Microstructural evolution and mechanical performance of TiO2 nanoparticle-reinforced Fe2O3–Al reactive composites

Abstract

In this study, Fe₂O₃-Al reactive composite samples containing different concentrations of TiO₂ nanoparticles (0.1, 0.2, 0.3, 0.4, and 0.5 wt%) were prepared through ultrasonic mixing followed by thermite combustion in sand molds. Before nanoparticle incorporation, the optimum Fe₂O₃:Al ratio was determined as 3:1, which produced the highest iron yield (116.2 g) with a reaction time of 26.43 s, falling within the industrially desirable range of 23–28 s. X-ray diffraction (XRD) analysis revealed that the base sample primarily consisted of α-Fe and         α-Al₂O₃ phases, while TiO₂-containing samples exhibited additional peaks associated with FeTi and Fe₂Ti intermetallic compounds. Field-emission scanning electron microscopy (FESEM) coupled with energy-dispersive spectroscopy (EDS) confirmed a uniform nanoparticle distribution up to 0.4 wt%, whereas noticeable agglomeration was observed at 0.5 wt%. Mechanical characterization demonstrated that the sample containing 0.4 wt% TiO₂ exhibited the highest density (7.81 g/cm³, corresponding to a 21.7% increase), hardness (293 HV, 36.3% increase), tensile strength (665 MPa, 35.2% increase), and compressive strength (732 MPa, 18.6% increase). Furthermore, the maximum impact energy (265 J, representing a 61.6% increase) and the highest wear resistance (30% reduction in wear depth) were achieved at the same nanoparticle content. The observed improvements are attributed to combined strengthening mechanisms including grain refinement, Orowan strengthening, crack deflection, and thermal mismatch effects.