Large-scale and additive-free hydrothermal synthesis of lamellar morphology boehmite

An additive-free hydrothermal approach has been developed for the large-scale synthesis of lamellar morphology boehmite powders by merely using Al(NO3)3 and urea as raw materials conducted in an autoclave of 10 L capacity. The hydrothermal synthetic and calcined products were characterized by techniques of X-ray diffraction(XRD), transmission electronic microscopy(TEM), scanning electron microscope(SEM), Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA/DTA). The microscope analysis manifested that the lamellar boehmite was around 100–200 nm in width and 500–1000 nm in length. The opportune influence factors on boehmite morphology, such as dosage of urea and reaction temperature were determined by single-factor experiment method. To investigate its crystal form and lamellar morphology evolution process, samples subjected to different reaction durations from 2 h to 12 h were prepared and characterized by techniques of TEM, SEM and XRD. A spontaneous morphology evolution mechanism driven by Ostwald ripening was proposed based on the experimental facts.