Preparation And Properties Of Magnetoelectric Oxides With Biological Hierarchical Structure

The material is an important foundation of human civilization, whichhas an important impact on the progress of society. In addition to chemicalcomposition, the properties of materials most depend on their structures.When materials have the same composition in different structures, theyoften exhibit distinct properties and characteristics. The main researchesare reflected in two aspects: one is the study on the structure andperformance of existing materials; the other is the design and preparationof the material with hierarchical structure having excellent performance.The excellent structures and properties of some living creatures inspirepeople to make and update new materials. After millions of years ofevolution, biological species form a variety of complex hierarchical finemicrostructure. The intercoupling of these fine structure and materialsshows the integration between structure and function.The special grading fine structure is possessed by the butterfly wings.The chitin, which forms flakes, has different refractive indices from thefilling air. Incident light in the hierarchical structures of butterfly wingswill produce scatter, interference and diffraction of an optical effect,making butterfly wing exhibit different colors. In addition to color change,certain butterflies also have a special ability to capture light. Though thecomponents of butterflies are simple, the complex and volatile hierarchicalstructures make courtship, predation and so on possible. Not only for their own life, the fine structures of butterflies have important implications, butalso they provide new inspiration and guidance to design materials.To our knowledge, previous researches mainly focused on preparationand optical properties of binary oxides. Researches on multiple oxides,especially magnetoelectricity oxides are rarely reported. In this study, themorph-genetic materials fabrication theory was applied to fabricatemultiple magnetoelectricity oxides with biological hierarchical structure,which provides new methods and ideas for reparation of magneticmaterials. Two kinds of different butterfly wings were used as originaltemplates to synthesis iron bismuth and zinc ferrite functional materials.Preparation and properties of magnetoelectric oxides with biologicalhierarchical structure were studied. Main research work and results are asfollows:1) A novel approach for BFO-NBT nanopowders by a sol-gel processhas been developed. The adding of NBT and excess sodium source couldsuppress the formation of secondary phases, thus, obtaining singleperovskite phase becomes easier. The band gap of the BFO-NBT catalystis estimated about2.08eV. The visible-light photocatalytic and magneticproperties of BFO-NBT nanopowders were investigated and it was foundthat BFO-NBT nanopowders exhibit high photocatalytic activity and weakferromagnetism at room temperature. BFO-NBT is a kind of newnarrowband gap semiconductor visible-light photocatalyst with broadapplication prospects. Furthermore, it is a prime candidate forroom-temperature magnetoelectric applications.2) Selected two kinds of butterflys: Shirozu and Papilio parisbutterfly wings as original templates to fabricate magnetoelectric oxides.The effects of synthesis’ parameters are carefully analyzed, for instanceproper precursors. By using XRD, FESEM, TEM characterization methods,the crystal information and detailed nanostructures of thesemagnetoelectric oxides are well characterized. It is found that themorphologies of the original templates are well conserved in these magnetoelectric oxides.3) BFO–NBT with ordered macropores was synthesized from Shirozubutterfly wings by a sol–gel method followed by calcination, whichreplicated not only the outer but also the inner and more complex surfacesof the butterfly wings. The resultant BFO–NBT replica presents enhancedcatalytic activity owing to the well-distributed macropores formed in situ.It is expected that our method will open up new avenues for the synthesisof multiferroic materials with hierarchical structures, which may formapplications as semiconductor visible-light photocatalyst and novelmagnetoelectric devices.4) ZFO with biological hierarchical structure was synthesized fromShirozu and Papilio paris butterfly wings by a sol–gel method followed bycalcination, which replicated not only the outer but also the inner and morecomplex surfaces of the butterfly wings. ZFO replica presents bettermagnetic properties and specific capacitance owing to the QHS formed insitu. It is expected that our method will open up new avenues for thesynthesis of ZFO materials with hierarchical structures, which may formapplications as supercapacitors and novel magnetic devices.