Search

Nitrogen doped multi-walled carbon nanotubes and other carbon nanoparticles were synthesized by catalytic chemical vapor deposition of tripropylamine and acetylene on CaCO₃-supported cobalt catalyst (5 wt%), prepared by impregnation, and various precursors. Each synthesis was performed by using either the pure nitrogenous organic compound or its mixture with acetone. Transmission electron microscopy studies revealed a significant difference both in the yield and the diversity of the carbon deposits. Every synthesis resulted in bamboo-like nanotubes, and nearly all of them also in onion-like structures. Electron energy loss spectroscopy studies of the samples indicated the presence of nitrogen and calcium (caused by the catalyst support). High-resolution transmission electron microscopy and X-ray diffraction measurements were also performed to characterize the samples.

An easy way of controlling pore sizes during the preparation of cellulose nanopapers using nanofibrillated cellulose and different solvents, such as water, ethanol and acetone, was applied in this study. A possible mathematical model is also presented, that describes the occuring processes, which model is based on simple probability theory computations taking the number of possible hydrogen bonds into consideration. This model allows the better understanding of the solvent dependence of pore formation on a molecular level. For the comparison of the effects of solvents two different series of cellulose nanopapers were prepared. In the cases of both series, an aqueous nanofibrillated cellulose suspension was used for the fabrication of nanopapers, and different solvents were used for their modification. Based on scanning electron microscopy images and mercury intrusion porosimetry data it has been concluded, that using different solvents was a crucial point in controlling pore sizes. A theory about the swelling effects, as well as the formation and decomposition of nanofibrillated cellulose aggregates based on the hydrogen bonding abilities of the solvents, was proposed and proven in this paper. As-prepared nanocellulose papers can be excellent candidates for further applications as support materials (e.g., virus filtration).