| 1. |
- Norek, M., et al.
(författare)
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Synthesis and decomposition mechanisms of ternary Mg2COH5 studied using in situ synchrotron X-ray diffraction
- 2011
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 36:17, s. 10760-10770
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Tidskriftsartikel (refereegranskat)abstract
- A ternary Mg2COH5 hydride was synthesized using a novel method that relies on a relatively short mechanical milling time (1 h) of a 2:1 MgH2-Co powder mixture followed by sintering at a sufficiently high hydrogen pressure (>85 bar) and heating from RT to 500 degrees C. The ternary hydride forms in less than 2.5 h (including the milling time) with a yield of similar to 90% at similar to 300 degrees C. The mechanisms of formation and decomposition of ternary Mg2COH5 were studied in detail using an in situ synchrotron radiation powder X-ray diffraction (SR-PXD). The obtained experimental results are supported by morphological and microstructural investigations performed using SEM and high-resolution STEM. Additionally, thermal effects occurring during the desorption reaction were studied using DSC. The morphology of as-prepared ternary Mg2COH5 is characterized by the presence of porous particles with various shapes and sizes, which, in fact, are a type of nanocomposite consisting mainly of nanocrystallites with a size of similar to 5 nm. Mg2COH5 decomposes at approximately 300 degrees C to elemental Mg and Co. Additionally, at approximately 400 degrees C, MgCo is formed as precipitates inserted into the Mg Co matrix. During the rehydrogenation of the decomposed residues, prior to the formation of Mg2COH5, MgH2 appears, which confirms its key role in the synthesis of the ternary Mg2COH5. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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| 2. |
- Polanski, M., et al.
(författare)
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Mg2NiH4 synthesis and decomposition reactions
- 2013
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 38:10, s. 4003-4010
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Tidskriftsartikel (refereegranskat)abstract
- A ternary Mg2NiH4 hydride was synthesized using method that relies on a relatively short mechanical milling time (one hour) of a 2:1 MgH2-Ni powder mixture followed by sintering at a sufficiently high hydrogen pressure (>85 bar) and temperature (>400 degrees C). The ternary hydride forms in less than 2.5 h (including the milling time) with a yield of similar to 90% as a mixture of two polymorphic forms. The mechanisms of formation and decomposition of ternary Mg2NiH4 under different hydrogen pressures were studied in detail using an in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and high pressure DSC. The obtained experimental results are supported by morphological and microstructural investigations performed using SEM and high resolution STEM. Additionally, effects occurring during the desorption reaction were studied using DSC coupled with mass spectrometry. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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| 3. |
- Ben Amara, Heithem, 1984, et al.
(författare)
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Bone healing around biodegradable Magnesium implants: Differential response between interfacial and near-implant bone in vivo
- 2022
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Ingår i: 14th Symposium on Biodegradable Metals, Alicante, Spain 24-29 August 2022.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- INTRODUCTION: By virtue of their mechanical properties and of their degradation, magnesium (Mg)-based osteosynthesis systems are metallic implants that hold the fractured bones while eliminated in situ, thus offering the promise of reduced complications posed by permanent implants. A growing amount of research validated Mg-based implants for bone fixation by providing robust evidence in support of new bone deposition in contact with the interfacial degradation layer. Whereas Mg-degradation products are known to distribute in the implant environment, less attention has been paid to the bone response at distance from the implant interface. The present study investigated the structural, cellular, and molecular events taking place at the bone-Mg implant interface and at distance from it after in vivo implantation in an experimental rat model. METHODS: Following approval by the Local Ethical Committee at the University of Gothenburg (Dnr: 14790/2019), male Sprague-Dawley rats (n=56) were implanted with miniature screws manufactured from pure magnesium (99.99% - high purity; Mg) or from pure titanium (grade 4; Ti) (herein, serving as a control, enabling osseointegration in this model). In each animal, the metaphysis of the left and right tibiae was drilled prior to the insertion of Ti or Mg screws. After 3 and 28 days, animals were euthanized, and two types of samples were retrieved (Fig. 1): 1-Implants and peri-implant bone for quantitative polymerase chain reaction (qPCR) (n=8/group/time-point): were separately collected and allocated for molecular gene expression of the implant-adherent cells and of the cells in the peri-implant space. 2-Peri-implant bone with implants en bloc for paraffin or plastic embedding (n=6/group/time-point): enabling radiographical analyses using micro-computed tomography (micro-CT) and histomorphometrical measurements of the bone at the implant interface and at distance from it. Statistical comparisons were made between experimental groups at each time point and between time-points for each experimental group. (Kruskal-Wallis, Mann-Whitney and Wilcoxon signed-rank tests; p<0.05). RESULTS: While histological observations provided evidence of new bone formation at the vicinity of both Ti and Mg, the bone marrow at distance from the implant-interface featured morphological differences between groups (Fig. 2). At 3 days, the proportion of the interstitial and microvascular area was significantly higher at the expense of the area occupied by the hematopoietic cells in Mg- vs Ti-implanted metaphyses. At 28 days, bone marrow around Mg implants showed significantly higher adiposity in comparison to Ti implants. Yet, no differences in the trabecular bone micro-architecture were detected between biomaterials by micro-CT analysis at distance from the implant-interface. The RNA extracted from cells from the implant surface and from the peri-implant bone revealed good quality, allowing detailed molecular analysis. CONCLUSIONS: In comparison to non-degradable Ti controls, the degradation of Mg implants changes the composition of the peri-implant bone marrow, but yet without alteration of new bone formation at the implant interface. ACKNOWLEDGEMENTS: Mg rods were generously provided by the Helmholtz-Zentrum Hereon, Geesthacht, Germany. This project is part of the European Training Network within the framework of Horizon 2020 Marie Skłodowska-Curie Action No 811226.
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| 4. |
- Ben Amara, Heithem, 1984, et al.
(författare)
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Dissecting the sequential interaction between biodegradable magnesium implants and soft tissues in vivo
- 2022
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Ingår i: Materials Science and Engineering Congress, Dredsen, Germany, 27-29 September 2022.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Magnesium-based biomaterials are developed with the intention to enable tissue regeneration while being degraded under physiological conditions and eventually eliminated from the body. Once in contact with tissues, the biodegradability and the biocompatibility of magnesium implants (Mg) are governed by the direct interactions with their immediate milieu. The precise mechanisms through which the soft tissue micro-environment shapes the behaviour of Mg and the host-response remain elusive. Here, it is demonstrated that Mg degradation modulates the initial acute immune response and the subsequent fibrous encapsulation upon subcutaneous implantation in rats monitored at 1-, 3-, 6-, 14- and 28-days following surgery. In comparison to titanium implants (Ti), the initial profuse release of Mg degradation products activates pro-inflammatory pathways through increased recruitment of inflammatory cells to the soft tissue/implant interface and upregulation of pro-inflammatory genes, in parallel with a superior neo-angiogenesis and vascularization at Mg. After 6d, a shift in Mg degradation kinetics dissipates the initial pro-inflammatory response and facilitates the assembly of a comparatively thinner fibrous tissue capsule than around Ti. The reduction in the fibrous encapsulation around the Mg implant aligns with a superior expression of anti-fibrotic marker FOXO-1 at the tissue interface with Mg versus Ti. Mg induce an initial potent yet transient inflammatory response, which is associated with less adverse fibrous encapsulation after tissue healing. Tailoring Mg with controlled initial degradation appears to be crucial to enabling a successful coupling between inflammation and tissue repair during the early host response to Mg.
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| 5. |
- Ben Amara, Heithem, 1984, et al.
(författare)
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Magnesium implant degradation provides immunomodulatory and proangiogenic effects and attenuates peri-implant fibrosis in soft tissues
- 2023
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Ingår i: Bioactive Materials. - : Elsevier BV. - 2452-199X. ; 26, s. 353-369
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Tidskriftsartikel (refereegranskat)abstract
- Implants made of magnesium (Mg) are increasingly employed in patients to achieve osteosynthesis while degrading in situ. Since Mg implants and Mg2+ have been suggested to possess anti-inflammatory properties, the clinically observed soft tissue inflammation around Mg implants is enigmatic. Here, using a rat soft tissue model and a 1-28 d observation period, we determined the temporo-spatial cell distribution and behavior in relation to sequential changes of pure Mg implant surface properties and Mg2+ release. Compared to nondegradable titanium (Ti) implants, Mg degradation exacerbated initial inflammation. Release of Mg degradation products at the tissue-implant interface, culminating at 3 d, actively initiated chemotaxis and upregulated mRNA and protein immunomodulatory markers, particularly inducible nitric oxide synthase and toll-like receptor-4 up to 6 d, yet without a cytotoxic effect. Increased vascularization was demonstrated morphologically, preceded by high expression of vascular endothelial growth factor. The transition to appropriate tissue repair coincided with implant surface enrichment of Ca and P and reduced peri-implant Mg2+ concentration. Mg implants revealed a thinner fibrous encapsulation compared with Ti. The detailed understanding of the relationship between Mg material properties and the spatial and time-resolved cellular processes provides a basis for the interpretation of clinical observations and future tailoring of Mg implants.
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| 6. |
- Fortuna-Zalesna, E., et al.
(författare)
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Decommissioning of TEXTOR : properties of the Inconel liner
- 2020
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Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T171:1
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Tidskriftsartikel (refereegranskat)abstract
- The final shut-down of Tokamak Experiment for Technology Oriented Research in year 2013 created unique opportunities for multi-directional studies of in-vessel components. A set of specimens from the Inconel liner parts was collected in order to assess material properties after 26 years of exploitation. The metal surfaces were covered with up to several mu m thick co-deposits rich in boron, carbon and silicon. Detailed examination of the co-deposits and nearsurface structure of Inconel performed with Transmission Electron Microscopy (TEM) revealed: (i) stratified character of the deposits; (ii) a similar to 200 nm thick layer identified as NiSi2 phase at the interface between the deposit and Inconel substrate; (iii) changed Inconel surface layer. TEM studies of the Inconel structure revealed its polycrystalline character with a mean grain size, low dislocation density and a significant number of heterogeneously distributed primary carbides.
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| 7. |
- Fortuna-Zalesna, E., et al.
(författare)
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Dust generation and accumulation in JET-ILW : morphology and stability of co-deposits on main plasma-facing components and wall probes
- 2021
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 96:12
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Tidskriftsartikel (refereegranskat)abstract
- Dust particles and co-deposits were sampled for the first time from beryllium limiters and bulk tungsten divertor (both after ILW-3), and test mirrors from the main chamber after ILW-2 and ILW-3. The focus was on the morphology of molten particles and metal outgrowths. In parallel, the stability of beryllium layers under the impact of hot water was examined on limiters and Be coatings. The study performed by several microscopy methods including SEM, AFM, FIB, TEM and Be-sensitive EDX has revealed: (i) an asymmetric distribution of Be particles with the largest objects (125-550 mu m) on side surfaces of the Be tile: (ii) the presence of highly porous particles, resembling blisters; (iii) very few thin flakes of co-deposits on the divertor, on the shadowed edge of lamella; (iv) the elemental composition and internal structure of the needle-shaped outgrowths on the mirrors: MoO; (v) no detectable impact of water on the beryllium morphology.
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| 8. |
- Rubel, Marek, et al.
(författare)
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Metallic mirrors for plasma diagnosis in current and future reactors : tests for ITER and DEMO
- 2017
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Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T170
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Tidskriftsartikel (refereegranskat)abstract
- Optical spectroscopy and imaging diagnostics in next-step fusion devices will rely on metallic mirrors. The performance of mirrors is studied in present-day tokamaks and in laboratory systems. This work deals with comprehensive tests of mirrors: (a) exposed in JET with the ITER-like wall (JET-ILW); (b) irradiated by hydrogen, helium and heavy ions to simulate transmutation effects and damage which may be induced by neutrons under reactor conditions. The emphasis has been on surface modification: deposited layers on JET mirrors from the divertor and on near-surface damage in ion-irradiated targets. Analyses performed with ion beams, microscopy and spectro-photometry techniques have revealed: (i) the formation of multiple co-deposited layers; (ii) flaking-off of the layers already in the tokamak, despite the small thickness (130-200 nm) of the granular deposits; (iii) deposition of dust particles (0.2-5 mu m, 300-400 mm(-2)) composed mainly of tungsten and nickel; (iv) that the stepwise irradiation of up to 30 dpa by heavy ions (Mo, Zr or Nb) caused only small changes in the optical performance, in some cases even improving reflectivity due to the removal of the surface oxide layer; (v) significant reflectivity degradation related to bubble formation caused by the irradiation with He and H ions.
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