金属化含能材料中金属自钝化及界面反应机理研究

After the high activity magnesium and aluminum are added in the energetic materials, their detonation temperature, explosion pressure and explosion heat effect are greatly improved. However the magnesium and aluminum in the air is extremely prone to self-passivation and informing the thick and compact oxide layer, these oxide layers can reduce the metal activity and inhibit the deflagration reaction of the metal with the energetic materials, which affects the efficiency of energy release. This project focuses on the composite systems of metallized energetic materials with Mg, Al and RDX, HMX. The research techniques mainly include the quantum mechanics method and molecular simulation technology. The research contents mainly include: the mechanism of the metal self-passivation; the mechanism of interface reaction of the energetic materials and their decomposed products (H2O, COx and NOx, et al) on the surface of the metals and their passivation layers, including the path of the interfacial reaction, the rate determing step, the activation energy, the primary and secondary reaction and the product distribution; the crystal boundary, the crystal hole and tropical insulation of the defective crystals of magnesium and aluminum covered with passivation layers. It will be constructed that the interacting-potential-function of the gas-solid, liquid-solid and gas-liquid was in the metal-containing energetic materials. Their force-field parameters are optimized at the micro-scale to simulate the process of the adsorption and diffusion about the energetic materials and their decomposed products on the metal passivation layers, and the adsorption-energy, the adsorption-quantity, the diffusion-path, diffusion-coefficient and diffusion-activation-energy will be obtained. The regularity of metal self-passivation and the mechanism of the interface reaction for the energetic materials on the surface of the metals and their passivation layers will be revealed to provide the scientific theory basis for improving metal reaction activity.

含能材料加入高活性金属镁、铝后，其爆温、爆压及爆热效应均大为提高。但金属镁、铝在空气中极易发生自钝化，所形成的厚密氧化层会降低金属有效活性并抑制其与含能材料的爆燃反应，影响其能量释放效率。本项目以金属镁、铝与RDX、HMX所构成的金属化含能材料为研究对象,采用量子力学方法和分子模拟技术，研究金属自钝化历程、含能材料及其分解产物(H2O、COx和NOx等)在金属及其钝化层上的界面反应机理,即界面反应的路径、决速步骤、活化能、主次反应、产物分布；研究有缺陷的镁、铝晶体及表面覆盖钝化层的晶界、晶孔、绝热带等。构建金属化含能材料中气-固、液-固、气-液相互作用势并优化其力场参数，以此模拟含能材料及其分解产物在金属钝化层上的吸附和扩散过程，研究吸附能、吸附量及其扩散的路径、系数和活化能。揭示金属自钝化规律和含能材料在金属及其钝化层上的微观反应机理，为提高其反应活性提供科学依据。

金属化含能材料中的高活性镁、铝极易与氧气、水、碳氧化物、氮氧化物等氧化剂反应形成“自钝化”效应影响其总能量的释放。本项目运用量子化学方法在原子-分子水平上，对镁、铝等金属的自钝化效应及其与黑索金(RDX)、奥克托今(HMX)等含能材料及其分解产物(如水、碳氧化物、氮氧化物等)和周围介质(如氧气)的界面反应机理进行研究，探索出影响镁、铝高能金属在含能材料中能量释放的效率问题，获得了实验条件下难以测得的数据，解决了金属镁铝在含能材料中释放能量的限度问题，揭示了微观尺度下金属化含能材料中界面作用的本质，为高活性金属镁铝在含能材料领域的应用提供科学理论依据。.(1) 运用GGA/PBE密度泛函方法，研究了氧原子和氧分子在Al(111)表面的吸附。氧原子在表层的最稳定吸附位为fcc位。当铝表面氧原子覆盖度增大时，其氧分子的物理吸附热也随之增大，而氧分子的解离吸附热先减小后增大。当覆盖度为1.00ML时，氧分子不发生解离，只发生物理吸附。随着表层氧原子覆盖度增大，氧原子层内扩散和层间扩散的能垒整体上也都随之增大，且层间扩散要相较层内扩散容易。Al(111)表面极易吸附氧分子，即使氧分子与铝表面的距离较大时，氧分子也可以自动吸附并解离。.(2) 运用密度泛函理论研究CO分子在Al(111)表面的吸附。揭示了Al(111)表面吸附CO的特性随覆盖度变化的规律。CO的稳定吸附位为六方堆积位(hcp)；CO分子与表面铝原子作用中电荷转移发生在C与Al原子的价电子间；CO分子的4σ、1π和5σ轨道上有电子转移至Al表面，从而在C原子和Al原子间形成化学键，而2π轨道得到了来自Al的反馈电子，导致反键轨道2π轨道部分填充，使C-O键被削弱，键长变长。CO分子在Al(111)表面的吸附作用使CO分子活化，同时使Al钝化。.(3) 用分子动力学方法研究了NH2NO2分子在Al(111)表面的扩散、结合能和径向分布函数。在低温下NH2NO2分子吸附在Al(111)表面上，在高温下NH2NO2分子在Al(111)表面上发生了扩散，并且表面Al原子也偏离了原来位置。扩散速率随着温度升高而增大，在450 K温度以下，随着压强增大先减小后增大。在250 K和0.1 GPa下，自扩散系数(Ds)最小，为0.85×10-6 cm2•s-1；在550K和 1.0 GPa下，自扩散系数(Ds)最大，为123.1