Magnetite nanoparticles of Fe3O4 were found to assemble into monodisperse hollow Fe3O4 microspheres with tunable diameters ranging from 200 to 400 nm and open pores on the shells in ethylene glycol in the presence of dodecylamine (DDA). The oriented assembly of nanoparticles conferred the individual hollow Fe3O4 microspheres a remarkable feature of single crystals. The morphologies of the products could be easily manipulated by varying the synthesis parameters. Increasing the concentration of DDA led to an obvious shape evolution of the products from rhombic nanoparticles to hollow microspheres, solid microspheres, and finally irregular nanoparticles, which were mainly attributed to the special self-assembly phenomenon of Fe3O4 nanoparticles in the solvothermal process.
This paper reports on the architectural growth of CaTiO 3 microstructures with regular geometrical morphologies and tunable dimensions under simple solvothermal conditions by using a mixture of ethanol and water as solvent, calcium nitrate and tetrabutyltitanate as starting materials, and NaOH as mineralizer. The microstructures can be divided into tubular and nontubular types, both of which can be further divided into one-, two-, and three-dimensional microstructures. The tubular/ nontubular structures and the dimensions of the microstructures can be achieved by adjusting the initial NaOH concentration and the volume ratio of ethanol to water, respectively. The growth mechanism responsible for the formation of the CaTiO 3 microstructures was investigated. A high-symmetry epitaxial growth process confers regular geometrical morphologies on the CaTiO 3 microstructures: the fast stacking interplay of the {111} planes results in a rectangular structure, and the epitaxial growth limited in the three perpendicular directions forms a perpendicular structure, thus generating the regular geometrical microstructures. The results suggest that highsymmetry epitaxial growth under solvothermal conditions should be a convenient and effective approach for the growth of regular geometrical CaTiO 3 microstructures, which may find importance in many fields.
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