Reducing losses in inductor core materials allows further miniaturization and increase of efficiency in power converters. Nanocomposites containing superparamagnetic 11 (Formula presented.) 3 nm (Formula presented.) - (Formula presented.) particles in a polyvinyl alcohol polymer matrix were developed as printable and castable inductor core materials for MHz range frequencies. The aqueous synthesis resulted in nanocomposites of well-dispersed particles with volume fractions ranging from 10% to 45%. The nanocomposite is eddy current free, has high volume susceptibility up to 17, and a constant AC response in the Hz–kHz range. Hysteresis measurements at 100–900 kHz show that power losses scale as (Formula presented.) -field squared and with frequency to the power of 1–1.3, indicating that the only loss mechanism is high-frequency hysteresis. For an induced (Formula presented.) -field amplitude of 30 mT, commonly used in inductor core materials for power electronics, the losses are on the order of (Formula presented.) – (Formula presented.) kW (Formula presented.). These losses can be reduced by using more monodisperse particles. The presented nanocomposite is easily integrated into micro-fabrication methods, demonstrated by depositing nanocomposite cores on printed circuit board inductors. The inductors with nanocomposite core, measured up to 100 MHz, display an increase in inductance compared to air-core inductors. This showcases superparamagnetic nanocomposites as relevant candidates for high-frequency applications such as portable electronics

Magnetic relaxation is exploited in innovative biomedical applications of magnetic particles such as magnetic particle imaging (MPI), magnetic fluid hyperthermia, and bio-sensing. Relaxation behavior should be optimized to achieve high performance imaging, efficient heating, and good SNR in bio-sensing. Using two AC susceptometers with overlapping frequency ranges, we have measured the relaxation behavior of a series of monodisperse magnetic particles and demonstrated that this approach is an effective way to probe particle relaxation characteristics from a few Hz to 10 MHz, the frequencies relevant for MPI, hyperthermia, and sensing

A magnetic susceptor in a printable filament form is developed for the induction welding of thermoplastic composites. The susceptor is based on Ni particles embedded in a poly-ether-imide matrix. It is extruded and spooled to form a filament which can then be 3D-printed. The susceptor produces heat by hysteresis losses due to the magnetic properties of the Ni particles. As opposed to other typical electrically conductive heating elements, no percolation threshold needs to be achieved to produce heat as the Ni particles individually heat up when exposed to the induction coil’s magnetic field. The heating efficiency of the susceptor filament and its deposition by the fused filament fabrication technique are demonstrated. The susceptor is used to assemble all thermoplastic composite sandwich panels. The sandwich samples are tested by the flatwise tensile test and a tensile strength of 4.6 MPa is obtained, which is equivalent to or higher than reported strengths for typical aerospace-grade sandwich panels. The printable susceptor opens the way to new induction welding or heating applications as it can be printed on a surface to produce a desired heating pattern.

We provide free space microwave measurements of composites made from carbon fibers and ferromagnetic microwires inclusion focusing on the electromagnetic properties. We observed that a low frequency modulating AC magnetic field allows to distinguish the microwave signals originated by ferromagnetic microwires inclusions from that generated by the carbon fibers.

To control solids circulation and optimize design and operating parameters in a circulating fluidized bed full-loop system, measurement and modeling of solids flow behaviors in an aerated standpipe and inclined pipe were conducted. Different aeration gas flows were injected at the inclined pipe, which was equipped with different orifice sizes of 37 mm, 54 mm and 75 mm, for regulating solids flow rates. The magnetic tracer-tracking method, which only needs to inject one small magnetic tracer for each measurement to follow the main solids flow, was successfully demonstrated for measuring sand particles’ real-time discharge rates, with good accuracy and no calibration requirement. A mathematical model was constructed to predict solids discharge rates and investigate the adverse effect of the pressure gradient in the standpipe bed in a full loop fluidized bed system. The optimization of the solids-return and circulation unit could therefore be achieved with the tools developed in this study.

In the present study, the application of a magnetic tracer-tracking method in measuring solids circulation in a fluidized bed standpipe is investigated, due to its advantages of little intervention and cost efficiency, especially in pressurized systems. The method only needs to inject one small magnetic tracer to follow the main solid flow in the standpipe, therefore predicting particles’ real-time velocities. The measurement accuracy was thoroughly tested via comparing to conventional descending and accumulation methods. Main tracer properties, including tracer shape, density, and magnet core, were considered. Solids flow patterns in the standpipe were also regulated by changing orifice sizes and adding an inclined pipe, for the purpose of investigating the measurement accuracy in various conditions. The adverse effect of a narrow orifice on measurement was addressed via constructing a model that includes sand particles’ non-uniform velocity distribution across the standpipe cross-section. To interpret behaviors of tracers varied in size and density, a mathematical model was constructed to describe forces exerted on the tracer in the solids bed. The behaviors of the tracer immersed into the solids bed were also examined, providing an insight to that in a standpipe with continuous solids circulation. The solids bed density was also regulated by varying the mixture of olivine sand and carbonaceous particles at different proportions. The magnetic tracer-tracking method has been successfully validated, demonstrating good measurement accuracy of solids discharge flow rates in the standpipe, particularly avoiding cumbersome calibration. Moreover, the method can also determine sand waving and oscillated discharge behaviors, which might be related to solids’ stick–slip phenomena and is unlikely to be accurately determined using conventional descending and accumulation methods. 

A method to assemble sandwich panels made of carbon fibre reinforced poly-ether-ether-ketone (CF/PEEK) facesheets and 3D-printed poly-ether-imide (PEI) honeycomb cores using induction welding is presented. Induction heating patterns inside CF/PEEK laminates of variable dimensions are first evaluated with a thermal camera and compared to a COMSOL Multiphysics model. Sandwich samples are then prepared by vacuum-assisted continuous induction welding under parameters selected from the modelling effort. Joining of sandwich panels made of CF/PEEK facesheets by induction welding under vacuum is demonstrated. Facesheets do not deconsolidate in the process and core crushing is avoided. Flatwise skin/core strength of the welded samples reaches up to 7 MPa, above reported performance for thermoset or thermoplastic composite sandwich panels. s

In this paper, we explore the benefits of using a magnetostrictive component in a variable reluctance energy harvester. The intrinsic magnetic field bias and the possibility to utilize magnetic force to achieve pre-stress leads to a synergetic combination between this type of energy harvester and magnetostriction. The proposed energy harvester system, to evaluate the concept, consists of a magnetostrictive cantilever beam with a cubic magnet as proof mass. Galfenol, Fe81.6Ga18.4, is used to implement magnetostriction. Variable reluctance is achieved by fixing the beam parallel to an iron core, with some margin to create an air gap between the tip magnet and core. The mechanical forces of the beam and the magnetic forces lead to a displaced equilibrium position of the beam and thus a pre-stress. Two configurations of the energy harvester were evaluated and compared. The initial configuration uses a simple beam of aluminum substrate and a layer of galfenol with an additional magnet fixing the beam to the core. The modified design reduces the magnetic field bias in the galfenol by replacing approximately half of the length of galfenol with aluminum and adds a layer of soft magnetic material above the galfenol to further reduce the magnetic field bias. The initial system was found to magnetically saturate the galfenol at equilibrium. This provided the opportunity to compare two equivalent systems, with and without a significant magnetostrictive effect on the output voltage. The resonance frequency tuning capability, from modifying the initial distance of the air gap, is shown to be maintained for the modified configuration (140 Hz/mm), while achieving RMS open-circuit coil voltages larger by a factor of two (2.4 V compared to 1.1 V). For a theoretically optimal load, the RMS power was simulated to be 5.1 mW. Given the size of the energy harvester (18.5 cm3) and the excitation acceleration (0.5 g), this results in a performance metric of 1.1 mW/cm3g2.

We provide new experimental results on studies of composites with glass-coated ferromagnetic microwires aligned with the requirements of carbon composites. This work focuses on the free space microwave measurements of composites made from carbon fibers and ferromagnetic microwires inclusion focusing on the electromagnetic properties. We prepared several glass-coated microwires and selected Co-based microwires with optimum soft magnetic properties and high magnetoimpedance effect for composite fabrication. We observed that by using a low frequency modulating AC magnetic field parallel oriented to the ferromagnetic microwires allows us to distinguish the microwave signals originated from the ferromagnetic microwires inclusions from the response generated by the carbon fibers. The location of carbon fibers near magnetic microwires has a critical effect on the response signals (parameters S amplitude) obtained from such composites.

In this work, continuous ferromagnetic microwires were integrated into glass fiber reinforced composite (GFRP) plates. The microwires were placed in a single orientation maintaining a constant distance between them. A vector network analyzer (VNA) and two antennas were placed in the vicinity of the composite plates that was mounted in a universal testing machine. Therewith, reflection and transmission scattering parameters were determined by means of free space measurements, while simultaneously, the composite test specimens were submitted to tensile stresses. Force was progressively increased, and dynamic stress cycles were also applied. No external magnetic fields were applied to the composite structures during the measurements. The obtained results were compared with those generated with the same procedure applied on composite specimens without integrated microwires. The result reveals a clear dependence of scattering parameters with tensile force applied. Outcomes are considered as a baseline for a new detection method that can be further developed. This would allow to monitor GFRP in a non-destructive and contactless operation by embedding continuous ferromagnetic microwires within their structure.