Investigation of the stability of nanofluids based on water and carbon nanoparticles synthesized by the electric arc method

In this work, arc discharge synthesis was carried out by sputtering electrodes of various compositions in a helium medium, as a result of which two types of materials containing carbon globules and graphene flakes were obtained. The synthesized materials were characterized with transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. The effect of the type and concentration of carbon nanoparticles and the type of surfactants on the stability of water-based nanofluids was studied with optical spectroscopy. For carbon globules and water, the mass concentrations of nanoparticles and sodium dodecyl sulfate were determined to obtain a nanofluid based on them stable for 1 month, which are 0.02% and 1%, respectively. It was shown that the use of neonol AF 9-12 at a concentration of 2% didn’t lead to the stabilization of carbon globules with a mass concentration of 0.02% in water. For graphene flakes, the mass concentrations of nanoparticles and stabilizers to obtain a water-based nanofluid stable for 1 month were: 0.02% graphene flakes and 1% SDS, as well as 0.02% graphene flakes and 2% neonol AF 9-12, respectively

Effect of Toluene Addition in an Electric Arc on Morphology, Surface Modification, and Oxidation Behavior of Carbon Nanohorns and Their Sedimentation in Water

Carbon nanohorns (CNHs) are attractive for various applications, where a high specific surface area and long dispersion stability in water are important. In the present work, we study these parameters of CNHs prepared by arc evaporation of graphite depending on the conditions of the synthesis and subsequent oxidation in air. It is shown that the addition of toluene in the reactor during the arcing allows obtaining CNHs functionalized with −CHx groups. Heating of CNHs in air at 400 °C leads to substitution of −CHx groups for oxygen-containing groups. Moreover, the CNH endcaps are opened at 500 °C, and as a result, the specific surface area of CNHs increases 4 times. Aqueous suspensions with a concentration of oxidized CNHs of 100 µg/mL are stable for 8 months