1455 ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2019, Vol. 93, No. 8, pp. 1455–1459. © Pleiades Publishing, Ltd., 2019. Russian Text © The Author(s), 2019, published in Zhurnal Fizicheskoi Khimii, 2019, Vol. 93, No. 8, pp. 1159–1163. Low-Temperature Synthesis of Zirconium Carbonitrode via the Reduction of Zirconia with Magnesium in the Presence of Sodium Carbonate in a Nitrogen Atmosphere R. A. Shishkin a, * and V. S. Kudyakova a a Institute of Physics and Technology, Ural Federal University, Yekaterinburg, 620078 Russia *e-mail: roman.shishkin@urfu.ru Received November 9, 2018; revised November 9, 2018; accepted November 20, 2018 Abstract—Physicochemical transformations that occur during the low-temperature synthesis of zirconium carbonitride via the reduction of zirconia with magnesium in the presence of sodium carbonate in a nitrogen atmosphere are studied. Both reactions leading to the formation of Zr 2 CN and side processes occurring in the charge are studied by means of differential scanning calorimetry. Based in the results, it is concluded that zir- conium carbonitride can be synthesized in the temperature range of 600–675°C. It is shown that using graph- ite does not lead to the formation of zirconium carbide or zirconium carbonitride in the investigated range of temperatures, while the use of urea has hardly any effect on the final product. Keywords: co-reduction, mechanism, zirconium carbonitride, zirconium nitride, sodium carbonate, low- temperature synthesis DOI: 10.1134/S0036024419080272 INTRODUCTION Carbides, nitrides, and carbonitrides of group III– V transition metals are of considerable interest, due to such remarkable physicochemical properties of these materials [1] as high melting temperatures, hardness, chemical resistance, strength, wear resistance, and thermal stability [2, 3]. Zr 2 CN is therefore used as wear-resistant coatings and barrier layers. A number of ways of synthesizing transition metal carbonitrides, particularly zirconium carbonitride, have been developed. These include the pyrolysis of organic precursors [4–6], solvothermal synthesis [7, 8], chemical vapor deposition [9], carbothermal reduction in a nitrogen-containing gas medium [10, 11], and combustion [11, 12]. In recent years, particu- lar attention has been given to means based on the co- reduction of inorganic compounds containing transi- tion metals and alkali or alkaline-earth metal carbon- ates with metallic magnesium [13–15]. However, the possibility of conducting synthesis in a nitrogen-con- taining atmosphere has yet to be explored. The use of this technique would appear to be promising, since it provides both a source of nitrogen and an additional reducing agent. The zirconium carbonitride formation reaction can be written as (1) However, it is still unclear which chemical transforma- tions occur during the co-reduction of zirconia and an alkali metal carbonate with metallic magnesium in a nitrogen-containing atmosphere. Studies of the pro- cesses that occur in the charge will allow us not only to select the optimum temperatures of synthesis, but to abandon the steel autoclaves and long periods of syn- thesis (8–12 h) that are conventionally used in these technologies as well. EXPERIMENTAL The precursors in this work were zirconia (special purity grade 9-2), sodium carbonate (reagent grade), a metallic magnesium powder (MPF-1 stored in kero- sene), powdered graphite (GII-A), and urea (analyti- cal grade). The composition of the four samples is given in Table 1. The samples were placed in an alun- dum crucible and subjected to simultaneous analysis via thermogravimetry and differential scanning calo- rimetry on a Sentsys EVO 1600 unit upon heating to 1200°C in a special purity grade nitrogen atmosphere (99.999%). The resulting product was washed with 0.1 M hydrochloric acid and isopropyl alcohol on a white ribbon filter and then dried at 90°C for 4 h. X-ray diffraction analysis was conducted on an Xpert PRO MRD diffractometer equipped with a ver- tical goniometer and a nickel filter on the secondary beam using CuK α radiation in Bragg–Brentano focus- + + + = + + (g) 2 2 3 2 2 2 2ZrO Na CO 6Mg 0.5N Zr CN 6MgO Na O. CHEMICAL KINETICS AND CATALYSIS