Combined experimental and reactive molecular dynamics study on the influence of oxide layer thickness on boron particle ignition and combustion

Boron (B), as a commonly used combustible agent in energetic materials, offers advantages such as high calorific value and combustion products that are free of corrosive or greenhouse gases. However, the oxide layer on the surface of boron powder leads to difficulties in ignition and low combustion efficiency. In this paper, the wet ball milling method with hot acetonitrile as the control agent was used to remove part of the oxide layer on the surface of boron powder, and the pretreated boron powder with high reactivity was obtained. The effect of oxide layer on the combustion performance of amorphous boron particles was analyzed by laser ignition and combustion experiment and thermogravimetric analysis. The experimental results indicate that the ignition delay time of the pretreated boron powder is significantly shortened, and the duration of intense light emission in the combustion process is relatively long. Based on the molecular dynamics calculation method of ReaxFF reactive force field, the ignition and combustion (3500 K) reactions of boron particles with different oxide thickness were studied. The high temperature combustion mechanism of boron particles and the influence of oxide layer on ignition and combustion process were analyzed. The computational results indicate that with the increase of the thickness of the oxide layer, the ignition delay time increases continuously, and the final energy release efficiency of the system decreases. However, when the oxide layer reaches a certain thickness, the change of the ignition delay time tends to stabilize. For the combustion reaction process of boron particles, the combustion dynamics model of amorphous boron particles was established, and the multi-stage reaction characteristics of boron particle combustion were revealed: initial reaction stage (∼1900 K), ignition combustion stage (1900 ∼ 3500 K) and continuous combustion stage (3500 K). In this paper, the mechanism of ignition and combustion reaction of boron particles is explored by combining experiments and calculation methods, which provides a theoretical basis for the development of application technology of boron metal fuel in energetic materials.