Tuning the Reactivity of Metastable Intermixed Composite n-Al/PTFE by Polydopamine Interfacial Control

Abstract

The metastable intermixed composite (MIC) is one of the most popular research topics in the field of energetic materials (EMs). The goal is to invent EMs with tunable reactivity and desired energy content. However, it is very difficult to tune the reactivity of MIC due to its high reactivity and sensitivity caused by enlarged specific surface area and intimate contact between the oxidizers and fuels. Herein, we demonstrated a facile fabrication method that can be used to control the reactivity between the nanoaluminum (n-Al) and poly(tetrafluoroethylene) (PTFE) using an in situ-synthesized polydopamine (PDA) binding layer. It was found that PDA can adhere to both n-Al and PTFE particles, resulting in integrated n-Al@PDA/PTFE MICs. In comparison with traditional n-Al/PTFE MICs, the n-Al@PDA/PTFE showed an increased energy release and reduced sensitivity and more importantly tunable reactivity. By regulating the experimental conditions of coating, the thickness of PDA could be well controlled, which makes the tunable reactivity of n-Al@PDA/PTFE possible. The PDA interfacial layer may increase the preignition reaction (PIR) heat of AlO/PTFE and therefore the overall reaction heat of n-Al/PTFE. It also reveals that the PDA interfacial layer postponed the PIR, leading to an increase in onset thermal decomposition temperature ( T). As T increased, a more complete reaction between PTFE and Al nanoparticles could be achieved.

Tuning the Reactivity of Perfluoropolyether-Functionalized Aluminum Nanoparticles by the Reaction Interface Fuel-Oxidizer Ratio

“…Interestingly, fluorine atoms could decompose the inert Al 2 O 3 shell surrounding the Al NPs into AlF 3 products, producing an exothermic surface reaction that promotes the decomposition of the fluorine-containing oxidizers [ 21 , 22 ]. It has been reported that fluorine-containing oxidizers such as polytetrafluoroethylene (PTFE) [ 23 , 24 ], polyvinylidene fluoride (PVDF) [ 25 , 26 , 27 ], perfluorotetradecanoic acid (PFTD) [ 28 , 29 ], perfluoroalkyl acids (PFAA) [ 30 ], and perfluorohexadecanoic acid (PFHD) [ 31 ] are capable of enhancing the ignition and combustion behavior of Al NPs because of pre-ignition reaction (PIR) which occurs prior to the oxidation reaction of the Al core. However, although the effect of PIR on activating reactivity of Al NPs was demonstrated several years ago [ 32 , 33 ], little attention has been paid to the oxidation mechanism of surface-modification Al NPs regulated by the reaction interface Fuel-Oxidizer ratio.…”

Influence of ceramic particles as additive on the mechanical response and reactive properties of Al/PTFE reactive composites

“…In recent years, extensive research has been conducted on the application of additives in reactive materials to tune the reactivity of composites. 16,17 He et al 18 utilized a synthesized polydopamine binding layer to adjust the reactivity of nanoscale Al/PTFE, where it was found that the mixture of PTFE and nanoscale Al coated with polydopamine showed increased energy release and reduced sensitivity, and more importantly tunable reactivity. In order to improve the strength and density of materials, metal particles are also very common additives, such as W particles.…”

Superhydrophobic Fluorine‐Containing Protective Coating to Endow Al Nanoparticles with Long‐Term Storage Stability and Self‐Activation Reaction Capability

“…In recent years, fluorine‐containing polymers, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and perfluoropolyether (PFPE), have been adopted in Al‐based energetic materials, and it has been shown that Al 2 O 3 shell can react exothermically with the fluoride gas decomposed from the polymers, thus transferring the “dead weight” to an energetic constituent . In this way, the oxidation efficiency is also improved when compared with pure ANPs with a dense surface oxide shell.…”