V.V. Sleptsov - Dr.Sc. (Eng.), Head of the Department, Moscow Aviation Institute (National Research University)
A.V. Savkin - Ph.D. (Eng.), Associate Professor, Moscow Aviation Institute (National Research University)
V.I. Berdnik - Ph.D. (Eng.), Associate Professor, Moscow Aviation Institute (National Research University)
D.U. Kukushkin - Assistant, Moscow Aviation Institute (National Research University)
A.O. Diteleva - Assistant, Moscow Aviation Institute (National Research University)
The unique properties of nanoparticles have been the subject of intense research for several decades. A number of methods for ob-taining nanoparticles have been developed, which can be conditionally divided into two groups: chemical methods and physical methods (dispersion). To obtain submicron and nanoscale particles of conductive materials (metals, alloys and semiconductors), a method of synthesis based on the electrospark erosion of raw materials in a liquid dielectric using the Electrical Discharge Machine (EDM), which is very attractive in its simplicity and accessibility, was proposed. However, this method and a number of other known methods for synthesizing nanoparticles have the disadvantage of a large dispersion in the sizes (from 1 to 100 nm) of produced nanoparticles. The results obtained by different groups of researchers made it possible to better understand the process of electrospark synthesis of nanoparticles, but could not eliminate the drawback associated with a large scatter of nanoparticle sizes. This can be due to several factors. On the basis of these results and arguments, we made the assumption that a decrease in the spread of the sizes of the produced nanoparticles is possible due to a change in the conditions for the occurrence of a spark breakdown, so that the process proceeds much faster. This can be achieved if a significant overvoltage is created on the EDM electrodes, which is not possible in any previously described scheme. To create an overvoltage, another switching element must be added to the circuit, which would commute the charged capacitor and the EDM electrodes to a high voltage. An experimental EDM was developed with the possibility of creating an overvoltage at the electrodes. A high-voltage capacitor with a capacity of 1000 pF was used in the experimental EDM. The capacitor was charged from a high-voltage AC transformer (50 Hz) to a voltage of 1-10 kV. For capacitor switching, an air electric spark gap is used, which is an air gap of 1 mm width between two 50 mm2 electrodes. The capacitor charged to a voltage sufficient to breakdown the air gap and the electrode system is discharged through the air gap to the working electrodes immersed in the liquid dielectric. As a liquid dielectric, distilled water was used in the experiment. The working electrodes were made of silver, for the experiment, a gap of 70 μm was established between them. For uniform consumption of electrode material during erosion, rotation of working electrodes relative to each other was provided.
The experiment showed that at the indicated values of the parameters of the experimental setup, the breakdown voltage was of the order of 4 kV, and the discharge current in the pulses reached values of 12 kA. The obtained samples of silver nanoparticles were subjected to the investigation of the size distribution by the method of dynamic light scattering (DLS), the measurement was carried out with the Photocor Compact-Z. The diameter of more than 80% of nanoparticles lies in the range of 20-45 nm. In addition to the DLS method, images obtained with the transmission electron microscope LEO-912 AB OMEGA were used to confirm the nanoparticle size distribution. The electron diffraction pattern of the obtained nanoparticle samples and its comparison with a sample of crystalline silver showed that the nanoparticles obtained consist of crystalline silver, without a noticeable admixture of oxides or salts. The possibility of producing nanoparticles by electrospark erosion under conditions of considerable overvoltage of the discharge gap was demonstrated. The resulting silver nanoparticles had a spherical shape and a rather narrow size distribution.
This work was supported by the grant № 8.7552.2017/BP from the Ministry of Education and Science of Russian Federation.
- Yong Yan, Scott C. Warren, Patrick Fuller, Bartosz A. Grzybowski. Chemoelectronic circuits based on metal nanoparticles // Nature Nanotechnology. 2016. № 11. Р. 603–608.
- Karmakar S., Kumar S., Rinaldi R., Maruccio G. Nano-electronics and spintronics with nanoparticles // Journal of Physics: Conference Series. 2011. V. 292. Р. 012002.
- Theodorakos I., Zacharatos F., Geremia R., Karnakis D., Zergioti I. Selective laser sintering of Ag nanoparticles ink for applications in flexible electronics // Applied Surface Science. 2015. V. 336. Р. 157162.
- Gubin S.P., Koksharov Yu.A., Khomutov G.B., Yurkov G.Yu. Magnetic nanoparticles: preparation, structure and properties // Russian Chemical Reviews. 2005. V. 74(6). Р 489520.
- An-Hui Lu, Salabas E.L., Ferdi Schüth. Magnetic Nanoparticles: Synthesis, Protection, Functionalization, and Application // Angewandte Chemie. 2007. V. 46. Is. 8. Р. 1222–1244.
- Namita Rajput. Methods of preparation of nanoparticles – a review // International Journal of Advances in Engineering & Technology. 2015. V. 7. Is. 4. Р. 18061811.
- Berkowitz A.E., Walter J.L. Spark erosion: A method for producing rapidly quenched fine powders // Journal of Materials Research. 1987. V. 2. Is. 2. Р. 277288.
- Hong J.I., Parker F.T., Solomon V.C., Madras P., Smith D.J., Berkowitz A.E. Fabrication of spherical particles with mixed amorphous/crystalline nanostructured cores and insulating oxide shells // J. Mater. Res. 2008. V. 23. Р. 17581763.
- Nguyen P.K., Lee K.H., Moon J., Kim S.I., Ahn K.A., Chen L.H., Lee S.M., Chen R.K., Jin S., Berkowitz A.E. Spark erosion: a high production rate method for producing Bi0.5Sb1.5Te3 nanoparticles with enhanced thermoelectric performance // Nanotechnology. 2012. V. 23. Р. 415604.
- Carrey J., Radousky H.B., Berkowitz A.E. Spark-eroded particles: Inﬂuence of processing parameters // Journal of applied physics. 2004. V. 95. Is. 3. . 823829.
- Monastyrsky G. Nanoparticles formation mechanisms through the spark erosion of alloys in cryogenic liquids // Nanoscale Research Letters. 2015. № 10. Р. 503.
- Yifan Liu, Xianglong Li, Fushi Bai, Jian Chen, Yantao Wang, Nan Liu. Effect of system parameters on the size distributions of hollow nickel microspheres produced by an ultrasound-aided electrical discharge machining process // Particuology. 2014. № 17. Р. 36–41.
- Mohammad T. Shervani-Tabar, Nima Mobadersany. Numerical study on the hydrodynamic behavior of the dielectric ﬂuid around an electrical discharge generated bubble in EDM // Theoretical and Computational Fluid Dynamics. 2013. V. 27. Р. 701–719.