The energy required to ignite micropyretic synthesis. Part I: stable Ni + Al reaction

摘要

The progression of chemical reactions is determined by both thermodynamics and kinetics factors. Micropyretic/combustion reaction is a cascade of many chain chemical reactions and thermodynamics and kinetics of the ignition reaction are expected to greatly affect the overall reaction outcome. Furthermore, the stability of the sequential reaction and its progression are correspondingly changed once micropyretic parameters are changed. Improper ignition of micropyretic reaction provides either excessive or insufficient external energy, thus causes over-heating or extinguishing of the combustion front during propagation and therefore the heterogeneous structures. To achieve the homogeneous micropyretic reaction, it is thought possible to control ignition energy. A numerical study on the correlation of thermodynamics and kinetics factors of ignition on the stable Ni + Al reaction and the required ignition energy is reported in this study. The influences of activation energy (E), enthalpy of the micropyretic reaction (Q), pre-exponential factor (K _o), thermal conductivity (K), heat capacity (C _p ), and thermal activity of the reactants and product, on the temperature/heat loss at the ignition spot and the length of pre-heating zone are respectively studied. It is found that the activation energy and heat capacity have the most significant effects on the ignition energy. The required ignition energy is increased by 44.0% and 23.9%, respectively, when the activation energy and the heat capacity are both increased by 40.0%