Effects of Strain on Activated-Aluminum–Water Reactions

Abstract

Activated aluminum is a fuel source that promises safe hydrogen energy storage with volumetric energy densities twice that of diesel fuel and 45 times that of lithium-ion batteries. Aluminum is activated when liquid eutectic gallium-indium disrupts the aluminum’s passive oxide layer, enabling a reaction with water to release hydrogen gas and heat. This thesis seeks further understanding of this reaction by exploring the effect of residual stresses in the aluminum. Annealing and cold rolling of 1100-alloy aluminum plate developed engineering strain levels up to -0.7. Reactions in both DI water and water with 3.5% NaCl salinity and 0.1M caffeine dopant showed no correlation between hydrogen production and strain but an aggressive acceleration of the reaction with increased strain levels. Some reactions produced unreacted aluminum in the product, most notably for high strain level (-0.4 – -0.6) reactions in DI water. The unreacted products, confirmed to be aluminum by SEM-EDS, fully reacted over 24 hours. Using SEM to inspect the first stages of microstructural reaction mechanisms, higher amounts of exfoliated aluminum were expelled from the bulk at high (-0.6) strain levels compared to unstrained (0.0) samples. These observations further understanding of how strain conditions affect activated aluminum reactions and help delineate ideal operating conditions for reactor design.