The interference of ambient oxygen in the solution combustion synthesis of metastable/nonstable compounds is a considerable factor which has been a challenge for synthesizing of such compounds in a single-phase state. Accordingly, evaluation of the amount of oxygen interference in the synthesis process would provide a better insight through the production of metastable compounds using the SCS method. In the current research, iron nitrate-fuel(s) system was selected as the model to estimate the amount of the interference of ambient oxygen in the synthesis process. For this purpose, synthesis of three different compositions of iron oxides i.e. 100 mol % Fe3O4, 80 mol % Fe3O4-20 mol % FeO, and 50 mol % Fe3O4-50 mol % FeO were considered and reaction between iron nitrate and fuel (glycine, urea, and citric acid) was balanced without considering the presence of ambient oxygen in the reactions. Experiments were carried out and obtained powders were characterized by XRD, FTIR, VSM, and SEM analysis. FTIR and XRD results demonstrated that all synthesized powders were multi-phase including Fe3O4 and Fe2O3 phases which indicated the oxidation of product due to the interference of atmospheric oxygen. Based on the quantitative analysis applied to XRD patterns, the amount of ambient oxygen interfered in the synthesis process was calculated. Obtained results demonstrated that the amount of the interference of ambient oxygen is highly influenced by the fuel type. For synthesizing 1 mol product using glycine, urea, and citric acid, the amount of interfered ambient oxygen was 0.25 mol, 0.17 mol, and 0.1 mol, respectively.

Keywords