Preparation and performance characterization of functionalized boron-based energetic-microcapsules with uniform size

Abstract

Energetic metal and metalloid nano-powders are highly promising as high-energy fuel or energetic additive of propellants. Specifically, boron has extremely high gravimetric and volumetric calorific values. However, the difficulty of ignition, slow combustion and uncomplete energy release limit its application. Herein, we developed an effective strategy to fabricate the functionalized energetic-microcapsules (nB@M−CS) with uniform size (with coefficient of variance lower than 3%) using droplet microfluidic technology, in which the boron nanoparticles (nBs) are uniformly encapsulated in chitosan (CS), with organometallic catalyst (M = Mo, Fe and Co) homogeneously dispersed inside. During combustion, nB@M−CS can overcome the agglomeration of nBs by generating micro-explosion to release and ignite the inner nBs, and the low loading (<2 wt%) and high dispersion of metal catalyst can shorten the mass transfer distance and enhance the contact area between nBs and M catalyst. These can significantly reduce the thermal oxidation temperature and accelerate the combustion rate. Specifically, nB@Mo-CS shows much lower initial oxidation temperature (393 °C) than the previously reported B particles, and exhibits the combustion heat and maximum pressurization rate increased by 114.3% and 7.3 times, respectively, compared with nBs. This work shows the great potential for designing and synthesizing functionalized propellant using microfluidic technology.