Recent research on image crystals: Discovery of shape-controllable cavities surrounded by facets in ceramics

International Conference and Expo on Ceramics

August 17-18, 2015 Chicago, USA

Hiroyuki Serizawa

Scientific Tracks Abstracts: J Material Sci Eng

Abstract :

Author’s investigation on cavities in ceramics was triggered by the unexpected discovery of a polyhedral cavity in a UO2 matrix.
The SEM image that attracted author’s attention was a cavity observed in the fracture surface of a single crystal of UO2 that
was heat-treated in helium at 90 MPa, followed by annealing at 1573 K for 1 h. It was clear that the cavity was a negative crystal
that was formed by the precipitation of helium during heat treatment after Hot Isostatic Pressing (HIP) injection. In a series of
experiments, it was noticed that the shape of the negative crystal changes depending on the heat-treatment history. In general, it
is difficult to control arbitrarily the shapes of these polyhedral negative crystals embedded in a solid medium; however, the shape
can easily be controlled using the helium injection method. Author’s research team named the shape controlled negative crystal
as image crystal. At this time, it wasdiscovered that three types of image crystals formed in UO2. Further research was conducted
on the formation of image crystals in CeO2. However, because of manufacturing difficulties, single-crystal CeO2 is not available.
Consequently, it a CeO2 thin film formed by epitaxial growth was used. Helium was injected as 130-keV He4+ ions from a 400-
keV ion implanter. The helium-ion-doped film was heat treated at 1673 K for 2h. The sample was cut into rectangular slices for
transmission electron microscopy. We confirmed that nanosized image crystals had been formed in the matrix.

Biography :

Hiroyuki Serizawa obtained his PhD from Osaka University. He is a Research Scientist at the Japan Atomic Energy Agency. He was a guest researcher at the Joint Research
Centre’s Institute for Transuranium Elements, Germany (ITU) from 2000 for one year as a student sent abroad by the Ministry of Education, Culture, Sports, Science and
Technology. He has published more than 50 papers in reputed journals. His work on image crystals will be published by Nova Science Publishers in the near future.