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- Azadian, Saied, et al.
(författare)
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Delta Phase Precipitation in Inconel 718
- 2004
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Ingår i: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; :52, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- The precipitation and dissolution kinetics of the δ-phase were studied in three wrought versions and one spray-formed (SF) version of the nickel alloy, Inconel 718. The precipitation in the spray-formed version and one wrought version was followed during isothermal ageing for up to 100 h between 700 and 1000 °C. The δ-phase precipitates in the form of nonuniformly distributed thin platelets and an alternative method of measuring volume fraction of this precipitate morphology is proposed. At and above 800 °C, the precipitation was measured quantitatively in terms of the volume fraction and platelet thickness distribution. The maximum rate of precipitation occurred at approximately 900 °C. The solvus temperature lay between 1005 and 1015 °C for Nb contents of 5.06 and 5.41 wt.%, respectively. A study was made of the dissolution of the δ-phase in all four alloys using isochronal treatments and this confirmed the above solvus temperature range. The effect of δ-phase and its dissolution on the grain growth of the alloys was also determined.
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- Azadian, S., et al.
(författare)
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Precipitation in spray-formed IN 718
- 2001
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Ingår i: Superalloys 718, 625, 706 and various derivatives. - Warrendale, Pa : Minerals, Metals & Materials Society. ; , s. 617-626
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Konferensbidrag (refereegranskat)abstract
- The precipitation of the γ', γ'' and δ phases in a spray-formed version of IN 718 has been studied by hardness measurement and metallographic examination of samples subjected to solution treatment at 1025°C followed by isothermal treatments between 620 and 1010°C up to 100 h. The precipitation processes were compared to those in a wrought (ring-rolled) version of the alloy subjected to the same heat treatments. Time-temperature-hardness diagrams for the two alloys were constructed. Small differences were observed between the two materials but these can at least partly be attributed to differences in composition. For the spray-cast material the δ-phase solvus temperature was determined and the growth kinetics of the γ'' phase established
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- Azadian, Saied, et al.
(författare)
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Precipitation in spray-formed IN718
- 2001
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Ingår i: Proceedings of Fifth International Special Emphasis Symposium on Sureralloys. - : The Minerals, Metals, and Materials Society. ; , s. 617-626
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Konferensbidrag (refereegranskat)
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| 9. |
- Berggren, Diana, et al.
(författare)
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Spontaneous hair-cell renewal following gentamicin exposure in postnatal rat utricular explants
- 2003
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Ingår i: Hearing Research. - 0378-5955 .- 1878-5891. ; 180:1-2, s. 114-125
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Tidskriftsartikel (refereegranskat)abstract
- We have established an in vitro model of long-time culture of 4-day-old rat utricular maculae to study aminoglycoside-induced vestibular hair-cell renewal in the mammalian inner ear. The explanted maculae were cultured for up to 28 days on the surface of a membrane insert system. In an initial series of experiments utricles were exposed to 1 mM of gentamicin for 48 h and then allowed to recover in unsupplemented medium or in medium supplemented with the anti-mitotic drug aphidicolin. In a parallel control series, explants were not exposed to gentamicin. Utricles were harvested at specified time points from the second through the 28th day in vitro. Whole-mount utricles were stained with phalloidin-fluorescein isothiocyanate and their stereociliary bundles visualized and counted. In a second experimental series 2'-bromo-5'deoxyuridine labeling was used to confirm the antimitotic efficacy of aphidicolin. Loss of hair-cell stereociliary bundles was nearly complete 3 days after exposure to gentamicin, with the density of stereociliary bundles only 3-4% of their original density. Renewal of hair-cell bundles was abundant (i.e. 15x increase) in cultures in unsupplemented medium, with a peak of stereociliary bundle renewal reached after 21 days in vitro. A limited amount of hair-cell renewal also occurred in the presence of the anti-mitotic drug, aphidicolin. These results suggest that spontaneous renewal of hair-cell stereociliary bundles following gentamicin damage in utricular explants predominantly follows a pathway that includes mitotic events, but that a small portion of the hair-cell stereociliary bundle renewal does not require mitotic activity.
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- Chen, Wei, et al.
(författare)
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Energy structure and fluorescence of Eu2+ in ZnS:Eu nanoparticles
- 2000
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Ingår i: Physical Review B. - 1098-0121. ; 61:16, s. 11021-11024
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Tidskriftsartikel (refereegranskat)abstract
- Eu2+-doped ZnS nanoparticles with an average size of around 3 nm were prepared, and an emission band around 530 nm was observed. By heating in air at 150 degrees C, this emission decreased, while the typical sharp line emission of Eu3+ increased. This suggests that the emission around 530 nm is from intraion transition of Eu2+: In bulk ZnS:Eu2+, no intraion transition of Eu2+ was observed because the excited states of Eu2+ are degenerate with the continuum of the ZnS conduction band. We show that the band gap in ZnS:Eu2+ nanoparticles opens up due to quantum confinement, such that the conduction band of ZnS is higher than the first excited state of Eu2+, thus enabling the intraion transition of Eu2+ to occur.
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