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 nanofiberssthus separating oxidizer and reducing agentsis 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.

The nonlinear optical mechanisms and the optical limiting behavior of porphyrin functionalized detonation nanodiamonds are investigated and compared to the conventional detonation nanodiamonds (DNDs). The optical limiting behavior is characterized by means of nonlinear transmittance, Z-scan, and scattered intensity measurements when submitted to a nanosecond pulsed Nd:YAG laser operating at the second harmonic wavelength. We found that the largest nonlinear attenuation was observed on the 4,4^',4^'',4^'''-(porphyrin-5, 10, 15, 20-tetrayl) tetrakis benzoic acid (PCOOH) suspension. Using Z-scan experiments, it is shown that nonlinear refraction predominates in the unfunctionalized DND suspension, while nonlinear absorption is the most relevant mechanism in the porphyrin functionalized DNDs. Furthermore, a stronger backscattered intensity signal is highlighted for the unfunctionalized DNDs through nonlinear scattering measurements.

The optical limiting behavior of silver nanoparticles with different sizes and shapes is investigated and compared to the optical limiting performance of conventional carbon black suspension (CBS). The optical limiting behavior is characterized by means of nonlinear transmittance and scattered intensity measurements when submitted to nanosecond pulsed Nd:YAG lasers operating at the fundamental or the second harmonic wavelength. We found that the optical limiting effect is strongly particle size dependent and the best performance is achieved with the smaller particles. Moreover, it is shown that the surface plasmon resonance is not the main effect responsible for the nonlinear processes. A theoretical model based on the computation of the Mie scattering functions is exposed, and it is shown that the experimental results can be well explained from the calculations.