Papers by Keyword: Barium Hexaferrite

Abstract: The main principles of objects of living nature protection from the influence of electromagnetic radiation have been studied. An analysis of various types of protective screens, structures and materials used for their manufacture was carried out. It is proposed to use special concretes based on barium-containing cement with barium hexaferrite aggregate as structural materials to protect the environment from the effects of electromagnetic radiation.

Abstract: 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.

Abstract: The article shows the results of a research in which barium hexaferrite samples of the BaFe₁₁M₁O₁₉ (M= Al, Ti and Mn) composition were obtained by solid-state synthesis. Samples substituted with titanium, aluminum, and manganese were obtained in a tubular furnace at an exposure time of 5 hours at a temperature of 1350°C, the sample, substituted with manganese, it was obtained at a temperature of 1250°C. The chemical composition was controlled using electron microscopy the samples obtained correspond to the initial composition with sufficient accuracy. Hexagonal plates represent the structure of all the obtained samples. According to X-ray phase analysis, all samples are monophasic and have the structure of barium hexaferrite. Using the data of powder X-rays, the parameters of the unit cell of the studied samples were calculated, when iron atoms are substituted by titanium or aluminum or manganese atoms, the crystal lattice is distorted, while its change is not the same for different crystallographic directions. During the doping of barium hexaferrite with titanium, aluminum or manganese atoms, the Curie temperature decreases. This is due to a decrease in the exchange interaction forces during the modification of the barium hexaferrite matrix. The aim of this study was to study the structure and change of the lattice parameters, the Curie temperature, depending on the substitution element.

Abstract: Co₃O₄ powder was added to barium hexaferrite by powder metallurgy process to determine its effect on the magnetic properties. The variation of the addition of Co₃O₄ are 0.0, 0.5, 1.0, 2.0, 3.0, and 5.0 wt%. Characterization and magnetic testing included density calculation, Permagraph test, and XRD were performed in order to elucidate the effect of Co₃O₄ addition to its structure and magnetic properties of barium hexaferrite. The magnetic density obtained was in the ranges of 3.2 - 4.35 g/cm³. From the permagraph test, it is found that the value of remanence (B_r) was in between 1.18 and 1.5 kG. The value of coercivity (H_c) was in the range of 0.594 - 3.366 kOe, and the maximum product energy (BH_max) was found to be in between 0.07 and 0.48 MGOe. From the XRD analysis, it was found that two types of barium hexaferrite were formed, namely barium hexaferrite type M(BaFe₁₂O₁₉) and X(Ba₂Fe₃₀O₄₆). It is concluded that the addition of the Co₃O₄ compound increased the value of magnetic density and decreased magnetic properties.

Abstract: In this study, effect of La substitution on the microstructure, magnetic properties and microwave absorption characteristics of Ba_1-xLa_xFe₁₂O₁₉ (x=0, 0.1, 0.2, 0.3, 0.5, 0.7) is reported. The samples were synthesized through mechanical alloying and solid reaction a temperature 1200 °C for 2 hours. A single-phase material occurred only at x = 0 and 0.1. Additional second phases were existing in all samples with x ≥ 0.2 which led to multi-phase materials. The single phase (x = 0 and 0.1) has a relatively uniform particle size distribution with a mean crystallite size 138 nm. Additional phases of respectively Fe₂O₃ and LaFe₂O₃ were identified in all samples with x ≥ 0.2. Effect of La substitution is to decrease the magneto crystalline anisotropy constant and the saturation magnetization. The latter is due to a decrease in mass fraction of the main magnetic phase. All Ba_1-xLa_xFe₁₂O₁₉ samples have superior microwave characteristics which able to absorb more than 99 % the incoming electromagnetic wave entering the material. The absorption bandwidth is found relatively wide within the frequency range 8-12 GHz.

Abstract: A bonded permanent magnet of Barium hexa Ferrite has been made using powder BaFe₁₂O₁₉ (commercial ferrite) and a polymer of bakelite powder as binder. The composition of bakelite was varried 5% wt. The preparation of sample was begun with mass weighing for each material, then mixed together using ball mill for 1, 6 and 12 hours and using aquades as milling media. The mixed powder is dried in an oven at 110 °C for 4 hours, then the particle size distribution was measured. After that, the dried sample powder was pressed to form a pellet at pressure 40 MPa and temperature about 160 °C for 20 minutes. The characterization of sample pellet was done such as measurement of bulk density, hardness , magnetic properties using VSM and anylisis of microstructure using SEM. The results of the characterization show that the density and magnetic properties tend to increase with increasing of milling time, where the highest density, hardness and highest magnetic properties are achieved at sample with milling time for 12 hours. The value of magnetic properties at this condition are flux magnetic of 530 Gauss, remenance of 3100 Gauss, coercivity of 1,10 kOe.

Abstract: Behavioral characterization of radar absorbent material consisting of Polyaniline (PaNi) and Barium M-Hexaferrite (BaM) has been successfully synthesized by solid state method. Polyaniline conductive material was synthesized using the polymerization method with DBSA dopant. A Radar Absorbing Materials (RAM) is characterized by X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Four Point Probe (FPP), Scanning Electron Microscope (SEM) and Vector Network Analyzer (VNA). The ion Zn ²⁺ is dopping into the BAM structure, where Zn ²⁺ ions replace Fe²⁺ ions in Hexaferrite barium so that the phase becomes soft magnetic materials . RAM and PANi particles are combined with ship paint to form radar wave absorbent coatings. The layer is coated with multilayer geometry on AH 36 type A steel, with thicknesses of 2.4 mm, 3.6 mm, 4.8 mm and 6 mm respectively. The X-band wave absorption was identified by VNA testing, where the maximum reflection loss value was found at 6mm thickness with a reflection loss value - 32.6 dB at 8.4 GHz frequency. Reflection loss values of multilayer variations with a thickness of 2.4 mm, 3.6mm and 4.8mm each have reflection loss values of -8.02 dB, -19.13 dB and -28.9 dB respectively in the x band frequency range.

Abstract: Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica to from a composite on the basis of wave propagation theory have been investigated. Barium hexaferrite, BaFe₁₂O₁₉, was synthesized through ceramic method from stoichiometric mixtures of BaCO₃ and Fe₂O₃ as precursors. The mixture was pelletized under the pressure of 10 MPa and sintered at 1100 °C for 5 hours. Silica in the forms of powder was purified by using HCl. The crystal structure of the samples was characterized using X-ray diffraction (XRD), microstructure was examined using scanning electron microscope (SEM), hysteresis curves recorded by PERMAGRAPH techniques, whereas the microwave absorbing properties for X-band was recorded using a vector network analyzer (VNA). Relative complex permeability and permittivity, and reflection loss values were calculated at given thickness according to transmittance line theory within the range 8.2–12.4 GHz. Based on this study, the layer dimension and frequency that results in low reflection loss can be estimated from the material properties of the barium hexaferrite/silica composite material.

Abstract: Barium hexaferrite BaFe₁₂O₁₉ single crystals hexagonal shaped and sizes of up to 5 mm were grown from barium borate flux. The electro physical parameters of grinded crystals were investigated following the open-ended methodology, using Speag DAK system. Thebtained Debye characteristic for permittivity confirmed the theoretical expectations. The presented results show the specific behavior of the target value in terms of causal models for metal powder materials.

Abstract: Solid state sintered pellets of barium hexaferrite were performed. The Curie temperature of BaFe₁₂O₁₉ pellets were measured with differential scanning colorimetry (DSC). The coefficient of thermal expansion (CTE) of pellets was defined above and below the Curie temperature. The Curie temperature calculated basedon the dilatometry is are in good agreement with the DSC measurements.