| 1. |
- Sugiyama, Jun, et al.
(författare)
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Negative muon spin rotation and relaxation on superconducting MgB 2
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Konferensbidrag (refereegranskat)abstract
- The internal nuclear magnetic field in a superconducting MgB2 powder sample was studied with a μ- SR technique. Although the past μ +SR study on MgB2 reported the appearance of a dynamic behavior even below Tc due to μ + diffusion, μ- SR shows a static behavior in the whole temperature range measured, as expected. The ZF-μ- SR spectra do not suggest any appearance of additional magnetic field below Tc within the experimental accuracy. Considering the small asymmetry of the μ- SR signal, it is a challenge to detect the appearance of an internal magnetic field below Tc caused by the time reversal symmetry breaking.
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| 2. |
- Forslund, Ola Kenji, et al.
(författare)
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Magnetic phase diagram of K 2 Cr 8 O 16 clarified by high-pressure muon spin spectroscopy
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- The K 2 Cr 8 O 16 compound belongs to a series of quasi-1D compounds with intriguing magnetic properties that are stabilized through a high-pressure synthesis technique. In this study, a muon spin rotation, relaxation and resonance (μ + SR) technique is used to investigate the pressure dependent magnetic properties up to 25 kbar. μ + SR allows for measurements in true zero applied field and hereby access the true intrinsic material properties. As a result, a refined temperature/pressure phase diagram is presented revealing a novel low temperature/high pressure (p C1 = 21 kbar) transition from a ferromagnetic insulating to a high-pressure antiferromagnetic insulator. Finally, the current study also indicates the possible presence of a quantum critical point at p C2 ~ 33 kbar where the magnetic order in K 2 Cr 8 O 16 is expected to be fully suppressed even at T = 0 K.
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| 3. |
- Miniotaite, Ugne, et al.
(författare)
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Magnetic Properties of Multifunctional 7 LiFePO 4 under Hydrostatic Pressure
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Konferensbidrag (refereegranskat)abstract
- LiFePO4 (LFPO) is an archetypical and well-known cathode material for rechargeable Li-ion batteries. However, its quasi-one-dimensional (Q1D) structure along with the Fe ions, LFPO also displays interesting low-temperature magnetic properties. Our team has previously utilized the muon spin rotation (μ +SR) technique to investigate both magnetic spin order as well as Li-ion diffusion in LFPO. In this initial study we extend our investigation and make use of high-pressure μ +SR to investigate effects on the low-T magnetic order. Contrary to theoretical predictions we find that the magnetic ordering temperature as well as the ordered magnetic moment increase at high pressure (compressive strain).
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| 4. |
- Miniotaite, Ugne, et al.
(författare)
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Magnetic Properties of Multifunctional (LiFePO4)-Li-7 under Hydrostatic Pressure
- 2023
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Ingår i: Proceedings 15th International Conference on Muon Spin Rotation, Relaxation and Resonance (SR). - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- LiFePO4 (LFPO) is an archetypical and well-known cathode material for rechargeable Li-ion batteries. However, its quasi-one-dimensional (Q1D) structure along with the Fe ions, LFPO also displays interesting low-temperature magnetic properties. Our team has previously utilized the muon spin rotation (mu+SR) technique to investigate both magnetic spin order as well as Li-ion diffusion in LFPO. In this initial study we extend our investigation and make use of high-pressure mu+SR to investigate effects on the low-T magnetic order. Contrary to theoretical predictions we find that the magnetic ordering temperature as well as the ordered magnetic moment increase at high pressure (compressive strain).
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| 5. |
- Palm, Rasmus, et al.
(författare)
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In situ neutron diffraction of NaAlD4/carbon black composites during decomposition/deuteration cycles and the effect of carbon on phase segregation
- 2022
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 47:80, s. 34195-34204
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Tidskriftsartikel (refereegranskat)abstract
- The influence on the decomposition and reforming of the hydrogen storage material NaAlH4 by adding relatively low amounts of mesoporous carbon black is investigated with in situ diffraction. A 60:40 NaAlH4/carbon black composite is prepared via ball milling and characterised ex situ via X-ray diffraction, gas adsorption, temperature-programmed decomposition, and dehydrogenation/hydrogenation cycling methods. The prepared composite is deuterated, and the crystalline phase composition is determined with in situ neutron powder diffraction method during multiple decomposition/deuteration cycles. Changes in the crystalline phase composition start slightly below the melting temperature of the pristine alanate, whereas the release of deuterium starts at considerably lower temperatures. The decomposition of Na3AlD6 to NaD is almost completely reversible at the applied low deuterium pressures of >= 2 MPa. Thus, the strong effect of even low concen-trations of a mesoporous carbon black on the capability to store H2 reversibly is showcased and analysed in-depth.
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| 6. |
- Sugiyama, J., et al.
(författare)
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Desorption reaction in MgH 2 studied with in situ μ + SR
- 2019
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Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry. - 2398-4902. ; 3:4, s. 956-964
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Tidskriftsartikel (refereegranskat)abstract
- In order to study the mechanism determining the desorption temperature (T d ) of hydrogen storage materials, we have measured positive muon spin rotation and relaxation (μ + SR) in MgH 2 over a wide temperature range including its T d . The pressure in the sample cell due to desorbed H 2 was measured in parallel with the μ + SR measurements under static conditions. Such in situ μ + SR measurements revealed that hydrogen starts to diffuse in MgH 2 well below T d . This indicates the important role of hydrogen diffusion in accelerating the desorption reaction by removing the reaction product, i.e. H 2 , from the reaction system.
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| 7. |
- Sugiyama, Jun, et al.
(författare)
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Lithium diffusion in LiMnPO4 detected with mu +/- SR
- 2020
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Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- Positive- and negative-muon spin rotation and relaxation (mu(+/-) SR) was first used to investigate fluctuations of nuclear magnetic fields in an olivine-type battery material, LiMnPO4, in order to clarify the diffusive species, namely, to distinguish between a mu(+) hopping among interstitial sites and Li+ ions diffusing in the LiMnPO4 lattice. Muon diffusion can only occur in mu+SR, because the implanted mu(-) forms a stable muonic atom at the lattice site, and therefore any change in linewidth measured with mu-SR must be due to Li+ diffusion. Since the two measurements exhibit a similar increase in the field fluctuation rate with temperature above 100 K, it is confirmed that Li+ ions are in fact diffusing. The diffusion coefficient of Li+ at 300 K and its activation energy were estimated to be 1.4(3) x 10(-10) cm(2)/s and 0.19(3) eV, respectively. Such combined mu(SR)-S-+/- measurements are thus shown to be a suitable tool for detecting ion diffusion in solid-state energy materials.
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| 8. |
- Sugiyama, Jun, et al.
(författare)
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Magnetic phase boundary of BaVS3 clarified with high-pressure mu+SR
- 2020
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9969 .- 2469-9950. ; 101:17
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic nature of the quasi-one-dimensional BaVS3 has been studied as a function of temperature down to 0.25 K and pressure up to 1.97 GPa on a powder sample using the positive muon spin rotation and relaxation (mu(+) SR) technique. At ambient pressure, BaVS3 enters an incommensurate antiferromagnetic ordered state below the Neel temperature (T-N)31 K. T-N is almost constant as the pressure (p) increases from ambient pressure to 1.4 GPa, then T-N decreases rapidly for p > 1.4 GPa, and finally disappears at p similar to 1.8 GPa, above which a metallic phase is stabilized. Hence, T-N is found to be equivalent to the pressure-induced metal-insulator transition temperature (T-MI) at p > 1.4 GPa.
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| 9. |
- Thomsen, Benjamin, et al.
(författare)
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Component Lifing Decisions and Maintenance Strategies in the Context of Aeroengine Product-Service Systems Design
- 2015
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Ingår i: Paper No DETC2015-46967, In Proceedings from ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, ASME, Boston, Massachusetts, USA, August 2–5, 2015. - 9780791857083 ; Volume 2B: 41st Design Automation Conference, s. pp. V02BT03A045-
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Konferensbidrag (refereegranskat)abstract
- Static structural engine components are typically designed for full lifetime operation. Efforts to reduce weight in order to improve performance result in structural designs associated with higher lifing uncertainty: Maintaining reliability levels may necessitate expensive manufacturing and maintenance solutions. In practice, repair techniques for such structures are available; however, they are not planned for during the design process. The objective of the research presented in this paper is to model and optimize component lifecycle costs with respect to lifing decisions, demonstrated by means of an aeroengine component design example. Both technical (failure) and legislative (certification) implications are considered. The impact of maintenance strategies (repair and/or replace) on lifing design decisions is quantified. It is shown that, under different conditions, it may not be prudent to design for full life but rather accept shorter life and then repair or replace the component. This is especially evident if volumetric effects on low cycle fatigue life are taken into account. It is possible that failure rates based on legacy engines do not translate necessarily to weight-optimized components. Such an analysis can play a significant supporting role in engine component design in a product-service system context.
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| 10. |
- Thomsen, Benjamin, et al.
(författare)
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Quantitative Assessment of the Impact of Alternative Manufacturing Methods on Aeroengine Component Lifing Decisions
- 2017
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Ingår i: Journal of Mechanical Design - Transactions of the ASME. - : ASME International. - 1050-0472. ; 139:2
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Tidskriftsartikel (refereegranskat)abstract
- Static structural aeroengine components are typically designed for full lifetime operation. Under this assumption, efforts to reduce weight in order to improve performance result in structural designs that necessitate expensive manufacturing solutions to ensure high reliability. However, there exist repair techniques that enable the consideration of alternative manufacturing and/or maintenance strategies, in which case different component lifing decisions may be preferable. The research presented in this paper proposes a value-maximizing design framework that models and optimizes component lifing decisions in an aeroengine product-service system context by considering manufacturing and maintenance alternatives. To that end, a lifecycle cost model is developed as a proxy of value creation. Component lifing decisions are made to minimize net present value of lifecycle costs. The impact of manufacturing (represented by associated intial defects) and maintenance strategies (repair and/or replace) on lifing design decisions is quantified by means of failure models whose output is an input to the lifecycle cost model. It is shown that, under different conditions, it may not be prudent to design for full life but rather accept shorter life and then repair or replace the component. This is especially evident if volumetric effects on low cycle fatigue life are taken into account. It is possible that failure rates based on legacy engines do not translate necessarily to weight-optimized components. Such an analysis can play a significant supporting role in engine component design in a product-service system context.
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