Effect Of High Pressure Treatment On The Microwave Absorbing Properties Of Ferrite

Absorbing materials has a very important practical value in civilian and military, the Ferrite-absorbing materials has the advantages of strong absorbability,matching impedance,good absorption frequency bandwidth,low cost,simple preparation,so it becomes the hot topic.In the design and synthesis of absorbing materials,people pay more attention to the chemical composition and methods of synthesis of substances, then made the good performance of ferrite.Althought using the extreme condition high pressure to design absorbing material has not been reported.This paper is dedicated to research high pressure treatment of absorbing properties,hope to prepare high-performance ferrite absorbing materials.The results show that: high-pressure could significantly improved the microwave electromagnetic parameters and enhanced its reflection loss,increased absorption bandwidth of ferrite, had been received satisfactory results.At the same time,also used Chemistry method -ceramic technique to make the ferrites,this two methods could be compared in certain basic.This paper provided a new ideas and research methods to research work of absorbing materials,and injected new vitality to ferrite absorbing materials for the further development.In this paper,it mainly obtained the conclusions as the following aspect:(1)Samples of M-type barium ferrites(BaM)were synthesized using the ceramic technique,phase identifications were performed by the X-ray power diffraction (XRD)the microstructure features were observed by scanning electron microscope (SEM),the results showed that:calcined inair at 1300℃for 3h,after the attrition,it obtained the uniformity ferrites.All samples were identified to be single phase with only M-type hexagonal barium ferrites,no other phases were detected.BaM particles are approximating hexagonal-shaped and the average grain size was about 1.4-3.2μm.(2)Carbon black,barium ferrite and the mixture of them were filled in the soft foamed polyurethane.The microwave absorption properties were measured by the arch reflection method from 4 to 8GHz using an HP 8320B vector network analyzer (VNA).The experiment indicated:filled with 5g ferrites and 15g carbon black plate has better absorbability,the reflectance approximately was-7dB.(3)Carried on 2GPa,4GPa,the 6GPa processing to Fe₃O₄,using the XRD and SEM, they had not appeared the new phase,but diffraction peak was widened,the particle size obviously had reducesd.(4)With the vector network analyzer to measure the electromagnetism parameter of the sample,the results showed that:high pressure can be good for adjusting microwave electromagnetic parameter,compared to normal pressure,effect of high pressure,μ′increased with increasing frequency,ε′decreased,it was propitious to realize the impedance matching;μ″andε″both increased,it was propitious to enhance energy attenuation.(5)The reflection loss of one-layer absorber was numerically calculated from 2 to 18GHz under 2mm thickness.The reflection loss were all decreased,peak value and bandwidth were both increased,especially when the pressure was 2GPa,the bandwidth could reached 7.5GHz for reflcting rate below-8dB,the biggest reflection loss was-24dB.All this proved that high pressure can be good for preparing ferrite absorbing material with properties of light,thin and width.