Barium Ferrite Research Articles

Synthesis and Characterization of Ternary Polyaniline/Barium Ferrite/Reduced Graphene Oxide Composite as Microwave-Absorbing Material

A microwave-absorbing composite with polyaniline (PANI), barium ferrite (BaFe12O19) and reduced graphene oxide (rGO) by co-precipitation and in situ polymerization is presented, consisting of three different microwave-absorbing materials. The structure characterization, the microstructure of the fabricated composites and their related thermal and microwave absorption properties have been investigated. The thermogravimetric analysis and vector network analyzer measurements indicated that both the thermal stabilities and the microwave-absorption properties of this ternary composite were significantly enhanced due to the synergistic effects of PANI, BaFe12O19 and rGO. The minimum reflection loss of PANI/BaFe12O19/rGO was − 22.05 dB at 8.6 GHz, and the effective microwave-absorption bandwidth for reflection loss below − 10 dB was 0.9 GHz from 8.2 GHz to 9.1 GHz with the thickness of 2.6 mm. The improved microwave-absorption properties could be mainly due to the impedance matching by integration of dielectric loss and magnetic loss, and interfacial polarization between the three components. The remarkable microwave-absorption properties suggests its promising application for microwave absorption.

Smart elastomeric hydrogel of polyacrylamide containing nanosized barium ferrite and graphene oxide

Smart elastomeric hydrogels based on polyacrylamide containing ferrimagnetic nanoparticles of BaFe12O19 alone or a combination of BaFe12O19 and graphene oxide were synthesized. An improvised sample preparation technique was evolved to design actuators, where the hydrogel samples in rolls form were inserted into cut pieces of hard plastic sleeve in order to fabricate a lab-level actuator. The magneto-responsive actuation behaviour was measured by applying an external magnetic field with the help of a hand-held square type of NdFeB magnet. While the sample containing only 20 wt% BaFe12O19 exhibited only 15 mm deflection at threshold magnetic field of 28 mT, the deflection was significantly enhanced up to 23 mm for the sample containing 1 wt% GO and 20 wt% BaFe12O19 at a threshold magnetic field of 36.7 mT. Up to 20 wt% BaFe12O19, the hydrogels showed a heterogeneous dispersion of large-sized BaFe12O19 clusters and addition of a small percentage, e.g. 1% of GO resulted in significant improvement in the homogeneity of dispersion as well as reduction of the scale of the BaFe12O19 clusters. The saturation magnetization value of the hydrogels was also improved by 50–75% due to the addition of 1 wt% GO with 20 wt% BaFe12O19.

Reaction schemes of barium ferrite in biomass chemical looping gasification for hydrogen-enriched syngas generation via an outer-inner looping redox reaction mechanism

Abstract The objective of this study was to build an efficient outer-inner looping redox reaction mechanism called steam recycled biomass chemical looping gasification (SR-BCLG) for H2 production by using BaFe2O4 as an oxygen carrier (OC). The X-ray diffraction (XRD) results showed the phase changes of BaFe2O4 in the SR-BCLG process can be oxidized to its initial state stimulated by steam. In addition, the impacts on the temperature, water injection rate (steam/biomass ratio) and OC loading were investigated. The maximum H2 production of 28.5 mol/kg· biomass was achieved in the 60 min of gasification with a BaFe2O4 load amount of 10 wt%, which is an increase in H2 production of 109.6% compared with the no-OC biomass gasification process under the optimal conditions. Durative high production of H2-enriched syngas was obtained during the cyclic stability tests, indicating the significant redox durability and high H2-generation properties of BaFe2O4. The XRD, scanning electron microscopy (SEM), and thermo-gravimetric analyzer (TG) characterizations revealed the high stability of BaFe2O4, which can be ascribed to the existence of Ba2+. The bimetal functional BaFe2O4 allows for an innovative method of outer-inner looping redox reactions for continuous H2-enriched syngas generation in the SR-BCLG process.

Physical and mechanical properties of microwave absorber material containing micro and nano barium ferrite

Physical and mechanical properties of microwave absorber material containing micro and nano barium ferrite

A superior microwave absorption material: Ni2+-Zr4+ Co-Doped barium ferrite ceramics with large reflection loss and broad bandwidth

Large reflection loss and wide bandwidth are significant targets, determining the microwave absorption ability. However, it is still a challenge to simultaneously satisfy the two conditions. As a multifunctional material, BaFe12O19 possess excellent electromagnetic properties in the microwave frequency band. Due to the natural resonance phenomenon of the material, BaFe12O19 can produce a large magnetic loss which correlates with Fe3+ content, and the microwave absorption characteristics of barium ferrite can be modulated by ion doping. As a typical magnetic metal, Ni coupled with high-valence state Zr4+ doping helps to produce double resonance peaks. In this work, Ni2+-Zr4+ co-doping M-type barium ferrites (BaFe12-2xNixZrxO19, BNZFO-x, x = 0–0.8) were prepared conveniently by solid-state reaction method. Several necessary measurements to characterize its microwave absorption property have been operated such as morphology, magnetic performance and electromagnetic parameters. The results show that reflection loss and bandwidth can be simply tuned by tailoring Ni2+-Zr4+ content. The reflection loss peak drifts from 18 GHz to 9.76 GHz, which involves a half of the studied frequency range. The maximum reflection loss achieves −60.6 dB and the corresponding bandwidth over −10 dB is 7.68 GHz for BNZFO-0.6 ceramic with only 2.1 mm thickness. Thus, the doping of Ni2+-Zr4+ ion pairs is beneficial to improve the absorbing properties of the material, and the superior microwave absorption property may originate from its inner double natural resonance in micro-scale. The excellent microwave absorption properties suggest that BNZFO-x is a promising candidate applied for designing electromagnetic shielding devices.

Measurement of effective magnetic anisotropy field and ferromagnetic resonance bandwidth at ferromagnetic resonance frequency in magnetically uniaxial hexagonal ferrites

In this work we have considered metrological problems and measurement of magnetic parameters and presented methods of measuring effective magnetic anisotropy field HAeff and ferromagnetic resonance bandwidth ∆H in magnetically uniaxial hexagonal ferrites in the electromagnetic microwave working frequency range. The methods allow measuring HAeff in the 10–23 and 28–40 kE ranges and ∆H in the 0.5–5.0 range. One method (suitable for wavelength measurements in free space in the 3-mm wavelength range) has been implemented for the 78.33–118.1 GHz range. The other method (based on the use of microstrip transmission lines) has been implemented for the 25–67 GHz range. The methods have been tested for polycrystalline specimens of hexagonal barium and strontium ferrites with nominal composition or complex substituted and having high magnetic texture. The measurement results have been compared with those obtained using conventional measurement methods and spherical specimens. Our methods prove to be highly accurate and reliable.

Barium Ferrite Magnetic Nanoparticles Labeled with 223Ra: A New Potential Radiobioconjugate for Targeted Alpha Therapy and Magnetic Hyperthermia

Barium Ferrite Magnetic Nanoparticles Labeled with 223Ra: A New Potential Radiobioconjugate for Targeted Alpha Therapy and Magnetic Hyperthermia

Microstructure and magnetic properties of Y substituted M-type hexaferrite BaYxFe12−xO19

Y (yttrium)-substituted M-type hexaferrite of composition BaYxFe12−xO19 (x ranges from 0.1 to 0.8 with step of 0.1) was synthesized through ceramic process. Pure phase formation of M-type hexaferrite was confirmed by XRD patterns for prepared sample when x < 0.4. The second phase (Y3Fe5O12) was detected when the substitution content exceeded 0.4. As the substitution dosage of yttrium increased, unconspicuous transform were observed in the microstructure of all samples BaFe12−xYxO19, such as compactness, size of grain. The bulk densities (ρ) of the samples decreased first and then increased with the increase of X. It means that the compactness of the sample receded first and then enhanced with rise of Y3+ substitution contents. Moreover, with increase of Y3+ amount, Y3+ substituted the Fe3+ in the octahedral position of m-type barium ferrite, the saturation magnetization (Ms) of the sample decreases rapidly and obtained a minimum of 55.63 emu/g, and then increased gradually attributed to the appearance of the second phase (Y3Fe5O12). Appropriate values of Ms (56.57 emu/g) and Hc (1794.17 Oe) were obtained simultaneously when x = 0.6. These two characters made the material suitable for the applications infield of magnetic recording.

Bi2O3 adjusting equivalent permeability and permittivity of M-type barium ferrite for antenna substrate application

In this paper, Co-Ti doped M-type barium ferrite [Ba(CoTi)1.22Fe9.56O19] was prepared at low temperature (925 °C) in O2 atmosphere with different amounts of Bi2O3 sintering additive (x = 5–14 wt%). XRD showed superfluous Bi2O3 additive led to BiFeO3 phase formation, which is the important factor to adjust properties of material. SEM revealed that the grain size diminished gradually. For magnetic and dielectric properties, with different amounts of Bi2O3, saturation magnetization (Ms) decreased and coercivity (Hc) gradually increased. Complex magnetic permeability and dielectric permittivity presented excellent regularity, and the equivalent permeability and permittivity were obtained when x = 5 wt%. At x = 5 wt%, the real part of permeability (μ′) and permittivity (ε′) were about 18.3 at a range of 10 MHz–1.0 GHz, the magnetic loss (tan δμ) was about 3.4 × 10−2, and the dielectric loss (tan δε) was about 2.8 × 10−3. It showed that Bi2O3 not only lowered the sintering temperature of ferrite, but also adjusted the magnetic and dielectric properties, and the material has potential to apply for miniaturizing efficient antennas at high frequency.

Application of Peroxide Curing Systems in Cross-Linking of Rubber Magnets Based on NBR and Barium Ferrite

Rubber magnetic composites were prepared by incorporation of barium ferrite in constant amount—50 phr into acrylonitrile-butadiene rubber. Dicumyl peroxide as the curing agent was used for cross-linking of rubber magnets alone, or in combination with four different types of co-agents. The main aim was to examine the influence of curing system composition on magnetic and physical-mechanical properties of composites. The cross-link density and the structure of the formed cross-links were investigated too. The results demonstrated that the type and amount of the co-agent had significant influence on cross-link density, which was reflected in typical change of physical-mechanical properties. The tensile strength increased with increasing amount of co-agents, which can be attributed to the improvement of adhesion and compatibility on the interphase filler-rubber due to the presence of co-agents. Magnetic characteristics were found not to be influenced by the curing system composition. The application of peroxide curing systems consisting of organic peroxide and co-agents leads to the preparation of rubber magnets with not only good magnetic properties but also with improved physical-mechanical properties, which could broaden the sphere of their application uses.

Comparative analysis of efficient Pb dopant in R and R–S blocks of BaFe12O19 structure synthesized by co-precipitation method

Site occupancy plays an important role in the properties of the materials in general, and in the case of ferrites, this makes a significant effect. Barium ferrite has a wide range of applications ranging from everyday applications to sophisticated communication technologies. Two compositions Ba1−xPbxFe12O19 and BaPbxFe12−xO19 (x = 0.0–1.0) were synthesized by co-precipitation method using similar synthesis conditions. The aim was to understand the different behaviors when Pb replaced Ba in R and R* blocks in the first composition, while in the second composition it replaced iron in RSR*S* blocks. Microstructural and morphological variations in both synthesized compositions because of Pb dopant were responsible for affecting all properties. Higher ionic radius (1.76 A), lower melting point (950 °C) of lead and gradually increased concentration were responsible for generating stresses and distortions of different magnitudes in both compositions. Magnetic and DC electrical characterizations were investigated by applying similar conditions. Higher phase purity and better morphology are obtained when Ba is replaced by Pb. Strong variation in coercivity due to decrease in anisotropic energy is useful in high-density storage devices. For the other composition, when Fe is replaced by Pb, higher resistivity is obtained. The obtained range of resistivity is useful against eddy current losses in high-frequency devices.

Achieving impressive millimeter-wave absorption properties in Nb5+ doped barium ferrite by simply controlling the sintering atmosphere

To enhance the millimeter-wave absorption properties around atmospheric window of 35 GHz, Nb5+ doped barium ferrite precursors are sintered at 1400 °C for 3 h in air, Ar, N2 respectively. The magnetic loss region covers 30 ∼ 40 GHz in the sample sintered in air and extends to 26.5 ∼ 40 GHz in the sample sintered in N2. The ε′ and ε″ vary from ∼5 to ∼0.4 by sintering in air to ∼10 and ∼0.3 by sintering in Ar, and to ∼13 and ∼2.0 in N2. Ultimately, contributed by enhanced permittivity and extended magnetic-loss region, the sample sintered in N2 exhibits impressive millimeter-wave absorption properties around 35 GHz with broad bandwidth more than 12 GHz and maximum reflectivity of −37 dB under thin thickness of 0.55 mm.

Barium ferrite nanoparticles: a highly effective EMI shielding material

Electromagnetic interference (EMI) is one of the main causes for the failure of electronic devices working in close vicinity of EM field induced by the neighboring electronic device. Therefore, we report a facile synthesis of barium ferrite (BaFe12O19) nanoparticles via sol-gel technique for efficient EMI shielding application. These nanoparticles were annealed at 400 °C, 700 °C, and 850 °C to investigate the effect of temperature on shielding efficiency and morphology of BaFe12O19 nanoparticles. The structure, morphology, phase purity, magnetism, and shielding effectiveness were analyzed using Fourier-transform infrared (FT-IR) spectroscopy, x-ray diffraction (XRD), electron microscopy (SEM and TEM), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. These studies suggest that BaFe12O19 nanoparticles annealed at 850 °C exhibit crystalline pure phase hexagonal structure with the high magnetic moment (31.32 emu g−1) and coercivity (2.7 kOe). The total shielding effectiveness of the same was found to be −17.57 dB at 11.58 GHz, which is much higher than those of earlier reported studies.

Structure and Electromagnetic Properties of Z-Type Barium Ferrite Composite Exposed to External Magnetic Field

The paper presents the analysis of the structure and electromagnetic properties of magnetodielectric composite material polymerized under the influence of the external magnetic field. The structure, phase composition and magnetic properties are determined for Z-type barium ferrite employed as a filling material in the production of test specimens. It is shown that the external magnetic field has an effect on the structure of this composite material. The proposed treatment technique allows fabricating test specimens with both magnetic and dielectric anisotropy parameters.

Refinement of the Atomic and Magnetic Structures of Solid Solutions BaFe12 – xInxO19 (x = 0.1–1.2) by the Neutron Diffraction Method

Structural investigations of solid solutions of BaFe12 – xInxO19 barium ferrites partially substituted with indium ions (x = 0.1–1.2) are carried out via the neutron diffraction method. Experimental investigations of ceramic samples are performed at room temperature using a high-resolution neutron diffractometer that allows precise information about changes in the crystal and magnetic structures, as well as microstructural parameters, to be obtained. Refinement of the crystal structure of the composition BaFe12 – xInxO19 is carried out in the framework of two space groups P63/mmc and Р63mc. Solid solutions of barium ferrites retain the hexagonal crystal-structure type in the entire investigated concentration range. Their ferrimagnetic structure is well described by Gorter’s model where magnetic moments are ordered along the c axis. Spontaneous polarization is revealed in barium hexaferrites partially substituted with indium ions. The total magnetic moment per formula unit decreases as the amount of diamagnetic In ions is increased. An increase in microstrains in the crystallites with increasing amount of In ions is explained by increasing disorder of the system because of the statistical distribution of diamagnetic ions in magnetic sublattices.

Smart strain sensing organic–inorganic hybrid hydrogels with nano barium ferrite as the cross-linker

Polyacrylic acid hybrid hydrogel with nano barium ferrite as a cross-linker exhibits stable piezoresistive sensing performance with negligible hysteresis loops.

Magnetic and Dielectric Properties of Low Temperature co-fired Na-Ta co-doped M-type Barium Ferrites

Na-Ta ions co-doped M-type barium ferrites, BaFe12-2x(NaTa)xO19, were synthesized at low temperature by the solid-state method. Na-Ta ion could occupy crystalline sites but not change the phase formation of barium ferrite. SEM images showed that samples had the regular and hexangular shape with 1-2 μm size. With the increase of Na-Ta, saturation magnetization (Ms) obviously decreased from 57.5 emu/g to 37.6 emu/g, and the coercivity (Hc) decreased from 4156 Oe to 2069 Oe. For dielectric properties, the real part permittivity (ε

Correlation of crystalline and magnetic structures of barium ferrites with dual ferroic properties

Abstract The spontaneous polarization has been found out in solid solutions of barium ferrites partially substituted with In, Al, Ga and Sc ions that is an evidence of their ferroelectric properties. For explanation reasons of appearance ferroelectric properties in these materials have been investigated features of crystal and magnetic structures with using X-ray and neutron time-of-flight diffraction methods in a wide temperature range. The crystal structure of barium ferrites has been refined in the frameworks of centrosymmetric P 6 3 / mmc (No. 194) and non- centrosymmetric P 6 3 mc (No. 186) space groups. According to analysis of neutron patterns, the distortion of oxygen octahedrons (tetrahedrons and trigonal-bipyramids) has been observed in unit cells both space groups. It was shown that a key role in appearance of spontaneous polarization can be associated with the absence of inversion center in unit cell.

Visible Light Induced Photodegradation of Methylene Blue in Sodium Doped Bismuth Barium Ferrite Nanoparticle Synthesized by Sol-gel Method

Perovskite-like BiFeO3 nanoparticles doped with barium and sodium ions were synthesized via the citric acid route by the sol-gel method. The as-prepared Bi0.65Na0.2Ba0.15FeO3 nanopowders were divided into three equal portions and separately annealed at various annealing temperatures of 600, 700 and 800°C. The powders were characterized using X-ray diffraction (XRD) and crystallized with a rhombohedral R3c space group. Scanning electron microscopy was used to determine the morphology of the crystal and Fourier transform infrared spectroscopy was conducted at room temperature to determine the phase purity and the B-site formation in the perovskite structure. The UV-vis diffuse reflectance spectroscopy of all the materials was investigated, showing strong photoabsorption (λ &gt; 420 nm). The doping effect of BiFeO3 enhanced photocatalytic activity while it significantly reduced the energy bandgap to 2.05 eV (for BNBFO at 800°C) which showed strong visible light absorption. The photocatalytic activity of Bi0.65Na0.2Ba0.15FeO3 nanomaterials was tested by monitoring the degradation rate of methylene blue dye pollutant under visible light irradiation in aqueous solution. All powders showed photoactivity after 2 hours of visible light irradiation. The annealing temperature greatly affected the methylene blue degradation, showing the efficiencies of 57, 67 and 75 % for BNBFO at 600, 700 and 800°C, respectively. Kinetic studies were carried out and the rate constants of 6.70 x 10-3, 8.90 x 10-3 and 1.05 x 10-2 min-1 were obtained for powders annealed at 600, 700 and 800°C, respectively. The photocatalytic mechanism of the degradation process was proposed in this study.

Highly efficient low cost EMI shielding by barium ferrite encapsulated polythiophene nanocomposite

Barium ferrite encapsulated polythiophene (BaFe12O19/PTh) nanocomposite has been synthesized to analyse electromagnetic interference (EMI) shielding. The morphological analysis of the synthesized composites has been investigated by scanning electron microscopy (SEM), which confirmed the encapsulation of BaFe12O19 nanoparticles by PTh forming a core-shell structure. Highest loading of BaFe12O19 in composite (NC-100 i.e. BaFe12O19:PTh = 1:1) exhibits excellent magnetic properties with a magnetic moment and coercivity of 25.78 emu/gm and 2.5 kOe, respectively. Microwave shielding behaviour of the nanocomposite samples has been tested in X-band region by vector network analyser. Highest −43.27 dB shielding effectiveness at 11.65 GHz has been obtained in NC-100 composite. The excellent shielding effectiveness is due to the synergistic effect of dielectric and magnetic loss of the nanocomposite. These results suggest that the BaFe12O19/PTh nanocomposite (NC-100) exhibited superior EMI shielding properties and find wider application as low cost, high performance, lightweight microwave absorbing material.