Fundamental Aspects of Catalytic Carbon Formation

这是一项化学研究，发生在催化剂颗粒上和内部，导致碳丝以各种构象生长。细丝可以形成三种基本形态：须状、分枝状和多向状。具体问题包括催化剂颗粒的结晶学特征对烃分解反应机理的影响；反应条件对给定催化剂烃类体系生成的碳丝结构特性的影响以及在催化剂中引入第二种金属对碳扩散途径的影响。研究这些方面的技术组合包括可控气氛电子显微镜（CAEM），高分辨率透射电子显微镜（HRTEM）与原位电子衍射，专门的原位表面光谱学，碳-13核磁共振，体动力学研究。通过碳氢化合物的催化分解在原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潜力。碳丝是由碳氢化合物在小金属颗粒上催化分解而产生的。铁、钴或镍促进这一过程。这种细丝具有双重结构——石墨皮包裹着更容易被氧化的芯。

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.