Preparation And Properties Of Doped SiC Microwave Absorber By Arc Method

In this paper,Al-doped SiC nanopowders,B-doped SiC nanopowders andB?N-co doped SiC nanopowders were synthesized by plasma direct-current(DC)arc method.The phase,morphology and surface composition of the samples were analyzed by X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy.At the same time,the microwave absorption properties of the samples were tested by vector network analyzer,and the influence of doping amount on the microwave absorption properties of SiC and its related mechanism were discussed.Firstly,Al-doped SiC nanopowders were prepared by DC arc method.The morphology of the samples showed irregular particles and some nanosheets.By changing the doping amount of Al,the microwave absorbing properties of SiC nanopowders are improved effectively.The results show that when the doping amount is 5at%,the performance of Al-doped SiC nanopowders is the best,the reflection loss is-43.761 dB at 6.9GHz,and the corresponding thickness is 3mm.When the thickness range is 1.2-5.5mm,the frequency range of reflection loss below-10 dB is 3.2-18 GHz.In the thickness range of 1.22-5.5mm,the reflection loss of Al-doped SiC nanopowders is about 1.1-6 times that of SiC nanopowders.Moreover,the samples with different thickness have different reflection loss peak and bandwidth,and move to low frequency with the increase of sample thickness.Secondly,B-doped SiC nanopowders were prepared by DC arc method.The morphology of the samples is also irregular particles and some nano flakes.The results show that the absorbing properties of B-doped SiC nanopowders are the best when the content of B is 10at%.When the thickness of absorption layer is 2.9mm and the frequency is 6.79 GHz,the best reflection loss is-51.69 dB.Moreover,in the frequency range of 2.9-18 GHz,the reflection loss of the sample is less than-10 dB,and the corresponding thickness is 1.1-5.5mm.When the frequency range is 3.2-7.9GHz,the reflection loss of the sample is less than-20 dB,and the corresponding thickness range is 2.5-5.5mm.Finally,B?N-co doped SiC nanopowders were prepared by DC arc method.The samples have multi-level nanosheet structure.The results show that with the increase of acetonitrile content,the microwave absorbing properties of B?N-co doped SiC nanopowders first increase and then decrease.When the content of acetonitrile is 5ml,the absorbing property of B?N-co doped SiC nanopowders is the best.When the thickness of absorption layer is 4.07 mm and the frequency is 5.08 GHz,the reflection loss is-44.59 dB.The frequency range of reflection loss below-10 dB is 3.09-18 GHz,and the corresponding thickness range is 1.32-5.5mm.The results show that Al,B single doping andB ? N-co doping can significantly improve the microwave absorbing properties of SiC nanopowders.Doping can make SiC nanopowders produce more defects,and then produce "electron / hole polarization center" to enhance the dielectric response and improve the dielectric properties of SiC powder.At the same time,the defects and vacancies lead to the spin polarization and local magnetic moment of SiC.The interaction between local magnetic moments leads to ferromagnetic order,which makes the samples show weak magnetism.In conclusion,Al-doped SiC nanopowders,B-doped SiC nanopowders andB?N-co doped SiC nanopowders have simple preparation process and excellent microwave absorbing properties,which have broad application prospects in the field of electromagnetic wave absorption.