| 1. |
- Nicolenco, Aliona, et al.
(författare)
-
Nanocrystalline Electrodeposited Fe-W/Al2O3 Composites: Effect of Alumina Sub-microparticles on the Mechanical, Tribological, and Corrosion Properties
- 2019
-
Ingår i: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 7:MAR, s. 241-
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, nanocrystalline Fe-Walloy and Fe-W/Al2O3 composite coatings with various contents of sub-microsized alumina particles have been obtained by electrodeposition from an environmentally friendly Fe(III)-based electrolyte with the aim to produce a novel corrosion and wear resistant material. The increase in volume fraction of Al2O3 in deposits from 2 to 12% leads to the grain refinement effect, so that the structure of the coatings change from nanocrystalline to amorphous-like with grain sizes below 20 nm. Nevertheless, the addition of particles to the Fe-W matrix does not prevent the development of a columnar structure revealed for all the types of studied coatings. The observed reduction in both hardness and elastic modulus of the Fe-W/Al2O3 composites is attributed to the apparent grain size refinement/amorphization and the nanoporosity surrounding the embedded Al2O3 particles. In the presence of 12 vol% of Al2O3 in deposits, the wear rate decreases by a factor of 10 as compared to Fe- W alloy tested under dry friction conditions due to the lowering of tribo-oxidation. The addition of alumina particles slightly increases the corrosion resistance of the coatings; however, the corrosion in neutral chloride solution occurs through the preferential dissolution of Fe from the matrix. The obtained results provide a possibility to integrate the nanocrystalline Fe-W/Al2O3 composite coatings into various systems working under dry friction conditions, for example, in high-temperature vacuum systems.
|
|
| 2. |
- Bartkowska, Aleksandra, et al.
(författare)
-
Accelerated biodegradation of FeMn porous alloy coated with ZnO: Effect on cytocompatibility and antibiofilm properties
- 2023
-
Ingår i: Surface and Coatings Technology. - 0257-8972. ; 471
-
Tidskriftsartikel (refereegranskat)abstract
- Fe-based alloys are being studied as potential candidates for biodegradable implants; however, their degradation rates remain too slow. To accelerate biodegradation while simultaneously hindering biofilm formation, a ZnO coating was deposited onto porous equiatomic FeMn alloy discs by sol-gel method using dip coating. The effect of the ZnO coating on the microstructure, biodegradability, cytocompatibility, and antibacterial properties were investigated. Biodegradability experiments were performed by immersing the specimens in Hank's balanced salt solution and measuring ion release after up to 28 days of immersion. The experiments showed an increased degradation of the FeMn/ZnO sample due to Fe segregation towards the grain boundaries, formation of iron-manganese oxide, and limited formation of degradation products on ZnO. Further, indirect Saos-2 cell cytotoxicity testing in 24 h sample-conditioned media showed no significant cytotoxicity in concentrations equal to or below 50 %. In addition, the total biofilm biovolume formed by Staphylococcus aureus on the FeMn/ZnO surface was significantly reduced compared to the uncoated FeMn. Taken together, these results show that the ZnO coating on FeMn improves the degradation rate, maintains cytocompatibility, and reduces biofilm accumulation when compared to an uncoated FeMn alloy.
|
|
| 3. |
- Bartkowska, Aleksandra, et al.
(författare)
-
Biodegradable porous FeMn(-xAg) alloys: assessment of cytocompatibility, mechanical, magnetic and antibiofilm properties
- 2023
-
Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 4:2, s. 616-630
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, porous FeMn(-xAg) alloys are fabricated through powder metallurgy methods. The effects of porosity and Ag addition on the microstructure, biodegradability, magnetic and mechanical properties of the alloys are investigated. Studies on the cytocompatibility, inflammatory cytokine response and antibacterial effect are also conducted. The fabricated alloys exhibit a macro- and nanoporous structure, with uniformly distributed silver particles. The biodegradability tests reveal that the release of Mn to the Hank's solution is higher than that of Fe, without significant differences between the alloys. The degradation products consist mainly of Fe, Mn, O and compounds enriched in Ca, P and Cl. As-sintered alloys show a low saturation magnetization value (below 1 emu g−1), which does not increase significantly with immersion time. The results on biocompatibility indicate that all tested alloys are non-cytotoxic, but the addition of Ag might interfere with cell proliferation. However, the ions released by the FeMn(-xAg) alloys do not induce an inflammatory response in macrophages. The obtained results on microbiological interactions reveal that although no significant bactericidal effect is observed at 4 h between FeMn control and FeMn-5Ag, a significant reduction in the total biofilm biomass of both live and dead bacteria is observed after 24 h in Ag containing FeMn-5Ag surfaces.
|
|
| 4. |
- Eiler, Konrad, et al.
(författare)
-
Oxygen reduction reaction and proton exchange membrane fuel cell performance of pulse electrodeposited Pt–Ni and Pt–Ni–Mo(O) nanoparticles
- 2022
-
Ingår i: Materials Today Energy. - : Elsevier Ltd. - 2468-6069. ; 27
-
Tidskriftsartikel (refereegranskat)abstract
- Proton exchange membrane fuel cells (PEMFCs) are an important alternative to fossil fuels and a complement to batteries for the electrification of vehicles. However, their high cost obstructs commercialization, and the catalyst material, including its synthesis, constitutes one of the major cost components. In this work, Pt–Ni and Pt–Ni–Mo(O) nanoparticles (NPs) of varying composition have been synthesized in a single step by pulse electrodeposition onto a PEMFC's gas diffusion layer. The proposed synthesis route combines NP synthesis and their fixation onto the microporous carbon layer in a single step. Both Pt–Ni and Pt–Ni–Mo(O) catalysts exhibit extremely high mass activities at oxygen reduction reaction (ORR) with very low Pt loadings of around 4 μg/cm2 due to the favorable distribution of NPs in contact with the proton exchange membrane. Particle sizes of 40–50 nm and 40–80 nm were obtained for Pt–Ni and Pt–Ni–Mo(O) systems, respectively. The highest ORR mass activities were found for Pt67Ni33 and Pt66Ni32–MoOx NPs. The feasibility of a single-step electrodeposition of Pt–Ni–Mo(O) NPs was successfully demonstrated; however, the ternary NPs are of more amorphous nature in contrast to the crystalline, binary Pt–Ni particles, due to the oxidized state of Mo. Nevertheless, despite their heterogeneous nature, the ternary NPs show homogeneous behavior even on a microscopic scale. © 2022 The Author(s)
|
|
| 5. |
- Klement, Uta, 1962, et al.
(författare)
-
Mid-term meeting of SELECTA: a European Training Network on smart electrodeposited alloys for environmentally sustainable applications
- 2017
-
Ingår i: Transactions of the Institute of Metal Finishing. - : Informa UK Limited. - 1745-9192 .- 0020-2967. ; 95:3, s. 124-125
-
Tidskriftsartikel (refereegranskat)abstract
- Integrating sustainability with technologicalprogress is becoming oneof the major challenges in modernsociety. Since research agendas aremainly driven by the push for incessanteconomic growth, there is therisk of reaching a critical point wheretechnological advances will nolonger be possible due to the imbalancebetween demand and availabilityof natural resources. To facethis issue, the European TrainingNetwork ‘Smart ELECTrodepositedAlloys for environmentally sustainableapplications: from advancedprotective coatings to micro/nanoroboticplatforms’ (SELECTA) waslaunched in January 2015. SELECTAaims to integrate technological progresswith environmental sustainabilityconcerns, which is one of themajor ‘Societal Challenges’ listed inthe Horizon 2020 Work Programme.
|
|
| 6. |
- Mulone, Antonio, 1989, et al.
(författare)
-
Enhanced mechanical properties and microstructural modifications in electrodeposited Fe-W alloys through controlled heat treatments
- 2018
-
Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 350, s. 20-30
-
Tidskriftsartikel (refereegranskat)abstract
- Among W alloys, Fe-W has seen much attention recently, due to the need of moving toward the design of environmentally friendly materials. Coatings with 4, 16 and 24 at.% of W were electrodeposited from an environmental friendly Fe(III)-based glycolate-citrate bath. The samples were annealed in vacuum at different temperatures up to 800 °C. Different crystalline phases are formed upon annealing: α-Fe, Fe2W, Fe3W3C, Fe6W6C, and FeWO4. Their grain size and distribution within the coating was studied by means of Electron Backscattered Diffraction (EBSD) technique. The effect of annealing on the mechanical properties of the coatings was analyzed performing nanoindentation measurements. The results show a considerable increase of the hardness followed by a rapid decrease at higher temperatures. The highest hardness value, i.e. 16.5 GPa, is measured for the sample with 24 at.% of W after annealing at 600 °C owing to the precipitation of α-Fe crystallites. This study indicates the possibility to substantially increase the hardness of electrodeposited Fe-W coatings by optimization of the annealing treatment. In addition, the critical influence of the carbide and oxide phases on the mechanical properties of alloys is discussed. Hence, Fe-W coatings rich in W can be applied as a possible candidate for protective coating applications at elevated temperatures.
|
|
| 7. |
- Mølmen, Live, et al.
(författare)
-
Recent advances in catalyst materials for proton exchange membrane fuel cells
- 2021
-
Ingår i: APL Materials. - : American Institute of Physics Inc.. - 2166-532X. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- Research on fuel cell technology is constantly gaining importance, while global emission requirements are becoming more and more restrictive. For environmentally neutral proton exchange membrane fuel cells (PEMFCs) to become a competitive technology, sustainable infrastructures need to be established. One of the main showstoppers is the utilization of the rare and therefore costly precious metal Pt as the key element in the electrocatalysis of hydrogen and oxygen. A huge amount of research is done on immensely reducing or even replacing Pt for future PEMFC technology. In this research update, the progress on oxygen reduction reaction catalysts in acidic media over the past two years is reviewed, with special attention to their durability. © 2021 Author(s).
|
|
| 8. |
|
|
| 9. |
- Pellicer, Miquel, et al.
(författare)
-
Poor people’s beliefs and the dynamics of clientelism
- 2021
-
Ingår i: Journal of Theoretical Politics. - : SAGE Publications. - 0951-6298 .- 1460-3667. ; 33:3, s. 300-332
-
Tidskriftsartikel (refereegranskat)abstract
- Why do some poor people engage in clientelism whereas others do not? Why does clientelism sometimes take traditional forms and sometimes more instrumental forms? We propose a formal model of clientelism that addresses these questions focusing primarily on the citizen’s perspective. Citizens choose between supporting broad-based redistribution or engaging in clientelism. Introducing insights from social psychology, we study the interactions between citizen beliefs and values, and their political choices. Clientelism, political inefficacy, and inequality legitimation beliefs reinforce each other leading to multiple equilibria. One of these resembles traditional clientelism, with disempowered clients that legitimize social inequalities. Community connectivity breaks this reinforcement mechanism and leads to another equilibrium where clientelism takes a modern, instrumental, form. The model delivers insights on the role of citizen beliefs for their bargaining power as well as for the persistence and transformation of clientelism. We illustrate the key mechanisms with ethnographic literature on the topic.
|
|
| 10. |
- Schütz, Christina, et al.
(författare)
-
Hard and Transparent Films Formed by Nanocellulose-TiO2 Nanoparticle Hybrids
- 2012
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:10, s. e45828-
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of hybrids of nanofibrillated cellulose and titania nanoparticles in aqueous media has been studied. Their transparency and mechanical behavior have been assessed by spectrophotometry and nanoindentation. The results show that limiting the titania nanoparticle concentration below 16 vol% yields homogeneous hybrids with a very high Young's modulus and hardness, of up to 44 GPa and 3.4 GPa, respectively, and an optical transmittance above 80%. Electron microscopy shows that higher nanoparticle contents result in agglomeration and an inhomogeneous hybrid nanostructure with a concomitant reduction of hardness and optical transmittance. Infrared spectroscopy suggests that the nanostructure of the hybrids is controlled by electrostatic adsorption of the titania nanoparticles on the negatively charged nanocellulose surfaces.
|
|
