Unexpected burning rate independence of composite propellants on the pressure by fine interfacial control of fuel/oxidizer

Sponge-like Al/PVDF films with laser sensitivity and high combustion performance prepared by rapid phase inversion

Nano aluminum (Al) has always been the research hotspot in the field of energetic materials because of its high energy density and combustion temperature, and has been considered to be a promising fuel to enhance the energy release of various propulsive systems. In this work, nanocomposite fibers were fabricated by electrospinning technology, in which nano Al and recrystallized cyclotrimethylene trinitramine (RDX) particle were integrated with nitrocellulose (NC) fibers. The agglomeration of nano Al particles in fibers is significantly inhibited. The morphology and chemical components of NC/Al, NC/RDX, and NC/Al/RDX composite fibers were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). The thermal analysis shows that nano NC fibers have lower thermal decomposition temperature (202.1 °C) and apparent activation energy (149.3 kJ mol−1) than raw NC (208.2 °C and 218.5 kJ mol−1), and NC/Al/RDX exhibits improved thermal decomposition properties compared with NC/RDX and NC/Al. The laser ignition experiments suggest that the uniformly dispersed nano Al particles could obviously promote the combustion and shorten ignition delay time. RDX may delay ignition due to its high decomposition temperature, but can significantly enhance the combustion properties of NC/Al/RDX fibers. The combustion propagation velocity of composite fibers is obvious higher than that of its physical mixture. The condensed combustion product is mainly spherical aluminum oxide (Al2O3) with a median diameter of about 180 nm. The reason can be attributed to the intimacy between fuel and oxidizer in composite fibers, which enhances heat and mass transfer. Aluminum with high enthalpy and high combustion temperature is an essential ingredient for improving combustion performance of propellants. In this work, NC based composite fibers containing nano Al were fabricated by electrospinning, which significantly improved laser ignition and combustion performance. The electrospinning technique would also be extended to other composite preparation for broader application beyond the energy materials.

Yanchun Li

Papers

Incorporation of high explosives into nano-aluminum based microspheres to improve reactivity