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In this study, we present a novel low-frequency magnetic field energy harvester (EH) employing beryllium bronze/Pb(Zr,Ti)O3 ceramic composited dual-beam structures with tip magnets attached to the inner and outer beams. This design incorporates the internal magnetic-coupled (IMC) effect, resulting in significantly enhanced coupling ability and a wide bandwidth. The validity of the IMC mechanism is confirmed through theoretical formulas and numerical simulations. By leveraging the IMC condition, the EH achieves an expanded bandwidth, which increases from 22 to 43 Hz. Moreover, the total output voltages at the inherent resonance and internal resonance are boosted by 15.4% and 32%, respectively. The performance of the IMC-EH can be further improved by increasing the number of the endmost magnets. Experimental investigations reveal that the IMC-EH generates a maximum RMS output power density of 56.25 μW Oe−2 cm−3, surpassing existing magnetically coupled piezoelectric energy harvesters. Remarkably, even under an ambient magnetic field as low as 1 Oe, the proposed IMC-EH still yields a total output power of 185 μW, sufficient to continuously power 26 LEDs in real time. This demonstrates its potential as a promising solution for low-power consumption small electronics. Furthermore, the implications of this work extend beyond its immediate benefits, as it inspires the design of future self-powered wireless sensor networks in the context of the Internet of Things. [ABSTRACT FROM AUTHOR]

This paper proposes analytical solutions for the resonant radiation performance of bending-mode magnetoelectric (ME) antennas. The strain-mediated Converse ME (CME) coupling model of bending-mode ME antennas is first established by solving nonlinear constitutive equations and bending governing equations using the elastic mechanics method. Then, the calculated magnetic flux and electric displacement are employed to propose a resonant radiation field model based on the dipole method. The numerical results for the CME coefficient show a good agreement with the experimental data. It can be observed that the volume fraction ratio of the piezoelectric layer can control the CME coefficient and radiation efficiency with the same variation trend since it can determine the bending strain via changing the location of the neutral layer of the ME antennas, which also demonstrates the strain-mediated essence of the ME antennas. In addition, the volume fraction ratio can tune the resonant frequency within a wide range. The gain of the ME antenna is stable and higher than −168 dB with the volume fraction ratio ranging from 0.2 to 0.7. The tensile stress and compressive stress have the opposite effect on the resonant frequency at low and high bias magnetic fields. Meanwhile, the tensile (compressive) stress is beneficial for both the radiation and gain in the low (high) bias field region. This model may facilitate the understanding of the bending-mode radiation mechanism of ME antennas and provide a basis for designing asymmetric ME antennas. [ABSTRACT FROM AUTHOR]

This study investigated the impact of BaO/Al2O3 molar ratio on the electrical conductivity and Al coordination state of CaO–MgO–SiO2–Al2O3–BaO slag using four-electrode technique and 27Al MAS-NMR spectroscopy, respectively. With an increasing BaO/Al2O3 molar ratio from 0.14 to 0.36, BaO preferentially participated in charge compensation of Al3+, which facilitated the transition from AlO5 and AlO6 structures to AlO4 structure and increased the stability of AlO4 tetrahedra, thus enhancing the slag's polymerization and reducing its electrical conductivity. However, once the compensation achieved equilibrium, remaining BaO was involved in depolymerizing the tetrahedral structure and promoting the formation of AlO5 and AlO6 structures. Consequently, the decreased degree of polymerization and increased concentration of free ions together led to an increase in electrical conductivity. However, the increased migration resistance due to the large radius of Ba2+ ion is responsible for the electrical conductivity minimum near the molar ratio of 0.43. [ABSTRACT FROM AUTHOR]

Anionic defects of H− (H∙O) and oxygen vacancies with trapped electrons (V∙O) have been built in the lattice of a hydrothermally derived perovskite (Ba5Nb4O15, BNO) by CaH2 reduction in Ar flow at 600 °C for 12 h. The formed anionic defects in the CaH2-reduced BNO (CaBNO) have been found to improve drastically the ammonia synthesis activity of Ru/CaBNO by donating electrons from both H∙O and/or V∙O to Ru atoms. The stoichiometry of H∙O and V∙O has been determined by TPR and TPO method, respectively. The H∙O defects have been proved to react with N2 under ammonia synthesis conditions via TPD, XPS measurements and isotope (D2) reaction, which provides secondary pathways for ammonia synthesis. Kinetic studies revealed that oxygen vacancies accept spilledover H atoms from Ru particles to alleviate the H2 poisoning effect. Cs-promoter has been demonstrated to accelerate the formation of anionic defects in CaBNO under ammonia synthesis reactions. Anionic defects (V∙O and H∙O) formed in the lattice of Ba5Nb4O15 perovskite via CaH2-reduction drastically promote the ammonia synthesis activity of Cs-Ru/CaBNO catalyst [ABSTRACT FROM AUTHOR]