Ultrahigh Pressure Technology

In 1970s GE pioneered the gem diamond growth by using belt apparatuses that were capable to sustain a pressure of 5.5 GPa (55,000 time of atmospheric pressure) and a temperature of 1300°C. The diamond was formed by feeding micron diamond fines to a molten catalyst of iron nickel alloy (Invar). The diamond fines were dissolved in the liquid and precipitated onto a diamond seed (Fig. 11.5).

GE diamonds were 1-2 carats after polishing. They could be colored or colorless depending on the dopant used in the catalyst. For example, the dopant free catalyst proceeded yellow diamond due to the incorporation of nitrogen from air. By adding a few PPM (part per million) of a nitrogen getter (e.g. titanium or zirconium), the diamond turned colorless (Fig. 11.6).

GE's gem diamond growth was costly and the process very slow. In 1980s, Sumitomo Electric used the similar technique to

Diamond Nanotechnology: Synthesis and Applications by James C Sung & Jianping Lin

Copyright © 2009 by Pan Stanford Publishing Pte Ltd

www.panstanford.com

978-981-4241-36-6

Figure 11.1. The brilliant cut of a gem diamond.
Figure 11.2. Rough diamond supply chain and its ecosystem.
Figure 11.3. The rough cut of natural diamond in 2006. The diamond gem market size was $63B that was compared to the ultimate jewelry sales of $143B.
Figure 11.4. The breakdown of diamond polishers and the segments of diamond gem market.

grow larger crystals. In 1990, De Beers grew gem diamond larger to more than 10 carats per crystal (Figs. 11.7 and 11.8).

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