Energy Release Characteristics and Reaction Mechanism of PTFE/Al/Bi₂ O₃ Reactive Materials under Drop-Hammer Test

To obtain the influence of the Bi₂ O₃ particle content of a PTFE/Al/Bi₂ O₃ reactive material (later referred to as PAB) on its shock-induced chemical reaction (SICR) characteristics, five kinds of PAB with different Bi₂ O₃ contents were prepared; the reaction process in a drop-hammer test, recorded using a high-speed camera, was analyzed. The ignition and reaction mechanisms of PAB under mechanical impact were analyzed based on the thermochemical reaction characteristics and the microstructure. The results show that with an increase in Bi₂ O₃ content, the shock-induced chemical reaction duration and the sensitivity of PAB increase, and then decrease. When the Bi₂ O₃ content is 9%, the impact sensitivity is the highest and the reaction duration is the longest. The heating at the crack tip is responsible for PAB ignition under long-pulse low-velocity impact. During ignition, PAB undergoes several physicochemical changes such as the melting of PTFE, a PTFE/Bi₂ O₃ reaction, an Al/Bi₂ O₃ reaction, pyrolysis of the melted PTFE, and a C₂ F₄/Al reaction; moreover, the presence of Bi₂ O₃ decreases the excitation threshold of the reactive material, which facilitates the propagation of the reaction and improves the degree of the reaction and overall energy release of the reactive material.