China 
Africa 
Explore chapters and articles related to this topic
High-Pressure Study of Phosphors Emission
Published in Ru-Shi Liu, Xiao-Jun Wang, Phosphor Handbook, 2022
Typical anvils are made of high gem-quality natural or synthetic diamonds. Diamonds are polished according to the (1 0 0)-crystal orientation, usually cut with 16 facets. The larger face of diamond (table) diameter ranges from 2.5 to 4 mm, with typical weight varies between 0.1 and 0.33 carat (20 and 67 mg). Depending on the cell type, the bottom (table) of the diamond can be flat, or it may have bevels.
Introduction
Published in Roshan L. Aggarwal, Anant K. Ramdas, Physical Properties of Diamond and Sapphire, 2019
Roshan L. Aggarwal, Anant K. Ramdas
The density of diamond is 3.515 g/cm3; that is, it has a C12 concentration of 1.762 × 1023 cm−3. The weight of diamonds is expressed in carats. One carat is equal to 200 mg and has a volume of 56.9 mm3.
Past, present, and the future of the research and commercialization of CVD diamond in China
Published in Functional Diamond, 2022
Technically, the emergence of the MWCVD diamond film deposition systems working at high pressure and high power in the late 1990s had laid down the foundation for the rapid advancement in the R&D of the large size high quality single crystal diamonds in the first decade of the twenty first century [127,128]. Soon after, commercial CVD diamonds appeared in the jewel market in 2012 [127]. Single crystal CVD diamond companies in Singapore and USA had begun selling CVD diamond jewelry in the world market. However, the size of the CVD diamonds was small (0.3-0.7 carat). In the same time period, numerous companies and organizations for the production of the CVD single crystal diamond had emerged in China. In 2015, a 5.09 carat CVD diamond of color J, and clarity VS2 only was sent to IGI for examination. In the same year, ISO claimed that the phrase “Laboratory Grown Diamond” and “Synthetic Diamond” were synonymous. Then the phrase “synthetic diamond” was replaced by “Laboratory Grown Diamond” (LGD). In 2018, FTC (Federal Trade Committee) recognized that the laboratory grown diamond belonged to the diamond categories. This meant that the laboratory grown diamond had already been accepted by the consumers. On 17 March 2020, the IGI claimed that it has received a 7.06 carats high quality laboratory grown colorless diamond, with color F, clarity VVS2 and cut 3EX. This diamond was from the Hangzhou Chao Ran Diamond Technology Ltd. China and was considered as the biggest high-quality laboratory grown diamond in the world [129]. It indicated the maturity of the large carat laboratory grown diamond. However, only 4 months later, this world record was broken again by another Chinese company, the Shanghai Zhenshi Technology Ltd. It sent a 10.57 carat colorless laboratory grown diamond with F color, VVS2 clarity and 3EX cut to the IGI for examination on 10 July 2020. As claimed by the IGI, the as-grown blank weighed 45.152 carat. Then the 10.57 carat diamond became the world largest high-quality laboratory grown diamond (Figure 9) [130]. At present, the HPHT LGD in China has remained as the world first position for three years, whilst the CVD LGD in China is also moving fast. It is estimated that the MWCVD systems for the growth of the LGD in China will reach 2500-3000 units by the end of this year [125]. However, this number is almost the same as predicated in India in 2022 [128]. Since the predicted annual output for India in 2022 is 6 M carat, the estimated output of 1.5 M carat in 2022 in China [126] is apparently underestimated. The major difference between the HPHT and the CVD LGD is that: the CVD LGD is usually of larger size and of better quality as compared to the HPHT LGD. However, the growth of the large carat CVD LGD is not easy. Up to now, only a few companies are capable of producing it. Both the HPHT and the CVD techniques are now nearly fully mature. The future of the LGD will be determined by the market, i.e. the extent of the acceptance of the consumers. However, it is reported that at present 80% of the LGD were consumed in US market and that only about 10% were sold in China [126]. Therefore, the future of the laboratory gown diamond (LGD) will be very bright.