by Staff Writers
Washington DC (SPX) Dec 21, 2011
The crushing pressures and intense temperatures in Earth's deep interior squeeze atoms and electrons so closely together that they interact very differently. With depth materials change. New experiments and supercomputer computations discovered that iron oxide undergoes a new kind of transition under deep Earth conditions. Iron oxide, FeO, is a component of the second most abundant mineral at Earth's lower mantle, ferropericlase.
The finding, published in an upcoming issue of Physical Review Letters, could alter our understanding of deep Earth dynamics and the behavior of the protective magnetic field, which shields our planet from harmful cosmic rays.
Ferropericlase contains both magnesium and iron oxide. To imitate the extreme conditions in the lab, the team including coauthor Ronald Cohen of Carnegie's Geophysical Laboratory, studied the electrical conductivity of iron oxide to pressures and temperatures up to 1.4 million times atmospheric pressure and 4000 degrees F-on par with conditions at the core-mantle boundary.
They also used a new computational method that uses only fundamental physics to model the complex many-body interactions among electrons. The theory and experiments both predict a new kind of metallization in FeO.
Compounds typically undergo structural, chemical, electronic, and other changes under these extremes. Contrary to previous thought, the iron oxide went from an insulating (non-electrical conducting) state to become a highly conducting metal at 690,000 atmospheres and 3000 degrees F, but without a change to its structure.
Previous studies had assumed that metallization in FeO was associated with a change in its crystal structure. This result means that iron oxide can be both an insulator and a metal depending on temperature and pressure conditions.
"At high temperatures, the atoms in iron oxide crystals are arranged with the same structure as common table salt, NaCl," explained Cohen.
"Just like table salt, FeO at ambient conditions is a good insulator-it does not conduct electricity. Older measurements showed metallization in FeO at high pressures and temperatures, but it was thought that a new crystal structure formed.
"Our new results show, instead, that FeO metallizes without any change in structure and that combined temperature and pressure are required. Furthermore, our theory shows that the way the electrons behave to make it metallic is different from other materials that become metallic."
"The results imply that iron oxide is conducting in the whole range of its stability in Earth's lower mantle."
Cohen continues, "The metallic phase will enhance the electromagnetic interaction between the liquid core and lower mantle. This has implications for Earth's magnetic field, which is generated in the outer core. It will change the way the magnetic field is propagated to Earth's surface, because it provides magnetomechanical coupling between the Earth's mantle and core."
"The fact that one mineral has properties that differ so completely-depending on its composition and where it is within the Earth-is a major discovery," concluded Geophysical Laboratory director Russell Hemley.
Space Technology News - Applications and Research
Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.
Infrared technology for measuring the effect of fire on materials
Madrid, Spain (SPX) Dec 21, 2011
The main problem associated with measuring the effects of fire on materials lies in the temperature of the flames, which reaches over 1000 C and can obscure the actual temperature of the material. In addition, there is the problem of the high concentration of gasses (CO2, H2O and others), which makes it difficult to obtain clear images of the sample being subjected to fire. In order to sol ... read more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement|