| 1. |
- Corbett, Thomas, et al.
(författare)
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Organic carbon source controlled microbial olivine dissolution in small-scale flow-through bioreactors, for CO2 removal
- 2024
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Ingår i: NPJ MATERIALS DEGRADATION. - : Nature Publishing Group. - 2397-2106. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The development of carbon dioxide removal methods, coupled with decreased CO2 emissions, is fundamental to achieving the targets outlined in the Paris Agreement limiting global warming to 1.5 degrees C. Here we are investigating the importance of the organic carbon feedstock to support silicate mineral weathering in small-scale flow through bioreactors and subsequent CO2 sequestration. Here, we combine two bacteria and two fungi, widely reported for their weathering potential, in simple flow through bioreactors (columns) consisting of forsterite and widely available, cheap organic carbon sources (wheat straw, bio-waste digestate of pig manure and biowaste, and manure compost), over six weeks. Compared to their corresponding abiotic controls, the inoculated straw and digestate columns release more total alkalinity (similar to 2 times more) and produce greater dissolved and solid inorganic carbon (29% for straw and 13% for digestate), suggesting an increase in CO2 sequestration because of bio-enhanced silicate weathering. Microbial biomass is higher in the straw columns compared to the digestate and manure compost columns, with a phospholipid fatty acid derived total microbial biomass 10 x greater than the other biotic columns. Scanning Electron Microscopy imaging shows the most extensive colonisation and biofilm formation on the mineral surfaces in the straw columns. The biotic straw and digestate columns sequester 50 and 14 mg C more than their abiotic controls respectively, while there is no difference in the manure columns. The selection of organic carbon sources to support microbial communities in the flow through bioreactors controlls the silicate weathering rates and CO2 sequestration.
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| 2. |
- Esmaily, Mohsen, et al.
(författare)
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High-temperature oxidation behaviour of AlxFeCrCoNi and AlTiVCr compositionally complex alloys
- 2020
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Ingår i: npj Materials Degradation. - : Springer Science and Business Media LLC. - 2397-2106. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Compositionally complex alloys (CCAs), also termed as high entropy alloys (HEAs) or multi-principal element alloys (MPEAs), are being considered as a potential solution for many energy-related applications comprising extreme environments and temperatures. Herein, a review of the pertinent literature is performed in conjunction with original works characterising the oxidation behaviour of two diverse Al-containing alloys; namely a lightweight (5.06 g/cm(3)) single-phase AlTiVCr CCA and a multiple-phase Al0.9FeCrCoNi CCA (6.9 g/cm(3)). The thermogravimetric results obtained during oxidation of the alloys at 700 and 900 degrees C revealed that both alloys tended to obey the desired parabolic rate law. Post-exposure analysis by means of electron microscopy indicated that while the oxide scale formed on the AlTiVCr is adherent to the substrate, the scale developed on the Al0.9FeCrCoNi displays a notable spalling propensity. This study highlights the need for tailoring the protective properties of the oxide scale formed on the surface of the CCAs.
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| 3. |
- Gout, Thomas L., et al.
(författare)
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Diffusive processes in aqueous glass dissolution
- 2019
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Ingår i: npj Materials Degradation. - : Springer Science and Business Media LLC. - 2397-2106. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- High level nuclear waste is often immobilised in a borosilicate glass for disposal. However, this glass corrodes in contact with aqueous solutions. To predict radionuclide releases from wasteforms, their dissolution mechanisms must be understood. Understanding glass dissolution mechanisms presents a challenge across numerous other disciplines and many glass dissolution models still remain conflicted. Here we show that diffusion was a significant process during the later stages of dissolution of a simplified waste glass but was not evidenced during the initial stages of dissolution. The absence of measurable isotopic fractionation in solution initially supports models of congruent dissolution. However, the solution becoming isotopically lighter at later times evidences diffusive isotopic fractionation and opposes models that exclude diffusive transport as a significant mechanism. The periodically sampled isotopic methodologies outlined here provide an additional dimension with which to understand glass dissolution mechanisms beyond the usual measurement of solution concentrations and, post-process, nano-scale analysis of the altered glass.
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| 4. |
- Hedberg, Yolanda, Docent, 1985-
(författare)
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Role of proteins in the degradation of relatively inert alloys in the human body
- 2018
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Ingår i: NPJ MATERIALS DEGRADATION. - : Springer Nature. - 2397-2106. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Many biomedical materials used today for applications such as orthopedic, dental, and cardiovascular implants and devices are made of corrosion-resistant, 'inert', metallic materials of the cobalt-chromium, titanium, and stainless steel alloy groups. This perspective focuses on the role of proteins in the degradation of these materials in a human body environment. After adsorption, the proteins interact relatively slowly with the metal and metal surface oxide. A number of factors, including the individual body chemistry (especially the presence of inflammatory cells producing oxidative species), determine whether the proteins can bind to metals in the surface oxide and whether the metal-protein conjugates can detach from the surface. Metals in the forms of protein-bound metal ions or nanosized particles can also increase protein-protein interactions and aggregation, which can cause some health effects and change the material degradation mechanism. While proteins in some short-term studies (<6 h) even decrease material degradation due to shielding effects and better lubrication, they may increase degradation after longer time periods due to relatively slow binding, detachment, and combined corrosion processes. In-vitro material degradation studies of relatively corrosion-resistant alloys for biomedical applications should therefore include long-term studies, complexing agents or proteins, and realistic oxidative environments simulating inflammatory conditions.
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| 5. |
- Larsson, Alfred, et al.
(författare)
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Dynamics of early-stage oxide formation on a Ni-Cr-Mo alloy
- 2024
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Ingår i: NPJ MATERIALS DEGRADATION. - : Springer Nature. - 2397-2106. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion results in large costs and environmental impact but can be controlled by thin oxide films that passivate the metal surfaces and hinder further oxidation or dissolution in an aqueous environment. The structure, chemistry, and thickness of these oxide films play a significant role in determining their anti-corrosion properties and the early-stage oxidation dynamics affect the properties of the developed oxide. Here, we use in situ X-ray Photoelectron Spectroscopy (XPS) to study the early-stage oxidation of a Ni-Cr-Mo alloy at room temperature and up to 400 degrees C. Cr and Mo begin to oxidize immediately after exposure to O2, and Cr3+, Mo4+, and Mo6+ oxides are formed. In contrast, Ni does not contribute significantly to the oxide film. A self-limiting oxide thickness, which did not depend on temperature below 400 degrees C, is observed. This is attributed to the consumption of available Cr and Mo near the surface, which results in an enrichment of metallic Ni under the oxide. The self-limited oxide thickness is 6-8 angstrom, which corresponds to 3-4 atomic layers of cations in the oxide. At 400 degrees C, sublimation of Mo6+ oxide is observed, resulting in the formation of an almost pure layer of Cr2O3 on the alloy surface. Lastly, a mechanism is presented that explains the formation of the bi-layer oxide structure observed for Ni-Cr-Mo alloys, which involves the enhanced migration of hexavalent Mo ions in the electric field, which drives mass transport during oxidation according to both the Cabrera Mott model and the Point Defect Model.
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| 6. |
- Li, Wenchao, et al.
(författare)
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Numerical simulation of carbon steel atmospheric corrosion under varying electrolyte-film thickness and corrosion product porosity
- 2023
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Ingår i: NPJ MATERIALS DEGRADATION. - : Springer Nature. - 2397-2106. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- A finite element model is developed to study dynamics of atmospheric corrosion of carbon steel, focusing on the influence of thin electrolyte film thickness under varying corrosion product porosity. Calculations have been done to evaluate the impact of electrolyte film thickness and corrosion product porosity on oxygen diffusion path, and the hindrance effect of corrosion products on the metal surface activity. The time evolution of corrosion current density and controlling steps in the corrosion process are explored. When the corrosion products are loose, oxygen diffusion is the dominant controlling step, and the thicker the electrolyte film, the lower the corrosion rate. When they are dense, the corrosion process is controlled by the mixture of oxygen diffusion and the surface discharge. The oxygen diffusion path is determined only by the corrosion product porosity, and therefore the corrosion rate is not affected by the electrolyte film thickness.
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| 7. |
- Linder, Clara, et al.
(författare)
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Corrosion resistance of additively manufactured aluminium alloys for marine applications
- 2024
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Ingår i: npj Materials Degradation. - : Springer. - 2397-2106. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing opens new possibilities for designing light-weight structures using aluminium alloys. The microstructure of two Al alloys and their corrosion resistance in NaCl and natural seawater environments were investigated. The newly designed Al-Mn-Cr-Zr based alloy showed a higher corrosion resistance than reference AlSi10Mg alloy in both environments in as printed and heat-treated conditions. The corrosion initiated in the Al matrix along the precipitates in the alloys where the Volta potential difference was found the highest. The coarser microstructure and precipitate composition of the new Al-alloy led to the formation of a resistant passive film which extended the passivity region of the Al-Mn-Cr-Zr alloy compared to the AlSi10Mg alloy. The effect of heat treatment could be seen in the microstructure as more precipitates were found in between the melt pool boundaries, which affected the corrosion initiation and slightly the pitting resistance. Overall, this study shows that a newly designed Al-alloy for additive manufacturing has a suitable corrosion resistance for applications in marine environments.
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| 8. |
- Långberg, Marie, 1988-, et al.
(författare)
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Redefining passivity breakdown of super duplex stainless steel by electrochemical operando synchrotron near surface X-ray analyses
- 2019
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Ingår i: npj Materials Degradation. - Stockholm, : Springer Science and Business Media LLC. - 2397-2106. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Passivity determines corrosion resistance and stability of highly-alloyed stainless steels, and passivity breakdown is commonly believed to occur at a fixed potential due to formation and dissolution of Cr(VI) species. In this work, the study of a 25Cr–7Ni super duplex stainless steel in 1 M NaCl solution revealed that the passivity breakdown is a continuous degradation progress of the passive film over a potential range, associated with enhanced Fe dissolution before rapid Cr dissolution and removal of the oxide. The breakdown involves structural and compositional changes of the passive film and the underlying alloy surface layer, as well as selective metal dissolution depending on the anodic potential. The onset of passivity breakdown occurred at 1000 mV/Ag/AgCl, and Fe dissolved more on the ferrite than the austenite phase. With increasing potential, the passive film became thicker but less dense, while the underlying alloy surface layer became denser indicating Ni and Mo enrichment. Rapid Cr dissolution occurred at ≥1300 mV/Ag/AgCl.
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| 9. |
- Nava-Farias, Lorena, et al.
(författare)
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Applying laboratory methods for durability assessment of vitrified material to archaeological samples
- 2021
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Ingår i: npj Materials Degradation. - : Springer Nature. - 2397-2106. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory testing used to assess the long-term chemical durability of nuclear waste forms may not be applicable to disposal because the accelerated conditions may not represent disposal conditions. To address this, we examine the corrosion of vitrified archeological materials excavated from the near surface of a ~1500-year old Iron Age Swedish hillfort, Broborg, as an analog for the disposal of vitrified nuclear waste. We compare characterized site samples with corrosion characteristics generated by standard laboratory durability test methods including the product consistency test (PCT), the vapor hydration test (VHT), and the EPA Method 1313 test. Results show that the surficial layer of the Broborg samples resulting from VHT displays some similarities to the morphology of the surficial layer formed over longer timescales in the environment. This work provides improved understanding of long-term glass corrosion behavior in terms of the thickness, morphology, and chemistry of the surficial features that are formed.
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| 10. |
- Pakharenko, Viktoriya, et al.
(författare)
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Chemical and molecular structure transformations in atomistic conformation of cellulose nanofibers under thermal environment
- 2022
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Ingår i: npj Materials Degradation. - : Springer Nature. - 2397-2106. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The structural changes of the glucopyranose chain and the chemical compositional response of cellulose nanofibers (CNFs) under thermal exposure (at 190 °C for 5 h) have remained a significant gap in the understanding of the long-term performance of nanocellulose. Herein, CNF films with different chemical compositions were investigated to confirm the structural transformation of glucopyranose (coupling constant of OH groups changed up to 50%) by nuclear magnetic resonance (NMR) analysis. Remarkably, the glucopyranose rings underwent partial dehydration during the thermal exposure resulting in enol formation. This study confirms the chain mobility that could lead to the conformational and dimensional changes of the CNFs during thermal exposure. The broad range of conformations was defined by the dihedral angles that varied from ±27° to ±139° after thermal exposure. Investigation into the mechanism involving chemical transformation of the substrates during heating is important for the fabrication of the next generation of flexible electrical materials.
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