Key Engineering Materials Vols. 512-515

Abstract: In this paper, we briefly introduce the magnetic fluid; then investigate the distinctive properties of F element; further, describe the exceptional properties of fluorinated surfactant in five aspects; at last, we through formed contact angle analysis the wetting effect of fluorinated surfactant coated on Fe₃O₄ nanoparticles preliminary.

Abstract: Magnetic fluid damper is a kind of shock absorber which based on the principle of second-order buoyancy of magnetic fluid. In this paper, the structure of magnetic fluid damper is analyzed firstly, and then a variety of structural parameters on the damping effect are tested. Focusing on the different gasket angles in the damper, we found that gasket angles play a key role in the damper to influence on the damping effect. A corresponding model is put forward to analyze the inherent reasons.

Abstract: A magnetic fluid damper which based on the principle of second-order buoyancy of magnetic liquid has been presented. During the process of damping, besides the elastic deformation of magnetic liquid adsorbed by permanent magnet, the main ways of energy dissipation are the friction functions, which include the friction between magnets and magnetic liquid, magnetic fluid and magnetic fluid and magnetic fluid and the shell of the damper. In order to investigate influence of magnetic fluid on damping effect, a series of experiments under different magnetic fluid with related parameters including magnetic fluid volume and saturation magnetization are carried out. It is found that both volume and saturation magnetization of magnetic fluid have optimal value on the damping effect of the damper.

Abstract: Highly ordered ZrO2 nanotube (NT) arrays were fabricated by anodization in organic electrolyte containing NH4F. The NTs have an opened porous structure at the top end. A facile electro-deposition technique was used to prepare ZnO quantum dots (QDs) in the pores of the ZrO2 NTs. Characterizations of SEM, XRD, HR-TEM were performed on the NTs. The results confirmed the formation of single-phase wurtzite ZnO nanoparticles in the ZrO2 NTs with a size around 20 nm. Photoluminescence (PL) spectra proved that the ZnO QDs coating had strongly enhanced the PL signal for blue (366nm) and green (503nm) light emissions of the hybrid NT arrays. That maybe arose from structure-dependent defects and oxygen vacancy in the hybrid layers.

Abstract: This paper reports the photoluminescence properties of Ca9Eu1-xSmx(VO4)7 (x=0.2-0.4) synthesized at 1250 oC in air for 12 h using traditional solid-state reaction method. With the increase of Sm3+ substitution amount, purity Ca9Eu1-xSmx(VO4)7 phase was obtained even when the Eu3+ ions were totally substituted by Sm3+. The experimental results showed that when Sm3+ was codoped with Eu3+ into Ca9Eu1-xSmx(VO4)7 crystal structure, Sm3+ would act as a sensitizer and transfer the excitation energy to Eu3+ ions and finally enhance the emission intensity of Ca9Eu1-xSmx(VO4)7 under 405 nm excitation, which leads to more favorite of this kind of phosphor used in UV LED based white LEDs.

Abstract: SrAl₂O₄:Eu²⁺, Dy³⁺ long afterglow phosphors were prepared by combustion synthesis and the influence of PEG dosages of the long afterglow phosphor on the luminescent properties was studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fluorescence spectroscopy (PL) and screen luminance meter. The main phase of the combustion products is SrAl²O⁴ with monoclinic crystal structure and the impurity phase content is reduced by adding PEG. Compared to the phosphor without PEG additive, the emission wavelength of the phosphor does not change, while the intensity of them is obviously enhanced. The optimum content of PEG was 0.4 mol% of the Sr²⁺, and the maximum initial brightness is 19110 mcd/m².

Abstract: The highly uniform spherical Si-based oxynitride core-shell structured phosphors with narrow size distribution and non-aggregation were successfully fabricated by the h-BN protective method for the first time. Firstly, the raw metallic ions (rare earth and alkaline earth ions) were coated on the surface of SiO2 templates via the urea homogeneous precipitation method. Then the core-shell precursor particles were coated with a H3BO3 layer, which was transformed to a h-BN protective film in the reduction condition. At last, the spherical core-shell structured oxynitride phosphors were synthesized through a gas reduction and nitridation method. The as-received phosphors show excellent luminescence properties due to the 4f65d-4f7 transition of Eu2+ under the excitation of UV and blue lights. The homogeneous spherical phosphors are expected to have excellent dispersing and coating properties, which are very important for LED and PDP applications.

Abstract: Transparent conducting films of aluminum-, gallium or tin-doped and undoped zinc oxide were fabricated by dip coating process and post-deposition annealing in reducing gas atmosphere. Films were fabricated using zinc acetate and diethanolamine (stabilizer) with aluminum chloride hexahydrate, gallium chloride or tin (IV) chloride dissolved in ethanol. Dip coating and heating at 600°C in air were repeated ten times before annealing at 600°C in N₂-0.1%H₂. The average film thickness was 240 nm. The average visible transmittance exceeded 80%. Approximately 1 at.% of aluminum- or gallium-doping remarkably increased the carrier electron concentration and lowered the mobility. The lowest resistivity (6.57×10^-3 Ω∙cm) was achieved by doping of 0.8 at.%Al; the carrier electron concentration, the movility and the average visible transmittance were, 3.6×10¹⁹ cm^-3, 28 cm²∙V^-1∙s^-1 and 85%, respectively. Gallium-doping resulted in the lowest resistivity (8.09×10^-3 Ω∙cm) at 1 at.%Ga with the carrier concentration of 2.9×10¹⁹ cm^-3 and the mobility of 25 cm² V^-1 s^-1. Tin doping increased the resistivity. The resistivities, carrier electron concentrations and mobilities were compared with reported values deposited by other deposition process.

Abstract: In this work, titanium films , 500nm thick, are rf sputtered onto glass substrates held at 500°C. The resulting films are then anodized at a constant potential in an electrolyte using a platinum counter electrode. Ti films were synthesized by RF magnetron sputtering on glass substrates. The anodizaton process resulted in the formation of titania nanoarrays. The samples are annealed at different temperature to induce crystallinity. XRD results indicated that the optimal annealing temperature is 500°C, the film is anastasia phases. Atomic force microscope (AFM) show that the microstructure is nanoporous pillar array. The AFM depth is about 21nm. The roughness average (Ra) of films is about 1~3nm. Then the TiO₂ nanoarry film is integrated into DSCs structure, and I-V Characteristic of cell is studied preliminarily.

Abstract: Cadmium sulfide (CdS) nanocrystals (NCs) were self-assembled and in-situ immobilized on the dithiocarbamate (DTCs)-functionalized polyethylene glycol terephthalate (PET) substrates between the organic (carbon disulfide diffused in n-hexane) –aqueous (ethylenediamine and Cd2+ dissolved in water) interface at room temperature. Powder X-ray diffraction measurement revealed the hexagonal structure of CdS nanocrystals. Morphological studies performed by scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) showed the island-like structure of CdS nanocrystals on PET substrates, as well as energy-dispersive X-ray spectroscopy (EDS) confirmed the stoichiometries of CdS nanocrystals. The optical properties of DTCs modified CdS nanocrystals were thoroughly investigated by ultraviolet-visible absorption spectroscopy (UV-vis) and fluorescence spectroscopy. The as-prepared DTCs present intrinsic hydrophobicity and strong affinity for CdS nanocrystals.