|
|
Because of their transparency, thermal conductivity, or surface properties, diamonds are used in many research instruments as windows. An application of exceptional value in mineral and material science is a small device that generates extremely great pressures in the space between two diamonds - the diamond anvil cell. These devices are used in experiments on the nature of planetary interiors and dense matter, from mimicking Earth's core to producing solid hydrogen.
Alvin Van Valkenburg, pictured here in 1963, was a pioneer in using the diamond anvil cell to study materials at high pressure at the National Bureau of Standards, Washington DC.
|
The mechanics of creating high pressure are simple, involving just an application of force onto a small area, but extreme pressure will not be achieved without a material of supreme hardness, incompressibility, and strength - such as diamond. Most materials, steel for example, will deform or break before reaching pressures that exist deep within Earth. Tungsten carbide is better, but diamond is best. By polishing the ends off two fine round brilliant diamonds to a width of a millimeter or so, and carefully and accurately squeezing them together, pressures comparable to the center of Earth - 4,500,000 atmospheres - can be achieved. At these pressures hydrogen transforms into a metal - a state that might exist deep within Jupiter. Research on planetary interiors and dense matter has been advanced greatly by the use of diamond anvil cells, using lasers, optics, and x-rays to probe these small samples to reveal their mysteries.
 |
 |
The diagram above illustrates the principle of the diamond anvil cell, and opposite it is a photomicrograph of an actual diamond anvil. To contain the pressurized area, a small donut-shaped metal gasket is placed between the diamond anvils. Conditions are probed with x-rays, light, and lasers; the last are used to heat the small samples to simulate Earth conditions.
An early diamond anvil cell for optical studies used the lever-arm diamond anvil cell, as diagrammed here: by the application of leverage a turn of a screw could create many thousands of atmospheres of pressure. click to zoom in
Photographs courtesy Geophysical Laboratory, Carnegie Institution of Washington
|
