István Vesselényi

Large scale production of short functionalized carbon nanotubes

A simple mechano-chemical modification of multiwall carbon nanotubes is described. The use of ball-milling in specific atmosphere allows us to introduce functional groups like thiol, amine, amide, carbonyl, chlorine, etc. onto carbon nanotubes. The resulted functional groups are characterized using infrared spectroscopy and X-ray photoelectron spectroscopy.

Mechanical and chemical breaking of multiwalled carbon nanotubes

Catalytically prepared multiwall carbon nanotubes (MWNTs) were cut and functionalised by mechanical and/or chemical methods. Products were characterised by transmission electron microscopy, infrared spectroscopy and BET method. It can be concluded that physical and chemical breaking procedures complete each other very well. With certain MWNT samples containing surface oxides preliminary investigations were done for testing them as catalyst support.

Comparison of Fe/Al/sub 2/O/sub 3/ and Fe, Co/Al/sub 2/O/sub 3/ catalysts used for production of carbon nanotubes from acetylene by CCVD

Characterization of iron containing alumina supported catalysts was performed by transmission electron microcopy (TEM), Mo/spl uml/ssbauer, and XPS spectroscopy during formation of multiwall carbon nanotubes from acetylene at 1000 K. TEM images showed that carbon fibers (outer diameter is around 20-40 nm) were generated on Fe/Al/sub 2/O/sub 3/ samples while on the bimetallic Fe,Co/Al/sub 2/O/sub 3/ carbon nanotubes with an average diameter of 8-12 nm were formed. XPS spectra revealed that Fe-Co alloy formed during the interaction of Fe,Co/Al/sub 2/O/sub 3/ and acetylene at 1000 K. The formation of the bimetallic alloy was proven by Mo/spl uml/ssbauer spectroscopy as well.

Production of Carbon Nanotubes on Different Metal Supported Catalysts

Multiwall carbon nanotubes have been prepared by catalytic chemical vapor deposition (CCVD) method in high yield using various metals supported on different supports. Measurements by transmission electron microscopy (TEM) revealed the presence of high quality nanotubes on each catalyst, however, comparing the different catalysts in nanotube production it can be stated that beyond metals, the support also affects both the quality and the quantity of nanotubes.

Functional groups generated by mechanical and chemical breaking of multiwall carbon nanotubes

Since the discovery of carbon nanotubes several attempts were made to modify them by various physical and chemical methods. Applying a ball-milling system mechanical cutting of nanotubes can be achieved. TEM, surface area and porosity measurements are used to follow these changes on the nanotubes. Using different reagents and methods functional groups can be generated on the nanotubes. To prove the existence of these groups infrared spectroscopy is used. Finally, it will be shown that the physical and chemical breaking processes complete each other very well.

Mechano‐chemical functionalization of carbon nanotubes

Short, functionalized multiwall carbon nanotubes were prepared by a simple mechano‐chemical way. The fundamental idea of our method is breaking of the nanotubes under reactive gas atmosphere such as CO, COCl2, Cl2, NH3, CH3SH in a ball mill. During this ball milling procedure the tube length decreased to 200–300 nm, while the specific surface area increased by about 20% and the inner pore of the nanotubes became accessible.

Mechanical cut of carbon nanotubes

Ball milling technique is a very efficient way of breaking carbon nanotubes. After 100 hour grinding the length of the tubes decrease to 200–300 nm although the final material contains high‐density particles, thus further purification method is necessary. We present a purification method using KMnO4 to destruct the particles and form well separated nanotubes.

Comparison of Fe/Al2O3 and Fe,Co/Al2O3 catalysts used for production of carbon nanotubes from acetylene by CCVD

Investigation of the properties of nanometer sized particles is in the focus of material and chemical science. Several questions about the synthesis and application of carbon nanotubes have been addressed the researchers working in nanoscience and nanotechnology. The catalytic chemical vapor deposition (CCVD) method proved to be one of the most prosperous technologies for large scale production of both single and multiwall carbon nanotubes. It has been proven that supported transition metals are the most productive catalysts for CCVD. The bimetallic catalysts showed excellent catalytic activity in conversion of acetylene to multi wall carbon nanotubes (MWNT) . In our previous papers, we dealt with the cobalt-iron bimetallic catalytic system. We showed that the best quality MWNTs with high yield was observed on Co-Fe catalyst. From the in situ XPS results we concluded that Co-Fe alloy phase should be formed on the catalyst treated at high temperature in acetylene atmosphere, furthermore, we attributed the effectiveness of this catalyst to the presence of alloy phase. However, we have also indicated the importance of Mössbauer spectroscopic studies. In this contribution we report on the results of Mössbauer spectroscopy supplementing our previous conclusions drawn by chemical and XPS techniques.

Comparative Study of Catalysts containing Transition Metals in Production of Carbon Nanotubes

For production of multiwall carbon nanotubes (MWNT) by catalytic chemical vapour deposition (CCVD) different transition metals supported on amorphous or crystalline oxides such as silica, alumina or zeolites were used. In several cases both the productivity of catalysts and the quality of MWNT are improved by using bimetallic catalysts such as Co‐Fe, Co‐V etc. In this publication we report the results in comparison of mono and bimetallic catalysts of Co, Fe, Ni and V supported on alumina, zeolite 13X‐FAU and zeolite ZSM‐5‐MFI.