Effect of PTFE content on the laser-induced ignition and combustion characteristics of Al@PTFE composite fuels

This paper prepared aluminum@polytetrafluoroethylene (Al@PTFE) composite fuels with different PTFE contents and evaluated the effect of PTFE content on the thermal and combustion characteristics via multiple characterization methods. The scanning electron microscopy (SEM) and thermogravimetry–differential scanning calorimetry (TG-DSC) results showed that the PTFE was well coated on the surface, and the higher the PTFE content, the faster the oxidation reaction rate. Al@PTFE_8% fuel demonstrated more stable thermal performance and higher weight gain. Al@PTFE_15% had a weak endothermic peak at 337.2 °C, while the other two fuels did not appear. The nanosecond pulsed laser-induced plasma ignition (LIPI) test showed that compared to pure Al counterpart, Al@PTFE fuels could effectively shorten the ignition delay and promote the energy release, for Al@PTFE_8% with a reduction of 41.9% in ignition delay and an increase by 17.1 % in combustion temperature. The self-sustaining burn time decreased as the PTFE content increased. The gas-phase combustion of Al@PTFE fuels were more pronounced, and their AlO spectral signal intensity were stronger. The Al@PTFE combustion residues showed lots of cracks and holes, and the mass fraction of O was increased from 22.96 % (Al) to 30.53 % (Al@PTFE_8%). The proposed combustion mechanism reveals that PTFE destroyed the alumina film that hindered combustion, significantly promoting the combustion of Al particles. This study provides guidance for laser-induced plasma ignition of this material under ultrahigh heating rates.