Fundamental Aspects of Catalytic Carbon Formation

这是对催化剂颗粒上和催化剂颗粒内发生的化学作用的研究，这种化学作用导致碳丝以不同的构象生长。细丝可以形成三种基本构象：晶须状、分支和多向。具体问题包括催化剂颗粒的结晶学特征对碳氢化合物分解反应机理的影响；反应条件如何影响特定催化剂碳氢体系产生的碳丝的结构特征；以及在催化剂中引入第二种金属对碳扩散路径的影响。综合运用控制气氛电子显微镜(CAEM)、原位电子衍射高分辨电子显微镜(HRTEM)、特殊的原位表面光谱、~(13)C核磁共振和块体动力学研究等技术对这些方面进行了研究。通过催化分解碳氢化合物在初级纤维表面生长碳丝的概念为生产具有独特物理、化学和电子性能的新一代复合材料提供了可能性。碳丝是通过碳氢化合物在小金属颗粒上的催化分解而产生的。铁、钴或镍促进了这一过程。这些细丝具有双重结构--一层围绕核心的石墨化皮肤，更容易被氧化。

This is an investigation of the chemistry occurring on and within catalyst particles that causes carbon filaments to grow in various conformations. Filaments can be formed in three basic conformations: whisker-like, branched, and multidirectional. Specific issues include the effects of the crystallographic features of the catalyst particle on the mechanism of the hydrocarbon decomposition reaction; how reaction conditions influence the structural characteristics of carbon filaments produced from a given catalyst hydrocarbon system; and the effects that the introduction of a second metal into the catalyst has on carbon diffusion pathways. A combination of techniques are used to study these aspects including controlled-atmosphere electron microscopy (CAEM), high-resolution transmission electron microscopy (HRTEM) with in-situ electron diffraction, specialized in-situ surface spectroscopy, carbon-13 nuclear magnetic resonance, and bulk kinetic studies. The notion of growing carbon filaments onto the surfaces of primary fibers by catalytic decomposition of a hydrocarbon offers the potential of producing a new generation of composites with unique physical, chemical, and electronic properties. Carbon filaments are produced by the catalytic decomposition of hydrocarbons on small metal particles. Iron, cobalt, or nickel promote this process. The filaments have a duplex structure - a graphitic skin surrounding a core that is more easily oxidized.