Control of the Length of Fe_73.5Si_13.5Nb₃Cu₁B₉ Microwires to Be Used for Magnetic and Microwave Absorbing Purposes

Abstract

A combination of high energy ball milling, vacuum filtering and sedimentation processes has been demonstrated to be a useful approach to reduce, in a controlled way, the length of as-cast Fe73.5Si13.5Nb3Cu1B9 amorphous magnetic microwires (MWs) and annealed material at 550 ºC in nitrogen condidions. Homogeneous compositional microstructures with fairly narrow size distributions between 1300 µm and 11.7 µm are achieved exhibiting tunable response as a soft magnetic material and as a microwave absorber. From the magnetic perspective, the soft magnetic character is increased with smaller length of the MWs whereas the remanence has the opposite behavior mainly due to the structural defects and the loss of the shape anisotropy.From the microwave absorption perspective, a novel potential applicability is tested in these refined microstructures. This innovation consists of coatings based on commercial paints with a filling percentage of 0.55% of MWs with different lengths deposited on metallic sheets. Large attenuation values around -40 dB are obtained in narrow spectral windows located in the GHz range and their position can be varied by combining different optimized lengths of MW. As an

Microwave Absorption Properties of Magnetite Particles Extracted from Nickel Slag

“…So far, however, there has been little discussion on the EM wave absorption of MPs gained from molten slag. Furthermore, considering microwave absorption strongly correlates with particle size [18], we conduct ball milling to enhance the EM wave properties of MPs since ball milling can conveniently control the size of MPs [19]. At the same time, the silicates can strip off during the ball milling process, resulting in the enhancement of the MPs' magnetic properties.…”

Crystal growth control of rod-shaped ε-Fe2O3 nanocrystals

“…This observed trend corresponds to the reported trend where H c increases as the particle size increases because the superparamagnetic effect operates in a small particle region. 32,36,37 The magnetization values for 1-5 become higher as the calcination temperature increases. However, in 6 and 7, the magnetization values are low, even though the calcination temperature is high.…”

Boosting the Tunable Microwave Scattering Signature of Sensing Array Platforms Consisting of Amorphous Ferromagnetic Fe2.25Co72.75Si10B15 Microwires and Its Amplification by Intercalating Cu Microwires

“…In turn, the XRD pattern (Figure 2b) displays broad amorphous shoulders located one below 30 • , and two around 45 • and~82 • . The first contribution corresponds to the Pyrex XRD signature (red asterisk) [37] and the other contributions (black asterisks) are associated with the amorphous Co-based alloys [50]. Regarding the magnetic properties, a high saturation magnetization of~81 emu/g (that is normalized to the magnetic mass) and an extremely low coercivity around~0.2 Oe (Figure 2c) are shown.…”

“…Interestingly, the most notable changes are observed when two sensing platforms are arranged in tandem (Figure 4a3), since a huge enhancement of the S21 minimum intensity up to ~ −47.9 dB is recorded (Figure 4b3). These values are highly competitive [37], since an enormous increase of the S21 coefficient of ~1041% is achieved by changing from configuration 1 to 3. In turn, a drastic narrowing of the scattering is also registered (FWHM = 0.03 GHz), shifting the minimum frequency to ~2.21 GHz.…”

“…In this line, wireless systems that are composed by MWs with GMI effects in the microwave range have been recently reported [36]. In the presence of electromagnetic waves, the frequency that is associated to the maximum scattering is determined by the length of the MW through a dipole electric resonance [37]. The scattering coefficient (S 21 ) can be modulated by means of the application of a DC or AC magnetic field in the presence of GHz-ranged electromagnetic wave due to the GMI effect observed in Co-based MWs.…”