Carbon Nano-Flakes Produced by an Inductively Coupled Thermal Plasma System for Catalyst Applications

Abstract

Carbon material was produced using an inductively coupled thermal plasma torch system of 35 kW and a conical shape reactor. The carbon nanopowders were obtained by plasma decomposition of methane at various flow rates and show a uniform microstructure throughout the reactor. The product has a crystalline graphitic structure, with a stacking of between 6 and 16 planes and a nano-flake morphology with particles dimensions of approximately 100 nm long, 50 nm wide and 5 nm thick. Nitrogen was also introduced in some synthesis experiments along with the methane precursor using flow rates of 0.1 and 0.2 slpm. The resulting product has the same structural properties and the nitrogen is incorporated into the graphitic structure through pyridinic type bonds.

Carbon Nanoparticle Production by Inductively Coupled Thermal Plasmas: Controlling the Thermal History of Particle Nucleation

“…A reduction of the velocities with increasing pressure translates into a longer residence time of the particles in the hot areas of the reactor where nucleation is expected to occur (typically in the 3,000-5,000 K zone as discussed in the next section). It was however demonstrated experimentally that this difference did not have a significant effect on the carbon powders morphology [8,12]. When plasma power is increased to 20 kW a similar trend in the velocity profiles is observed, with higher velocities values, around 115, 50 and 30 m/s for reactor pressures of 20.7, 55.2 and 101.3 kPa, respectively.…”

“…6 all showed identical and spatially uniform morphologies in the shape of graphene flakes, thereafter called CNF, as shown on Fig. 7 [12]. Uniformity of this The following section focuses on the case of a reactor pressure value of 55.2 kPa as being representative for the generation of a uniform morphology of the CNF.…”

“…A higher pressure drop is maintained across the annular gap in comparison to the pressure drop in the manifold, ensuring in this way a highly symmetric radial outlet flow pattern of the gases from the collection plate. This geometry also provides a symmetric flow pattern within the reactor chamber above the collection plate and a stagnation point flow geometry on the plate itself [9,12].…”

“…Our previous work concentrated on creating clean, homogeneous, strongly graphitized CB particles on which a specific nitrogen and iron chemical functionalization is attached. The target objective for these structures being to replace platinum by non-noble and atomically dispersed catalytic sites in polymer electrolyte membrane (PEM) fuel cells [8,12]. The results rapidly showed that the plasma reactor design was a key point in controlling the energy/flow fields and the resulting particle structure [8].…”

“…A reactor geometry enabling a control of these fields also provided the means to transform the spherical CB nanostructure into a flake-like structure consisting of a stacking of around 6-16 graphene layers, thereafter called carbon nanoflakes (CNF). A closer analysis of these structures indicated the very high crystallinity of the material generated, the elimination of the impurity by-products such as volatile organic compounds (VOCs), and the inclusion of the nitrogen functionalization into pyridinic sites as needed for the non-noble catalyst application [12]. These results are essentially linked to the control of the particle nucleation process now achievable in the thermal plasma reactor.…”