Papers by Keyword: Magnetic Permeability

Abstract: The work presents the investigations of working out the method of obtaining radio-absorbing composite material based on magnetite nanoparticles and polydimethylsiloxanes. The electron microphotographs of nanoparticles were obtained and the radio-physical characteristics of material in the frequency band of 0.1-8 GHz were measured.

Abstract: Determination of the electromagnetic parameters is an important tool to evaluate the microwave-absorbing characteristic of a novel material. In this context, our research was carried out to investigate the electromagnetic parameters of nanocomposites samples obtained by inclusion of nanostructured Fe₇₂Al₂₃V₅ powders in a resin matrix. Nanostructured Fe₇₂Al₂₃V₅ powders were synthesized by high-energy mechanical alloying (MA) route and characterized using a scanning electron microscopy (SEM). The nanostructured Fe₇₂Al₂₃V₅ powders were dispersed in an epoxy resin matrix. Nanocomposites bulk samples of rectangular section and given thickness were shaped for electromagnetic characterization in an X-band metallic rectangular waveguide. Electromagnetic characterization was performed in terms of measured S_ij scattering parameters. Dielectric permittivity and magnetic permeability spectra were extracted over the microwave X-band via the transmission/reflection technique. Obtained results exhibit how the nature and size of the inclusions affect the electromagnetic parameters in the X-band frequencies.

Abstract: In this study, Co_0,7Zn_1,3W powders were synthesized and investigated at the microwave region. The solid-state reaction method and self-propagating high-temperature synthesis were used to production of the two kinds of hexaferrite powders. The high-frequency magnetic properties under temperature effect have been studied. It is show, that there is a nonlinear dependence on temperature within the 0 – +40 °C temperature range.

Abstract: The present paper investigates the utilization of the magnetic Barkhausen noise and magnetic permeability methods for the nondestructive characterization of annealed non-oriented electrical steel samples which were isothermally annealed in a wide range of temperatures (400°C – 950°C) and subsequently cooled in air. The resulting magnetic properties were compared with the microstructural changes occurring during annealing.

Abstract: The magnetic static permeability of sputtered FeCuNbSiB and electrodeposited NiFe patterns with thicknesses varying from 0.1 to 8 μm has been studied. The permeability varies proportionally with the pattern size/thickness ratio, like for uniformly magnetized patterns. Different hypothesis on this variation have been investigated and a critical analysis favors a demagnetizing effect. The comparison between experimental results and the theoretical value of the demagnetizing factor of squares plates confirms MOKE imaging, i.e. large magnetic domains but a non-uniform magnetization in the samples.

Abstract: Non-oriented silicon iron (NO Fe-Si) alloys are soft magnetic materials used in the construction of medium and high power rotating machines. To obtain efficiency higher than 95%, it is necessary to promote a new design of their magnetic circuits and/or alternative cutting technologies. There were tested steel samples of fully processed non-oriented silicon iron (NO FeSi) grades, M400-65A and M800-65A, with an area of 300 × 30 mm². The magnetic properties were measured with a single strip tester in the range of frequency from 10 ÷ 200 Hz at 1 T peak magnetic polarization. The sheet cutting technologies, involved in this study, are mechanical, laser, water-jetting and electro-erosion.

Abstract: The present paper investigates the utilization of both the magnetic Barkhausen noise and permeability measurements for the nondestructive distinguish of the three welding zones in a welded low carbon steel.

Abstract: We note that for a wide range of porous, especially granular, ferromagnetics used as matrices of magnetic filter-separators, there is still an issue of defining their demagnetizing factor N which has a dramatic effect on the values of average magnetic permeability of these operating units of filter-separators. The work aims at filling the existent gaps in the issue, we supply N values depending on the relative size of such magnets as well as a respective generalizing phenomenological dependence which is characterized by an exponential realtion between the demagnetizing factor and relative size radical. The established relation allows obtaining real values of magnetic permeability of a short filter matrix thus providing an unbiased comparative estimate of its technological workability.

Abstract: The inverse magnetostrictive effect provides a chance to detect the stress by measuring some magnetic parameters. So it is important to learn the effect of stress on some magnetic parameters. A measuring system to measure magnetic permeability and magnetic loss and a device to load uniaxial tension and pressure stress were developed. The result shows that magnetic permeability and magnetic loss increase with uniaxial tension stress increase and decreases with uniaxial pressure stress increase. It is also concluded that the relative change of magnetic permeability and magnetic loss decrease with increase of the included angle between the directions of the stress and magnetic field. These results suggest that magnetic permeability and magnetic loss can be further used to evaluate the stress in low-carbon steel.

Abstract: If TRIP steel with excellent mechanical properties dominated by strain induced martensitic transformation (SIMT) can be applied to a shock absorber in automobiles, it becomes possible to reduce a weight of the automobiles by decreasing the thickness of their components. In order to improve its reliability by clarification of the mechanical properties, it is necessary to evaluate continuous evolution of martensite during deformation in TRIP steel. In the previous studies, volume resistivity and impedance have been measured during deformation. However, these studies have not been succeeded for the evaluation of martensite with higher precision. Here, because of focusing on a characteristic which martensite indicates ferromagnetism, the evolution of martensite is evaluated by measuring relative magnetic permeability in TRIP steel during deformation at various strain rate.