Thermal degradation of aluminum formate sol-gel; synthesis of α-alumina and characterization by 1 H, 13 C and 27 Al MAS NMR and XRD spectroscopy

Homogeneous nucleation of corundum nanocrystallites by rapid heating of aluminum formate hydroxide-based precursor powder

“…The broad bands of the precursor powder observed at 9.91, −7.06 and −41.82 ppm could be attributed to octahedral aluminum species (Al VI ). After calcination for 10 s, the bands at −7.06 and −41.82 ppm decreased drastically and new bands were observed at 38.79 and 74.54 ppm which were attributed to pentavalent (Al V ) and tetrahedral (Al IV ) aluminum species, respectively 17 . The bands at 9.91 ppm could be derived from the bidentated bond between aluminum and carboxyl group, while the peaks at −7.06 and −41.82 ppm could be associated with hydrogen bonds between water and aluminum formate 17 .…”

“…After calcination for 10 s, the bands at −7.06 and −41.82 ppm decreased drastically and new bands were observed at 38.79 and 74.54 ppm which were attributed to pentavalent (Al V ) and tetrahedral (Al IV ) aluminum species, respectively 17 . The bands at 9.91 ppm could be derived from the bidentated bond between aluminum and carboxyl group, while the peaks at −7.06 and −41.82 ppm could be associated with hydrogen bonds between water and aluminum formate 17 . From the observation of the band attributed to pentavalent aluminum species (Al V ) not present in crystalline phases 18 , a part of aluminum formate was converted to amorphous alumina by calcination for only 10 s. With increasing the soaking time to 30 s, the bands at −7.06 and −41.82 ppm completely disappeared.…”

A density functional theory study on the structure formation of Al(III) carboxylate complexes in aqueous aluminum sols

“…For example, when the volume ratio of aluminum to formic acid is 1:3, aluminum triformate (Al[O 2 CH] 3 ) could be obtained, which has been proved by using X‐ray diffraction (XRD). [ 42,43 ] Moreover, by using FT‐IR, 13 C and 27 Al magic‐angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, they found that aluminum triformate was a hydrate aluminum formate species, which was composed mainly of the AlO6 structure. Obviously, DFT calculations are in good agreement with these experimental results.…”

“…For example, when the volume ratio of aluminum to formic acid is 1:3, aluminum triformate (Al[O 2 CH] 3 ) could be obtained, which has been proved by using X-ray diffraction (XRD). [42,43] Moreover, by using FT-IR, 13 Figure 5. Due to the presence of coordinating water molecules close to the carboxylate group, the product OH-HCOO-IM3 (OH-CH 3 COO-IM3) may be partially hydrolyzed by this coordinating water molecule to generate the product OH-HCOO-IM5 (OH-CH 3 COO-IM5), and the energy barrier of this hydrolysis process is 88.3 kJÁmol −1 (80.0 kJÁmol −1 ).…”

A facile rout to obtain Al2O3 nanopowder via recycling aluminum cans by sol-gel method

“…The sol-gel method involves the formation of a sol from organometallic precursor, whose suspended particles in sol are polymerized at low temperature, then the produced wet gel is dried and heat treated. Highpurity particles with large surface area can be obtained by sintering ceramic precursors prepared by chemical synthesis and sol-gel methods [15][16][17][18][19][20]. There are only a few reports on the sol-gel and template-free methods for the preparation of γ-alumina mesostructure.…”