Study On Sputtering Carbon/Titanium Dioxide On The Surface Of Iron-based Amorphous Powder And Its Microwave Absorption Properties

In recent years,with the wide application of electronic equipment and radar,the study of microwave absorption in low frequency bands has been paid more and more attention.Microwave absorbing materials should have strong absorption and attenuation capabilities while being thin and lightweight.In various electromagnetic absorption materials,the electron scattering of iron-based amorphous disordered atoms makes the magnetic amorphous phase have a high resistivity,reduces the skin effect at high frequencies,and effectively promotes the penetration of microwaves.to get attention.However,the iron-based amorphous loss mechanism is single,the microwave reflection loss is limited,the low-frequency absorption bandwidth is narrow,and the impedance matching is poor,which greatly hinders the practical application.Therefore,this thesis is devoted to studying the combination of iron-based amorphous magnetic powder materials and carbon and titania dielectric materials to form composite materials,and using the synergistic effect between the materials to improve the microwave absorption performance of iron-based amorphous powders.The specific research contents are as follows:(1)Fe-based amorphous powders were prepared by ball milling,and carbon was deposited on the surface of Fe-based amorphous powders with different particle sizes by magnetron sputtering,and C/Fe-based amorphous composites were obtained.It is found that the particle size of the iron-based amorphous powders screened by the sieve is about 28-34?m,22-30?m and 15-25?m,respectively.With the decrease of the particle size,the iron-based amorphous powder gradually becomes irregular flake.The results of simulated reflectivity show that the particle size of 22-30?m has the best microwave absorption performance,and the minimum loss value is-14.6 d B at 3.5 mm and 3.8 GHz.After sputter deposition of carbon,the dielectric constant of the composites increases with the decrease of particle size,which is related to the increase of interface polarization and conductivity loss.The minimum RL value of Fe-based amorphous powder with particle size in the range of 22-30?m is-26.5 d B at 1.8 GHz when the thickness is 3.5 mm.It is also found that the interfacial polarization of the iron-based amorphous powders with particle size in the range of 22-30?m increases after different time of carbon deposition.The composite sample with the sputtering time of 2h has the smallest loss value and the largest effective bandwidth,and the minimum loss value is-26.5 d B at 1.5 GHz.(2)Fe-based amorphous powders with particle size of 22-30?m were used to prepare amorphous TiO₂by magnetron sputtering.After oxidation at 400?,TiO₂was transformed from amorphous to anatase.With the increase of sputtering time,the real and imaginary parts of the complex permittivity of the TiO₂/Fe-based amorphous composite decrease first and then increase.By comparing the simulated reflectivity,in the low frequency region,the composite sample with a sputtering time of 2.5 h shows the minimum RL value of-35.5 d B,and the effective bandwidth is 0.9 GHz;When the thickness is 3 mm,there is a maximum effective bandwidth of 1.8 GHz(2.9-4.7).For the oxidized TiO₂/Fe-based amorphous powder composites,the real part and the imaginary part of the complex dielectric constant show the same trend with the increase of sputtering time.When the thickness is 3.5 mm,the minimum loss value is below-30 d B;when the sputtering time is 2.5 h,the minimum RL value is-39.3 d B,and the effective bandwidth is 0.8 GHz;when the thickness is 2.5 mm,the maximum effective bandwidth is 1.4 GHz,and the effective bandwidth increases by 0.5GHz compared with that before oxidation.(3)C/TiO₂/Fe-based amorphous and TiO₂/C/Fe-based amorphous powder composites were prepared by magnetron sputtering twice.It is found that with the increase of sputtering time,the dielectric constant of C/TiO₂/Fe-based amorphous composite increases,and the dielectric loss capability of the composite is significantly enhanced in the range of 0-11GHz,and the dielectric loss capability also increases first and then decreases,while the value of??decreases slightly in the low frequency band.When the thickness of the composite is 2.5 mm,the minimum RL value is-37.2 d B,and the effective bandwidth is 2.1GHz when the thickness is 2 mm.By sputter a layer of TiO₂on that surface of the C/iron-based amorphous pow composite material and oxidizing,the real part and the imaginary part of the dielectric constant are obviously reduced,the change of the real part of the magnetic permeability is very small,and the imaginary part is slightly improved in a low frequency band.With the extension of sputtering time,the values of??and??gradually decrease and then increase,and the dielectric loss capacity decreases significantly in the range of 0-11 GHz;while the magnetic permeability basically does not change with the extension of sputtering time.The composite material with a sputtering time of 2 h has a good reflection loss,and the minimum loss value is-42.8 d B at a thickness of 2 mm.The composite material with a sputtering time of 3h has a maximum effective bandwidth of 3.2GHz at a thickness of 2 mm.