Aging behavior of aluminum nanopowders: accelerated aging experiments and modeling of the influence of temperature and humidity on the aluminum content

A quantitative study on the aging behavior of aluminum nanopowders is presented. While previous studies in literature focused on a few conditions of temperature and/or humidity, towards an understanding of the physical process behind the aging, no study investigated yet sufficient conditions to develop an accelerated aging model specific to aluminum nanopowders. This study investigated aluminum nanopowders obtained by plasma electro-condensation, submitted to a range of 11 conditions of humidity (25 to 75%) and temperature (298 to 348 K) over periods of 1 h to 71 days. Apart from the storage time in the climatic chamber, the powders were stored in a low-oxygen and low-humidity glovebox to prevent the influence of natural aging. The powders were then analyzed through thermo-gravimetric analysis (TGA) combined with differential scanning calorimetry (DSC) to retrieve the aluminum content as well as the humidity content. The decrease in aluminum content over time for each storage condition was then modeled with a power law. Finally, the fitting coefficients determined from the power law were used to build an accelerated aging model taking into account temperature and humidity effects, and that can predict the oxidation due to natural aging. Furthermore, the activation energy of the aging process determined through the model can also be used in the accelerated aging model of Bohn with a similar F coefficient.