Optimization of ethanol flow rate for improved catalytic activity of Ni particles to synthesize MWCNTs using a CVD reactor

Abstract

During synthesis of MWCNTs using CVD, role of carbonaceous material and catalyst, besides other process parameters, has considerable influence on the structure and yield of pristine nanotubes. In present study, different flow rates (i.e. 10, 25, 40 and 55 sccm) of precursor ethanol were used for the synthesis of MWCNTs at 750 °C in a CVD reactor, where nickel particles were supported on quartz as catalyst. Further, these nanotubes were characterized using XRD, SEM, TGA and Raman spectroscopy to investigate the effect of ethanol flow rate on the catalytic activity of nickel for optimum production of MWCNTs. It was observed that at different ethanol flow rates, variations in synthesis products (i.e. CNTs, amorphous carbon and carbon nanoparticles) were associated with catalytic activity. Maximum catalytic activity of nickel particles was attained by optimizing ethanol flow rate (at 25 sccm). At the optimum flow rate a maximum purity of MWCNTs (>83%) was attained along with other relevant structures i.e. amorphous carbon <1.5% and SWCNT <10% balancing with retained catalytic particles. Any increase from the optimum limit caused not only defects within the CNTs' structure but also increased the impurities which were correlated with the reduction in activity of the nickel particles due to the saturation of active sites.

A Strategy towards Light-Absorbing Coatings Based on Optically Black Nanoporous Alumina with Tailored Disorder

“…However, since the correlation between the morphological randomness and blackening does not automatically mean their causation, the following hypotheses have to be checked to exclude any chances that the light absorption results from the chemical composition features: Amorphous carbon admixture, which is highly unlikely from the experimental conditions. The decomposition of amorphous carbon in air atmosphere occurs at 315–355 °C [ 19 ], which should also lead to visible color changes. In addition, Raman spectroscopy is a powerful tool for detection.…”

“…Amorphous carbon admixture, which is highly unlikely from the experimental conditions. The decomposition of amorphous carbon in air atmosphere occurs at 315–355 °C [ 19 ], which should also lead to visible color changes. In addition, Raman spectroscopy is a powerful tool for detection.…”

Fractographic Evaluation of Crack Initiation and Growth in Al-CNTs Nanocomposite Fabricated by Induction Melting

“…The multiwalled carbon nanotubes (MWCNTs) of 10 nm diameter were used for the present work, which were synthesized using chemical vapor deposition [2]. Aluminum (grade-1199) was used for the matrix material, which was melted in an air induction furnace under multifunctional fluxes.…”