Preparation Of Tetrapod Zno Modified By Cofe₂o₄ And The Mocrowave Absorbing Properties

Zinc oxide is a kind of multifunctional semiconductor crystal materials. Becauseof its low density, large aspect ratio and easy-forming three-dimensional networks, thetetrapod zinc oxide whiskers (T-ZnOw)with special morphology is excellent to act asthe electromagnetic wave absorber, composite reinforcement, damping and anti-slipmaterials. Exploring the preparation process and investigating the effect ofmodification on the electromagnetic properties of T-ZnOw, are important issues intheoretical and practical aspect for the development of the applications of T-ZnOw.T-ZnOw were prepared by thermal evaporation. The ratio of zinc to graphite,zinc to zinc acetate, the evaporation temperature and holding time, were studied. Thenthe growth mechanism of T-ZnOw was discussed. T-ZnOw/CoFe₂O₄ compositepowder can be obtained via chemical coprecipitation, and the influence on itselectromagnetic properties was investigated. T-ZnOw/CoFe₂O₄ was filled into theepoxy by molding method in different content and the absorbing properties werecompared. Besides, carbon nanotubes (CNT) covered with ZnO and polygonalstar-like ZnO were fabricated, and then the electrical and magnetic properties of themwere investigated.The results showed that the proportion of mixed powders and holding time hadrelatively minor influence on the T-ZnOw growth, but the evaporation temperaturewas an important impact on the final morphology of ZnO. When the zinc and graphitein the mass ratio of 5:1, holding at 950℃for 5min, it is available to obtain the bestmorphology of T-ZnOw, as well as a high purity, good crystallinity and high yield.According to comparison of the products T-ZnOw, T-ZnOw/CoFe₂O₄, CNT/ZnO andpolygonal star-like ZnO, it noticed that, the electromagnetic properties ofT-ZnOw/CoFe₂O₄ were reduced because of CoFe₂O₄ modification to T-ZnOw. Asincrease of the CoFe₂O₄ content, the dielectric constant of T-ZnOw/CoFe₂O₄ waslower than T-ZnOw without modification, and T-ZnOw/CoFe₂O₄ filled in epoxy resinhas the largest reflectivity around at -3dB. It was also indicated that the dielectricconstant of CNT/ZnO was higher than T-ZnOw, but polygonal star-like ZnO waslower than T-ZnOw because of different morphology.