Introduction
Diamond, the hardest material known to man, is one of the most sought after resources throughout the centuries. From ancient times, this crystalline form of carbon has been mined, cut and fashioned into sparkling jewels, tools and other items of economic value. The crystalline lattice of diamond, based on its unique covalent bonds, appears indestructible by conventional means.
But diamond may also occur naturally through chemical and physical processes in the earths mantle, and in some cases, on the surface. This process is called diamond growth and is a result of a combination of intense temperature and pressure. Many theories exist that predict the formation of crystals, but science is still learning new information about these processes, as well as how they might be used to synthesize diamond in the laboratory.
Diamond growth in nature
Diamonds are thought to form when carbon atoms interact with the natural environment in a certain way. Carbon-bearing fluids, for instance, may interact with certain regions of the Earths mantle, to form small diamond grains. These grains grow when additional atoms may react with them, often adding atoms of other elements, such as nitrogen and boron, to the structure.
Exactly how this process occurs is still largely a mystery, but scientists think that it is due to a reaction between the fluids and certain minerals that are present in the mantle. As the temperature and pressure increase, the carbon in the fluids becomes increasingly concentrated, eventually crystallizing into a lattice structure, rather like a magnet.
This lattice structure could, in theory, become a diamond. However, there are other materials present which can prevent this from happening, such as graphite, which is another form of carbon, and other elements which may serve to reduce the diamond’s mass.
Diamond growth in laboratories
The science of growing diamonds in the lab has been steadily advancing in recent years, and a number of different methods have been developed to replicate the natural process in a controlled environment. Many of these techniques originated in Russia, but they have also been adopted in other countries.
The most basic method is known as the high-pressure, high-temperature (HPHT) technique. This involves subjecting graphite and other forms of carbon to very high temperatures and pressures in a vacuum chamber, which results in the formation of crystals (Figure 1).
Figure 1. The HPHT technique for creating diamond crystals.
Other methods are based on chemical vapor deposition (CVD) (Figure 2). In this technique, a substrate is heated in a vacuum chamber to a temperature where carbon atoms may be released. The atoms then form a lattice structure which can be used to create diamond crystals.
Figure 2. The CVD technique for creating diamond crystals.
Conclusion
From ancient times, diamond has been a precious and enduring resource. But the way in which it is produced has changed over the centuries. Due to ongoing research, we now have a better understanding of how diamonds are formed in nature, and how they can be created using laboratory techniques. This has opened up new possibilities for the production of diamonds and their use in numerous industries.
