Microwave programmable response of Co-based microwire polymer composites through wire microstructure and arrangement optimization

Abstract

Traditional approaches to realize microwave tunability in microwire polymer composites which mainly rely on topological factors, magnetic field/stress stimuli, and hybridization are burdensome and restricted to rather narrow band frequencies. This work presents a facile strategy based on a single component tunable medium to program the transmission response over wide frequency bands. Structural modification of one type of microwire through suitable current annealing and arrangement of the annealed wires in multiple combinations were sufficient to distinctly red-shift the transmission dip frequency of the composites. Such one wire control-strategy endorsed a programmable multivariable system grounded on the variations in both the overall array conductivity or "effective" area determined by the wires arrangement and the relaxation time dictated by the annealing degree of microwires. These results can be used to prescribe transmission frequency bands of desired features via diverse microwire arrays and microwave performance from a single component to composite system design. phenomena/microwave absorption) have been shown in composites containing such wires, their electromagnetic response is limited to topological factors and magnetic field/stress stimuli [3][4][5][6][7]. Most recently, inspired by the enhancement in the mechanical and electromagnetic properties of hybrid composites by the addition of nano-carbons [8-11] we adopted the multiscale design philosophy by adding carbon fillers into the microwire composites [12,13]. However, such an approach required delicate control and fine-tuning of the constitutive parameters of the nano-carbons.Considering that the wires' intrinsic electromagnetic parameters relate to their microstructure, we propose to add to these methods a programming-based strategy by incorporating arrays of the same type of microwire but with different internal structure and adjusting their combination within the composite. Apart from doping with metallic elements such as Cu, Cr, Nb, the microstructure of the microwires and their electromagnetic properties can be conveniently tailored by current annealing, which promotes internal stress relaxation or redistribution and alteration in domain structure.Thus, the approach presented here is to implement different DC current-annealing

Vertical interface augmented tunability of scattering spectra in ferromagnetic microwire/silicone rubber metacomposites

“…For the 40 mAannealed sample, very fine particles smaller than 5 nm are uniformly distributed within the amorphous matrix. The darker droplet-like nanoparticles in the annealed samples mainly consist of heavier elements i.e., Co and Fe, while the brighter droplets correspond to the lighter elements Si and B [9,24]. The second type of composite corresponds to incorporating the as-cast A and annealed short-cut wires X (where X corresponds to B or C annealed wires) in separated regions and variable proportion in the matrix ( Fig.…”

“…where l s and s ii refer to the magnetostriction coefficient and the dominant internal stress component, respectively [9,26]. The internal stresses s ii of the wires can be redistributed or relieved by modifying the microstructure of the wires through annealing improving the magnetic softness.…”

“…Beyond those methods, we have recently proposed a programming-based strategy using the microwire (microstructurally modified by current annealing) as a code unit and different wire combinations as the code pattern [9,10]. Although such approach enabled the modulation of scattering properties to a large extent, strategies other than increasing the number of components and modifying microstructure have not yet been exploited.…”

“…The produced microwires were currentannealed under different DC currents of 30 and 40 mA for 10 min by mechanically removing the glass coat from the wire ends to allow electrical contact. The changes in DC resistance of the current-annealed microwires were monitored with a digital multi-meter showing a considerable drop for the 40 mA treated-wire which is related to the onset of crystallization and larger grain size due to the rise in temperature [9,22]. The microstructure of the as-cast and current-annealed wires consists mainly of nanocrystalline droplets embedded in amorphous matrix [23].…”

Pattern Reconfigurable Microstrip Patch Antenna Based on Shape Memory Alloys for Automobile Applications

“…The transmission coefficient (S 21 ) is a measure of transmission loss used to understand the microwave properties of the antenna, and to program the microwave properties of microwire array composites via a single wire component subjected to different current annealing conditions and arrangements in the polymer matrix. The variations in transmission spectra featuring in the composites could be explained by the dynamic wire-wire interactions, considering the differences in domain structure and magnetic tensors between the as-cast and annealed wires incorporated in the array, 27 and the microwave properties of composites containing Fe-based ferromagnetic microwires and carbon fibers. A transmission window observed at 1-6 GHz demonstrates a double-negative, i.e., metamaterial characteristics in the composites containing short-cut carbon fibers and a parallel array of microwires.…”