Effect of Fluoroalkylsilane Surface Functionalization on Boron Combustion.

Boron has been regarded as a promising high-energy fuel due to its high volumetric and gravimetric heating values. However, it remains challenging for boron to attain its theoretical heat of combustion because of the existence of its native boron oxide layer and its high melting and boiling temperatures that delay ignition and inhibit complete combustion. Boron combustion is known to be enhanced by physically adding fluorine-containing chemicals, such as fluoropolymer or metal fluorides, to remove surface boron oxides. Herein, we chemically functionalize the surface of boron particles with three different fluoroalkylsilanes: FPTS-B (F3-B), FOTS-B (F13-B), and FDTS-B (F17-B). We evaluated the ignition and combustion properties of those three functionalized boron particles as well as pristine ones. The boron particles functionalized with the longest fluorocarbon chain (F17) exhibit the most powerful energetic performance, the highest heat of combustion, and the strongest BO2 emission among all samples. These results suggest that the surface functionalization with fluoroalkylsilanes is an efficient strategy to enhance boron ignition and combustion.