| 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. |
- Lif, Johan, 1964, et al.
(författare)
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Sintering of alumina-supported nickel particles under amination conditions: Support effects
- 2007
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Ingår i: Applied Catalysis A: General. - : Elsevier BV. - 1873-3875 .- 0926-860X. ; 317:1, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- The sintering of alumina-supported nickel particles has been studied after heat-treatment in ammonia + hydrogen at 523 K and 250 bar. The investigated samples were nickel supported on gamma-alumina, transalumina and alpha-alumina, and co-precipitated nickel oxide-alumina. The sintering process was mainly followed by hydrogen chemisorption. The samples were also characterised by specific surface area measurements, X-ray diffraction, temperature programmed desorption of ammonia, in situ FTIR spectroscopy and temperature programmed reduction. For nickel supported on gamma-alumina, up to 40 % of the initial metal surface area remained after the heat-treatment in ammonia + hydrogen compared with alpha-alumina or transalumina where only 10-20 % of the initial metal surface area remained after the heat-treatment. The sintering can be correlated to the bond strength between the metal particle and the support. The larger the number of low-coordinated surface aluminium sites is, as for gamma-alumina, the stronger the metal-support interaction is and this in turn suppresses diffusion of nickel particles and /or atoms
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| 9. |
- Lindahl, Erik, 1979-
(författare)
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Thin Film Synthesis of Nickel Containing Compounds
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Most electrical, magnetic or optical devices are today based on several, usually extremely thin layers of different materials. In this thesis chemical synthesis processes have been developed for growth of less stable and metastable layers, and even multilayers, of nickel containing compounds. A chemical vapor deposition (CVD) method for deposition of metastable Ni3N has been developed. The deposition process employs ammonia as nitrogen precursor. An atomic layer deposition (ALD) process for deposition of both polycrystalline and epitaxial NiO and using low oxygen activity, has also been developed. Both deposition processes utilizes bis(2,2,6,6-tetramethyl-3,5-heptanedionato)nickel(II) (Ni(thd)2) as the metal precursor. The Ni3N deposition proceeds via surface reactions. The growth rate is very sensitive to the partial pressure of ammonia, why adsorbed –NHx species are believed to be of importance for the film growth. Similar reactions can be expected between the metal precursor and H2O. For ALD of NiO a large excess of water was needed For the multilayered structures of Ni3N/NiO, growth processes, working at low activities of oxygen and hydrogen, are needed to avoid oxidation or reduction of the underlying layer. Chemical vapor growth methods such as CVD and ALD are often suffering from using high activities of hydrogen or oxygen to deposit metals and oxides. An alternative deposition pathway for metal deposition, without any hydrogen in the vapor, has been demonstrated. The metal has been formed by decomposition of the metastable nitride Ni3N in a post-annealing process. Ni3N decomposes via different mechanisms, depending on environment in the annealing process. The different mechanisms result in different degrees of ordering in the resulting Ni films. From the knowledge gained about the chemical growth of NiO and Ni3N as well as the decomposition of Ni3N, well-defined multilayer structures have been produced in different combinations of NiO, Ni3N and Ni.
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| 10. |
- Odnevall Wallinder, Inger, et al.
(författare)
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Corrosion-induced release and environmental interaction of chromium, nickel and iron from stainless steel
- 2006
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Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 170:1-4, s. 17-35
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Tidskriftsartikel (refereegranskat)abstract
- A cross-disciplinary research project has been implemented because of increased awareness of the potential environmental effects caused by dispersion of metals from external applications into the environment. The work comprises a 4-year (1998-2002) field exposure of grades 304 and 316 stainless steels, and a laboratory percolation study simulating 20-25 years of chromium and nickel containing runoff water interactions with soil. Total metal annual release rates varied between 0.2 and 0.7 mg m(-2) yr(-1) for Cr, between 0.1 and 0.8 mg m(-2) yr(-1) for Ni and between 10 and 200 mg m(-2) yr(-1) for Fe. Most Cr and Ni is present in an ionic form as a result of the limited presence of organic matter at the immediate release situation. Metal ion concentrations in the runoff water are far below reported ecotoxic concentrations. Studies of the environmental interaction between runoff water from stainless steel and soil show the majority of released Cr and Ni to be retained and their concentrations in percolation water to be very low (0.5-1 mu g L-1 and 1-5.5 mu g L-1 for Cr and Ni, respectively). Speciation calculations showed Cr to be primarily complexed to dissolved organic carbon while Ni also was present in an ionic form in the solution phase. Soil extractions showed Cr and Ni to be very strongly retained within the soil.
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