【作者】 徐海涛；

【导师】 陈丽娟；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 物理化学， 2009， 博士

【摘要】 微米螺旋碳纤维(CMC)不仅具有普通碳纤维的高强度、低密度、耐高温、化学性质稳定等优点,而且其独特的螺线管大空腔的结构,有望用作新型雷达吸波材料。本论文采用多种方法对微米螺旋碳纤维材料进行了磁性修饰,并深入研究了其电磁吸波性能。论文中另一部分工作围绕形貌不同于微米螺旋碳纤维的新型弹簧状微纳米螺旋碳纤维的制备、结构及性能进行了系统的研究,并对其生成机理进行了初步的探讨。主要内容如下:1.论文首先对相关领域的研究工作进行总结。基于电磁基本方程、电磁参数以及电磁波平面阻抗匹配理论,在综述螺旋碳纤维、铁氧体、铁碳复合材料研究现状的基础上,提出本论文的研究内容及要解决的主要科学问题。2.采用化学气相沉积法,合成了规则的弹簧状微纳米螺旋碳纤维。系统研究了催化剂种类、助剂噻吩的用量、反应温度、反应气组成及流量等各种实验条件对产物结构的影响;在此基础上,优化了实验条件并得到形貌均一的微纳米螺旋碳纤维。基于气-液-固-固生长机理,论文从实验上对螺旋碳纤维形成进行了研究,结果表明弹簧状微纳米螺旋碳纤维与CMC具有相同的生成机理。3.选用共沉淀、高聚物保护液相合成方法和溶胶凝-胶法制备了多种形貌的铁氧体,首次用所合成的多种形貌的纳米级铁氧体和铁颗粒对活化后的微米螺旋碳纤维进行了修饰和填充,并用优化了的修饰方法和填充工艺,得到了电磁性能兼备的纳米铁氧体和纳米铁颗粒填充的螺旋碳纤维复合材料,并对其性能进行了详细研究。4.利用反胶束法制备的明胶包覆草酸亚铁颗粒作为前躯体,通过高温下氢气还原,制备了核壳式碳包铁复合微球,对其性能研究表明,这是一种具有优良电磁性能的复合材料。5.论文首次针对微米螺旋碳纤维的粒径和样品的添加比例对复合结构的电磁参数和吸波性能的影响进行了系统研究,模拟了相关添加比例的反射率曲线,为螺旋碳纤维作为雷达吸波材料的应用提供了有价值的参考数据。更多还原

【Abstract】 Due to the excellent physical and chemical properties, as well as the novel structure, the carbon micro-coils (CMC) have the promise of being used as an efficacious material for radar absorption. In this dissertation, the spring-like carbon fibers having distinct morphologies from the carbon micro-coils were successfully synthesized. Furthermore, the as-synthesized CMC were modified with nanometer ferrite and ferric grain. The electromagnetic properties of this new kind of composite material were investigated in detail.At first, the relevant researches about the helical carbon fibers were summarized. From the basic electromagnetic equations, electromagnetic parameters, and electromagnetic wave impedance matching theory to the spiral of carbon fiber, ferrite and iron-carbon composite materials, the contents of their research were reviewed in this paper, respectively.Secondly, the regular spring-like carbon fibers were fabricated by a catalytic pyrolysis method with acetylene as a carbon resource, Fe as a catalyst and thiophene as a promoter. The dependence of the products’structures on the preparation conditions, including the catalyst, additive thiophene, reaction temperature as well as gas composition and flow rate, etc. was explored. By optimizing experimental parameters, the uniform spring-like carbon fibers were obtained. It was demonstrated that the growth of the spring-like carbon fibers might be attributed to the process of gas-liquid-solid-solid, similar to the growth mechanism of CMC.The nano-sized ferrites and ferric particles with various morphologies were prepared by co-precipitation and liquid synthesis with polymer protection. The as-prepared nanoparticles were employed to fill and modify the CMCs through an optimized process. The electromagnetic properties of the synthesized iron-carbon composites were studied. It is indicated that the present composites own excellent electric as well as magnetic properties, and were expected to achieve better impedance matching.The gelatin-coated ferrous oxalate particles were fabricated as precursors by reverse micelles method. The precursors were subsequently reduced by hydrogen at a high temperature. As a result, the carbon-coated iron core-shell composite microspheres were obtained. The electromagnetic properties of the core-shell structure were characterized.It was found that the electromagnetic properties of the CMCs were strongly depended on the size of the CMC grain as well as th ratio of the CMC to matrices. These data could be utilized to design the coat for radar absorption in the further.更多还原