Abstract-Pulsed-current sensors require transducers constituted of magnetic materials with high magnetic permeability in a frequency range compatible with the period and the frequency of the current pulse. The use of ferrites in this application has the advantage of low cost and low losses in high frequencies. The aim of this work is to present a procedure for selection of the ceramic processing route of Ni-Zn ferrite for application in a pulsed-current sensor. The ferrite samples were prepared under different processing parameters and characterized in terms of microstructure, chemical analysis, complex magnetic permeability, and magnetic hysteresis. The chosen processing route included high energy milling of the pre-sintered powder, its disaggregation before sample forming, and sintering of the samples in air for 2 h at 1300 • C. Tests were performed and it was verified that using this processing route for the fabrication of the sensor's core it was possible to monitor pulses of 0.1-1.0 µs.
By measurements of ac susceptibility we have studied the phase boundaries on MnP in the vicinity of the point where the ferromagnetic, the cone, and the fan phases meet. The present data are consistent with the assignment of second order to the cone-fan transition line. This line, then, ends at a critical end point on the ferromagnetic boundary.
The electromagnetic properties of Carbon-Graphene Xerogel (CGX), Flaky graphite (GR) and Nickel-Zinc ferrite (FeNiZn) composites in polystyrene (PS) matrix were studied in the X-Band range (8.2 -12.4 GHz). In this work the Expanded Polystyrene (EPS) waste material was processed into polystyrene through the recycling of EPS. The polystyrene obtained was utilized as dielectric matrix, mainly because PS is a wellknown organic polymer that presents low dielectric loss and light weight, which contribute to applications in composites for the aerospace field. In order to produce the final composite specimens, the CGX additive was previously synthesized through a sustainable method that employed the use of waste from the paper and pulp industry (black liquor). Afterwards, the morphological and structural analysis were made through Scanning Electron Microscope (SEM) and Raman Spectrometer, respectively. On the other hand, the magnetic ferrite material, FeNiZn, was obtained for the composite production through calcination, whereas the GR utilized was commercially obtained. It was observed that the increase of CGX and GR influenced on the increase of the Complex Permittivity, and that 10 wt% CGX + 50wt% FeNiZn composite sample demonstrated an absorption peak at 10.5 GHz. The results are relevant concerning the recycling of EPS waste through its use as dielectric matrix, thus developing greener and low-weight composite materials to be used in microwave applications.
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