Preparation And Characterization Of One-dimensional Nano-alumina And Alumina Microwires

Recently, well-defined inorganic nanocrystals with a controlled size and shape, especially for 1-D nanostructures, have been a focus of extensive research, due to their unique optical, electrical, and mechanical properties. Because of having less defects in the crystals, the strength and modulus of 1-D alumina and alumina microwires are close to the theoretical value. Furthermore,1-D structure, such as a fibrillar crystalline structure, can minimize the area of contact between primary particles, avoid the occurring of a phase transformation, and suppress the rate of sintering. So, compared with ordinary alumina powder,1-D alumina is an excellent enhancer and catalyst support materials, and is worthy of studying.In this study, alumina with 1-D structures, such as, nanorods, bundles made up of nanorods, and microwires were prepared using hydrothermal and mixed-solvothermal route. The main contents and results are as follows:1,Preparation of one-dimensional alumina from a hydrothermal route using urea as precipitating agent.Bundles of self-assembledγ-AlOOH nanorods were prepared by hydrothermal route using Al(NO3)3 and urea as source materials and various additive (eg. SDSB, CTAB, PVP, NaNO3). XRD, FT-IR, TG/DSC, SEM and TEM analysis techniques were used to characterize the products. The results show that the obtained bundles of self-assembled y-A100H nanorods are uniform with average length about 1.2μm The length and diameter ofγ-AlOOH nanorods is about 560nm and 30nm respectively. When heat-treated at 500℃for 2 hours,γ-Al2O3 nanorods were prepared with the same morphology. The influence of pHfinaie and surfactant on the as-prepared AlOOH nanomaterials'morphology are also been studied.2,Preparation of one-dimensional alumina from a mixed-solvothermal route.One-dimensional (ID) boehmite nanorods with large aspect ratio were successfully synthesized through a template-free mixed-solvothermal route using ethanol and water as mixed solution, AlCl3·6H2O as aluminum source. And the effects of the soaking time on crystallinity and structure of boehmite were investigated. XRD, SEM, TEM and TG/DSC analysis techniques were used to characterize the products. The results show that the obtained willow-leaf-like boehmite nanorods are uniform with average width of 180 nm at the widest point and length up to 1.8μm When heat-treated at 550℃or 4 hours,γ-Al2O3 nanorods were prepared with the same morphology. 3,Preparation of alumina microwires using AACH as a precursor.The AACH precursor fiber were synthesized through hydrothermal method using Al(NO3)3 and urea as source materials and PEG as surfactant. The influence of reaction condition, such as, reactants'concentration, reaction temperature and the use of surfactant, is also been studied. Then the precursor was calcined at different temperature to obtain alumina with various crystal form. XRD, FT-IR, TG/DSC, SEM and TEM analysis techniques were used to characterize the products. Brunauer-Emmett-Teller (BET) gas-sorption measurements were conducted to examine the porous nature ofγ-Al2O3 obtained. The absorption capacity ofγ-Al2O3 to organics were measured by UV-vis spectrometer. The results show that the obtained AACH fibers are uniform with a length from 6 to 12μm and the width from 300 to 500 nm. When heat-treated at 900℃for 2 hours,γ-Al2O3 microwires were prepared with mesoporous structure, having a large surface area, and may be promising candidates for technical applications as catalyst and sorbent. When heat-treated at 1200℃for 2 hours,α-Al2O3 microwires were prepared with favorable dispersibility.