Kinetics Simulation Of The Reaction Between Nitromethane And PETN With Al/AlH₃

Adding active metals or hydrides to the energetic materials（EMs）is an effective way to improve their properties.However,the mechanism of interaction between the two is still unclear.The theoretical methods provide safe and flexible conditions for researches.Based on the ReaxFF-lg reactive force field,the initial reaction mechanism,species evolution,energy release and product formation of the following systems were studied:composites of nitromethane（NM）,pentaerythritol tetranitrate（PETN）and nano-aluminum（nano-Al）,nano aluminum hydride（nano-AlH₃）,nano aluminum hydride with oxidized surface（nano-AlH₃[O]）.The main contents of this paper include the following parts:（1）Thermal decomposition of NM/nano-Al composites.The initial decomposition pathway of NM in the NM/nano-Al composites has changed due to the strong adsorption of O atoms by nano-Al.The thermal decomposition of NM/nano-Al can be divided into three stages:adsorption stage,slow decomposition stage,fast decomposition stage.The addition of nano-Al reduces the thermal decomposition temperature and decomposition energy barrier of NM,and increases the energy release.There is an optimal amount of Al contents being added to the NM composite by which the largest total numbers of gaseous products are released.The maximum detonation pressure can be achieved by adding an appropriate amount of nano-Al,which is similar to the experimental results.（2）Thermal decomposition of NM/nano-AlH₃ and NM/nano-AlH₃[O]composites.The addition of nano-AlH₃ accelerates the thermal decomposition of NM,reduces the reaction energy barrier,and increases energy release.The main way of AlH₃ oxidation involves the capture of O atoms from NM.The results show that AlH₃ content and passivated layer affect the oxidation and hydrogen release of AlH₃.The explosion of small particle size AlH₃ leads to rapid oxidation and hydrogen release.The oxidation of AlH₃[O]and large particle size AlH₃ is dominated by the inward and outward diffusion of O and Al atoms,and both formed a hydrogen gas cavity.The final products of NM/nano-AlH₃ composites are H₂O,CO₂,N₂ gases,and Al clusters.（3）Thermal decomposition of PETN/nano-Al,PETN/nano-AlH₃,PETN/nano-AlH₃[O]composites.The effects of the species,particle size and passivation effect of additives on the thermal decomposition mechanism,final product,explosion pressure,and energy release of PETN are studied.The initial decomposition method of PETN is not changed by the addition of nano-Al or nano-AlH₃[O],but is affected by the addition of nano-AlH₃.During the evolution,nano-AlH₃ and nano-AlH₃[O]adsorb a large number of oxygen atoms,and the oxide layer on their surface limits the generation and release of hydrogen.The four additives can all reduce the energy barrier during the thermal decomposition of PETN and increase the energy release,and the three kinds of nano-AlH₃ all have an effect on the total output of the final gaseous product.