Preparation And Characterization Of Alumina Nanoparticles Via Non-aqueous Route

It is very important to prepare Al2O3nanoparticle powders because they have widely applications for their excellent capabilities. Non-aqueous route is a new method to prepare nanomaterials. Nanoparticles with small size, narrow size distribution, and well dispersibility, high quality have been prepared via non-aqueous route. We have prepared the precursor of Al2O3nanoparticle by non-aqueous route, and improved the dispersibility of the precursor by chemical surface-modification method. The Al2O3nanoparticle powders were obtained after heat treatment of the precursor, the phase transformation of the as-prepared precursor, the change of morphology, size and agglomerations of obtained Al2O3nanoparticles were investigated.(1) We used Al(NO3)3·9H2O as the precursor reactant, PVP as surfactant, CH3COONa as hydrolyzing agent, prepared the precursor of Al2O3nanoparticles at180℃and5h via solvothermal method by using ethylene glycol as solvent. Inorganic nanoparticles are easy to agglomerate because their surface are easy to adsorb hydrophilic groups such as-OH and H2O, these groups always form hydrogen bond and hydroxyl bridges between the aluminum hydroxide nanoparticles. We use ethyl acetoacetate as the surface-modification agent, which could replace the-OH groups on the surface of the Al(OH)3nanoparticles, form an hydrophobic layer on its surface, kept apart nanoparticles from each other, and improve the dispersibility of Al(OH)3nanoparticles. The molar ratio of ethyl acetoacetate to aluminum hydroxide was adjusted to prepare a series of surface-modified Al(OH)3nanoparticles, we found by the SEM analysis that the optimal ethyl acetoacetate-to-Al(OH)3molar ratio is0.3:1. The transformation temperature of the ethyl acetoacetate modified Al(OH)3nanoparticles to the stable α-Al2O3is50℃higher than that for the as-prepared and unmodified Al(OH)3nanoparticles, but they shown seriously sintering. FTIR analysis proved that the ethyl acetoacetate molecules are chemically attached to the surface of the Al(OH)3nanoparticles and form a stable surface structure. TGA analysis proved that the weight loss of the ethyl acetoacetate modified Al(OH)3nanoparticle powder is more than that of the as-prepared and unmodified Al(OH)3nanoparticle powder at700℃. The size of the obtained Al2O3nanoparticles have no effect change when the concentration of the reactant Al(NO3)3·9H2O increase from0.01M to0.05M, the size increased and with a broad size distribution when the reactant Al(NO3)3·9H2O increased to0.10M after surface modification and calcination.(2) We obtained the non-aggregated, spherical shape and equiaxial Al(OH)3nanoparticle powders by used Al(NO3)3·9H2O as the precursor reactant, C17H33COONa as hydrolyzing agent, surfactant and template, ethylene glycol as solvent via solvothermal method. The average size of the obtained Al(OH)3nanoparticles increased from41nm to77nm when the concentration of the reactant Al(NO3)3·9H2O increase from0.005M to0.02M. It is proved that the react temperature and time have no effect on the morphology and size of the product nanoparticles. The yield of Al(OH)3is increased when the molar ratio of C17H33COONa and Al(NO3)3·9H2O increasing from0.3:1to1:1; and decreased when the molar ratio increasing from1:1to3:1. It can not obtained product when the molar ratio is3:1. After calcining the obtained precursor Al(OH)3at900℃for2h, γ-Al2O3nanoparticles with spherical shape and porous structure were obtained. The pore size distribution of the γ-Al2O3nanoparticles was measured by the BJH method is between1.8and10nm. SEM and HAADF-STEM analysis proved that the obtained γ-Al2O3nanoparticles were agglormated by small nanoparticles with sizes range2-10nm. α-Al2O3nanoparticles were obtained after calcining the obtained precursor Al(OH)3at1100℃for2h, the particles with smaller size were sintering while large size particles were kept the spherical shape. Furthermore, the formation mechanism of the porous structured Al2O3nanoparticles was discussed.(3) We used Al(NO3)3·9H2O as the precursor reactant, PVP as surfactant, CH3COONa as hydrolyzing agent, prepared the precursor of Al2O3nanoparticles by reflux in ethylene glycol at180℃and5h. It is proved by XRD and SEM that the obtained precursor nanoparticles with an average size of20nm were severe agglomerated, and with amorphous structure. α-Al2O3nanoparticles with small particle size were obtained after calcining the obtained precursor nanoparticles at1100℃for2h. Furthermore, the obtained α-Al2O3nanoparticles show excellent sinterability.