Study On Hierarchically Structured Nano-alumina:Crystal Structure Regulation And Properties

Due to their unique physical and chemical properties, more and more attentions were paid to nanomaterials, especially the new hierarchical structure ones. In this thesis, a highly opened hierarchical cluster structure nano-alumina was successfully synthesized via a two-step solvothermal route. The influence of synthesis conditions on its morphology and text property was investigated. The chemical properties of nano-alumina with special crystallite orientation were systematically investigated, including the thermal stability, the acidity-alkalinity on the surface and its catalytic performance in methane dry gas reforming reaction.1. Hierarchical cluster nano-alumina was synthesized by a two-step solvothermal reaction but its synthesis conditions were strictly limited. The addition amount of urea, the pH value of the ripening process, the ratio of ethanol/water had a great impact on the morphology of hierarchical cluster structure.2. The morphology evolution and phase transformation of hierarchical cluster structure nano-alumina under different duration time was investigated and a possible mechanism was proposed based on the experiment results. Different organic solvents and precipitation agents greatly affected its morphology. According to the crystallization kinetics, hierarchical cluster structure nano-alumina was drived by an anionic oriented growth mechanism.3. The reasons of deactivation of surfactant in the alcohol-water system and the substances used to regulate crystalline orientation were investigated. Appropriate amount inorganic salts were used to regulate new kinds of sub unit flake crystalline orientation and the samples sustained the hierarchical cluster structure without changing morphology.4. The research was focused on chemical properties of the hierarchical cluster nano-alumina, especially on the properties of its anti-reunion and crystal phase delay shift compared with commercial one. The hierarchical alumina had a good catalytic performance in methane dry gas reforming reaction, which was better than the commercial one.