PRELIMINARY STUDY ON NANOMETER-SCALE GAMMA-ALUMINA POWDER DENSIFICATION THROUGH VIBRATION

摘要

Lightweight, compact hydrogen storage has been one of the major bottlenecks in developing fuel cell systems applicable to powering ground vehicles. In this study, preliminary experimental examinations have been performed to evaluate vibratory densification of nanometer-scale powder particles, which directly affects the volume and weight of storage systems based on complex hydrides such as NaAlH_4. Since NaAlH_4 is is reactive with moisture and oxygen, and thus not possible to test in air, γ-alumina (gamma-aluminum oxide) with a similar average particle size (～50 nm) is applied as a surrogate material in this preliminary investigation. An apparatus including a tube test section to quantify the densification of a column of powder was developed for this study. Comprehensive testing has been carried out to identify the optimal vibration conditions achieving the highest densities. The study investigates the effectiveness of 1-dimensional and 2-dimensional vibration, as well as the impact of frequency patterns (constant frequency and frequency sweeping). Offering fundamental understanding of nano-powder densification using shakers, this experimental investigation provides guidelines for further study of vibration-based hydride powder densification.