Pulsed discharge production of nano- and microparticles in ethanol and their characterization

Nanoparticles were synthesized using a pulsed arc submerged in ethanol. Two electrode configurations, (a) a 1×4 mm and a 10×10 mm graphite electrodes, and (b) Ni, W, and steel rod electrode pairs, were used. The liquid was arc treated for 5 min with 100 A peak current, 20 μs duration pulses, at a repetition rate of 100 Hz. Samples were obtained by extracting liquid from the top of the treatment vessel, and by allowing the liquid to evaporate from the vessel, and collecting the residue. The samples were examined by HRTEM, HRSEM, XRD, and X-ray photoemission spectroscopy (XPS). Carbon nanoparticles with an onion-like structure, i.e., composed of concentric spherical layers, were found in the samples from the top of the liquid vessel after arcing with either C or Ni electrode pairs. These particles typically had an o.d. of 15-20 nm, and the diameter of the interior void was approximately 5-8 nm. In some cases, the onions were clustered together, such that a typical cluster size was 50-60 nm. Ni and W nanoparticles were produced by treatment with Ni and W electrodes, respectively. The particles could be electrically collected by applying a potential difference between a pair of collection electrodes submerged in the fluid. The Ni particles with sizes of ∼15 μm drifted in the direction generally towards the positive electrode with velocities of approximately ∼2.5-3.5 mm/s in a d.c. electric field of 100 V/mm.