| 1. |
|
|
| 2. |
- Joffrin, E., et al.
(författare)
-
Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
-
Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Cedervall, Johan, et al.
(författare)
-
Magnetocaloric effect in Fe2 P: Magnetic and phonon degrees of freedom
- 2019
-
Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 99:17
-
Tidskriftsartikel (refereegranskat)abstract
- Devices based on magnetocaloric materials provide great hope for environmentally friendly and energy efficient cooling that does not rely on the use of harmful gasses. Fe2P based compounds are alloys that have shown great potential for magnetocaloric devices. The magnetic behavior in Fe2P is characterized by a strong magnetocaloric effect that coexists with a first-order magnetic transition (FOMT). Neutron diffraction and inelastic scattering, Mossbauer spectroscopy, and first-principles calculations have been used to determine the structural and magnetic state of Fe2P around the FOMT. The results reveal that ferromagnetic moments in the ordered phase are perturbed at the FOMT such that the moments cant away from the principle direction within a small temperature region. The acoustic-phonon modes reveal a temperature-dependent nonzero energy gap in the magnetically ordered phase that falls to zero at the FOMT. The interplay between the FOMT and the phonon energy gap indicates hybridization between magnetic modes strongly affected by spin-orbit coupling and phonon modes leading to magnon-phonon quasiparticles that drive the magnetocaloric effect.
|
|
| 6. |
- Dahlqvist, Martin, et al.
(författare)
-
Magnetically driven anisotropic structural changes in the atomic laminate Mn2GaC
- 2016
-
Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- Inherently layered magnetic materials, such as magnetic M(n+1)AX(n) (MAX) phases, offer an intriguing perspective for use in spintronics applications and as ideal model systems for fundamental studies of complex magnetic phenomena. The MAX phase composition M(n+1)AX(n) consists of M(n+1)AX(n) blocks separated by atomically thin A-layers where M is a transition metal, A an A-group element, X refers to carbon and/or nitrogen, and n is typically 1, 2, or 3. Here, we show that the recently discovered magnetic Mn2GaC MAX phase displays structural changes linked to the magnetic anisotropy, and a rich magnetic phase diagram which can be manipulated through temperature and magnetic field. Using first-principles calculations and Monte Carlo simulations, an essentially one-dimensional (1D) interlayer plethora of two-dimensioanl (2D) Mn-C-Mn trilayers with robust intralayer ferromagnetic spin coupling was revealed. The complex transitions between them were observed to induce magnetically driven anisotropic structural changes. The magnetic behavior as well as structural changes dependent on the temperature and applied magnetic field are explained by the large number of low energy, i.e., close to degenerate, collinear and noncollinear spin configurations that become accessible to the system with a change in volume. These results indicate that the magnetic state can be directly controlled by an applied pressure or through the introduction of stress and show promise for the use of Mn2GaC MAX phases in future magnetoelectric and magnetocaloric applications.
|
|
| 7. |
- Ericsson, A., et al.
(författare)
-
Crystallization of a Zr-based metallic glass produced by laser powder bed fusion and suction casting
- 2021
-
Ingår i: Journal of Non-Crystalline Solids. - : Elsevier. - 0022-3093 .- 1873-4812. ; 571
-
Tidskriftsartikel (refereegranskat)abstract
- The crystallization behaviour during low temperature annealing of samples of the Zr59.3Cu28.8Al10.4Nb1.5 (at%) bulk metallic glass produced by suction casting and the laser powder bed fusion (LPBF) process were studied with small angle neutron scattering (SANS), X-ray diffraction and scanning electron microscopy. The in-situ SANS measurements during isothermal annealing reveals that the phase separation in the LPBF processed material proceeds at a smaller characteristic length-scale than the cast material. Quantitative analysis of the SANS data shows that, while the crystallization process in both materials proceed through rapid nucleation followed by diffusion limited growth, the LPBF processed material crystallizes with a smaller cluster size and at a higher rate. The smaller cluster size is attributed to the elevated oxygen content in the LPBF processed material which reduces the nucleation barrier and thus the thermal stability.
|
|
| 8. |
- Ericsson, A., et al.
(författare)
-
Transient nucleation in selective laser melting of Zr-based bulk metallic glass
- 2020
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 195
-
Tidskriftsartikel (refereegranskat)abstract
- The crystallization rate during selective laser melting (SLM) of bulk metallic glasses (BMG) is a critical factor in maintaining the material's amorphous structure. To increase the understanding of the interplay between the SLM process and the crystallization behavior of BMGs, a numerical model based on the classical nucleation theory has been developed that accounts for the rapid temperature changes associated with SLM. The model is applied to SLM of a Zr-based BMG and it is shown that the transient effects, accounted for by the model, reduce the nucleation rate by up to 15 orders of magnitude below the steady-state nucleation rate on cooling, resulting in less nuclei during the build process. The capability of the proposed modelling approach is demonstrated by comparing the resulting crystalline volume fraction to experimental findings. The agreement between model predictions and the experimental results clearly suggests that transient nucleation effects must be accounted for when considering the crystallization rate during SLM processing of BMGs.
|
|
| 9. |
- Lindwall, Johan, et al.
(författare)
-
Simulation of phase evolution in a Zr-based glass forming alloy during multiple laser remelting
- 2022
-
Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 16, s. 1165-1178
-
Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing by laser-based powder bed fusion is a promising technique for bulk metallic glass production. But, reheating by deposition of subsequent layers may cause local crystallisation of the alloy. To investigate the crystalline phase evolution during laser scanning of a Zr-based metallic glass-forming alloy, a simulation strategy based on the finite element method and the classical nucleation theory has been developed and compared with experimental results from multiple laser remelting of a single-track. Multiple laser remelting of a single-track demonstrates the crystallisation behaviour by the influence of thermal history in the reheated material. Scanning electron microscopy and transmission electron microscopy reveals the crystalline phase evolution in the heat affected zone after each laser scan. A trend can be observed where repeated remelting results in an increased crystalline volume fraction with larger crystals in the heat affected zone, both in simulation and experiment. A gradient of cluster number density and mean radius can also be predicted by the model, with good correlation to the experiments. Prediction of crystallisation, as presented in this work, can be a useful tool to aid the development of process parameters during additive manufacturing for bulk metallic glass formation.
|
|
| 10. |
- Pasquini, Luca, et al.
(författare)
-
Magnesium- and intermetallic alloys-based hydrides for energy storage : modelling, synthesis and properties
- 2022
-
Ingår i: Progress in Energy. - : Institute of Physics Publishing (IOPP). - 2516-1083. ; 4:3
-
Forskningsöversikt (refereegranskat)abstract
- Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 'Energy Storage and Conversion based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group 'Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage'. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage.
|
|
