Synthesis of Carbon Nanotubes by Microwave Method: Mathematical Modeling and Practical Implementation

The article presents the synthesis of carbon nanotubes (CNT), which are intended to obtain functional properties in polymer composites. One of these functional properties of polymer composites is electrical and thermal conductivity. CNTs synthesized using the microwave method differ in both geometric and morphological characteristics, as well as the presence of deposited iron particles on the surface of the CNT graphene layer. Microwave synthesis of CNT is carried out in a 700 W setup using different ratios of the graphite–ferrocene mixture (4 : 1 (10 s), 5 : 1 (10 s), 6 : 1 (10 s), and 4 : 1 (20 s)). The obtained CNT samples are characterized by Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction analysis. It is shown that as a result of combinations of ferrocene and graphite in various ratio (4 : 1 (10 s), 5 : 1 (10 s), 6 : 1 (10 s), and 4 : 1 (20 s)), different CNT morphologies are formed. This circumstance allows effective filling of polymers, including silicones, thereby creating functional composites. Analysis of electron microscopy data allows us to conclude that all of the synthesized CNTs have different geometric characteristics. The diameter of the CNTs can range from 30 to 60 nm and iron particles are present on the surface of the CNTs. At the same time, an increase in the specific surface area of the studied CNTs is observed. When microwaves are applied to a mixture consisting of ferrocene and graphite, the microwaves form local electric dipoles in the material, which is caused by structural defects in individual graphite layers. It is established that microwave synthesis is a fast method for obtaining CNT (synthesis time is approximately 10 s at a microwave radiation power of 700 W) and can be used for the targeted synthesis of CNT with different structures and morphologies, which are intended for modifying polymers and creating functional composites with a wide range of thermal and electrophysical properties.