Effect of a Metallocene Catalyst Mixture on CNT Yield Using the FC-CVD Process

This work studies synthesis of carbon nanotube (CNT) sheet using the high temperature (1400 °C) floating catalyst chemical vapor deposition (FC-CVD) method. Three metallocenes—ferrocene, nickelocene, cobaltocene—and their combinations are used as precursors for metal catalysts in the synthesis process. For the carbon source, an alcohol fuel, a combination of methanol and n-hexane (9:1), is used. First, the metallocenes were dissolved in the alcohol fuel. Then, the fuel mixture was injected into a tube furnace using an ultrasonic atomizer with Ar/H2 carrier gas in a ratio of about 12/1. The synthesis of CNTs from a combination of two or three metallocenes reduces the percentage of metal catalyst impurity in the CNT sheet. However, there is an increase in structural defects in the CNTs when using mixtures of two or three metallocenes as catalysts. Furthermore, the specific electrical conductivity of the CNT sheet was highest when using a mixture of ferrocene and cobaltocene as the catalyst. Overall, the multi-catalyst method described enables tailoring certain properties of the CNT sheet. However, the standard ferrocene catalyst seems most appropriate for large-scale manufacturing at the lowest cost

Nitrogen-Doped Flower-Like Hybrid Structure Based on Three-Dimensional Graphene

A new flower-like hybrid structure consisting of nitrogen-doped 3-dimensional (3D) graphene and vertically aligned graphene has been synthesized using a combination of low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques. Active nitrogen (N) species were found to be essential for the growth of the flower-like morphology. N-doping was responsible for enhanced electrical conductivity and wettability of the obtained nano-carbon hybrid structure. Based on the conducted studies a growth mechanism has been proposed. The high specific surface area, low resistance to charge transfer and enhanced specific capacitance of this nitrogen-doped hybrid structure, makes it an excellent candidate material for supercapacitors