Search

A nonlinearity in the magnetoelectric coefficient, αMENonlin, of Metglas/Pb(Zr,Ti)O3 (PZT) and Metglas/Pb(Mg1/3,Nb2/3)O3-PbTiO3 (PMN-PT) laminate sensors has been observed. This nonlinearity was found to be dependent on the dc magnetic bias (Hdc) and frequency of the ac drive field (Hac). The maximum value of αMENonlin for both types of composites was found near the electromechanical resonance. For Metglas/PZT laminates, the maximum occurred under a finite bias of Hdc ≈5 Oe; whereas, for Metglas/PMN-PT, the maximum was found near zero dc bias. One application for αMENonlin is a cross-modulation scheme that can shift low frequency signals to higher frequency to achieve lower noise floor. For Metglas/PMN-PT, αMENonlin has another application: removal of the necessity of a dc bias, which helps to design high-sensitivity sensor arrays and gradiometers. [ABSTRACT FROM AUTHOR]

Magnetoelectric composites have shown promise in low power magnetic field sensing with responsive detection of low frequency fields through the modulation of electromechanical resonance by exploiting a nonlinearity in magnetoelastic properties (ΔE effect). There is also the as-of-yet unrealized potential of tuning this effect to further enhance the shift in resonant frequency of these devices. In the present work, the magnetic field sensitivity was modulated in a bending mode stress reconfigurable sensor through the application of uniaxial tensile stress, reaching up to 8% f0/mT. The minimum magnetic noise floor was determined by detecting the frequency shift using a phase locked loop circuit and was found to directly correspond to the maximum in magnetic field sensitivity that resulted from the ΔE effect. [ABSTRACT FROM AUTHOR]

Operated under high magnetic field (>11 T), the toroidal field (TF) system consists of complex conductors using \ Nb3{\ {Sn}} as superconducting material. According to the strand requirements for the ITER TF conductor, bronze processed \ Nb3{\ {Sn}} strands with high superconducting performance have been manufactured using high tin content bronze at WST. The studies on filament diameter, diffusion barrier, sample heat treatment and annealing temperature have been carried out to enhance \ Nb3{\ {Sn}} strand properties. The results of these investigations have been presented. The result indicates that the different filament diameter has a weak influence on the critical current (Ic) value for the different reaction degree. In the manufacturing process the annealing temperature should be kept below 500 ^\circC to realize a high n value. The continuous \ Nb3{\ {Sn}} layer formation on the internal surface of the barrier causes a considerable increase of hysteresis loss when single Nb barrier is used. There is almost no difference of Ic, hysteresis loss and grain morphology for two heat treatments: ITER heat treatment cycle B and WST heat treatment cycle. [ABSTRACT FROM PUBLISHER]

This article presents the design and analysis of a novel dynamic stiffness tuning vibration absorber working with Magnetorheological elastomers (MRE). In this design, the MRE worked in a shear mode, but its MR effect was significantly enhanced by dynamically squeezing the sample thickness with an embedded piezoelectric (PZT) actuator. With this design, both the quasi-static magnetic field and the PZT driven dynamic squeeze strain in the direction of particles chain were properly adjusted to control the vibration of the primary system. The vibration suppression capabilities were theoretically analyzed by the harmonic analysis. A combined control strategy (the tuning strategy and the ON-OFF strategy) and the control system were developed to suppress the vibration of the primary system. The simulation results indicate that the proposed MRE-PZT-based dynamic stiffness-tuning dynamic vibration absorber (DSTDVA) exhibits more effective suppression capabilities than those conventional MRE-based quasi-static tuned vibration absorbers; the stronger the enhanced effect of squeeze strain on MRE's shear storage modulus is, the more effective vibration suppression capabilities the proposed MRE-PZT-based DSTDVA has. [ABSTRACT FROM AUTHOR]

This paper presents two kinds of magnetorheological elastomers (MREs). One is composed of appropriate silicon rubber, carbonyl iron particles and some other materials. It is cured under a strong magnetic field at a room temperature. Its shear modulus change from 0.34MPa at zero magnetic field to 3.34MPa at 1T magnetic field, the relative MR effect reaches 878%. Such high MR effect has not been reported until now. The other is composed by appropriate natural rubber, carbonyl iron particles and some other materials. After the compositions are mixed in a two-roll mill, they are cured under a strong magnetic field according to a temperature profile. The increment of its modulus reaches 3.6MPa, and the relative modulus increment is 133%. Their mechanical properties are also evaluated. All observed results show that the fabricated MREs are utilizable. They have successfully been utilized to adaptive tuned vibration absorbers, which will serve for vibration absorption of vehicles. [ABSTRACT FROM AUTHOR]

The optimization of critical current density in NbTi superconductors involves a complex schedule of heat-treatments, which precipitate normal conducting alfa-Ti precipitates and reduce the dimensions of these precipitates to the optimum size for flux pinning. Final drawing strain is the most important parameter for the optimization of the critical current density. In this paper, high homogeneity Nb47Ti alloy was applied for the fabrication of the NbTi superconductors. The NbTi samples were having the same intermediate stage heat-treatment schedule just varied in the final drawing strain ranging between 4 to 5.5. The critical current of these samples were tested at 4.2 K under different magnetic fields ranging between 2 to 8 Tesla. Based on the results, it was found that the optimal final strain for the NbTi/Cu samples was about 4.8. Jc decreased abruptly after the maximum value has been passed. The effect of the final drawing strain on the Jc in the low magnetic field region was more significant than which in the high magnetic fields. [ABSTRACT FROM PUBLISHER]

We report on a giant tunable enhanced resonant magnetoelectric (ME) coupling in multiferroic magnetostrictive/piezoelectric composite bimorph structures. The approach uses a magnetic/electric field assisted stress-reconfigurable resonance to produce frequency tuning of up to 100%. The studies were performed by laser Doppler spectroscopy. We also show that this principle of a continuously tuned resonance might be used to improve sensitivity for ME magnetic sensors. [ABSTRACT FROM AUTHOR]

This paper reports on the tuning of both magnetic and electric responses with electric and magnetic fields for metglas-Pb (Zr,Ti)O3 based magnetoelectric (ME) heterostructures that can be promising for communication and sensor applications. The hysteresis loop results indicate a change in the in-plane magnetization due to application of voltages that leads to a tuning of the ferromagnetic resonance frequency by up to about 210 MHz with electric field. Furthermore, these structures show a high ME voltage coefficient that results in the detection of a 2 nT ac magnetic field and a low noise floor. [ABSTRACT FROM AUTHOR]

The effect of magnetostrictive layer thickness on the magnetoelectric (ME) response and field sensitivity of Pb(Zr,Ti)O3-metglas based sandwiched ME heterostructures has been studied. Such structures hold promise for sensor applications. The increase in metglas thickness results in a significant increase in the ME response and magnetic field sensitivity. The ME coefficient and field sensitivity increase by about 1.5–1.75 and 2.7 times, respectively, for a structure with 150 μm thick six metglas layers on both sides of the Pb(Zr,Ti)O3, in comparison to a 50 μm thick two layered structure. [ABSTRACT FROM AUTHOR]