Hydrogen generation by the reaction of mechanochemically activated aluminium and water
Du Preez, Stephanus Petrus
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This dissertation presents a method to generate on-demand and pure hydrogen from neutral pH water using a hydrolysing material, i.e. mechanochemically activated aluminium (Al), under standard ambient conditions. The individual and combined effects of the considered activation compounds, i.e. bismuth (Bi), indium (In), and tin (Sn), on Al during mechanochemical processing were evaluated. Of importance in this study were i) composite hydrolysis reactivity towards water, ii) the effects of activation compounds on Al particle behaviour during mechanochemical activation, i.e. cold-welding, strain hardening, fracturing, and iii) the distribution of activation compounds in Al particles. Several activation compound combinations were considered for investigation, i.e. Bi-In-Sn, Bi-In, Sn-In and Bi- Sn. SEM and EDS analyses were applied to determine particle morphology and surface/subsurface chemical compositions of Al particles pre- and post mechanochemical activation procedures. Scanning electron microscopy (SEM) energy dispersive x-ray spectrometer (EDS) results presented in this study suggests that the considered activation compounds could be distributed relatively homogeneously throughout Al particles by mechanochemical activation. Such a distribution promoted micro-galvanic activity between anodic Al and cathodic Bi, In, and Sn. X-ray diffraction indicated various intermetallic phase formation between Al-activation compound and activation compound-activation compound. These phases formed as a result of mechanochemical activation and in some cases affected the structural failure and/or reactivity of Al particles. Numerous high hydrogen yielding (>95%) composites were prepared. Furthermore, a preliminary method to recover activation compounds from hydrolysed Al using common acids was proposed.
- Engineering