| This disseration is focused on the hydrothermal synthesis ofα-Fe2O3 micro/nanomaterials, including cubic structures, sea urchin-like structures, and capsule-like structures. Investigations are based on several aspects including synthetic procedure, formation mechanism, and the properties for hydrogen storage. The contents comprise hydrothermal synthesis of single crystalline a-Fe2O3 cubes via a surfactant-free method, facile synthesis of sea urchin-like a-Fe2O3 via a simple reaction system, synthesis of capsule-like with the aid of SDS. The effects of concentrations of reagen, the reaction temperature, and the reaction time on the morphologies of products were investigated in detail. The formation mechanism and applications for hydrogen storage were also discussed. This work is not only enriching the iron oxide investigations, but also beneficial to the fundamental research of formation and growth of micro/nanomaterials. The detailed information of the dissertation is listed as follows.Uniform single crystallineα-Fe2O3 cubes were successfully synthesized by hydrothermal reaction with FeCl3·6H2O and CH3COONH4. The size of the hematite cubes can be adjusted in the range of 0.6-3.0μm by using different dosages of the FeCl3 and CH3COONH4 at the hydrothermal temperature of 160 or 180℃for 24 h. The influences of the reactant concentration, reaction temperature, and reaction time on the crystal growth were systematically investigated. The results show that the CH3COONH4 played a crucial role in the system. The formation of cubic hematite in hydrothermal conditions may be due to the complexation between hematite and CH3COO-. The hydrogen storage performance of the as-synthesis hematite was measured on the apparatus composed of a gas flow system with a fixed bed of the samples and a gas detecting system.Monodisperse sea urchin-likeα-Fe2O3 nanostructrues were successfully synthesized through a two-step route in Fe2(SO4)3 solution. First, the sea urchin-like intermediate products were obtained by a hydrothermal method under the temperature of 140℃. Then the products were annealed in air at 500℃for 3h. The effects on reaction temperature, reaction time, the pH of the solution, and the surfactants to the morphologies of hematite in the hydrothermal conditions had been studied. It was found that the SO42- ions played an important role in the formation of sea urchin-like nanostructures. The hydrogen storage performances of the sea urchin-like hematite before and after modified with Mo were investigated.Uniform capsule-like a-Fe2O3 particles with diameter of about 0.4μm and average length up to 1.3μm were synthesized by hydrothermal method with FeCl3, dodecyl sodium sulfate (SDS), and CH3COONa at the hydrothermal temperature of 140℃for 24 h. SDS was used as a soft template to form the capsule-likeα-Fe2O3 particles. The effect of SDS was investigated by varying its concentration. The effect of other surfactants such as CTAB or PVP was also investigated after SDS instead. The results indicated that SDS plays an important role in the formation of capsule-likeα-Fe2O3. The sphere and capsule-likeα-Fe2O3 can be obtained by varying the concentration of the SDS. A possible five-step formation mechanism is presented for the formation of uniform capsule-likeα-Fe2O3.Straw-bundle-like AlOOH (boehmite) nanostructures were successfully synthesized by a hydrothermal method with Al(NO3)3 and CH3COONH4 in the absence of templates at 160℃for 24 h.γ-Al2O3 was obtained by calcining the as-synthesized AlOOH at 600℃for 2 h in air, with the morphology perfectly remainding. The CH3COONH4 reaction system could be provide a strategy to synthesize other metal oxides with new morphologies.Modified iron oxides with double-metal-cation-additive (Fe2O3-Zr-Mo, Fe2O3-Zr-Ni, Fe2O3-Zr-Ce) for hydrogen storage were prepared by an impregnation method using two kinds of Fe2O3 powders with different particle size and different pore diameter as the starting materials. Their performances of hydrogen storage were investigated in detail. The results show that the Fe2O3 powders with larger pore diameter were suitable for being modified with the metal cations by impregnation method. Both of the Zr, Mo-modified samples is the most favorable material for hydrogen storage.
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