Synthesis And Characterization Of Chromates With Novel Morphologies

In this paper, chromates nanostructures with novel controlled morphologies havebeen synthesized by simple solution-phase method and hydrothermal method. Theobtained products were investigated by field emission scanning electron microscopy(FE-SEM), transmission electron microscopy (TEM), and X-ray diffractometer (XRD).The main contents of our work are as follows:1. Hydrothermal synthesis of Cu₁₁(OH)₁₄(CrO₄)₄ nanobeltsCu₁₁(OH)₁₄(CrO₄)₄ nanobelts have been synthesized by hydrothermal method inthe absence of any surfactants. The as-synthesized products are characterized by X-raydiffraction, transmission electron microscopy, and scanning electron microscopy. Theaverage thickness, widths and lengths of the nanobelts are about 15 nm, 30～40 nm, andseveral micrometers, respectively. The influences of the reaction temperature on themorphologies of the resulting products have been investigated. It is interesting thatCu₁₁(OH)₁₄(CrO₄)₄ nanobelts are very sensitive to electron beam illumination. Porousnanobelts are obtained with the electron beam illumination time increased.2. Synthesis and formation mechanism of SrCrO₄ nanobelts by solution-phasemethodSrCrO₄ nanobelts have been successfully synthesized by simple solution-phasemethod at room temperature. The time-dependent formation process of SrCrO₄nanobelts was observed by TV microscopy. When the reaction starts, regular rhombicmicrostructure was formed. As the reaction time increased, rhombic microstructuredisappeared and only SrCrO₄ nanobelts were obtained in the resulting products. 3. Synthesis of CoCrO₄ with various mophologies by solution-phase methodCoCrO₄ with different morphologies have been synthesized by solution-phasemethod in the presence of some suffactant. When CoCl₂ was used as reactant,microparticles with 4μm in diameter were synthesized, which were assembled bygreat number of nanorods with 100 nm in diameter. However, when CoSO₄ take theplace of CoCl₂, some agaric-like microstructures composed of nanosheets weresynthesized. The thickness of the nanosheets is about 20 nm.4. Hydrothermal synthesis of Cr/O₃ doped TiO₂ nanotubesCr₂O₃ doped TiO₂ nanotubes have been successfully prepared by hydrothermalprocess, with 500～600 nm in lengths, 10～20 nm in diameters, and about 4～6 nm inthickness. Compared with pure titanium dioxide, the UV-VIS spectra of Cr₂O₃/TiO₂show the peak is red-shifted clearly in visible-light region.