ABSTRACT
The formation of carbon nanotubes (CNTs) occurs typically between 600 and 1000°C. Due to the low-temperature process, chemical vapor deposition (CVD) method is generally better for the production of the multiwall carbon nanotubes (MWCNTs) as compared to other synthesis methods. The transition metals used for CNT synthesis are Fe, Co, and Ni. The wet impregnation methods are used for binary catalyst preparation and the starting materials are ferric nitrate, cobalt nitrate, and nickel nitrate. The samples are prepared with 1, 3, and 5% catalyst weight percentage with a CaCO3 substrate. Thermogravimetric and differential temperature analysis (TG–DTA) is 106carried out to study the effect of weight loss as well as oxide transition in the presence of inert gas. It is observed that at 417°C, the crystallization of γ-Fe2O3 occurs; also, the reduction of the Fe3O4 to FeO occurs at 712°C. Similarly, nickel nitrate starts its water separation at 268.25°C, partial oxidation starts at 388.25°C, and finally nickel oxide formation takes place at 503.25°C. The CaCO3 reduction to CaO occurs at 700°C with 40% weight reduction. TG–DTA curve shows catalytic decomposition temperature. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images substantiate the result reflecting uniform diameter of CNTs produced by CVD method.
