High-surface-area corundum by mechanochemically induced phase transformation of boehmite

Abstract

In its nanoparticulate form, corundum (α-Al2O3) could lead to several applications. However, its production into nanoparticles (NPs) is greatly hampered by the high activation energy barrier for its formation from cubic close-packed oxides and the sporadic nature of its nucleation. We report a simple synthesis of nanometer-sized α-Al2O3 (particle diameter ~13 nm, surface areas ~140 m2 g−1) by the mechanochemical dehydration of boehmite (γ-AlOOH) at room temperature. This transformation is accompanied by severe microstructural rearrangements and might involve the formation of rare mineral phases, diaspore and tohdite, as intermediates. Thermodynamic calculations indicate that this transformation is driven by the shift in stability from boehmite to α-Al2O3 caused by milling impacts on the surface energy. Structural water in boehmite plays a crucial role in generating and stabilizing α-Al2O3 NPs.

Mechanochemical Synthesis of Catalytic Materials

“…The NPs are synthesized mainly by wet‐chemistry and thermal methods, including precipitation, sol‐gel synthesis, hydrothermal synthesis, spray drying, annealing, and flame pyrolysis, to mention only a few [39, 41] . The mechanochemical route, which is becoming more and more popular, [14–15, 37, 42] already proved to be advantageous over conventional methods as a low‐waste or even waste‐free process. Besides, the availability of high‐energy ball milling devices (see Section 2), which typically have 1000 times higher impact energy than conventional ball mills, enable access to sub‐micrometre to nanometre‐sized solid particles [43–44] .…”

“…Therefore, despite being particularly appealing for catalysis due to their excellent thermal and chemical stability, these forms are not often applied. In contrast, mechanochemical grinding has been shown to provide easy access to the nanoparticulate form of these phases by top‐down (involving comminution and phase transformation) [58] and bottom‐up (e.g., via redox and dehydration reactions induced during grinding) [42] strategies (Figure 2).…”

“… Examples of mechanochemical syntheses of metal oxide nanoparticles by top‐down (involving (a) particle comminution and (b) phase‐transformation), [58–61] and bottom‐up (involving (c) chemical reactions, e.g., redox and dehydration reactions) [42, 62–64] strategies. Atom colours in (b): Ti, green; O, pink.…”

Recent advances in mechanochemical synthesis of mesoporous metal oxides

“…[25][26][27][28] Recently, a facile mechanochemical process, which relied on dehydration of boehmite in a vibration mill afforded a valuable catalyst -corundum with nanoparticle size of ~13 nm and specific surface area (SSA) 6 of ~140 m 2 /g. 29 Elsewhere, a mechanochemical reaction between titanium and cupric oxide conducted for 12 h resulted in the formation of nanocrystalline titanium oxide with an average particle size of ~ 20 nm. 30 Mesoporous nanoparticles of tin oxide were obtained via a simple manual grinding of stannous chloride, ammonium carbonate and glucose followed by calcination at 600 °C.…”

Hierarchical Porous Molybdenum Carbide Based Nanomaterials for Electrocatalytic Hydrogen Production

“…Enriched active sites of sufficient unsaturated Mo and C atoms promote intimate contact between the electrolyte and the electrode material, thereby enhancing catalytic performance (Wang et al, 2019a;Cui et al, 2020). The introduction of a suitable matrix to form a strong coupling toward the catalyst can improve the intrinsic catalytic activity of Mo x C, and also increase the conductivity of the catalyst due to the synergistic effect in the hybrid nanostructure, and hance, finally harvest desired electrochemical performance (Amrute1 et al, 2019;Xiong et al, 2019;Zhao et al, 2019c).…”