Speaker
Description
Alumina Al2O3 is a material of high technological importance, and is generally obtained via processes that employ calcination of aluminum hydroxides to achieve full dehydration of these phases. The dehydration of aluminum hydrates is extensively investigated. The underlying atomistic mechanisms are, however, still the subject of a lively debate. Investigation of interfaces between dehydrated phases and their hydrated precursors can be helpful in elucidating reaction pathways. The present study is an investigation of interfaces associated with the gibbsite Al(OH)3 → boehmite AlO(OH) → γ-Al2O3 dehydration sequence, and is intended as a first exploration of possible interface geometries.
Using density functional theory calculations and accounting for van der Waals interactions, four different interfaces between gibbsite and boehmite and boehmite and γ-Al2O3 were investigated. The interface configurations were all found to have a reasonable probability of occurring. H transfer between hydroxyl groups and separation of hydroxyl groups and H atoms from the lattice during relaxation, resulted in the formation of chemisorbed H2O and OH2 groups in gibbsite. In boehmite, the formation of OH2 groups and interstitial H was observed. All interfaces show a transfer of small amounts of charge across the interface. Accumulation of charge in spaces interstitial to the lattice was found to play a role as well. The present study shows the potential of interface studies for elucidating dehydration pathways at the atomic scale, and offers various starting-points for follow-up studies.
H. van Gog, Appl. Surf. Sci. 541 (2021) 148501, https://doi.org/10.1016/j.apsusc.2020.148501.
| Speaker Country | The Netherlands |
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