Crystallographic orientations of catalytic particles in filamentous carbon; Case of simple conical particles

Abstract Filamentous catalytic carbons in the form of simple tubes with conical metal particles at one end have been selectively prepared by CO disproportionation (2 CO → CO 2 + C) catalysed by iron-cobalt and iron-nickel alloys of various compositions and structures: 6 iron-cobalt alloys with the bcc structure, 1 fcc iron-cobalt and 4 fcc iron-nickel. The crystallographic relations between the metal particles and their carbon tubes have been determined by CTEM. In the case of all the metal composites prepared from alloys of bcc structure, the metal particle is a single crystal with a [100] axis parallel to the axis of the carbon tube, and the basal faces of the truncated cone, which appear free of carbon, are (100) faces. In the case of all the metal composites prepared from alloys of fcc structure (FeCo and FeNi), the metal particles are not always single crystals as they present sometimes (111) twin planes. However, there is always a [110] axis parallel to the axis of the carbon tube and the carbon-free basal planes of the cones are always (111) faces.