Preparation And Electromagnetic Behavior Of TiN Based Materials For Lightweight And High Efficiency Microwave Absorption

In recent years,with the applications expansion of microwave absorbing material,researches on improving the loss performance and broadening of the effective loss frequency band have become increasingly active at home and abroad.In addition,developing new absorbers with thin thickness,light weight,wide bandwidth and strong-absorption is urgently needed.However,the traditional absorbers materials such as ferrites,magnetic metal particles and their oxides are difficult to meet the requirements of light weight and high efficiency due to their high density,large filler content and poor environmental stability.At present,some new types of microwave absorbing materials with unique electromagnetic mechanisms provide us more choices and ideas for designing and studying microwave absorbing materials.Our previous studies indicate that titanium nitride(TiN)nanoparticle is a potential lightweight absorber,due to its low density and excellent microwave absorbing properties.Nevertheless,the ease of agglomeration and single microwave absorbing mechanism of TiN result in the large amount of filler content(45 wt%),and it is difficult to meet the demands of light-weight and high-efficiency.Therefore,improving the dispersion and introduces new absorbing mechanisms are the keys to prepare TiN-based lightweight and efficient waveabsorbing materials.Based on the above discussion,TiN nanofibers,TiN/C nanofibers and TiN/ reduced graphene oxide(RGO)two-dimensional sheet composites were prepared by means of electrospinning and/or hydrothermal reduction in the present studies,and their electromagnetic wave absorption performance and electromagnetic wave dissipation mechanism were systematically investigated.The main research content is as follows:1.Preparation and Electromagnetic Properties of TiN NanofibersWith titanium dioxide nanotubes(NTA,laboratory prepared)and tetrabutyl titanate(TBT,commercially available)as precursors,two types of TiN nanofibers were prepared under the similar conditions using electrospinning-assisted high-temperature thermal nitridation.On the one hand,the effective assembly of TiN nanoparticles in nanofibers improves the dispersivity and gives the material more opportunities for interacting with electromagnetic waves.On the other hand,the formation of the conduction net ascribed to the physical contact of fibers will eventually lead to the multiple internal reflection,which is expected to endow the TiN nanofibers superior electromagnetic wave absorption performance at lower filler content.The results show that the type of precursor has little influence on the electromagnetic properties of TiN fibers.For 14.5 wt% loading,the reflection losses of the two types of TiN fiber can reach-47 dB and-45 dB respectively,which indicates that the types of precursor has little influence on the electromagnetic properties of TiN fibers.Obviously,in comparison with TiN nanoparticles,TiN nanofiber can greatly reduce the filler content in the matrix and improve the electromagnetic wave absorption performance,suggesting that it has potential as a lightweight wave-absorbing material with high efficiency.2.Preparation and Electromagnetic Properties of TiN/C Composite FibersOn the basis of above studies,to further improve the dispersion properties of TiN nanoparticles and introduce more electromagnetic wave dissipation mechanisms,a series of composite nanofibers with different TiN/C ratios were in-situ prepared with tetrabutyl titanate as the titanium source,and polyvinyl pyrrolidone(PVP)as the carbon source.Then the influence of the ratio of TiN to C on the electromagnetic properties of TiN/C was investigated.The results show that the dielectric properties and microwave absorbing properties of the composites gradually increase with increasing the proportion of TiN in the TiN/C composite nanofibers.The optimum electromagnetic wave absorption performance of TiN/C was achieved when the mass ratio of TBT to PVP was 2:1.With S2 as filler,the electromagnetic wave absorption performance of the composites loading with 5 wt%,10 wt%,15 wt%,20 wt%,25 wt% were investigated in detail.The results showed that the best microwave absorption performance was obtained with the filler content is 15wt%.The maximum reflection loss can reach-41.85 dB with a thin thickness of 1.9 mm.Moreover,the effective absorption covers the whole test frequency range.In contrast to pure TiN fiber,TiN/C composite fiber show several advantages such as the synergistic combination of multiple losses mechanism,wide bandwidth and flexibility.3.Preparation and Electromagnetic Properties of TiN/RGO CompositesAs a new type of two-dimensional structure material,graphene has high specific surface which is favorable for the interactions between electromagnetic wave and materials interface.In order to further improve the dispersibility of TiN nanoparticles and give the material more interaction with electromagnetic waves,based on the above studies,a series of two dimensional TiN/RGO composites with different ratios were in-suit prepared by simple hydrothermal method and thermal nitriding treatment.The results show that the effective dispersion of TiN nanoparticles can be achieved by means of the lamellar structure of graphene.The electromagnetic wave absorption performance of TiN/RGO composites with various ratio were evaluated at the fixed filler loading of 2 wt%.The results show that the eddy current gradually dominates the loss of electromagnetic wave as the proportion of RGO in the composite material increases.In particular,the high absorption capacity of TiN/RGO at ultra-low filler content can be successfully achieved,as not only the minimum reflection loss value can reach-42.8 dB,but also effective absorption bandwidth of 4.32 GHz was reached.