Fabrication and combustion behavior of high volumetric energy density core-shell Si/Ta -based nano-energetic composites.

• ECs can enhance the combustion of Si/Ta. • Core-shell structure has some advantages compared with traditional mechanical mixing preparation method. • The reaction mechanism for ECs enhanced Si/Ta combustion was summarized. • Heat release efficiency of the composites could be well tuned by using different content and type of the ECs. This paper reports a group of new energetic materials (EMs) based on Si/Ta coated with recently developed high energetic composites (ECs), such as AP/NC and PVDF/CL-20. These Si/Ta-based nano-energetic composites have been prepared by both mechanical mixing method and an advanced technique of electrostatic self-assembly followed with a spray-drying process. The heat of reaction and combustion behavior of these novel Si/Ta@ECs composites, as well as the morphologies and compositions of their condensed combustion products (CCPs) have been comprehensively studied. It has been shown that the combustion efficiency of Si-Ta could be largely enhanced with the inclusion of two types of ECs. The maximum energy release was 18.39 kJ cm−3 of Si/Ta with the inclusion of ECs prepared by electrostatic self-assembly followed with spray-drying technique, which was 51.6% of the theoretical energy density of the pure Si/Ta and it is about 9.58 kJ cm−3 higher than the mechanically mixed one. It shows that the enhanced flame has improved luminosity and radiation due to increased energy content with higher reaction rate. The maximum flame-front propagation rate and the condensed phase reaction rate of Si/Ta with the addition of 10 wt% of ECs are 30.1 mm s−1 and 120.7 mg s−1, respectively. The maximum combustion wave temperature of Si/Ta-based composite was 2.4 times higher than that of pure Si/Ta without the ECs inclusion. The typical phase composition of the CCPs is composed of TaSi 2 , which is combined with a minor inclusion of Ta 2 O 5 , TaN 0.25 , TaC and Ta 5 Si 3. The two-step reaction mechanism includes the activation and propagation of the fast combustion wave of the ECs and the initiation of the post-burning reaction. [ABSTRACT FROM AUTHOR]