Preparation And Microwave Absorbing Properties Of Mo₂C Nanocomposites

In recent years,transition metal carbides have been widely used in the fields of catalysis,energy and devices due to their characteristics of"interstitial alloy",which have high melting point,good hardness,excellent thermal stability and outstanding corrosion resistance.Considering the preeminent conductivity of Mo₂C,this paper would firstly explore its microwave absorbing properties.But single Mo₂C shows poor performance in electromagnetic attenuation and impedance matching.In view of these facts,compositoin regulation and morphological control would be adopted in this paper.And the main contents of research and results are as follows:?1?Firstly,in order to explore the microwave absorption performance of Mo₂C,this chapter prepared Mo₂C nanoparticles via simple hydrothermal reaction and carbon-thermal reduction.And we found that they were suitable to be microwave abosrbing materials with conductivity loss and relaxation characteristics.The reflection loss of Mo₂C nanoparticles could reach-40.07 dB at 2.45 mm.However,the effective bandwidth was not only narrow but also concentrated at high frequency,because of the single loss mechanism of Mo₂C nanoparticles.?2?Then,to solve the problem that bandwidths focused on high frequency,this chapter aimed at improving the graphitization degree of samples and enriching attenuation mechanisms.Therefore,porous Mo₂C@C nanocomposites were prepared in this chapter through synergistic effects of MOFs and POMs.The results showed that porous Mo₂C@C nanocomposites not only owned the characteristics of light weight and strong attenuation,such as RL peak value of-49.19 dB at 2.60 mm,but also the shift of absorbing bands?2.48 GHz?to low frequency.However,their effective bandwidths were still restricted by limited attenuation meahcnisms,including conduction loss and polarization loss.?3?Finally,to obtain microwave absorbent with high-efficiency and broad-bands features,one-dimensional porous Mo₂C/Co@C nanorods were synthesized on basis of excellent microwave asorbing properties for porous Mo₂C@C nanocomposites.The truth is that one-dimensional morphology can effectively decrease the density of nanocomposites and decrease value of percolation.In addition,due to exsitence of Co particles,the samples possessed multiple loss mechanisms?dielectric loss and magnetic loss?and polarization ability?interfacial polarization and dipole polarization?,which greatly enhanced the microwave absorption performance.It is worth mentioning that the effective bandwidth?RL<-10 dB?could reach 6 GHz.Generally speaking,this paper researches the microwave absorbing features of Mo₂C nanocomposites based on well regulation of composition and structure.It is successful to obtain the excellent absorbers with strong absorbing possibility,wide bandwidth and low density.Moreover,the relationship between micro structure and multiple polarization as well as loss forms has been deeply studied.This paper provides a sufficient reference for further application about transition metal carbides-based microwave absorbers.