Current-voltage measurements obtained from lead zirconate titanate/nickel bilayered hollow cylindrical magne-toelectric composite showed that a sinusoidal current applied to the copper coil wrapped around the hollow cylinder circumference induces voltage across the lead zirconate titanate layer thickness. The current-voltage coefficient and the maximum induced voltage in lead zirconate titanate at 1 kHz and resonance (60.1 kHz) frequencies increased linearly with the number of the coil turns and the applied current. The resonance frequency corresponds to the electromechanical resonance frequency. The current-voltage coefficient can be significantly improved by optimizing the magnetoelectric structure geometry and/or increasing the number of coil turns. Hollow cylindrical lead zirconate titanate/nickel struc-tures can be potentially used as current sensors.
The electromagnetic and microwave absorbing properties of FeCoB powder composites prepared by single-roller melt-spinning and mechanical milling processes were investigated in this paper.The result indicates that the flake-like powders are obtained.As milling time increases,the flake-like powder particles tend to agglomerate,causing the flake-like powders decrease gradually.The milling time plays an important role in the electromagnetic parameters which relates to the shape and size of the powder particles.The calculation shows that the sample milled for 6 h could achieve an optimal reflection loss of-11.5 dB at 5.8 GHz,with mass fraction of 83%and a matching thickness of1.8 mm.The result also indicates that the microwave absorbing properties of the FeCoB powder composites are adjustable by changing their thickness,and can be applied as a thinner microwave absorbing material in the range of2–8 GHz.
Shen-Gen ZhangHang-Xin ZhuJian-Jun TianDe-An PanBo LiuYan-Tao Kang
The effects of heating rate (ranging from 50 to 300 ℃/s) during the final annealing process on microstructure evolution and magnetic properties of cold rolled non-oriented electrical steel were investigated. It was found that increasing heating rate increased the nucleation temperature and complete recrystallization temperature. At the same time, heating rate increasing could cause the substantially refined structures for the recrystallization grains and this grain refinement would decline when the heating rate was beyond 50 ℃/s. The recrystallization texture exhibited pronounced improvement with heating rate, such as the intensity decrease of <111>ND (normal direction) fiber and the intensity increase of {110}<001> Goss texture component. The texture improvement and grain size refinement caused by heating rate increasing resulted in complicated variation of the magnetic properties. The magnetic induction (B50) keeps increasing while heating rate increases from 15 to 300 ℃/s which is due to the recrystallized texture optimization caused by rapid heating. The core losses (P1.5/50) decrease while heating rate increases from 15 to 100 ℃/s; however, the core losses would increase when heating rate is higher than 100 ℃/s, which is caused by the mean grain size refinement after rapid heating annealing. The results indicate that recrystallization texture and the magnetic properties of the non-oriented electrical steel can be improved definitely by rapid heating during the final annealing treatment.
WANG JianLI JunWANG Xin-fengTIAN Jian-junZHANG Cai-hongZHANG Shen-gen
