| 1. |
- Engkvist, Josefin, 1972, et al.
(författare)
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The initial effect of KCl deposit on alumina scales characterized by ToF-SIMS and AES
- 2013
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Ingår i: Surface and Interface Analysis. - : Wiley. - 1096-9918 .- 0142-2421. ; 45:1, s. 445-448
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Tidskriftsartikel (refereegranskat)abstract
- A FeCrAl alloy was preoxidized to form a protective alumina scale, and the effect of KCl deposits on the alumina scale was investigated while exposed during 1 and 24 h at 600 degrees C. However, impurity concentrations in the alumina scale change the ion conductivity and hence affect its protective properties. Therefore, Auger electron spectroscopy and time-of-flight secondary ion mass spectrometry were used to characterize the alumina scales and detect traces of K and Cl. The results showed that K and Cl existed as large sharp-edged crystals surrounded by a dendritic network after 1 h. However, after 24 h, those were dissolved, and K together with Cl was detected only in the outer layer of the duplex alumina scale, which was formed during preoxidation.
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| 2. |
- Hagman, Henrik, 1980-
(författare)
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Co-firing animal waste, sludge, residue wood, peat and forest fuels in a 50MWth CFB boiler : ash transformation, availability and process improvements
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The direct variable costs for heat and electricity production based on solid biomass fuel combustion is approximately 3-5 times lower than the costs in a fossil fuel-oil based boiler in Sweden. In addition waste derived biomass fuels are typically much cheaper than biomass not classified as waste. The introduction of the waste derived fuels; wastewater treatment sludge, demolition wood, and animal waste in a 50MWth circulating fluidized bed (CFB) biomass boiler located in Perstorp, Sweden, led to rapid deposit buildup in superheaters, heavy ash accumulation in economizers and failing boiler tubes and vortex finders that forced frequent boiler shutdowns. This in turn increased the use of expensive oil (fossil fuel) in backup boilers and the CO2 footprint of the on-site energy conversion system. This work aims to increase the general mechanistic understanding of combustion systems using complex fuels, and includes: A mapping of the boiler failure and preventive maintenance statistics; elemental composition analysis of ash, deposits and fuel fractions; flue-gas composition measurements; chemical speciation analysis; an attempt to describe the overall ash transformation reactions and mass balance throughout the combustion process. Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) was used to analyze the elemental composition of ash and deposits. The SEM-EDS results were used together with data from X-ray powder diffraction (XRD) analysis, thermodynamic phase data, and equilibrium calculations in an attempt to quantify the crystalline phases and the overall ash transformation of the process. Based on the findings concerning ash transformation and the failure statistics, it has been possible to identify generic key parameters regarding boiler design and process parameters, enabling major improvements of the CFB boiler availability, a lower overall energy conversion cost and a reduced CO2 footprint.
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| 3. |
- Clayton, Clive R., et al.
(författare)
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Passivity of austenitic stainless steels
- 2011
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Ingår i: Corrosion Mechanisms in Theory and Practice: Third Edition. - 9781420094633 ; , s. 327-348
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Austenitic stainless steels appear to have signiŽcantly greater potential for aqueous corrosion resistance than their ferritic counterparts. This is because the three most commonly used austenite stabilizers, Ni, Mn, and N, all contribute to passivity. As in the case of ferritic stainless steel, Mo, one of the most potent alloying additions for improving corrosion resistance, can also be added to austenitic stainless steels in order to improve the stability of the passive Žlm, especially in the presence of Cl ions. The passive Žlm formed on austenitic stainless steels is often reported to be duplex, consisting of an inner barrier oxide Žlm and outer deposit hydroxide or salt Žlm.
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| 4. |
- Lindgren, Mikaela, 1987, et al.
(författare)
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Confinement dependence of electro-catalysts for hydrogen evolution from water splitting
- 2014
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Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein Institut. - 2190-4286. ; 5:1, s. 195-201
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory is utilized to articulate a particular generic deconstruction of the electrode/electro-catalyst assembly for the cathode process during water splitting. A computational model was designed to determine how alloying elements control the fraction of H2 released during zirconium oxidation by water relative to the amount of hydrogen picked up by the corroding alloy. This model is utilized to determine the efficiencies of transition metals decorated with hydroxide interfaces in facilitating the electro-catalytic hydrogen evolution reaction. A computational strategy is developed to select an electro-catalyst for hydrogen evolution (HE), where the choice of a transition metal catalyst is guided by the confining environment. The latter may be recast into a nominal pressure experienced by the evolving H2 molecule. We arrived at a novel perspective on the uniqueness of oxide supported atomic Pt as a HE catalyst under ambient conditions.
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| 5. |
- Lindgren, Mikaela, 1987, et al.
(författare)
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Impact of Additives on Zirconium Oxidation by Water: Mechanistic insights from first principles
- 2013
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Ingår i: RSC Advances. - 2046-2069. ; 3:44, s. 21613-21619
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Tidskriftsartikel (refereegranskat)abstract
- Zirconium alloys are widely used as cladding materials employed to contain the fission fuel in nuclear power plants. A limiting factor for fuel longevity is the corrosion property of the zirconium alloys. In the reactor, the main corrodent is water. The oxide forms thermodynamically during hydrogen evolution. Due to the corrosion mechanism, a fraction of the hydrogen is transferred to the alloy. It has long been known that the alloying elements actually control the hydrogen pick-up fraction, HPUF. A mechanism that explains these observations by means of density functional theory calculations is presented and validated. A hydroxylated grain boundary model decorated by various transition metal, TM, ions is employed to study the dependence of the hydrogen evolution reaction, HER, on the choice of TM ion and spin state along the hydride-proton recombination pathway. The efficiency of the system to utilize the overpotential for hydrogen evolution, originating from the overall corrosivity of the alloy, is found to be decisive for the HPUF. A dual origin of the detrimental effects of Co and Ni additives on the HPUF is identified.
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| 6. |
- Lindgren, Mikaela, 1987, et al.
(författare)
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On the fate of hydrogen during zirconium oxidation by water: Effect of oxygen dissolution in α-Zr
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:22, s. 11050-11058
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Tidskriftsartikel (refereegranskat)abstract
- Zirconium oxidation by water is accompanied by hydrogen conversion, either H2 is released or hydrogen is picked up by the alloy. Strategies are sought to mitigate the detrimental hydrogen uptake into the metal. The corrosion phenomenon is subdivided into anode and cathode processes caused by electron release upon O2- oxidation at the metal/oxide interface in case of the former and electron-proton recombination resulting in hydrogen pick-up or H2 evolution in case of the latter. In a previous study, the additive dependence of the cathodic hydrogen evolution reaction was analysed. The present study contributes the oxygen concentration dependence of the anode potential, presents the impact of oxygen concentration on the co-absorption of hydrogen and merges the anode and cathode processes. The computational model is validated by semi-quantitatively reproducing the experimental solubility limit for oxygen in α-Zr. The impact of the emerging conceptual understanding for material development is discussed.
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| 7. |
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| 8. |
- Hultquist, Gunnar, et al.
(författare)
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Corrosion of copper in distilled water without molecular oxygen and the detection of produced hydrogen
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper reports on hydrogen pressures measured during the longterm immersion (~19 000 hours) of copper in oxygen-free distilled water. Hydrogen gas evolution is from copper corrosion and similar pressures (in the mbar range) are measured for copper contained in either a 316 stainless steel or titanium system. Copper corrosion products have been examined ex-situ by SEM and characterized by Xray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS strongly indicates a corrosion product containing both hydroxide and oxide. SIMS shows that oxygen is mainly present in the outer 0.3 um surface region and that hydrogen penetrates to depths in the substrate well below the corrosion product.
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| 9. |
- Oudbashi, Omid, 1978, et al.
(författare)
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A note on the corrosion morphology of some middle elamite copper alloy artefacts from haft tappeh, South-West Iran
- 2010
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Ingår i: Studies in Conservation. - : Informa UK Limited. - 0039-3630 .- 2047-0584. ; 55, s. 20-25
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Tidskriftsartikel (refereegranskat)abstract
- The paper reviews the corrosion morphology of some copper-based alloy objects from the Middle Elamite site of Haft Tappeh, south-west Iarn about 1400 BC. These artefacts have undergone extensive bronze disease corrosion and their interior is completely converted to a greyish-white, tin-rich phase, with corresponding loss of copper.
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| 10. |
- Oudbashi, Omid, 1978, et al.
(författare)
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Micro-stratigraphical investigation on corrosion layers in ancient Bronze artefacts by scanning electron microscopy energy dispersive spectrometry and optical microscopy
- 2013
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Ingår i: Heritage Science. - : Springer Science and Business Media LLC. - 2050-7445. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Archaeological metallic artefacts buried in soils deteriorate by means of various environmental as well as internal factors and mechanisms over time such as change in composition and microstructure of metal and corrosive factors due to long-term burial environment. Corrosion in metals occurs in different morphologies and results in different types of corrosion products based on soil composition. Identification of corrosion mechanisms and morphology in archaeological metals can help conservators to characterize deterioration occurred in metals and make decisions to protect artefacts about preventing further deterioration. In archaeological bronzes, different layers may form on the surface of artefacts and their composition, depth and shape depends on factors noted above.Results: In this paper, results of investigation carried out on ancient bronzes discovered from Haft Tappeh archaeological site, southwestern Iran, are presented. The ancient bronze samples are dated to the Middle Elamite period about 14th century BC. Some of the Haft Tappeh bronze artefacts corroded completely and a multilayer structure has formed. To study the stratigraphy of corrosion layers and their composition, some bronze artefacts have been analyzed using SEM-EDS (Scanning Electron Microscopy Energy Dispersive Spectrometry) and Optical Microscopy analyses. The results show difference between the amount of Cu and Sn in layers that may follow from copper leaching from inner layers and formation of copper trihydroxychlorides because of bronze disease.Conclusions: Based on the results, it can be concluded that SEM-EDS analysis and Microscopy observations can help to characterize compositional difference between corrosion layers in the micro scale as well as corrosion mechanisms occurring in archaeological metal artefacts. © 2013 Oudbashi et al.; licensee Chemistry Central Ltd.
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