Key Engineering Materials Vols. 512-515

Abstract: The La₂S₃ microcrystalline were prepared by microwave hydrothermal method (M–H). The influences of different S⁄La molar ratio on the phase composition, and morphology of the La₂S₃ microcrystalline were particularly investigated. The obtained samples were characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet and visible–spectroscopy (UV–vis) and photoluminescence spectroscopy (PL) at room temperature. XRD results show that the decrease of S⁄La molar ratio from 6⁄3 to 6⁄6, the improving in crystallization of the obtained microcrystalline is observed with the decrease in S⁄La molar ratio. The morphology of prepared La₂S₃ transforms from irregular shapes to quasi-sphere structure. The as-prepared microcrystalline show excellent absorbency of ultraviolet light and are almost transparent to visible light to exhibit stable violet-blue photoluminescence properties under the ultraviolet light excitation at room temperature.

Abstract: Lithium trivanadate (LiV₃O₈) powders have many attractive characteristics such as high specific energy density, good rate capacity and long cycle life due to their unique crystal structure and outstanding structure stability as cathode material for rechargeable lithium batteries. LiV₃O₈ crystallites were synthesized under different conditions via a combined ultrasonic irradiation and sol-gel method. The as-prepared LiV₃O₈ powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) absorption spectra. The thermal decomposition process was investigated using thermogravimetric (TG) and differential scanning calorimetry (DSC). The effects of molar ratios of metal ion/citric acid and calcinations temperature on phases and microstructure of the powders were investigated. Results indicate that calcinations temperatures have significant influence on the particle morphology, particle size and particle size distribution of the powders. The pure and rod-like LiV₃O₈ powders with an average size of 0.2-1 μm are obtained at 350 and 400 °C. With the increase of calcinations temperature, the powders exhibit preferred growth orientation along (100) planes. The crystallites obtained at 550 and 600 °C are composed by LiV₃O₈ with a small amount of Li_0.3V₂O₅ phase, both of which exhibit tabular morphologies with an average size of 2-10 μm.

Abstract: La₂CuO₄ crystallites were prepared via a sol-gel process using lanthanum nitrate and cupric nitrate as raw materials, distilled water as solvent, citric acid as complexing agent and ammonia to control the pH value. The as-prepared La₂CuO₄ crystallites were characterized by XRD, FESEM, TEM and UV-Vis spectra. Results show that the crystallization property of La₂CuO₄ crystallites increases firstly and then decreases with increasing of the solution pH value from 1.0 to 2.5, but all of the samples exhibit single sphere-like morphology. It is found that when the solution pH value is controlled at 2.0, the grains display uniform distribution and the size ranges from 100nm to120nm after sintering at 600°C for 2 hours. The optical band gap of the as-prepared La₂CuO₄ crystallites is calculated to be 1.38eV.

Abstract: The hexagonal phase NaYF₄ (Na(Y_1.5Na_0.5)F₆, β-NaYF₄ type) is a kind of ideal host materials for upconversion luminescence with high efficiency. The synthesis of monophase hexagonal NaYF₄:Yb³⁺/Er³⁺ nanoparticles has been investigated by solvothermal processing under 200° for 24hrs. It was found that solvents adopted had a great impact on formation of β-NaYF₄. X-ray diffraction patterns indicated that monophase α-NaYF₄ and β-NaYF₄ nanosized grains could be synthesized successfully under environment of ethanol and oleic acid respectively, whereas the mixture of α-NaYF₄ and Na₅Y₉F₃₂ phases were obtained when water was used as solvent. The synthesized pure β-NaYF₄ nanoparticles were uniformly monodispersed in hexagonal shape with typical length of 150~200nm and diameter of 50~100nm. Selected area electron diffraction observation revealed that the as-prepared nanorods are of single crystalline nature. By co-doping (20%)Yb-(2%)Er, the β-NaYF₄ nanosized grains exhibited bright green upconversion luminescence centered at 538nm under the radiation of near-infrared (NIR) laser(nm). The FTIR spectrum shows theβ-NaYF₄ have the potential of water-solubility for the strong bands at around 3444 and 1634 cm^-1.

Abstract: To improve the dispersion of phthalocyanine blue powder, decrease its consumption and increase the use value of talc, TPBCP (Talc / Phthalocyanine Blue Composite Powder) was prepared by liquid phase mechanochemical method. By means of paint performance test, scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR), the properties and microstructure of composite powder were characterized. The hiding power and oil absorption value of talc/phthalocyanine blue composite powder were 12.88 g/m2 and 32.50 g/100g respectively, and the International Commission on Illumination (CIE) colorimetric data L, a, and b were 44.95, 1.65 and -17.18 respectively. It was equivalent for the hiding power of composite powder to 77.6% of that of pure phthalocyanine blue with a equivalent CIE. The formation of TPBCP was marked by phthalocyanine blue particles uniformly coated on talc surface. The results showed that TPBCP had similar performances with phthalocyanine blue and could instead of phthalocyanine blue to be applied in several fields.

Abstract: The hollow microsphere is a kind of new materials. It has a bright future for its excellent comprehensive performance. This article introduces a high-temperature synthetic technology on the basis of SHS to prepare new hollow ceramic microspheres. Reaction mechanism of hollow ceramic microspheres was studied. Results show that sphere, similar sphere and irregular powders constitute the spraying products. Sphere and similar sphere powders are hollow structure. Besides it also recommend the self-made equipments of collection that adopts three kinds of collections methods of static electricity, water and filter net. The total rate of collection raised above 80%.The effect is good. The hollow microsphere were analyzed through SEM and XRD, the hollow microsphere is regular spheroid or type spheroid.the size of the hollow microsphere is abort Similar. Its diameter is 20 μm or so. The equipments that experiment needs is simple, vivid craft and strong adaptability and respond that raw material and manufacturing circulate cost cheap.

Abstract: Barium ferrites hollow microspheres were prepared by self-propagating high-temperature synthesis self-reactive flame spraying method. The droplets enter in the cooling medium and solidified rapidly so that the gas can not escape to remain holes inside the products. The powder samples were used for characterization. The microstructure and crystal structure were studied by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres. They are spherical or ellipsoidal shapes from nanometer dimension to several micrometers. The phase structure of composite powders is the mixtures of barium ferrite and Fe₂O₃.

Abstract: Zirconium dioxide hollow microspheres were prepared using carbonaceous polysaccharide microspheres as a template through a heterogeneously nucleating wrapping technique. Firstly, carbonaceous microspheres wrapped by ZrO₂ were synthesized, and then the obtained precursor was calcinated at 800°C for 2 hours to remove the template. Based on SEM, TEM and EDS analysis, the microstructure, composition and thermal decomposition process of the precursor as well as the final products were investigated. The formation mechanisms of the core-shell structure precursor and the hollow microspheres were also discussed.

Abstract: The present work used hydrothermal synthesis method utilizing glucose as carbon source to obtain homogeneous nano-sized carbon spheres. The holding time and the concentration of glucose have a remarkable effect on the microstructure of nanometer carbon spheres. When synthesized at a constant temperature and kept the same in the productivity, the lower concentration of glucose or the shorter holding time, the easier to acquired homogeneous and tiny nanometer carbon spheres

Abstract: As anionic surfactant, a commercial salt of lauryl sodium sulfate was used. The effects of different amounts of dispersant on the measurement of particle size distribution between two titanium dioxide powders (anatase and rutile) in aqueous media were discussed. Diluted aqueous suspensions were characterized in terms of particle size distribution and zeta potential. The results demonstrate that the measurement of particle size distribution strongly depends on the amounts of dispersant. The amounts of dispersant have a significant effect on the behavior of the rutile-TiO2 particles. The particle size first decreases significantly with an increase in the amounts of dispersant and then lesser increases with a further increase in the amounts of dispersant. The tendency show significant differences between two particles.