Heal Thyself


Researchers at the Department of Energy's Pacific Northwest National Laboratory found that the restless movement of oxygen atoms heals radiation-induced damage in the engineered ceramic yttria-stabilized zirconia. Scientists modeled how well that ceramic and other materials stand up to radiation. They noted that materials capable of handling high-radiation doses also "could improve the durability of key equipment and reduce the costs of replacements."

The researchers approached their investigation in three steps. First, they analyzed yttria-stabilized zirconia, a compound of yttrium and zirconium oxides that contains random structural defects called "vacancies." The defects occur because yttrium has a smaller electrical charge than zirconium. To correct the charge imbalance, zirconia gives up oxygen atoms. But the loss of these oxygen atoms leaves empty oxygen sites. The remaining oxygen atoms constantly jump in and out of those sites.

Next, the scientists simulated an atom undergoing alpha decay. An alpha particle shoots out of the atomic nucleus with such force that the remainder of the atom recoils in the opposite direction. The recoiling atom can cause significant damage to surrounding atomic structures.

Finally, the researchers used data analysis algorithms developed at PNNL to look for atoms knocked out of place. The results showed that displaced oxygen atoms in the yttria-stabilized zirconia "found seats" in the pre-existing vacancies throughout the ceramic.

Although the self-healing activity does not completely repair the material, the defects are less apt to cause problems because they are spread out. This characteristic indicates that yttria-stabilized zirconia, which is used today in such items as solid oxide fuel cells and oxygen sensors, might be suitable for nuclear applications.

The scientists now are refining the simulations and applying them to other materials.

COMPAMED.de; Source: Pacific Northwest National Laboratory