Multi-wall carbon nanotubes (MWCNTs) were synthesized on carbon fiber cloth by chemical vapor deposition using natural gas as the carbon source and FeSO4·7H2O powder as the catalyst precursor. Scanning and transmission electron microscopy and Raman spectroscopy were used to characterize the product. Small catalyst particles were observed on the top of the tubes. The MWCNTs were dispersed uniformly and aligned perpendicular to the cloth. They had a high crystallinity, and few impurities and defects. The density and structure of the MWCNTs on the cloth can be controlled by deposition temperature and time.

The initial redox potential is employed to control the quality of expandable graphite prepared from natural flake graphite by chemical oxidation using KMnO₄ as oxidant and sulfuric acid as intercalation agent. The effects of the initial redox potential on the layer structure and the expansion volume of the expandable graphite are investigated by scanning electron microscopy and X-ray diffraction. Results show that there is an optimum initial redox potential range between 1340 and 1819mV, at which the extent of graphite layer oxidation is moderate and the intercalation reaction is complete. Low-order graphite intercalation compounds are formed and a high expansion volume of the expandable graphite can be obtained in this potential range. The redox potential can be used as a quality control parameter for the industrial preparation of expandable graphite.

Expanded graphite (EG) was loaded with iron by impregnating with ammonium carbonate and ferric nitrate solution. Carbon nanotubes (CNTs) were grown on the EG by iron-catalyzed chemical vapor deposition, using acetylene as a carbon source to form hybrids that were used as a conductive filler to produce conducting polybutylene terephthalate (PBT) composites by an extrusion method. It is found that the CNTs are not entangled and are easy to disperse. The CNT average diameters are 40, 20 and 40nm, and their lengths are 2, 3.7 and 2.6μm for iron loadings of 1.13, 0.75 and 0.57 mass%, respectively. The thickness of the EG is reduced to 10-30nm as a result of CNT insertion into the graphene layers of the EG. The content of CNTs in the hybrids increases from 50 to 85 mass% with the increasing iron content. The conductive PBT modified by the hybrids (5 mass%) derived from EG loaded with 0.75 mass% iron has a surface resistance of 1.55×104Ω/cm², significantly lower than that (1.55×1010Ω/cm²) of the PBT modified by CNTs with the same amount of filler added.