[en] A simple scheme with the single-particle resonant continuum coupling and pairing correlations, is applied to describe the formation of the giant halo for neutron-rich even-even Zr isotopes by the resonant BCS model within the relativistic mean field framework. Resonance parameters and wave functions are extracted from the effective analytic continuation in the coupling-constant approach. It can be seen that the sudden increase of the neutron radii close to the neutron drip line is due to a few resonant states in the vicinity of the Fermi surface. (orig.)

[en] Q values are reported for (d,t) reactions on all the stable isotopes of zirconium. The neutron separation energies of ⁹⁴Zr and ⁹⁶Zr differ greatly (by 27.5 and 22.1 keV, respectively) from the values in the 1971 Atomic Mass Evaluation. These results combined with those from other authors seem to indicate that the 1971 values for the masses of ⁹³Zr and ⁹⁵Zr are in error. (orig.)

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[en] The isotopic composition of zirconium in the normal shelf reagent and in two terrestrial rock standards, W-1 and G-2, has been determined. In the course of this study, the mass spectrometric measurements were checked by artificial mixtures of ⁹⁰Zr-, ⁹¹Zr-, ⁹²Zr- and ⁹⁴Zr-enriched isotopes. The absolute isotopic abundance obtained in this work is as follows (atom%); ⁹⁰Zr: 51.449+-0.059; ⁹¹Zr: 11.320 +- 0.015; ⁹²Zr: 17.189 +- 0.021; ⁹⁴Zr: 17.283 +- 0.021; and ⁹⁶Zr: 2.759 +- 0.004. Because of the higher accuracy, these abundances should replace the currently accepted values. The corresponding atomic weight of zirconium was calculated to be 91.219. This shows good agreement with the currently accepted value of 91.22 by IUPAC (1975), although the isotopic composition differs slightly from the IUPAC 'intrim' values. From nine chondrites, belonging to various classes, zirconium was extracted and the isotopic composition was determined. By the present technique, the limit of the experimental error for a single measurement of each sample, 2sigma approximately 0.5%, prevents detection of possible incomplete mixing during and after nucleosynthesis and following the formation of the solar system. (Auth.)

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[en] The allotropic transformation hcp(α) in equilibrium bcc(β) was examined in crystal bar zirconium. The β → α transformation is massive type in melt grown crystals of β--Zr. Upon thermal cycling through α → β → α the bcc → hcp transformation occurs frequently through a shear process and less frequently through a massive transformation. The presence of α → β transformation substructure may favor the operation of the shear mode. The hcp → bcc phase change occurs through a massive transformation. A lack of transformation memory is associated with the process of thermal cycling. 11 fig., 3 tables

[en] The effect of fluoride ions on the corrosion behavior of zirconium in concentrated nitric acid medium was studied by electrochemical technique. Zirconium was observed to exhibit pseudopassive behavior in fluorinated nitric acid, as the current density measured from the potentiodynamic polarization study was several orders of magnitude higher than the value in fluoride-free nitric acid. The data obtained from Electrochemical Impedance Spectroscopic (EIS) studies on zirconium sample exposed to 11.5 M HNO_3 for 240 h were modeled using the (R_S(QR_P)) equivalent circuit. The EIS analysis confirmed the formation of the passive film with high polarization resistance (RP) and the calculated thickness of the film based on the capacitance value was about ∼ 4.5 nm

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