| 1. |
- Zendejas Medina, León, et al.
(författare)
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Enhancing corrosion resistance, hardness, and crack resistance in magnetron sputtered high entropy CoCrFeMnNi coatings by adding carbon
- 2021
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 205
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Tidskriftsartikel (refereegranskat)abstract
- This study explores carbon addition as a materials design approach for simultaneously improving the hardness, crack resistance, and corrosion resistance of high entropy thin films. CoCrFeMnNi was selected as a starting point, due to its high concentration of weak carbide formers. The suppression of carbides is crucial to the approach, as carbide formation can decrease both ductility and corrosion resistance. Films with 0, 6, and 11 at.% C were deposited by magnetron co-sputtering, using a graphite target and a sintered compound target. The samples with 0 at.% C crystallized with a mixture of a cubic closed packed (ccp) phase and the intermetallic chi-phase. With 6 and 11 at.% C, the films were amorphous and homogenous down to the nm-scale. The hardness of the films increased from 8 GPa in the carbon-free film to 16 GPa in the film with 11 at.% C. Furthermore, the carbon significantly improved the crack resistance as shown in fragmentation tests, where the crack density was strongly reduced. The changes in mechanical properties were primarily attributed to the shift from crystalline to amorphous. Lastly, the carbon improved the corrosion resistance by a progressive lowering of the corrosion current and the passive current with increasing carbon concentration.
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| 2. |
- Korvela, Marcus, 1986-, et al.
(författare)
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Development of a method using paperpoint stick sampling to determine Ti concentration in saliva with ICP-MS
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Peri-implantitis is a disease that causes an inflammatory process in soft tissues as well as bone loss around dental implants integrated into bone. The relationship between peri-implantitis and titanium presence has previously been established and also a correlation between the inflammation severity and Ti concentration in biopsies from patients with dental implants. Biopsy can be considered as an invasive sampling procedure and therefore there is an interest to study alternative sampling methods, such as collecting saliva with paperpoint sticks. The small volume absorbed by the paperpoint sticks requires a sensitive detection method for Ti, therefore ICP-MS was used. To minimize the effect of common polyatomic interferences on Ti, the use of He as a collision gas and complexation using NH3 as reaction gas were investigated and both methods were compared to each other. Three sample preparation techniques were investigated: leaching, ultrasonic extraction and microwave bomb digestion. The use of paperpoint sticks for sampling was shown to be a valid approach with simple leaching in combination with ICP-MS using either He- or NH3-gas. The use of NH3-gas to create a 131Ti-complex, required more technical expertise, but gave a 2 times lower detection limit compared to using He as a collision gas.
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| 3. |
- Korvela, Marcus, et al.
(författare)
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Internal standards in inductively coupled plasma mass spectrometry using kinetic energy discrimination and dynamic reaction cells
- 2018
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Ingår i: Journal of Analytical Atomic Spectrometry. - : ROYAL SOC CHEMISTRY. - 0267-9477 .- 1364-5544. ; 33:10, s. 1770-1776
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Tidskriftsartikel (refereegranskat)abstract
- ICP-MS is a sensitive element analysis technique used for analyzing several different sample types. This can result in difficult matrixes which can affect both physical parameters and create overlaps of analyte elements. Some of the possible overlaps can be reduced by the use of reaction and/or collision cells, while the use of internal standards can help with reducing the physical interferences caused by a matrix. While both internal standardization and the use of cells have been studied separately, their effects on each other have not been investigated earlier. In this study ICP-MS was used to analyze Mg-24, Al-27, Ti-47, Ti-49, V-51, Cr-52, Cr-53, Mn-55, Fe-57, Co-59, Ni-60, Ni-61, Ni-62, Cu-63, Cu-65, Zn-66, Zn-67, As-75, Se-78, Se-82, Cd-111, and Pb-208 with Be-9, Y-89, Ga-69, Rh-103, In-115, Ir-193, and Tl-205 as internal standards with high concentrations of either HNO3, PBS-buffer, or Triton X-100 as the matrix, in reaction-, collision- and standard-cell modes. This was done to investigate which internal standards would compensate matrix effects in different cell modes. All internal standards, except Be, compensated fairly well (relative sensitivity RSD < 10%) even for severe matrix effects for most elements regardless of similarity in mass in the different cell modes. For Zn, As and Se no proper internal standard could be found, of the ones investigated.
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| 4. |
- Korvela, Marcus, 1986-
(författare)
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Method development for the analysis of complex samples with inductively coupled plasma mass spectrometry
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis the development of methods for handling the problems associated with analyzing trace elements in complex matrixes using inductively coupled plasma mass spectrometry is presented. Trace elements such as Cu, Fe, Se, and Zn, to name a few, do play important roles in different organisms. Therefore it can be of importance to study trace elements in different samples of biological origin. As trace elements are low in abundance, sensitive instrumental techniques such as inductively coupled plasma mass spectrometry (ICP-MS) are required for accurate determination. Due to the complexity of samples with biological origin, careful method development, both regarding the sample preparation and instrumental analysis has to be performed to minimize negative effects on the instrument signal and introduction of interferences.For example the metal contents of mink livers were analyzed, after bomb digestion to investigate if the metal concentration could be linked to changes in the organ morphology as well as the minks’ environment. Morphological changes and capture locations could be linked to the metals investigated. The investigation of the elemental composition of cerebrospinal fluid from chronic pain patients using spinal cord stimulation electrode treatment on the other hand required less harsh sample treatment. No correlation between the spinal cord stimulation and element concentration could be found, but differences between patients and the control group were presented hinting that chronic pain intrinsically could affect the cerebrospinal fluid metal concentration. Another bodily fluid of interest is saliva and the use of paperpoint sticks as a sampling technique for Ti in saliva was investigated. As Ti is interfered by several components expected to be found in saliva, the use of reaction or collision gas was also investigated to reduce the effects of interferences. Simple leaching of the paperpoint sticks together with complexing the Ti with NH3 as reaction gas was shown to be optimal. Finally, how the selection of internal standard would be affected by the use of reaction and collision gases was also investigated. With collision gas most internal standards worked fine, while for reaction gas internal standard selection was harder. For elements with high ionization energy such as As, Se and Zn the choice of internal standard was very dependent on matrix. While ICP-MS suffers from problems when analyzing samples with complex matrixes many of them can be minimized by proper method development as shown in this thesis.
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| 5. |
- Korvela, Marcus, et al.
(författare)
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Quantification of 10 elements in human cerebrospinal fluid from chronic pain patients with and without spinal cord stimulation
- 2016
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Ingår i: Journal of Trace Elements in Medicine and Biology. - : Elsevier BV. - 0946-672X .- 1878-3252. ; 37, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Neuropathic pain affects 1-10% of the general population and is caused by a lesion or disease of the somatosensory nervous system. Spinal cord stimulation (SCS), a method where implanted electrodes stimulate the spinal cord, has been successfully used to treat drug-resistant neuropathic pain, but the mechanism of action is largely unknown. Studies show that SCS changes the protein levels in CSF (cerebrospinal fluid) of pain patients. Several neurological conditions have been shown to alter the elemental composition of CSF. Therefore changes in the levels of ions and trace elements in the CSF may correspond to SCS use. This study used ICP-MS (Inductively coupled plasma mass spectrometry) and ICP-AES (Inductively coupled plasma atomic emission spectroscopy) to quantify 10 elements in CSF from chronic neuropathic pain patients using SCS. The element concentrations in CSF from patients with SCS treatment on/off, were measured. No effect on the element concentrations in CSF from treatment with SCS could be detected. Also, the elemental concentrations in pooled CSF from patients without chronic neuropathic pain was determined and compared to the patients using SCS. The concentration of the elements Ca, Sr, Na, K, P, Mg and Ti were, significantly higher in patients compared to the CSF-control.
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| 6. |
- Ljungvall, Karl, et al.
(författare)
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Heavy metal concentrations in female wild mink (Neovison vison) in Sweden : Sources of variation and associations with internal organ weights
- 2017
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Ingår i: Environmental Toxicology and Chemistry. - : Wiley. - 0730-7268 .- 1552-8618. ; 36:8, s. 2030-2035
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Tidskriftsartikel (refereegranskat)abstract
- The American mink is an invasive species in Sweden, and it is legally hunted all year. Therefore, the mink is well suited as a sentinel species for environmental monitoring. In the present study female mink (n = 91) from 6 different areas in Sweden were analyzed for the concentrations of silver, cadmium, mercury and lead in liver tissue using inductively coupled plasma mass spectrometry. The wet concentrations in liver tissue were 42.6 +/- 52.7 ng/g for silver, 99.5 +/- 100 ng/g for cadmium, 652 +/- 537 ng/g formercury, and 196 +/- 401 ng/g for lead (expressed as mean + standard deviation). There were associations between the sample area and the concentrations of silver, lead, and mercury. The concentrations of lead and cadmium varied with season of capture and lead, cadmium, and mercury were positively associated with increasing age. Relative liver weight was positively associated with concentrations of mercury and negatively associated with lead and cadmium. Relative kidney weight was negatively associated with lead concentrations. In summary, it is of importance to take age and season of capture into account when assessing levels of heavy metals in wild mink. Also, liver and kidneys seem to be potential targets for heavy metal toxicity in wild female mink in Sweden.
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| 7. |
- Ottosson, Mikael, 1962-, et al.
(författare)
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Copper in ultrapure water, a scientific issue under debate
- 2017
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Ingår i: Corrosion Science. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0010-938X .- 1879-0496. ; 122, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion properties of copper in ultrapure water have been studied experimentally by submerging copper samples (99.9999%) in pure water for up to 29 months. The surface was first electropolished at ambient temperature, then exposed to hydrogen gas treatment at 300-400 degrees C, thereby reducing the bulk hydrogen content to 0.03 ppm. These copper samples, the water and the glassware were all then subjected to precise chemical analysis. Great care was taken to avoid contamination. After exposure, only similar to 6 mu g/L copper had accumulated in the water phase. Electron spectroscopy could not detect Cu2O or any other oxidation products containing copper.
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| 8. |
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| 9. |
- Srinath, Aishwarya, 1991-, et al.
(författare)
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An investigation of the corrosion resistances of magnetron sputtered TaW-rich, Nb-rich, and multicomponent CrNbTaTiW alloys
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The corrosion resistances of magnetron sputtered nearequimolar, TaW-rich, and Nb-rich CrNbTiTaW alloys, with and without 8 at.% carbon, were studied in aqueous chloride-containing environments. Electrochemical tests and scanning electron images showed that all the CrNbTaTiW alloys were highly corrosion resistant in 1.0 M HCl. The results conclusively showed that passivated nearequimolar CrNbTaTiW coatings have comparable corrosion performances to passivated Nb- and TaW-rich alloys in 0.01 M HCl + 0.1 M NaCl. Carbon affected the rate of surface repassivation in polarisation measurements of the films whose oxide had been partially reduced, but had a minor influenceon the corrosion resistances once a mature oxide was formed. No conclusive relationships between microstructure and corrosion resistance were established. The comparable corrosion resistances of the multicomponent CrNbTiTaW, Nb-rich and TaW-rich alloys were attributed to the presence of extremely stable surface oxides of Nb and Ta which prevented losses of Ti and Cr. The near surface regions of all the alloys before and after corrosion appeared to be depleted in W compared to the bulk.
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| 10. |
- Srinath, Aishwarya, et al.
(författare)
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Influence of the nitrogen content on the corrosion resistances of multicomponent AlCrNbYZrN coatings
- 2021
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 188
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the relationship between the nitrogen content and the corrosion resistances of non-equimolar multicomponent AlCrNbYZrN films (N = 13-49 at.%) is probed. While there was no linear relationship between nitrogen content and corrosion resistance, the results clearly show that the corrosion resistances of the films were instead determined by their nitrogen-induced porosities i.e. the less porous the sample, the higher the corrosion resistance. The 23, 30 and 37 at.% N samples were denser while the 13 at.% N sample was porous and the 49 at.% N film had an underdense nanocrystalline columnar cross section permitting the ingress of electrolyte.
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