Inducing Oxygen Vacancies to Modulate Ignition Threshold of Nanothermites

Many characteristics of metal oxides are governed by defect chemistry. As a result, defect engineering has become an effective strategy to modulate the electrical, optical, and mechanical properties of metal oxides. As the most commonly used oxidizers in nanothermite systems, metal oxides offer an opportunity to manipulate nanothermite reactions from a fundamental, atomic-scale, defect structure aspect. However, the challenge lies in the complexity of nanothermite reactions that requires shifting defect equilibria without introducing other variations. In this work, we choose a model oxidizer Co3O4 for nonstoichiometry. Utilizing a soft chemistry reduction process, oxygen vacancies are created in Co3O4 with minimal structural disturbance. Ignition threshold is used as a metric to probe the effect of oxygen defects. The results show an inverse correlation between the ignition temperature of Al/Co3O4 nanothermites and oxygen vacancy content in Co3O4. The evolved species analyzed by temperature-jump time-of-flight mass spectrometry (T-jump TOFMS) indicates that the ignition is likely limited by the availability of sufficient gas-phase oxygen species, the production of which can be facilitated by oxygen vacancies.

Automated summary

Defect engineering has become an effective strategy to modulate the properties of metal oxides. In this study, the effect of oxygen defects on the ignition temperature of nanothermite reactions was investigated using Co3O4 as a model oxidizer. Results demonstrated an inverse correlation between the oxygen vacancy content in Co3O4 and the ignition temperature of Al/Co3O4 nanothermites.