Comparison of Preparation Methods of Co3O4-Fe2O3 Composite Powder as a Heat Storage Material and Study of its Morphological and Phase Evolution during Redox Reactions

In this study, Co3O4-15 wt. % Fe2O3 composite powder was synthesized by two methods including: A-simultaneous milling of oxide mixtures (0, 1 and 16 h) and B-separately milling of cobalt oxide (0, 1 and 16 h) and iron oxide (0, 0.5 and 7 h) and then mixing. Average particle size, particle morphology, iron oxide distribution, phase analysis, and heat storage capacity were studied by FE-SEM, XRD and thermogravimetry methods. It was found that preparation method has a significant effect on the above-mentioned parameters. The results showed that decreasing of iron oxide particle size and addition of it to cobalt oxide, increase the heat storage capacity of the material relative to as-received cobalt oxide. It was revealed that samples prepared by method A generally had lower heat storage capacity than samples prepared by method B. In addition, it was found that small-scale particle size of the composite may not necessarily improve heat storage capacity of the material, and spinel phase formation (Fe2O3.CoO) also is a key factor that has a great effect on decreasing the heat storage capacity.