| 1. |
- Allen, P. D., et al.
(författare)
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Low-frequency low-field magnetic susceptibility of ferritin and hemosiderin
- 2000
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Ingår i: Biochimica et Biophysica Acta - Molecular Basis of Disease. - 0925-4439 .- 1879-260X. ; 1500:2, s. 186-196
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Tidskriftsartikel (refereegranskat)abstract
- Low-frequency low-field magnetic susceptibility measurements were made on four samples of mammalian tissue iron oxide deposits. The samples comprised: (1) horse spleen ferritin; (') dugong liver hemosiderin; (3) thalassemic human spleen ferritin; and (4) crude thalassemic human spleen hemosiderin. These samples were chosen because Mossbauer spectroscopic measurements on the samples indicated that they exemplified the variation in magnetic and mineral structure found in mammalian tissue iron oxide deposits. The AC-magnetic susceptometry yielded information on the magnetization kinetics of the four samples indicating samples 1, 2, and 3 to be superparamagnetic with values of around 10(11) s(-1) for the preexponential frequency factor in the Neel-Arrhenius equation and values for characteristic magnetic anisotropy energy barriers in the range 250-400 K. Sample 4 was indicated to he paramagnetic at all temperatures above 1.3 K. The AC-magnetic susceptometry data also indicated a larger magnetic anisotropy energy distribution in the dugong liver sample compared with samples 1 and 3 in agreement with previous Mossbauer spectroscopic data on these samples. At temperatures below 200 K, samples 1-3 exhibited Curie-Weiss law behavior, indicating weak particle-particle interactions tending to favor antiparallel alignment of the particle magnetic moments. These interactions were strongest for the dugong liver hemosiderin. possibly reflecting the smaller separation between mineral particles in this sample. This is the first magnetic susceptometry study of hemosiderin iron deposits and demonstrates that the AC-magnetic susceptometry technique is a fast and informative method of studying such tissue iron oxide deposits.
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| 2. |
- Andersson, Richard L., et al.
(författare)
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Micromechanics of ultra-toughened electrospun PMMA/PEO fibres as revealed by in-situ tensile testing in an electron microscope
- 2014
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4, s. 6335-
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Tidskriftsartikel (refereegranskat)abstract
- A missing cornerstone in the development of tough micro/nano fibre systems is an understanding of the fibre failure mechanisms, which stems from the limitation in observing the fracture of objects with dimensions one hundredth of the width of a hair strand. Tensile testing in the electron microscope is herein adopted to reveal the fracture behaviour of a novel type of toughened electrospun poly(methyl methacrylate)/poly(ethylene oxide) fibre mats for biomedical applications. These fibres showed a toughness more than two orders of magnitude greater than that of pristine PMMA fibres. The in-situ microscopy revealed that the toughness were not only dependent on the initial molecular alignment after spinning, but also on the polymer formulation that could promote further molecular orientation during the formation of micro/nano-necking. The true fibre strength was greater than 150 MPa, which was considerably higher than that of the unmodified PMMA (17 MPa). This necking phenomenon was prohibited by high aspect ratio cellulose nanocrystal fillers in the ultra-tough fibres, leading to a decrease in toughness by more than one order of magnitude. The reported necking mechanism may have broad implications also within more traditional melt-spinning research.
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| 3. |
- Andersson, Richard, et al.
(författare)
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Superparamagnetic [sic] nanofibers by electrospinning
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:26, s. 21413-21422
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of superparamagnetic thin fibers by electrospinning dispersions of nanosized magnetite (Fe3O4, SPIO/USPIO) in a PMMA/PEO polymer solution is reported. The saturation magnetization and coercivity were not affected by the concentration (0, 1, 10, 20 wt%) or fiber orientation, showing hysteresis loops with high magnetization (64 A m(2) kg(-1) @ 500 kA m(-1)) and record low coercivity (20 A m(-1)). AC susceptibility measurements vs. temperature at frequencies from 60 to 2 kHz confirmed superparamagnetism. The mechanical properties were only slightly dependent on the particle concentration because the nanoparticles were separately encapsulated by the polymer. A uniform fibre fracture cross section was found at all the investigated particle contents, which suggests a strong interaction at the polymer/particle interface. A theoretical value of the magnetic low field susceptibility was calculated from the Langevin function and compared with measured values. The results show a distinct but concentration-independent anisotropy, favoring magnetization along the fiber orientation with no sign of exchange interaction, explained by complete nanoparticle separation. Superparamagnetism cannot be inferred from particle size alone, so a relevant interpretation and criterion for superparamagnetism is presented, in accordance with Neel's original definition. From the measurements, it can be concluded that magnetic characterization can be used to elucidate the material morphology beyond the resolution of available microscopy techniques (TEM and SEM).
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| 4. |
- Antonio, Capezza, et al.
(författare)
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Preparation and Comparison of Reduced Graphene Oxide and Carbon Nanotubes as Fillers in Conductive Natural Rubber for Flexible Electronics
- 2019
-
Ingår i: Omega. - : American Chemical Society (ACS). - 0030-2228 .- 1541-3764. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Conductive natural rubber (NR) nanocomposites were prepared by solvent-casting suspensions of reduced graphene oxide(rGO) or carbon nanotubes (CNTs), followed by vulcanization of the rubber composites. Both rGO and CNT were compatible as fillers in the NR as well as having sufficient intrinsic electrical conductivity for functional applications. Physical (thermal) and chemical reduction of GO were investigated, and the results of the reductions were monitored by X-ray photoelectron spectroscopy for establishing a reduction protocol that was useful for the rGO nanocomposite preparation. Field-emission scanning electron microscopy showed that both nanofillers were adequately dispersed in the main NR phase. The CNT composite displays a marked mechanical hysteresis and higher elongation at break, in comparison to the rGO composites for an equal fraction of the carbon phase. Moreover, the composite conductivity was always ca. 3-4 orders of magnitude higher for the CNT composite than for the rGO composites, the former reaching a maximum conductivity of ca. 10.5 S/m, which was explained by the more favorable geometry of the CNT versus the rGO sheets. For low current density applications though, both composites achieved the necessary percolation and showed the electrical conductivity needed for being applied as flexible conductors for a light-emitting diode.
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| 5. |
- Dahlberg, D, et al.
(författare)
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Measurements of the ferromagnetic/antiferromagnetic interfacial exchange energy in CO/CoO and Fe/FeF2 layers
- 1998
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 83:11, s. 6893-6895
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Tidskriftsartikel (refereegranskat)abstract
- Two measurement techniques, both relying on reversible rotations of the magnetization, have been used to determine the magnitude of the interfacial exchange energy (IEE) between ferromagnetic and antiferromagnetic (F/AF) layers. One technique is to use the anisotropic magnetoresistance to determine rotations of the magnetization away from the unidirectional easy axis, where the rotation is accomplished by applying external magnetic fields less than the effective F/AF exchange field. The second technique uses measurements of the ac susceptibility as a function of the angle between the ac field and the unidirectional exchange field. Both of the reversible process techniques result in values of the IEE larger (by as much as a factor of 10 in Co/CoO bilayers) than the traditional irreversible technique of measuring a shift in the hysteresis loop. The ac susceptibility technique was also used to measure one Fe/FeF2 bilayer. For this sample, the IEE values obtained by reversible and irreversible methods are equivalent.
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| 6. |
- Dastanpour, E., et al.
(författare)
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Crystallization behavior, soft magnetism and nanoindentation of Fe–Si–B–P–Cu alloy on Ni substitution
- 2021
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 851
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Tidskriftsartikel (refereegranskat)abstract
- The present work investigates how the substitution of Ni for Fe in the amorphous precursor of the high flux density Fe–Si–B–P–Cu (Nanomet®) alloy avoids the creation of detrimental pre-existing nuclei in the amorphous precursor as a step forward for improved amorphization capability, retains homogenous nanocrystalline structure with excellent soft magnetic properties, and affects the mechanical properties in terms of reduced hardness and Young's modulus. This has been achieved by adding Ni of various concentrations (0–8 atomic %). The investigation includes structural characterization, calorimetry, optimization of annealing temperature, extensive magnetic characterization and nanoindentation to assess the mechanical properties. The excellent soft magnetic properties demonstrate a strategy to deploy the nanocrystalline ribbons where freedom of device design is a limiting factor for electrodynamic energy conversion applications.
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| 7. |
- Dastanpour, Esmat, et al.
(författare)
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Non-isothermal nanocrystallization of Fe83.3Si4B8P4Cu0.7 (NANOMET (R)) alloy : modeling and the heating rate effect on magnetic properties
- 2020
-
Ingår i: Journal of Physics D. - : Institute of Physics Publishing (IOPP). - 0022-3727 .- 1361-6463. ; 53:21
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of the nanocrystallization of a Fe83.3Si4B8P4Cu0.7 amorphous alloy by using differential scanning calorimetry has been investigated by non-isothermal annealing in a wide heating rate range from 10 degrees C min(-1) to 200 degrees C min(-1). The amorphous alloy was prepared by melt-spinning and showed a two-stage crystallization. In the first crystallization stage, alpha-Fe nanocrystals are formed. This phase is responsible for the good soft magnetic properties. The activation energy during the crystallization of the alpha-Fe nanocrystalline phase was determined from an isoconversional approach, and was found to be distinctively varying during the crystallization. An attempt was made to model the crystallization in an interval where the activation energy is relatively constant. The Malek criterion indicated that the Kolmogorov-Johnson-Mehl-Avrami model is not appropriate, whereas the Sestak-Berggren model meets the criterion. The acquired model shows good agreement with the experimental results. The magnetic properties of annealed ribbons at different heating rates show an initially steep decrease of the coercivity (H-c) from 82 A m(-1) at a heating rate of 10 degrees C min(-1) to 20 A m(-1) above 100 degrees C min(-1), whereas saturation magnetization (M-s) is practically invariant at ca 175 Am-2 kg(-1). This dependence is explained as due to diminishing grain size with higher heating rates, which is further supported by x-ray diffraction measurements.
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| 8. |
- Dastanpour, E., et al.
(författare)
-
On the glass forming ability (GFA), crystallization behavior and soft magnetic properties of nanomet-substituted alloys
- 2020
-
Ingår i: Journal of Non-Crystalline Solids. - : ELSEVIER. - 0022-3093 .- 1873-4812. ; 529
-
Tidskriftsartikel (refereegranskat)abstract
- This study was aimed to investigate the effect of substitution of Fe with Co, C, and Mo on the glass forming ability (GFA), crystallization behavior, and magnetic properties of Fe-B-Si-P-Cu (Nanomet) alloy. The thermodynamic parameters, P-HS and P-HSS, were used to guide towards increased GFA. The P-HSS enhanced from -2.04 kJ/mol for Nanomet to -4.83 kJ/mol for a Co4C1Mo1 (at.%) substituted alloy. As a result, the critical quench rate reduced significantly, manifested as a drop of the required rotational speed from 3000 rpm to 2000 rpm. The temperature interval between two crystallization peaks enlarged for the substituted alloy, allowing a broader annealing range for nanocrystallization. The saturation magnetization (M-S) and the coercivity (H-C) were nearly maintained. This work confirms the relevance of the parameters P-HS and P-HSS to improve the GFA of the Nanomet alloy, and it is suggested that the same strategy can be applied for other alloys.
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| 9. |
- Dastanpour, Esmat, et al.
(författare)
-
Quantification of the anomalous crystallization and soft magnetic properties of Fe-Si-B-P-Cu (Nanomet) by isothermal calorimetry
- 2020
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 830
-
Tidskriftsartikel (refereegranskat)abstract
- The present study aimed to quantify the anomalous crystallization and soft magnetic properties of Fe-Si-B-P-Cu (Nanomet) alloy by isothermal calorimetry. The isothermal crystallization had slow kinetics at temperatures below the peak temperature of the exothermic event. The inhomogeneous distribution of pre-existing nuclei in the amorphous structure led to the anomalous crystallization, and hence, to a nonlinear Avrami plot with lowered localized Avrami exponents, attributed to temperature dependent crystallization kinetics. To the best of our knowledge, the presence of pre-existing magnetic nuclei was experimentally confirmed for the first time using ultra-high sensitive magneto-thermo-gravimetry (MTG). This is otherwise challenging, if not impossible, with conventional structural diffraction techniques. The incremental saturation magnetization (Ms) revealed how the volume fraction of the nanocrystallites intrinsically depends on both the annealing temperature and dwell time, and the significant change in the coercivity (He) confirmed the vital role the homogenous nucleation growth process has in order to achieve excellent soft magnetic properties.
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| 10. |
- Dastanpour Hosseinabadi, Esmat, et al.
(författare)
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An assessment of the Al50Cr21-xMn17+xCo12 (x=0, 4, 8) high-entropy alloys for magnetocaloric refrigeration application
- 2024
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 984
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the magnetocaloric potential of the Al50Cr21-xMn17+xCo12 (x=0, 4, 8 at%) high-entropy alloy (HEA) series using integrated experimental and theoretical approaches. Structural analysis by X-ray diffraction and scanning electron microscopy indicate a dual phase containing B2 and body-centered cubic (BCC) structures. Magnetic characterization shows an approximately linear decrease in saturation magnetization and Curie temperature with increasing Cr content. Curie temperatures calculated by Monte Carlo simulations suggest that the measured magnetic properties originate from the B2 phase rather than the BCC phase. The enhanced magnetocaloric effect with decreasing Cr content highlights the attractiveness of HEAs in magnetocaloric applications.
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| 11. |
- Dastanpour Hosseinabadi, Esmat, et al.
(författare)
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Investigation of the metastable spinodally decomposed magnetic CrFe-rich phase in Al doped CrFeCoNi alloy
- 2023
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 939
-
Tidskriftsartikel (refereegranskat)abstract
- We have conducted an in-depth study of the magnetic phase due to a spinodal decomposition of the BCC phase of a CrFe-rich composition. This magnetic phase is present after casting (arc melting) or water quenching after annealing at 1250 degrees C for 24 h but is entirely absent after annealing in the interval 900-1100 degrees C for 24 h. Its formation is favored in the temperature interval ca 450-550 degrees C and loses magnetization above 640 degrees C. This ferromagnetic-paramagnetic transition is due to a structural transformation from ferromagnetic BCC into paramagnetic sigma and FCC phases. The conclusion from measurements at different heating rates is that both the transformation leading to the increase of the magnetization due to the spinodal decomposition of the parent phase and the vanishing magnetization at 640 degrees C are diffusion controlled. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
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| 12. |
- Dastanpour Hosseinabadi, Esmat, et al.
(författare)
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Multi-alloying of nanomet : conception and implementation of homogeneous nanocrystallization in high-flux density soft magnetic alloys
- 2021
-
Ingår i: Journal of Materials Science. - : Springer. - 0022-2461 .- 1573-4803. ; 56:16, s. 10124-10134
-
Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates how multi-alloying the Fe-Si–B–P–Cu (Nanomet®) can avoid the strict requirements on the annealing scheme in terms of high heating rate and narrow annealing temperature range in order to grow a homogeneous ultrafine nanocrystalline structure. The rather restricted amorphization capability sets a low limit of the maximum thickness of the amorphous precursor. These shortcomings have their origin in the existence of detrimental pre-existing nuclei in the amorphous precursors, which in turn potentially lead to a heterogeneous crystallization. Here, we have multialloyed Nanomet with CoCNi- and CoCMo- to avoid the creation of these pre-existing nuclei. This leads to improved amorphization capability and changes a potentially heterogeneous crystallization to a homogeneous nanocrystallization over a much broader temperature range than for unalloyed Nanomet. Thus, the requirements for the annealing are much relaxed. This work encompasses quenching the amorphous precursors using melt-spinning, investigating the crystallization temperatures by calorimetry, showing the depletion of pre-existing nuclei by magneto-thermo-gravimetry, conceptualizing the crystallization dynamics using isothermal calorimetry, and finally revealing the excellent soft magnetic properties over a broad annealing temperature interval (390–490 °C for the substituted alloys compared to 410–470 °C for unalloyed Nanomet). The multi-elemental substitution of Fe with CoCMo and CoCNi in Nanomet alloy nearly maintains the saturation magnetization and the coercivity. We believe the substituted alloys provide a better alternative to Nanomet with improved amorphization capability and homogeneous nanocrystallization without any special heat treatment scheme. Graphical abstract: [Figure not available: see fulltext.]
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| 13. |
- Dastanpour Hosseinabadi, Esmat, et al.
(författare)
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On the structural and magnetic properties of Al-rich high entropy alloys : a joint experimental-theoretical study
- 2023
-
Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 56:1
-
Tidskriftsartikel (refereegranskat)abstract
- The present work investigates how the vanadium (V) content in a series of Al50V (x) (Cr0.33Mn0.33Co0.33)((50-x)) (x = 12.5, 6.5, 3.5, and 0.5 at.%) high-entropy alloys affects the local magnetic moment and magnetic transition temperature as a step towards developing high-entropy functional materials for magnetic refrigeration. This has been achieved by carrying out experimental investigations on induction melted alloys and comparison to ab initio and thermodynamic calculations. Structural characterization by x-ray diffraction and scanning electron microscopy indicates a dual-phase microstructure containing a disordered body-centered cubic (BCC) phase and a B2 phase with long-range order, which significantly differ in the Co and V contents. Ab initio calculations demonstrate a weaker magnetization and lower magnetic transition temperature (T
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| 14. |
- Dong, Zhihua, et al.
(författare)
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MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 high entropy alloys for magnetocaloric refrigeration near room temperature
- 2021
-
Ingår i: Journal of Materials Science & Technology. - : Chinese Society of Metals. - 1005-0302. ; 79, s. 15-20
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Tidskriftsartikel (refereegranskat)abstract
- High entropy alloys (HEAs) based on transition metals display rich magnetic characteristics, however attempts on their application in energy efficient technologies remain scarce. Here, we explore the magnetocaloric application for a series of MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 (0.8 < x < 1.1) HEAs by integrated theoretical and experimental methods. Both theory and experiment indicate the designed HEAs have the Curie temperature close to room temperature and is tunable with Mn concentration. A non-monotonic evolution is observed for both the entropy change and the relative cooling power with changing Mn concentration. The underlying atomic mechanism is found to primarily emerge from the complex impact of Mn on magnetism. Advanced magnetocaloric properties can be achieved by tuning Mn concentration in combination with controlling structural phase stability for the designed HEAs.
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| 15. |
- Fang, Mei, 1984-, et al.
(författare)
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Co-precipitation of iron oxide nanoparticles by rapid mixing
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Synthesis of Magnetite appears to be a topic of continued interest because of its versatility and the variety applications. Among the chemical techniques to synthesize Fe3O4, co-precipitation approach although very common, seems to be extremely sensitive to the consequences of nucleation, growth and most of all the rate of the reaction involved. This work is an attempt to demonstrate the complexities of obtaining monodispersed nanosized Fe3O4 particles. We consider the role of rapid mixing and its consequences on co-precipitation at ice-point, room temperature and boiling water temperatures on the magnetic properties of Fe3O4. We obtained crystallites varying in the range from 6.6 nm (grown in ice-water) to 7.9 nm (grown in boiling water) as determined from the broadening of XRD diffraction peaks using the Scherrer approach. With the increase of the particle size, the saturate magnetization of iron oxides increases from 52 emu/g to 63 emu/g, and the coercivity increases from 0.5 Oe to 7.9 Oe. Layers of nanosized magnetic particles on glass substrates show unusual wavelength dependence of Faraday rotation loops which show a reversal phenomenon in the sign of the magnetization around 550.
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| 16. |
- Fang, Mei, et al.
(författare)
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Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:14, s. 145601-
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Tidskriftsartikel (refereegranskat)abstract
- Magnetite nanoparticles have been prepared by co-precipitation using a custom-designed jet mixer to achieve rapid mixing (RM) of reactants in a timescale of milliseconds. The quick and stable nucleation obtained allows control of the particle size and size distribution via a more defined growth process. Nanoparticles of different sizes were prepared by controlling the processing temperature in the first few seconds post-mixing. The average size of the nanoparticles investigated using a Tecnai transmission electron microscope is found to increase with the temperature from 3.8 nm at 1 +/- 1 degrees C to 10.9 nm for particles grown at 95 +/- 1 degrees C. The temperature dependence of the size distribution follows the same trend and is explained in terms of Ostwald ripening of the magnetite nanoparticles during the co-precipitation of Fe2+ and Fe3+. The magnetic properties were studied by monitoring the blocking temperature via both DC and AC techniques. Strikingly, the obtained RM particles maintain the high magnetization (as high as similar to 88 A m(2) kg(-1) at 500 kA m(-1)) while the coercivity is as low as similar to 12 A m(-1) with the expected temperature dependence. Besides, by adding a drop of tetramethylammonium hydroxide, aqueous ferrofluids with long term stability are obtained, suggesting their suitability for applications in ferrofluid technology and biomedicine.
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| 17. |
- Fang, Mei, et al.
(författare)
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Rapid mixing : A route to synthesize magnetite nanoparticles with high moment
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 99:22, s. 222501-
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the impact of rapid mixing of the precursors in a time scale of milliseconds on the reaction rate and magnetic properties of co-precipitated magnetite with a custom-made mixer. The mixed volume is directed into a desk-top AC susceptometer to monitor the magnetic response from the growing particles in real-time. These measurements indicate that the reaction is mostly completed within a minute. The obtained superparamagnetic nanoparticles exhibit a narrow size distribution and large magnetization (87 Am(2) kg(-1)). Transmission electron micrographs suggest that rapid mixing is the key for better crystallinity and a more uniform morphology leading to the observed magnetization values.
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| 18. |
- Galland, Sylvain, 1987-, et al.
(författare)
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Cellulose nanofibers decorated with magnetic nanoparticles : synthesis, structure and use in magnetized high toughness membranes for a prototype loudspeaker
- 2013
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Ingår i: Journal of Materials Chemistry C. - 2050-7526. ; 1:47, s. 7963-7972
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic nanoparticles are the functional component for magnetic membranes, but they are difficult to disperse and process into tough membranes. Here, cellulose nanofibers are decorated with magnetic ferrite nanoparticles formed in situ which ensures a uniform particle distribution, thereby avoiding the traditional mixing stage with the potential risk of particle agglomeration. The attachment of the particles to the nanofibrils is achieved via aqueous in situ hydrolysis of metal precursors onto the fibrils at temperatures below 100 °C. Metal adsorption and precursor quantification were carried out using Induction Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). FE-SEM was used for high resolution characterization of the decorated nanofibers and hybrid membranes, and TEM was used for nanoparticle size distribution studies. The decorated nanofibers form a hydrocolloid. Large (200 mm diameter) hybrid cellulose/ferrite membranes were prepared by simple filtration and drying of the colloidal suspension. The low-density, flexible and permanently magnetized membranes contain as much as 60 wt% uniformly dispersed nanoparticles (thermogravimetric analysis data). Hysteresis magnetization was measured by a Vibrating Sample Magnetometer; the inorganic phase was characterized by XRD. Membrane mechanical properties were measured in uniaxial tension. An ultrathin prototype loudspeaker was made and its acoustic performance in terms of output sound pressure was characterized. A full spectrum of audible frequencies was resolved.
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| 19. |
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| 20. |
- Galland, Sylvain, 1987-, et al.
(författare)
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Strong and Moldable Cellulose Magnets with High Ferrite Nanoparticle Content
- 2014
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 6:22, s. 20524-20534
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Tidskriftsartikel (refereegranskat)abstract
- A major limitation in the development of highly functional hybrid nanocomposites is brittleness and low tensile strength at high inorganic nanoparticle content. Herein, cellulose nanofibers were extracted from wood and individually decorated with cobalt-ferrite nanoparticles and then for the first time molded at low temperature (<120 degrees C) into magnetic nanocomposites with up to 93 wt % inorganic content. The material structure was characterized by TEM and FE-SEM and mechanically tested as compression molded samples. The obtained porous magnetic sheets were further impregnated with a thermosetting epoxy resin, which improved the load-bearing functions of ferrite and cellulose material. A nanocomposite with 70 wt % ferrite, 20 wt % cellulose nanofibers, and 10 wt % epoxy showed a modulus of 12.6 GPa, a tensile strength of 97 MPa, and a strain at failure of ca. 4%. Magnetic characterization was performed in a vibrating sample magnetometer, which showed that the coercivity was unaffected and that the saturation magnetization was in proportion with the ferrite content. The used ferrite, CoFe2O4 is a magnetically hard material, demonstrated by that the composite material behaved as a traditional permanent magnet. The presented processing route is easily adaptable to prepare millimeter-thick and moldable magnetic objects. This suggests that the processing method has the potential to be scaled-up for industrial use for the preparation of a new subcategory of magnetic, low-cost, and moldable objects based on cellulose nanofibers.
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| 21. |
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| 22. |
- Guex, Leonard Gaston, et al.
(författare)
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Experimental review : chemical reduction of graphene oxide (GO) to reduced graphene oxide (rGO) by aqueous chemistry
- 2017
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 9:27, s. 9562-9571
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Forskningsöversikt (refereegranskat)abstract
- The electrical conductivity of reduced graphene oxide (rGO) obtained from graphene oxide (GO) using sodium borohydride (NaBH4) as a reducing agent has been investigated as a function of time (2 min to 24 h) and temperature (20 degrees C to 80 degrees C). Using a 300 mM aqueous NaBH4 solution at 80 degrees C, reduction of GO occurred to a large extent during the first 10 min, which yielded a conductivity increase of 5 orders of magnitude to 10 S m(-1). During the residual 1400 min of reaction, the reduction rate decreased significantly, eventually resulting in a rGO conductivity of 1500 S m(-1). High resolution XPS measurements showed that C/O increased from 2.2 for the GO to 6.9 for the rGO at the longest reaction times, due to the elimination of oxygen. The steep increase in conductivity recorded during the first 8-12 min of reaction was mainly due to the reduction of C-O (e.g., hydroxyl and epoxy) groups, suggesting the preferential attack of the reducing agent on C-O rather than C=O groups. In addition, the specular variation of the percentage content of C-O bond functionalities with the sum of Csp(2) and Csp(3) indicated that the reduction of epoxy or hydroxyl groups had a greater impact on the restoration of the conductive nature of the graphite structure in rGO. These findings were reflected in the dramatic change in the structural stability of the rGO nanofoams produced by freeze-drying. The reduction protocol in this study allowed to achieve the highest conductivity values reported so far for the aqueous reduction of graphene oxide mediated by sodium borohydride. The 4-probe sheet resistivity approach used to measure the electrical conductivity is also, for the first time, presented in detail for filtrate sheet assemblies' of stacked GO/rGO sheets.
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| 23. |
- Hoogendoorn, Billy W., et al.
(författare)
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Cellulose nanofibers (CNFs) in the recycling of nickel and cadmium battery metals using electrodeposition
- 2023
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 5:19, s. 5263-5275
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibers (CNFs) were employed in the aqueous electrodeposition of nickel and cadmium for battery metal recycling. The electrowinning of mixed Ni-Cd metal ion recycling solutions demonstrated that cadmium with a purity of over 99% could be selectively extracted while leaving the nickel in the solution. Two types of CNFs were evaluated: negatively charged CNFs (a-CNF) obtained through acid hydrolysis (−75 μeq. g−1) and positively charged CNFs (q-CNF) functionalized with quaternary ammonium groups (+85 μeq. g−1). The inclusion of CNFs in the Ni-Cd electrolytes induced growth of cm-sized dendrites in conditions where dendrites were otherwise not observed, or increased the degree of dendritic growth when it was already present to a lesser extent. The augmented dendritic growth correlated with an increase in deposition yields of up to 30%. Additionally, it facilitated the formation of easily detachable dendritic structures, enabling more efficient processing on a large scale and enhancing the recovery of the toxic cadmium metal. Regardless of the charged nature of the CNFs, both negatively and positively charged CNFs led to a significant formation of protruding cadmium dendrites. When deposited separately, dendritic growth and increased deposition yields remained consistent for the cadmium metal. However, dendrites were not observed during the deposition of nickel; instead, uniformly deposited layers were formed, albeit at lower yields (20%), when positively charged CNFs were present. This paper explores the potential of utilizing cellulose and its derivatives as the world's largest biomass resource to enhance battery metal recycling processes.
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| 24. |
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| 25. |
- Hoogendoorn, Billy W., et al.
(författare)
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Ultra-low Concentration of Cellulose Nanofibers (CNFs) for Enhanced Nucleation and Yield of ZnO Nanoparticles
- 2022
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 38:41, s. 12480-12490
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibers (CNFs) were used in aqueous synthesis protocols for zinc oxide (ZnO) to affect the formation of the ZnO particles. Different concentrations of CNFs were evaluated in two different synthesis protocols producing distinctly different ZnO morphologies (flowers and sea urchins) as either dominantly oxygen-or zinc-terminated particles. The CNF effects on the ZnO formation were investigated by implementing a heat-treatment method at 400 degrees C that fully removed the cellulose material without affecting the ZnO particles made in the presence of CNFs. The inorganic phase formations were monitored by extracting samples during the enforced precipitations to observe changes in the ZnO morphologies. A decrease in the size of the ZnO particles could be observed for all synthesis protocols, already occurring at small additions of CNFs. At as low as 0.1 g/L CNFs, the particle size decreased by 50% for the flower-shaped particles and 45% for the sea-urchin-shaped particles. The formation of smaller particles was accompanied by increased yield by 13 and 15% due to the CNFs' ability to enhance the nucleation, resulting in greater mass of ZnO divided among a larger number of particles. The enhanced nucleation could also be verified as useful for preventing secondary morphologies from forming, which grew on the firstly precipitated particles. The suppression of secondary growths' was due to the more rapid inorganic phase formation during the early phases of the reactions and the faster consumption of dissolved salts, leaving smaller amounts of metal salts present at later stages of the reactions. The findings show that using cellulose to guide inorganic nanoparticle growth can be predicted as an emerging field in the preparation of functional inorganic micro/nanoparticles. The observations are highly relevant in any industrial setting for the large-scale and resource-efficient production of ZnO.
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