粒径大小对高频感应加热制备纳米铝粉活性影响

Effect of Particle Size on Activity of Aluminum Nanopowders Produced by High Frequency Induction Heating

采用高频感应加热蒸发-冷凝法制备了20,25,50 nm三种不同粒度的纳米铝粉,并运用X射线衍射(XRD)和透射电镜(TEM)对纳米铝粉进行表征,使用差热分析(DTA)研究了不同粒径纳米铝粉的热学行为。结果发现,随着纳米粒子粒径从50 nm减小到20 nm,纳米铝粉反应放热热焓从3.721 kJ.g-1减少到0.928 kJ.g-1,即随着粒径的减小纳米铝粉的活性反而变低。认为这是由于铝纳米粒子表面氧化铝膜含量的增加,采用高频感应加热方法制备的粒子不存在内部储能所致。因此,纳米铝粉的活性,不仅取决于粒子的尺寸大小,还取决于粒子的制备方法,以及粒子表面包覆壳层的种类、结构、厚度等。

Three different aluminum nanopowders with mean panicle size of 20 nm,25 nm and 50 nm were synthesized by high frequency induction evaporation condensation method. Structure and morphology of these aluminum nanopowders were characterized by X-ray diffraction （XRD） and transmission electron microscopy （TEM） , and the thermal behaviors of them were studied using differential thermal analysis （DTA）. The results show that the enthalpy change for oxidizing reaction of Al nanopowders is reduced from 3.721 kJ · g^-1 to 0. 928 kJ · g^-1 as Al particle size decreases from 50 nm to 20 nm, so the reactivity of aluminum nanopowders becomes low as the panicle size decreases,which is possibly due to the increase of surface oxide of aluminum nanoparticles and the absence of stored energy in aluminum nanopowders. Therefore,the reactivity of Al nanopowders in air depends on the panicle size, the preparation method,as well as the type,structure and thickness of the surface passivating layer.