| This graduation project studied the crystal structure and electromagnetic properties of flake FeSiAl magnetic powders obtained from different ball milling times,and prepared a wave-absorbing coating with ZrO2 as the substrate and flake FeSiAl magnetic powder as the absorber.The effects of milling time,FeSiAl magnetic powder content,and coating thickness on the electromagnetic and absorbing properties of flake FeSiAl magnetic powder are studied.SEM,XRD,and VSM were used to observe the morphology and crystal structure of the flake FeSiAl magnetic powder,as well as the saturation magnetization of the flake FeSiAl magnetic powder,and the complex permittivity and complex permeability of the flake FeSiAl magnetic powder were tested by a microwave network vector analyzer.And use MatLab analysis to calculate the reflectance.The experimental results show that:(1)The ball milling time will have a significant impact on the morphology and electromagnetic properties of the material.With the increase of the ball milling time,the FeSiAl powder exhibits an obvious flattening trend,and the average particle size of the powder is 66.77?m after the ball milling for 40 hours.The average particle size of the powder is 58.81 ?m when the ball is milled for 45 hours.In addition to the flake powder obtained after the ball milling for 45 hours,the granular powder appears due to the increase of the ball milling time;with the increase of ball milling time,the saturation magnetization of FeSiAl magnetic powder decreased from 96.24 emu/g in ball milling for 40 hours to 47.87 emu/g in ball milling for 45 hours.(2)In the frequency range of 1 GHz-6 GHz,the flake FeSiAl magnetic powders milled for 40h and ball milled for 45 hours are mixed with paraffin wax in different proportions to compress coaxial ring samples.Both powders have the lowest real part of complex permittivity and the real part of maximum complex permeability when the paraffin content is 30 wt%,and the minimum values of complex permittivity real part are 19.24 and 18.60,and the maximum values of the real part of the complex permeability are 3.32 and 3.48 respectively;at the same time,the paraffin content is 30 wt%and the simulated thickness is 4 mm;when the reflectivity of the two powders is the smallest,it is-12.75 dB at 1.6 GHz and-13.33 dB at 2.0 GHz respectively;with the increase of thickness,the reflection peaks of the two powders move towards the low frequency band,and the bandwidth gradually increases;when the thickness is 4mm,the sample reflectivity<-10 dB frequency band bandwidth is 1 GHz and 1.45 GHz.(3)Different proportions of CrNi powder are added to FeSiAl powder milled for 40 hours and 45 hours to prepare coaxial ring samples.The proportion of paraffin was 30 wt%,the mixed powder with 2 wt%CrNi powder had the lowest real part of complex permittivity and the real part of maximum complex permeability,the minimum value of real part of complex permittivity was 14.08 and 17.04,and the maximum value of real part of complex permeability was 4.81 and 4.95,the complex permittivity is significantly lower than that of the original powder,and the complex permeability is significantly higher than that of the original powder.At the same time,the reflectivity of the two powders is the smallest when the paraffin content is 30 wt%and the simulated thickness is 4mm,which are-14.19 dB at 1.85 GHz and at 1.85 GHz,-14.43 dB at 1.6 GHz;as the thickness increases,the reflection peaks of the two powders move toward the low frequency band,and the bandwidth gradually increases.When the thickness is 4mm,the sample reflectivity<-10dB band bandwidth is 1.1 GHz and 1.53 GHz respectively,compared with the original the powder bandwidth is significantly increased.(4)Add different proportions of TiB2 powder to the FeSiAl magnetic powder of ball milling for 40 hours and ball milling for 45 hours to prepare coaxial ring samples.The proportion of paraffin wax is 30 wt%,the mixed powder with 1 wt%TiB2 powder has the lowest real part of complex permittivity.The minimum values of the real part of the complex permittivity are 14.33 and 17.04,but the complex permeability is significantly lower than that of the original powder,the magnetic properties of the material is significantly reduced,and the complex permittivity is significantly lower than that of the original powder.The magnetic properties of the material decrease significantly,and the complex permittivity is significantly lower than that of the original powder,at the same time,the reflectivity of the two powders is the smallest when the paraffin content is 30 wt%and the simulated thickness is 4mm,which are-11.14 dB at 1.5 GHz and-11.6 dB at 1.7 GHz;with the increase of the thickness,the reflection peaks of the two powders move to the low frequency band,and the frequency bandwidth increases gradually.When the thickness is 4 mm,the bandwidth of reflectivity<-10 dB is 0.51 GHz and 0.85 GHz,respectively,which is significantly lower than that of the original powder.(5)The FeSiAl powder that has been ball-milled for 40 hours is prepared into absorbing coatings with different thicknesses by plasma spraying technology,the morphology of the coating was observed by SEM,and it was found that the FeSiAl powder became more flat after plasma spraying,the coating has the smallest reflectivity at a thickness of 1.5 mm,which is-11.73 dB at 4.5 GHz.Using a resistance furnace to heat a 1.5mm thick coating and measure the reflectance at different temperatures,it is found that the reflection peak gradually shifts to the high frequency region as the temperature rises,the peak value of the reflection peak decreases and the half-value width becomes larger.The band width of reflectivity<-10 dB can reach 0.89 GHz at 500?,when the temperature rise to Curie point,the magnetic loss and half peak width of reflectivity peak decrease sharply because FeSiAl becomes paramagnetic material. |
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