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Possible origin and roles of nano-porosity in ZrO2 scales for hydrogen pick-up in Zr alloys

Mikaela Lindgren (Institutionen för kemi och kemiteknik, Oorganisk miljökemi) ; Christine Geers (Institutionen för kemi och kemiteknik, Oorganisk miljökemi) ; Itai Panas (Institutionen för kemi och kemiteknik, Oorganisk miljökemi)
Journal of Nuclear Materials (0022-3115). Vol. 492 (2017), p. 22-31.
[Artikel, refereegranskad vetenskaplig]

A mechanistic understanding of Wagnerian build-up and subsequent non-Wagnerian break-down of barrier oxide upon oxidation of zirconium alloys by water is reiterated. Hydrogen assisted build-up of nano-porosity is addressed. Growth of sub-nanometer wide stalactitic pores owing to increasing aggregation of neutral oxygen vacancies offering a means to permeate hydrogen into the alloy is explored by density functional theory. The Wagnerian channel utilizes charge separation allowing charged oxygen vacancies and electrons to move separately from nominal anode to nominal cathode. This process becomes increasingly controlled by the charging of the barrier oxide resulting in sub-parabolic rate law for oxide growth. The break-down of the barrier oxide is understood to be preceded by avalanching hydrogen pick-up in the alloy. Pore mediated diffusion allows water to effectively short circuit the barrier oxide.

Nyckelord: Zirconium oxidation, Hydrogen pick-up, Porosity, DFT, Oxygen vacancy, Nucleation



Denna post skapades 2017-08-14.
CPL Pubid: 251077

 

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Institutioner (Chalmers)

Institutionen för kemi och kemiteknik, Oorganisk miljökemi

Ämnesområden

Oorganisk kemi

Chalmers infrastruktur