Enhanced-absorption template method for preparation of double-shell NiO hollow nanospheres with controllable particle size for nanothermite application

Abstract

Nanothermite, due to its high energy density, short ignition delay time, and self-sustained exothermic reaction, is attracting wide attention. In this study, an ammonium hydroxide assisted enhanced-absorption carbon microsphere template method is adopted to prepare double-shell NiO hollow nanospheres with controllable particle size, which further are evaluated as the oxidizers in nanothermite. A possible evolutionary process to form the double-shell NiO is described according to the transmission electron microscopy images at different calcination temperature. The thermal and combustion performances of Al/NiO nanothermite are studied by differential scanning calorimetry, electric ignition and constant-volume pressure cell tests. Results show that as the particle size of NiO hollow nanospheres decreases, the nanothermites show lower activation energy, higher heat release, stronger light intensity, shorter ignition delay time and higher pressurization rate. Based on the optical signal, the combustion process is mainly affected by the mass diffusion distance, depending on the gap between the inner and outer layer. These results indicate that Al/NiO nanothermite has excellent ignition and combustion properties, which are very promising for practical applications in microelectromechanical system (MEMS).