SELF-PROPAGATING HIGH TEMPERATURE SYNTHESIS OF SHAPE MEMORY TITANIUM-NICKEL ALLOYS

Abstract

Introduction This research work is aimed at developing (establishing) an effective
method for synthesizing nitinol alloy (Ni – Ti), a shape memory material using the self-propelled hightemperature synthesis (SHS) process. The synthesis was performed using condensed mixtures composed
of titanium dioxide (TiO₂), nickel oxide (NiO), and magnesium (Mg), where magnesium served as a
reducing agent. The mass fraction of magnesium was varied between 25% and 45% to determine its
impact on combustion characteristics. The results showed that the highest combustion temperature
reached 1845 °C, with a peak propagation velocity of 9.0 mm/s, demonstrating the system’s strong
exothermic nature. Thermogravimetric analysis revealed activation energies of 379.66 kJ/mol and 366.44
kJ/mol as calculated using the Kissinger and Ozawa methods, respectively. These values confirm the
thermodynamic feasibility of the SHS reaction. X-ray diffraction (XRD) analysis identified the presence
of multiple phases, including TiNi, MgO, and Mg₂TiO₄, indicating simultaneous reduction and
intermetallic formation. Scanning electron microscopy (SEM) revealed a porous microstructure with pore
sizes in the range of 50–200 nm, suggesting the suitability of the material for biomedical and sensor
applications. Overall, the research confirms that SHS offers a promising pathway to synthesize porous
NiTi alloys directly from metal oxides, reducing costs and avoiding complex vacuum-based melting
techniques traditionally required in nitinol production.