α‐Alumina nanospheres from nano‐dispersed boehmite synthesized by a wet chemical route

Abstract

In this work, stable aqueous suspensions of nano-boehmite were developed through a hybrid wet-chemical route that uses hyperbranched dendritic poly(ethylene)imine (PEI) as template material for boehmite formation aiming at the development of a deagglomerated a-alumina nanopowder after calcination. The method involves firstly the interaction between the Al precursor and PEI followed by the hydrolysis and polycondensation reactions. The study was aiming to investigate the effect of solids content and pH during reactions on both the stability of the final suspension and the morphology of the resulting nanocrystals. For this purpose, the suspensions were evaluated through viscosity measurements, zeta potential analyses, FT-IR, DLS and sedimentation studies, whereas after the proper centrifugation, drying, and calcination steps, the as-received nanocrystals were evaluated through SEM, TEM and XRD studies. In addition, the boehmite nanopowder was studied using Thermogravimetric and Differential Thermal Analysis, whereas its sinterability was evaluated by dilatometric measurements. The investigation showed that the conditions employed affect greatly both the morphology of nanocrystals as well as the dispersion and the stability of the suspensions. The boehmite suspension with the optimum dispersion and stability can lead, after calcination at 1050°C, to a fine deagglomerated a-alumina nanopowder with a mean size at about 10 nm. K E Y W O R D S a-alumina, boehmite, dispersion, hyperbranched poly(ethylene)imine, nanoparticles, nanopowder, suspensions

Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

“…Zaki et al also reported cylindrical particles of 100-200 nm in length and less than 25 nm in diameter, yielding 18 m 2 /g for A BET [125]. They used citric acid and acrylic acid in a modified Pechini process, yet obtaining not entirely pure α-Al 2 O 3 particles at 900 • C. Recently, Petrakli et al published a route for the obtention of α-Al 2 O 3 nanospheres < 10 nm from aqueous suspensions of nano-boehmite, stabilized by hyperbranched dendritic poly(ethylene)imine [126]. By calcination at 1050 • C, they attained a specific surface area of 14 m 2 /g in their pure α-Al 2 O 3 powder.…”

Dendritic Polymers as Promising Additives for the Manufacturing of Hybrid Organoceramic Nanocomposites with Ameliorated Properties Suitable for an Extensive Diversity of Applications

“…Amine-terminated dendrimers of various generations constitute exceptional templates that stand out for their similarity to proteins and tunable design that is primarily dictated by the high concentration of well-localized nitrogen functionalities, which resemble the units found in their biological counterparts and are responsible for silica nanospheres production [ 142 ]. For instance, poly(amidoamine) PAMAM and poly(propylene imine) PPI represent popular matrices for the formulation of nanopatterned silica ( Figure 19 ) and alumina ( Figure 20 ) [ 146 ]. The silica ratio of the final aggregated nanoproduct depends highly on the number of amino groups of the selected dendrimer.…”

“… SEM micrographs of alumina nanospheres templated by hyperbranched PEI for different quantities of nano-dispersed boehmite (( a ) 0.02, ( b ) 0.04, ( c ) 0.06, and ( d ) 0.08 g/mL) (Reproduced with permission from [ 146 ]; Copyright The American Ceramic Society, 2018). …”

“…( d ) Self-precipitation in the presence of 3.5 generation PAMAM dendrimer from SBF at pH 8.0. Insets in all figures show typical hydroxyapatite particle shape and morphology under magnification (Reproduced with permission from [ 146 ]; Copyright The American Ceramic Society, 2018).…”

Dendritic Polymers as Promising Additives for the Manufacturing of Hybrid Organoceramic Nanocomposites with Ameliorated Properties Suitable for an Extensive Diversity of Applications

“…Amine terminated dendrimers of various generations constitute exceptional templates that stand out for their similarity to proteins and tunable design that is primarily dictated by the high concentration of well localized nitrogen functionalities, which resemble the units found in their biological counterparts and are responsible for silica nanospheres production [136]. For instance poly(amidoamine) PAMAM and poly(propylene imine) PPI represent popular matrices for the for the formulation of nanopatterned silica ( Figure 19) and alumina ( Figure 20) [140]. The silica ratio of the final aggregated nanoproduct depends highly on the number of amino groups of the selected dendrimer.…”