【作者】 王欢；

【导师】 王志江；

【作者基本信息】 哈尔滨工业大学 ， 化学工程， 2016， 硕士

【摘要】 SiC多孔材料是吸波/承载一体化的结构型吸波剂,并且具有轻质、宽频、强吸收的特点,在电磁波吸收领域尤其是高温吸波方面有着极大的研究价值和应用前景。作为结构型吸波剂,SiC多孔材料既要具有优异的吸波性能,还要具备良好的力学性能。本论文主要是对制备的SiC多孔材料的抗压和吸波性能进行评价和研究,为满足实际应用,SiC多孔材料的最大抗压强度要大于4MPa,并且高温条件下的最小反射损耗要低于-10dB。本论文首先制备出碳多孔骨架,再以其作为碳模板来与硅源反应,得到复制了碳多孔骨架孔结构的SiC多孔材料。通过对制备工艺的研究,确定了碳多孔骨架的炭化温度为800oC,此温度下碳多孔骨架的抗压性能和化学反应活性最佳;SiC多孔材料的制备则要选择按摩尔比1:1混合的SiO2和Si混合物作为外部硅源,1500oC烧结5h才能使硅源和碳源充分反应生成SiC,如果碳多孔骨架中含有内部硅源时,会使反应更加彻底。借助XRD、SEM、红外光谱和拉曼等测试手段对SiC多孔材料的成分、形貌和结构进行了表征,研究发现,SiC多孔材料可以复制碳多孔骨架的多孔结构特征,通过改变酵母量可以在5-150μm范围对其孔径大小和分布进行调节,并且Si C多孔材料的孔隙率可以达到70%左右。此外,在SiC多孔材料的开孔处和孔道内部有大量SiC纳米线生成,纳米线的存在可以提高材料的抗压强度,最后对SiC的生长机制进行了探讨。SiC多孔材料的抗压性能较碳多孔骨架有所提升,所制备的SiC多孔材料的最大抗压强度都在5MPa以上,其中抗压性能最佳的SiC多孔材料的最大抗压强度可以达到9.8MPa。TG曲线分析发现SiC多孔材料从室温到800oC范围具有非常好的稳定性,即使是含碳的SiC多孔材料在600oC以下也可以具有良好的稳定性,说明Si C多孔材料可以应用在高温环境中。在X波段从室温到700oC的吸波性能研究发现,SiC多孔材料的吸波性能随着温度的升高而增强,在700oC达到最佳,其最小反射损耗都在-12dB以下,当频率为11.8GHz时,更是具有-34dB的最小反射损耗。更多还原

【Abstract】 SiC porous materials are a kind of structural radar absorbing materials, which possess numerous merits, such as light weight,broad absorption band and efficient absorption ability. It has a great potential in microwave absorption field, especially in high temperature microwave absorption field. SiC porous materials should have excellent microwave absorption performance and mechanical properties when used as structural radar absorbing materials. In this paper, the microwave absorption properties and compressive properties of the fabricated SiC porous materials were investigated. In order to meet the requirement of practical application, the maximum compressive strength should be greater than 4MPa and the minimum reflection loss should be less than-10 dB.In our study, porous carbon materials were fabricated as a template, then the template of carbon was reacted with silicon source to obtain SiC porous materials. The best carbonizing temperature was 800 oC because the obtained carbon template had good compression resistance and reactivity ability. A well mixture powder of SiO2 and Si whose mole ratio being 1:1was used as silicon source. Afterwards, the carbon template and silicon source was sintered at the temperature of 1500 oC and maintained for 5h. If the porous carbon materials had internal silicon source, the reaction would be more complete. On account of detailed characterization on the component and microstructure of the final products by XRD, SEM, FIIR and Raman test, we found that the as-prepared SiC porous materials had similar porous structure with carbon template. The aperture could be controlled at the range of 5-150μm by changing the content of yeast and the porosity was about 70%. In addition, we found that a lot of SiC nanowires were formed in the open pores and porous channels of SiC porous materials. The SiC nanowires were beneficial to increase the compressive strength of SiC porous materials. Finally, the growth mechanism of SiC nanowires in SiC porous materials was also proposed.The compression resistance of SiC porous materials was better than the original carbon template, the maximum compression resistance could reach 9.8MPa. TG analysis demonstrated that SiC porous materials was stable when the temperature was elevated from 25 oC to 800 oC. The sample of SiC porous materials contained residual carbon was also stable at the temperature of 600 oC which demonstrated that SiC porous materials could be applied at high temperature condition. The microwave absorption of SiC porous materials was characterized in X-band at the temperature range of 25-700 oC. The microwave performance was promoted with the temperature increase and reached the best state in 700 oC. The reflection loss was under-12 d B and the minimum reflection loss was-34 dB at the frequency of 11.8GHz.更多还原