纳米铝颗粒在二氧化碳气氛下燃烧的反应分子动力学研究

Molecular Reaction Dynamics Study on Combustion of Aluminum Nanoparticles in Carbon Dioxide Atmosphere

为研究核壳结构纳米铝颗粒(ANP)在CO_(2)气氛下加热与燃烧的过程,采用反应分子动力学方法 (ReaxFF MD)对原子扩散过程进行研究。加热前期,在热膨胀与电场力作用下,核心处的铝原子与壳层的氧原子间相互扩散,在ANP内部形成空腔;加热中后期,ANP在电场力与浓度梯度作用下,转变为均匀分布的亚氧化物(AlO,Al_(2)O等)。分析原子间化学键以及产物数量的变化趋势发现,未氧化的铝原子会抑制一氧化碳的产生。当CO_(2)进入ANP时,发生2Al+CO_(2)=Al_(2)OC+O反应,产生中间产物,游离的O原子优先氧化未反应的铝原子。当铝原子消耗殆尽后,亚氧化物与中间产物分别发生AlO+CO_(2)=AlO2+CO和Al_(2)OC+2AlO2=4AlO+CO反应产生CO。研究揭示了ANP在CO_(2)气氛下加热与燃烧阶段的微观反应机理,为Al/CO_(2)反应体系在火星探测领域的应用提供理论依据。

In order to study the heating and combustion process of core-shell nano-aluminum particles(ANP) in carbon dioxide atmosphere, the atomic diffusion process was studied by reactive molecular dynamics method(ReaxFF MD). In the early stage of heating, under the action of thermal expansion and electric field force, the aluminum atoms in the core and the oxygen atoms in the shell diffused each other, forming a cavity inside the ANP. In the middle and late stage of heating, under the action of electric field force and concentration gradient, the ANP transformed into a uniform distributed sub-oxides(AlO, Al_(2)O etc.). Analysis of the chemical bonds among atoms and the change trend of the number of products found that unoxidized aluminum atoms can inhibit the production of carbon monoxide. When carbon dioxide entered the ANP, the 2Al+CO_(2)=Al_(2)OC+O reaction occurs, resulting in an intermediate product, and the free O atom preferentially oxidizes the unreacted aluminum atom. When the aluminum atoms were exhausted, the sub-oxides and intermediate products undergo the reactions of AlO+CO_(2)=AlO2+CO and Al_(2)OC+2AlO2=4AlO+CO, respectively, to produce carbon monoxide. The study revealed the microscopic reaction mechanism of ANP in the heating and combustion stages of carbon dioxide atmosphere, and provided a theoretical basis for the application of the Al/CO_(2)reaction system in the field of Mars exploration.