| 1. |
- Saldan, Ivan, et al.
(författare)
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Surface analysis of nickel nanomaterials electrodeposited on graphite surface
- 2019
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Ingår i: Micro & Nano Letters. - : INST ENGINEERING TECHNOLOGY-IET. - 1750-0443. ; 14:12, s. 1233-1237
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Tidskriftsartikel (refereegranskat)abstract
- Pure Nickel (Ni) and Nickel-Palladium (Ni-Pd) alloy were electrodeposited on graphite surface via pulse electrolysis in dimethyl sulfoxide in form of rods and nanoparticles with a diameter of similar to 100-350 and similar to 10-35 nm, respectively. X-ray photoelectron spectroscopy (XPS) spectra of Ni 2p(3/2) region for these nanomaterials suggests on their surface Ni2+ precursor while after Ar+ ion-etching metallic nickel starts to be dominated. Both Pd-0 and Pd2+ for XPS spectra of Pd 3d(5/2) and 3d(3/2) were observed after electrodeposition. Scanning electron microscope-energy dispersive X-ray and XPS analysis confirmed electrodeposition of nickel nanomaterials in non-aqueous electrolyte. Using a lower concentration of Ni2+ precursor, nanoparticles with an average particle size of similar to 10-23 nm were prepared on a graphite surface.
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| 2. |
- Guo, K., et al.
(författare)
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Size-Dependent Catalytic Activity of Monodispersed Nickel Nanoparticles for the Hydrolytic Dehydrogenation of Ammonia Borane
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 10:1, s. 517-525
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Tidskriftsartikel (refereegranskat)abstract
- Nickel (Ni) nanoparticles (NPs) with controlled sizes in the range of 4.9-27.4 nm are synthesized by tuning the ratio of the nickel acetylacetonate precursor and trioctylphosphine in the presence of oleylamine. X-ray diffraction and transmission electron microscopy confirm the formation of the metallic Ni crystal phase and their monodispersed nature. These Ni NPs are found to be effective catalysts for the hydrolytic dehydrogenation of ammonia borane, and their catalytic activities are size-dependent. A volcano-type activity trend is observed with 8.9 nm Ni NPs presenting the best catalytic performance. The activation energy and turnover frequency (TOF) of the 8.9 nm NP catalyst are further calculated to be 66.6 kJ·mol-1 and 154.2 molH2·molNi -1·h-1, respectively. Characterization of the spent catalysts indicates that smaller-sized NPs face severe agglomeration, resulting in poor stability and activity. Three carbon support materials are thus used to disperse and stabilize the Ni NPs. It shows that 8.9 nm Ni NPs supported on Ketjenblack (KB) exhibit higher activity than that supported on carbon nanotubes and graphene nanoplatelets. The agglomeration-induced activity loss is further illustrated by immobilizing 4.9 nm Ni NPs onto KB, which exhibits significantly enhanced activity with a high TOF of 447.9 molH2·molNi -1·h-1 as well as an excellent reusability in the consecutive dehydrogenation of ammonia borane. The high catalytic performance can be attributed to the intrinsic activity of nanoparticulate Ni and the improved activity and stability due to the strong Ni/KB metal-support interactions.
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| 3. |
- Stjärnsäter, Johan, et al.
(författare)
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Effect of dissolved hydrogen on the crack growth rate and oxide film formation at the crack tip of alloy 600 exposed to simulated pwr primary water
- 2018
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Ingår i: Part of the The Minerals, Metals & Materials Series book series (MMMS). - 9783319672434 ; , s. 423-437
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Konferensbidrag (refereegranskat)abstract
- The effect of dissolved hydrogen (DH) on primary water stress corrosion cracking of nickel base alloys has been of intense interest for plant operators worldwide. In this study, crack growth rates of Alloy 600 were measured in simulated PWR primary coolant at 330, °C with DH levels of 5, 16, 45 and 75, cc, H2/kg H2O, respectively. The oxide films formed in the crack tip regions were examined using transmission electron microscopy (TEM). The results show low and similar crack growth rates at all DH levels, without a maximum at 16, cc, H2/kg H2O. The low DH content favors nickel oxide formation at the crack tip region, whereas the high DH level favors Me3O4 type spinel formation. Also, the oxide films were found to grow epitaxially on some metal grain surfaces in the cracks. The possible effects of alloy composition on the oxide films formed, and the effect of DH on the crack growth are briefly discussed.
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| 4. |
- Bi, G., et al.
(författare)
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Feasibility study on the Laser Aided Additive Manufacturing of die inserts for liquid forging
- 2010
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Ingår i: Materials & Design. - : Elsevier BV. - 0261-3069. ; 31:SUPPL. 1, s. S112-S116
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the Laser Aided Additive Manufacturing of nickel-base alloy Nimonic 80A for the purpose of direct building of die inserts for liquid forging. Low porosity level of 0.01-0.04% with reasonable deposition rate was achieved. The micro-hardness showed very good homogeneity. Directionally solidified cellular micro-structure with an average size of 5Όm was observed. Very fine MC-type carbides were detected at the grain boundaries, which function as the strengthening phase of the alloy. © 2009 Elsevier Ltd.
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| 5. |
- Cassagne, Thierry B., et al.
(författare)
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Replacing titanium in sea water plate heat exchangers
- 2010
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Ingår i: NACE - International Corrosion Conference Series.
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Konferensbidrag (refereegranskat)abstract
- The use of titanium plate heat exchangers is widespread for Offshore and Coastal installations where seawater cooling is required. Several years ago difficulties to supply titanium Grade 1 for this application triggered the need for qualification of other alloys for this application. Applications using passive alloys are especially susceptible to crevice corrosion when exposed to hot seawater. Since titanium is the most corrosion resistant alloy in seawater only highly corrosion resistant alloys could be considered for its replacement in plate heat exchangers. In addition since they need to be shaped into plates by cold pressing only alloys with a high formability could be selected. This narrowed even further candidate alloys for plate heat exchangers. In this study nickel chromium molybdenum alloys and a highly alloyed stainless steel were tested between 30 and 70°C in natural seawater with up to 1 ppm free chlorine. Rather than using short term electrochemical testing that is often difficult to compare with service performance long term exposure tests (up to 18 months) of real plate heat exchangers were carried out. These tests are considered to be more representative of actual service conditions. The results of these tests and their significance are discussed and compared with previous reported work.
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| 6. |
- Chen, Jiaxin, et al.
(författare)
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Microstructures of oxide films formed in alloy 182 BWR core shroud support leg cracks
- 2018
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Ingår i: Miner. Met. Mater. Ser.. - Cham : Springer International Publishing. - 9783319684536 ; Part F11, s. 417-431
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Konferensbidrag (refereegranskat)abstract
- This paper contributes to a TEM examination on the oxide films formed at three locations along a crack path in Alloy 182 weld from a BWR core shroud support leg, namely, the crack mouth, the midway between the mouth and the crack tip, and the crack tip. In the crack mouth the oxide film was approximately 1.6 μm in thickness and consisted of relatively pure NiO. The midway oxide film was mainly a nickel chromium oxide with a film thickness of 0.3 μm. At the crack tip the oxide film was a nickel chromium iron oxide with a film thickness of 30 nm. In all studied locations the main oxides had the similar rocksalt structure and the cracks were much wider than the thicknesses of the oxide films. It probably suggests that the corroded metal was largely dissolved into the coolant. The different dissolution rates of nickel, chromium and iron cations in the oxide films are clearly displayed with the compositions of the residual oxides. The oxide stability under different redox potentials along the crack path is briefly discussed.
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| 7. |
- Dueso, Cristina, 1977, et al.
(författare)
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Reactivity of a NiO/Al2O3 oxygen carrier prepared by impregnation for chemical-looping combustion
- 2010
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 89:11, s. 3399-3409
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Tidskriftsartikel (refereegranskat)abstract
- The reactivity of a Ni-based oxygen carrier prepared by hot incipient wetness impregnation (HIWI) on alpha-Al2O3 with a NiO content of 18 wt% was studied in this work. Pulse experiments with the reduction period divided into 4-s pulses were performed in a fluidized bed reactor at 1223 K using CH4 as fuel. The number of pulses was between 2 and 12. Information about the gaseous product distribution and secondary reactions during the reduction was obtained. In addition to the direct reaction of the combustible gas with the oxygen carrier, CH4 steam reforming also had a significant role in the process, forming H-2 and CO. This reaction was catalyzed by metallic Ni in the oxygen carrier and H-2 and CO acted as intermediate products of the combustion. No evidence of carbon deposition was found in any case. Redox cycles were also carried out in a thermogravimetric analyzer (TGA) with H-2 as fuel. Both tests showed that there was a relation between the solid conversion reached during the reduction and the relative amount of NiO and NiAl2O4 in the oxygen carrier. When solid conversion increased, the NiO content also increased, and consequently NiAl2O4 decreased. Approximately 20% of the reduced nickel was oxidized to NiAl2O4, regardless DXs. NiAl2O4 was also an active compound for the combustion reaction, but with lower reactivity than NiO. Further, the consequences of these results with respect to the design of a CLC system were investigated. When formation of NiAl2O4 occurred, the average reactivity in the fuel reactor decreased. Therefore, the presence of both NiO and NiAl2O4 phases must be considered for the design of a CLC facility. (C) 2010 Elsevier Ltd. All rights reserved.
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| 8. |
- Ebin, Burcak, 1983
(författare)
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Simple Preparation of Ni and NiO Nanoparticles Using Raffinate Solution Originated from Spent NiMH Battery Recycling
- 2018
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Ingår i: Journal of Inorganic and Organometallic Polymers and Materials. - : Springer Science and Business Media LLC. - 1574-1451 .- 1574-1443. ; 28:6, s. 2554-2563
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Tidskriftsartikel (refereegranskat)abstract
- Nickel (Ni) and nickel oxide (NiO) nanoparticles were produced by a combination of precipitation and reduction/calcination methods using the raffinate solution originated from laboratory scale spent NiMH recovery process. Ni recovery from the solution reached 99.8% by a simple precipitation step using baking soda. X-ray diffraction, FTIR spectroscopy, carbon analyzer and thermal gravimetric analysis techniques were used to characterize the precipitate. Metallic and oxide nanoparticles were obtained by hydrogen reduction and calcination under air atmosphere of the precipitate at 400 °C, respectively for 30–90 min residence times. The crystal structure, crystallite size, morphology, particle size and surface area of the samples, as well as carbon residue content in the particles were detected by particle characterization methods. The results indicate that spherical Ni nanoparticles have a crystallite size about 37 nm, and particle sizes of around 100 nm. The agglomeration of the nanoparticles reduces by increasing residence time. NiO nanoparticles have finer crystallite and particle sizes than the metallic samples produced at the same temperature and residence times. The results show that the combination of the simple methods presented can be an alternative process for producing advanced particles from spent NiMH batteries.
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| 9. |
- Larché, Nicolas, et al.
(författare)
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Effect of service conditions on the corrosion of nickel-aluminum bronze and copper-nickels alloys in seawater
- 2019
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Article number 13337Corrosion Conference and Expo 2019; Nashville; United States; 24 March 2019 through 28 March 2019. - : National Assoc. of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- Nickel-Aluminum Bronze (NAB) and Copper-Nickel alloys (CuNi) are commonly used in seawater environments due to their strength combined with a good corrosion resistance and a high resistance to biofouling. However, localized corrosion failures have been reported and are often attributed to abnormal service conditions. The effect of several service condition parameters on the localized corrosion of NAB (UNS C63000, CuAl10Ni5Fe4) and CuNi alloys 90/10 (UNS C70600) and 70/30 (UNS C71500) have been investigated in natural seawater. The results are compared with that of Aluminum-brass (UNS C68700). It includes flow conditions (flowing, quiescent and stagnant), chlorination, sulphide pollution, and crevice geometries. Exposures in both indoor (laboratory) and outdoor tanks (conditions promoting macro fouling) have been tested in temperate and in tropical seawaters. The corrosion stability of the protective oxide layer of the tested copper-based alloys was mainly affected by sulphide pollution in aerated seawater (general corrosion). Under the tested conditions, localized corrosion under-biodeposit clearly appeared as the critical failure for the tested alloys. The conditions for which biodeposit appeared critical for copper-nickel alloys was investigated.
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| 10. |
- Larché, Nicolas, et al.
(författare)
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Crevice and pitting corrosion of stainless-steel and nickel based alloys in deep sea water
- 2019
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Ingår i: NACE - International Corrosion Conference SeriesVolume 2019-March, 2019, Article number 13337Corrosion Conference and Expo 2019; Nashville; United States; 24 March 2019 through 28 March 2019. - : National Assoc. of Corrosion Engineers International.
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Konferensbidrag (refereegranskat)abstract
- The exploration and exploitation of deep seawater present promising prospects for many industries. Hence, the use of reliable materials resistant to corrosion in deep seawater conditions is required. In natural seawater, many parameters can influence the kinetics of corrosion such as: temperature, oxygen content, biofilm and fouling activity, flow rates and hydrostatic pressure. For passive materials such as Cr Ni Mo stainless steels and nickel-based alloys, the specificity of the above parameters in deep sea environment might have an impact on both initiation and propagation phases of localized corrosion (e.g. pitting and crevice corrosion), and no or limited field data obtained in deep sea can be found in the literature. Currently, there are still many questions on the corrosion behavior of metallic materials in deep seawater since the results obtained in laboratory or from near-surface seawater cannot be extrapolated to deep seawater environments, especially in terms of bacterial activity which can significantly impact the localized corrosion resistance of passive alloys (cf. biofilm-induced ennoblement). In this study, 13-Cr Ferritic, Austenitic, Lean Duplex, Duplex, Super Duplex, Super Austenitic, Hyper Duplex Stainless Steels and Nickel based alloys were exposed during 11 months at 1020 and 2020 m water depth in the Atlantic Ocean to evaluate their corrosion behavior. Structural carbon steel S355 was also exposed under similar conditions. Polyvinylidene difluoride (PVDF) crevice gaskets according to ISO18070:2015 were used to assess the crevice corrosion at two different gasket pressures, namely 3 and 20 N/mm2. Potential monitoring was performed in-situ (at both 1020 m and 2020 m) in order to characterize the formation of electroactive biofilms at the surface of passive alloys in these environments. At each exposure depth, the environment was characterized using environmental sensors, e.g. temperature, flow velocity, dissolved oxygen, salinity. The obtained results allowed i) ranking the passive material in terms of resistance to pitting and crevice corrosion in deep water at 4°C, ii) comparing biofilm electroactivity and corrosion rates at 1020 and 2020 m depth.
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