The Preparation Of Hexagonal Ferrite Microwave Absorber For Isolator Load

The W type hexagonal ferrite particles were prepared by sol-gelcombustion technique. The products were characterized by TG/SDTA, XRD,SEM, LPSA and absorption loss. Through these tests determined the preparationtechnology, ions doping, compound proportion of ferrite powders/epoxy resin.The surface modification of W type hexagonal ferrite powders by stearic acidwas investigated. The activation exponential, FT-IR, TG, wettability andviscosity were tested. Through these tests determined the modification processesand studied the modification mechanism. The electromagnetic parameters of Wtype hexagonal ferrites were tested by the coaxial method, and the absorbingproperties and absorbing mechanism were studied. The main results are asfollows:(1) A better calcining conditions of preparing the W type hexagonal ferriteparticles:3℃/min temperature rise rate and calcined at1250℃for2hours.BaZnxCo2-xFe16O27(x=0.0,0.6,1.0,1.4,2.0) hexagonal ferrite powders wereprepared according to the above process. The ferrite powders were compositedwith epoxy resin with the mass ratio of2:1and were prepared in the isolatorload absorbing materials. The BaZn0.6Co1.4Fe16O27ferrite powders/epoxy resinwith the mass ratio of8:1had good absorbing properties above X wave band(8GHz to14GHz), the highest of which was3.85dB/mm.(2)The products with excellent modification effect as well as95.2%activation exponential were prepared in the conditions of80℃, with1.5%stearic acid added (mass fraction) and stirring for30min. Stearic acid moleculesoccured chemisorption on the surface of ferrite powders. The surface property offerrite powders modified with stearic acid was changed from hydrophilicity tohydrophobicity. Viscosity was reduced in the organics, and the flow propertiesand the consistency of the ferrite powders and epoxy resin were improved. Theferrite powders and epoxy resin were mixed uniformly, which enhanced themechanical and thermal properties of the composites. (3) W type hexagonal ferrite particles had good absorbing properties at Xwave band (8GHz to12GHz). When d=2.8mm, the minimum reflectivity was-48dB. The main absorbing mechanism of ferrite is the magnetic loss caused bynatural resonance absorption, the secondary cause of which is dielectric losscaused by inherent electric dipole orientation polarization and interfacepolarization.