A novel method for synthesizing well-defined boehmite hollow microspheres

A novel and effective synthesis route has been developed to fabricate γ-AlOOH (boehmite) hollow microspheres (diameter in 1-2μm) with urchin-like shell structures. The external surface of the hollow microspheres was constructed by randomly aggregated and interconnecting nanoplatelets (length in 50nm). The method involves two processes: (1) solid spherical particles can be obtained by an epoxide-driven sol-gel process in several seconds, (2) solid spheres particles transform into urchin-like hollow spheres through chemically induced self-transformation process. Formation of the γ-AlOOH hollow microspheres was strongly dependent on the amount of propylene oxide, the volume ratio of solvents, as well as the kinds of anion. γ-AlOOH hollow microspheres could only be obtained in a particular situation that AlCl₃·6H₂O acts as salt precursor and the volume between H₂O and ethanol were defined as 4ml, 6ml and 6ml, 4ml. In general, the described method is efficient and environmentally benign, and has significant advantages over traditional template approaches to the large-scale production of hollow inorganic materials.