An optimization approach for producing carbon nanotubes involving economic and safety objectives

The unique properties of carbon nanotubes (CNTs) make them suitable for an incredible range of applications in materials science, electronics, energy management, and many other fields. CNTs can be manipulated chemically and physically in very useful ways, and their final properties and dimensions strongly depend on the parameters and the nature of the method used for their synthesis, this is why many methods of synthesis have been reported. Several key parameters and operating conditions have to be manipulated to produce CNTs with suitable properties for future applications, and it is evident that all these methods of synthesis need to be optimized. This paper presents an optimization approach for determining the best synthesis method and their corresponding operating conditions for synthesizing carbon nanotubes accounting for technical and economic issues as objective functions for a desired application. Proper correlations for the interaction between the considered variables are proposed, and these correlations are based on experimental data taken from literature. A case study considering three synthesis methods of carbon nanotubes (arc discharge, laser ablation, and chemical vapor deposition) is presented. The results indicate that the safest technology with the minimum cost and maximum efficiency was chemical vapor decomposition using turpentine as carbon source (with a cost of 0.374 USD/g, and 0.00088 % fatalities for exposure to 0.1 g of catalyst and 0.000006 % of fatalities per exposure to 4 g of carbon source during 8 min of processing).