| 1. |
- Brunell, I.F., et al.
(författare)
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In-situ stress measurement during the deposition of CN x thin films by unbalanced magnetron sputtering; formation of high levels of stress with 28 eV ion irradiation
- 2004
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 84:6, s. 395-403
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Tidskriftsartikel (refereegranskat)abstract
- Stress development during growth of CN x films by unbalanced magnetron sputtering has been investigated with an in-situ laser deflection technique. The stress is initially tensile, then it becomes compressive, reaching a maximum of as much as 7 GPa. These are anomalously high stress levels compared with pure carbon, considering the low ion energies (28 eV) and ion-to-neutral arrival rate ratio (<1) employed. This phenomenon is explained by the formation of a fullerene-like microstructure and nitrogen substitution at the growth surface. An accompanying increased reactivity of carbon atoms promotes sp3 bonding or other cross-linking of curved basal planes with resulting film densification.
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| 2. |
- Chen, Chun Lin, et al.
(författare)
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In situ TEM observation of decomposition of high-purity sapphire
- 2009
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 89:2, s. 113-119
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Tidskriftsartikel (refereegranskat)abstract
- The decomposition of agr-Al2O3 under 200 keV electron irradiation has been investigated by in situ high-resolution electron microscopy (HREM). It was confirmed that aluminium precipitated from agr-Al2O3 under 200 keV electron irradiation for less than 1 min over the temperature range from 700 to 1273 K. The electron dose rate was of the order of 1023 e m-2 s-1 and the vacuum level of the microscope was better than 10-6 Pa. The mechanisms of agr-Al2O3 decomposition were discussed based on two possible decomposition models: the thermally activated atom movement and the forced atom displacement
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| 3. |
- Ghassemali, Ehsan, 1983-, et al.
(författare)
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Dynamic precipitation at elevated temperatures in a dual-phase AlCoCrFeNi high-entropy alloy : an in situ study
- 2018
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Ingår i: Philosophical Magazine Letters. - : Taylor & Francis. - 0950-0839 .- 1362-3036. ; 98:9, s. 400-409
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a possible phase transformation or precipitation of the face-centred cubic (FCC) phase on intermediate-temperature deformation of a dual-phase AlCoCrFeNi high-entropy alloy has been studied using in situ tensile testing at 550°C. Electron backscatter diffraction (EBSD) results showed localised precipitation of the FCC phase during the intermediate-temperature deformation. The overall fracture behaviour and crack propagation of the material was not altered much compared to the room-temperature behaviour, namely brittle trans-granular fracture. Deformation at higher temperatures (above 750°C) is suggested as a way to enhance the dynamic FCC phase precipitation, in order to improve the ductility or deformability of the alloy.
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| 4. |
- Gutiérrez, R., et al.
(författare)
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The formation of nanopipes caused by donor impurities in GaN: A theoretical study for the case of oxygen
- 1999
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 79:3, s. 147-152
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Tidskriftsartikel (refereegranskat)abstract
- Local density-functional methods are used to examine the behaviour of O and O-related defect complexes at {1010}-type surfaces in GaN. We find that O has a tendency to segregate to the (1010) surface and we identify the gallium vacancy surrounded by three oxygen impurities (VGa-(ON)3) to be a particularly stable and electrically inert complex. We suggest that these complexes impede growth at the walls of the nanopipes preventing them from growing in. Also, other donor-related defect complexes, in particular gallium vacancies surrounded by three silicon atoms as second nearest neighbours, are expected to have the same effect.
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| 5. |
- Hörnqvist Colliander, Magnus, 1979, et al.
(författare)
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Complete precipitate dissolution during adiabatic shear localisation in a Ni-based superalloy
- 2020
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 100:12, s. 561-570
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Tidskriftsartikel (refereegranskat)abstract
- Whereas microstructure evolution in adiabatic shear bands have been thoroughly studied, reports on the stability of hardening precipitates during shear localisation are scarce. We report an atomic scale investigation of solute distribution in adiabatic shear bands in a precipitation strengthened Ni-Fe-based superalloy, showing that the hardening particles are completely dissolved. Temperature estimations indicate that peak temperatures in the shear band above the solvus limits of the precipitates are not unrealistic, and thus diffusion-assisted transformations during the severe plastic deformation cannot be ruled out.
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| 6. |
- Johansson, Sven, 1981, et al.
(författare)
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Theory of ultrathin films at metal-ceramic interfaces
- 2010
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 90:8, s. 599-609
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model for understanding the formation of interfacial thin films is presented, which combines density functional theory calculations for interface energies with thermodynamic modeling techniques for multicomponent bulk systems. The theory is applied to thin film formation in VC-doped WC-Co cemented carbides. It is predicted that ultrathin VC films may exist in WC/Co interfaces at the high temperature sintering conditions where most of the WC grain growth occurs, which provides an explanation of the grain growth inhibiting effect of VC additions in the WC-Co system.
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| 7. |
- Jones, R, et al.
(författare)
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Ab initio calculations of the structure and dynamics of C60 and C3- 60
- 1992
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 65:6, s. 291-298
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Tidskriftsartikel (refereegranskat)abstract
- A local-density-functional cluster method is used to calculate the structure and vibrational modes of C60. We find C–C lengths in good agreement with observed values. The effect of doping the molecule with three extra electrons is investigated and shown to result in a surprising shortening of the longer bonds. The second derivatives of the energy are evaluated and have enabled, for the first time, all the normal modes of the molecule to be found. We find these to be in fair agreement with the available experimental results.
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| 8. |
- Jones, R., et al.
(författare)
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First-principles theory of nitrogen aggregates in diamond
- 1992
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 66:2, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- Local-density-functional theory is used to evaluate the structure, vibrational bands and electronic properties of two point defects in diamond a pair of adjacent substitutional N atoms and a vacancy surrounded by four N atoms. These defects are important as they are possible models of the A and B centres seen in type Ia diamond. For the A centre we find a N─N bond length of 2·14 Å, an occupied electronic energy level near midgap and four infrared absorption bands with frequencies close to the experimental values. For the model of the B centre we find a N─C length of 1·49 Å an occupied triplet electronic level within the gap consistent with the recent suggestion that the N9 absorption band is due to this defect and again vibratory modes in close agreement with experiment. These results provide strong evidence as to the validity of the models for the A and B centres.
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| 9. |
- Joseph, Ceena, 1982, et al.
(författare)
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Precipitation of γ’ during cooling of nickel-base superalloy Haynes 282
- 2021
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 101:1, s. 30-39
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Tidskriftsartikel (refereegranskat)abstract
- Cooling-induced precipitation of the strengthening γ’ phase is commonly investigated in Ni-base superalloys with a high γ’ volume fraction, where it is used to control the final microstructure and properties. Less is known about the phase separation in low-volume-fraction alloys during cooling, although the microstructural state after cooling from solution treatment is known to affect subsequent heat-treatment steps. We use atomic-scale characterisation of Ni-base superalloy Haynes 282 (equilibrium γ’ volume fraction around 20%) to show that air cooling after solution or carbide stabilisation results in precipitation of nm-sized γ’ particles, whereas precipitation was suppressed during water quenching. The solution treatment has a significant effect on the hardness and γ’ precipitation during air cooling from the subsequent carbide stabilisation temperature. Also, the carbide-stabilisation treatment itself affects the γ’ precipitation during subsequent air cooling.
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| 10. |
- Mathieu, Roland, et al.
(författare)
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Isothermal remanent magnetization and the spin dimensionality of spin glasses
- 2010
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Ingår i: Philosophical Magazine Letters. - : Informa UK Limited. - 0950-0839 .- 1362-3036. ; 90:10, s. 723-729
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Tidskriftsartikel (refereegranskat)abstract
- The isothermal remanent magnetization is used to investigate dynamical magnetic properties of spatially three-dimensional spin glasses with different spin dimensionality (Ising, XY, Heisenberg). The isothermal remanent magnetization is recorded versus temperature after the application of a weak magnetic field at a constant temperature T-h. We observe that in the case of the Heisenberg spin glasses, the equilibrated spin structure and the direction of the excess moment are recovered at T-h. The isothermal remanent magnetization thus reflects the directional character of the Dzyaloshinsky-Moriya interaction present in Heisenberg systems.
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