Ph. Serp

Carbon nanotubes produced by fluidized bed catalytic CVD: first approach of the process

Abstract Multi-walled carbon nanotubes have been produced with high yield on an iron supported catalyst by catalytic chemical vapor deposition in a fluidized bed reactor. The choice of such a technique allows to reach high selectivity towards the desired material. A remarkable feature of this process is the huge bed expansion observed during the nanotubes growth that affects the fluidization regime due to the evolution of the apparent density of the composite powder. The catalytic powder, the composite material and the purified nanotubes have been analyzed by SEM, TEM and BET nitrogen adsorption.

Surface treatments of vapor-grown carbon fibers produced on a substrate - Part II: Atomic force microscopy

Vapor-grown carbon fibers (VGCF) were produced from a methane-hydrogen mixture on a substrate seeded with an iron catalyst. The fibers thus produced were submitted to different oxidative treatments: nitric acid, oxygen plasma and partial gasification with air or carbon dioxide. These fibers have been previously characterised by X-ray diffraction, SEM, nitrogen adsorption, XPS and ToF-SIMS. In the present paper we report on the examination of their surface nano-topography by atomic force microscopy (AFM)

Production of vapour-grown carbon fibres: Influence of the catalyst precursor and operating conditions

Vapour-grown carbon fibres (VGCF) were produced from a methane–hydrogen mixture on a substrate seeded with an iron catalyst. The influence of the operating conditions and of the nature of the catalyst precursor on the yield and properties of the VGCF produced was investigated. The presence of hydrocarbon during the catalyst reduction stage and the heating rate imposed during the fibre growth step were found to be the most important factors determining the yield of VGCF, while Fe3(CO)12 proved to be an excellent precursor, producing the longest fibres.

The effect of morphology on the properties of vapour-grown carbon fibres

In the present work, mechanical properties of a batch of VGCF with various morphologies have been studied.

Optimizing Growth Conditions for Carbon Filaments and Vapor-Grown Carbon Fibers

The production, properties and applications of vapor-grown carbon fibers (VGCF) and carbon filaments were reviewed in the course of a previous NATO ASI [1].

Gasification and Surface Modification of Vapor-Grown Carbon Fibers

Vapor-grown carbon fibers (VGCF) were produced from a methane-hydrogen mixture on a reconstituted graphite support using the [Fe3(CO)12] complex as catalyst precursor. The fibers thus produced were submitted to different oxidative treatments: nitric acid, oxygen plasma and partial gasification with air or carbon dioxide. The original and the oxidised fibers were characterised by X-ray diffraction, SEM, AFM, nitrogen adsorption, XPS and ToF-SIMS. The use of nitric acid or plasma as oxidation agents does not affect significantly the surface morphology of the fibers, but greatly increases the number of surface oxygen functions. The air and carbon dioxide treatments do not lead to significant increase either of the surface area, or of the quantity of surface oxygen containing groups, despite the important weight loss attained (50%). This peculiar observation has been interpreted by considering the presence of traces of iron at the fibers surface, which catalyse the gasification of carbon. Removal of this iron by acid washing allows an improvement of the specific surface area. A detailed study of the gasification in air gave valuable informations on the intimate structure of the VGCF.

Characterisation and reactivity of activated carbon supported platinum catalysts prepared by fluidised bed organometallic chemical vapour deposition (FBOMCVD)

Publisher Summary In the course of developing new methods for the preparation of heterogeneous catalysts, this chapter illustrates that the combination of organometallic chemical vapor deposition (OMCVD) and the fluidization of a bed of porous particles is a powerful method to prepare supported catalysts. Highly dispersed deposits of rhodium, palladium, and platinum on metal oxide supports were obtained in a single step using a fluidized bed reactor. The method of chemical vapor deposition (CVD) allows direct deposition of the active phase onto the catalyst support by means of the reaction between surface sites containing oxygenated groups and the vapor of a suitable organometallic compound. Using silica or alumina with large specific areas—around 200 m 2 g -1 —the presence of hydroxyl groups on the surface allows the facile grafting of small and dispersed particles of the noble metal (2–5 nm).