Synthesis Of Barium Hexaferrite Research Articles

Characterization of Barium Hexaferrite (BaFe<sub>12</sub>O<sub>19</sub>) from NitrateCompound with Sol-Gel Method for Barium Hexaferrite MagneticMaterials

Barium Hexaferrite is a permanent magnet material known for its excellent quality and relatively inexpensive manufacture. Barium hexaferrite has good stability and can be applied in various technologies. In this research, the synthesis of barium hexaferrite has been successfully made from the primary materials Fe (NO3)3 and Ba (NO3)2 using the sol-gel method, as well as other materials such as NaOH, chitosan, molasses, acetic acid and distilled water as the primary solvents for several materials. In addition, variations in aging time 0 hours, 2 hours, 4 hours and 6 hours were added to see the effect on morphology, crystal structure and the magnetic properties of barium hexaferrite magnets. The characterization process is carried out with three testing processes, namely X-Ray Diffraction testing (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM). From the XRD, it was found that the desired phase of Barium Hexaferrite (BaFe12O19) was formed, while in the SEM testing process, it was seen that the aging time of the barium hexaferrite sample decreased the particle size of the barium hexaferrite BaFe12O19 from an aging time of 0 hours seen 681.459 nm and at an aging time of 6 hours. Visible 538.859 nm particle size formed. The VSM characterization results showed that different aging times did not affect the barium hexaferrite nanomagnets' magnetic properties.

Influence of sintering temperature on structural, morphological and magnetic properties of barium hexaferrite nanoparticles

Barium hexaferrite nanoparticles are attractive for modern data storage and microwave devices due to their unique properties. Single phase synthesis of barium hexaferrite using sol–gel auto-combustion route was optimized by varying sintering temperature and time. X-ray diffraction confirmed single phase hexagonal crystal structure of the sample sintered at 1100[Formula: see text]C for 2 h. Crystallite size, as determined using Scherrer’s formula, was increased with the increase in sintering temperature while the porosity remained nearly unchanged. Field emission scanning electron microscope (FE-SEM) revealed that grain size was increased from nanometers to micrometers by rising the sintering temperature and the shape of particles was platelet-like hexagonal at 900[Formula: see text]C. Vibrating sample magnetometer (VSM) exhibited that saturation magnetization and coercivity increased with the increase of sintering temperature. Maximum saturation magnetization and coercivity values were 36.80 emu/g and 5365 Oe, respectively, for the sample sintered at 1100[Formula: see text]C for 2 h.

Synthesis of Barium Hexaferrite with Addition of Tapioca as Rodlike Template

Barium hexaferrite is categorized as hexagonal ferrite material with ferrimagnet properties. Barium hexaferrite has high coercivity, curie temperature, anisotropy magnetic field, and chemical stability that is often used as permanent magnet. It can be synthesized by using bottom up or top down method. The bottom up method of sol-gel has potential advantages in industry application compared to the top down method because of low energy requirement, more homogeneous product, and low time consuming to achieve nanometer size. The development of sol-gel method by using tapioca and chitosan as surfactant increases the quality of the product. Tapioca is used to increase anisotropy properties of particles by changing the particles shape into rodlike shape whereas chitosan is used to stabilize them at small size. Molar ratio of Fe3+/Ba2+ is set on 12 and the ratio of tapioca/chitosan is set on 1/3, 1/2, and 1. Iron (III) nitrate is used as Fe3+ source whereas barium nitrate is used as Ba2+ source. Condensation is done by heating up the sol system in the oven at 100OC. The product then is calcined at 1000OC with holding time of 3 hours. The calcined product is then characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Vibrating Sample Magnetometer (VSM). XRD result shows that the hematite phase has still been formed. The occurrence of the phase indicates that the reaction between iron and barium is uncompleted. SEM images show the existence of needle and rod-shaped particles with diameter of 200nm–550nm. It explains that tapioca can be used as rodlike template. The increase of tapioca tends to enlarge the rod-shaped particle and remove the needle-shaped particle. VSM result shows that the highest value of Br is found in the sample of tapioca/chitosan with the ratio of 1/3 and the value of 24 emu/g. The fact indicates that the optimal ratio of tapioca/chitosan is 1/3.

Effect of heat treatment on the phase composition, structure and magnetic properties of M-type barium hexaferrite

Effect of the heat treatment of carbonate-hydroxide precipitates on the phase composition, structure and magnetic properties of M-type barium hexaferrite has been investigated using the Mőssbauer spectroscopy, X-ray phase analysis and magnetic measurements.The distribution of Fe3+ ions over structural sites of barium hexaferrite with different degree of ferritizations has been defined. The conditions of single-domain behavior of barium hexaferrite nanoparticles in the magnetic field have been discussed.Obtained results explain the formation of magnetic structure during the synthesis of barium hexaferrite. This information could further be used for optimizing conditions for synthesis of nanosized barium hexaferrite with high-level properties.

Fractal structure of precursors and phase transformations in the sol-gel synthesis of nanoparticulate M-type barium hexaferrite

We have studied the influence of sol-gel process conditions on the fractal structure of precursors, the phase transformations during the synthesis process, and the morphology of the resulting barium hexaferrite particles and determined the optimal fractal structure of sol-gel derived precursors for the solid-state synthesis of barium hexaferrite. The activity of the precursors is shown to correlate with the fractal dimension of their first structural aggregation level. Nanoparticulate barium hexaferrite can be prepared in the form of anisometric particles: platelets (dav ∼ 65 nm) and nanorods (dav ∼ 30 nm, lav ∼ 70 nm).

Effect of preparation conditions on fractal structure and phase transformations in the synthesis of nanoscale M-type barium hexaferrite

The conditions of the synthesis of carbonate-hydroxide precursors (pH of FeOOH precipitation and heat treatment regimes) were studied in terms of their effect on the fractal structure and physical–chemical properties of precursors. Phase transformations which occur during the synthesis of nanosize M-type barium hexaferrite (BHF) were studied as well. The first structural level of precursors' aggregation for mass fractals, the correlation between fractal dimension and precursors' activity during the synthesis of BHF were determined. Synthesis parameters for the precursors with the optimal fractal structure were determined. These data permit an enhancement of the filtration coefficient of the precipitates by a factor of 4–5, obtaining substantial decrease in the temperature required for synthesis of a single-phase BHF, and monodispersed plate-like nanoparticles (60 nm diameter) with the shape anisotropy and good magnetic characteristics (saturation magnetization ( M s )=68,7 emu/g and coercitivity ( H c )=5440 Oe).

Magnetic properties of cobalt substituted M-type barium hexaferrite prepared by co-precipitation

The co-precipitation and solid state methods were used in the synthesis of barium hexaferrite (BaM). Phase pure BaM was obtained with 1, 2, 3, 5, 10, 15, 20 and 30 wt% cobalt oxide (Co 3O 4). The addition of Co 2+/3+ ions to the BaM increased the permeability and magnetic loss tangent to a value of 3.5 at 5% and reduced to 1 at 30% doping. With increased Co doping, M s was reduced from 87-58 emu/g, M r increased from 11 to 40 emu/g with 3–5 wt% Co and 9 emu/g for 30% doping. H c sharply increased from 540 to 2200 Oe with a reduction to 280 Oe at 10 K with increasing temperature to 300 K. T c increased from 740 to 750 K for 30% Co doping. DTA–TGA studies of green body showed decarboxilation to occur at around 825 °C and the transformation of residual Co 3O 4 to Co 2O 3 at around 577 °C. The XRD data confirmed the Co ions substituting into Fe sites until a 10–15% doping level where the structure altered to W-type hexaferrite. The densities of the compounds varied with doping to a maximum of 4.45 g/cm 3.

New Methods for Development of Three-Dimensional Ceramics Based on Barium Hexaferrite with Chromium Additives

The possibility of implementing a reaction of self-propagated high-temperature synthesis of ferrites controlled through selective laser treatment is demonstrated. The conditions of synthesis of barium hexaferrite with a chromium additive and the effect of additional annealing on the results of synthesis are investigated. The three-dimensional ceramic products obtained have sufficiently good consumer properties.

Synthesis of barium hexaferrite by the co-precipitation method using acetate precursor

Fine particles of barium hexaferrite were synthesised by a chemical co-precipitation method using acetate-nitrate (barium acetate + iron nitrate) precursors. The thermal properties, phase composition and morphology of hexaferrite powders were studied. Simultaneous DTA/TG results confirmed by those obtained from XRD and VSM, indicated that the formation of barium hexaferrite occurs at a relatively low temperature of 710°C. This temperature is affected by the Fe3+/Ba2+ molar ratio. The SEM investigations revealed that the mean particle size of barium hexaferrite increases with increasing calcination temperature. In this system the Fe3+/Ba2+ molar ratio of 12 (stoichiometric ratio) is favourable.

Hydrothermal synthesis of barium hexaferrite

The authors of the report carried out synthesis of barium hexaferrite (BHF) both in water vapor atmosphere and in liquid medium in the temperature range 200-400°C at pressures PH2O of 9-26MPa in laboratory autoclaves. The results of research have shown that BHF with the best performances can be obtained by thermovaporous treatment of dry mixtures of precursors (γ-F2O3 with barium hydroxide or nitrate). As Fe - containing precursor, α-FeOOH can be also used. The formation of BHF begins at the temperature of about 200° C. The BHF crystals are hexagonal platelets with diameter ≥ 1 μm and thickness 0,1 −0,2 μm. The magnetic properties of synthesized BHF can be improved by increasing the temperature of thermovapor treatment. The coercive forces of the BHF samples synthesized at about 400°C vary from 1.7-2.0 kOe and spec& saturation magnetization of nonoriented samples from 40-50emu/g. BHF crystals with low coercive force (0.6-0.7) kOe were obtained by introduction of doping micro-additives at the stage of their formation in water vapor atmosphere.

Variations in the synthesis of barium hexaferrite doped with iridium and its effect in the catalytic combustion of hydrocarbons

This paper discusses the influence of the synthesis technique on the porous structure, phase transformation, and catalytic properties of barium hexaferrite. Barium hexaferrite was synthesized by two different citrate gel methods. The first one involved metal salts, citric acid, and ammonia, while the second dispersed the same components in a polyacrylamide gel. X-ray diffraction analysis was used to determine the nature of the phase while the Brunauer, Emmett, and Teller (BET) analysis was used to study the porous structure of the material which were heat-treated at 700 °C, 900 °C, and 1200 °C. The catalytic activity of all materials in the combustion of methane was also measured.

ChemInform Abstract: Synthesis of Barium Hexaferrite by the Oxidation of a Metallic Barium‐ Iron Precursor.

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Synthesis of Barium Hexaferrite by the Oxidation of a Metallic Barium–Iron Precursor

Tapes of the hard magnetic ferrite, BaFe12O19, were synthesized by the oxidation of metallic barium and iron precursors. Milled mixtures of barium flakes and iron powder (Ba:Fe atomic ratio = 1:12) were sealed within fugitive silver tubes and then compacted and formed into tapes by rolling at room temperature. Oxidation and postoxidation heat treatments were conducted over the temperature range 300°–1250°C (the silver was removed after heat treatment at 900°C). Phase‐pure BaFe12O19 tapes were produced after heat treatments at peak temperatures of is greater than or equal to $1080°C. Such tapes exhibited room‐temperature magnetization values of is greater than or equal to $65.0 emu/g in an applied field of 16.5 kOe (1.32 × 106 A/m). A coercivity of 3.44 kOe (2.75 × 105 A/m) was achieved in a fine‐grained (submicrometer) BaFe12O19 tape that had been annealed for 24 h at a peak temperature of 1080°C.

Synthesis of Barium Hexaferrite and Catalytic Behavior in the Combustion of Methane

Barium hexaferrite doped with iridium was synthesized by two methods: the citrate get and the polyacrylamide get methods. The nature of phases obtained and the specific surface area were determined after heat treatments in air at 700°C, 900°C and in air containing 10% humidity at 1200°C. The catalytic activity in the combustion of methane was measured after heat treatment at 900°C. These hexaferrites showed a good catalytic activity after treatment at 900°C. However this catalytic activity and the specific surface disappeared after heat treatment at 1200°C.

Synthesis of barium hexaferrite by pyrolysis of an aerosol

Polycrystalline BaFe12O19 has been synthesized by pyrolysis of an aerosol produced by ultrahigh frequency spraying of a solution. Two precursor solutions have been used in order to study its influence on the formation temperature of the barium hexaferrite and on the microstructural and magnetic properties. The relationship between in situ temperature, pyrolysis precursor, and textural and magnetic properties of the products obtained is discussed.

Synthesis of barium hexaferrite for magnetic recording media using the KCl flux system

Individual and fine crystals of barium hexaferrite were prepared by a modified flux method using the KCI flux system. Co2+-Ti4+-substituted barium hexaferrite with a homogeneous composition was synthesized at 950° C for 5 h or at 1000° C for 1 h from a mixture of BaCO3, Fe2O3, CoO and TiO2 with 30 wt% KCI added. Laboratory-prepared fine Fe2O3, was preferred because it gave ferrite particles with diameters of 0.2 to 0.4μm. Magnetic properties were controlled by the Co-Ti content in hexaferrite crystals. Coercive force and Curie temperature decreased with the degree of Co-Ti substitution with saturation magnetization held at high value. The present process, from which individual and fine barium hexaferrite crystals can be prepared by using the KCI flux system, is recommended as a means of mass-production of ferrite powders with controlled magnetic properties for use in magnetic recording media.

The synthesis of barium hexaferrite from iron oxide and barium carbonate: II. The role of iron oxide texture

AbstractThe texture of several samples of laboratory‐prepared and commercial iron oxide and their reactivity with barium carbonate (BaCO3.6Fe2O3) has been examined. The first stage of the reaction involves decarbonation with the formation of monoferrite and dynamic thermogravimetry was used to assess mix reactivity. While some of the variation in the behaviour of iron oxide powders could be appreciated from an examination of their texture by scanning electron microscopy and porosity determination, prediction of their reactivity was not possible. In fact the reactivity of the mix can best be considered to give an indication of the efficiency of mixing of the finer iron oxide particles with the barium carbonate. In the subsequent formation of barium hexaferrite the coarse end of the iron oxide particle size range is of primary importance since it controls the rate of completion of the reaction. The larger aggregates in an iron oxide sample can readily be detected by scanning electron microscopy but conclusions regarding reactivity may be erroneous if this coarse material is dispersed during mixing. It was shown by scanning electron microscopy that the least reactive iron oxide sample examined contained aggregates which survived the mixing process employed.

The synthesis of barium hexaferrite from iron oxide and barium carbonate: 1. General features of the reaction

AbstractThe reaction between BaCO3 and Fe2O3 in the proportions necessary for the formation of the hexaferrite has been studied in air. The decarbonation reaction was followed by measuring weight loss isothermally, the formation of hexaferrite by measurement of saturation magnetisation and by X‐ray diffractometry.The only kinetically important intermediate found was the monoferrite and its rate of formation could be correlated with the rate of decarbonation. An unexpected feature of this process was the rapid apparent disintegration of the barium carbonate lattice: this was far more rapid than the weight loss suggested.An examination of the pseudobinary system BaO‐Fe2O3 in air at 1000°C using the electron micro‐probe analyser on reaction products at an interface between partly reacted Fe2O3 and BaCO3 revealed the high barium ferrites 2BaO.Fe2O3; 3BaO.Fe2O3; 5BaO.Fe2O3 but no compound intermediate in composition between mono‐ and hexaferrite, nor any solid solution of Fe2O3 in monoferrite.With powdered reactants the high barium phases were not formed in sufficient concentration and or crystallinity to be revealed by X‐ray diffraction. But their presence could be inferred, because of their reaction with water vapour and/or carbon dioxide, from infrared (i.r.) absorption in the range 700–900 cm−1. An absorption peak at 880 cm−1 appeared to be associated with a very small amount of incompletely reacted material as saturation magnetisation approached the maximum achievable.In the presence of only 0.5% lithium fluoride both decarbonation and the conversion of mono‐ to hexaferrite were greatly accelerated; scanning electron microscopy revealed a big change in crystal size and the form suggested a mechanism involving a liquid phase.