A. Romashin Tekhnology Science and Production, Obninsk, Russia:

E. A. Korableva, Leading Production Design Engineer, e-mail: korablea61@mail.ru
D. V. Kharitonov, Deputy Director of Production, Doctor of Engineering Sciences
A. A. Anashkina, Head of laboratory, Candidate of Engineering Sciences, Associate Professor

D. Mendeleev University of Chemical Technology of Russia, Moscow, Russia:
D. O. Lemeshev, Associate Professor, Dean at the Faculty of Technology of Inorganic Substances and High-Temperature Materials, Candidate of Engineering Sciences, Associate Professor

The article discusses potentiality of creating ceramics out of powder system based on ZrO₂ – MgO with nanostructure responsible for heat resistance when in extensive contact with metal melts (special alloys, steels, precious metals). The research results on creation of nanostructured ceramic materials are presented, and the nanotechnologies intended to improve functional properties of zirconia ceramics are compared. Two ways of obtaining a nanostructure in zirconia ceramics are distinguished: with feedstock represented by nanocrystalline zirconium oxide powder produced by chemical precipitation from chloride salt; two-stage sintering of ceramic half-finished material, which is efficient and available approach to producing materials with controlled size of structural components. The experiments show that the developed method of two-stage sintering of half-finished calcinatories from chemically precipitated nanocrystalline magnesia-stabilized zirconia powders allows production of ceramics with nanostructured nests of tetragonal phase in coarse grains of monoclinic modification. It is revealed that the optimal structure is coarse (to 25–40 μm) grains in the monoclinic modification, with nanosize (25–35 nm) pockets of tetragonal crystalline phase, with open porosity in the range of 7–9 %. It is found that ceramics with optimal structure, thermally resistive in heating to the maximum temperature of 1750–1800 ^oC at a rate of 175 ^oC/min, without splitting and reacting to platinum alloys can be produced in two-stage sintering of calcinatories in the mode of 1700 ^oC for 1 h and 1000 ^oC for 10 h. The created nanostructure is responsible for resistance of ceramics under induction heating at high rates of heating and cooling in smelting of precious metals at 1750–1800 ^oC.

1. Gusev A. I. Nanomaterials, nanostructures, nanotechnologies. Moscow : Fizmatlit, 2007. pp. 13–15.
2. Makarov N. A., Kharitonov D. V., Lemeshev D. O. Physical chemistry of sintering : Teaching aid. Moscow : RKHTU Mendeleeva, 2019. pp. 31–45.
3. Kumagai T. Hot extrusion of nanocrystalline yttria-stabilized tetragonal zirconia polycrystals. Journal of Materials Research. 2016. Vol. 31. Iss. 21. pp. 3290–3302. DOI: 10.1557/jmr.2016.371
4. Li B., Zheng X., Fu Z. F. Fast densification of nanocrystalline yttria ceramics without grain growth. International Journal of Self-Propagating High-Temperature Synthesis. 2015. Vol. 24. pp. 14–20.
5. Vasserman I. M. Chemical precipitation from solutions. Leningrad : Khimiya, 1980. 207 p.
6. Aboras M. M. et al. Effect of sintering temperature on the mechanical properties of nanostructured ceria-zirconia prepared by colloidal process. Advanced Materials Research. 2015. Vol. 1125. pp. 401–405. DOI: 10.4028/www.scientцific.net/AMR.1125.401
7. Reis S. L., Muccillo E. N. S. Two-step sintering of Samaria-doped ceria. Materials Science Forum. 2010. Vol. 660–661. pp. 807–812. DOI: 10.4028/www.scientific.net/MSF.660-661
8. Manosso M. K., Chinelatto A. L., Chinelatto A. S. A., Pallone E. M. D. S. A. Two-steps sintering of alumina-zirconia ceramics. Materials Science Forum. 2010. Vol. 660–661. pp. 819–825. DOI: 10.4028/www.scientific.net/MSF.660-661.819
9. Hui Huang, Bin Wei, Fu-Qiang Zhang et al. Effect of two-step sintering method on properties of zirconia ceramic. West China Journal of Stomatology. 2008. Vol. 26. pp. 175–178.
10. Rajeswari K., Reddy A., Rajasekhar R. et al. Micro structural control of stabilized zirconia ceramics (8YSZ)) through modified conventional sintering methodologies. Science of Sintering. 2010. Vol. 42. pp. 91–97.
11. Wójtowicz B., Pyda W., Labuz A. Monoclinic zirconia sintered bodies prepared via two-step sintering and characterisation of selected mechanical properties. Сeramics Silikáty. 2013. 57, No. 3. pp. 185–189.
12. Morozova L. V., Kalinina M. V., Panova T. I. et al. Synthesis and studies of ZrO₂ – HfO₂ – Y₂O₃ (CeO₂)-based solid solutions. Fizika i khimiya stekla. 2017. Vol. 43, No. 5. pp. 522–530.
13. Khasanov O. L., Dvilis E. S., Bikbaeva Z. G. Methods of compaction and consolidation of nanostructural materials and products. Tomsk : TPU, 2008. 23 p.
14. Ramesh S., Lee S., Tan C. Y. A review on the hydrothermal ageing behaviour of Y-TZP ceramics. Ceramics International. 2018. Vol. 44. pp. 20620–20634.
15. Glymond D., Vick M., Giuliani F., Vandiver L. High-temperature fracture toughness of mullite with monoclinic zirconia. Journal of the American Ceramic Society. 2017. Vol. 100, No. 4. pp. 1570–1577.
16. Korableva E. A., Rusin M. Yu., Savanina N. N. Influence of thermal treatment parameters on properties of composite ZrO₂ – Al₂O₃ ceramic material. Vse materialy. Entsiklopedicheskii spravochnik. 2017. No. 7. pp. 57–64.
17. Vikulin V. V., Yakushkina V. S., Korableva E. A., Dyachenko O. P. Dependence of ionic conductance of solid electrolytes in metallic melts under high temperatures (1500–1800 ^oC) on chemistry and properties of ceramics. Transactions of Regional Contest of Natural Science Projects. 2006. Issue 10. Kaluga : Poligraf-Inform, 2006. pp. 59–67.
18. State Standard GOST 7875.2–2018. Refractory products. Method to determine heat resistance of samples. Effective of 01.04.2019.
19. State Standard GOST 2409–2014. Refractory products. Method to determine apparent density, open and total porosity, water absorption. Effective of 01.09.2015.