Performance of Energy Harvester Using Iron-Gallium Alloy in Free Vibration

We propose a micro energy-harvesting device, using an iron-gallium alloy (Galfenol), capable of generating electrical energy from ambient vibrations. Galfenol is a ductile magnetostrictive material with a high piezomagnetic constant, good machinability, and a large inverse magnetostrictive effect by which magnetization can be varied by mechanical stress. The device consists of two beams of Galfenol combined with iron yokes, coils, and a bias magnet. A bending force applied at the tip of the cantilever yields a flux increase by tensile stress in one beam, and a flux decreases in the other by compression. The time variation of the flux generates a voltage on the wound coils. This energy harvester has advantages over conventional types of device, such as those using piezoelectric materials, with respect to size, and efficiency, and it has high robustness and low electrical impedance. In addition, the structure needs only a low mechanical force to generate electricity. In this paper, the free vibration characteristic to accrue electric energy effectively is examined. From the experimental results, the energy conversion efficiency in the vibration is inverse proportional to the resonant frequency

Thermal properties of N-alkyl-N-methylpyrrolidinium and N-butylpyridinium fluorometallates and physicochemical properties of their melts

A series of N-alkyl-N-methylpyrrolidinium (RMPyr+, where R = E: ethyl, B: butyl, and H: hexyl) and N-butylpyridinium (BPy+) salts based on the fluorocomplex anions, BF₄⁻, PF₆⁻, SbF₆⁻, NbF₆⁻, TaF₆⁻, and WF₇⁻, have been synthesized and their thermal behavior has been investigated. The melting points of the RMPyr⁺ salts are above room temperature with the trend; BMPyrAF₆ < HMPyrAF₆ < EMPyrAF₆ for the hexafluorocomplex salts. Some of the salts containing BMPyr⁺ and HMPyr⁺ exhibit phase transitions in the solid states. Similar melting points of BPy⁺ salts of PF₆⁻, SbF₆⁻, TaF₆⁻, and WF₇⁻ are observed at around 350 K. Ionic conductivity and viscosity for BMPyrNbF₆ (3.0 mS cm⁻¹ and 164 cP at 328 K) are similar to those for BMPyrTaF₆ (3.0 mS cm⁻¹ and 165 cP at 328 K), resulting from the similarity of the anions in size. The activation energies of ionic conductivity for the NbF₆⁻ and TaF₆⁻ salts are 18 and 20 kJ mol⁻¹, and those for viscosity are 23 and 25 kJ mol⁻¹, respectively calculated by Arrhenius equation in the temperature range between 328 and 348 K. Electrochemical windows of BMPyrNbF₆, BMPyrTaF₆, and BMPyrWF₇ are about 4.0, 5.0 and 3.1 V, respectively

2-D Image of Eddy-Current Testing and Dependence of Shape for Notch inside of Narrow Hole by Needle-Type Probe

Eddy-current testing (ECT) has a large contribution to the maintenance of apparatus with a high reliability both in the past and the future. The needle type magnetic probe with the giant magneto-resistance sensor made it possible to inspect minute defects in narrow spaces (groove and hole). Moreover, the high resolution and sensitivity of the detection methodology could observe the ECT signal image inside of hole and groove. In this paper, we discuss the 2-dimensional signal recognition of magnetic fields and distinguish the relationship and discrepancy between a shape of notch inside of narrow hole and a signal image by both experimental and calculated results

Finite Element Analysis of Galfenol Unimorph Vibration Energy Harvester

This paper develops a numerical model to examine the performance of the vibration energy harvester with one-rod (unimorph) of Iron-Gallium (Galfenol). The device\u27s principle of operation is based on inverse magnetostrictive effect of the Galfenol rod. In order to take into consideration the anisotropy of the Galfenol, the Armstrong model is employed that is implemented into a static 3-D finite element model (FEM) of the energy harvester. The predicted results from the numerical model are compared to the measured ones