| Calcium titanium oxide nanomaterials have attracted considerable attention due to its low cost, nontoxicity and their potential applicationgs in catalyst control techniques, electric engineering and even biotechnology. Therefore, studies on controllable synthesis, microstructure and properties of calcium titanium oxide nanomaterials should be of great significant to discovering the new phenomena and novel applications.In this disseration, on the basis of the summarized corresponding field, in order to resolve the problems in controllable grwoth of calcium titanum oxides and likely aggregation of photocatalyst, a detailed reasearches on the hydrothermal condition and factors of controllable growth are investigated detailedly. A series of calcium titanium oxides are synthesized by hydrothermal method. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR) spectrometer, UV-visible (UV-vis) spectrophotometer, and atomic force microscope (AFM) are used to study the crystallization behavior, microstructure and properties. The main results are described as follows:Effects of pH values on crystallization and morphology of calcium titanium oxides have been studied. The results show when pH<6, one-dimension (ID) CaTi2O5rod or shuttle-like shape are obtained. When pH=8, two-dimension (2D) CaTi2O4(OH)2nanoflakes are obtained. With increasing pH values at pH>9, the obtained CaTiO3sample changed from three-dimension (3D) CaTiO3aggregated prisms, then to butterfly-like dendrites and cross cubic shapes. The above as-prepared crystals are synthesized via a simple hydrothermal route without surfactants or templates. In addition, the effects of experimental conditions, such as the kind of titanium precursor, Ca/Ti molar ratio and and water/ethanol volume ratio are systematicly investigated on the formation of calcium titanium. The experimental results show that kind of mineralizer and the concentration of strong alaki have a crucial effect on the crystal phase and shape evolution of the samples. The formation mechanisms are proposed for the evolution of phase and morphology.The effect of experimental condition have been studied systematicly on the formation of CaTiO3hierarchical dendrite and microspheric structure composed of nanoflakes. The individual CaTiO3dendrite consists of a long central trunk with symmetry aligned branches, which preferentially grow along<210> directions. The growth mechanisms for CaTiO3hierarchical dendrite and microspheric structure composed of nanoflakes are proposed. Effects of CaTiO3crystals with various morphologies on the optical and photocataltic properties are studied. The results show that CaTiO3butterfly-like dendrite shows high efficient light harvesting since this ordered unit geometry offers a light transfer path for incident light as well as multiple reflective and scattering effects. Moreover, CaTiO3butterfly-like dendrites show exceptional photocatalytic activity due to unique morphology, enhanced light harvesting and large surface area.Pure CaTi2O4(OH)2nanoflake crystals are synthesized via a template-free and surfactant-free hydrothermal process for the first time. The effect of experimental condition such as hydrtothermal temperature, time, solvent kind and water/ethanol molar ratio have been studied systematicly on the formation of CaTi2O4(OH)2nanoflakes. The well-defined nanoflakes are prepared at180℃for36h in a mixed solvent with various molar ratio of400/15-50/10under pH=8-8.3. The nanoflakes with serrated leaf-like have a side length of0.2～0.5μm, a width of0.1～0.2μmn and a height of10～50nm, and the nanoflake grows along the [201] direction. The growth process for CaTi2O4(OH)2nanoflakes is dominated by a crystallization-dissolution-recrystallization growth mechanism. The hydrothermal time plays an important role on the optical properties, photocatalytic properties and electrical properties. The sample prepared at36h shows better optical properties, photocatalytic properties and electrical properties than others shorter than36h. The electrode synthesized from CaTi2O4(OH)2nanoflakes reach specific capacitances of162F g-1at the discharge current of2mA cm-2. It can be attributed to a large surface area and high crystallization and suitable pore size. CaTi2O4(OH)2nanoflakes are calcined at different temperature.When the temperature is low (i.g.≤400℃), CaTi2O4(OH)2nanoflakes are still kept steady indicating that it is stable at room temperature. The formation mechanism of CaTiO3changed from CaTi2O4(OH)2is proposed.Pure and lithium ion doped CaTi2O4(OH)2nanoflakes are prepared by a hydrothermal method without template or surfactant. The results show the electrochemical properties of CaTi2O4(OH)2nanoflakes for lithium-ion batteries are improved by introducing lithium ion. Lio.4CaTi204(OH)2material has demonstrated superior electrochemical performance (e.g. lower initial irreversible loss of11.2%and higher reversible capacity of86%). The improvement of Li0.4CaTi2O4(OH)2sample could be ascribed to the slightly increased lattice constant, large specific surface areas and decreased particle size. |
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