Metastable intermixed Core-shell Al@M(IO3)x nanocomposites with improved combustion efficiency by using tannic acid as a functional interfacial layer

Abstract

As is known to all, the nano-aluminum (n-Al) of metastable intermixed composites (MICs) could be easily and slowly oxidized during long-term storage. Herein, a plant polyphenol, tannic acid (TA), has been used to coat n-Al as an interfacial layer to bind with metal iodates (Fe(IO3)3, Cu(IO3)3, Bi(IO3)3) forming MICs with tunable reactivity. The latter can be in-situ synthesized on the surface of TA to construct a core-shell n-Al@TA@M(IO3)x MICs suing a facile, green and low-cost chemical way. Various characterization techniques are used to investigate the prepared these core-shell MICs, including scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermal analysis, bomb calorimetry and high-speed camera. The results showed that the obtained novel MICs were almost monodispersed and uniformly distributed. They have shown enhanced performances in terms of thermal reactivity, long-term storage, energy releases and combustion efficiency. For the thermal reactivity, the major exothermic peak temperature of n-Al@TA@M(IO3)x can be reduced by about 16.9–48.6 °C by using TA as an interfacial layer in comparison with the mechanically mixed n-Al/M(IO3)x. For the long-term storage stability, the energy loss of n-Al@TA@Fe(IO3)3 (11.0%) after three weeks aging is much less than that of n-Al/Fe(IO3)3 (35.3%). For the energy release, Fe(IO3)3-based MICs can be increased to 24.1 kJ cm−3 (14.5% higher), whereas the Cu(IO3)3-based MICs to 22.8 kJ cm−3 (19.4%) and Bi(IO3)3-based MICs to 20.2 kJ cm−3 (3.1%). The burning rates of n-Al@TA@M(IO3)x are 1.7 to 4.3 times higher than that of n-Al/M(IO3)x, and the flame of n-Al@TA@M(IO3)x is more homogeneous than that of n-Al/M(IO3)x.