Transition alumina nanoparticles and nanorods from boehmite nanoflakes

A new way of synthesizing boehmite (γ-AlOOH) nanoflakes with a specific surface area of 303 m2/g is reported. The phase transformations upon heat treatments from 500 to 1000 °C to transition aluminas (γ-, δ-, θ-alumina) were systematically studied by X-ray diffraction (XRD). The morphologies of nanoparticles and nanorods were revealed by a transmission electron microscope (TEM). The specific surface area, pore size distribution and pore structure of the different transition aluminas at different calcination temperatures were also discussed by the N2 adsorption/desorption test. When calcined from 500 to 800 °C, γ-alumina nanoparticles and nanorods were formed with specific surface areas ranging from 438 to 200 m2/g. At 900 °C, δ- and γ-alumina coexisted with a specific surface area of 124 m2/g, showing morphologies of both nanoparticles and nanorods. At 1000 °C, the sample with morphology of only nanorods was a mixture of θ- and δ-alumina, possibly also γ-alumina with a specific surface area of 79 m2/g.