Experiments under high pressure investigate material changes that are not found in most of the universe. At the Carnegie Institute for Science, it was seen that the materials sandwiched between two diamonds went through a process reminiscent of alchemy. Iron does not turn into gold though. But familiar atoms and molecules behave differently. Oxygen turns blue, then red, and finally a shiny metal. Peanut butter becomes diamond, as General Motors demonstrated in a pioneering work in the 1950s. So are roof pitch and wood. But Russell J. Hemley and his colleagues don't do it by magic.
Interest in high pressure science in the Geophysical Laboratory at the Carnegie Institution arose from the laboratory's mission to study the depths of the Earth. Currently, scientists are looking at transformations under high pressure, investigating material changes that are not found in most of the universe; He's trying to illuminate what's going on deep inside Earth or Jupiter. And they hope these experiments will reveal new materials that can more efficiently capture sunlight in electricity-generating solar cells or serve as fuel tanks in hydrogen-powered cars. “This is a new type of chemistry,” Hemley says. It is certain that the term “high pressure” takes on a new meaning in these circumstances. Air pressure at sea level is about one kilo per square centimeter. In diamond anvils at the Carnegie Institution, a pressure of over 3,5 million pounds per square centimeter is applied.
Moreover, researchers in Germany have developed methods that double that. However, there are even more overwhelming forces in some parts of the universe. The pressure at the center of Jupiter is more than 70 million kilograms per centimeter. There are also neutron stars, the remnants of suns that have run out of fuel, whose atoms so close together by their gravitational pull create a pressure a billion trillion times greater than that in Jupiter's core. The anvils used in Carnegie and other labs look simple. Although their designs vary, they are housed in cylindrical metal cases measuring 5 cm by 2,5 cm. To apply pressure, scientists tighten the top screws, bringing the lower and upper plates closer together. As the plates bend, the tips of the two small diamonds come closer together. One end has a slot that holds the material to be compressed, and the other end presses right there, like a thin heel crushing an insect. Even if the screws apply only a few pounds of force, they turn into tremendous pressure because the diamond bits are tiny. We can compare this to riding a hundred elephants on the tip of a pen; If only there was a pen that so many elephants could ride on. Therefore, diamonds should not have even a small crack or flaw. At reasonable pressures, the atoms line up neatly, like cannonballs. That's why scientists expected them to line up like this again in experiments. But later it was seen that although the distance between them does not decrease, the atoms do not stand in a regular row. For example, sodium goes into a complex order.
Normally circulating in pairs, like dumbbells, nitrogen takes the form of a twisted cage. As the atoms get closer to each other, the electrons jump in different directions and give different shapes to the molecules they are in. Dr. In Hemley's words, "In a way, a new periodic table emerges". Even noble gases such as xenon, which rarely interact with other atoms, mingle with hydrogen to form new structures. Malcolm McMahon of the University of Edinburgh in Scotland is interested in red oxygen. His team obtained a single ruby-colored oxygen crystal inside an anvil. Oxygen atoms, which are usually bonded together in pairs, form octal clusters. This structure absorbs the shorter blue wavelengths of light. The remaining wavelengths (red) were passing through it. Under even more intense pressure, the oxygen turns into metal. But perhaps the biggest enigma is the simplest and most abundant hydrogen atom.
Under very high pressures in the center of Jupiter, hydrogen turns into a liquid metal; The magnetic field on the planet is thought to be caused by the activity there. But findings in the lab cast doubt on that. NASA's Juno spacecraft, which is going to Jupiter, may be able to illuminate the depths of this planet with its measurements. His data and laboratory experiments can help explain each other. “We want to understand the long-term behavior of hydrogen under all conditions,” Hemley says.
source : morning
📩 30/12/2013 22:53