South Urals State University, Chelyabinsk, Russia:

G. D. Apalkova, Professor, e-mail: apalkova@yandex.ru

This paper examines a relationship between the globular and acicular structure of iron oxide nanoadditives and the properties of graphite. It is shown that under similar conditions the effectiveness of the acicular iron oxide rises in comparison with the nanoadditives having globular structure, which leads to an average of 14% decrease in the specific electrical resistance of graphite and a 20–22% increase in mechanical strength. When electrodes are pressed in a piercing press, the acicular particles of the nanoadditive go parallel to the press centre line, as is typical of anisometric elements. During mixing, the polar components of the pitch — i.e. asphaltenes, which are a carbon forming component of the pitch, go through chemisorption involving the acicular additive. During baking, the aromatic macromolecules of the coal-tar pitch take a directional orientation of the anisometric grains of the additive, which are something like nucleation centres of a new phase. From the structure with a directional orientation, the following heat treatment (graphitisation) creates a secondary structure — i.e. graphite. If globular additives are used, there is observed no directional orientation of the coke microcrystals, which are the result of the additive added to the pitch, and the process of graphitisation (or, transformation resulting in a three-dimensional layered structure) would require a much higher thermodynamic force. That’s why, under similar conditions, the use of acicular nanoadditives produces graphite with a better structure and a low electrical resistance. Moreover, the anisometric grains of the nanoadditive serve to reinforce the graphite phase forming from the coaltar pitch, which is the weakest link in the graphitised composition. The findings suggest that the acicular structure of iron oxide nanoadditives improves the physical and mechanical properties of the graphite phase formed from the coal-tar pitch, which reduces the risk of fracturing and enhances the durability of electrodes.
The research reported in this paper was funded by the Government of the Russian Federation (Decree No. 211 dated 16 March 2013), Agreement No. 02.A03.21.0011.

1. Valyavin G. G., Zaporin V. P., Rizvanov I. V. The practice of producing acicular coke at oil refineries of the USSR and the current potential of launching its industrial production. Electrodes & structural and composite carbon materials: Current status and prospective development: International conference proceedings. Chelyabinsk : Entsiklopediya, 2010. pp. 67–73.
2. Predel H., Nielsen M. Petroleumkoks — Enwicklung und Tendenzen. Erdol und Kohle. 2005. No. 10. pp. 348–352.
3. Valyavin G. G., Khukhrin E. A., Valyavin K. G. The place of delayed coking in the flow diagram of modern oil refineries. Chemistry and Technology of Fuels and Oils. 2007. No. 3. pp. 15–18.
4. Fokin V. P., Kalayda I. N., Ulyanchenko S. V. Upgraded production of graphitised electrodes in Russia. Stal. 2010. No. 4. pp. 46–48.
5. GOST R 57613–2017. Graphite electrodes and nipples. Specifications. Introduced: 01.08.2018.
6. Apalkova G. D. Operation of electrodes in electric arc furnaces in today’s engineering industry. Elektrometallurgiya. 2015. No. 5. pp. 3–11.
7. Borlée J., Wauters М., Mathy C., Weber M. Monitoring system for controlling and reducing the electrode consumption in DC EAF plants. Final report Directorate-General for Research. European Commission, Contract No RFSR–CT–2003–00024 1 September 2003 to 31 August 2006. 2009. 143 p.
8. Armstrong С. R., Bosserman T. L, Haibult K. E. Electrode Consumption in Modem High-Power Electric Steel Shop. Iron & Steel Technology. 2013. No. 1. pp. 57–68.
9. Belkovskiy A. G. Measures to reduce the consumption of electrodes at SDI’s steel melting facility in Butler. Novosti chernoy metallurgii za rubezhom. 2013. No. 2. pp. 23–26.
10. Butakova T. V., Lepp M. V., Bleskin G. S., Spektoruk A. A., Olvovskiy S. A. Enhanced strength and thermophysical properties of bottom blocks by ENERGOPROM — Novosibirsk Electrode Plant. Non-Ferrous Metals and Minerals — 2014: 7^th International Congress. Krasnoyarsk, 2014. pp. 1041–1042.
11. Apalkova G. D., Vesnin A. Ya., Davydovich B. I. Reduced consumption of graphitised electrodes in steel production. Production of light non-ferrous metals and electrodes: Review. Moscow : TsNIIEItsvetmet, 1989. Issue 4. 64 p.
12. Apalkova G. D., Selesnev A. N., Prosvirina I. I. Study of reasons for electrode destruction in high power electric arc Furnaces. 1-st World Conference on Carbon Eurocarbon 2000. Berlin, Germany, 9–13 July 2000.
13. Marsh H., Warburton A. R. Catalysis of graphitization. Journal of Applied Chemistry. 1970. Vol. 20, No. 5. pp. 133–142.
14. Dmitrieva G. V., Zatsepin S. V., Apalkova G. D., Skopets T. L. Interaction between iron oxides and carbon during heat treatment and their effect on the graphite structure. Khimiya tverdogo topliva. 1981. No. 6. pp. 146–149.
15. Apalkova G. D., Dmitrieva G. V., Shipkov N. N. How the dispersion of the iron oxide additive influence the graphite properties. Tsvetnye Metally. 1982. No. 11. pp. 61–62.
16. Apalkova G. D., Dmitrieva G. V. Electrode paste pressing in the presence of iron oxide. Khimiya tverdogo topliva. 1981. No. 2. pp. 135–137.
17. Gao Y., Tang Z. Design and application of inorganic nanoparticle superstructures: current status and future challenges. Small. 2011. Vol. 7, No. 15. pp. 2133–2146.
18. Nasibulin A. V., Antipov E. A., Beilina N. Yu. Effect of adding nanomaterials on on pitch rheological properties. Refractories and Industrial Ceramics. 2017. Vol. 57, No. 7. pp. 299–303.
19. Apalkova G. D. Effect of nanodispersed iron oxide additives on the density of carbon refractories. Novye ogneupory. 2018. No. 11. pp. 50–52.
20. Belenkiy E. F., Riskin I. V. The chemistry and technology of pigments. Leningrad : Khimiya, 1974. 656 p.
21. GOST 10200–2017. Electrode coal-tar pitch. Specifications. Introduced: 01.03.2019.
22. GOST 22898–78. Low-sulphur petroleum cokes. Specifications. Introduced: 01.01.79.