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Gas-Filled Inclusions in Materials

#G-838


The Experimental Investigation of Physical Parameters of Gas-filled Regions in Materials

Tech Area / Field

  • FIR-MAT/Materials and Materials Conversion/Fission Reactors
  • PHY-SSP/Solid State Physics/Physics

Status
3 Approved without Funding

Registration date
06.12.2001

Leading Institute
Tbilisi State University / Institute of Physics (Ge), Georgia, Tbilisi

Collaborators

  • Pacific Northwest National Laboratory, USA, WA, Richland

Project summary

For the last ten years the influence of radiation on physical properties of metals and alloys have been under active study. The importance of such investigations is conditioned, mainly, by technological aspects, as the radiation damages generated by neutrons or high-energy ions change significantly the physical and mechanical properties of structural materials, that in its turn should be considered for providing safety and reliability of nuclear reactors, as well as for creation of appropriate conditions for nuclear waste storage. Among the wide variety of radiation effects in metals and alloys the problems connected with the behavior of inert gas atoms formed as a result of neutron-induced transmutations in the materials of nuclear reactors, in particular in the fuel of nuclear reactors are of special interest.

The goal of the Project Proposal is the investigation of the influence of formation, growth and coalescence of gas precipitates consisting inert gas atoms on the physical properties of metals with different crystal structures, as well as the investigation of phase transitions in such precipitates.

The accumulation of inert gas atoms (such as He, Ar, Kr, Xe) in the material that practically do not dissolve in metallic matrix can lead to such undesirable phenomena as: embrittlement, void swelling, surface erosion, etc. A great attention is paid to the investigation of such phenomenon as helium blisters being in relation with the problem of creation of thermonuclear reactor, as the first wall and the elements of thermonuclear reactor will be subjected to the action of the fast neutrons, deuterium and tritium, as well as helium formed as a result of D-T reaction.

From the viewpoint of application the results of no less interest were obtained at the investigations of the behaviour of bubbles filled with the atoms of other inert gases (Ar, Kr, Xe) in metals. When the metallic crystals (practically all the metals of periodic table) are irradiated by 105-106 eV energy ions of heavy inert gases, the crystal grains are formed consisting of Ar, Kr, Xe. A great attention is paid to the investigation of this phenomenon, as the appearance of such bubbles, their growth and coalescence can result in such undesirable phenomenon as the material swelling.

Beside the application aspects the problem of precipitates of heavy inert gases in metals is of great interest from the physical point of view too, as in gas-containing materials there is observed such an interesting phenomenon as reversible phase transitions of solid-liquid type in the medium (precipitates) being under high pressure; the gas-contained metals give an unique possibility to investigate the nature of phase transition in medium being under high pressure.

Within the frames of the project the carrying out of calorimetric, acoustic, magnetic, thermogravimetric and electron microscopic investigations of gas contained metals are proposed in the wide range of temperature (4.2-1,100 K). It is supposed to choose Al, Cu and Ni with face-centered cubic structure, Nb with body-centered cubic structure, and Ti with hexagonal closely-packed structure as the objects under investigation. Implantation of inert gas atoms into investigated samples will be done by means of their irradiation on the accelerator by ions of He+, Ar+, Kr+ and Xe+ inert gases at ambient temperature, by fluence above the critical fluence of blister formation ~ 1021 m-2.

During project fulfillment following results will be expected:

– internal pressure in gas precipitates (Ar, Kr, Xe) for various metals (Al, Cu, Ni, Nb, Ti) will be determined;


– thermodynamical parameters of reversible phase transitions in gas precipitates (He, Ar, Kr, Xe) will be determined;
– diffusivity of ”inert gas atom–vacancy” complexes for various metals (Al, Cu, Ni, Nb, Ti) will be determined;
– stages of gas outlet from irradiated metals will be established.

It will be also obtained the results of following investigations:

– interaction of point defects with gas filled voids in irradiated metals;


– electron structure of gas-contained metals and the effect of defect microstructure on it.


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