Oxidized iron nanoparticles obtained by high-power plasma cutting E.D. Cabanillas CONICET and Departamento de Combustibles Nucleares, Comisión Nacional de Energía Atómica, Argentina abstract article info Article history: Received 7 August 2007 Accepted 29 July 2008 Available online 5 August 2008 Keywords: Nanomaterials Plasma cutting Electron microscopy Metallurgy A high-power industrial plasma cutting equipment was applied to carve a SAE 1010 carbon steel. The usually discarded cut material was observed by scanning electron microscopy (SEM) showing that hollow and entire microspheroidal particles were produced. The analysis with X-ray diffraction (XRD) evidenced that the composition of microparticles was FeO, Fe 2 O 3 and Fe 3 O 4 . By transmission electron microscopy (TEM) it was found that spherical nanoparticles in the range of 2 to 150 nm in diameter were formed. © 2008 Elsevier B.V. All rights reserved. Electroerosion [1–3] and laser ablation are non-conventional thermal methods capable of producing micro and nanoparticles. In this communication we have found that with the plasma cutting technique it is also possible to obtain the same type of microscopic spheroidal oxidized particles, hollow and entired from 0.4 to 100 μm in diameter and also spherical nanoparticles. To our knowledge, in the literature there are no references to the type and quality of the scrap produced by industrial high plasma cutting devices. However, taking advantage of the blowing gas current that removes the liquid metal, we have found that along its flight the detached drops acquire a quasi- spherical shape. This type of spheroidal particles finds applications in several processes, in particular in the manufacture of fuel for nuclear reactors. In this communication, we show by TEM observations that the industrial plasma cutting method is effective to produce nanoparticles having a narrow distribution of sizes and very uniform shape. We employed an industrial equipment operated at 30 A and 9 kW using air as impelling gas and a conventional torch. The powder was picked from the debris reservoir and sieved in different size intervals. Particles smaller than 20 μm were sonized with alcohol and held in an amorphous carbon layer of a copper grid and observed by a CM200 Philips equipment operated at 200 kV. We obtained the debris den- sity of all the unsieved material using an ultrapycnometer “Quanta- chrome” designed to evaluate the volume and actual density of powders measured at 20 °C. The X-ray data were taken with CoK-α radiation in a conventional diffractometer. A general view of the microparticles is presented in Fig. 1 . The nano-details of their conglomerates are displayed in Fig. 2 while Fig. 3 shows a picture of the smallest particles captured by our TEM equipment. Fig. 4 exhibits the distribution size of the nanoparticles and the X-ray diffractogram of the captured particles is exhibited in Fig. 5. The measured density of the debris was calculated to be 3.3± 0.3 g cm - 3 . In the high-power plasma cutting process an electric potential difference is applied between the piece to be cut and the torch. The electric field rises and ionizes the gas forming a plasma and in this way an electric discharge takes place. Like in the electroerosion and the laser ablation processes the piece surface reaches a swift temperature increase and melts a small part of the material and like to the laser ablation process, the emerging gas from the torch expels the liquid metal which reaches its spherical shape during its cooling when flying Materials Letters 62 (2008) 4443–4445 E-mail address: cabanill@cnea.gov.ar. Fig. 1. SEM micrograph showing a general view of the plasma ablationed material. 0167-577X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2008.07.044 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet