Study On The Microwave Absorbing Properties Of Carbonyl Iron/M Type Barium Ferrite Composites

Magnetic metal and alloy powder becomes an important developing trend of the absorbing material for the high magnetic permeability and high magnetic loss.Flaky soft magnetic powder material shows high-frequency magnetic permeability and it also express better absorption at high frequencies of electromagnetic wave.M type ferrite with high resonance frequency,good dielectric properties and low cost shows the better absorption.In this paper,the flake carbonyl iron powder(CIP),flake FeNi alloy and TiCo doped barium ferrite(Ba M)powders as the absorbing agent has been prepared,and then EPDM rubber matrix composite was prepared as rubber-based absorbing materials.The main research content is as follows:(1)Flaky CIP was prepared though mechanical alloying method by using planetary ball milling method.Flake-shaped Fe Ni alloy particles were prepared by mechanical ball milling and subsequent calcination method using carbonyl iron,carbonyl nickel powder as raw material.Different time of ball mill was studied on the influence of the thickness of powder,and we also studied the influence of the wave absorption performance.The thicknesses of the flake-shaped particles milled for 18 h,20 h,22 h,24 h were about 3 ?m,2.5 ?m,2 ?m,1 ?m,respectively.The sample milled for 24 h shows excellent EM wave absorbing properties and the peak frequency is located at 55 MHz with the reflection value of-39.0 dB with the thickness d=5 cm.(2)TiCo doped barium ferrite(BaM)powders were prepared by traditional ceramic processing.We have explored the influence of the different Ti-Co doping amount on the morphology,structure,electromagnetic and microwave absorption performance of BaM.When the ratio of the Ti-Co doped amount is x = 1.2,the materials shows well absorbing properties for the electromagnetic matching.When the frequency f is up to 1 GHz,the reflectivity reaches to-25 dB.(3)We have prepared the iron material / M type barium ferrite composites.We have explored the absorbing properties of the composites after adding ferrite.When the thickness of the absorbing layer is 2 mm,the sample CIP-BaM has an absorption of less than-10 dB at 4.3 ? 7.6 GHz(3.3 GHz),and FeNi-BaM less than-10 dB absorbing band is 6 ? 12 GHz(6 GHz);when the thickness is 1.5 mm,the sample CIP-BaM in 5.7 ? 11.2 GHz(5.5 GHz)has an absorption of less than-10 dB,and FeNi-Ba M less than-10 dB absorbing frequency band 11 ? 18 GHz(7 GHz).The minimum reflection peak moves to high frequency and has a larger bandwidth.(4)We have prepared different thickness of EPDM-based absorbers use Fe Ni alloy powders as absorbents.The different thicknesses of the absorbing materials have different absorbing properties.The peak of the minimum reflectivity move to low frequency with the increase of the thickness.When the thickness d = 2.083 mm,the minimum reflectivity has reached to-34 dB,the reflectivity of less than-20 d B absorbing band is 5.2 GHz to 9.0 GHz,bandwidth is 3.8 GHz.