Research On Absorbing Performance Of Carbonyl Iron Modified By Multicomponent System

Carbonyl iron is magnetic loss type absorbing materials with a wide range of applications.It has the advantages of large magnetic loss angle,high saturation magnetization and curie temperature.But the complex permittivity of carbonyl iron is large,the spectrum characteristics and corrosion resistance are poor.It can not satisfy the strong loss of electromagnetic wave and high absorption characteristic on the specific frequency band.Therefore,In the light of the deficiencies in the microwave absorbing properties of carbonyl iron.The method of surface composite modification is usually adopted,to reduce the complex permittivity,increase complex permeability,to closely match the impedance of free space and the modified carbonyl iron.The purpose of attenuation of electromagnetic waves is to be achieved.This paper aims to prepare modified flake carbonyl iron absorbing material by multicomponent system doping.The microstructure,phase composition and electromagnetic parameters of the modified powder are analyzed.Reflection loss is calculated according to the theory of electromagnetic field transmission line.The main researches as follows:Three different stearate salts?calcium stearate,zinc stearate and sodium stearate?are used as one element doing system,prepared modified carbonyl iron absorbing materials by high energy ball milling.The variation regulation of the electromagnetic parameters and reflection loss for the modified samples with frequency had been studied.XRD results show that:three samples showed the diffraction peak of alpha-Fe phase after modification,and the width and height of the diffraction peak were no obvious change.The modification preparation samples by adding calcium stearate disperse more evenly,low complex permittivity and reflection loss.When the thickness of the coating is 1.5mm,the reflection loss is-7.73dB,the lowest in the same doping system.The absorption performance is better than others.Calcium stearate respectively with Co,SiO₂ and TiO₂ are used as the two elements doping system.The changes of electromagnetic parameters and reflection loss of the modified carbonyl iron sample.had been studied.The experimental results show that:the two elements system doping preparation of modified carbonyl iron samples have high degree of refinement and flake,superior magnetic permeability and preferable impedance matching performance.According to the map of X ray diffraction?XRD?,it can be clearly seen that the phase structure of the modified powders still exhibit the structure of alpha-Fe body center cubic.When the thickness of the material is 1.5 mm,adding calcium stearate and TiO₂ modified samples were prepared by doping two elements system of obtains minimum reflection loss,it can reach-7.92dB at 1.94GHz,and the effective absorption bandwidth?RL<-6dB?is 1.87GHz.It is suitable for thin thickness and wide-band radar wave absorber in low frequency band.The composite effect of three elements doping system for absorbing materials are researched.One is adopted calcium stearate,KH-560 respectively compound doping with Co,SiO₂ and TiO₂,the other is used calcium stearate and mixture of two metal powder.The experimental results show that:The particles morphology of the samples prepared by the two types of doping systems all showed a smooth and flat foliated structure,which increased the surface area of the absorbing electromagnetic waves to some extent.The two phase structure shown carbonyl iron always presents alpha-Fe body centered cubic structure,no other phases were generated in the material milling process.However,the samples prepared by the second doping method,According to the Bragg formula,which reduces the internal stress of the crystal lattice formed during ball milling,and makes the diffraction peak shift slightly to a low angle.From the reflection loss,the absorption peaks of the two types of doped systems are all located 2-4 GHz.Calcium stearate,KH-560 and TiO₂ compound doping system and SiO₂,TiO₂ and calcium stearate compound doping system obtain minimum reflection loss in the same system,-12.46 dB and-11.15 dB,respectively.The effective absorption bandwidth of lower than-10 dB was 1.02 GHz and 0.51 GHz,respectively.Contrast two ways,the three elements doping system with coupling agent has the lowest reflection loss extreme value and the best attenuation and loss electromagnetic wave performance when RL<-10dB.It can better achieve the wide frequency and high absorption requirements in the low frequency range.