[Zirconium or zirconium oxide/zirconium dioxide?].
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Zirconium dioxide
Zirconium alloy
Zirconium oxide
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Zirconium dioxide
Stoichiometry
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Semiconducting characteristics of oxide film on pure Zr, Zr-Sn binary alloy, and Zr-Sn-X (X: Fe, Ni, or Cr) ternary alloy were evaluated by a photo-electrochemical method to study the effects of alloying elements on the oxidation mechanism of Zr alloy in a boiling water reactor (BWR) environment. Oxide films of the alloys showed the characteristics of an n-type semiconductor. Maximum photocurrent (Imax) was generated by an illumination of monochromatic light with a photon energy of 5 to 6 eV (i.e., the band gap energy of the Zr oxide semiconductor was 5 to 6 eV). Higher corrosion-resistant alloys showed a lower value of Imax. Maximum photocurrent decreased by an addition of Fe, Ni, or Cr, notably Fe or Ni, to Zr-Sn alloy. By repetition of cold-working and α-annealing subsequent to β-quenching, Imax increased. Such changes of Imax caused by changes in alloy chemical composition and material processing, were explained by the valence theory of oxide semiconductors (i.e., the decrease of Imax was considered to result from the increase of holes in the oxides due to the substitution of divalent cations (Ni2+) and trivalent cations (Fe3+, Cr3+ ) at Zr4+ cation sites). From these results, the effects of alloying elements on the oxygen vacancy structure of the surface oxide were believed to play a major role in controlling the corrosion resistance of zirconium alloys.
Zirconium alloy
Zirconium oxide
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Zirconium alloy
Cladding (metalworking)
Precipitation hardening
Hardening (computing)
Strain hardening exponent
Environmental stress fracture
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Work hardening
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The processes of oxidation of zirconium and zirconium-base alloys in oxygen and air at temperatures up to 800 deg C were investigated. Electronographic analysis of oxidation of thin layers of zirconium helped establish polymorphism of ZrO/sub 2/ and temperature regions of existence of various modifications: cubic at 250 to 700 deg C; tetragonal at 700 to 900 deg C; and monoclinic over 1000 deg C. The same structural transformations were also disclosed in the oxide film on massive samples of zirconium. Kinetic examination of zirconium proved that the speed of oxidation increases abruptly during polymorphic transformations of the film of ZrO/sub 2/. It was observed that stresses in the oxide film play an important part in changing its structure. (auth)
Tetragonal crystal system
Monoclinic crystal system
Zirconium dioxide
Zirconium alloy
Zirconium oxide
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Zirconium dioxide
Zirconium alloy
Zirconium oxide
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Zirconium oxide
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Zirconium oxide
Zirconium alloy
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Ammonium sulfate
Zirconium oxide
Zirconium dioxide
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The reaction of Zircaloy in steam at elevated temperature involves the growth of discrete layers of oxide and oxygen-rich alpha Zircaloy from the parent beta phase. The multiphase, moving boundary diffusion problem involved is encountered in a number of important reaction schemes in addition to that of Zircaloy-oxygen and can be completely (albeitly ideally) characterized through an appropriate model in terms of oxygen diffusion coefficients and equilibrium concentrations for the various phases. Conversely, kinetic data for phase growth and total oxygen consumption rates can be used to compute diffusion coefficients. Equations are developed that express the oxygen diffusion coefficients in the oxide and alpha phases in terms of the reaction rate constants and equilibrium solubility values. These equations were applied to recent experimental kinetic data on the steam oxidation of Zircaloy-4 to determine the effective oxygen diffusion coefficients in these phases over the temperature range 1000--1500/sup 0/C.
Zirconium alloy
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