The Preparation Of Barium Ferrite Magnetic Materials And The Research Of Wave Absorption Performance

The microwave absorbing materials have being taken much more attention due to therapid growing of radar, microwave communication and electronic technique, as well as theneed of stealth technique, Microwave dark room and anti-electromagnetic interference. Ferriteabsorbing materials is a kind of both magnetic loss and dielectric loss of microwave absorbingmaterials. In the text, the latest research progress and preparation method of microwaveabsorbing materials such as barium ferrite and barium ferrite/cenospheres compositeabsorbing materials were introduced mainly. Due to possessing good size, relatively stronganisotropy and moderated saturation magnetization, barium ferrites are widely utilised aspermanent magnets for high-density magnetic recording, high performance permanentmagnets, microwave devices and bubble domain memories and applications in civilian andmilitary technology, and it has attracted much attention.The nanometer powder of barium ferrites with magneto-plumbite type structure wasprepared by a sol-gel method. Citric acid method as a solution-based method, which allowsmixing of precursors at the molecular level, has an advantage in the preparation of ultrafinematerials.(1)To optimize the process conditions, the amounts of citric acid, the substitution amounts,pH value, calcination temperature and holding time were determined to prepare pure smallerparticle size and fine well-dispersed Ba(Ni0.5Mg0.45Co0.05)xFe12-xO19(x=0，1，2，3)nano-powder with citric acid method，and orthogonal experimental is designed. Meanwhile onthe basis of orthogonal experiment, two single factor, substitution quantity X and the dosageof citric acid variable, are considered to impact on its electromagnetic performance.Ultimately we have obtained the best synthesis condition.(2)Effects of microstructures and electromagnetic properties in ion-substitutionscondition have been investigated. Ni，Mg and Co ion instead of Fe ion in M type bariumferrite can alter microstructures and magnetic properties of M-type barium ferrites to satisfyvarious requirements in different application realms. The magnetic properties and Wave absorption performance changed differently with increasing replace quantity. The resultsindicate that: the single phase barium ferrite Ba(NiMg0.9Co0.1)Fe10O19nano-powder isprepared in the best synthesis condition, which possesses the largest saturation magnetization,and a resonance peak at12GHz with the optimum reflection rate of-16.2dB(thickness of2.0mm)(3)In order to achieve better absorbing property of Ba(NiMg0.9Co0.1)Fe10O19，it isimportant to choose two cenosphere for composite materials. The single phase ofBa(NiMg0.9Co0.1)Fe10O19can be coated on the cenospheres. Compared with theelectromagnetic properties of Ba(NiMg0.9Co0.1)Fe10O19, which also prepared by sol-gelmethod, their dielectric loss tangent and magnetic loss tangent have different frequencydependences. Due to adding cenosphere, wave absorption performance ofBa(NiMg0.9Co0.1)Fe10O19composite become poor, and its key experiment factors areconsidered. In order to achieve good absorbing property，it is important for us to chooseappropriate cenospheres and control the thickness the match.