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45 results on '"Cao, X.Z."'

36. Thermal desorption of helium from defects in nickel

Author

Cao, X.Z., Xu, Q., Sato, K., and Yoshiie, T.

Subjects
dissociation energy, Condensed Matter::Materials Science, helium bubbles, dislocation, Physics::Atomic and Molecular Clusters, thermal desorption, Physics::Atomic Physics, helium, vacancy, helium-vacancy clusters
Abstract

Helium atoms, introduced into materials by helium plasma or generated by the (n, α) nuclear reaction, have a strong tendency to accumulate at trapping sites such as vacancy clusters and dislocations. In this paper, the effects of dislocations, single vacancies and vacancy clusters on the retention and desorption of helium atoms in nickel were studied. Low energy (0.1–0.15 keV) helium atoms were implanted in nickel with vacancies or dislocations without causing any displacement damage. He atoms, interstitial-type dislocation loops, and vacancy clusters were also introduced with irradiation damage by 5.0 keV helium ions. Helium thermal desorption peaks from dislocations, helium-vacancy clusters and helium bubbles were obtained by thermal desorption spectroscopy at 940 K, in the range from 900 to 1370 K, and at 1500 K, respectively. In addition, a thermally quasi-stable state was found for helium-vacancy clusters.

Published
2011

37. Effects of alloying elements on defect structures in the incubation period for void swelling in austenitic stainless steels

Author

30378971, 90273531, Horiki, M., Yoshiie, T., Huang, S.S., Sato, K., Cao, X.Z., Xu, Q., Troev, T.D., 30378971, 90273531, Horiki, M., Yoshiie, T., Huang, S.S., Sato, K., Cao, X.Z., Xu, Q., and Troev, T.D.

Abstract

Positron lifetime measurements were used to study the effects of alloying elements on the defect structure during the incubation period for void swelling in several fcc model alloys. Pure Ni, four model alloys (Fe–Cr–Ni, Fe–Cr–Ni–Mo–Mn, Fe–Cr–Ni–Mo–Mn–Si and Fe–Cr–Ni–Mo–Mn–Si–Ti), and four commercial alloys (SUS316LSS, SUS316SS, SUS304SS and Ti added modified SUS316SS) were irradiated with electrons and neutrons. Even at 363 and 573 K to a dose of 0.2 dpa, an effect of alloying elements was observed. At 363 K irradiation, voids were formed only in Ni and Fe–Cr–Ni. At 573 K irradiation, voids were formed in Ni and all model alloys, though the concentration depended on the alloying elements. In commercial alloys, precipitates were formed instead of vacancy clusters, which prevented void growth.

Published
2013

38. Effects of alloying elements on thermal desorption of helium in Ni alloys

Author

90273531, 30378971, Xu, Q., Cao, X.Z., Sato, K., Yoshiie, T., 90273531, 30378971, Xu, Q., Cao, X.Z., Sato, K., and Yoshiie, T.

Abstract

It is well known that the minor elements Si and Sn can suppress the formation of voids in Ni alloys. In the present study, to investigate the effects of Si and Sn on the retention of helium in Ni alloys, Ni, Ni–Si, and Ni–Sn alloys were irradiated by 5 keV He ions at 723 K. Thermal desorption spectroscopy (TDS) was performed at up to 1520 K, and microstructural observations were carried out to identify the helium trapping sites during the TDS analysis. Two peaks, at 1350 and 1457 K, appeared in the TDS spectrum of Ni. On the basis of the microstructural observations, the former peak was attributed to the release of trapped helium from small cavities and the latter to its release from large cavities. Small-cavity helium trapping sites were also found in the Ni–Si and Ni–Sn alloys, but no large cavities were observed in these alloys. In addition, it was found that the oversized element Sn could trap He atoms in the Ni–Sn alloy.

Published
2012

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