Pressure: The Extremes
There are places here on earth, not just in the ocean, and elsewhere in the solar system where there are stunningly high pressures. The center of the sun is a good example. There are processes that we would like to understand that happen in those environments. It would be nice to understand how the inside of a star works or the behavior of materials buried deep in the earth. Diamonds are both formed in such environments and are part of the equipment we use to study high pressure processes.
Much like the idea we talked about in the very begining with the difference between a sharp and a dull knife. If you take a large force from a hydraulic press and then reduce the area of contact between the anvils you can achieve remarkable pressures. It is normal in metals manufacturing to create pressures that are large enough to make metal move like peanut butter. So what can we do to create higher pressures if the metals are going to flow? If we replace the metal anvils with diamonds, which are the hardest known material, we can acheive higher pressures than with metal anvils. Diamonds have the added advantage of being transparent so we can look into the tiny high pressure region we are creating to 'see' what is happening. At this time we can achieve pressures of 100-200 GPa which is roughly 1 million atmospheres. Truly remarkable. The image at the top of the page is of the diamond anvil in such a machine.
Diamonds themselves are formed in a hot high pressure environment deep in the earth. There has been lots written about the natural formation process for diamonds. It is no surprise, given the value of diamonds, that folks have been trying to make synthetic diamonds as soon as we had some sense of how they were formed. The pressures needed to this are in the range of 100,000 atmospheres so we can get these with mechanical equipment. Most diamonds formed this way are not gem quality but are used in a whole range of industrial tooling.
Interestingly we have also developed other processes for growing diamonds that do not rely on very high pressures and heat which have resulted from our better understanding of how crystals grow. That's a discussion to have with a crystallographer which I am not.
