Effect Of High-Energy Ball Milling Parameters On Electromagnetic Performance Of Microwave Absorbing Materials

High-energy ball milling method,because of control,production,cost,efficiency and so on,has become an important method for the preparation of absorbing materials.High-energy ball milling is not only an effective method for the preparation of absorbing materials powder,but also an important control means of electromagnetic parameters of absorbing materials.This paper is mainly about the effects of shape,material,size and proportion of milling media on the microstructure and the electromagnetic parameters of carbonyl iron powder absorbing materials and analyze these factors systematiclly.The paper includes the following studies:(1)Two kinds of ball-milling media shapes,namely spherical and cylindrical,are used to study the micro-morphology,electromagnetic parameters and the microwave-absorbing properties of carbonyl iron powder absorbing materials prepared by ball milling.The results show that,compared with the spherical milling media,the cylindrical grinding media is more conducive to keep the uniform small structure of the ball milling material,and the electromagnetic parameters of the ball mill materials are lower than that of the ball milling media.The carbonyl iron absorbing materials after ball milling are characterized by ?-Fe phase structure,and the magnetic loss plays a major role in the total loss.When the thickness of the absorbing layer is 1 mm,the carbonyl iron powder absorbing material with the ball milling media for 10 hours has the minimum reflection loss value,the reflection loss is-9.8 dB at the frequency of 9.9 GHz,and the reflection loss is lower than-5dB in 4.8 ~18 GHz and lower than-7.5 dB in the frequency band of 8.1 GHz(6.5 ~ 14.6 GHz).It has a wide frequency width and is suitable as a microwave absorber with thin thickness,wide frequency band,and good performance of absorbing electromagnetic waves in low and middle frequency radar wave bands.(2)The effects of milling media materials on the microstructure,electromagnetic parameters and microwave absorbing properties of carbonyl iron powder absorbing materials were studied.The research work was carried out with two kinds of materials,namely cemented carbide and stainless steel.The experimental results show that the carbonyl iron powder absorbing materials after ball milling all represent lamellar structure,and are characterized by ?-Fe phase structure,and the magnetic loss plays a major role in the total loss.Compared with the stainless steel ball milling media,at the same ball milling time,the carbide grinding media is more conducive to make the ball milling materials flaky,resulting in higher permittivity and permeability of the carbonyl iron powder and milling efficiency.Carbide ball milling media is hard to wear,and very suitable for batch processing of materials.When the thickness of the absorbing layer is 1 mm,the carbonyl iron powder absorbing material has the minimum reflection loss value,the reflection loss is-8.1dB at 6.1GHz frequency,and the bandwidth of the reflection loss lower than-5dB reaches 8.1GHz(3.5 ~ 11.6 GHz),and the material is suitable as a microwave absorber with thin thickness,frequency bandwidth,low frequency,and great performance of absorbing electromagnetic waves in low and middle frequency radar wave bands.(3)The effects of size and ratio of milling media on the microstructure,electromagnetic parameters and microwave absorbing properties of carbonyl iron powder absorbing materials were studied.The research work was carried out with five kinds of size and ratio of ball mill media(weight ratio of large and small ball milling media is 3:1 / 2:1 / 1:1 / 1:2 / 1:3,respectively).Experiment demonstrates that the carbonyl iron powder absorbing materials after high energy ball milling represent flaky structure,and the increase of the average size of the ball milling media is not proportional to the flaky size of the absorber.Besides,the carbonyl iron powder after high energy ball milling showed ?-Fe phase structure,and the magnetic loss plays a major role in the total loss.Too large or too small milling media average size will make reflection loss peak of the absober smaller and closer to the low frequency,and when the thickness of the absorbing layer is 1 mm and the weight ratio large and small ball milling media is 1 : 2,the minimum reflection loss reaches-7.8 dB.