BaFe12O19 Research Articles

Structural, Morphological, and γ-ray Attenuation properties of m-type hexaferrite BaFe12O19 doped with V2O5, Ce2O3 and Bi2O3 for Radiation Shielding applications

This paper studies, structurally analyzes, evaluates the morphology, and assesses the gamma-ray and neutron attenuation properties of a composite material composed of M-type hexaferrite BaFe12O19 (BF) doped with three additional compounds: Bi2O3, V2O5, and Ce2O3. X-ray diffraction revealed that the structure of BF can be indexed to a hexagonal structure, BF/Bi2O3 to a tetragonal structure, BF/V2O5 to a cubic structure, and BF/Ce2O3 to a trigonal structure. These results were refined using PROFEX software. The Crystallite size of the nano-powders was determined by X-ray line broadening using the Williamson-Hall method. Morphology evaluations illustrated that HR-TEM images for BF, BF/Bi2O3, BF/V2O5, and BF/Ce2O3 reveal high crystallinity with a polycrystalline nature. Various attenuation measurements, using the FLUKA Monte Carlo code, aimed to determine the efficacy of these dopants into m-type hexaferrite BF as potential materials for radiation shielding applications. Doping with Bi2O3 into hexaferrite BF markedly enhances its attenuation properties, demonstrating superior Linear Attenuation Coefficient (LAC) values across a broad energy spectrum from 0.16 to 10 MeV. The Mass Attenuation Coefficient (MAC) analysis revealed a pivotal energy threshold at 0.3 MeV. Below this energy, BF presented the highest MAC values. Conversely, for energies equal to or greater than 0.3 MeV, BF exhibited the highest MAC values, affirming its superior gamma photon shielding efficacy. The study of the Half Value Layer (Δ0.5) and Mean Free Path (MFP) provided additional evidence of the superior shielding performance of BF/Bi2O3. The Δ0.5 values ranged between 0.128 to 1.240 cm for BF, 0.162 to 1.430 cm for BF/V2O5, 0.163 to 1.390 cm for BF/Ce2O3, and 0.162 to 1.210 cm for BF/Bi2O3, indicating that BF/Bi2O3 requires a thinner layer to halve the gamma-ray intensity, particularly at higher energies. The MFP values further support the improved shielding ability of BF/Bi2O3, with measurements showing that gamma photons travel the shortest distance before interacting with the material, thereby reducing the potential for radiation exposure.

Charge Storage Properties of Ferrimagnetic BaFe12O19 and Polypyrrole-BaFe12O19 Composites.

This investigation is motivated by an interest in multiferroic BaFe12O19 (BFO), which combines advanced ferrimagnetic and ferroelectric properties at room temperature and exhibits interesting magnetoelectric phenomena. The ferroelectric charge storage properties of BFO are limited due to high coercivity, low dielectric constant, and high dielectric losses. We report the pseudocapacitive behavior of BFO, which allows superior charge storage compared to the ferroelectric charge storage mechanism. The BFO electrodes show a remarkably high capacitance of 1.34 F cm-2 in a neutral Na2SO4 electrolyte. The charging mechanism is discussed. The capacitive behavior is linked to the beneficial effect of high-energy ball milling (HEBM) and the use of an efficient dispersant, which facilitates charge transfer. Another approach is based on the use of conductive polypyrrole (PPy) for the fabrication of PPy-BFO composites. The choice of new polyaromatic dopants with a high charge-to-mass ratio plays a crucial role in achieving a high capacitance of 4.66 F cm-2 for pure PPy electrodes. The composite PPy-BFO (50/50) electrodes show a capacitance of 3.39 F cm-2, low impedance, reduced charge transfer resistance, enhanced capacitance retention at fast charging rates, and good cyclic stability due to the beneficial effect of advanced dopants, HEBM, and synergy of the contribution of PPy and BFO.

Synthesis, structural and magnetic study of BaFe12O19/CoFe2O4@CoFe2 nanocomposites

Cooperative effects in hybrid nanocomposites are an interesting field of research. The behavior of magnetic nanocomposites is the result of spatial arrangements of phases and their magnetic correlations through exchange and dipolar forces. Understanding these influences is an important task in order to produce magnetic composites with improved properties. In this work, we present a study on the structural and magnetic properties of nanocomposites made of barium hexaferrite (BaFe12O19) coated either with cobalt ferrite spinel (CoFe2O4) or core-shell CoFe2O4@CoFe2 nanoparticles, i.e. BaFe12O19/CoFe2O4 or BaFe12O19/CoFe2O4@CoFe2. The BaFe12O19 (BFO) phase was produced using the ionic coordination reaction technique and then coated with CoFe2O4 (CFO) nanoparticles synthesized by the polyol method. Several concentrations of the BFO and CFO phases were considered. The BFO/CFO samples were reduced in hydrogen gas, where partial reductions of cobalt ferrite give rise to the alloy CoFe2 (CF). Thus, we produced a new nanocomposite of the type BFO/CFO@CF. These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Mössbauer spectroscopy (ME). The XRD and ME analyzes revealed the presence of the phases BFO and CFO, for the non-reduced nanocomposites, and for the partially reduced nanocomposites we found three phases BFO, CFO and CF. TEM images showed that these phases are structurally coupled. Isothermal remanent magnetization (IRM) and direct current remanent demagnetization (DCD) measurements were done and the analyzes through the Henkel and δm plots were performed, providing information about the nature of the interactions among the phases and their magnetic behavior. The samples BFO/CFO and BFO/CFO@CF with the lowest percentage of BFO (∼7 wt%) showed exchange coupling between the phases while the other samples exhibited predominantly magnetic dipolar interactions.

Investigation of the magnetic and mechanical performance of fly ash Geopolymer/BaFe12O19 nanocomposites

The magnetic and mechanical properties of a geopolymer (GeO) were improved by using composites with BaFe12O19 (BFO) nanoparticles. The composites were prepared with 0, 1, 3, and 5 wt% of BFO nanoparticles. All samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM) and compressive strength measurements. The contribution of O 1s in all samples was observed using X-Ray photoemission spectroscopy (XPS). All composite samples exhibited ferromagnetic behavior at room temperature with large hysteresis loops and increased magnetization with higher BFO nanoparticle contents. The compressive strength values of the composites increased from 58.2 to 62.2 MPa as the BFO nanoparticle content was raised from 0 to 3 wt%. An increased strength of the GeO suggests a higher denser and more compaction due to addition of BFO nanoparticles in the voids of a N-A-S-H gel structure. The LAC values for the geopolymer composites increased with BFO powder levels.

A comprehensive study of structure, oxygen vacancy, and electrical properties of Mg2+ introduced in barium hexaferrite synthesized via spark plasma sintering

Barium hexaferrite BaFe12O19 (BFO) was prepared following conventional solid-state reaction procedure (CSRP) and its’ reformed compound has been prepared following CSRP and spark plasma sintering (SPS) approaches. The Rietveld refinement of synchrotron x-ray diffraction (SXRD) study assured single-phase formation of hexaferrite (M-type with space-group P63/mmc). A dense microstructure appeared in the SPS prepared sample compared to the other compounds. The presence of multiple valances of Fe (Fe2+ along with Fe3+) was studied following modified Mohr’s salt titration (MST) besides of oxygen vacancy estimation. Mg-doped increased oxygen vacancy amount via enhancing Fe2+ in the sample. As a result, the impedance was lower in the Mg-doped BFO (BFMO) samples in contrast to undoped sample, where SPS BFMO further reduced impedance.

Preparation, Antibacterial Activity, and Catalytic Application of Magnetic Graphene Oxide-Fucoidan in the Synthesis of 1,4-Dihydropyridines and Polyhydroquinolines.

Polymer‐coated magnetic nanoparticles are emerging as a useful tool for a variety of applications, including catalysis. In the present study, fucoidan‐coated magnetic graphene oxide was synthesized using a natural sulfated polysaccharide. The prepared BaFe12O19@GO@Fu (Fu=fucoidan, GO=graphene oxide) was characterized using Fourier‐transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray (EDX) analysis, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), Raman spectroscopy, and X‐ray diffraction (XRD). The catalytic proficiency of BaFe12O19@GO@Fu was investigated in the synthesis of 1,4‐dihydropyridine and polyhydroquinoline derivatives. Excellent turnover numbers (TON) and turnover frequencies (TOF) (6330 and 25320 h−1) testify to the high efficiency of the catalyst. Moreover, the antimicrobial activity of BaFe12O19@GO@Fu was evaluated against Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) through the Agar well diffusion method, indicating that BaFe12O19@GO@Fu has antibacterial activity against S. aureus.

The detailed studies of the structural and magnetic properties of hexaferrites Ba1−xSrxFe12O19 for 0.0 ≤ x ≤ 0.75

The monophase polycrystalline hexaferrites Ba1−xSrxFe12O19 for 0 ≤ x ≤ 0.75 were prepared using the sol–gel synthesis method. The average crystallite size (Dac) ranged from 47 to 50 nm with Sr doping. The crystal structure and magnetic properties have been studied using X-ray diffraction (XRD) and neutron diffraction (ND). The structure of the studied hexaferrites is described by the hexagonal symmetry of P63/mmc space group. Field-emission scanning electron microscopy (FE-SEM) revealed the heterogeneous distribution of the grain sizes, which takes the hexagonal shape. Energy-dispersive X-ray spectroscopy (EDS) showed that the element compositions agree with the used components for each prepared sample. The substitution of Ba2+ ions by Sr2+ enhances the thermal stability of these hexaferrites. The magnetic hysteresis loops for the studied hexaferrite samples were obtained at room temperature. Different magnetic parameters are given in this work. The magnetocrystalline anisotropy parameter (Keff) initially increases for x ≤ 0.5 and then decreases for (x = 0.75). According to the analysis of neutron data, the magnetic structure formed by the Fe3+ ions, is located in five non-equivalent crystallographic sites with tetrahedral (Fe3-4f1), octahedral (Fe1-2a, Fe4-4f2, and Fe5-12k), and trigonal bipyramidal (Fe2-2b) coordinations. The strontium doping BaFe12O19 (BFO) hexaferrite affects the crystal lattice parameters, bond lengths, bond angles, and ordered magnetic moments of iron. Finally, the enhancement of the thermal stability and some magnetic parameters of the studied hexaferrite samples could be important for applications.

Evidence for Conical Magnetic Structure in M‐Type BaFe12O19 Hexaferrite: A Combined Single‐Crystal X‐ray Magnetic Circular Dichroism and Neutron Diffraction Study

The magnetic ground state of BaFe12O19 (BFO) is investigated using X‐ray absorption spectra (XAS), X‐ray magnetic circular dichroism (XMCD), and neutron diffraction studies at 1.2 and 1.5 K, respectively. The XMCD measurements on single‐crystals of BFO in grazing‐incidence geometry reveal canting of the spins away from the c‐axis of the hexagonal unit cell. Single‐crystal neutron diffraction studies reveal magnetic satellite peaks along the 00l reciprocal lattice row around the forbidden l = 2n ± 1 positions confirming the conical‐type magnetic structure in the ground state of BFO. The observation of the conical magnetic structure of BFO opens the possibility of type‐II multiferroicity in undoped BFO.

Impact of Gd doping on the dielectric and magnetic properties of (Sr–Ba) Fe12O19 nanoparticles

Composition Ba0.5Sr0.5Fe12-xGdxO19, where x = 0 to 0.4 in steps of 0.1 was synthesized by Without Water and Without Surfactant (WOWS) Sol-Gel method. The synthesized powder was calcined and sintered at 910 °C/20 min and 920 °C/20 min, respectively. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques to study phase purity, surface morphology and particles shape of the samples, respectively. There is no change in the lattice constant value of ‘a’ but value of ‘c’ showed small change in undoped and Gd-doped mixed 0.5Sr-0.5Ba hexaferrite samples. SEM micrographs revealed that particles shape is spherical and grains size reduced up to x = 0.4 Gd doping. Grain size was from 180 to 130 nm. Dielectric properties were measured from 20 Hz–3 MHz at room temperature. The dielectric constant,ε, values were high in frequency range from 20 to 600 Hz and dielectric loss tangent, tanδ showed low values from 20 Hz to 3 kHz. However, in high frequency regions both values were not sensitive to the frequency changes. It is also observed that ε, values of all Gd doped samples are high (except 0.2 Gd doped) and tan δ values of all Gd doped samples are low as compared to the undoped sample. The AC conductivity, σac values remained almost constant in the low frequency region up to 6 kHz and showed exponential increase in the frequency region >6 kHz. AC Electrical conductivity of all Gd doped samples is high as compared to undoped sample. These changes are explained by Maxwell-Wagner model. Cole-Cole plots showed that changes in the electrical properties of the undoped and Gd doped mixed 0.5Sr-0.5Ba hexaferrite sample is due to the change in grains size and grain boundaries resistance. The vibrating sample magnetometer, VSM was used to study magnetic properties. Values of coercivity, Hc decreased for x = 0.1 Gd doped sample as compared to undoped sample. Further increase in Gd doping concentrations leads to increase in Hc values and highest value of 6202 Oe is observed which is close to the theoretically predicted value. However, saturation magnetization, Ms and remanence, Mr values increased for doped samples up to x = 0.2 Gd and then further doping decreased these values. The 0.1 Gd doped 0.5Ba-0.5Sr ferrite material may be used in the recording media devices.

Research progress of high temperature microwave-absorbing ceramic matrix composites

Microwave-absorbing ceramic matrix composites play an important role in the development of heat-resisting stealthy materials due to their excellent high-temperature mechanical property, superior corrosion resistance and oxidation resistance. In this paper, the micro to macromultiscale design principle of microwave-absorbing ceramics is introduced. The latest research progresses of microwave-absorbing materials such as modified SiC ceramics, doped BaFe12O19 (BFO) ceramics, polymer derived ceramics (PDCs), 3D printed porous ceramics/ceramic-honeycombs, multiscale-designed continuous fiber reinforced ceramic matrix composites (CFCMC) and other new ceramic matrix composites are overviewed. The development trend of ceramic matrix composites with integrated structure absorbing is prospected, and the fiber reinforced ceramic matrix composites with multiscale structure design of micro-macro is proposed to be an important development direction in the field of high-temperature stealth materials in the future.

Complex Permittivity, Permeability and Microwave Absorption Studies of Double Layer Magnetic Absorbers Based on BaFe<sub>12</sub>O<sub>19</sub> and BaFe<sub>10</sub>CoZnO<sub>19</sub>

Microwave absorption properties of double layer magnetic absorbers based on BaFe12O19 (BFO) and BaFe10CoZnO19 (BFCZO) have been investigated in X-band (8.2–12.4 GHz) frequencies. The BFO and BFCZO were prepared by using a solid state reaction process. The crystalline structures were investigated by X-ray diffraction (XRD), The complex permittivity and permeability are determined using Vector Network Analyzer (VNA) in a range from 8.2 GHz to 12.4 GHz. The double layer magnetic absorbers, composed of the BFO as matching layer and the BFCZO as absorption layer, with a total thickness of 5 mm, showed an effective reflection loss (RL) an effective absorbing bandwidth below –5 dB.

Magnetic and microwave absorption properties in 2.6–18 GHz of A-site or B-site substituted BaFe12O19 ceramics

The A-site substituted (20 mol% Sr2+ and Ca2+) and B-site substituted (20 mol% Co3+ and Mn3+) M-type BaFe12O19 (BFO) ceramics were synthesized and the magnetic properties and microwave absorption were investigated. The A-site substitution by Ca2+ or B-site substitution by Co3+ can effectively modify the magnetic properties of the M-type BFO. The B-site dopant suppresses the complex permittivity more greatly than A-site ones and substitution of Co3+ at B-site changes the microwave permeability response to a resonate-like manner in 2.6–18 GHz. The A-site substitution is more effective on the enhancement of peak absorption whilst B-site substitution is more effective on the enhancement of absorption bandwidth. A wide bandwidth of reflection loss (RL) value below − 5 dB (> 70% microwave absorption) of the BaFe11.8Mn0.2O19 ceramic is obtained in 3.6–18 GHz and the minimum RL of − 18.5 dB is obtained at 7.2 GHz with a thickness of 2.5 mm.

Co substituted BaFe12O19 ceramics with enhanced magnetic resonance behavior and microwave absorption properties in 2.6 – 18 GHz

Abstract BaFe12-xCoxO19 (BFCO, x ≤ 0.4) ceramics with superior magnetic and electromagnetic (EM) properties were prepared using Co3+ substituted BaFe12O19 (BFO) in 2.6–18 GHz. Compared with the ceramics without Co3+, the incorporation of 40 mol% Co3+ enhances magnetic properties; the saturation magnetization (MS) is improved by about 55.6 emu·g−1 due to the variety of magnetocrystalline anisotropy. The resonance behaviors of complex permeability are observed and resonance frequency shifts to lower frequency range from 6 to 3 GHz. The minimum reflection loss (RL) of −32.1 dB (

RGO/BaFe12O19/Fe3O4 nanocomposite as microwave absorbent with lamellar structures and improved polarization interfaces

In this paper, we designed and prepared a composite of BaFe12O19 (BFO) flakes, two-dimensional graphene and Fe3O4 nanoparticles using a two-step solvothermal method. The combination of BFO flakes and two-dimensional graphene could effectively enhance the heterointerface and is believed to be favorable to enhance the interface polarization. The introduction of inverse spinel Fe3O4 as the third phase could increase the saturated magnetization. The phase structure, morphology, magnetic properties and electromagnetic wave absorption performance of the as-prepared samples were characterized. Due to the enhanced interfacial polarization between the BaFe12O19 flakes and graphene, the composite of RGO/BaFe12O19/Fe3O4 exhibits excellent microwave absorption properties. The maximum reflection loss can reach -46.04 dB at 15.6 GHz with a thickness of 1.8 mm, and the effective absorption bandwidth reaches 5.68 GHz (from 11.60 GHz to 17.28 GHz). It is believed that the RGO/BaFe12O19/Fe3O4 composites can find potential application in the field of microwave absorption due to their excellent absorption properties.

Quantum phase transitions in Ba(1−x)CaxFe12O19 ( 0≤x≤0.10 )

The ground state of BaFe12O19 (BFO) is controversial as three different quantum states, namely quantum paraelectric, frustrated antiferroelectric and quantum electric dipole liquid (QEDL), have been proposed. We have investigated the quantum critical behavior of BFO as a function of chemical pressure (a non-thermal variable) generated by smaller isovalent ion Ca2+ at the Ba2+ site. Analysis of synchrotron x-ray diffraction data confirms that Ca2+ substitution generates positive chemical pressure. Our dielectric measurements reveal that Ca2+ substitution drives BFO away from its quantum critical point (QCP) and stabilizes a quantum electric dipolar glass state whose dielectric peak temperature (Tc) increases with increasing Ca2+ content as Tc ~ (x-xc)1/2, a canonical signature of quantum phase transitions. Our dielectric measurements reveal that pure BFO is slightly away from its QCP with a Tc of 2.91 K. Specific heat measurements reveal excess specific heat of non-Debye and non-magnetic origin with linear temperature dependence below Tc which could be due to QEDL state of BFO.

Synthesis of sandwich microstructured expanded graphite/barium ferrite connected with carbon nanotube composite and its electromagnetic wave absorbing properties

Abstract The pursuing aim of high reflection loss and broad frequency bandwidth for electromagnetic wave (EMW) absorbing materials is a long-term task and under a close scrutiny. To construct rational microstructures for the absorber have significant impacts on increasing reflection loss and broadening frequency bandwidth. Herein, we presented a sandwich microstructured expand graphite (EG)/BaFe12O19 (BF) nanocomposite successfully prepared by in-situ sol-gel auto-combustion method. The experimental results showed that EG/BF nanocomposite has better EMW absorbing performance than pure EG and BF, the sandwich microstructured EG/BF connected with carbon nanotubes (CNTs) could further improve the electromagnetic performance effectively. The obtained CNT/EG/BF nanocomposite exhibited a saturation magnetization of 26.5 emu g−1 at room temperature and an excellent EMW absorbing performance. The maximum reflection loss of the sandwich microstructured CNT/EG/BF composites with a thickness of 1 mm was up to −45.8 dB and the frequency bandwidth below −10 dB could reach to 4.2 GHz within the frequency range of 2–18 GHz. The research results indicated that the prepared nanocomposite showed great potential as a new type of microwave absorbing material.

Synthesis and electromagnetic wave absorption property of amorphous carbon nanotube networks on a 3D graphene aerogel/BaFe12O19 nanocomposite

Abstract Homogeneous amorphous carbon nanotube (ACNT) networks have been synthesized using floating catalyst chemical vapor deposition method on a 3D graphene aerogel (GA)/ BaFe12O19 (BF) nanocomposite which was prepared by a self-propagating combustion process. The as-synthesized ACNT/GA/BF nanocomposite with 3D network structures could be directly used as a good absorber material for electromagnetic wave absorption. The experimental results indicated that the minimum reflection loss of ACNT/GA/BF composite with a thickness of 2 mm was −18.35 dB at 10.64 GHz in the frequency range of 2–18 GHz. The frequency bandwidth of the reflection loss below −10 dB was 3.32 GHz and below −5 dB was 6.24 GHz, respectively. The 3D graphene aerogel structures which composed of dense interlined tubes and amorphous structure bearing quantities of dihedral angles could consume the incident waves through multiple reflection and scattering inside the 3D web structures. The interlinked ACNTs have both the virtues of amorphous CNTs (multiple reflection inside the wall) and crystalline CNTs (high conductivity), consuming the electromagnetic wave as resistance heat. ACNT/GA/BF composite has a good electromagnetic wave absorption performance.

Direct in situ synthesis of a 3D interlinked amorphous carbon nanotube/graphene/BaFe12O19 composite and its electromagnetic wave absorbing properties

The 3D interlinked amorphous carbon nanotube (ACNT)/reduced graphene oxide (RGO)/BaFe12O19 (BF) composite was directly prepared by a self-propagation combustion process.

Effects of the Sintering Temperature on Structural and Bioactivity in BaFe<sub>12</sub>O<sub>19</sub>-P<sub>2</sub>O<sub>5</sub>-CaO-Na<sub>2</sub>O Bioactive Glass Ceramic

In this research, the effects of sintering temperatures on structural and bioactivity in BaFe12O19 (BF) /P2O5-CaO-Na2O bioactive glass ceramics were investigated. The BF/P2O5-CaO-Na2O bioactive glass ceramics were fabricated under various sintering temperatures in a range of 550-700 oC. X-ray diffraction (XRD) technique and the scanning electron microscopy (SEM) are used to characterize phase and microstructure. The studied samples were evaluated for mechanical properties by hardness testing. Moreover, the bioactivities of studied samples were studied by using simulated body fluid (SBF) in vitro. It was found that, the sintering temperatures are the most influential parameter on microstructure and mechanical properties of the bioactive glass ceramics. The highest density of studied ceramics was found in the sample sintered at 700 oC. The microstructural properties of the studies samples were investigated and the results were then correlated with the characteristics of sintering temperature as well as the microstructure of the bioactive glass ceramic. Moreover, the covering of bone-like apatite layer on the surface sample after a 7 day immersion in SBF suggested that the BF/P2O5-CaO-Na2O glass ceramics have acceptable bioactivities.

Suppressing of slow magnetic relaxation in tetracoordinate Co(II) field-induced single-molecule magnet in hybrid material with ferromagnetic barium ferrite.

The novel field-induced single-molecule magnet based on a tetracoordinate mononuclear heteroleptic Co(II) complex involving two heterocyclic benzimidazole (bzi) and two thiocyanido ligands, [Co(bzi)2(NSC)2], (CoL4), was prepared and thoroughly characterized. The analysis of AC susceptibility data resulted in the spin reversal energy barrier U = 14.7 cm−1, which is in good agreement with theoretical prediction, Utheor. = 20.2 cm−1, based on axial zero-field splitting parameter D = −10.1 cm−1 fitted from DC magnetic data. Furthermore, mutual interactions between CoL4 and ferromagnetic barium ferrite BaFe12O19 (BaFeO) in hybrid materials resulted in suppressing of slow relaxation of magnetization in CoL4 for 1:2, 1:1 and 2:1 mass ratios of CoL4 and BaFeO despite the lack of strong magnetic interactions between two magnetic phases.