Shock-induced thermal behavior of aluminum nanoparticles in propylene oxide

Abstract

The thermal behavior of aluminum nanoparticles reacting with propylene oxide was investigated in normal incident shock waves. Their reactive temperature, which is about 2705±150K, was experimentally determined by the emission strength of AlO. The reactive products were evaluated by x-ray diffraction, which shows that several different phases of Al2O3 are produced in different temperature regions. The scanning electron microscopy image of the reactive products shows that some holes, which were produced in the process of aluminum nanoparticles violently reacting with suboxides of aluminum, are found on the surface of the products. The data of transmission electron microscopy indicate that the grain diameters of the products were within the range of 20–90nm. The geometry of propylene oxide was calculated and optimized using the Rb31yp function and the 6–311+g(d,p) basis set. The calculated results show that the diameter of the molecule is about 0.435nm. The process of vaporizing and condensing of propylene oxide was investigated by electron microscopy, and the results show that the average drop diameter is 4.03μm at t=70s and then is 2.06μm at t=120s. It suggests that the average drop diameters tend to range from several nanometers to tens of nanometers, which is very close to the diameter of aluminum nanoparticles (average of 70nm). Thus, we may consider them to react with each other in the gas phase in normal incident shock waves in the experiment.