Magnetometric Studies of Catalyst Refuses in Nanocarbon Materials

It is shown that magnetometry can be employed as an effective tool to control the content of a ferromagnetic constituent in nanocarbon materials. We propose a thermochemical treatment protocol to achieve extensive cleaning of the source nanocarbon materials from ferromagnetic refuses

Graphene -- Based Nanocomposites as Highly Efficient Thermal Interface Materials

We found that an optimized mixture of graphene and multilayer graphene - produced by the high-yield inexpensive liquid-phase-exfoliation technique - can lead to an extremely strong enhancement of the cross-plane thermal conductivity K of the composite. The "laser flash" measurements revealed a record-high enhancement of K by 2300 % in the graphene-based polymer at the filler loading fraction f =10 vol. %. It was determined that a relatively high concentration of single-layer and bilayer graphene flakes (~10-15%) present simultaneously with thicker multilayers of large lateral size (~ 1 micrometer) were essential for the observed unusual K enhancement. The thermal conductivity of a commercial thermal grease was increased from an initial value of ~5.8 W/mK to K=14 W/mK at the small loading f=2%, which preserved all mechanical properties of the hybrid. Our modeling results suggest that graphene - multilayer graphene nanocomposite used as the thermal interface material outperforms those with carbon nanotubes or metal nanoparticles owing to graphene's aspect ratio and lower Kapitza resistance at the graphene - matrix interface.Comment: 4 figure

Single step process for the synthesis of carbon nanotubes and metal/alloy-filled multiwalled carbon nanotubes

A single-step approach for the synthesis of multi-walled nanotubes (MWNT) filled with nanowires of Ni/ternary Zr based hydrogen storage alloy has been illustrated. We also demonstrate the generation of CO-free hydrogen by methane decomposition over alloy hydride catalyst. The present work also highlights the formation of single-walled nanotubes (SWNT) and MWNTs at varying process conditions. These carbon nanostructures have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), Energy dispersive X-ray analysis (EDX) and Raman spectroscopy. This new approach overcomes the existing multi-step process limitation, with possible impact on the development of future fuel cell, nano-battery and hydrogen sensor technologies

The role of metal nanoparticles in the catalytic production of single-walled carbon nanotubes - A review

Recent progress in chemical vapour deposition and aerosol synthesis of single-walled carbon nanotubes (SWCNTs) is reviewed with an emphasis on the role of metal nanoparticles in the processes. The effect of the various parameters on SWCNT formation is reported on the basis of published experiments. Evolution of the catalyst particle size distribution due to collision, sintering and evaporation of metal during SWCNT synthesis is discussed. The active catalyst has been demonstrated to be in a reduced metal form by comparison of the experimental data and calculations regarding the equilibrium concentration of carbon and oxygen in iron. Also the effect of the catalyst particle size on melting temperature and carbon solubility in metal is discussed. The stability of different carbon precursors (hydrocarbons and carbon monoxide) is considered thermodynamically. Furthermore, estimation of the maximum length of 1 and 2.5 nm diameter SWCNTs as a function of carbon solubility is conducted to determine whether carbon dissolution and precipitation are simultaneous or subsequent process steps

Thermal and electrical conductivity of single- and multi-walled carbon nanotube-epoxy composites

The electrical and thermal conductivities of epoxy composites containing 0.005-0.5 wt% of single-walled (SWNTs) or multi-walled (MWNTs) carbon nanotubes have been studied. The MWNT composites had an electrical percolation threshold of < 0.005 wt%, whereas the thermal conductivity of the same samples increased very modestly as a function of the filler content. In the case of the SWNT composites, the electrical percolation thresholds were higher (0.05-0.23 wt%) whereas the thermal conductivity was lower than that of the pristine epoxy. (c) 2005 Elsevier Ltd. All rights reserved

Carbon nanotube synthesis from alcohols by a novel aerosol method

Single- and multiwalled carbon nanotubes (CNTs) were synthesised by a novel aerosol method using alcohols, namely ethanol and octanol, as carbon precursors. Preformed iron and nickel aerosol nanoparticles, produced by evaporation from resistively heated metal wire, were used as catalysts. Multiwalled CNTs were initiated by 10 nm sized catalyst particles and produced in the presence of ethanol vapour with the partial pressure of 7072 Pa, while combination of 2.4 nm particles and decreased alcohol vapour pressure (123 Pa) resulted in the formation of mainly single-walled and a small fraction of double-walled CNTs. The effect of a promoter (thiophene) in the system was found to be very important for the synthesis of multiwalled CNTs, while only a 30% number concentration increase was found for the single-walled CNT production. © Springer 2006