Study Of Carbonaceous Materials Research Articles

Nitrogen Doped Carbon Nanotubes from Organometallic Compounds: A Review

Nitrogen doped carbon nanotubes (N-CNTs) have become a topic of increased importance in the study of carbonaceous materials. This arises from the physical and chemical properties that are created when N is embedded in a CNT. These properties include modified chemical reactivity and modified conductivity and mechanical properties. A range of methodologies have been devised to synthesize N-CNTs. One of the procedures uses a floating catalyst in which an organometallic complex is decomposed in the gas phase in the presence of a nitrogen containing reactant to give N-CNTs. Most studies have been limited to ferrocene, ring substituted ferrocene and Fe(CO)5. This review covers the synthesis (and properties) of N-CNTs and other shaped carbon nanomaterials (SCNMs) produced using organometallic complexes. It summarizes the effects that physical parameters such as temperature, pressure, gas flow rates, type and concentration of N source etc. have on the N-CNT type, size and yields as well as the nitrogen content incorporated into the tubes that are produced from organometallic complexes. Proposed growth models for N-CNT synthesis are also reported.

High-Resolution Solid-State NMR Study of the Occurrence and Thermal Transformations of Silicon-Containing Species in Biomass Materials

The occurrence of silicon in two kinds of biomass (rice hulls and endocarp of babassu coconut) and the thermal transformations taking place in these materials under heat treatments are studied here. We report also the production, characterization, and study of carbonaceous materials with high SiC content through the carbothermal reduction of silica, using these natural precursors. X-ray diffraction, scanning electron microscopy, and 13C and 29Si room temperature high-resolution solid-state NMR measurements are used in the characterization and study of the materials as well as the process of SiC formation. Important conclusions about the nature of silicon in these types of biomass and the effects of heat treatments on the structure of silicon-containing species are derived from the results presented. It is shown that silicon in these materials occurs in two distinct forms: amorphous hydrated silica and organically bound silicon species. The influence of spin−lattice relaxation dynamics on the NMR spectra ...

00/00553 129Xe NMR study of carbonaceous materials: effects of surface chemistry and nanotexture

00/00553 129Xe NMR study of carbonaceous materials: effects of surface chemistry and nanotexture