A comparative study on the mechanical and reactive behavior of three fluorine-containing thermites

Abstract

Thermite serves as a kind of representative energetic material, which is extensively applied in the civil and military fields. In this paper, PTFE/Al/Fe₂O₃, PTFE/Al/MnO₂ and PTFE/Al/MoO₃, solid fluorine-containing thermite with different PTFE content, were successfully fabricated by referring to the traditional thermite and adding PTFE as a binder or matrix. Quasi-static compression tests were performed to investigate the mechanical and reactive behavior of fluorine-containing thermite. SEM and XRD were employed to analyze and characterize the energetic composites and reaction residuals. The results show that all types of fluorine-containing thermite exhibited different mechanical behavior. PTFE/Al/MnO₂ exhibited the lowest yield strength and strain hardening modulus, but the highest compressive strength and toughness. With the increase of PTFE content, the strength of fluorine-containing thermite improved. No reaction occurred when the PTFE content was 60 vol%, while fluorine-containing thermite with a PTFE content of 80 vol% experienced a severe exothermic reaction under quasi-static compression. The ignition of PTFE/Al/MoO₃ and PTFE/Al/Fe₂O₃ actually attributed to the reaction of Al and PTFE, and the reaction between Al and Fe₂O₃ or MoO₃ was not excited due to the insufficient input energy. The thermite reaction between Al and MnO_2, as well as the reaction of MnO₂ and PTFE, was induced because PTFE/Al/MnO₂ possessed excellent ductility and absorbed the most energy during compression, accompanied with the production of Mn and MnF₂.