ON THE QUESTION OF THE COEXISTENCE OF NICKEL AND COBALT SPINEL

Abstract

Listen

Translate article

For the development of composite materials based on alumina and high-alumina cements using resource-saving technology when replacing the original raw materials with substandard raw materials and chemical wastes, there is a need for a physical and chemical substantiation of the coexistence of newly formed phases in the composition of the binder, which necessitated the study of the subsolidus structure of the system. The paper presents the results of calculations characterising the elements of the subsolidus structure of the CoO - NiO - Al2O3 system. The results of the study revealed the predominance of solid-phase exchange reactions and determined the structure of the CoO - NiO - Al2O3 system in the subsolidus region. It was found that the sub-solidus structure of the system is simple and consists of three elementary triangles. The analysis of the area of the elementary triangles and the low degree of asymmetry indicate that there are no significant risks of deviation from the specified phase composition of the synthesised materials due to the preparatory technological stages, and no special measures are required during the synthesis of materials to ensure the accuracy of the dosage of the starting ingredients. Based on the results of the calculations, the most thermodynamically stable compound in the studied system (aluminocobalt spinel) was identified, and the maximum probability of its existence was determined. Aluminium-nickel spinel has a lower probability of existence because it does not coexist with CoO and is not represented in the elementary triangle with the maximum area. Aluminium-nickel spinel has a lower probability of existence, and the least likely is the identification of Al2O3 in the composition of heterophase combinations. Based on the results of the study, the geometric-topological and statistical characteristics of the subsolidus structure of the system were analysed, which are important for the accuracy of predicting phase combinations in the synthesis of new heterogeneous composite materials.