Regulating orientation growth plays a dominant role in enhancing dielectric properties for the electromagnetic(EM)functional materials,which faces a huge challenge in the synthesis method.By sprayannealing strategy,hi...Regulating orientation growth plays a dominant role in enhancing dielectric properties for the electromagnetic(EM)functional materials,which faces a huge challenge in the synthesis method.By sprayannealing strategy,hierarchical ZnO microspheres assembled by ZnO nanorods and nanoparticles were successfully fabricated.With confined microsphere space and controlling crystal growth,oriented ZnO nanorods possess rich defects,Zn-polar,O-polar faces,and high permittivity.Meanwhile,temperaturedependency of exposed polarization surfaces is discovered in the semiconductor ZnO nanoparticles with evolved aspect ratios.As pure dielectric EM wave absorption material,the hierarchical ZnO microsphere exhibits adjustable complex permittivity and polarization behaviors.When the thickness is 2.4 mm,the hierarchical ZnO-1 absorber shows the widest efficient absorption(RL≤–10 d B)region from 9.9 to18.0 GHz(8.1 GHz,^50.6%testing frequency).The minimum reflection loss(RL)of ZnO-1 can reach–31.5 d B at only 2.0 mm.Because of the outstanding dielectric loss ability and wide absorption frequency,large-scale hierarchical ZnO microspheres can be a potential EM absorption candidate.展开更多
Microspheres covered with ZnO nanowires were fabricated by oxidative evaporation of pure zinc powder without catalyst at 450℃. X-my diffraction （XRD） demonstrates that the as-obtained sample can be indexed to high ...Microspheres covered with ZnO nanowires were fabricated by oxidative evaporation of pure zinc powder without catalyst at 450℃. X-my diffraction （XRD） demonstrates that the as-obtained sample can be indexed to high crystaUinity with wurtzite structure. The structural features associated with different growth stages were monitored using scanning elec- tron microscope （SEM）, which described the direct observation nucleation and growth process. Meanwhile, room temperature photoluminescence （PL） spectrum showed a UV emission at -388 nm and a broad green emission at -505 nm. The ZnO nanowires with the self-catalyzed growth mechanism were discussed in detail.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51725101,11727807,51672050,61790581,22088101)the Ministry of Science and Technology of China(No.2018YFA0209102)the Infrastructure and Facility Construction Project of Zhejiang Laboratory。
文摘Regulating orientation growth plays a dominant role in enhancing dielectric properties for the electromagnetic(EM)functional materials,which faces a huge challenge in the synthesis method.By sprayannealing strategy,hierarchical ZnO microspheres assembled by ZnO nanorods and nanoparticles were successfully fabricated.With confined microsphere space and controlling crystal growth,oriented ZnO nanorods possess rich defects,Zn-polar,O-polar faces,and high permittivity.Meanwhile,temperaturedependency of exposed polarization surfaces is discovered in the semiconductor ZnO nanoparticles with evolved aspect ratios.As pure dielectric EM wave absorption material,the hierarchical ZnO microsphere exhibits adjustable complex permittivity and polarization behaviors.When the thickness is 2.4 mm,the hierarchical ZnO-1 absorber shows the widest efficient absorption(RL≤–10 d B)region from 9.9 to18.0 GHz(8.1 GHz,^50.6%testing frequency).The minimum reflection loss(RL)of ZnO-1 can reach–31.5 d B at only 2.0 mm.Because of the outstanding dielectric loss ability and wide absorption frequency,large-scale hierarchical ZnO microspheres can be a potential EM absorption candidate.
文摘Microspheres covered with ZnO nanowires were fabricated by oxidative evaporation of pure zinc powder without catalyst at 450℃. X-my diffraction （XRD） demonstrates that the as-obtained sample can be indexed to high crystaUinity with wurtzite structure. The structural features associated with different growth stages were monitored using scanning elec- tron microscope （SEM）, which described the direct observation nucleation and growth process. Meanwhile, room temperature photoluminescence （PL） spectrum showed a UV emission at -388 nm and a broad green emission at -505 nm. The ZnO nanowires with the self-catalyzed growth mechanism were discussed in detail.
