Research On The Preparation And Modification Of Fe-based Amorphous Powders

With the widening of the application scope of electromagnetic waves,the development and application of microwave absorbing materials have attracted more and more attention.To meet the characteristics of "thin,light,wide,strong"characteristics of electromagnetic wave absorption materials is not only conducive to reducing the radiation damage caused by electromagnetic waves to the human body,but also to improve the stealth characteristics of weapons and equipment in the military field.Fe-based amorphous alloys have become anew type of electromagnetic absorbing materials because of their excellent soft magnetic properties and low price.However,the impedance matching characteristics of pure Fe-based amorphous powders is unbalanced when used for absorbing waves,and the excellent absorption characteristics of electromagnetic waves cannot be shown.In this paper,Fe-based amorphous powders are modified by three ways to improve their impedance matching characteristics as well as improve their microwave absorbing properties.The influence of dispersant addition on the electromagnetic properties of composites was explored through graphite doping modification.By controlling the particle size of the mixed Fe-based amorphous powders,the absorption peak and absorption bandwidth of the composites are effectively improved.When the size of amorphous powder is 300mesh,the coating with thickness of 3.0mm has a peak absorption value of-17.8dB at 12.04 GHz,and the effective bandwidth is 3.1 GHz.In addition,by adding different amounts of graphite,the optimum proportion of graphite addition was determined,and the absorption frequency shifted to low frequency.Through the modification of high energy ball milling,the maximum absorption peaks of-24.9dB and-23dB were obtained at the 9.4 GHz and 9.2 GHz after milling forl5h and 25h.When the ball milling time is up to 35h,the material absorbing performance is excellent,the bandwidth of the reflection loss value below-20dB is in the range of 10.8-12.8GHz,the frequency range reaches 2 GHz,and the minimum reflection loss value at 11.6GHz is-27.3dB.The optimum technological parameters were determined in the process of SiO2 coating modification.For the single coating process,the best process parameters are reaction temperature at 40?,reaction time with 6h,alcohol water ratio in 8:1,ammonia water with 2ml and TEOS with 2ml.When the coating thickness of the coating is 2.0mm,the effective frequency bandwidth(<-l0dB)reaches 4.4GHz wider than that of the coating with the thickness of 2.0mm before coating,and the effective band width of the coating is increased by 25%.The characteristics of the electromagnetic parameters are improved by the SiO2 coating.The high dielectric constant is suppressed,the eddy effect is reduced and the permeability of the material is increased,and the absorbing property of the amorphous material can be improved effectively.