Synthesis of core–shell copper–graphite submicronic particles and carbon nano-onions by spark discharges in liquid hydrocarbons

Abstract

Spark discharge in hydrocarbon liquids is considered a promising method for the synthesis of various nanomaterials, including nanocomposites. In this study, copper–carbon particles were synthesized by generating spark discharges between two Cu electrodes immersed in heptane, cyclohexane, or toluene. The synthesized particles were characterized using scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. Overall, two families of particles were observed: Cu particles (diameter < 10 nm) embedded in a carbon matrix and submicrometric Cu particles encapsulated in a carbon shell. The obtained results indicate that the size distribution of the Cu nanoparticles and the degree of graphitization of the carbon matrix depend on the liquid. Indeed, discharges in heptane lead to Cu particles with diameters of 2–6 nm embedded in a carbon matrix of low graphitization degree, while discharges in toluene result in particles with diameters of 2–14 nm embedded in carbon matrix of high graphitization degree. Based on the obtained experimental results, it is proposed that the Cu nanoparticles are produced in the plasma core where Cu (evaporated from the electrode surface) and carbonaceous species (decomposition of the liquid) are present. When the plasma hits the electrode surface, hot (thousands of Kelvin) Cu particles are ejected from the electrode, and they propagate in the liquid. The propagation of the hot particles in the liquid results in the local evaporation of this liquid, which leads to the formation of a C-shell around each Cu particle. In few cases where the shape of the Cu particle is not spherical, carbon nanoonions are detected between the C-shell and the Cu core. These nanoonions are supposedly formed under the effect of the fluid vortices generated close to the particle surfaces when these latter are ejected into the liquid.

A Versatile Route for Synthesis of Metal Nanoalloys by Discharges at the Interface of Two Immiscible Liquids

“…[ 25 , 26 , 27 , 28 ]. This has led to the production of a wide range of nanomaterials, including nanocomposites [ 27 , 29 ] and materials with novel crystallographic phases [ 30 , 31 ]. Although nanoalloys are searched for many applications, their synthesis is, however, not straightforward as it requires either multiple stage experiments [ 32 ] or the use of alloy electrodes [ 33 , 34 ].…”

Spark discharges in liquid heptane in contact with silver nitrate solution: Investigation of the synthesized particles

“…), between electrodes of varying chemical nature (Al, Cu, Pt, Co, Ni, etc. ), [47][48][49][50] a wide range of nanomaterials, including nanocomposites [49,51] and materials with novel crystallographic phases [52,53] can be synthesized.…”

Synthesis of Silicon and Silicon Carbide Nanoparticles by Pulsed Electrical Discharges in Dielectric Liquids

“…The properties of the plasma are significantly different than those of gas-phase plasmas: higher density of species [26], higher temperature [27], higher pressure [28], and shorter lifetime [29]. In these specific conditions, various kind of nanomaterials are produced, including nanocomposites [30,31], metal oxides [32][33][34], as well as novel phases of some materials [35][36]. Spark discharges in liquid usually produce two particle size distributions that are due to two processes: i) local evaporation from the electrode surface that leads to the formation of small particles (few nm in size) and ii) ejection of liquid volume from electrode surface that leads to micron-sized particles [24,31].…”