| Layered magnetoelectric(ME) composite is a new smart material, which is widely used in designing many electronic devices such as magnetoelectric sensors, magnetoelectric energy harvester and magnetoelectric frequency multipliers etc. At the basis of both theoretical research and numerical simulation, experimental study is considered as an important way to reveal the response of magnetoelectric composite. At present, experimental works on the magnetoelectric laminate composite mainly focus on its operating mode and mechanism, mechanism on the response of magnetoelectricity, the effects of component materials’ ratio, manufacturing new materials and other aspects. Even so, when it comes to different structural configurations, magnetic field direction, and some nolinear properties of magnetoelectric output signals in a large ac magnetic field, the previous experimental results are not successful completely. Therefore, some researches are conducted in this academic dissertation as follows.1) Firstly, we compared three kinds of layered magnetoelectric composites and tested their magnetoelectric properties respectively. The results show that T/N/P composite presents a relatively larger ME coefficient at a low dc magnetic field as well as an obvious multi-resonant characteristic ranging from 1Hz to 50 kHz. Meanwhile, we obtained the maximum ME coefficients 2.79V/cm Oe and 3.66V/cm Oe at the frequencies of 9.1kHz and 11.1 kHz, respectively. However, N/T/P and T/P/N composites just achieve their maximum ME coefficients 2.25V/cm Oe and 4.84V/cm Oe at the frequencies of 12.7kHz and 12.6kHz. Also, in the further study of T/N/P composite cantilever with a tip mass, it was found that whether with the equably increase of tip mass or the shift of tip mass’s position from near to far, the resonant frequency reduces gradually. Besides, another important way to reduce the resonant frequency is to decrease the clamping length of the cantilever within a low frequency range(1—700Hz).2) Both the ME reponse and the resornant frequency of Terfenol-D/Ni/PZT laminate composite have been studied. A dual peak phenomenon can be observed from the experimental results. It was proved that the dc magnetic field corresponding to two maximum ME coefficients is the main reason for magnetoelectric resonance. At the same time, the amplitude of ac magnetic field have a little influence on ME coefficient within a limited scale.3) We analyzed effects of different ac/dc magnetic angles on ME response. Three magnetic loading modes were set in the experiment. That is, rotating ac magnetic field, dc magnetic field and sample range from 0° to 90°, respectively. The results indicate that the optimum ME coefficient and the dual-peak phenomenon presents an obvious variation under different loading modes. To be specific, the optimum ME coefficient versus rotating angle curves present a linear decrease, a nonlinear variation and decrease first and then increase, respectively. Finally, the angular effect on ME response was explained from the magnetic sensitive characteristic of Terfenol-D and structural model views, and the working mechanism was also discussed in detail.4) The dependences of ME frequency multiplying behaviors on structure and ac/dc magnetic fields are investigated. We found that the results present a marked multi-frequency doubling phenomenon at a large ac magnetic field. And, dc magnetic field have a significant influence on the ME frequency multiplying behaviors. As the dc magnetic field continue to increases, ME frequency multiplying behaviors become weak, whereafter, it disappears gradually. For different samples, ME effects show different variations with the applied magnetic fields:T/P/T laminate present much larger output voltage than others, T/P laminate takes the second place, and 2T/P laminate is the weakest one. |
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