| 1. |
- Lopez-Ortega, Alberto, et al.
(författare)
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Size-Dependent Passivation Shell and Magnetic Properties in Antiferromagnetic/Ferrimagnetic Core/Shell MnO Nanoparticles
- 2010
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 132:27, s. 9398-9407
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of bimagnetic core/shell nanoparticles consisting of an antiferromagnetic MnO core and a ferrimagnetic passivation shell have been investigated. It is found that the phase of the passivation shell (gamma-Mn2O3 or Mn3O4) depends on the size of the nanoparticles. Structural and magnetic characterizations concur that while the smallest nanoparticles have a predominantly gamma-Mn2O3 shell, larger ones have increasing amounts of Mn3O4. A considerable enhancement of the Neel temperature, T-N, and the magnetic anisotropy of the MnO core for decreasing core sizes has been observed. The size reduction also leads to other phenomena such as persistent magnetic moment in MnO up to high temperatures and an unusual temperature behavior of the magnetic domains.
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| 2. |
- Bartkowska, Aleksandra, et al.
(författare)
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Accelerated biodegradation of FeMn porous alloy coated with ZnO: Effect on cytocompatibility and antibiofilm properties
- 2023
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Ingår i: Surface and Coatings Technology. - 0257-8972. ; 471
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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.
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| 3. |
- Bartkowska, Aleksandra, et al.
(författare)
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Biodegradable porous FeMn(-xAg) alloys: assessment of cytocompatibility, mechanical, magnetic and antibiofilm properties
- 2023
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Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 4:2, s. 616-630
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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.
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| 4. |
- Cordero-Edwards, Kumara, et al.
(författare)
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Flexoelectric Fracture-Ratchet Effect in Ferroelectrics
- 2019
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 122:13
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Tidskriftsartikel (refereegranskat)abstract
- The propagation front of a crack generates large strain gradients and it is therefore a strong source of gradient-induced polarization (flexoelectricity). Herein, we demonstrate that, in piezoelectric materials, a consequence of flexoelectricity is that crack propagation is helped or hindered depending on whether it is parallel or antiparallel to the piezoelectric polar axis. The discovery of crack propagation asymmetry proves that fracture physics cannot be assumed to be symmetric in polar materials, and indicates that flexoelectricity should be incorporated in any realistic model.
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| 5. |
- Eiler, Konrad, et al.
(författare)
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Oxygen reduction reaction and proton exchange membrane fuel cell performance of pulse electrodeposited Pt–Ni and Pt–Ni–Mo(O) nanoparticles
- 2022
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Ingår i: Materials Today Energy. - : Elsevier Ltd. - 2468-6069. ; 27
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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)
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| 6. |
- Farhadi-Khouzani, Masoud, et al.
(författare)
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A CaCO3/nanocellulose-based bioinspired nacre-like material
- 2017
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 5:31, s. 16128-16133
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Tidskriftsartikel (refereegranskat)abstract
- Nacre continues to be an inspiration for the fabrication of strong and tough materials from renewable and earth-abundant raw materials. Herein, we showed how a nacre-like hybrid material based on nanocellulose (NC) and CaCO3 can be prepared via the sequential infiltration of polymer-stabilised CaCO3 liquid precursors into layers of predeposited NC films. Layer-by-layer assembly of the NC films followed by controlled spreading and infiltration with liquid CaCO3 precursors generated a lamellar material with an architecture and iridescent appearance similar to those of nacre. The wettability of the NC films towards the liquid CaCO3 precursors was controlled by hydroxyl and carboxyl functionalization of the NC fibrils and the addition of magnesium ions. The combination of a high stiffness and plasticity of the nacre-like NC/CaCO3 hybrid materials show that excellent mechanical properties can be obtained employing a fibrillar organic constituent that is relatively hard. The fabrication of a nacrelike hybrid material via an aqueous route of assembly and infiltration processing demonstrates how a sustainable composite material with outstanding properties can be produced using the most abundant biopolymer and biomineral on earth.
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| 7. |
- Gebauer, Denis, et al.
(författare)
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A transparent hybrid of nanocrystalline cellulose and amorphous calcium carbonate nanoparticles
- 2011
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Ingår i: NANOSCALE. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 3:9, s. 3563-3566
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Tidskriftsartikel (refereegranskat)abstract
- Nanocellulose hybrids are promising candidates for biodegradable multifunctional materials. Hybrids of nanocrystalline cellulose (NCC) and amorphous calcium carbonate (ACC) nanoparticles were obtained through a facile chemical approach over a wide range of compositions. Controlling the interactions between NCC and ACC results in hard, transparent structures with tunable composition, homogeneity and anisotropy.
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| 8. |
- Klement, Uta, 1962, et al.
(författare)
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Mid-term meeting of SELECTA: a European Training Network on smart electrodeposited alloys for environmentally sustainable applications
- 2017
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Ingår i: Transactions of the Institute of Metal Finishing. - : Informa UK Limited. - 1745-9192 .- 0020-2967. ; 95:3, s. 124-125
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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.
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| 9. |
- Kovalska, Natalia, et al.
(författare)
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Electrodeposition of Soft Magnetic Fe-W-P Alloy Coatings from an Acidic Electrolyte
- 2023
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Ingår i: Coatings. - 2079-6412. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Fe-W-P coatings were deposited from a newly developed electrolytic bath. The effect of plating parameters, such as electrolyte current density and pH has been studied. It was found that the pH has a very strong effect on the phosphorous content of the coatings. Metallic-like, non-powdery alloys of Fe-W-P deposits with no cracks (lowly stressed) can be obtained at a lower pH (<3), exhibiting high phosphorus (up to 13 at.%) and low tungsten (6 at.%) contents. At a higher pH (>3), the composition changes to low phosphorus and high tungsten content, showing a matte, greyish, and rough surface. The applied current density also influences the morphology and the amount of phosphorous content. The deposits showed an amorphous structure for all samples with soft ferromagnetic properties.
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| 10. |
- Krycka, Kathryn L., et al.
(författare)
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Resolving Material-Specific Structures within Fe3O4 vertical bar gamma-Mn2O3 Core vertical bar Shell Nanoparticles Using Anomalous Small-Angle X-ray Scattering
- 2013
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 7:2, s. 921-931
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Tidskriftsartikel (refereegranskat)abstract
- Here it is demonstrated that multiple-energy, anomalous small-angle X-ray scattering (ASAXS) provides significant enhancement in sensitivity to internal material boundaries of layered nanoparticles compared with the traditional modeling of a single scattering energy, even for cases in which high scattering contrast naturally exists. Specifically, the material-specific structure of monodispersed Fe3O4 vertical bar gamma-Mn2O3 core vertical bar shell nanoparticles is determined, and the contribution of each component to the total scattering profile is identified with unprecedented clarity. We show that Fe3O4 vertical bar gamma-Mn2O3 core vertical bar shell nanoparticles with a diameter of 8.2 +/- 0.2 nm consist of a core with a composition near Fe3O4 surrounded by a (MnxFe1-x)(3)O-4 shell with a graded composition, ranging from x approximate to 0.40 at the Inner shell toward x approximate to 0.46 at the surface. Evaluation of the scattering contribution arising from the interference between material-specific layers additionally reveals the presence of Fe3O4 cores without a coating shell. Finally, it is found that the material-specific scattering profile shapes and chemical compositions extracted by this method are independent of the original input chemical compositions used in the analysis, revealing multiple-energy ASAXS as a powerful tool for determining internal nanostructured morphology even if the exact composition of the individual layers is not known a priori.
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| 11. |
- Mulone, Antonio, 1989, et al.
(författare)
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Effect of heat treatments on the mechanical and tribological properties of electrodeposited Fe–W/Al2O3 composites
- 2020
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 448-449
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the influence of heat treatment on the mechanical and tribological properties of electrodeposited Fe–W/Al2O3 composite coatings is studied. The properties of the as-deposited and annealed composites are compared with those of electrodeposited hard chromium coatings. The amorphous structure of the Fe–W matrix transforms into a mixed amorphous-crystalline structure upon annealing at 600 °C for 1 h. The observed microstructural transformations result in a substantial increase of both the hardness and the reduced Young's modulus of the Fe–W/Al2O3 composite coatings, reaching values of 16.3 GPa and 191.7 GPa, respectively. The results on the wear resistance studied under dry friction using ball-on-disc sliding tests show that a low wear rate is obtained for both as-deposited and annealed composite coatings, i.e. ~1.5 × 10−6 mm3/Nm. In contrast, the heat treatments are detrimental for both the hardness and wear resistance of hard chromium coatings. As a consequence, the mechanical and wear properties of the electrodeposited Fe–W/Al2O3 composite coatings, especially after annealing, are superior to the properties of hard chromium coatings. Hence, Fe–W/Al2O3 composite coatings can be considered as a valid and sustainable alternative to hard chromium coatings, particularly in applications where these materials may be exposed to high temperatures.
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| 12. |
- Mulone, Antonio, 1989, et al.
(författare)
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Enhanced mechanical properties and microstructural modifications in electrodeposited Fe-W alloys through controlled heat treatments
- 2018
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 350, s. 20-30
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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.
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| 13. |
- Nicolenco, Aliona, et al.
(författare)
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Nanocrystalline Electrodeposited Fe-W/Al2O3 Composites: Effect of Alumina Sub-microparticles on the Mechanical, Tribological, and Corrosion Properties
- 2019
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Ingår i: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 7:MAR, s. 241-
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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.
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| 14. |
- Salazar-Alvarez, German, et al.
(författare)
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Enhanced coercivity in Co-rich near-stoichiometric CoFe3-xO4+delta nanoparticles prepared in large batches
- 2007
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 19:20, s. 4957-4963
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between the structure and composition with the magnetic properties of near stoichiometric cobalt ferrite nanoparticles CoxFe3-xO4+delta (0.85 < x < 1.1) prepared in large batches with average sizes in the range 60-210 nm has been investigated. Chemical analysis and Rietveld refinement of the X-ray diffraction data in conjunction with Mossbauer spectroscopy allowed us to identify an interplay between particle size, microstructure (concentration of interstitial ions, microstrain, cation arrangement in octahedral and tetrahedral sites), and composition, which sensitively controls the magnetic properties such as coercivity and saturation magnetization. In all cases, cobalt-rich compositions resulted in a higher coercivity, whereas lower degrees of inversion and higher iron contents led to slightly higher saturation magnetization values.
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| 15. |
- Salazar-Alvarez, German, et al.
(författare)
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Reversible post-synthesis tuning of the superparamagnetic blocking temperature of gamma-Fe2O3 nanoparticles by adsorption and desorption of Co(II) ions
- 2007
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 17:4, s. 322-328
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the post-synthesis adsorption of Co(II) ions on the structural and magnetic properties of maghemite (gamma-Fe2O3) nanoparticles with a mean particle size of about 10 nm has been investigated. It is shown that the step-wise adsorption of Co( II) can controllably increase the blocking temperature, T-B, of the system up to 60 K with respect to that of untreated particles, while neither the particle size nor the particle size distribution are significantly modified. This is accompanied by a four-fold increase in the coercivity, H-C, at low temperatures. Using a selective leaching of the previously adsorbed Co(II) ions the T-B and H-C values of the pristine gamma-Fe2O3 nanoparticles are recovered. Hence, a reversible and controllable tailoring of the magnetic properties (e.g., T-B and H-C) of the gamma-Fe2O3 nanoparticles can be achieved by a simple adsorption and desorption process of Co( II) ions after their synthesis.
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| 16. |
- Salazar-Alvarez, German, et al.
(författare)
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Tunable High-Field Magnetization in Strongly Exchange-Coupled Freestanding Co/CoO Core/Shell Coaxial Nanowires
- 2016
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 8:34, s. 22477-22483
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Tidskriftsartikel (refereegranskat)abstract
- The exchange bias properties of Co/CoO coaxial core/shell nanowires were investigated with cooling and applied fields perpendicular to the wire axis. This configuration leads to unexpected exchange-bias effects. First, the magnetization value at high fields is found to depend on the field-cooling conditions. This effect arises from the competition between the magnetic anisotropy and the Zeeman energies for cooling fields perpendicular to the wire axis. This allows imprinting predefined magnetization states to the antiferromagnetic (AFM) shell, as corroborated by micromagnetic simulations. Second, the system exhibits a high-field magnetic irreversibility, leading to open hysteresis loops attributed to the AFM easy axis reorientation during the reversal (effect similar to athermal training). A distinct way to manipulate the high-field magnetization in exchange-biased systems, beyond the archetypical effects, was thus experimentally and theoretically demonstrated.
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| 17. |
- Salazar-Alvarez, German, et al.
(författare)
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Two-, Three-, and Four-Component Magnetic Multilayer Onion Nanoparticles Based on Iron Oxides and Manganese Oxides
- 2011
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 133:42, s. 16738-16741
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic multilayered, onion-like, hetero-structured nanoparticles are interesting model systems for studying magnetic exchange coupling phenomena. In this work, we synthesized heterostructured magnetic nanopartides composed of two, three, or four components using iron oxide seeds for the subsequent deposition of manganese oxide. The MnO layer was allowed either to passivate fully in air to form an outer layer of Mn(3)O(4) or to oxidize partially to form MnO vertical bar Mn(3)O(4) double layers. Through control of the degree of passivation of the seeds, particles with up to four different magnetic layers can be obtained (i.e., FeO vertical bar Fe(3)O(4)vertical bar MnO vertical bar Mn(3)O(4)). Magnetic characterization of the samples confirmed the presence of the different magnetic layers.
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| 18. |
- Schütz, Christina, et al.
(författare)
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Hard and Transparent Films Formed by Nanocellulose-TiO2 Nanoparticle Hybrids
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:10, s. e45828-
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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.
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