Review of the Design and Operation Criteria of a DC Submerged Arc Discharge Carbon Nanostructure Synthesis Installation

Table 6

Selection of work liquids.

Liquid	Advantages	Drawbacks
Water	Economic, high heat capacity, production of various types of nanostructures, natural phase separation	High carbon loss due to CO emission. High purity of water is required
Saline solution	Obtaining decorated nanostructures, better cooling, and better arc stability	Decorated particles are more toxic. Oxygen is emitted the bonds of which contribute to the agglutination of the CNSs
Cryogenic liquid	Obtaining unique exotic nanostructures (nanoflowers, nanoclusters, and nanohorns)	Expensive, strong bubbling that drags away CNSs (nanosafety risks), use of materials with a small thermal contraction coefficient
Organic solvents	The solvent is an additional source of carbon; when metal electrodes are used, core shell nanoparticles are obtained	Solvents carry the risk of being flammable and toxic
CNSs water suspension	Obtaining nanostructures decorated with metals with lower energy consumption because the power consumed in the discharge with metal electrodes is significantly lower than in graphite	Decorated particles are more toxic. Oxygen is emitted the bonds of which contribute to the agglutination of the CNSs
Water + organic solvents + surfactants	There is a very limited number of publications. Carbon sources increase. The authors claim an increase in CNSs yield. Reduction of fire risk	Purification problems, certain contaminants remain in suspension due to the action of surfactants