Spherical Reactive Composite Powders Combining Boron with Polytetrafluoroethylene (PTFE)

Different compositions of boron and polytetrafluoroethylene (PTFE) were prepared using emulsion assisted ball-milling. For each composition, porous spherically-shaped powders were prepared. Additionally, the size and porosity for the same composition powders were tuned selecting the milling parameters. The prepared powders were characterized using scanning electron microscopy. Particle sizes were measured using low-angle laser light scattering. The particle sizes of the prepared powders vary from 5 to 30 µm. Tests related to the reactivity of these powders were performed using Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). With an increase in the amount of fluorinated<br/>additive, PTFE, the temperature at which the onset of mass gain occurs becomes lower. However, the total mass gain at the end of the measurement (at 900 C) is greatest for the neat milled boron with no PTFE added. In DSC, several overlapping exothermic peaks were observed; the peaks shifted to lower temperatures as the concentration of PTFE increased. The strongest exothermic peak was observed for the composite containing 5 wt% PTFE. Prepared powders were placed on top of a flat, electrically heated filament, and their ignition temperatures were measured in air. With increase in the PTFE concentration, the ignition temperature of the composite decreases. Generally, the results suggest that addition of PTFE improves the reactivity of boron.