BCN Ternary Ceramic Design And Preparation And Research On Its Absorbing Properties

Electromagnetic pollution is an invisible pollution that has become a public concern that people are eagerly concerned about.The impact on human society has attracted the attention of countries all over the world and is listed as one of the environmental protection projects.Therefore,the wave absorbing material is of great significance to the civil and military fields,but the traditional wave absorbing material is difficult to meet the "thin,light,wide,strong" characteristics of a good wave absorbing material.Therefore,the preparation of new wave-absorbing materials is imperative.The boron carbonitride(BCN)material is considered to be a promising type of electromagnetic wave absorbing material that can be applied to critical Mach number aircraft because of its excellent thermal,chemical stability and flexibly adjustable dielectric properties.This paper first uses the CASTEP module of Materials studio to simulate the molecular structure of the BCN material with some possible element ratios.The study found that the real and imaginary parts of the dielectric constant of the BCN material decrease as the proportion of B and N elements increases.Then we used experiments to verify.By polymerizing monomers,a solid BCN precursor was prepared by passing boron trichloride gas into the mixed solution of boron trichloride,cyclohexane and ethylenediamine,in order to recover its possible polymerization process.High temperature cracking was performed in a tube furnace to change the heat treatment temperature,and the effects of precursor reactant ratio,heating rate,and maximum heating temperature on the microstructure,composition,and electromagnetic wave absorption properties of BCN materials were studied.We found that with the increase of the maximum heating temperature,nitrogen element gradually detaches from the BCN system or forms a more stable BN/C structure.If the molar ratio of cyclohexylamine: ethylenediamine is 2: 1,the maximum heating temperature is 1000 ?,and the heating rate is 5 ?/min,the BCN material will have the best wave absorption performance when the above three conditions are met at the same time.Under this situation,the effective bandwidth is 13.93 GHz(4.07-18GHz),the thickness corresponds to 2 to 6.0 mm;when the thickness is 3 mm,the lowest reflection loss value on-60.36 d B would reach 9.76 GHz,and the effective bandwidth at this time reaches 3.52 GHz.Also,the induction heating furnace was used to prepare the BCN material.The infrared heating gun measured the maximum heating temperature of about 1000 ?,and the heating time was 120 s.Compared with the BCN material obtained by heating in a tube furnace,the wave absorption performance is poor,which can achieve a minimum reflection loss of-20.81 d B at a frequency of 6.48 GHz and a thickness of 5.5 mm,and a maximum absorption bandwidth of 5.5 GHz(RL value <-10 d B).At the same time,the relationship between the element content of the prepared BCN material and the real part(?')and imaginary part(?'')of the complex dielectric constant is in good agreement with the results obtained by the first-principles calculation.