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Defects, secondary phases, diffusion and transmutation in zirconium diboride

wallpapers News 2021-11-24
Defects and secondary phases in zirconium diboride
The high-temperature mechanical stability of zirconium diboride comes from the high atomic defect energy (that is, the atoms do not easily deviate from their lattice position). This means that even at high temperatures, the concentration of defects will remain at a low level, thereby preventing material failure.
The laminar bond between each layer is also very strong, but this means that the ceramic is highly anisotropic, with different thermal expansions in the "z". direction. Although the material has excellent high-temperature properties, the production of ceramics must be very careful, because any excess zirconium or boron cannot be contained in the ZrB2 lattice (ie the material does not deviate from stoichiometry). On the contrary, it forms a particularly low melting point phase, which may cause malfunctions under extreme conditions.
Diffusion and Transmutation in Zirconium Diboride
Due to the presence of boron and hafnium, zirconium diboride has also been studied as a possible material for nuclear reactor control rods.
The 10B + nth→[11B]→α + 7Li + 2.31 MeV layered structure provides a plane for helium diffusion. It is a transmutation product of boron-10 (boron-10 is the alpha particle in the above reaction). It will migrate rapidly in the lattice between the zirconium and boron layers, but not in the "z" direction. Interestingly, another transmutation product, lithium, is likely to be trapped in the boron vacancies created by the boron-10 transmutation, rather than being released from the crystal lattice.

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