Study On Single/Multi-lectrode Cylindrical Magnetoelectric Composites And Exploration Of Magnetic Energy Harvester Prototypes

The magnetoelectric(ME)effect is defined as the induced dielectric polarization under applied magnetic field(H)through interfacial strain coupling of the two phases,or as the induced magnetization in the presence of an applied electric field.Magnetoelectric composites made by combining piezoelectric(PE)and piezomagnetic(PM)materials can lead to remarkable ME,compared with the single phase magnetoelectric,making it a promising candidate for potential applications.In this thesis,the study focuses on investigation of the multiphase magnetoelectric composites which containing Tbi-xDyxFe2-y(Terfenol-D),Terfenol-D-epoxy(TDE),Pb(Zr,Ti)O3(PZT),Ni,and/or Nickel alloys.Designed,Fabricated,and characterized the single/multi-electrode Polymer-bonded(0-3-2)cylindrical magnetoelectric composite,which could be applied to smart devices,to seek the strongest ME coupling for exploration of designing and preparation of the magnetic energy harvester prototypes.Magnetoelectric composites(0-3-2)with bonded Tb1-xDyxFe2-y-epoxy(TDE)and Pb(Zr,Ti)O3 cylindrical ceramics were prepared by the "one-step" compression molding at room temperature.The PZT cylindrical ceramics not only provided the piezoelectric phase,but also acted as a mold for TDE.The axial ME voltage coefficient of the cylindrical composites,aE,A,was studied.The composite with an epoxy content of 14 wt%and 100-150 ?m particle range exhibited better overall ME performance,6 V/cm Oe.This investigation promotes selecting the appropriate polymer content and particle size to optimize fabrication of the polymer-bonded ME.By contrast,the new structure has a larger ME voltage coefficient compared with the effective planar laminated composites due to the self-bound state.The multi-electrode cylindrical magnetoelectric composite,Pb(Zr,Ti)O3/Tb1-xDyxFe2-y/Pb(Zr,Ti)O3(P-T-P),was designed and prepared based on the(0-3-2)cylindrical structure.Compared with the same overall dimensions but different structures T-P and T-P-T-P composites,the hollow P-T-P composite with multi-electrode cylinder structure has doubled ME coefficient and used 35-45%less Tb1-xDyxFe2-y(an expensive piezomagnetic rare earth alloy).The reason for the improvement can be described to the effective working surface conditions and the series multi-electrode effect.The constitutive equation and PM/PE volume fractions have been calculated to optimize the P-T-P composite.The calculation results demonstrated that the P-T-P composite has better ME performance,which is attributed to an optimal volume fraction of the PM phase.The magnetic energy harvester prototype,which based on the polymer-bonded(0-3-2)cylindrical magnetoelectric composite have been designed and prepared.The energy harvesting performance has been studied.The compact magnetic energy harvester could harvest alternative magnetic energy into direct current(electrical energy,up to 1.6 V in the capacitor),which could lit up a F5/5mm red LED at around resonance frequency and saturated magnetic field of the composite.