Carbon belong to the most fascinating materials due to its multiplicity of modifications and the associated properties. The amazing structural and unusual morphological properties of turbostratic carbon (TSC), carbon nanofibers (CNF) and carbon nanotubes (CNT) open several research fields and applications. They are characterized by a high specific surface area, high free volume and defined “pore size” resulting in interesting transport properties in membrane application and chemical properties in catalysis.
The focus of this work was the preparation of carbon layers on porous ceramic substrates. TSC layers were prepared by a wet-chemical coating of a polymer on the ceramic substrate followed by first hardening and second carbonization under inert atmosphere at a temperature of 700-900°C. CNT and CNF layers were prepared by chemical vapor deposition using methane as well as ethylene as carbon sources and iron and palladium as catalysts. The samples were characterized by FESEM, HRTEM, Raman spectroscopy and thermal analysis. The CVD-process was coupled with an in-situ infrared spectrometer to investigate the catalyst performance and by-products.
The TSC layers showed a lattice plan distance of 0.42 nm. By using Pd as catalyst, neither single-walled-carbon nanotubes (SWCNT) nor double-walled carbon nanotubes (DWCNT) were observed. The main carbon structure in this case was herringbone CNF. In comparison to that, Fe predominantly catalyzed MWCNT growth in diameter range between approximately 10 nm to 40 nm.
The different carbon layers were tested for gas separation.