电爆炸法高效制备纳米铝粉中的关键过程及关键影响因素研究

The performance of energetic materials can be significantly improved by aluminum powder additives with particle size of tens of nanometers. At present, the electrical explosion of aluminum wire is the most promising method for large-scale production of aluminum nanopowder. However, it will significantly increase the particle size when using aluminum wire with larger diameter and length in the electrical explosion to improve the production efficiency. In the condensation process of the high temperature supersaturated aluminum vapor produced by electrical explosion of aluminum wire, the particle size is significantly influenced by the vapor temperature, the degree of supersaturation, as well as the diffusion rate and the cooling rate of vapor in the condensation process. The smaller aluminum nanopowder will be formed with the higher vapor temperature and supersaturation degree , as well as the faster diffusion rate and the cooling rate of the vapor. In aluminum wire electrical explosion , the initial temperature and supersaturation degree of the aluminum vapor are determined by specific energy deposition in the resistive stage of explosion and the current value at the explosion time, whereas the diffusion rate and the cooling rate of the vapor are determined by the protective gas and its pressure. Meanwhile, the spatial inhomogeneity of the explosion, the unstability of the specific energy deposition in the resistive stage, and the the secondary discharge plasma in the vapor also have important influences on the particle size . Our proposed project intends to study the influence of the electrical parameters, the protection gas conditions and parameters of aluminum wires on the specific energy and its instability the temperature characteristics, explosion morphology, dispersion characteristics, and the discharge plasma characteristics, as well as the physical mechanisms. On this basis, the method will be determined to increase the specific energy , improve the explosion morphology and dispersion characteristics of the explosion when large-scaled aluminum wire is used in the electrical explosion, and essential criterion of the state parameters in the explosion will be determined to insure the expected particle size of the aluminium nanopowder.

粒径数十纳米的铝粉添加剂可大幅提高含能材料性能，电爆炸法是目前最有希望实现大规模生产的方法。但为提高效率增大丝径和丝长时，会带来粒径显著增大的问题。铝丝电爆炸产生的高温铝蒸气冷凝产生纳米粉体时，蒸气温度和过饱和度越高，冷凝过程的扩散速度和冷却速度越快，越有利于减小纳米粉体粒径。铝丝电爆炸过程中，铝蒸气初始温度和过饱和度与电爆炸过程阻性阶段的比沉积能量和爆炸时刻电流值有关，其扩散速度和冷却速度则与保护气体种类和气压有关，也受爆炸剩余能量的影响。爆炸形态空间不均匀性、沉积能量不稳定性及二次放电等离子体也都对粒径有重要影响。本项目拟就铝丝电爆炸过程中电参数、气体条件和丝参数对铝丝电爆炸比沉积能量及其不稳定性、温度特性、爆炸形态、扩散特性以及放电等离子体特性的影响进行研究，掌握其规律及机制，探索使用大规格铝丝时增加比沉积能量、改善爆炸形态及扩散特性的途径，并确定爆炸过程中物态参数的控制指标。

铝粉作为添加剂在推进剂和高能炸药等含能材料中有广泛的应用，而纳米级的超细铝粉相比微米铝粉对含能材料性能有更显著的提高。金属丝电爆炸(Electrical Explosion of Wires，EEW)是指金属丝在脉冲电流作用下，因焦耳加热产生的沉积能量使其发生剧烈相变，最终成为等离子体，并伴随强光辐射和冲击波等现象的复杂物理过程。在气体氛围中，电爆炸产生的高温蒸汽及等离子体与氛围气体相互作用，最终冷凝成为纳米尺度的超细粉末，具有产物纯度高、粒径分布可控、能量转化效率高等优势，有望成为一种高效率大规模的纳米粉体制备技术。多种实验参数(氛围条件、回路参数、铝丝规格)共同影响电爆炸物理过程，包括阻性阶段能量沉积过程、等离子体空间形态演化过程及形核过程，并最终影响纳米粉体的形貌及粒径分布。目前，实验参数对气氛环境中电爆炸过程及纳米粉体特性的影响规律及影响机制尚不明确，从而限制了其在纳米粉体制备中的应用。针对上述问题，本项目通过电学测量计算获得了比沉积能量、峰值功率、击穿场强、阻抗变化等电学参数，从而获得了气压、外施电压、铝丝规格对电爆炸模式及电学特性的影响规律。通过分幅成像技术，激光阴影、纹影、干涉图像诊断，发射光谱分析等超快光学诊断方法，对电爆炸过程进行光学观测，从而获得了气压、铝丝规格对电爆炸空间形态演化过程、等离子体特性以及扩散特性的影响规律。通过对纳米粉体进行形貌观测及粒径分析，获得了气压、铝丝规格、初始储能等实验参数对纳米粉体特性的影响规律。研究结果对于研究纳米粉体形成的物理过程，为纳米粉体制备的参数优化提供理论依据，具有重要意义；同时对深入理解电爆炸过程的物理过程及机制，以及其在其他领域的应用具有一定的参考价值。