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Five different batches of Li 0.25 Zn 0.3 Co 0.15 Fe 2.3 O 4 (LZC) nanoparticles were prepared by sol-gel method. Of these five batches, one has a very small mean size of ∼6.0 nm and the others have mean sizes of ∼11.9, 47.3, 114 and 139 nm. The phase formation of the nanoparticles is confirmed by analysing the X-ray diffraction (XRD) patterns using the Rietveld method. To ensure phase formation, further structural analyses, namely transmission electron microscopy, Raman spectroscopy and x-ray photoemission spectroscopy measurements are performed. Before analysing the magnetic properties of the prepared nanoparticles, Mössbauer spectra are recorded both at room temperature and at 77 K to determine the magnetic nature and hyperfine behaviour of the nanoparticles. The resence of magnetically blocked states is estimated by recording the dynamic hysteresis loops and then to gain insight into the magnetic properties of this particular Li-Zn-Co-ferrite stoichiometry, static M − H loops and field cooled and zero field cooled M-T curves are extracted using a vibrating sample magnetometer. Finally, the applicability of prepared nanoparticles as a heat mediator in magnetic induction heating is studied in an external field of 335 Oe intensity and 290 kHz frequency. The highest specific absorption rate (SAR) is found to be ∼212 W/g Ferrite for 47.3 nm nanoparticles at a concentration of only 1 mg/mL. [Display omitted] • Nanoparticles (size ∼ 6 nm) of Li 0.25 Zn 0.3 Co 0.15 Fe 2.3 O 4 are prepared by sol gel method in a pure phase. • Presence of superparamagnetic nanoparticles is confirmed in smaller nanoparticles (size ∼ 6 - 12 nm). • High saturation magnetization with enhanced anisotropy is observed. • Nanoparticles exhibit significant magnetic induction heating efficiency. • Hyperthermia temperature is reached within a short interval (∼6 min) of switching the external ac magnetic field. [ABSTRACT FROM AUTHOR]

Fe-substituted YFexCr1−xO3 crystalline compounds show promising magnetic and multiferroic properties. Here we report the synthesis and characterization of several compositions from this series. Using the autocombustion route, various compositions (x = 0.25, 0.50, 0.6, 0.75, 0.9, and 1) were synthesized as high-quality crystalline powders. In order to obtain microscopic and atomic information about their structure and magnetism, characterization was performed using room temperature X-ray diffraction and energy dispersion analysis as well as temperature-dependent neutron diffraction, magnetometry, and 57Fe Mössbauer spectrometry. Rietveld analysis of the diffraction data revealed a crystallite size of 84 (8) nm for YFeO3, while energy dispersion analysis indicated compositions close to the nominal compositions. The magnetic results suggested an enhancement of the weak ferromagnetism for the YFeO3 phase due to two contributions. First, a high magnetocrystalline anisotropy was associated with the crystalline character that favored a unique high canting angle of the antiferromagnetic phase (13°), as indicated by the neutron diffraction analysis. This was also evidenced by the high magnetic hysteresis curves up to 90 kOe by a remarkable high critical coercivity value of 46.7 kOe at room temperature. Second, the Dzyaloshinskii–Moriya interactions between homogenous and heterogeneous magnetic pairs resulted from the inhomogeneous distribution of Fe3+ and Cr3+ ions, as indicated by 57Fe Mössbauer studies. Together, these results point to new methods of controlling the magnetic properties of these materials. [ABSTRACT FROM AUTHOR]

Previous experimental studies on clay potentiometric titration have been unable to distinguish inorganic cation exchange in the interlayer and on basal plane surfaces from specific pH-dependent sorption of cations and anions on the edges. In this study, we refined a titration technique, combining discontinuous backtitration and cation exchange capacity (CEC) measurements, and applied it to the potentiometric titration of Na- and Ca-conditioned montmorillonites. This technique can be used to accurately measure cation exchange, edge surface proton charge, dissolution of clay, and precipitation of new phases. Thus, a precise measurement of the variations of net proton surface charge is possible. This has important implications for clay surface modeling (see part II of this article) and for processes that depend on the clay surface charge, e.g., alteration, rheological processes, and contamination retention applications. In addition, this study confirms the adsorption of ionic pairs such as CaCl+ in exchange site positions and shows that CaOH+ could behave like CaCl+. This result, together with the evidence of precipitation of a Ca&z.sbnd;Si phase over a short time-scale (1 week) at high pH and low temperature, can be used to model clay–concrete interactions more accurately. We confirmed and quantified the H+/Na+ exchange reaction at low pH. Finally, we demonstrate that both the edge surface charge and the permanent structural charge are compensated for by the nonspecific sorption of cations from solution across the entire pH range from 4 to 11. Under these conditions, the surface potential is fully screened and does not need to be invoked in modeling sorption processes on clay particles in dilute suspensions. [Copyright &y& Elsevier]

Raspberry-shaped iron oxide nanostructures (RSNs) correspond to oriented aggregated and hollow clusters of nanograins exhibiting a high saturation magnetization and a superparamagnetic behaviour. These nanostructures are promising for a wide range of applications, such as magnetic separation, catalysis, pollution control, and nanomedicine. However, for most applications, particularly nanomedecine and depollution, high colloidal stability is required, and the isoelectric point of iron oxide is around 6–7. Therefore, these nanoclusters need to be coated with a surfactant to obtain colloidal suspensions in water. Here, we have developed a one-pot polyol solvothermal synthesis process to coat these promising nanoclusters with tannic acid (TA), a natural compound with antimicrobial properties, which has been little studied with these nanoclusters. Different parameters of the synthesis were adjusted, such as the molar ratio TA:Fe, the synthesis temperature and duration. We showed that TA interferes deeply in the RSNs synthesis mechanism with the observed reduction of iron(III) to iron(II), the complexation of TA with iron, the formation of intermediate phases, as well as the growth of a parasitic iron carbonate phase and the loss of the oriented aggregation and hollowness of the iron oxide RSNs. Considering all these parameters, the optimal synthesis conditions were thus established (TA:Fe ratio = 0.010, temperature of 200°C and duration of 10.5 h), leading to RSNs with small nanograins, a rather high surface area (82 m2/g), high saturation magnetization (74 emu/g) and good colloidal stability. By combining different characterization techniques, a new synthesis mechanism was proposed different from previously established for RSNs without TA, based on strong TA-iron oxide interfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

57Fe Mössbauer spectroscopy is used to elucidate the nature of the hyperfine interactions present in amorphous and nanocrystalline forms of Fe80Ti7Cu1B12 alloy. Two mutually independent distributions of hyperfine fields and one sextet of Lorentzian lines are employed to reproduce the broad (atoms in amorphous rest and interface zone) and narrow (ordered) parts of the spectra, respectively. The presented conclusions are derived from three-dimensional mapping of the hyperfine field distributions corresponding to both amorphous and interfacial spectral components. The individual distributions are decomposed into Gaussian components which characterize different types of hyperfine interactions. [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 physico-chemical properties of akaganeite are known to be modified when formed in the presence of ions, but there are no reports on these effects for arsenic, antimony and mercury. In this work, akaganeites are precipitated via hydrolysis of FeCl3 solutions in the absence and in the presence of varying concentrations of As5+, Sb3+ and Hg2+. All co-precipitated akaganeites exhibit an acicular morphology, and the increase of ion concentration greatly reduces the particle sizes and induces a transformation from nanostructured powders to nanoparticle morphologies. The variation of the mean crystallite size versus ion concentration is fitted to an exponential function, and the derived parameters suggest that the energy for particle growth is greater for akaganeite co-precipitated with As5+. The analysis of infrared, Raman and Mössbauer spectra suggests the replacement of OH⋯Cl groups by ionic species located at the surface and tunnel sites. The 77 K hyperfine data suggest that the iron ions in the vicinity of unoccupied chloride sites and on the surface are the most affected ones. One can unambiguously conclude that these ions do not replace iron in the lattice but are adsorbed at the surface and possibly to tunnel sites as ionic species during nucleation and growth of the particles, altering the surface tension of the nucleus and also the growth energy. [ABSTRACT FROM AUTHOR]

Abstract The present work is focused on the effect of substitution of Co2+ and Cu2+ ions on the structural, morphological, magnetic and optical properties of nanocrystalline ternary doped ferrite nanoparticles (NPs) having formula Mn 0.4 Co 0.6-x Cu x Fe 2 O 4 (x = 0, 0.2, 0.4, 0.6). They were synthesized using sol-gel precursor methodology and then sintered at 300 °C for 3 h and characterized by XRD, FT-IR, 57Fe Mössbauer and magnetometry. Alteration in surface morphology and surface area was studied using SEM-EDX, TEM and BET analyses. XRD patterns confirmed the formation of single phase ferrite NPs. Doping of Cu2+ ions in MnFe 2 O 4 NPs led to slight increase in magnetization, whereas doping with Co2+ ions appreciably increased the magnetization. The results were correlated to magnetic moment of cations. Maximum saturation magnetization value was 65.0 emu/g for ternary ferrite NPs having formula Mn 0.4 Co 0.4 Cu 0.2 Fe 2 O 4. Doping of MnFe 2 O 4 with Co2+ and Cu2+ ions enhanced surface area. The change in Mössbauer parameters suggested the alteration in environment of Fe3+ ions in presence of different divalent ions. Optical studies revealed lowering in band gap up to 2.03 eV on doping and minimum band gap was observed in Mn 0.4 Co 0.4 Cu 0.2 Fe 2 O 4 NPs. The results confirmed the improved magnetic and optical properties of ternary doped ferrite NPs as compared to pristine counterparts. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

[Display omitted] • Testing aging effect on magnetic properties of ternary magnetic nanohybrid. • Impact of magnetic nanohybrid in an effluent with living beings. • Low lethality of Daphnia magna after application of the magnetic nanohybrid. • Reproductive rate test was found to be nanohybrid dose dependent. A ternary magnetic nanohybrid, composed of maghemite, titanium dioxide (anatase phase), and graphene oxide as synthetized by co-precipitation method and initially applied with success to arsenic removal from contaminated synthetic effluent, has its main magnetic properties (the thermal dependence of the coercive field, the saturation magnetization, and the effective anisotropy constant values) systematically studied using a modified Kneller's and modified Bloch's laws applied to magnetization data. Besides values of exchange integral and spin wave stiffness constant equal to 2.7 meV and 949 meV Å2 respectively calculated, the Fe-oxide nanoparticles have ca. 11% of Fe spin in canted configuration, a result that also agreed with the description of the in-field Mössbauer spectrum. A magnetization saturation value of 47.5 emu g −1 (size of 19.6 nm) at 300 K and the Bloch's exponent of 3/2 have suggested that the ternary nanocomposite behaves like a 3D material. In order to check the impact of this ternary nanocomposite, acute toxicity tests were performed on Daphnia Magna water fleas neonates for a 24-hour exposure period due to (i) the fast metabolism of daphnids and (ii) the fact that the nanocomposite precipitates within one day at concentrations of interest for nanoremediation. Post-exposure effects were also studied after the first offspring hatched (2 weeks). A lethal concentration LC 50 value of 0.55 mg mL−1 was found for this experiment. Analysis of morphological changes showed toxicity with little significant difference between exposed and negative control individuals. The reproductive rate test was dose dependent. [ABSTRACT FROM AUTHOR]

In the Neolithic Gavà mines, variscite and turquoise were exploited for ornaments manufacturing, although some prospective pits and tunnels were dug on other similar greenish minerals such as smectite or kandite. A 3D study of the distribution of mineral phases allows us to determine the parameters involved in variscite colours. Methods are comprised of quantitative colourimetry, thin section petrography, SEM-BSE-EDS, EMPA, XRD, Raman spectroscopy, and 57Fe Mössbauer spectrometry. Mapping of the mines indicates that colour is not directly dependent on depth. Although variscite from Gavà is poor in Cr3+ and V+3 compared with gemmy variscite from other localities, the deep green samples content has the highest values of Cr3+. In the case of cryptocrystalline mixtures with jarosite, phosphosiderite, or goethite, variscite tends to acquire a greenish brown to olivaceous hue. If white minerals such as quartz, kandite, crandallite, or alunite are involved in the mixtures, variscite and turquoise colours become paler. [ABSTRACT FROM AUTHOR]

The chemical synthesis of shape and composition controlled Fe based binary alloys has been challenging due to the highly oxidizing nature of Fe. Here, we report the physical properties of flower-like Fe50Co50 nanoparticles prepared by a unique polyol process based on the addition of precursors at the elevated temperature. The magnetic properties are correlated through synchrotron radiation based X-ray diffraction and 57Fe Mössbauer spectrometry. Transmission electron microscopy analysis exposed the flower-like morphology of the FeCo particles. The FeCo nanoparticles showed a coercivity of 440 Oe, attributed to the shape anisotropy of the flower-like shape. Room temperature Mössbauer investigation revealed hyperfine fields of 34.9 and 36.7 T, suggesting two different Fe environments in the disordered state. Mössbauer analysis also showed the presence of superparamagnetic Fe-oxide with a relative fraction of 17%. [ABSTRACT FROM AUTHOR]

• Multiferroic nanocomposite (Ni 0.5 Zn 0.5 Fe 2 O 4) 0.5 (TiO 2) 0.5 was prepared by bottom-up approach. • Magnetic data confirms the ferrimagnetic state in the nanocomposite at room temperature (RT). • The dielectric spectrum reveals the non-Debye type of relaxation present in the sample. • P-E hysteresis loops confirm the presence of ferroelectric property at RT. • Nonlinear variation of the MC confirms the presence of magnetoelectric coupling at RT. A new multiferroic nanocomposite resulting from a subtile mixture of Ni 0.5 Zn 0.5 Fe 2 O 4 and TiO 2 nanocrystalline grains was synthesized by bottom-up approach. The structural, nanostructural and morphological characteristics of the nanocomposite were carefully evaluated from the X-ray patterns, from fringe patterns and selected area electron diffraction (SAED) patterns obtained by High Resolution Transmission Electron Microscope. The dielectric permittivity of the NZFO-TO nanocomposite is characterized by a phase transition from the ferroelectric to paraelectric order at ∼390 K while the corresponding spectrum reveals a non-Debye type of relaxation phenomenon. It is concluded that this nanocomposite is suitable to be applied in magnetoelectric devices. [ABSTRACT FROM AUTHOR]

The epidemic spreading on spatial-driven network is studied with the spatial susceptible-infected-susceptible (SIS) model. The network is constructed by random addition of nodes on the plan. The probability for a previous node to be connected to the new one is inversely proportional to their spatial distance to the power a. The spreading rate between two nodes is inversely proportional to their spatial distance. The effective spreading time increases with the increasing of ɑ. The proportional coefficient is found to have a ɑ-dependent threshold with a maximum situated in the interval 1.5 < ɑ < 2. [ABSTRACT FROM AUTHOR]

In order to assess the adsorption properties of hydrogen gas and reactivity of adsorbed hydrogen, we measured H2(g) adsorption on Na synthetic montmorillonite-type clays and Callovo-Oxfordian (COx) clayrock using gas chromatography. Synthetic montmorillonites with increasing structural Fe(III) substitution (0 wt %, 3.2 wt %, and 6.4 wt % Fe) were used. Fe in the synthetic montmorillonites is principally present as structural Fe(III) ions. We studied the concomitant reduction of structural Fe(III) in the clays using 57Fe Mössbauer spectrometry. The COx, which mainly contains smectite/illite and calcite minerals, is also studied together with the pure clay fraction of this clayrock. Experiments were performed with dry clay samples which were reacted with hydrogen gas at 90 and 120 °C for 30 to 45 days at a hydrogen partial pressure close to 0.45 bar. Results indicate that up to 0.11 wt % of hydrogen is adsorbed on the clays at 90 °C under 0.45 bar of relative pressure. 57Fe Mössbauer spectrometry shows that up to 6% of the total structural Fe(III) initially present in these synthetic clays is reduced upon adsorption of hydrogen gas. No reduction is observed with the COx sample in the present experimental conditions. [ABSTRACT FROM AUTHOR]

Magnetic structures have attracted a great interest due to their multiple applications, from physics to biomedicine. Iron, nickel and cobalt are among the most important ferromagnetic elements, therefore the synthesis of Fe-based alloys processed by ball milling from the Fe, Ni and Co powders is of particular interest. This subject mainly concerned the structural and magnetic properties evolution of Fe50Co25Ni25 nanocrystalline powder mixture prepared by mechanical alloying in a high-energy planetary ball mill under argon atmosphere. For extended milling time of 100 h, two nanocrystalline Fe (Co,Ni) (∼ 87 nm) and fcc-Co-rich (∼ 47 nm) phases were identified. This phase transformations, dependent on the alloying time, are related to the increase in dislocations and accumulation of stacking faults. Dislocation density of 1.25 × 1015 m−2 is estimated after 100 h of milling. The milled FeCoNi alloy displays a soft ferromagnetic behavior with single magnetic domain (Hc ∼ 12.5 Oe and Mr/Ms ∼ 0.007 for 100 h milling). Mössbauer analysis gives three main magnetic components: two different components attributed to metallic Fe species located in bcc and fcc Fe–Co–Ni domains and a magnetic component characterized by larger hyperfine fields and isomer shifts typical of Fe3+, Fe2+ species and Fe ions. [ABSTRACT FROM AUTHOR]

Surface magnetic configuration in samples NPEDTA1 and NPEDTA2 samples without and in the presence of an applied magnetic field (8T). The arrows represent the spin magnetic moment for each magnetic phase. • EDTA functionalized maghemite nanoadsorbents were prepared and tested for Pb absorption. • Surface spin canting and exchange bias effects were explained using XPS and high field Mössbauer experiments. • 99.9% Pb(II) is adsorbed from water after 7 h of contact time. • The nanomaterials have shown remarkable adsorption performance for pH > 6. • The adsorption mechanism was demonstrated to be due the EDTA chelating properties. • The tested nanoadsorbent has remarkable reusability properties. EDTA functionalized γ-Fe 2 O 3 nanoparticles, with controlled-sizes between 4 and 8 nm and specific surface areas up to 272 m2/g, were prepared using modified co-precipitation routes and systematically characterized using local, surface and global experimental methods. The functionalized nanoparticles behave as a magnetic trilayer-like system formed by ferrimagnetic spinel-like grains, a spin-glass-like layer as a spacer, and a cover of iron hydroxide layer with antiferromagnetic interactions. The fraction of the Fe canted spins in the spacer layer and the specific surface area are directly related to the amount of the iron hydroxide thin layer. Small (large) amounts of the iron-hydroxide layer on the nanoparticle surfaces reduce (increase) the canted Fe spin fraction, decreasing (increasing) the exchange bias effect found in the functionalized NPs. The nanoparticles with the largest specific area were applied for Pb(II) adsorption and showed a reduction of Pb(II) concentration in contaminated water to a limit less than 10 μg L−1 for an equilibrium time of 7 h. The EDTA tailored γ-Fe 2 O 3 nanoparticles showed efficient Pb(II) adsorption, easy magnetic removal, and recycling properties, making this nanohybrid adsorbent a good potential candidate for a water cleaning process. [ABSTRACT FROM AUTHOR]

This review summarizes the recent advances on the application of 57Fe Mössbauer spectrometry to study the magnetic and phase characteristics of Nd–Fe–B-based permanent magnets. First of all, the hyperfine structures of the Ce2Fe14B, (Ce, Nd)2Fe14B and MM2Fe14B phases are well-defined by using the model based on the Wigner-Seitz analysis of the crystal structure. The results show that the isomer shift δ and the quadrupole splitting ΔEQ of those 2:14:1 phases show minor changes with the Nd content, while the hyperfine field Bhf increases monotonically with increasing Nd content and its value is influenced by the element segregation and phase separation in the 2:14:1 phase. Then, the hyperfine structures of the low fraction secondary phases are determined by the 57Fe Mössbauer spectrometry due to its high sensitivity. On this basis, the content, magnetic behavior, and magnetization of the REFe2 phase, the amorphous grain boundary (GB) phase, and the amorphous worm-like phase, as well as their effects on the magnetic properties, are systematically studied. [ABSTRACT FROM AUTHOR]

• Ni 0.5 Zn 0.4 Cu 0.1 Fe 2 O 4 ferrite nanoparticles were prepared and incorporated in the titanium dioxide matrix. • Structural and morphological insvestigations were carried out. • Investigation of the magnetic and Mössbauer spectra revealed the presence of superparamagnetic phenomena. • The microwave reflection loss enhances significantly in the incorporated sample. • Considerable specific absorption rate was observed during inductive heating study of the samples. Ni 0.5 Zn 0.4 Cu 0.1 Fe 2 O 4 ferrite nanoparticles (NZCUFO) were prepared using a conventional co-precipitation method. The NZCUFO nanoparticles were then combined with titanium dioxide matrix to make the nanocomposite of [TiO 2 ] 0.2 [Ni 0.5 Zn 0.4 Cu 0.1 Fe 2 O 4 ] 0.8 (TNZCUFO). The formation of the appropriate crystallographic phase was confirmed by analyzing the X-ray diffraction pattern of the samples. Investigations extracted from the X-ray fluorescence spectroscopy, high-resolution transmission electron microscopy, and Raman spectroscopy imply the successful association of ferrite nanoparticles into the TiO 2 matrix. At 300 K, the saturation magnetization of NZCUFO and TNZCUFO reaches 34.6 and 23.4 emu/g, respectively. Mössbauer spectra recorded at 77 and 300 K indicate the presence of superparamagnetic behavior. These results were in agreement with the data obtained from magnetic hysteresis loop, zero field cooled, and field-cooled magnetization measurements. Both the samples were exposed to alternating current inductive heating and the extracted results successfully satisfy the condition of hyperthermia therapy for cancer treatment. The electromagnetic wave absorption capabilities of the samples were measured in the microwave region (8–18 GHz). The microwave reflection loss reaches −13.6 dB at 11.6 GHz and −29.7 dB at 11 GHz for the 2 mm thick samples of NZCUFO and TNZCUFO, respectively. The balanced matching of magnetic and dielectric loss, high magnetization, and specific absorption rate of the samples would be extremely useful for diverse soft magnetic applications. [ABSTRACT FROM AUTHOR]

REFe 2 (RE = rare earth) phase has been considered to form spontaneously in Nd-Ce-Fe-B cast strips and inherit into sintered magnets. However, here we report that REFe 2 phase, which is absent in starting strip, occurs in as-sintered magnet with an identical composition of 25 wt% Ce. More interestingly, the formation of REFe 2 induces apparent Ce-enriched shell surrounding RE 2 Fe 14 B grain, which is further exacerbated in annealed magnet containing a higher fraction of REFe 2 phase. Influences of increasing REFe 2 fraction on magnetic performance are revealed. Above findings on REFe 2 phase evolution and resultant Ce segregation may shed lights on fabricating high-performance Nd-Ce-Fe-B. Here we report two novel findings in the Nd-Ce-Fe-B system, (i) REFe 2 phase occurs after sintering and annealing, which is however absent in the starting cast strip with the same Ce substitution of 25 wt.%, as evidenced by the Rietveld refinement result (a) and SAED patterns along three different zone axes of REFe 2 phase (b); (ii) Ce segregates at the surface of 2:14:1 main phase grain upon forming additional REFe 2 in the as-sintered magnet (c), which is further exacerbated in the annealed one containing higher REFe 2 fraction (d). Unlabelled Image [ABSTRACT FROM AUTHOR]

Contaminant removal from (waste)waters by magnetite is a promising technology. In the present experimental study, a magnetite recycled from the steel industry waste (zero-valent iron powder) was used to investigate the sorption of As, Sb and U in phosphate-free and -rich suspensions, i.e. as a remediation for the acidic phosphogypsum leachates derived from the phosphate fertilizer industry. The results showed up to 98% U removal under controlled pH conditions, while phosphate did not hinder this immobilisation. In contrast, the results confirmed the limited uptake of As and Sb oxyanions by magnetite in presence of phosphate as the competing anion, displaying only 7–11% removal, compared to 83–87% in the phosphate-free sorption experiments. To limit this wastewater problem, raw ZVI anaerobic oxidation was examined as mechanism to increase the pH and as a source of Fe2+ in a first step, and in a second step to remove phosphate via vivianite precipitation, therefore prior to the reaction with magnetite. UV–Vis, XRD and SEM-EDS showed that vivianite precipitation is feasible at pH > 4.5, mainly depending on the phosphate concentration. The higher the [PO 4 3−], the lower is the pH at which vivianite precipitates and the higher the % removal of phosphate from solution. It is anticipated that an optimum 3-steps design with separate reactors controlling the conditions of ZVI oxidation, followed by vivianite precipitation and finally, reaction with magnetite, can achieve high contaminant uptake in field applications. [Display omitted] • Sorption of As, Sb, and U by magnetite in acidic, PO 4 3− rich waters is shown. • PO 4 3− does not hinder U sorption, on the contrary to As and Sb. • (N)ZVI is used to increase the water pH and produce Fe2+ to form vivianite. • Phosphate ions precipitate as vivianite at pH > 4.5, depending mainly on [PO 4 3−]. • A novel, eco-friendly remediation route of acidic, PO 4 3--rich waters is suggested. [ABSTRACT FROM AUTHOR]

Optimizing the performance of magnetocaloric materials is facilitated by understanding the thermomagnetic transitions they undergo, including the order of these transitions and their strength. Those exhibiting strong first-order phase transitions (FOPT) are accompanied by large heating and cooling responses but with relatively small cyclic responses, while materials with second-order (SOPT) character exhibit moderate heating and cooling responses. However, the lack of hysteresis could partially compensate for the lower magnitudes with a more cyclic response. One way to effectively maximize the cyclic response, combining the advantages of FOPT and SOPT, is to fine tune the transition towards the borderline of FOPT-SOPT, which can minimize hysteresis. For the well-known La(Fe,Si) 13 family, it is challenging to identify and/or evaluate the critical point where FOPT crossovers to SOPT based on conventional techniques. To address these ambiguities, in this work, we apply the field dependence exponent n criteria to a series of lowly hysteretic and high-performance La(Fe,Mn,Si) 13 H magnetocaloric materials with compositions close to the critical one. Even if the sample with the lowest hysteresis resembles characteristics of SOPT, it is evidently identified as undergoing FOPT from the n criteria: (1) existence of n > 2 overshoot and (2) n at the tra n sition temperature, n transitio n , is 0.37. This proximity to the critical composition (n transitio n =0.4) further explains the low hysteresis observed. This FOPT character of the series is confirmed by temperature-dependent 57Fe Mössbauer spectrometry studies, fitting the hyperfine field to the Bean-Rodbell model instead of the usual Brillouin function. As it is a zero-field method, the confirmation by Mössbauer spectrometry gives further strength to the n -criterio n. • Order of the transition identified for weakly hysteretic La(Fe,Mn,Si) 13 H series. • Exponent n criteria identify the first-order character in the studied samples. • Samples found to be near the critical point. • First-order character further corroborated from Mössbauer spectrometry. [ABSTRACT FROM AUTHOR]

Abstract The RE-rich (Ce 1−x Nd x) 16 Fe 78 B 6 (x = 0–1) nanocrystalline alloys were prepared by melt-spinning method. The transmission electron microscopy equipped with EDS was employed to investigate the microstructure and rare-earth element segregation. The average Nd/RE ratios in 2:14:1 grains are 22, 52, 67, 74, 78, and 81% for the x = 0.1, 0.4, 0.5, 0.6, 0.7, and 0.8 alloys, respectively, which are larger than the nominal ratios, indicating a Nd segregation in 2:14:1 phase. The Nd/RE ratio changing with x shows a two-stage of increment: the average increment in x = 0.1–0.5 alloys is much higher than that of x = 0.5–0.8 alloys. The corresponding change is also observed in the plotted intrinsic parameters of cell volume V , hyperfine field B hf , and spin reorientation temperature T SR of the 2:14:1 phase changing with x curves. The high Ce-contained RE-rich Nd-Ce-Fe-B with strong element segregation shows high coercivities and high performance/price ratio. The present results thus contribute to understanding the fundamental mechanism of Ce-contained Nd-Ce-Fe-B permanent magnets and taking advantage of the element segregation. Highlights • Strong RE segregation is observed in the nanocrystalline (Ce 1−x Nd x) 16 Fe 78 B 6 (x = 0–1) alloys. • Both the magnetic properties and Nd/RE ratios in 2:14:1 phase show a two-stage change with the increasing Nd content. • The Ce segregation in 1:2 phase promotes the element segregation and further increases the Nd/RE ratios in 2:14:1 phase. [ABSTRACT FROM AUTHOR]

In this work, we present a correlation between High Resolution Transmission Electron Microscopy (HRTEM) and in-field Mössbauer spectrometry to point out exchange coupling behavior, surface effects and chemical disorder in Co x Fe 3-x O 4 cobalt ferrite nanoparticles. The samples were synthesized by a solvothermal chemical route. The hysteresis loops, recorded by using Vibrating Sample Magnetometer (VSM), suggest a jump-like behavior nearby zero applied magnetic fields. The HRTEM micrographs illustrate the presence of faceted nanoparticles for x < 1. Moreover, the images show the presence of some crystal defects such as twins. 3D images have been simulated to determine the crystallographic orientation for the different facets. By performing analyses using a TEM corrected spherical aberration (Cs), we have evidenced the presence of twin boundaries viewed along the [110] orientation at atomic scale. These crystal defects, facets and twin boundaries promote important interactions between nanoparticles. The spin frustration has been investigated by in-field Mössbauer spectrometry performed for three samples chosen by respect to zero field analyses. The observed frustrated Fe moments have been referred to three different origins: interactions in the contact surface between faceted nanoparticles, chemical disorder and surface effects for x = 1.6 and 1.8. A canted layer of about 0.35 nm for grain size of about 6 nm has been found for x = 1.6. [ABSTRACT FROM AUTHOR]

Barium lanthanum ferrite and four Mn/Ti substituted materials were synthesized by the sol-gel method. The crystal structure of the materials was studied by a combination of X-ray powder diffraction, electron diffraction, scanning transmission electron microscopy and 57 Fe Mössbauer spectrometry. BaLaFe 2 O 6-δ has a cubic perovskite structure and Ba 0.7 La 1.3 FeMnO 6-δ is distorted perovskite with the R 3 ̅ c symmetry, both from electron diffraction and X-ray powder diffraction. However, according to transmission electron microscopy, the crystals of BaLaFeTiO 6-δ , BaLaFeTi 0.5 Mn 0.5 O 6-δ , and BaLaFe 0.5 Ti 0.5 MnO 6-δ consist of nanodomains with different symmetries ( Pm 3 ̅ m next to R 3 ̅ c due to octahedral tilts), whereas the bulk X-ray powder diffraction patterns for these compounds correspond to the simple cubic structure. 57 Fe Mössbauer spectrometry confirms that all materials contain high spin state Fe 3+ ions which are strongly influenced by the chemical disorder resulting from various cationic environments. [ABSTRACT FROM AUTHOR]

The effects of laser irradiation on γ-Fe2O34 ± 1 nm diameter maghemite nanocrystals synthesized by co-precipitation and dispersed into an amorphous silica matrix by sol-gel methods have been investigated as function of iron oxide mass fraction. The structural properties of γ-Fe2O3phase were carefully examined by X-ray diffraction and transmission electron microscopy. It has been shown that γ-Fe2O3nanocrystals are isolated from each other and uniformly dispersed in silica matrix. The phase stability of maghemite nanocrystals was examinedin situunder laser irradiation by Raman spectroscopy and compared with that resulting from heat treatment by X-ray diffraction. It was concluded that ε-Fe2O3is an intermediate phase between γ-Fe2O3andα-Fe2O3and a series of distinct Raman vibrational bands were identified with the ε-Fe2O3phase. The structural transformation of γ-Fe2O3intoα-Fe2O3occurs either directly or via ε-Fe2O3, depending on the rate of nanocrystal agglomeration, the concentration of iron oxide in the nanocomposite and the properties of silica matrix. A phase diagram is established as a function of laser power density and concentration. [ABSTRACT FROM PUBLISHER]

Cobalt nano-ferrite of formula Co 0·4 Fe 2·6 O 4 was successfully prepared by a surfactant-free solvothermal reaction. Powder X-ray Diffraction (PXRD) revealed a cubic spinel structure. Transmission Electron Microscopy (TEM) observations confirmed the presence of agglomerated nanoparticles of two different sizes and shapes. 57Fe Mössbauer Spectrometry (MS) studies suggested a cationic redistribution between tetrahedral and octahedral sites in the spinel lattice. The low-frequency dependence of the dielectric properties is significantly affected by the presence of all polarization phenomena, in particular the interface polarization, on the basis of the phenomenological theory of the Koop model and the Maxwell-Wagner approach. At low frequencies, a linear negative correlation between the imaginary part of the permittivity and the frequency in the logarithm scale is observed. This is attributed to a dc-conductivity process. Furthermore, the electrical modulus analysis shows both Debye and non-Debye dielectric relaxations. The complex impedance plots were analyzed using the equivalent circuit model; grain and grain boundaries effects coexist. In the conductivity spectra, three regions were detected. A single power law and a double power law were separately applied to resolve the grains and grain boundaries effects. This unusual conductivity behavior can be explained by the modification in microstructure as well as the variation in charge carrier mobility. All results were interpreted in terms of microstructure properties and correlated with the cationic distribution within the spinel structure. The close values of activation energies obtained from the impedance, modulus and ac-conductivity in different temperature regions confirmed that the transport is probably due to a hopping mechanism dominated by smaller amount of oxygen vacancies. [Display omitted] • Co 0·4 Fe 2·6 O 4 nanoparticles were prepared by a surfactant-free solvothermal method using benzyl alcohol as solvent. • Microstructure observations and 57Fe Mossbauer spectrometry study explain the electrical conductivity results. • Complex impedance plots highlight the grains and grain boundaries contributions to the dielectric response. • The Co 0·4 Fe 2·6 O 4 material can be classified as a high-k dielectrics suitable for gate dielectric applications. [ABSTRACT FROM AUTHOR]

• γ to α -Fe 2 O 3 structural transformation occurs for laser power higher than 4.14 mW. • Zeolite type 5A improves thermal stability of nanomaghemite under laser irradiation. • In-field Mössbauer experiments helped to understand magnetic properties of γ -Fe 2 O 3. • Spin structure of nanoparticle surface and goethite showed canted spin configurations. • Concentrated and canted nanomaghemite favor the formation of superspinglass state. Maghemite nanoparticles functionalized with type 5A zeolite were prepared by co-precipitation to produce three different nanohybrid materials with potential for application in water remediation process. Raman and in-field 57Fe Mössbauer spectroscopies were used to bring information about structural and magnetic properties of these materials, while their magnetic properties were obtained from Direct Current magnetization experiments. The Raman data suggested the maghemite to hematite phase transition when two of the samples were exposed to laser power above 4.14 mW. For the two zeolite-based samples that exhibited a secondary goethite phase, the temperature-dependent Mössbauer results indicated low magnetic anisotropy for this phase, an effect associated with its low crystallinity. The spin structure of maghemite nanoparticles is described using the core-shell model, where ferrimagnetic core grains are easily polarized by external magnetic fields and are surrounded by non-collinear spins (canted spins) originating from the particle surface. No strong magnetic interaction between the maghemite nanoparticles and the goethite phase that would yield the exchange bias effect was observed; this may be due to the low magnetic anisotropy of the antiferromagnetic goethite, as suggested by the low crystallinity measured by Raman spectroscopy. Minor loop effects that occurred for in field-cooling loops are recorded in low scan fields due to the large magnetic anisotropy of the superspinglass state of the maghemite nanoparticles established by dipolar magnetic interactions. [ABSTRACT FROM AUTHOR]

(Na0.60Bi1.40) (Fe1.06Mn0.17Bi0.77)O6.87 and (K0.24Bi1.51) (Fe1.07Mn0.15Bi0.78)O6.86 are hydrothermally synthesized from aqueous solutions of NaBiO3, Fe(NO3)3, MnCl2, and NaOH or KOH (autoclave, 200 °C, 6 h). [ABSTRACT FROM AUTHOR]

An easy and straightforward strategy has been used for loading palladium(0) nanoparticles onto the magnetic surface of maghemite (γ-Fe2O3), without the use of organic modifiers. The nanocomposite was fully characterized by TEM, XRD, 57Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, and superconducting quantum interference device measurements. The Pd0@γ-Fe2O3 nanocatalyst has been investigated in various catalytic reactions, under mild conditions (100 kPa H2, RT), and in neat water. Relevant catalytic activities were achieved in the hydrogenation of olefinic substrates, as well as in hydrodehalogenation reactions of halogenoarenes, that constitutes a promising process for wastewater treatment. These nanocatalysts proved also pertinent for the reduction of nitroarene derivatives into the corresponding anilines, which are promising substrates for fine chemistry. Finally, these catalysts proved to be easily recoverable through the use of an external magnet, without significant loss of activity. [ABSTRACT FROM AUTHOR]

Denitrification is expected to occur at and near the interface with clayey formations dedicated to radioactive waste disposal, due to the nitrate content in some waste canisters and the high probability of introducing denitrifiers during the operational phase. Nitrate reduction to nitrous-oxide gas by pure-strain Pseudomonas mandelii , in the presence or absence of sterilized Callovian–Oxfordian (COx) clay rock, was studied over a period of ~ 41.5 months (1267 days) by means of batch experiments. A culture medium with a similar porewater chemistry to that of COx rocks was used, supplemented with acetate and nitrate. Bacterial growth was monitored by genomic-DNA and nar G-gene quantification. Nitrite accumulated in solution concomitantly with a decrease in nitrate content and the weak generation of nitrous oxide, but denitrification rates drastically decreased over the study period. Acetate was both oxidized to inorganic carbon and incorporated into biomass. The presence of solid COx particles significantly affected the geochemical reactions and particularly caused an enhanced nitrate reduction, a higher bacterial growth and the precipitation of calcium carbonate. Moreover, in the presence of COx a delay of several weeks was observed before the accumulation of nitrite in solution, leading to an imbalance between nitrate consumption and the production of nitrite, nitrous oxide and ammonium. Chemical oxidation of clay along with nitrite reduction to dinitrogen is expected to occur, explaining both the delay in nitrite accumulation and the apparent imbalance in nitrogen species. Although the electron donor of the COx oxidation was not identified, several hypotheses may be advanced, and we provide new insight into the biogeochemical and geochemical processes that may occur concomitantly at the excavation damaged interface of the clayey host rock after closure, resaturation and release of waste components in a nuclear waste repository. Because of denitrification, the oxidative impact of nitrate released from waste will diminish. However, nitrites produced through denitrification and diffusing into the rock will likely play in redox reaction via their abiotic reactivity which may occur within the compact clay formation despite a lack of space for bacterial activity. [ABSTRACT FROM AUTHOR]

A novel synthesis of cobalt–iron layered double hydroxide (LDH) with interlayer chlorides was investigated. The method consists in mixing concentrated solutions of hexaamminecobalt(III) trichloride with ferrous chloride at room temperature and in anoxic conditions. Four initial Fe/Co atomic ratios have been tried out (0.12, 0.6, 1.2 and 1.8). Neither heating nor addition of alkali was employed for adjusting the pH and precipitating the metal hydroxides. Still, each mixture led to the spontaneous precipitation of a LDH-rich solid having a crystal-chemistry that depended on the initial solution Fe/Co. These LDHs phases were carefully characterized by mean of X-ray diffraction, 57 Fe Mössbauer spectrometry, transmission electron microscopy and chemical analysis (total dissolution and phenanthroline method). Solution Eh and pH were also monitored during the synthesis. Increasing initial Fe/Co ratio impacted the dynamic of the observed stepwise reaction and the composition of the resulting product. Once the two solutions are mixed, a spontaneous and abrupt color change occurs after an induction time which depends on the starting Fe/Co ratio. This makes the overall process acting as a chemical clock. This spontaneous generation of CoFe-LDH arises from the interplay between redox chemistries of iron and cobalt–ammonium complexes. [ABSTRACT FROM AUTHOR]

We present the study of pristine and calcined f-MWCNTs functionalized by nitrogen-containing functional groups. We focus on the structural and microstructural modification tuned by the previous annealing. However, our primary goal was to analyze the electronic structure and magnetic properties in relation to the structural properties using a multi-technique approach. The studies carried out by X-ray diffraction, XPS, and 57Fe Mössbauer spectrometry revealed the presence of γ-Fe nanoparticles, Fe3C, and α-FeOOH as catalyst residues. XPS analysis based on the deconvolution of core level lines confirmed the presence of various nitrogen-based functional groups due to the purification and functionalization process of the nanotubes. The annealing procedure leads to a structural modification mainly associated with removing surface impurities as purification residues. Magnetic studies confirmed a significant contribution of Fe3C as evidenced by a Curie temperature estimated at TC = 452 ± 15 K. A slight change in magnetic properties upon annealing was revealed. The detailed studies performed on nanotubes are extremely important for the further synthesis of composite materials based on f-MWCNTs. [ABSTRACT FROM AUTHOR]

Abstract: Escherichia coli abatement was studied in liquid phase under visible light in the presence of two commercial titania photocatalysts, and of Fe- and Al-doped titania samples prepared by high energy ball-milling. The two commercial titania photocatalysts, Aeroxide P25 (Evonik industries) exhibiting both rutile and anatase structures and MPT625 (Ishihara Sangyo Kaisha), a Fe-, Al-, P- and S-doped titania exhibiting only the rutile phase, are active suggesting that neither the structure nor the doping is the driving parameter. Although the MPT625 UV–visible spectrum is shifted towards the visible domain with respect to the P25 one, the effect on bacteria is not increased. On the other hand, the ball milled iron-doped P25 samples exhibit low activities in bacteria abatement under visible light due to charge recombinations unfavorable to catalysis as shown by photoluminescence measurements. While doping elements are in interstitial positions within the rutile structure in MPT625 sample, they are located at the surface in ball milled samples and in isolated octahedral units according to 57Fe Mössbauer spectrometry. The location of doping elements at the surface is suggested to be responsible for the sample cytotoxicity observed in the dark. [Copyright &y& Elsevier]

We report the synthesis of yttrium iron garnet ( YIG) combining soft chemistry route, namely the polyol process, and spark plasma sintering ( SPS) technique. The polyol process produced an intermediary amorphous phase containing both iron and yttrium cations in the desired ratio. They were annealed at 400°C in air to decompose the organic content of the reaction (polyol and acetate). To achieve the garnet phase, the polyol-obtained precursor was subjected to reactive SPS treatment at a temperature of 750°C, far below the typical temperatures (1350°C) used in the classic solid-state reaction process. In 15 min pure and high-density Y3 Fe5 O12 ceramic, with about 100 nm sized crystalline grains, was obtained. We report as well the characterization of the initial amorphous phase and the obtained YIG by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, 57 Fe Mössbauer spectrometry, and magnetization measurements. [ABSTRACT FROM AUTHOR]

Highlights: [•] New measurements of nontronite negative layer charge versus structural Fe reduction. [•] Nontronite negative layer charge can decrease upon intense structural Fe reduction. [•] Tetrahedral iron strongly affects the clay redox behaviour. [•] A model quantifying negative layer charge increases upon moderate reduction. [ABSTRACT FROM AUTHOR]

We have successfully modified the synthesis of γ-Fe 2 O 3 and ZnO in a variety of potential matrices, like as multiwall carbon nanotubes (MWCNT) and graphene oxide (GO), referred to as FZ@MWCNT and FZ@MWCNT-GO. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed for phase formation and morphological analysis. Phase purity and superparamagnetic environment of maghemite and FZ@MWCNT were investigated by 57Fe Mössbauer spectrometry at 77 and 300 K, confirming the reduction of dipolar interaction. Induction heating of γ-Fe 2 O 3, FZ@MWCNT and FZ@MWCNT-GO was analysed at various concentrations of nanoparticles to investigate the suitability of this nanocomposite for hyperthermia application. Ironically, the inductive heating rate of FZ@MWCNT at 3 mg/ml concentration is reflecting its high potential for hyperthermia therapy in cancer treatment. [Display omitted] • γ-Fe 2 O 3 is prepared through an unconventional cost-effective technique. • π conjugate interaction of nanoparticles with that of the MWCNT surface i.e. magnetophoresis interaction bond is identified. • Mössbauer spectrometry at 77 and 300 K confirm the reduction of dipolar interaction to adopt the LRT theory. • Néel's relaxation makes the dominant position for hyperthermia. • Inductive heating rate of FZ@MWCNT reflects their high potential for hyperthermia therapy. [ABSTRACT FROM AUTHOR]

Co spinel ferrite nanoparticles were successfully prepared using a solvothermal route. Their structure, morphology and cationic distribution were studied by X-ray diffraction, Transmission Electron Microscopy and 57Fe Mössbauer Spectrometry. Though, their electric conductivity and dielectric relaxation were studied on nanostructured pellets resulting from the compaction of nanoparticles, by complex impedance spectroscopy in the frequency range 1–106 Hz from 25 up to 250 °C. The dielectric properties are investigated in detail. The presence of two thermally activated relaxation peaks in the modulus loss spectra confirms the contribution of grains and grain boundaries to the electrical behavior of the material. The main dielectric relaxation comportment and the conduction process are governed by the grain boundaries. Ac-conductivity, which deviates from the usual Universal Dielectric Response, can be described by a double power-law evidenced by a Nearly Constant Loss trend followed by a Super-Linear Power Law that decreases with increasing temperature. The change in the cationic distribution in CoFe 2 O 4 , deduced from the 57Fe Mössbauer spectra, may explain the observed trend in conductivity. The classical dielectric relaxation behavior is observed and very low values of permittivity are estimated. This compound can therefore be classified as an ultra-low-k dielectric. [Display omitted] • Cobalt ferrite nanoparticles prepared using a solvothermal method. • Non-Debye behavior of grain boundaries plays important role in dielectric response. • Ac-conductivity followed a Nearly Constant Loss trend then a Super-Linear Power Law. • Cation redistribution and size effect are responsible for electrical conductivity. • Cobalt ferrite considered as an ultra-low-k dielectric material. [ABSTRACT FROM AUTHOR]

• Density Functional Theory (DFT) is used to study the interaction between the metal and its support. • Palladium and palladium oxide deposition on Fe 3 O 4 (001) is accompanied with charge transfer from the metal host. • The charge transfer induces an increase in the Fe2+/Fe3+ ratio at the topmost surface of the support. • The charge transfer may be more efficient for palladium oxide but the resulting structure is thermodynamically unstable. Magnetic iron oxide particles decorated with transition-metal nanoparticles have become increasingly attractive in catalysis regarding the environment modifications, such as an additive ligand or carrier, which could significantly influence their performances. In this work, we used the Density Functional Theory (DFT) in the gradient approximation to study the interaction between the metal and its support for palladium and palladium oxide clusters on the surface of Fe 3 O 4 (001)magnetite. We report a dynamic process promoted by the palladium deposition with charge transfer from the metal host. An increase in the Fe2+/Fe3+ ratio at the topmost surface of the support was determined. The reduction of surface Fe3+ ions with electrons located at the interface has been proposed. Surprisingly, this slight increase in the surface density in Fe2+ ions was not observed in palladium oxide when the charge transfer from the support was significantly enhanced. Finally, the impact of the charge transfer process between the surface and the adsorbed species on palladium in terms of structure stability was discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

The effectiveness of amine-borane as reducing agent for the synthesis of iron nanoparticles has been investigated. Large (2-4 nm) Fe nanoparticles were obtained from [Fe{N(SiMe3)2}2]. Inclusion of boron in the nanoparticles is clearly evidenced by extended X-ray absorption fine structure spectroscopy and Mössbauer spectrometry. Furthermore, the reactivity of amine-borane and amino-borane complexes in the presence of pure Fe nanoparticles has been investigated. Dihydrogen evolution was observed in both cases, which suggests the potential of Fe nanoparticles to promote the release of dihydrogen from amine-borane and amino-borane moieties. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic nanoparticles prepared with iron oxides and N-benzyl-O-carboxymethylchitosan, an amphiphilic chitosan derivative, were prepared through the incorporation method and characterized by Fourier infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), Mössbauer spectroscopy, and magnetization measurements. The γ-Fe2O3 nanoparticles proved to be spherical and well crystallized, and some aggregation behavior was observed. The particles containing the polymer presented saturation magnetization of 18.4emug−1 and roughly superparamagnetic behavior. The material was used to adsorb three cationic dyes from aqueous solution (methylene blue, crystal violet, and malachite green). The adsorption process preferably followed the Langmuir–Freundlich isotherm and pseudo-second-order kinetic model. The removal of the dyes was optimized using a 32 factorial design, and the initial dye concentration proved to be more influential in dye adsorption than the temperature of the system. [Copyright &y& Elsevier]

Abstract: Biotite is a constituent Fe-bearing mineral of Delta subsoils in India and Bangladesh and has been hypothesized as a primary source of arsenic (As). The adsorption behavior of As onto structural Fe(II, III)-bearing biotite fractions (<50μm) was investigated in the pH range of 4–8 under a CO2-free, anoxic condition (O2 <1ppmv) using X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The batch experiments indicate that As adsorption is strongly pH dependent and that As(V) adsorbs more efficiently than As(III). X-ray Absorption Near-Edge Structure (XANES) spectra show no oxidation or reduction of As by biotite after reaction with As(III) or As(V) solutions for 3days. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopic results suggest that As(III) forms bidentate mononuclear edge-sharing (2E) and bidentate binuclear corner-sharing (2C) surface complexes at pH 7.7 as indicated by average As–Fe bond distances at 3.00±0.02Å and 3.37±0.03Å respectively. The surface speciation retrieved by XPS does not provide any evidence of reduction of As(V) on biotite after 30days further confirming the thermodynamic prediction and the XANES results. This study has therefore significant environmental implications for As contaminated areas, where biotite retards the release of As into reducing groundwater. The changes in soil redox conditions and weathering of biotite may likely contribute to the occurrence of high As in groundwater. [ABSTRACT FROM AUTHOR]

Abstract: It was reported the adsorption of As(III) on the surface of the chitosan-Fe-crosslinked complex. Theoretical correlation of the experimental equilibrium adsorption data for As(III)/Ch-Fe system is best explained by the non-linearized form Langmuir–Freundlich isotherm model. At optimum conditions, pH 9.0, the maximum adsorption capacity, calculated using the Langmuir–Freundlich isotherm model was 13.4mgg−1. The adsorption kinetics of As(III) onto Ch-Fe are described by the pseudo-first-order kinetic equation. The results of the Mössbauer spectroscopy showed that there is no redox process on the surface of the adsorbent. [ABSTRACT FROM AUTHOR]

Bisphosphonates BP molecules have shown to be efficient for coating superparamagnetic iron oxide particles. In order to clarify the respective roles of electrical charge and the length of the molecules, bisphosphonates with one or two ammonium moieties with an intermediate aliphatic group of 3, 5 or 7 carbons were synthesized and iron oxide nanoparticles coated. The evaluation on their iron core properties was made by transmission electron microscopy (TEM), nuclear magnetic relaxation dispersion (NMRD) profiles and Mössbauer spectra. The core size is close to 5 nm, with a global superparamagnetic behaviour modified by a paramagnetic Fe-based layer, probably due to surface crystal alteration. The hydrodynamic sizes increase slightly with aliphatic chain length (from 9.8 to 18.6 nm). The presence of one or two ammonium group(s) lowers the negative electrophoretic mobility up to bear zero values but reduces their colloidal stability. These BP-coated iron oxide nanoparticles are promising Magnetic Resonance Imaging (MRI) contrast agents. [ABSTRACT FROM AUTHOR]

Abstract: Iron and Sr bearing phases were thoroughly investigated by means of spectrometric and microscopic techniques in Callovian–Oxfordian (COX) samples originating from the ANDRA Underground Research Laboratory (URL) in Bure (France). Strontium was found to be essentially associated with celestite, whereas Fe was found to be distributed over a wide range of mineral phases. Iron was mainly present as Fe(II) in the studied samples (∼93% from Mössbauer results). Most of the Fe(II) was found to be in pyrite, sideroplesite/ankerite and clay minerals. Iron(III), if present, was associated with clay minerals (probably illite, illite-smectite mixed layer minerals and chlorite). No Fe(III) oxy(hydro)xide could be detected in the samples. Strontianite was not observed either. Based on these observations, it is likely that the COX porewater is in equilibrium with the following carbonate minerals, calcite, dolomite and ankerite/sideroplesite, but not with strontianite. It is shown that this equilibrium information can be combined with clay cation exchange composition information in order to give direct estimates or constraints on the solubility products of the carbonate minerals dolomite, siderite and strontianite. As a consequence, an experimental method was developed to retrieve the cation exchanged Fe(II) in very well preserved COX samples. The very homogeneous cation exchange composition of the formation is completely in agreement with a homogeneous presence of calcite and dolomite minerals whose equilibrium reactions control part of the porewater composition. Amongst the broad range of values available for dolomite solubility products in thermodynamic databases, the value of log K dolomite =−3.57 is the most appropriate for the one present in the COX formation. With regard to strontianite, it appears that the equilibrium constant tabulated in the Llnl database is not valid for natural clay systems. The value given by Busenberg et al. used by most of the other available thermodynamic databases seems to be far more appropriate. Concerning Fe(II) and siderite/ankerite equilibrium, the measured Fe/Ca ratio on the clay exchanger (∼0.01) could only be considered as a maximum value due to possible experimental bias, leading to the following constraint for the solubility of the sideroplesite phase present in the COX: Fe0.7Mg0.2Ca0.1CO3 +H+ 0.7 Fe2+ +0.2 Mg2+ +0.1 Ca2+ + logK sid_COX <0.42 This constraint is in agreement with the estimated solubility of this phase based on a solid solution model: log K sid_COX =0.23. [Copyright &y& Elsevier]

We present a potent pathway, (Nd, Pr)H x and Cu grain boundary engineering, to tackle the trade-offs between coercivity, remanence and corrosion resistance of Nd-Ce-Fe-B sintered magnets. Concurrent improvements of magnetic and corrosive properties are achieved in 25 wt% Ce-substituted magnet depending on the (Nd, Pr)H x /Cu ratio. A representative 8:2 ratio yields room-temperature magnetic performance (H cj = 14.1 kOe, B r = 12.88 kG, (BH) max = 39.4 MGOe) equivalent to that of N40M commercial-grade Nd-Fe-B, as well as superb thermal stability (coercivity coefficient | β | of 0.55%/K within the 293-413 K interval) and electrochemical resistance. These outstanding properties are closely correlated to the three notable microstructural characteristics, including (1) an increasing fraction of the REFe 2 phase with raised Cu content, (2) the occurrence of a new-type Cu-dissolved REFe 2 phase with higher Nd/Pr and lower Ce content than conventional 1:2 phase, and (3) a Cu-dissolved RE-rich phase with deficient Fe. Above structural and chemical features are discussed on the basis of experimental studies, which allow for better continuity of non-ferromagnetic grain boundary phase and higher chemical stability of intergranular regions, thus enabling a good compatibility of magnetic and anti-corrosive performance. Our exploration of (Nd, Pr)H x and Cu synergy may pave a novel way for developing high-figure-of-merit Nd-Ce-Fe-B permanent magnets that rival the commercial Nd-Fe-B counterpart. Image, graphical abstract [ABSTRACT FROM AUTHOR]

In the present study, nanocomposites (NCs) of activated carbon and iron oxide nanoparticles (NPs) in different w:w ratio were synthesized via. co-precipitation technique and evaluated for the removal of Cr (VI) ions. Detailed characterization of NCs was performed by FT-IR, XRD, BET, SEM-EDX, TEM and VSM analyses. The loading of NPs on activated carbon was evidenced from TEM images. Fe57 Mössbauer spectroscopy was used to identify the phase of iron oxide NPs and indicated the presence of hematite and goethite. The saturation magnetization values decreased with increasing activated carbon content and ranged from 14.4 to 28.1 emug−1. The composition of the nanocomposite was optimized for efficient Cr (VI) removal. The nanocomposite with 2:1 w:w ratio of activated carbon and NPs had the highest Cr (VI) removal efficiency, among synthesized nanocomposites and pristine NPs. The Langmuir model fitted the adsorption isotherms commendably. The maximum adsorption capacity of iron oxide NPs was 83.3, and it increased to 500.0 mgg−1 in nanocomposite with 2:1 ratio of activated carbon and Iron oxide NPs. The kinetic data was well described by pseudo-second order kinetic model. The thermodynamic analysis depicted spontaneous and exothermic nature of the adsorption process. The reducing characteristics of activated charcoal and the magnetic nature are important features of NCs for the removal of Cr (VI) ions, magnetic separation and regeneration. The results showed that optimizing the composition of activated charcoal-NPs nanocomposites served as an effective strategy for the removal of Cr (VI) ions. The ecotoxicity assessment showed that the synthesized nanocomposite is environmentally friendly. Image 1 • Composition of iron oxide loaded activated carbon nanocomposites was optimized. • Iron oxide phases fully characterized by Mössbauer analysis. • Composition was effectively tuned for Cr (VI) removal. • Composite effective as magnetically separable adsorbent for highly labile Cr (VI) ions. [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]

Presents a study which prepared composites from manganese-zirconium and iron or iron[sub25]nickel[sub75] nanostructured powders. Experimental details; Results and discussion; Conclusion.

Abstract: A study of La0.6Sr0.4− x MnTi x O3 (, 0.05, 0.1, 0.15, and 0.2) manganites with the Ti in B(=Mn)-position and vacancies in A(=La, Sr)-site is presented. The manganites belonged to the rhombohedral phase and small amount of Mn3O4 oxide was observed with increase of Ti content. X-ray adsorption fine structure (XAFS) analysis showed an appearance of Mn2+ ions in perovskite cell and tremendous change of local structure. We suppose that the change of local structure was mainly caused by the appearance of Mn ions in the A-positions and partially by the formation of vacancies in the above position with the increase of x-value. Curie temperature, , decreased drastically with x: and, . Further increase of Ti content changed the low-temperature magnetic state from the ferromagnetic to spin/cluster glass state. Effects of destruction of the electron pathway and change of local structure on Curie temperature, caused by the Ti doping, is discussed. [Copyright &y& Elsevier]