Preparation And Wave Absorbing Properties Of SiC Nanowires

Silicon carbide(Si C)nanomaterials used as wave absorbing materials have the characteristics of low density,high thermal conductivity,good mechanical properties,low thermal expansion coefficient and good chemical stability.It not only has an important position in the field of stealth fighters,but also has a wide range of civil applications.The application is very wide,and with the development of science and technology,there are higher requirements for it.However,the preparation of nanowire materials currently has certain bottlenecks in system research and nanowire morphology control.In this thesis,based on different preparation methods and different carbon sources,the raw material ratio,calcination temperature,calcination time,and the influence of sodium salt on the nanowires for the synthesis of silicon carbide nanowires are studied separately,and then the phase,structure and morphology are characterized.After that,the prepared samples with excellent nanowire morphology were tested for the wave absorbing performance.Firstly,the influence of different carbon sources on the growth of silicon carbide nanowires was studied.The sol-gel-carbothermal reduction method and the carbothermic reduction method were used to prepare silicon carbide nanowires,and the morphology and phase were characterized.The results showed that the silicon carbide nanowires prepared with sucrose as the carbon source have the best morphology when maintained at 1500 ℃ for 3 h.Apricot shell carbon is used as the carbon source,silicon dioxide is used as the silicon source,and the carbothermic reduction method is used to prepare silicon carbide.For nanowires,the best silicon carbide nanowires are prepared when the mass ratio is 2.5:1 and 4:1,and the calcination temperature is 1450 ℃ for 4h.When humic acid was used as a carbon source to prepare silicon carbide nanowires,there is almost no nanowire generation,and the use of coal gangue as a silicon source to prepare nanowires has also been studied,and the generation of silicon carbide nanowires is also very small.Secondly,silicon carbide nanowires were prepared by using glucose as the carbon source and silica sol as the silicon source.On this basis,1%,2% and 3% sodium fluoride and sodium chloride were added to prepare silicon carbide nanowires.The results showed that the nanowires prepared with glucose as the carbon source have better morphology after reacting at 1500 ℃ for 3 h,and the addition of 3% sodium fluoride and 2% sodium chloride has the best effect on the nanowires.Finally,the dielectric and wave absorbing properties of silicon carbide nanowires are studied.The wave absorption of silicon carbide nanowires prepared is-9.78 d B when sucrose is used as the carbon source and kept at 1500 ℃ for 3 h.Apricot shell carbon is used as a carbon source.When the mass ratio is 2.5:1 and the calcination temperature is 1450 ℃ for 4 h,the Si C nanowires have a wave absorption of-58.42 d B and an absorption bandwidth of 4.0 GHz at a frequency of 8.9 GHz and a thickness of3.02 mm.The nanowire prepared with glucose as a carbon source has a wave absorption of-42.81 d B.Silicon carbide nanowires prepared by adding 3% sodium fluoride and 2%sodium chloride were tested for wave absorbing performance.The results showed that the addition of two additives made the thickness of the material at the maximum reflection loss value thinner,and 2% sodium chloride was added.The prepared nanowire has the best wave absorption performance,with a wave absorption of-53.30 dB.