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With the development of technological innovation, the basic methods of human synthetic diamond are mainly divided into three categories: dynamic high pressure method, static high pressure method, chemical vapor deposition method. In 2000, China developed a unique six-face high-pressure device and its synthetic diamond technology, reaching the world's advanced level. In 2012, CVD synthetic diamonds appeared in the Chinese jewelry market. In 2013, NGTC Laboratories detected â€œpost-treatedâ€ HPHT synthetic diamonds (Type Ia). Lu Taijin said: "The actual application is more static high pressure method and chemical vapor deposition method to make synthetic diamond. Static high pressure method is a method of converting graphite into diamond in static high temperature and high pressure environment. This method is subdivided into two Species: direct conversion method and high temperature and high pressure (HPHT) solvent method. The former has higher pressure and temperature requirements due to the absence of catalyst, while chemical vapor deposition (CVD) is a method for laboratory synthesis of diamonds. The temperature of the synthesis conditions reaches 700-1000 Â° C. When the pressure is less than one atmosphere, the carbon-containing methane and hydrogen are chemically grown on the diamond seed crystal. The CVD diamond grows in a layered direction along the seed crystal, so most of them It is a nitrogen-free type IIa diamond."
When talking about the distinguishing features of colorless HPHT synthetic diamonds, CVD synthetic diamonds and natural diamonds, Lu Taijin explained: "The fluorescence characteristics can clearly distinguish their differences. The HPHT synthetic colorless diamonds are grayish blue and the block partitions are obvious; CVD synthetic diamonds are orange, green, blue, blue-green, and orange, with parallel layered growth lines; natural diamonds are mostly blue, blue-green, etc., mostly quadrilateral ring bands, meshes, bands, etc. In terms of phosphorescence characteristics, the three are also different. In addition, when using standard gemstones to illuminate with UV lamps, HPHT synthetic colorless diamonds are usually shorter than long waves and appear yellow or yellow-green fluorescence; CVD synthetic colorless diamonds are usually shorter than long waves. , showing yellow, orange or yellow-green fluorescence; natural colorless diamonds are usually longer than short waves." For how to identify these three, Lu Taijin believes that from UV-visible absorption spectroscopy, photoluminescence spectroscopy, trace elements, abnormal birefringence, magnetic properties , conductivity, key identification features and other aspects can be known.
â€œIn the case of NGTC, the laboratory can use the existing inspection and identification instruments on the market, and develop new methods and instruments to conduct diamond identification for the detailed study of the suspected samples.â€ Lu Taijin also recommended suitable for China for the participants. The market's new rapid inspection and identification instrument, including the Jewelry Multi-Band Illumination Observer (GV5000), is used for the investigation and preliminary identification of synthetic diamonds (bare stone, inlay), as well as the UV-Vis-NIR full spectrum diamond screening instrument (DS). -5000), diamond characteristic spectrum detector (PL5000) and so on.
Finally, Lu Taijin pointed out that large-scale gem-quality synthetic diamond products will appear â€œunstoppableâ€ in the jewelry market. In recent years, domestic and foreign jewelry testing institutions have provided strong technical support for the healthy development of the industry. NGTC, HRD and other institutions have carried out a series of studies on the investigation and identification of natural and synthetic diamonds. As long as the jewelry enterprises use the instruments correctly to find out the differences, Ability to accurately identify synthetic diamonds. As the most important country in the world for the production of HPHT synthetic diamonds, China's technological innovation acceleration, cost reduction, and expansion of uses (including jewelry) will be the general trend. Jewelry companies need to mark them correctly and confirm the attributes of the products before they are placed. "We strongly support synthetic diamonds to enter the consumer market through reasonable guidance, so that consumers have more freedom to choose, so that the jewelry industry is full of flowers." He particularly stressed.
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