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William Atkins
Tuesday, 20 March 2007 02:37
Sandia researchers Daniel Dolan, Chris Deeney, Mark Knudson, and Clint Hall took part in the research on nanosecond ice production.
The Sandia Z machine makes ice by sending twenty million amperes of electrical pulses through water held in a small aluminum chamber under extreme compression. Compressing water normally heats it, but when it is under extreme compression it is easier for the dense water to turn into its solid phase, or ice. More specifically, this ice is called ice VII (ice seven), a phase of water that is formed from liquid water at pressures above 3 GPa (gigapascal)—or about 30,000 atmospheres [atm]—by lowering its temperature to ambient (normal experimental room) temperatures.
We are familiar with three phases of water: solid (ice), liquid (water), and gas (vapor). However, under extreme pressures and temperatures, water can take on at least 11 other phases. And, even though it is ice, the ice produced by the Scandia scientists is hotter than the boiling point of water, which is approximately 100 degrees Celsius (212 degrees Fahrenheit or 373.15 Kelvin)
The Scandia researchers cite that the water was compressed to pressures of 50,000 to 120,000 atm in less than 100 nanoseconds. For a comparison, when we stand at sea level on the surface of the Earth, we have about 1 atmosphere of pressure pressing against us. A diver about ten meters (30 feet) below the water's surface is at about 2 atmosphere of pressure.
Below 70,000 atm, the water was opaque (cloudy), indicating that it was still part liquid water and ice. However, at 70,000 atm, the water became clear, a sign that the U.S. government scientists say indicates the water was now entirely ice.
Such studies are important to scientists because it helps to understand how materials react when placed under extreme conditions. It has applications in defense, manufacturing, and other areas where materials are used, made, and altered under extreme conditions.
The article stating the results of the Sandia Z experiment appears in the March 11, 2007 online edition of Nature Physics.
More information about Scandia National Laboratories is found at: http://www.sandia.gov/.
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