THERMODYNAMIC ANALYSIS OF THE SOLUTION SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS OF COPPER AND COPPER OXIDE NANOPARTICLES

Nanostructured copper and its oxides (I) Cu₂O and (II) CuO are the advanced materials for wide application in various fields of industry and engineering. Among a wide range of the existing techniques of their production, the method of the solution self-propagating high-temperature synthesis (SHS-S) is distinguished due to its technical and economic efficiency. It is based on the combustion of a mixture of reagents of highly exothermic oxidation-reduction reactions in a solution. The paper presents the results of the newly conducted thermodynamic analysis of the reaction of an oxidizer - copper nitrate Cu(NO₃)₂ and a reducing agent (fuel) - urea CO(NH₂)₂ dissolved in distilled water. The authors formulated the general stoichiometric equation of an oxidation-reduction reaction and selected the conditions to carry out the thermodynamic analysis. The application of the THERMO computer program allowed calculating the adiabatic temperature and the reaction products compositions depending on the fuel/oxidizer ratio in the reagents mixture determined by the value of known criterion φ and the presence of the external molecular oxygen in the reaction zone; and specifying the conditions of an oxidation-reduction reaction in the mode of volume SCS with the formation of nanoparticles of copper and copper oxides (II) CuO and (I) Cu₂O. In the case of fuel-poor mixtures of reagents ( φ ≤1), the amount of the internal molecular oxygen in the mixture composition is plenty for the complete fuel oxidation and the formation of copper oxide CuO. In the case of the fuel-rich mixtures ( φ ≥1), the existence or absence of the external gaseous oxygen in the reaction zone has the crucial significance: at its stoichiometric content, gaseous medium is an oxidative one and the SHS-S reaction causes the formation of copper oxide CuO; with the absence of the external molecular oxygen, gaseous medium is a reductive one and the SHS-S causes the synthesis of pure copper.

cupric nitrate, urea, overall combustion, thermodynamic analysis, adiabatic temperature, copper, copper oxides