Preparation and characterization of mechanically activated aluminum/polytetrafluoroethylene composites and their reaction properties in high temperature water steam

Activated aluminum/polytetrafluoroethylene (Al/PTFE) composites were prepared by ball milling method, and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Their reaction properties with the high temperature water steam were systematically studied. The autoignition temperature, delay time to autoignition after igniting of the Al/PTFE composites in the water steam were recorded. Their reaction products with the water steam were observed by SEM, analyzed by XRD, and the residual metal aluminum content in it was obtained through measuring hydrogen production. The experimental results showed that the content of the PTFE was closely related to the size and morphology of the milled particles. Meanwhile, the addition of PTFE significantly promoted the reaction of aluminum with water steam. The samples Al-8%PTFE and Al-10%PTFE exhibited superior combustion properties with the water steam, such as the shorter delay time to autoignition and lower autoignition temperature. Meanwhile, the mechanism of the reaction between Al/PTFE composites and water steam was also discussed. It was suggested that the decomposition products of PTFE in the composites reacted with aluminum and formed AlF₃ firstly, then the AlF₃ immediately reacted with the water steam and formed the Al₂O₃.