| Hydrothermal synthesis means that the high-temperature, high pressure under some hydroxide in water solubility than the corresponding oxide in the water solubility, so hydroxide precipitates oxides into water at the same time. Hydrothermal Synthesis method has the advantage of being directly generated oxides, to avoid a general liquid phase synthetic methods require oxide calcined into this step, thereby greatly reducing the hardware group and avoid sudden formation. In addition, hydrothermal synthesis of nano-particles also generate a small particle size, narrow particle size distribution, and the advantages of pure ingredients. By use of hydrothermal synthesis of a dimensional nanostructures La2O3 and lanthanum oxide perovskite structure LaMe(Fe, Co, Mn)O3 nano-particles, andα-Fe2O3 coated on La2O3 to form the core-shell structure of nanoparticles which own magnetic and optical properties. It will further expand the scope of the application materials.By assisted of surfactant, we use a simple hydrothermal process to synthesize one dimensional nanostructures lanthanum oxide structure, respectively: nano-needle, nanorods, nanorods cluster. The result of TG/DTA thermal analysis is that the pure lanthanum oxide can be obtained by calcinations at 850℃. the single crystal nature of rod-like La2O3 was showed by the patterns of XRD and SAED. BJH analysis shows that the porous La2O3 possesses a mean pore diameter of 7.9nm, and according to BET analysis, the surface area of the product is 84m2 /g. The porosity materials will provide the opportunities for some potential applications as advanced materials.we observed that the obtained nanorod was of small diameter, and high aspect-ratio (5～15 nm in width and 200～400 nm in length) by TEM. It has been found that the pH values of the micelle solution, reaction time, reaction temperature and the amount of CTAB all play important roles in the formation of La2O3 nanocrystals with various morphologies. Moreover, the mechanism for the morphology control of lanthanum oxide have also been preliminarily presented.La2O3-Fe2O3 composite nano-pseudo-spheres with a core-shell structure were prepared by the hydrothermal process in the presence of cetyltrimethyl-ammonium bromide. x-ray diffraction(XRD), transmission electron microscope(TEM), selected area electron diffraction(SAED), magnetic properties measurement system and UV–vis spectra were employed to characterize the morphology, structure, magnetic properties and performance of optical absorption of the nano-pseudo-spheres materials. The pattern of XRD showed that La2O3 as core had been packed tightly by Fe2O3 as shell. The result of magnetic properties measurement system has a ferromagnetic behavior. Moreover, a rational mechanism is proposed and we also found that the reaction time, reaction temperature play important roles in the formation of core-shell structured La2O3-Fe2O3 nano-pseudo-spheres nanocrystals.Nanosized perovskite LaMe (Fe, Co, Mn) O3 powders were synthesized by a simple hydrothermal process at 100℃for 6 h and further low temperature calcination to crystallize the product. Pure preovskite powers of LaFeO3 and LaCoO3 were formed at thermal treatments as low as 500℃, LaMnO3.15 powers were formed at 650℃. The phase contents and lattice parameters were investigated by X-ray diffraction(XRD). Transmission electron microscope(TEM) investigations were carried out to examine the morphology and average particle size of these powders. The mean particle size was in the nanosale range. The composition and phase structure of obtained samples were showed by XRD. This procedure can be very useful for large scale production of oxides. |
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