Reduced-Sensitivity Nanothermites Containing Manganese Oxide Filled Carbon Nanofibers

Nanothermites are versatile pyrotechnic systems composed of a metal oxide and a reducing metal powder, such as aluminum. The high mechanical sensitivity of some of these mixtures (e.g., MnO 2 /Al) makes their handling hazardous. Enclosing the metal oxide inside carbon nanofibers—thus separating oxidizer and reducing agent—is a new way to lower the sensitivity of nanothermites. In this study, we filled herringbone carbon nanofibers (CNF) with manganese oxide MnO x ( x ≈ 1.9) by a two-step opening/filling treatment using nitric acid and molten manganese nitrate, followed by a heat treatment; the resulting nanocomposite is used to prepare a MnO x @CNF/Al nanothermite. A dramatic decrease in the friction sensitivity (threshold >360 N) as compared to a MnO 2 /Al nanothermite (threshold <5 N) is found. The electrostatic discharge sensitivity was also strongly decreased (from 1.0 to 5300 mJ). The combustion was studied by time-resolved cinematography. Analysis of the combustion residues indicates that metallic Mn was formed along with less oxygenated manganese oxides and aluminum carbide. This study shows a new route for the design of safer pyrotechnic systems.