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The magnetoelastic effect is known as the dependence between the magnetic properties of the material and applied mechanical stress. The stress might not be applied directly but rather generated by the applied torque. This creates the possibility of developing a torque-sensing device based on the magnetoelastic effect. In this paper, the concept of an axially twisted toroidal magnetic core as a torque-sensing element is considered. Most known works in this field consider the utilization of an amorphous ribbon as the core material. However, Ni-Zn ferrites, exhibiting relatively high magnetostriction, also seem to be promising materials for magnetoelastic torque sensors. This paper introduces a theoretical description of the magnetoelastic effect under torque operation on the basis of total free energy analysis. The methodology of torque application to the toroidal core, utilized previously for coiled cores of amorphous ribbons, was successfully adapted for the bulk ferrite core. For the first time, the influence of torque on the magnetic properties of Ni-Zn ferrite was investigated in a wide range of magnetizing fields. The obtained magnetoelastic characteristics allowed the specification of the magnetoelastic torque sensitivity of the material and the determination of the optimal amplitude of the magnetizing field to maximize this parameter. High sensitivity, in comparison with previously studied amorphous alloys, and monotonic magnetoelastic characteristics indicate that the investigated Ni-Zn ferrite can be utilized in magnetoelastic torque sensors. As such, it can be used in torque-sensing applications required in mechanical engineering or civil engineering, like the evaluation of structural elements exposed to torsion. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract In this study, entanglement of composition, additive and/or sintering conditions and their effects on magnetic properties of soft ferrites, nickel zinc spinel ferrites (Ni1−xZnxFe2O4, x = 0.65 and 0.70) which were prepared via conventional solid-state reaction method investigated. Also an equiponderant calcined mixture of Bi2O3, CaO, CeO2, SiO2, Al2O3, Y2O3 and nanotitania was mixed thoroughly and used as a multi-compound calcined additive (MCCA). Calcined ferrite powders were crushed, dry and wet milled, dried, mixed with different amounts of MCCA (0.0, 0.5, 1.0, 1.5 and 2.0 wt%), formed in toroidal shapes and finally sintered at different temperatures, from 1150 up to 1360 °C for 3 h. X-ray diffraction assessment confirmed formation of the single phase cubic spinel structures. Initial permeability and Q-factor spectra of the toroids were obtained from 0.1 to 1000 kHz, using an LCR meter. The results show that initial permeability of each sample has a maximum and addition of MCCA to the ferrites leads to a marvelous increase in permeabilities. Additionally, MCCA decreases the optimum sintering temperature too. The optimum amounts of additive were 1.0 and 0.5 wt% for the x = 0.65 (μ′ = 492, Ts = 1280 °C) and x = 0.70 (μ′ = 478, Ts = 1320 °C), respectively. Permeability spectra illustrate that utility zone of the Ni0.35Zn0.65Fe2O4 and Ni0.3Zn0.7Fe2O4 are both less than 100 and 10 kHz, respectively. The results represent that there is a strong entanglement between composition, additive and/or sintering conditions. It can be concluded the MCCA added Ni0.35Zn0.65Fe2O4, is suitable for application in the switching power supplies.

In near-field communication (NFC) antennas, soft magnetic ferrites are usually applied as a substrate to reduce eddy current loss and increase magnetic field coupling. For this purpose, the applied ferrites are required to have high permeability and saturation magnetization together with low magnetic loss and dielectric loss. However, for most soft magnetic ferrites, it is difficult to meet all the requirements. Herein novel Ni–Zn ferrite ceramics co-doped by Ho3+ and Co2+ ions with chemical formula Ni0.5−xZn0.5Ho0.02CoxFe1.98O4 (x = 0–0.2) were designed and prepared to balance these needs on the basis of molten salt synthesis with metal nitrates as raw materials and potassium hydroxide (KOH) as the precipitation agent and molten salt precursor. After the substitution of Ho3+, the saturation magnetization and initial permeability decrease, but with further doping of Co2+, the saturation magnetization gradually increases, while the initial permeability continues to decrease. When x = 0.1, the sample will have the lowest dielectric constant, magnetic and dielectric loss, as well as the highest Curie temperature (305 ℃). Moreover, the acquired Ni–Zn ferrites have been applied simulatively in NFC antennas, revealing that the device manufactured with the optimal Ni0.4Zn0.5Ho0.02Co0.1Fe1.98O4 ferrite ceramics would have significantly improved performance at 13.56 MHz with low leakage and long transmit distance of magnetic field. Therefore, the Ni0.4Zn0.5Ho0.02Co0.1Fe1.98O4 ferrite ceramics would be a good candidate for NFC antenna substrates.

Highly effective electromagnetic (EM) wave absorber materials with strong reflection loss (RL) and a wide absorption bandwidth (EBW) in gigahertz (GHz) frequencies are crucial for advanced wireless applications and portable electronics. Traditional microwave absorbers lack magnetic loss and struggle with impedance matching, while ferrites are stable, exhibit excellent magnetic and dielectric losses, and offer better impedance matching. However, achieving the desired EBW in ferrites remains a challenge, necessitating further composition design. In this study, impedance matching is successfully enhanced and EBW in Ni–Zn ferrite is broadened by successive doping with Mn and Co , without incorporation of any polymer filler. It is found that Ni0.4Co0.1Zn0.5Fe1.9Mn0.1O4 material exhibits exceptional EM wave absorption, with a maximum RL of −48.7 dB. It also featured a significant EBW of 10.8 GHz, maintaining a 90% absorption rate (RL < −10 dB) for a thickness of 4.5 mm. These outstanding properties result from substantial magnetic losses and favorable impedance matching. These findings represent a significant step forward in the development of microwave absorber materials, addressing EM wave pollution concerns within GHz frequencies, including the frequency band used in popular 5G technology. [ABSTRACT FROM AUTHOR]

Electromagnetic interference has attracted much attention in various areas, due to its unfavorable properties that interrupt electronic devices and threaten human health. Ferrite composites have been proved to be effective materials to solve this problem. However, the electromagnetic properties of ferrite composites need to be enhanced. To improve the electromagnetic properties of ferrite composites, Ni-Zn Ferrite absorbents and diatomite/Ni-Zn ferrite composites were prepared by the sol–gel method in this work. The functional groups, phase composition, and surface morphology of the composites were analyzed by Fourier-transform infrared spectroscopy, XRD, SEM and vector network analysis, and the electromagnetic parameters were measured. The effects of temperatures (450°C, 550°C, 650°C, 750°C) and molar ratios of raw materials on the microstructure and microwave-absorbing properties of microwave-absorbing materials were studied. The results show that the metal ions were successfully loaded onto the diatomite, and that a large number of SiO2 characteristic peaks appeared in the XRD pattern. As the heat-treatment temperature is 650°C, the surface pore structure is covered by ferrite. The reflection loss of NixZn1−xFe2O4/diatomite reaches − 21.65 dB at 10.62 GHz when the heat-treatment temperature is 650°C. The absorption effect of NixZn1−xFe2O4/diatomite is better than that without diatomite. [ABSTRACT FROM AUTHOR]

The composites of expanded graphite (EG) and magnetic particles have good electromagnetic wave attenuation properties in the centimeter band, which is valuable in the field of radar wave interference. In this paper, a novel preparation method of Ni–Zn ferrite intercalated EG (NZF/EG) is provided in order to promote the insertion of Ni–Zn ferrite particles (NZF) into the interlayers of EG. The NZF/EG composite is in situ prepared via thermal treatment of Ni–Zn ferrite precursor intercalated graphite (NZFP/GICs) at 900 °C, where NZFP/GICs is obtained through chemical coprecipitation. The morphology and phase characterization demonstrate the successful cation intercalation and NZF generation in the interlayers of EG. Furthermore, the molecular dynamics simulation shows that the magnetic particles in the EG layers tend to disperse on the EG layers rather than aggregate into larger clusters under the synergy of van der Waals forces, repulsive force, and dragging force. The radar wave attenuation mechanism and performance of NZF/EG with different NZF ratios are analyzed and discussed in the range of 2–18 GHz. The NZF/EG with the NZF ratio at 0.5 shows the best radar wave attenuation ability due to the fact that the dielectric property of the graphite layers is well retained while the area of the heterogeneous interface is increased. Therefore, the as-prepared NZF/EG composites have potential application value in attenuating radar centimeter waves. [ABSTRACT FROM AUTHOR]

Thin films of Ni-Zn ferrite grown on MgO(111) single crystal substrate were prepared using radiofrequency magnetron sputtering, with a target of nominal composition Ni _0.5 Zn _0.5 Fe _2 O _4 . Subsequently, x-ray diffraction (XRD) was performed, which revealed characteristic reflections of a Ni-Zn ferrite structure, confirming the unique formation of the ferrite. X-ray photoelectron spectroscopy (XPS) revealed the presence of metal ions in their appropriate valence states within the crystalline structure of the Ni-Zn ferrite. The variation in binding energy observed in the thin film is attributed to changes in the environment of Fe ^3+ and Zn ^2+ or Ni ^2+ ions, resulting from the non-equilibrium distribution of cations in tetrahedral and octahedral sites. The saturation magnetization and the coercivity field were $7.05{\mu }_{{\rm{B}}}/{\rm{cell}}$ and 513 ± 32 Oe, respectively. In addition, ferromagnetic resonance studies were made using broad-band FMR spectroscopy based on a coplanar waveguide (CPW) spectrometer.

Herein, we report the influence of trivalent chromium (Cr3+) ion substitution on the electric, dielectric, and hyperfine interaction properties of a mixed Ni–Zn nanoferrite system synthesized by an auto combustion solution-gelation route. The XRD analysis verified the monophase nanocrystalline formation of prepared ferrites belonging to the spinel group with a cubic structure. TEM images displayed the sphere-like morphologies of the typical nanoferrite sample. FT-IR spectra uncover the occurrence of two absorption frequency bands in the desired region belonging to spinel ferrite. The magnetic parameters decreased significantly with increasing Cr3+ concentration. Mossbauer parameters, such as the hyperfine field, line-width, isomer shift and quadrupole splitting, were deduced for all the samples. DCR studies confirmed the semiconducting behavior of all the samples with an increasing resistivity trend after Cr3+ substitution. The dielectric study showed a decreasing trend with an increase in Cr3+ concentration. All the results display the influential substitution of Cr3+ ions in the Ni–Zn ferrite system, which shows the usability of the prepared samples in higher frequency ranging systems. [ABSTRACT FROM AUTHOR]

Cu substituted Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples is synthesized using the sol-gel auto-combustion process. They have a cubic spinel structure with crystallite size in the range of 29.01–42.68 nm. The increment in the copper content increases the DC conductivity. The electrical resistivity decrease with an increase in the temperature i.e. it has a negative temperature coefficient with resistance similar to semiconductors. The remnant ratios R obtained from VSM show their isotropic nature forming single domain ferrimagnetic particles. The results are compared with Ni0.5CuxZn0.5-xFe2O4 (x = 0 to 0.25). The resultant material Cu substituted Zn is more significant than that of Ni as indicated by its results and previous literature. BIBECHANA 19 (2022) 61-67

The mixing protocol effect was investigated in nanocomposites based on polyamide 6 (PA6) and maleic anhydride grafted ethylene‐propylene‐diene (EPDM‐MA), using Ni‐Zn ferrite as filler. The nanocomposites were processed using an internal mixer and specimens were injection molded. Compounds properties were investigated through Izod impact strength, tensile strength, x‐ray diffraction (XRD), magnetic measurements, differential scanning calorimetry (DSC), thermogravimetry (TG), heat deflection temperature (HDT), and scanning electron microscopy (SEM). PA6/EPDM‐MA mixture showed super‐tough behavior, with an increase of around 918% in impact strength, compared with PA6. However, there was a loss close to 50% in the elastic modulus and 5% in HDT, due to the high flexibility. In view of this, this mixture was selected for the production of nanocomposites toughened with Ni‐Zn ferrite, using three mixing sequences. When the nanocomposite was processed by the simultaneous mixing of all components (PA6/EPDM‐MA/Ni‐Zn), the highest impact strength (458 J/m) was reached, corresponding to a gain of 486%, compared with PA6. On the other hand, when Ni‐Zn ferrite and PA6 were initially premixed by melting, before EPDM‐MA addition in a second processing step, HDT and impact strength properties increased by 6% and 281%, in relation to PA6. In addition, the nanocomposites showed magnetic responses, with a soft material behavior, that is, they magnetize and demagnetize easily. In general, toughened and magnetic nanocomposites were produced, with good mechanical and thermal properties, displaying potential to produce magnetic films. [ABSTRACT FROM AUTHOR]

In search of efficient ways to produce biodiesel under environmentally friendly conditions, catalytic reactions have been explored with emphasis on replacing homogeneous by heterogeneous catalysis with the use of new catalyst types, such as the spinel ferrites, which are described as a viable option, since they are stable, highly active, inexpensive, reusable, and allow the easy recovery of the reaction medium through the application of magnetic fields. In this context, the present work proposes to contribute to the consolidation of the catalytic viability of the Ni0.5Zn0.5Fe2O4 system obtained by combustion reaction, because although previous studies indicate the catalytic effectiveness of this system in polyphasic form, the present work seeks as differential to evaluate the influence of the secondary phases and magnetization of the Ni-Zn system in the conversion to biodiesel, and for this purpose, it aims to evaluate the catalytic effect of ZnO formed as secondary phase and obtained concomitantly in the Ni-Zn ferrite synthesis, besides evaluating the effect of the stirring mechanism used in biodiesel production reaction by the ethyl transesterification of soybean oil. The synthesized Ni-Zn ferrites and ZnO sample were characterized by X-ray diffraction (XRD), nitrogen adsorption textural analysis (BET), particle size distribution, and then, tested in two reactor types, one with magnetic stirring, and another of mechanical stirring, to observe the magnetization effect of the material, and the characterization of the obtained biodiesels by gas chromatography (GC) and acidity index. The performed catalytic tests showed that the Ni-Zn ferrites promoted excellent ester conversions with values near and above 94%, thus confirming that although ZnO also promotes good ester conversion (83.9%), the catalytic effectiveness of the Ni-Zn ferrite is evident and independent of secondary phases. Moreover, the catalytic tests performed in the magnetic stirring reactor using the Ni-Zn ferrites as catalysts made it possible to realize that their magnetic properties may be interference in the catalytic effectiveness, being this, a more determining factor than the surface characteristics.

Magnetic and flexible nanocomposites of polyamide 6 (PA6)/styrene‐(ethylene‐butylene)‐styrene grafted with maleic anhydride (SEBS‐MA) were prepared using Ni‐Zn ferrite synthesized by combustion reaction. Thermal treatment was applied to the Ni‐Zn ferrite to form a more crystalline phase. The nanocomposites were processed in an internal mixer and later injection molded. The materials were characterized by torque rheometry, X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Izod impact strength, tensile strength, magnetic measurements, differential scanning calorimetry (DSC), thermogravimetry (TG), heat deflection temperature (HDT), and scanning electron microscopy (SEM). Ferrite calcination led to a higher degree of crystallinity and nanocomposites with a higher number of crystalline peaks. This favored a higher saturation magnetization. The magnetic hysteresis curves of the nanocomposites indicated a ferrimagnetic behavior. The impact strength and elongation at break increased significantly compared to neat PA6, suggesting the formation of flexible and magnetic nanocomposites. This behavior was ascribed to a chemical reaction between the terminal amine groups of PA6 and the maleic anhydride of SEBS‐MA, confirmed by FTIR and torque rheometry. Neat PA6 and the nanocomposites showed similar thermogravimetric, HDT, melting temperature, and crystallization properties. SEM results showed that the dispersed ferrite tends to form agglomerates, especially if calcined. In general, the addition of the non‐calcined Ni‐Zn ferrite to the PA6 matrix improved the mechanical properties. Conversely, the calcination of ferrite tended to improve the magnetic behavior of the nanocomposites. [ABSTRACT FROM AUTHOR]

Magnetic properties and structural analysis of Nd(Neodymium) doped Ni0.65Zn0.35Fe2O4 using XRD, Rietveld Analysis, FTIR Spectroscopy and VSM are reported. Confirmation of secondary phase formation with increased Nd content is established. Cation distribution for neodymium substituted nickel-zinc ferritesis proposed by considering the deficiency of Fe3+ in NiZnFe2O4 due to secondary phase formation of NdFeO3. The quality of present cation distribution was confirmed through close agreement of experimentally calculated lattice constant and Rietveld refinement. Changes in saturation magnetization with increased Nd content are explained on the basis of intensifying effect on energy exchange (inter-sublattice) between Ni-O-Nd and Ni-O-Fe concnerning Fe-O-Fe interaction, effect of replacing lower magnetic moment Nd3+ (3.62 μB) in place of Fe3+ (5 μB) and exchange developed between the cations existing at B-sites due to creation of oxygen vacancies. [ABSTRACT FROM AUTHOR]

Ni0.5Zn0.5Fe2O4 powders were prepared by a novel molten‐salt synthesis method. The effects of calcination processes of the powders on their sintering behaviors were investigated. Compared with the synthesis by traditional solid‐state reaction, the proposed molten‐salt method can significantly reduce the synthesis temperature of Ni0.5Zn0.5Fe2O4 from 800 to 550°C below, and the prepared powders have relatively high sintering activity at low temperature, which can thus decrease the sintering temperature. However, the abnormal growth of grains is easy to occur during sintering, thus resulting in uneven grain size. In particular, during the molten‐salt synthesis, the holding time for calcination is a dominant factor affecting the activity and crystallization degree of the resultant powders. From the point of view of increasing the density of sintered bodies, the optimal conditions for synthesizing Ni0.5Zn0.5Fe2O4 powder by the proposed molten‐salt synthesis is 400°C for 6 h. In addition, the saturate magnetization of the finally obtained ferrite ceramics has nothing to do with the preparation processes, while their coercivity depends on their densification and grain size caused by their different processing routes. [ABSTRACT FROM AUTHOR]

The present study aims to develop low magnetic anisotropy Ni-Zn nanoferrites with cobalt substitution. The results enable the development of nanoferrite samples with superior magnetic properties suitable for high-frequency core applications through an understanding of the influence of cobalt in the manipulation of the magnetic anisotropy of the nanoferrite. Ni0.65-xZn0.35CoxFe2O4 (x varies from 0.00 to 0.24 in steps of 0.04) particles were synthesized by sol–gel method using polyvinyl alcohol as a chelating agent. X-ray diffraction patterns of all the samples showed sharp peaks corresponding to spinel structure with no extra phases. Transmission electron micrographs depict uniform size distribution of particles in the range 185 to 247 nm. Magnetic properties were measured at 300 K and 5 K. Excellent control to reduce the magnetic anisotropy to a negligible amount can be achieved by incorporating minute amounts of cobalt in nickel-zinc ferrite. [ABSTRACT FROM AUTHOR]

Here, we are reporting electrical properties of Barium Titanate and Ni-Zn ferrite magneto-electric composites. Sr substituted barium titanate (BST = 90%) and MnO2 doped nickel zinc ferrite (NZF = 10%) were selected as individual phases for magneto-electric composite. Individual Ba0.9Sr0.1TiO3 and Ni0.8Zn0.2Fe2O4 were prepared separately through solid state reaction route. For structural analysis, the sintered samples subjected to X-ray diffraction reveal a presence of both the ferrite and ferroelectric phase in the composite sample. Dielectric properties were measured as a function of frequency and temperature. Curie temperature for pure BST was observed to be 92 °C, whereas in the composite sample, the transition became broader. P-E hysteresis loops were recorded at 20 Hz for all the samples. [ABSTRACT FROM AUTHOR]

Cu substituted Ni in Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) samples and Cu substituted Zn in Ni0.5Zn0.5−xCuxFe2O4 (x = 0, 0.05, 0.1, 0.15 and 0.2) is synthesized using the sol-gel auto-combustion process. Recently, we have carried out their structural analysis using XRD and FTIR and found a cubic spinel structure. In this paper, we have studied their morphological and compositional structure with the help of a Scanning Electron Microscope (SEM) attached with an Energy Dispersive Spectrometer (EDS). The comparative study shows that the grain size of Cu substituted Ni is greater than Cu substituted Zn in Ni-Zn ferrite. These smaller grain-sized ferrites are preferred for many microstructural applications. Depending on the available magnetic field, sintering temperature, and atmosphere, they can have different nucleation, and hence their application mode is different. They can have a critical concentration that can tune their properties. The EDS attached with the SEM confirmed the proper composition of samples. BIBECHANA 18 (2) (2020) 80-86

Ni-Zn ferrites are soft ferrites basically popular for high-frequency devices. They have low coercivity, low permeability, and higher resistivity. These properties have their own benefits on one hand but on the other hand, we can make them more efficient by doping suitable elements in order for tuning their properties for other applications. In this work, highly conducting Cu is used for substituting Ni in Ni-Zn ferrites and prepared Ni0.5-xCuxZn0.5Fe2O4 (x = 0, 0.05, 0.1, 0.15, and 0.2) samples using the sol-gel auto-combustion process. We have studied their resulting structural parameter using X-ray Powder Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy method and compared with that of Cu substituted Zn Ni-Zn ferrites. Their structures are found to be single-phase cubic spinel similar to that of Cu substituted Zn. The lattice constant increases with Cu concentration opposite to that at Zn substitution. Likewise, the size of the crystallites was not in monotonic change with the doping concentration in both cases due to internal strain and cation distribution. The difference in the pattern of XRD and FTIR of our samples indicate their different but significant properties. The changes in the structure show the effect of Cu doping and indicate the possible interesting changes in their electric, electronic, and magnetic properties. BIBECHANA 18 (1) (2021) 128-133

Polycrystalline Yb-substituted Ni-Zn nanoferrites with the compositions of Ni0.5Zn0.5YbxFe2-xO4 (x = 0.00, 0.04, 0.08, 0.12, 0.16 and 0.20) have been synthesized using sol–gel auto combustion technique. Single phase cubic spinel structure has been confirmed by the X-ray diffraction (XRD) patterns. Larger lattice constants of the compositions are found with increasing Yb3+ concentration while the average grain size (52–18 nm) has noticeable decrease as Yb3+ content is increased. The presence of all existing elements as well as the purity of the samples has also been confirmed from energy dispersive X-ray spectroscopic (EDS) analysis. Frequency dependent dielectric constant, dielectric loss, dielectric relaxation time, AC and DC resistivity of the compositions have also been examined at room temperature. The DC resistivity value is found in the order of 1010 Ω-cm which is at least four orders greater than the ferrites prepared by conventional method. This larger value of resistivity attributes due to very small grain size and successfully explained using the Verwey and deBoer hopping conduction model. The contribution of grain and grain boundary resistance has been elucidated using Nyquist/Cole-Cole plot. The study of temperature dependent DC resistivity confirms the semiconducting nature of all titled compositions wherein bandgap (optical) increases from 2.73 eV to 3.25 eV with the increase of Yb content. The high value of resistivity is of notable achievement for the compositions that make them a potential candidate for implication in the high frequency applications where reduction of eddy current loss is highly required.

The monodisperse Ni0.5Zn0.5Fe2O4 nanospheres have been synthesized via a simple solvothermal method. The effects of reactant concentration on structural and magnetic properties have been studied. X-ray diffraction analysis results indicate that the lattice constant and crystallite size can be tuned by controlling reactant concentration. The nanosphere size monotonically decreases from 238 to 35 nm with increasing reactant concentration. The magnetic studies show that blocking temperature is enhanced, and these single-domain particles are superparamagnetism at room temperature. The hollow nanospheres exhibit a high saturation magnetization value of 52.6 emu/g. The nanospheres with various diameters exhibit different magnetic saturation values which may be caused by the domain structure, surface effects and the distribution of metal ions on A and B sites. These superparamagnetic Ni0.5Zn0.5Fe2O4 nanospheres are expected to have potential application in biomedicine and magnetic fluid technology.

In search of efficient ways to produce biodiesel under environmentally friendly conditions, catalytic reactions have been explored with emphasis on replacing homogeneous by heterogeneous catalysis with the use of new catalyst types, such as the spinel ferrites, which are described as a viable option, since they are stable, highly active, inexpensive, reusable, and allow the easy recovery of the reaction medium through the application of magnetic fields. In this context, the present work proposes to contribute to the consolidation of the catalytic viability of the Ni 0.5 Zn 0.5 Fe 2 O 4 system obtained by combustion reaction, because although previous studies indicate the catalytic effectiveness of this system in polyphasic form, the present work seeks as differential to evaluate the influence of the secondary phases and magnetization of the Ni-Zn system in the conversion to biodiesel, and for this purpose, it aims to evaluate the catalytic effect of ZnO formed as secondary phase and obtained concomitantly in the Ni-Zn ferrite synthesis, besides evaluating the effect of the stirring mechanism used in biodiesel production reaction by the ethyl transesterification of soybean oil. The synthesized Ni-Zn ferrites and ZnO sample were characterized by X-ray diffraction (XRD), nitrogen adsorption textural analysis (BET), particle size distribution, and then, tested in two reactor types, one with magnetic stirring, and another of mechanical stirring, to observe the magnetization effect of the material, and the characterization of the obtained biodiesels by gas chromatography (GC) and acidity index. The performed catalytic tests showed that the Ni-Zn ferrites promoted excellent ester conversions with values near and above 94%, thus confirming that although ZnO also promotes good ester conversion (83.9%), the catalytic effectiveness of the Ni-Zn ferrite is evident and independent of secondary phases. Moreover, the catalytic tests performed in the magnetic stirring reactor using the Ni-Zn ferrites as catalysts made it possible to realize that their magnetic properties may be interference in the catalytic effectiveness, being this, a more determining factor than the surface characteristics. [ABSTRACT FROM AUTHOR]

Ni0.5Zn0.5Fe2O4 nanoparticles were synthesized by thermal decomposition method. The influence of reaction conditions such as the amount of the surfactant, refluxing temperature and time on the size, morphology and dispersibility was investigated. The structure, morphology and magnetic properties of the samples were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM) and vibrating sample magnetometry(VSM). The results indicate that increasing the amount of the surfactant is beneficial to obtain samples with smaller particle size and better dispersibility, and the improving refluxing temperature and extending refluxing time is beneficial to obtain samples with larger particle size, but with wider size distribution. The saturation magnetization of the sample is determined to be 49.38A·m2/kg, coercivity is 7143.20A/m and remanent magnetization is 5.76A·m2/kg with ferrimagnetic behavior at room temperature when the reaction condition is determined as follows, the amount of TOPO is 0.6mmol, the refluxing temperature is 260℃ and the refluxing time is 1h.

In the present work, series of Zn ion-doped Ni1−xZnxFe2O4 (0.0≤x≤0.5) ceramics were prepared by the double sintered solid-state reaction route to find out the influence of Zn2+ ions on the crystal structure, lattice structure and dielectric behavior of parent NiFe2O4. X-ray diffraction (XRD) study favors that all the prepared compounds belong to the cubic spinel structure. Lattice parameters found to have increasing value with increased Zn2+ ion substitution. The Raman scattering measurement discerns optical-active modes with blue shift as the doping increases. The dielectric constant (ε′) and dielectric tangent loss (tan δ) decrease with an increase in frequency and at higher frequency, both become constant. Dielectric parameters observe nonlinear behavior with increasing Zn2+ ion substitution. Room temperature dielectric constant of 10% Zn ion-doped NiFe2O4 [Ni0.9Zn0.1Fe2O4] is much higher as compared to other prepared ceramics. The room temperature ac conductivity is found to increase with increase in frequency and temperature-dependent ac conductivity increases with increase in temperature.

A series of diamagnetic aluminum (Al3+) substituted Ni-Zn Nanoferrites have been synthesized using sol-gel auto combustion route. Structural, magnetic, and dielectric properties were systematically studied and reported with respect to Al3+ substitution in host Fe3+ ions. X-ray diffraction (XRD) and infrared spectroscopy (IR) measurements confirm the presence of Al3+ ions at both A and B sites. Cation distribution proposed from XRD and IR correlates with magnetic and dielectric results. It is observed that Al3+ ions are distributed in to tetrahedral and octahedral sub-lattices. The saturation magnetization varies between 58.5 and 44.2 emu/g with increasing Al3+ substitution. This decrease in magnetization is ascribed to presence of the non-collinear spin (canted spin) structure in octahedral sub-lattice. Dielectric constant decreased and a significant improvement in AC resistivity is observed with Al3+ substitution. The observed variations are accounted on the basis of cation distribution in spinel ferrite. [ABSTRACT FROM AUTHOR]

Copyright of Revista Eletrônica de Materiais e Processos is the property of Revista Eletronica de Materiaia e Processos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High-performance inductive couplers require Ni-Zn ferrites of high saturation magnetization, Curie temperature, permeability and application frequency. However, for inductive couplers some of these properties run against each other in one ferrite. To balance these requirements, in this work, novel Ni-Zn ferrite ceramics co-doped by Ce3+ and Co2+ ions with chemical formula Ni 0.4 Zn 0.5 Co 0.1 Ce x Fe 2-x O 4 (x = 0–0.06) were designed and fabricated by a molten salt method. For the acquired ferrites, both Ce3+ and Co2+ ions could come into the lattices. The initially doped Co2+ ions would cause a slightly decreased grain size and dramatically reduced the specimen densification, but the further added Ce3+ ions could effectively inhibit the density reduction, while the grain size continues to dwindle. The additional Ce3+ ions would generate a foreign CeO 2 phase in the acquired specimens. The sole doping of Co2+ ions would aggrandize the saturation magnetization of ferrites, but the introduction of Ce3+ ions would cause its decrease. However, with an appropriate doping level, the Ce3+ and Co2+ ions co-doped ferrites could preserve a relatively high saturation magnetization, while the Curie temperature and cut-off frequency of the ferrites are dramatically augmented, although the permeability would be somewhat reduced. The as-acquired ferrites were simulated to apply in inductive couplers, revealing that the devices manufactured by the Ni 0.4 Zn 0.5 Co 0.1 Ce x Fe 2-x O 4 ferrites had significantly high maximum operating frequency, compared with that of the one manufactured by pure Ni 0.5 Zn 0.5 Fe 2 O 4 ferrite. [ABSTRACT FROM AUTHOR]

Abstract The present work investigated the effect of the addition of V 2 O 5 and MnCO 3 on the microstructure and magnetic properties of Ni-Zn ferrite ceramic samples prepared by a conventional ceramic sintering method at different temperatures. With this aim, a series of samples were prepared by varying the loadings of V 2 O 5 -MnCO 3 (un-doped, 0.4–0.1 wt%, 0.1–0.4 wt%, 0.2–0.3 wt%, 0.3–0.2 wt%, and 0.5–0.1 wt%, denoted as sample 1, sample 2, sample 3, sample 4, sample 5, and sample 6, respectively). The initial permeability and power loss of the different Ni-Zn ferrites were investigated with respect to the sintering temperature. The V 2 O 5 and MnCO 3 dopants significantly improved the initial permeability and power loss characteristics of the Ni-Zn ferrite at frequencies ≥0.5 MHz. When sintered at 1100 °C, sample 2 showed a maximum initial permeability of 931.23 H/m at a frequency of 1 MHz combined with a minimum power loss of 339.2 kW/m3. Co-doping with V 2 O 5 and MnCO 3 also resulted in the sintered samples with larger average grain sizes and higher density, while the sintering temperature of Ni-Zn ferrites was significantly reduced. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Calcium doped Ni–Zn ferrites having the nominal composition Ni 0. 6 Zn 0. 4 − x Ca x Fe 2 O 4 (x = 0, 0.1, 0.2, 0.3 and 0.4) are prepared via the conventional ceramic method at 1 2 5 0 ∘ C for 3 h to study their physical, electrical and dielectric properties at high frequencies which have extended their applications. The X-ray diffraction (XRD) and scanning electron microscope (SEM) have been used to characterize the microstructure and surface morphology of the prepared composition. XRD patterns reveal the formation of pure spinel phase ferrites whereas SEM micrographs display nonhomogeneous grains of polyhedral shape. The studies disclose that with increasing Ca content in spinel, the lattice parameter of the Ni–Zn ferrite increases and at the same time the grain boundary also increases. As a result of the increased boundary, the large grains could be trapped pores inside the grains which have affected the density, resistivity and dielectric constant of the sample. The DC electrical resistivity of the prepared sample decreases with the increase of Ca content. Also, the resistivity decreases with increasing the temperature. This increase in the conductivity with temperature must be regarded mainly as due to the thermally activated mobility of charge carriers, but not to a thermally activated creation of these carriers. The dielectric constant decreases with the increasing frequency following the Verway-de-Boer hopping mechanism. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fe particles were coated with a uniform (NiZn)Fe 2 O 4 via a co-precipitation method. • With the increase of heat treatment temperature, the O element in the boundary gradually penetrated into the Fe matrix. • With the increase of heat treatment temperature, the internal stress release of the sample is more complete. • The 450 °C argon-annealed sample had the optimum magnetic properties (u = 55.8, Pcv = 12.2 kw/m3, H c = 22.6 A/m). Abstract Fe/(NiZn)Fe 2 O 4 soft magnetic composites (SMCs) were prepared by the co-precipitation method using pure atomised iron powder and chloride as raw materials. The morphology and element content of coated powders were analysed using scanning electron microscopy and energy dispersive spectroscopy. Moreover, we used electron probe micro-analyser, X-ray diffraction and Raman spectrum to systematically investigate the effect of heat treatment temperature in argon on the microstructure of SMCs, including O element distribution, phase formation and internal stress. The results show that by increasing heated temperature, the oxygen content at the boundary of the SMCs increased and the internal stress release of SMCs was more complete. Moreover, non-magnetic FeO would be generated in SMCs when the heat treatment temperature reached 550 °C. We also discussed the relationship of heat treatment temperature and atmosphere with AC magnetic properties of the samples, including permeability, core loss and coercivity. The results indicate that the SMCs annealed at 450 °C in argon had the optimum magnetic performance (µ = 55.8, P cv = 12.2 kw/m3, H c = 22.6 A/m). At the heat treatment temperature of 500 °C, the argon-annealed samples presented better magnetic properties and higher frequency stability than air-annealed samples. [ABSTRACT FROM AUTHOR]

In the present work, series of Zn ion-doped Ni 1 − x ZnxFe2O4 (0. 0 ≤ x ≤ 0. 5) ceramics were prepared by the double sintered solid-state reaction route to find out the influence of Zn 2 + ions on the crystal structure, lattice structure and dielectric behavior of parent NiFe2O4. X-ray diffraction (XRD) study favors that all the prepared compounds belong to the cubic spinel structure. Lattice parameters found to have increasing value with increased Zn 2 + ion substitution. The Raman scattering measurement discerns optical-active modes with blue shift as the doping increases. The dielectric constant ( ε ′) and dielectric tangent loss (tan δ) decrease with an increase in frequency and at higher frequency, both become constant. Dielectric parameters observe nonlinear behavior with increasing Zn 2 + ion substitution. Room temperature dielectric constant of 10% Zn ion-doped NiFe2O4 [Ni 0. 9 Zn 0. 1 Fe2O4] is much higher as compared to other prepared ceramics. The room temperature ac conductivity is found to increase with increase in frequency and temperature-dependent ac conductivity increases with increase in temperature. [ABSTRACT FROM AUTHOR]

A simple hydrothermal method combined with microwave irradiation was used to synthesize nickel-zinc ferrite/coal-based carbon (Ni 1−x Zn x Fe 2 O 4 /CBC) composites. The influences of Zn2+ concentration on the magnetism and microwave absorption characteristics of Ni 1−x Zn x Fe 2 O 4 /coal-based carbon composites were examined. The Ni 1−x Zn x Fe 2 O 4 particles were equally anchored on the coal-based carbon within the Ni 1−x Zn x Fe 2 O 4 /CBC composites. The dielectric and magnetism characteristics of Ni 1−x Zn x Fe 2 O 4 /CBC composites can be improved simultaneously by adjusting the Zn2+ concentration. The minimum reflection loss (RLmin) for the sample at x = 0.4 is −65.5 dB for a thickness of 4.0 mm. The samples also have typical soft magnetic properties. Furthermore, some possible mechanisms of microwave absorption are investigated. Our Ni 1−x Zn x Fe 2 O 4 /CBC composites show great potential for microwave absorption applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• EM absorbing properties of NZF (1- x)–BT(x)–epoxy composites have been investigated. • The addition of BT effectively adjusts EM wave absorption frequencies within 1–4 GHz. • The composite with × = 0.4 showed remarkable EM wave absorption performance with RL of −70 dB. Composites consisting of ferrimagnetic spinel ferrite Ni 0.5 Zn 0.5 Fe 2 O 4 (ZNF) and ferroelectric BaTiO 3 (BT) powders embedded in epoxy (10 wt%) were synthesized and analyzed for their electromagnetic (EM) wave absorption properties. The ZNF and BT powders were combined in weight ratios of 1- x : x , where x = 0, 0.1, 0.2, 0.3, 0.4, and 1.0. With increasing x , the height of the complex permittivity (ε′ and ε″) spectra increased, while the height of the complex permeability (μ′ and μ″) spectra gradually decreased. The reflection loss (RL) value, indicative of EM absorption efficiency, was calculated using measured ε′, ε″, μ′, and μ″ data. Apart from the BT–epoxy sample (x = 1.0), which exhibited no magnetic loss mechanisms, the EM wave absorption characteristics in the NZF-BT-epoxy composites were predominantly influenced by magnetic loss mechanisms, as reflected in the μ″ values. The incorporation of BT modified the impedance matching conditions, causing the frequency at which maximum EM wave absorption indicated by the minimum RL (RL min) occurs to shift to lower frequencies. The most remarkable EM wave absorption performance was observed for the sample with x = 0.4, where RL min reached −70 dB. Notably, the samples with x values ranging from 0 to 0.4 demonstrated outstanding EM wave absorption capabilities within the radar frequency range of L and S-bands (1–4 GHz). Furthermore, the EM wave absorption bandwidth (Δ f), representing the frequency range where RL < -10 dB, was 8.3 GHz (4.5–12.8 GHz) for the x = 0 sample. However, this bandwidth decreased to 2.6 GHz (5.0–7.6 GHz) for the x = 0.4 sample. Although the addition of BT led to a reduction in the EM wave absorption bandwidth compared to the NZF–epoxy composite (x = 0), it enabled the tuning of the absorption band towards lower frequencies, particularly emphasizing excellent EM wave absorption in the L-band. [ABSTRACT FROM AUTHOR]

The monodisperse Ni0.5Zn0.5Fe2O4 nanospheres have been synthesized via a simple solvothermal method. The effects of reactant concentration on structural and magnetic properties have been studied. X-ray diffraction analysis results indicate that the lattice constant and crystallite size can be tuned by controlling reactant concentration. The nanosphere size monotonically decreases from 238 to 35 nm with increasing reactant concentration. The magnetic studies show that blocking temperature is enhanced, and these single-domain particles are superparamagnetism at room temperature. The hollow nanospheres exhibit a high saturation magnetization value of 52.6 emu/g. The nanospheres with various diameters exhibit different magnetic saturation values which may be caused by the domain structure, surface effects and the distribution of metal ions on A and B sites. These superparamagnetic Ni0.5Zn0.5Fe2O4 nanospheres are expected to have potential application in biomedicine and magnetic fluid technology. [ABSTRACT FROM AUTHOR]

Highlights • The sol-gel method has been proved in producing nanoparticles of size less than 15 nm. • The role of chelating agent, PEG is powerful in controlling the particle size. • The investigation establishes the impact of iron content on sintering temperature. • The magnetic properties are very sensitive to the iron content present in the composition. • High saturation magnetization (91.9 emu/g) has been achieved in Ni 0.60 Zn 0.35 Fe 2.05 O 4. Abstract Ni-Zn ferrite nanoparticles of smaller particle size and high saturation magnetization have gained a special attention for their use in biomedical applications. The development of such nanoparticles requires rigorous processing conditions in arriving at desired characteristics. Ni-Zn ferrite nanoparticles of three different compositions Ni 0.65 Zn 0.35 Fe 2 O 4 , Ni 0.65 Zn 0.40 Fe 1.95 O 4 and Ni 0.60 Zn 0.35 Fe 2.05 O 4 containing varying amounts of iron concentration 50.00 mol%, 48.75 mol%, and 51.25 mol% respectively were processed by the sol-gel method using polyethylene glycol (PEG) as a chelating agent and characterized by techniques X-ray diffraction, Transmission electron microscopy, field emission scanning electron microscopy and Fourier transform infrared spectroscopy in elucidating the structural parameters. Ferrite compositions containing lower and higher iron content require the lower annealing temperature to produce higher saturation magnetization as compared to the stoichiometric composition. The composition of lower iron content favoured smaller particle size of 9 nm, while the material of higher iron content showed enhanced saturation magnetization of 91.9 emu/g. From the knowledge of literature and our previous works, it is opined that no other chelating agent than PEG proved to be an efficient one in controlling the particle size and improving the microstructure. [ABSTRACT FROM AUTHOR]

Abstract The Ni 0.5- x Mo x Zn 0.5 Fe 2 O 4 (x = 0.00, 0.005, 0.01, 0.015 and 0.02) ferrites have been synthesized by the sol-gel auto-combustion method. The crystal structure, surface morphology, magnetic properties, and cation distribution of the ferrites have been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The lattice parameter initially decreases and then sharply increases. According to the analysis of SEM and magnetic properties, there is the second phase NiO existing in the sample of x = 0.02. Cation distribution estimated from XRD, SEM and magnetic properties analyses suggests that Mo6+ ions occupy the tetrahedral sites, and more and more Fe2+ ions appear in the samples with the addition of Mo content. The saturation magnetization (M s) and initial permeability (μ i) of samples increase firstly, and then sharply decrease with increasing Mo6+ content from x = 0.005 to x = 0.02. The Ni 0.485 Zn 0.5 Mo 0.015 Fe 2 O 4 ferrite has the maximum M s of 82.2 emu/g and μ i of 86. Meanwhile, it presents the best microstructure, the largest bulk density and the lowest porosity. [ABSTRACT FROM AUTHOR]

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Lithium-doped nickel-zinc ferrite compound with formula Ni0.8Zn0.2−2xLixFe2+xO4 (x = 0, 0.01, 0.03, 0.05) was prepared using the sol-gel technique. The results of XRD proved a cubic spinel system of crystal. The lattice parameters, average particle sizes, and crystal density were calculated. It was found that the distance between magnetic ions decreases with lithium concentration and crystal density values ranging from 5.3 to 5.2 g/cm3. SEM and AFM show the lithium substitution effect on the morphology of the samples. The saturation magnetization (Ms) and coercivity (Hc) of Ni0.8Zn0.2−2xLixFe2+xO4 increase with an increasing content of Li1+ ion, where x is equal to 0, 0.01, 0.03, and 0.05. The Ms and Hc increase from 52 to 65 emu/g and from 99 to 119 Oe, respectively. The squareness ratio (Mr/Ms) appeared at a maximum value of x = 0.01. [ABSTRACT FROM AUTHOR]

Sol-gel method has been employed to prepare Ni-Zn ferrite with chemical formula Ni1-xZnxFe2O4 where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5. The structural Ni-Zn ferrite was studied via the X-ray diffractometer (XRD) pattern. X-ray analysis showed that there is a small shift in peaks towards shorter angles which increases with the concentration of zinc. Experimental values of lattice constant was varied from 8.34 of Ni ferrite to 8.397nm for Ni-Zn ferrite. The crystallite size of Ni ferrite was 83nm which is decreasing with substituted Zn to it and became 43nm at 4 x = 0.5. Therefore, the superparamagnetic behavior appears with substitution of Zn to Ni ferrite. The saturation magnetization, remiensis, coersivity, magnetic moment and anisotropy constant were calculated according to hysteresis loop using the result of vibrating sample magnetometer (VSM). The effect of cation distribution appeared clearly through the saturation magnetization value which was 46.8 emu/gm for nickel ferrite and increased to an optimum value (59.64 emu/gm) at x = 0.3. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successfully developed Ni 0.6-x Zn 0.4 Co x Fe 2 O 4 (x = 0, 0.033, 0.066, 0.132, 0.264 and 0.528) nanoferrites via a novel hybrid non-aqueous approach. • The produced nanoparticles have spinel cubic phase at various cobalt concentrations, x = 0.033, 0.066 and 0.528. • M6 specimen attained the highest maximum saturation magnetization and coercivity of 37.09 emu/g and 108.85 Oe. • Cation distributions validates our theoretical and experimental investigations to a great extent. • M2 and M6 sample shows high ZOI against both Bacillus subtilis and Escherichia coli. Ni-Zn spinel nanoferrite with a composition Ni 0.6-x Zn 0.4 Co x Fe 2 O 4 (x = 0.00, 0.033, 0.066, 0.132, 0.264 and 0.528) was produced at a low reaction temperature using a novel hybrid direct non-aqueous approach that eliminates the need for a complexing agent and a precursor that adjusts pH. The developed Ni 0.567 Zn 0.4 Co 0.033 Fe 2 O 4 (x = 0.033), Ni 0.534 Zn 0.4 Co 0.066 Fe 2 O 4 (x = 0.066) and Ni 0.072 Zn 0.4 Co 0.528 Fe 2 O 4 (x = 0.528) nanoferrites attains the single-phase spinel cubic nano symmetry with a crystallite size of 54.91, 47.55, and 48.98 nm, respectively. Spherical shaped nanoparticles with aggregated behaviour were confirmed for the produced nanoferrites. XPS spectra of Ni 0.072 Zn 0.4 Co 0.528 Fe 2 O 4 nanoferrite confirms the detection of major photoemission peaks of Zn2p, Ni2p, Co2p, Fe2p, O1s, and C1s. According to the BET research investigation, Ni 0.072 Zn 0.4 Co 0.528 Fe 2 O 4 nanoferrite having specific surface area of 2.309 m2/g. The highest saturation magnetization and coercivity of 37.09 emu/g and 108.85 Oe was attained at higher doping content of cobalt (x = 0.528). With this nano crystalline nature and excellent magnetic factors, the developed nanoferrites are highly beneficial for the recording media applications to get the suitable signal to noise ratio and also, for multi-layer chip inductors (MLCIs). From the antibacterial investigation, it was observed that the produced Co doped Ni-Zn ferrites (x = 0.033, 0.264) shows high zone of inhibition (ZOI) for E. coli and Bacillus subtilis but the rest of the samples (x = 0.0, 0.066, 0.132, 0.528) shows no ZOI for both the bacterial strains. Therefore, the prepared Co doped Ni-Zn nanoferrites also works as superior antibacterial agent for biological application. [ABSTRACT FROM AUTHOR]

Ni-Zn ferrites with a nominal composition of Ni 0.5 Zn 0.5 Ho x Fe 2- x O 4 ( x = 0–0.06) were prepared by conventional solid state reaction through using analytical-grade metal oxides powders as raw materials. The phase composition, microstructure, magnetic properties and dielectric performance of the as-prepared samples were investigated. The doped Ho 3+ ions could enter into the crystal lattice of the resultant spinel ferrites, causing the expansion of the unit cell, reaching a saturated state when x = 0.015; and the additional Ho 3+ ions would form a foreign HoFeO 3 phase at the grain boundary. The grain size and densification of the samples initially decreased after a small amount of Ho 3+ ions was doped, but then increased with more Ho 3+ ions added. The saturation magnetization decreased gradually with increasing substitution level of Ho 3+ ions. The Curie temperature and coercivity raised initially and declined later with increasing content of Ho 3+ ions in the samples, reaching their maximums of 305 °C with x = 0.015 and 2.99 Oe with x = 0.03, respectively. The variation of complex permeability versus Ho 3+ ions substitution level presented an opposite trend to that of coercivity. The dielectric loss increased slightly after the introduction of a small amount of Ho 3+ ions, but reduced significantly with more Ho 3+ ions doped. [ABSTRACT FROM AUTHOR]

Ni-Zn ferrite nanoparticles were synthesized via mechanical activation of Zn, NiO and Fe 2 O 3 powders in a high energy planetary ball mill. The 30 h-milled samples in argon, oxygen and air atmospheres were pressed in pellet and toroid shape form and were sintered from 500 °C to 900 °C with 100 °C increments. The X-ray diffraction patterns results indicated a single phase Ni-Zn ferrite formation with a cubic-spinel structure in all the samples sintered at 500 °C. The milling atmosphere had a key role in the synthesis, microstructure and properties of the samples in such a way that this effect sustained even after the completion of sintering process. Thus, the main goal of this study is to scrutinize the effect of sintering temperature in the 30-h-milled samples in different atmospheres on DC electrical resistivity and dielectric behavior of Ni-Zn ferrite samples. The results indicated that although electrical resistivity decreased, dielectric behaviors, i.e. constant, loss and tan δ increased with increase in sintering temperature. The milled samples in argon had the highest resistivity of 1.2 × 10 6 Ωcm at 500 °C, and lowest dielectric constant and loss ( ∼ 4.67 × 10 2 and 1.7 at 300 K and frequency 10 6 MHz, respectively) compared to other samples owing to more homogeneity and smaller average crystallite size, making them a good candidate for high frequency applications. X-ray photoelectron spectroscopy (XPS) revealed the presence of metal ions in their proper valence in the Ni-Zn ferrite crystal structure. Noticeably, a variation in the binding energy for the milled samples in different atmospheres is attributed to the changes in surroundings of Fe 3+ and Zn 2+ /or Ni 2+ , due to non-equilibrium distribution of cations in tetrahedral and octahedral sites, which is further confirmed by the XRD patterns. [ABSTRACT FROM AUTHOR]

Asphalt-based composites have the ability to heal themselves. Under certain conditions, strength and stiffness modulus can be restored so that the fatigue life can be extended. However, without the aid of external influences (energy supply or material supplement), the self-healing ability of asphalt mixture is quite limited. In this paper, the efficiency of self-healing of asphalt mixture with Ni-Zn ferrite powders was analyzed based on the concept of microwave heating. The recovery rate of stiffness modulus and the fatigue life extension ratio were adopted to evaluate the self-healing efficiency of asphalt mixture. Different influence factors, such as heating temperature, healing time and damage level, were analyzed in this study. The analysis results proved that Ni-Zn ferrite powders can promote the self-healing ability of asphalt mixture significantly. It is found that when the asphalt mixture is filled with 80% ferrite powders (volume fraction of mineral powders), under the condition of healing for 3 h after heating to 55 °C by microwave, the fatigue life extension ratio of 50% damaged ferrite-filled asphalt mixture can reach 1.33. [ABSTRACT FROM AUTHOR]

Rare-earth ions (RE)-doped Ni-Zn ferrite nanoparticles with a structural formula of NiZnFeREO (RE = Nd, Ce, La and Pr) were synthesized at room temperature by a sol-gel auto-combustion method. The structural and magnetic properties of Ni-Zn ferrite samples were carried out by XRD, vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FE-SEM) and FT-IR spectroscopy. XRD pattern of Ni-Zn ferrite revealed that all the diffraction planes are in agreement with cubic spinel phase and the addition of FeO phase was also observed. In the case of RE ions-doped Ni-Zn ferrite in addition to the FeO phase, very low intensity peaks corresponding to some secondary phase are also present. The average crystallite sizes were found to be from 42 to 56 nm using the Scherer formula. The lattice constant ( a) values are gradually decreased from 8.378 to 8.349 Å with different substitutions of RE ions in the Ni-Zn ferrite samples. VSM analysis revealed that saturation magnetization values are decreased and coercivity values are increased with substitution of different RE ions. FE-SEM images exhibits that particles are spherical in shape. FT-IR interpretation revealed that two main metal oxygen bands (564 and 411 cm) are observed in all the substituted Ni-Zn ferrite samples. [ABSTRACT FROM AUTHOR]

Purpose The present communication aims to investigate the influence of cobalt substitution on the structural, mechanical and elastic properties of nickel–zinc ferrite thick films. The changes observed in the crystallite size (D), lattice constant (a), texture coefficient [TC(hkl)] and mechanical and elastic properties of the thick films due to cobalt substitution have been reported systematically.Design/methodology/approach Ni–Zn ferrites with the stoichiometric formula Ni0.7−xCoxZn0.3Fe2O4 (where, x = 0, 0.04, 0.08, 0.12, 0.16 and 0.20) were synthesized via solution combustion technique using sucrose as the fuel and poly-vinyl-alcohol as the matrix material. The thick films of the ferrites were fabricated on alumina substrates by the screen printing method. The thickness of the films was 25 μm, as measured by the gravimetric method. The thick films were subjected to X-ray diffraction and Fourier transform infrared spectroscopy.Findings The detailed study of variation of lattice parameter (a), sintering density, micro-strain and elastic properties with cobalt (Co+2) substituted was carried out. The remarkable increase in lattice parameter (from 8.369 A° to 8.3825 A°), bulk density and average grain size (69-119 nm) with the cobalt content was due to larger ionic radius of Co2+ compared to Ni2+. Texture analysis [TC(hkl)] reveals all thick films have adequate grain growth in the (311) plane direction. The main absorption bands of spinel ferrite have appeared through infrared absorption spectra recorded in the range of 300-700 cm−1.Originality/value The variation in stiffness constants (for isotropic material, C11 = C12), longitudinal elastic wave (Vl), transverse elastic wave (Vt), mean elastic velocity (VMean), rigidity modulus (G), Poisson’s ratio(s) and Young’s modulus (E) with cobalt (Co+2) composition has been interpreted in terms of binding forces found. [ABSTRACT FROM AUTHOR]