Performance Of Zirconium Diboride-Based Composites For Microwave Absorption Property

The rapid development of electronic and communication technology has brought convenience to humans while also bringing electromagnetic pollution.Microwave absorbers are a key means to solve electromagnetic pollution and enhance the stealth ability of military targets.Therefore,the development of a"thin,light,wide,strong,high temperature resistant"microwave absorber has become a research hotspot at the moment.Thus,ZrB₂-based composite structure as a new type of high-performance microwave absorbers are synthesized in the paper and a cheap but efficient synthesis method is also achieved.Moreover,the microstructure and microwave absorption properties of ZrB₂ and ZrB₂-based composite structures are also studied.Firstly,in this paper,the structure and morphology of ZrB₂ are characterized via multiple characterization methods,and further the microwave absorption property is studied.It shows that ZrB₂ has a high dielectric constant?32.3¹44.2?and dielectric loss tangent,due to the existence of electrical conduction loss and dielectric loss,it has excellent dielectric loss capability.However,its impedance matching characteristics are poor,which limited its practical application.Secondly,in order to improve the microwave absorption performance,ZrB₂@C composite structure is prepared by catalytic chemical vapor deposition?CCVD?method,and then ZrB₂-ZrN_0.4B_0.6-C composite structure is synthesized by chemical vapor infiltration?CVI?process,and the microstructure,chemical composition and electromagnetic properties of the materials are studied systematically.Studies have shown that after coating a layer of carbon on the surface of ZrB₂,the dielectric constant of the material is significantly reduced?6.7²2.2?,which is beneficial to improve the impedance matching characteristics,thereby improving its microwave absorption performance.For the ZrB₂@C composite structure,the minimum reflection loss value RL_min is as high as-38.7 dB at 5.9 GHz.In addition,the effective absorption bandwidth can reach 9.2 GHz from 3.8-13.0 GHz in the range of 2.0-4.5 mm thick.Further,in case of ZrB₂-ZrN_0.4B_0.6-C composite structure,at a thickness of 4.0 mm,RL_min is-37.2 dB at6.2 GHz and the effective absorption bandwidth is 2.0 GHz.Finally,the ZrN_0.4B_0.6-SiC composite structures are synthesized by CVI method used the ZrB₂@C composite structure as the precursor.The structure,morphology,conductivity,thermal stability and electromagnetic properties of the composite are characterized.Studies have shown that when the temperature of the synthetic precursor ZrB₂@C composite structure is 650°C for 30 min,the microwave absorption properties of the obtained sample?ZS-3 composite structure?are significantly improved than that of ZrB₂.For the ZS-3 composite structure,the effective absorption bandwidth of less than-10 dB is 11.8 GHz from 0.5 to 5.0 mm when the filling loading is 80 wt%.In particular,when the thickness is 3.05 mm,RL_min is achieved as high as-50.8 dB at 7.7GHz with the bandwidth of 2.8 GHz from 6.5 to 9.3 GHz.It has been found that adjusting the CCVD process is helpful to control the thickness,content,crystallinity,etc.of the carbon layer,and then adjust the content of ZrN_0.4B_0.6 and SiC in the composite to reduce the electrical conductivity of the composite structure appropriately,which is beneficial to make sure the dielectric constant of the material be close to or even equal to the magnetic permeability,thereby improving the electromagnetic properties of the material.