellent grade, and controllable color To cultivate diamonds at the highest level, and to meet the needs of consumers with the concept of "technology, environmental protection, fashion, and ever-changing", to truly make diamonds popular and shared.

Technological breakthroughs HPHT and CVD make synthetic diamonds

Synthetic diamond by HPHT and CVD method

(1) High temperature and high-pressure synthesis method (HPHT synthesis method)

HPHT synthetic diamond growth occurs in a small chamber inside the device, which can generate very high pressures. In the chamber, the raw material of diamond powder is dissolved in the molten metal flux and then crystallized on the seed crystal to form a synthetic diamond crystal. The crystallization process takes several weeks to one month or more to form one or several crystals.

This method usually synthesizes cubes, octahedrons, and the combination of the two. The color is usually yellow or yellowish-brown. There are often colored bands and metal inclusions inside. The unmelted metal inclusions are needle-like and flake-like. , Small columnar and irregular appearance, with a metallic luster, which makes synthetic diamonds magnetic. At the same time, it usually has no fluorescence under long-wave ultraviolet and often has yellow, green-yellow, and orange-yellow fluorescence under short-wavelength. Different growth areas show different colors of fluorescence.

Most of the synthetic diamonds produced by this method fail to reach the gem level and are generally used in fields such as drilling, cutting, aerospace, electronics industry, and heat exchange.

Colorless HPHT synthetic crystal

(2) Chemical vapor deposition method (CVD method).

CVD synthetic diamond growth is carried out in a vacuum chamber filled with carbon-containing gas (such as methane). The substrate can be a non-diamond material, but single crystal diamonds are usually formed by the precipitation of carbon atoms on the diamond substrate. An energy source (such as a microwave beam) breaks down the gas molecules, and the carbon atoms are adsorbed down into the flat diamond disk. The crystallization process takes several weeks to form multiple crystals at the same time. The CVD method can obtain diamonds with high purity without the participation of catalysts, reaching the gem level, so it is mostly used in the jewelry market. Usually, CVD synthetic diamond is carried out under low pressure and high-temperature conditions, the pressure is generally less than a large pressure, and the temperature is about 1000 degrees.

Most of the synthetic diamond single crystals are plate-shaped, and occasionally octahedrons and rhombic dodecahedrons can be seen at the edge. Early CVD synthetic colors are mostly dark brown or light brown. Recently, it has been found that after high-temperature heat treatment, the color is colorless or nearly colorless, and there are few internal inclusions. In some cases, needle-like and black irregular inclusions can be seen. , Because it does not appear metal inclusions, because it is not magnetic.

CVD synthetic diamond

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