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Using a modified co-precipitation method, 11(2) nm γ-Fe2O3 nanoparticles functionalized with PSSNa [Poly(sodium 4-styrenesulfonate)] saloplastic polymer were successfully synthesized, and their structural, vibrational, electronic, thermal, colloidal, hyperfine, and magnetic properties were systematically studied using various analytic techniques. The results showed that the functionalized γ-Fe2O3/PSSNa nanohybrid has physicochemical properties that allow it to be applied in the magnetic remediation process of water. Before being applied as a nanoadsorbent in real water treatment, a short-term acute assay was developed and standardized using a Daphnia magna biomarker. The ecotoxicological tests indicated that the different concentrations of the functionalized nanohybrid may affect the mortality of the Daphnia magna population during the first 24 h of exposure. A lethal concentration of 533(5) mg L−1 was found. At high concentrations, morphological changes were also seen in the body, heart, and antenna. Therefore, these results suggested the presence of alterations in normal growth and swimming skills. The main changes observed in the D. magna features were basically caused by the PSSNa polymer due to its highly stable colloidal properties (zeta potential > −30 mV) that permit a direct and constant interaction with the Daphnia magna neonates. [ABSTRACT FROM AUTHOR]

Using a modified co-precipitation method, 11(2) nm γ-Fe2O3 nanoparticles functionalized with PSSNa [Poly(sodium 4-styrenesulfonate)] saloplastic polymer were successfully synthesized, and their structural, vibrational, electronic, thermal, colloidal, hyperfine, and magnetic properties were systematically studied using various analytic techniques. The results showed that the functionalized γ-Fe2O3/PSSNa nanohybrid has physicochemical properties that allow it to be applied in the magnetic remediation process of water. Before being applied as a nanoadsorbent in real water treatment, a short-term acute assay was developed and standardized using a Daphnia magna biomarker. The ecotoxicological tests indicated that the different concentrations of the functionalized nanohybrid may affect the mortality of the Daphnia magna population during the first 24 h of exposure. A lethal concentration of 533(5) mg L−1 was found. At high concentrations, morphological changes were also seen in the body, heart, and antenna. Therefore, these results suggested the presence of alterations in normal growth and swimming skills. The main changes observed in the D. magna features were basically caused by the PSSNa polymer due to its highly stable colloidal properties (zeta potential > −30 mV) that permit a direct and constant interaction with the Daphnia magna neonates.

We have studied the structural and magnetic properties of maghemite submicron particles and their arsenic adsorption properties. The chemical method for the synthesis of these novel submicron particles consisted of the thermally activated partial oxidation and solid phase transformations of magnetite particles. The crystallographic structure of the synthesized particles prepared at different time intervals of thermal treatment (10 min, 30 min, 60 min, and 90 min) was characterized using powder X-ray diffraction and Rietveld refinement. Moreover, the magnetic properties were examined using a conventional 57Fe Mössbauer spectrometer and an alternating gradient magnetometer applying a field of ± 12 kOe at room temperature. The concentration of arsenic was determined, before and after removal experiments, by inductively coupled plasma-atomic emission spectroscopy. The results showed that the submicron particles synthesized by this method exhibit a cubic inverse spinel structure with a particle size distribution in the range of 80–170 nm. According to Mössbauer spectrometry, the particles are composed of a magnetically ordered core and a disordered surface region. Room temperature magnetization curves confirmed an interacting weakly ferrimagnetic behavior with saturation magnetization of 60 emu g− 1 and coercive field of 60 Oe. Additionally, the submicron particles are capable of efficiently decreasing the arsenic(V) content in water from 100 µg/L to below 10 µg/L (the current recommended limit of arsenic in drinking water according to the World Health Organization guideline) and it can be recycled by the application of an external magnetic field. [ABSTRACT FROM AUTHOR]

We have studied the structural and magnetic properties of maghemite submicron particles and their arsenic adsorption properties. The chemical method for the synthesis of these novel submicron particles consisted of the thermally activated partial oxidation and solid phase transformations of magnetite particles. The crystallographic structure of the synthesized particles prepared at different time intervals of thermal treatment (10 min, 30 min, 60 min, and 90 min) was characterized using powder X-ray diffraction and Rietveld refinement. Moreover, the magnetic properties were examined using a conventional 57Fe Mössbauer spectrometer and an alternating gradient magnetometer applying a field of ± 12 kOe at room temperature. The concentration of arsenic was determined, before and after removal experiments, by inductively coupled plasma-atomic emission spectroscopy. The results showed that the submicron particles synthesized by this method exhibit a cubic inverse spinel structure with a particle size distribution in the range of 80–170 nm. According to Mössbauer spectrometry, the particles are composed of a magnetically ordered core and a disordered surface region. Room temperature magnetization curves confirmed an interacting weakly ferrimagnetic behavior with saturation magnetization of 60 emu g− 1 and coercive field of 60 Oe. Additionally, the submicron particles are capable of efficiently decreasing the arsenic(V) content in water from 100 µg/L to below 10 µg/L (the current recommended limit of arsenic in drinking water according to the World Health Organization guideline) and it can be recycled by the application of an external magnetic field. [ABSTRACT FROM AUTHOR]

We report the effect of a polyol-mediated annealing on nickel ferrite nanoparticles. By combining X-ray fluorescence spectroscopy, X-ray diffraction, and 57Fe Mössbauer spectrometry, we showed that whereas the as-prepared nanoparticles (NFO) are stoichiometric, the annealed ones (a-NFO) are not, since Ni0-based crystals precipitate. Nickel depletion from the spinel lattice and reduction in the polyol solvent are accompanied with an important cation migration. Indeed, thanks to Mössbauer hyperfine structure analysis, we evidenced that the cation distribution in NFO departs from the thermodynamically stable inverse spinel structure with a concentration of tetrahedrally coordinated Ni2+ of 20 wt-% (A sites). After annealing, and nickel demixing, originated very probably from the A sites of NFO lattice, the spinel phase accommodates with cation and anion vacancies, leading to the (Fe3+0.84□0.16)A[Ni2+0.80Fe3+1.16□0.04]BO4-0.20 formula, meaning that the applied polyol-mediated treatment is not so trivial.

A new source of clay mineral was explored and an extraction and purification protocol was developed to isolate it from raw clay samples acquired in the Oued Ziz region of southeastern Morocco. Clay minerals are always identified in the raw clay or soil by a purification step, as the presence of carbonates, iron oxides or organic matter interferes with the identification process. Purification is also necessary to study the properties of clay minerals. The process involved the collection of raw clay from the source, as well as mineralogical, and physicochemical characterizations. Characterization of the prepared materials was done using X-ray diffraction spectrometry (XRD) which makes it possible to determine the structure and nature of clay. The basic chemical analysis of the materials was carried out by X-ray fluorescence (XRF) and inductively coupled plasma—Atomic emission spectroscopy (ICP-AES). Moreover, Energy dispersive X-ray analysis (EDX) and Fourier transform-infrared spectroscopy (FT-IR Spectroscopy) were used to investigate the chemical composition or nature of minerals. The morphology of the clay samples is unveiled by scanning electron microscopy (SEM), thus thermal analysis (TGA-DTA) records the sample mass loss caused by thermal transformations such as dehydration or calcination for clay minerals. 57Fe Mössbauer spectrometry was also used to investigate the presence of iron in clay samples. [ABSTRACT FROM AUTHOR]

A simple one-pot synthesis was utilized to prepare Mn-doped maghemite nanoparticles. A homogenized mixture of Mn- and Fe-acetylacetonates was heated in air atmosphere at 300 °C to produce Mn-doped maghemite. XRD showed only the presence of a spinel crystal structure with a linear increase of the unit-cell volume up to 20 mol% of the Mn dopant. Possible structural changes with increased Mn doping are briefly discussed.57Fe Mössbauer spectra recorded at 77 K were fitted with two sextets of lines corresponding to Fe3+ ions at A-tetrahedral and B-octahedral sites in maghemite. FE SEM images showed that Mn-doped maghemite nanoparticles were of good uniformity, with the crystallite size varying from 24 to 35 nm, as determined by XRD. [ABSTRACT FROM AUTHOR]

The objective of this work was to study the influence of annealing temperature on the structural changes and magnetic properties of the Ni0.5Zn0.5Fe2O4 spinel-type nanoparticles. The nanomaterial was prepared by the chemical co-precipitation method and studied by thermal analysis (TG–DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), magnetic measurements and 57Fe Mössbauer spectrometry. XRD has revealed that the as-prepared sample shows poor crystallization with less defined diffraction lines. As the annealing temperature increases, the diffraction peaks become intense and well defined, reflecting perfect crystallization of the sample. The estimated crystallite size varies from 25 to 83 nm. TEM observations give information on the morphology and confirm the XRD results. To quantify the proportions of the iron atoms in the tetrahedral and octahedral sites, in-field Mössbauer spectrometry measurements were carried out at low temperature. Saturation magnetization (Ms) and the average hyperfine magnetic field B hf increase gradually with annealing temperature. For the sample annealed at 1000 °C, the magnetic entropy change Δ S M max and relative cooling power, measured under field change of 2T, are 0.67 J kg−1 K−1 and 112.5 J kg−1, respectively. [ABSTRACT FROM AUTHOR]

We combine powder neutron diffraction, magnetometry and 57Fe Mössbauer spectrometry to determine the nuclear and magnetic structures of a strongly interacting weberite-type inorganic-organic hybrid fluoride, Fe2F5(Htaz). In this structure, Fe2+ and Fe3+ cations form magnetically frustrated hexagonal tungsten bronze layers of corner-sharing octahedra. Our powder neutron diffraction data reveal that, unlike its purely inorganic fluoride weberite counterparts which adopt a centrosymmetric Imma structure, the room-temperature nuclear structure of Fe2F5(Htaz) is best described by a non-centrosymmetric Ima2 model with refined lattice parameters a=9.1467(2) Å, b=9.4641(2)Å and c=7.4829(2) Å. Magnetic susceptibility and magnetization measurements reveal that strong antiferromagnetic exchange interactions prevail in Fe2F5(Htaz) leading to a magnetic ordering transition at TN =93 K. Analysis of low-temperature powder neutron diffraction data indicates that below TN, the Fe2+ sublattice is ferromagnetic, with a moment of 4.1(1) ƒÊB per Fe2+ at 2K, but that an antiferromagnetic component of 0.6(3) ƒÊB cants the main ferromagnetic component of Fe3+, which aligns antiferromagnetically to the Fe2+ sublattice. The zero-field and in-field Mossbauer spectra give clear evidence of an excess of high-spin Fe3+ species within the structure and a non-collinear magnetic structure. [ABSTRACT FROM AUTHOR]

Highlights • 57Fe Mössbauer spectrometry was employed to investigate the hyperfine structure of the alloy. • The largest coercivity of 31.9 kOe was obtained in the Nd 60 Fe 30 Al 10 alloy at 50 K. • Exchange bias was observed in the M−H loops measured at 5 K for the alloy after field cooling. Abstract Magnetic characteristics of the ferromagnetic Fe-rich clusters is the key to exploring the hard magnetism of bulk amorphous Nd-Fe-Al alloys, which has not been fully understood yet. In this work, Φ 2 mm Nd 60 Fe 30 Al 30 rod sample was prepared by copper mold casting method. Based on the detailed microstructure analysis, the alloy is actually composed of main amorphous phase and Hcp structured nanocrystalline Nd phase. 57Fe Mössbauer spectrometry was employed to investigate the hyperfine structure of the alloy. Based on the refined hyperfine parameters, the distribution of the hyperfine field of the Fe-rich clusters suggests the typical amorphous structure of those clusters. The M−H loops measured at 5 K for the alloy after field cooling shifts upwards compared with that without field cooling. The reason could be attributed to the fact that parts of the clusters' moments are blocked by the strong pinning effects of antiferromagnetic coupled Nd atoms, which is difficult to be reoriented under an available applied magnetic field. The present data provides some useful information for understanding the ferromagnetic Fe-rich clusters in Nd 60 Fe 30 Al 10 alloy. [ABSTRACT FROM AUTHOR]

• τ-Mn 50.5 Fe 0.5 Al 47 C 2 showed a complex magnetic hyperfine splitting. • The hyperfine interaction of τ-Mn 50.5 Fe 0.5 Al 47 C 2 was temperature dependent. • The Curie temperature (T c) was identified to lie at 565 K ± 2 K. • Fe and Mn formed a non-collinear magnetic structure. • µ Fe at different sites showed different canting angles with neighboring Mn atoms. Four samples γ 2 -Mn 40 Fe 0.5 Al 59.5 , β-Mn 60 Fe 0.5 Al 39.5 , and ε-Mn 50.5 Fe 0.5 Al 47 C 2 , τ-Mn 50.5 Fe 0.5 Al 47 C 2 were synthesized by mechanical alloying method. X-ray diffraction results showed high purity of the γ 2 , β, ε, and τ phases in each sample. Mössbauer measurement at room temperature showed non-ferromagnetic characteristic of the γ 2 -Mn 40 Fe 0.5 Al 59.5 , β-Mn 60 Fe 0.5 Al 39.5 , and ε-Mn 50.5 Fe 0.5 Al 47 C 2. Interestingly, τ -Mn 50.5 Fe 0.5 Al 47 C 2 showed a complex magnetic hyperfine splitting, indicating magnetic ordered structure. The hyperfine interaction in τ -Mn 50.5 Fe 0.5 Al 47 C 2 was found dependent with temperature, in which isomer shift (IS) and magnetic hyperfine field (B hf) decreased with increasing temperature. From the IS temperature dependence curve, the Debye temperature (θ D) is determined to be 422 ± 80 K. The temperature dependence of B hf values and the thermomagnetic measurement yielded a Curie temperature (T c) values of 560 ± 13 K and 565 ± 2 K respectively. In order to investigate the magnetic interaction between Fe and Mn atoms in τ -Mn 50.5 Fe 0.5 Al 47 C 2 , local magnetic order of τ -Mn 50.5 Fe 0.5 Al 47 C 2 was probed by using in-field 57Fe Mössbauer spectrometry. The obtained results showed that Fe and Mn formed a non-collinear magnetic structure with magnetic moments of Fe at different sites showing different canting angles with neighboring Mn atoms. [ABSTRACT FROM AUTHOR]

Ni 1- x Zn x Fe 2 O 4 (0 ≤ x ≤ 1) nanoparticles were synthesized via co-precipitation method in order to study their structural and magnetic properties as well as their heating efficiency. Structural results show that the annealed samples at 1000 °C exhibit a single cubic spinel structure while the mean crystallites size is ranging from 70 to 130 nm, as x increases. Rietveld refinement was also performed to deduce both cation distribution and lattice parameter. Mössbauer spectroscopy at room temperature shows the decrease of the average hyperfine field with the increase of the zinc content. Magnetic curves indicate that saturation magnetization was increased with the increase of zinc concentration, up to x = 0.5, then decreased. These results have been explored to explain the magnetic heating characteristics of the samples under an AC magnetic field at a fixed frequency. The intrinsic loss power (ILP) of sample with x = 0.5 is found about 0.42 nH m2kg-1, this value allows the use of x = 0.5 for the in-situ hyperthermia treatment of cancer cells as application. • Ni 1-x Zn x Fe 2 O 4 nanoparticles were successfully synthesized by co-precipitation method. • Average crystallite size is in the range of 70 and 130 nm. • Magnetic properties were studied through Mössbauer and SQUID measurements. • Law approach to saturation is used to study the dependency of magnetization on the applied field. • Highest ILP value was 0.42 nH m2 kg-1, obtained for the sample with x = 0.5. [ABSTRACT FROM AUTHOR]

Abstract: Powders of melted disordered Fe50Mn10Al40 alloy were separated at different mean particle sizes as well as magnetically and structurally characterized. All the samples are BCC and show the same nanostructure. Particles larger than 250μm showed a lamellar shape compared to smaller particles, which exhibited a more regular form. All the samples are ferromagnetic at room temperature and showed reentrant spin-glass (RSG) and superparamagnetic (SP)-like behaviors between 30 and 60K and 265 and > 280K, respectively, as a function of frequency and particle size. The freezing temperature increases with increasing particle size while the blocking one decreases with particle size. The origin of these magnetic phenomena relies in the internal disordered character of samples and the competitive interaction of Fe and Mn atoms. The increase of their critical freezing temperature with increasing mean particle size is due to the increase of the magnetic dipolar interaction between the magnetic moment of each particle with the field produced by the other magnetic moments of their surrounding particles. [Copyright &y& Elsevier]

Abstract: The formation mechanism of the mechanically alloyed Fe–20at% Al, from elemental Fe and Al powders, has been investigated. The experimental results indicate the formation of a nanocrystalline bcc α-Fe(Al) solid solution with a lattice parameter close to a α−Fe(Al)=0.2890nm, where each Fe atom is surrounded by (6Fe+2Al) in the first coordination sphere. The reaction mechanism of MA process seems to be controlled by a diffusion phenomenon. Aluminum particles undergo an important refinement to the nanometer scale and then they stick on Fe particles of large sizes. A large number of clear Al/Fe interface areas were generated. The short diffusion path and the presence of high concentration of defects accelerated the solid state reaction. [Copyright &y& Elsevier]

Abstract: In the present paper, we discuss the local atomic environment of Fe atoms in the mechanically alloyed Fe50Al40Ni10 powders on the basis of hyperfine data estimated from 57Fe Mössbauer spectra. B hf decreases with increasing milling time due to the diffusion of Al and/or Ni into Fe grains. Nickel atoms did not diffuse inside the first coordination sphere of Fe and if the diffusion takes place the number is not more than one atom. Analyses of P(B hf), indicate that the high hyperfine field values ranging from 30 to 33T have to be partially attributed to Fe crystalline nanograins and the presence of the defects in them, the hyperfine field values ranging from 15 to 30T can be associated to the nanocrystalline bcc Fe(Al, Ni) solid solution while the low hyperfine field values (<15T) result from Fe atoms located in the disordered grain boundaries. [Copyright &y& Elsevier]

Abstract: A new family of MIEC compounds resulting from the electrolyte BaIn0.3Ti0.7O2.85 (BIT07) was developed by coupled substitution of titanium by iron and barium by lanthanum. Total conductivity increases significantly with iron and lanthanum content. BaIn0.3Ti0.7O2.85 yields a total conductivity in air of 10−2 Scm−1 at 700°C whereas that of Ba0.7La0.3In0.3Ti0.1Fe0.6O3−δ (BLITFe06) is 3Scm−1. Doped compounds are p-type conductors. In reducing atmosphere the electrical conductivity decreases drastically to σ =2×10−2 Scm−1 for the best value, which is not sufficient for a use as MIEC anode. Nevertheless, Ni/BLITFe06 cermets seem to be good candidates as SOFC anodes. The total conductivity of Ni/BLITFe cermets is higher than that of 18.7vol.% Ni/BIT07 (σ 700 °C ≈102 Scm−1), even for a lower Ni content (16.1vol.% Ni/BLITFe σ 700°C ≈200Scm−1). The percolation threshold moves towards the small quantities of nickel (from 15.7vol.% to 10vol.%). Ni/BLITFe06 cermets, compared with Ni/BIT07, show a better electrochemical behaviour towards fuel oxidation. [Copyright &y& Elsevier]

Abstract: FeSi10Cr10 powder was mechanically alloyed by high energy planetary ball milling, starting from elemental powders. The microstructural and magnetic properties of the milled powders were characterized by scanning electron microscopy, X-ray diffraction, 57Fe Mössbauer spectrometry and a vibratory sample magnetometer. After 3h of milling, the formation of two bcc solid solutions α-Fe1 (Si, Cr) and α-Fe2 (Si, Cr) is observed. Their grain sizes decrease with increase in milling time attaining, at 15h of milling, 23 and 11nm, respectively. Mössbauer spectra of the milled powder show the presence of two components. One is a ferromagnetic type with a broad sextuplet. Its distribution of hyperfine field is characterized by high and low hyperfine field’s peaks and a mean value of 26.5T. The other is a single paramagnetic peak. Its low concentration increases to ∼4% at 15h of milling. These results can be explained by different atomic environments affected by Si or/and Cr elements, as well as the increased disordered grain boundaries. Magnetic measurements of the milled FeSi10Cr10 alloy powder exhibit a soft ferromagnetic character with a decrease of both magnetization at saturation (Ms) and coercive force (Hc) with milling time attaining values of Ms=151emu/g and Hc=2500A/m at 30h of milling time. [Copyright &y& Elsevier]

Abstract: The hydrothermal synthesis, using tris-(2-ethylamino)amine (tren) as a template, and the crystal structures of three new hybrid iron fluorides, (H3O)2·[H3 tren]2·(FeF6)2·(FeF5(H2O))·2H2O (I), [H3 tren]2·(FeF6)2·(FeF2(H2O)4)·8H2O (II) and [H3 tren]2·(FeF6)·(F)3·H2O (III), are reported. I, II, and III are triclinic (P-1), monoclinic (P21/c) and orthorhombic (I222), respectively. The structure of I is built up from isolated FeF6 and FeF5(H2O) distorted octahedra separated by triprotonated [H3 tren]3+ cations, disordered H3O+ cations and H2O molecules. In II, FeIIIF6 and neutral [FeIIF2(H2O)4] octahedra form, together with [H3 tren]3+ cations, infinite (100) layers separated by extra water molecules. The structure of III consists of isolated and disordered FeF6 octahedra, fluoride anions F− connected to [H3 tren]3+ cations and extra fluoride anions F− disordered with H2O molecules. All [H3 tren]3+ cations have a “spider” type conformation. 57Fe Mössbauer characterization shows that +III valence state can only be considered for iron cations in I and III and preliminary Mössbauer results are consistent with the presence of both +II and +III valences for iron cations in II, in agreement with the crystallographic results. [Copyright &y& Elsevier]

Abstract: Fe–20wt.% Ni alloys were prepared using a planetary ball mill PM 400 from Retsch (with different milling times for Ω =400rpm, ω =800rpm) and P4 vario ball mill from Fritsch (with different milling conditions (Ω/ω), Ω and ω being the disc and the vial rotation speeds, respectively). The bcc-Fe(Ni) phase formation is identified by X-ray diffraction. The higher the shock power and the higher milling time are, the larger the bcc lattice parameter and the lower the grain size. The highest value of the coercive field is 1420A/m for Fe–20wt.% Ni (with shock mode (424rpm/100rpm) after 36h of milling), while the lowest value is 110A/m for (400rpm/800rpm) after 96h of milling. The milling performed in the friction mode favors the formation of alloys exhibiting a soft magnetic behavior for Fe–20wt.% Ni alloys. The Mössbauer spectra of the alloys recorded at 77 and at 300K differ according to the milling conditions and give relevant information on the local structure environment in relation with the nature of the mode used (friction or shock mode). [Copyright &y& Elsevier]

Fe60Mn10Al20Nb10, (Fe60Mn10Al30)95Nb5 and (Fe60Mn10Al30)90Nb10 ball milled powdered alloys were investigated using X-ray diffraction, Mössbauer spectrometry, thermomagnetic (TGM) and magnetization measurements. We studied the influence of Nb content and of different milling times on the structural and magnetic properties. Two main features can be concluded: (1) the FeAlMn induces a BCC phase whatever the Nb content is, and (2) as both increasing Nb content and milling time give rise to an highly disordered state in conjunction with a decrease of the ferromagnetic behavior. [ABSTRACT FROM AUTHOR]

We propose a method to describe accurately Mössbauer spectra recorded on nanocrystalline FINEMET-type alloys by means of two independent components. The validity of the fitting procedure is controlled by comparing hyperfine characteristics of spectra recorded under different experimental configurations. In addition, the reliability of the fitting model is discussed from spectra obtained on nanocrystalline alloys resulting from different annealing treatments, i.e., with different crystalline contents. Such a method allows us to estimate more accurately the crystalline fraction and to refine the values of hyperfine parameters, both their annealing temperature and time dependencies, the hyperfine field distribution characteristic of the intergranular component and the magnetic texture. Finally, their changes versus crystalline fraction provide relevant information to describe the nanocrystallization process occurring during the transformation from the amorphous into the nanocrystalline state in the case of FINEMET alloys. [ABSTRACT FROM AUTHOR]

Soft magnetic nanocrystalline alloys have attracted great fundamental interest in recent years due to their two-phase structural and magnetic behaviour. We review first the reliability of the fitting procedures of spectra obtained by 57Fe Mössbauer spectrometry which is a very efficient tool to investigate such materials. Then, we report the common features which characterise the temperature dependence of Mössbauer spectra; the hyperfine field temperature dependence of both the crystalline grains and the intergranular phase is discussed for different crystalline fractions in order to model the magnetic behaviour of the nanocrystalline alloys. [ABSTRACT FROM AUTHOR]

Magnetic polymer gels are a new promising class of nanocomposite gels. In this work, magnetic PEO/iron oxide nanocomposite hydrogels were synthesized using the one-step γ-irradiation method starting from poly(ethylene oxide) (PEO) and iron(III) precursor alkaline aqueous suspensions followed by simultaneous crosslinking of PEO chains and reduction of Fe(III) precursor. γ-irradiation dose and concentrations of Fe3+, 2-propanol and PEO in the initial suspensions were varied and optimized. With 2-propanol and at high doses magnetic gels with embedded magnetite nanoparticles were obtained, as confirmed by XRD, SEM and Mössbauer spectrometry. The quantitative determination of γ-irradiation generated Fe2+ was performed using the 1,10-phenanthroline method. The maximal Fe2+ molar fraction of 0.55 was achieved at 300 kGy, pH = 12 and initial 5% of Fe3+. The DSC and rheological measurements confirmed the formation of a well-structured network. The thermal and rheological properties of gels depended on the dose, PEO concentration and initial Fe3+ content (amount of nanoparticles synthesized inside gels). More amorphous and stronger gels were formed at higher dose and higher nanoparticle content. The properties of synthesized gels were determined by the presence of magnetic iron oxide nanoparticles, which acted as reinforcing agents and additional crosslinkers of PEO chains thus facilitating the one-step gel formation. [ABSTRACT FROM AUTHOR]

To introduce a paramagnetic intergranular phase into the ThMn 12 -type permanent materials, SmFe 12 -based alloys with the composition of Sm x Zr 0.2 (Fe 0. 8 Co 0.2) 11.5 Ti 0.5 (x = 0.8–1.4, at.%) are designed and prepared by arc-melting and melt-spinning. Roles of extra Sm on the phase constitution and magnetic properties are systematically investigated. First of all, within the range of x = 0.8–1.2, the as-cast ingots mainly constitute of 1:12, 1:10, 1:2 and α -(Fe,Co) phase. With increasing Sm content, both 1:12 and α -(Fe,Co) phases decrease whereas 1:2 and 1:10 phases increase. Similarly, for the heat-treated ribbons with x = 0.8–1.2, α -(Fe,Co) phase also decreases with the increasing Sm content. Consequently, the J s and J r of the alloys exhibit a decreasing trend while the H c and (BH) max show an increasing trend. As a result, excellent magnetic properties of J r = 1.04 T for x = 0.8 alloy, (BH) max = 61 kJ/m3 and H c = 3.0 kOe for x = 1.2 alloys are acquired. Henkel curves of the annealed ribbons prove the existence of an exchange coupling effect in all alloys, which has contributed to the remanence enhancement. Interestingly, the observed kink in the demagnetization curve of x = 1.2 annealed alloy suggests the ineffective exchange coupling between soft and hard grains. An amorphous grain boundary phase is observed in the annealed x = 1.2 alloy while the refined 57Fe Mössbauer spectrum confirms its paramagnetic behavior. The present work may provide a dependable guideline for designing the composition and microstructure of 1:12-based permanent material. Image 1 • Relatively high magnetic properties of J r = 1.04 T and BH max = 61 kJ/m3 were obtained. • A paramganetic amorphous GB phase is obseved in x = 1.2 alloy. • The non-magnetic GB phase could be successfully induced by Sm addtion. [ABSTRACT FROM AUTHOR]

The equiatomic FeCo alloy with average particle sizes of 140 and 30 nm is obtained using an instant chemical reduction process. The mean hyperfine field of 36.0(5) T estimated from 300 K 57Fe Mössbauer spectra is consistent with a disordered FeCo phase with a relative fraction of 90(2)% for both the samples, along with γ‐Fe2O3. A CoO shell with an average thickness of 2.7 nm is inferred from transmission electron microscopy in the size‐reduced FeCo. The room temperature coercivity of the size‐reduced FeCo is higher than the expected theoretical values. An exchange bias field (HE of 296 Oe), vertical remanence shift at 15 K, and an exchange bias blocking temperature of 150 K are exhibited by the 30 nm FeCo particles. The observed HE and its temperature dependence are fairly explained based on a random field model. [ABSTRACT FROM AUTHOR]

The powders of the Fe93.28Si6.72 soft magnetic system and the Nd2Fe14B hard magnetic system were mixed, pressed and finally sintered at 300, 400 and 500 °C. The powder chosen for the soft phase (Fe93.28Si6.72) used was the one milled with a surfactant for 48 h and the hard phase powder was the original commercial powder without milling. The sintered samples were characterized by XRD, Mössbauer spectrometry and VSM. After this characterization, the sample with the best magnetic behavior, with a larger coercive field and saturation magnetization, was the one treated at 500 °C, however, none of the treated samples showed a perfect ferromagnetic coupling between the soft and hard phases. [ABSTRACT FROM AUTHOR]

In the field of nanomedicine, superparamagnetic nanoparticles are one of the most studied nanomaterials for theranostics. In this study, a one-pot synthesis of magnetic nanoparticles is presented, with an increased control on particle size from 10 to 40 nm. Monitoring of vacuum level is introduced here as a crucial parameter for achieving a fine particle morphology. The magnetic properties of these nanoparticles are highly affected by disorders or mismatches in crystal structure. A prolonged oxidation step is applied to the obtained nanoparticles to transform the magnetic phases into a pure maghemite one, confirmed by high-resolution X-ray photoelectron spectroscopy analysis, by Mössbauer spectrometry and, indirectly, by increased performances in magnetization curves and in relaxation times. Afterward, the attained nanoparticles are transferred into water by a nonderivatized dextran coating. Thermogravimetric analysis confirms that polysaccharide molecules replace oleic acid on the surface by stabilizing the particles in the aqueous phase and culture media. Preliminary in vitro test reveals that the dextran-coated nanoparticles are not passively internalized from the cells. As a proof of concept, a secondary layer of chitosan assures a positive charge to the nanoparticle surface, thus enhancing cellular internalization.