Effect of Temperature on Anisotropic Crystal Growth of Boehmite under Hydrothermal Condition

Temperature effect （200-400 ℃） on the anisotropic crystal growth of boehmite under hydrothermal conditions with and without octanoic acid was investigated. The crystallinity and the size of particles increased with increasing the treatment temperature. The crystal growth was facilitated greatly above the critical temperature of water. Although several possible factors could affect the crystal growth behavior, the experimental results were discussed in terms of water properties, such as dielectric constant and viscosity The crystallization was enhanced when the viscosity and dielectric constant of water were low. The viscosity reduction at higher temperature may enhance diffusion and crystallization, in particular, without octanoic acid. The enhancement of crystallization at lower dielectric constant implies that the formation of particles, which are less polar than precursor ions, favorably proceeds in such media. The crystal growth along c-axis showed less temperature dependence around the critical temperature in the experiments with octanoic acid, which suggests that the modification reaction on the （001） surface was also facilitated because the modification reaction forms less polar products. This is probably the reason why the aspect ratio （a/c） was considerably higher for the products obtained with the treatments above the critical temperature.

Hydrothermal Processing,Characterization and Theoretical Calculations of a Copper(Ⅱ) Compound with 1,10-Phenanthroline Derivative Ligand:2-(4-Methoxyphenyl)-1H-imidazo[4,5-f][1,10] Phenanthroline

The metal-organic compound [Cu（MOPIP）2（OH）2] 1（MOPIP = 2-（4-methoxy-phenyl）-1H-imidazo[4,5-f][1,10] phenanthroline） was hydrothermally synthesized and structurally characterized by elemental analysis,Fourier-transformed infrared spectroscopy,thermogravimetric analysis,single-crystal X-ray diffraction and theoretical calculations in Gaussian 03.In the crystal structure,the copper（Cu） atoms are tetra-coordinated with four different nitrogen atoms from two different MOPIP ligands,and the Cu atom is one of the five vertexes of the tetrahedron.Presumably due to the steric bulk of the phenyl ligands,compound 1 adopts a slightly distorted tetrahedral configuration.Moreover,it exhibits a zero-dimensional structure with Cu-MOPIP as the building units.Natural Bond Orbital（NBO） analysis was performed by using the NBO method built in Gaussian 03 Program.The calculation results showed a covalent interaction between the coordinated atoms and Cu（Ⅱ） ion.

Hydrothermal Synthesis and Characterization of Nd Doped One-dimensional Hexagonal CePO_4 Nanowires

One-dimensional Nd doped CePO4 hexagonal nanowires have been synthesized for the first time at 140 ℃ for 24 hours via a hydrothermal method using P123 surfactant as the template.The products were characterized by X-ray diffraction,transmission electron microscopy,photoluminescence and high-resolution transmission electron microscopy.Compared with CePO4,one-dimensional nanomaterials we have synthesized,Nd doped CePO4 nanomaterials remain their hexagonal one-dimensional morphology and smooth surface.However,their photoluminescence emissions are greatly enhanced at the wavelength of 348 nm.With their novel fluorescence-emission property,the Nd doped CePO4 nanomaterials are potential in many fields such as optics and electronics.

Citrate-Mediated Hydrothermal Route to Synthesis A Large-Scale Y_2O_3∶Eu^(3+) Hexangular Prism

Europium-doped yttrium oxide (Y2O3∶Eu3+) hexangular microprisms were synthesized through a citrate-mediated hydrothermal method followed by subsequent calcination. The as-prepared products were characterized by X-Ray Powder Diffractometer (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and fluorescence spectrometer. The sizes of the Y2O3∶Eu3+ hexangular prisms are about 3 μm in rim and 10 μm in length. The citrate additive was found to be responsible for tailoring the crystal growth dynamically: the concentration of hydroxides in solution is reduced via forming citrate-rare earth ion complexes, giving rise to large crystals with perfect facets; the ratio of growth rate of hydroxides along the c-axis and other crystal facets is suppressed, leading to relatively small aspect ratio. The smooth surface and large size led to the luminescence intensity of hexagonal-prism phosphors higher than that of needle-like bundle products obtained without using trisodium citrate additive.

Hydrothermal synthesis of lanthanide(hydr)oxide micro/nanorods in presence of tetrabutylammonium hydroxide

Uniform and well-defined lanthanide hydroxide and oxide micro/nanorods Ln（OH）_3（Ln=La, Pr, Sm, Eu, Gd, Er） and Gd（OH）_3：Eu^（3＋）, Gd_2O_3：Eu^（3＋） were successfully synthesized through a green and facile hydrothermal method. Tetrabutylammonium hydroxide（TBAH） and lanthanide nitrides were used as the hydrothermal precursors without the addition of any templates/surfactants. The products were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, high-resolution transmission electron microscopy（HRTEM） and photoluminescence（PL） spectra. The result demonstrated that lanthanide hydroxide micro/nanorods with 20–80 nm in diameter and 50–450 in length were obtained. The size of the Ln（OH）_3（Ln=La, Pr, Sm, Eu, Gd, Er） rods increased with the increase of the atomic number. The size of the Gd（OH）_3：Eu^（3＋） rods decreased with the increase of p H value by modulating the amount of the TBAH solution. The as-formed product via the hydrothermal process, Gd（OH）_3：Eu^（3＋）, could be transformed to Gd_2O_3：Eu^（3＋） with the same morphology and a slight shrinking in size after a post annealing process. It is a facial method to synthesize photoluminescent nanomaterial of Gd_2O_3：Eu^（3＋）. The Gd_2O_3：Eu^（3＋） microrods exhibited strong red emission corresponding to ~5D）0→~7F_2 transition（610 nm） of Eu^（3＋） under UV light excitation（257 nm）.

Microwave-assisted solvothermal synthesis of ZSM-22 zeolite with controllable crystal lengths

ZSM-22 （TON） zeolite crystal morphology was successfully controlled using a microwave-assisted solvothermal fabrication method. Different co-solvents, including ethanol, 2-propanol, glycerol, and ethylene glycol, were also applied in the synthesis mixture. The effects of various parameters such as the aging time, the type and amount of co-solvent on the ZSM-22 crystal aspect ratio were investigated. When employing this microwave irradiation synthesis, a long aging time was crucial to obtain smaller and more uniform crystal sizes. The addition of co-solvent resulted in elongated ZSM-22 crystals, regard- less of the actual co-solvent used, although ZSM-22 zeolite crystallinity was sensitive to the co-solvent type. In general, the use of a co-solvent stimulated the appearance of ZSM-5 zeolite as an impurity and the amount of this impurity was proportional to the concentration of co-solvent in the synthesis mixture.

Template-free approach for hydrothermal fabrication of ZnO microspheres

Wurtzite ZnO microspheres, 5.5-11 μm in diameter and with smooth surfaces, were prepared in absolute ethanol via a simple template-free method in the presence of ethylenediamine. The products were characterized using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. This simple method to fabricate ZnO microspheres shows high yield （〉90%） and good reproducibiliry. The formation process of ZnO microspheres was discussed. The as-obtained ZnO microspheres are expected to provide some immediate advantages for optical, microelectronic, and biological applications.

Influence of temperature and solution composition on the formation of calcium sulfates

Calcium sulfates （anhydrite and hydrates） were synthesized by mixing CaCl2 and Na2SO4 solutions at room temperature followed by aging the resulting slurries at elevated temperatures. The variation of the morphology and structure of the calcium sulfates with aging temperature was investigated. Experimental results indicated that CaSO4.2H20 plates, CaSO4.0.5H2O whiskers and CaSO4 spindles were formed at 〈100℃, 130-160℃ and 〉170℃, respectively. The formation and conversion of the calcium sulfates were discussed on the basis of characterization of the products and chemical analysis of the solutions. Compared to NaCl solution, pure water favors one-dimensional hydrothermal growth of CaSO4.0.BH2O whiskers owing to lower supersaturation.