Key Engineering Materials Vol. 519

Abstract: La_1-xCa_xMnO₃ (x=0.0-1.0) epitaxial thin films were deposited on both tilted and untilted LaAlO₃ (0 0 1) single crystalline substrates using PLD (pulsed laser deposition) technique, in which the employed qualified polycrystalline La_1-xCa_xMnO₃ targets were synthesized by sol-gel method. The structural properties and the ultraviolet LITV (laser induced thermoelectric voltage) effect of the as-grown films on the tilted substrates were studied. The results demonstrate that the intensities of the LITV signals depend non-monotonously on Ca content, that is, the peak values of the LITV signals firstly increase and then decrease with Ca content increasing. The maximal peak value of LITV was found in the film with Ca=0.33.

Abstract: Lanthanum magnesium hexaaluminate (LaMgAl11O19, LMA) has attracted much interest as its widely used in solid state lasers, TV phosphors and fluorescent lamps. In this paper, LaMgAl11O19 ceramic was pressureless sintered at 1650 °C for 10 h in air atmosphere using LaMgAl11O19 powders prepared by solid-state reaction at 1500 °C for 4 h. The result indicated that the synthesis temperature of LaMgAl11O19 powders was about 1500 °C. The LMA ceramic sample was dense and had a microstructure of platelet-like gains. The excitation spectrum shows two wide bands with the peaks at about 254 nm and 265 nm by monitoring the strongest 362 nm emission, and the emission spectra is consisted of a broad band emission with their peaks near 362 nm with a half-width about 5 nm exciting with 265 nm wavelength.

Abstract: High quality Al2O3 nanoparticles have been successfully synthesized by a simple sol-gel method. Analysis on phase and structure based on x-ray diffraction (XRD) techniques indicate that the as-synthesized samples are well crystallized γ-Al2O3. High-resolution transmission electron microscopy (HRTEM) techniques further confirm a NP is single crystal with size less than 20 nm, the size distribution is uniform as a whole. Raman spectra analysis indicates the vibrational models are in accordance with γ-Al2O3. The density of the obtained γ-Al2O3 nanoparticles material is very small and have a loosen structure, elemental analysis suggests that the nanoparticles are high purity. The as-synthesized γ-Al2O3 material is comparable to the corresponding products that bought abroad in structure, density and purity, and is suitable for energy saving lamps.

Abstract: ZnO-based varistor; Microstructure; design and optimization; Electrical properties Abstract. ZnO-based ceramic varistors of a commercially available ZnO-based varistor composition were prepared under sintering system of different temperatures and dwelling times. The microstructure and electrical properties were investigated systematically and optimized. With increasing sintering temperature from 1035 to 1175 °C and dwelling time from 1 to 4 h, the composition and microstructure phases of the samples almost had no change, but the samples prepared at 1035 and 1175 °C presented the highest porosity; the nonlinear coefficient generally increased, but the samples prepared at 1145 and 1175 °C almost presented the same value of nonlinear coefficient; the varistor voltage decreased; and the samples sintered at 1035 and 1175 °C presented the highest leakage current. From the microstructure and electrical performance, it was proposed that, for the given varistors, the optimum sintering system was 1145 °C for 2 h.

Abstract: Transparent conducting antimony doped tin oxide (ATO) films have been prepared on quartz glass substrate by pulsed laser deposition (PLD) method which is distinctive to maintain the elemental components between the targets and the obtained thin films under optimal conditions. The effect of annealing temperature on the electrical and optical properties of the ATO thin films has been discussed. The annealing treatments have been often employed to reduce the defects and enlarge the grain size for more desirable crystalline structure. As the annealing temperature increases, the ATO thin films exhibited a slightly enhanced crystallinity. Furthermore, annealing treatment can promote both conductivity and transmittance significantly, especially for conductivity. The X-ray photoelectron spectroscopy is used to explore the variation of Sb5+/Sb3+ ratio against the annealing temperature. The optimal resistivity is 2.7×10-3 Ω cm and the average transmittance is about 92% at annealing temperature of 550 oC.

Abstract: In this paper, TiO₂/ ordered mesoporous carbon (CMK-3) composites were prepared by hydrolysis method after electron beam (EB) pretreatment. The XRD results showed pure TiO₂/CMK-3 composites can be obtained under mild reaction conditions (0.06 M TiF₄ solution, and at 60 °C), and the SEM/TEM images showed that the TiO₂ was successfully grown onto the surface of CMK-3. The photocatalytic properties of TiO₂/CMK-3 composites were also investigated by methyl orange (MO) degradation under the UV irradiation. Results demonstrated that the TiO₂/CMK-3 composites have a good photodegradation for the MO.

Abstract: Effects of zinc cations doping into wide band gap semiconductor photocatalysts of electronic structure, visible light response, and photo-absorbed mechanism were studied. A series of Zn-doped NaTaO3 catalysts were prepared by hydrothermal method. XRD results suggested that zinc were successfully doped into the NaTaO3 nanocrystal in the Zn2+ ions state. UV-vis diffuse reflectance spectra indicated no obvious red-shift was observed in the series of zinc doped NaTaO3 photo-catalysts. The simulation of energy band structure by density functional theory unfolded that d orbital of Zn2+ is lower than the Ta 5d and also O 2p orbital, thus it located at the lower energy region of the valence band. Therefore the substitution of Ta5+ ions by Zn2+ ions can not form an intermediate band (IB) between the top of the valence band (VB) and the bottom of conduct band. Meanwhile Zn species can become the recombination centers of photoinduced electrons and holes. Thus, the quickly recombination of e--h+ pairs is one of the most significant factors which deteriorate the photoactivity of Zn-doped NaTaO3

Abstract: Nano-titanium dioxide photocatalyst were prepared under anodizing in the ionic liquid [Bmim ]BF₄, with the Sulfuric acid and water as solvent, groped for the amount of ionic liquid doping in electrolyte. With the help of XRD and SEM technology we characterized the light catalyst that we have prepared. By oxidation degrading LuoDanMing B, we tested its light catalytic activity. The results show that: the best current up time using anodic oxidation method for the preparation of TiO₂/Ti catalyst is 10 min, while the light catalytic activity of the catalyst is the best; the best doping quantity of ionic liquid in electrolyte is 0.5 mL, while the light catalytic activity of the catalyst is the best; in the membrane of the titanium dioxide crystals both Rutile and Anatase are more; the mixed effect of Rutile and Anatase is better. Besides, the membrane surface is rough and porous. Therefore, the catalytic activity is higher.

Abstract: Vacuum glass is a new building material with excellent energy conservation and sound insulation properties. Usually, the spacers between two pieces of flat glass substrates are mini-rings of metal. In the present research, the spacers were prepared with a glass dielectric paste by screen printing, and then sintered till them transparent. The glass dielectric paste for the preparation of transparent spacers of vacuum glass was prepared by using low melting glass powder and terpineol ethyl cellulose solution. The composition of the paste with preferable properties was evaluated as in mass percent: organic vehicle 20-25, and low melting glass powder 73-80. The rheological behaviors of the typical paste were characterized by using an ARES (RFS-III) rheometer. It is found that a weak flocculated network structure is formed in the paste for the high solid filler. The spacers were prepared by screen printing the paste on the glass substrate and then sintered. The transparent, Vickers hardness of the spacers as well as the binder forces between the spacers and the substrate is reported. The reliability of the prepared transparent spacers for the vacuum glass was discussed.

Abstract: Nowadays, nano-material has been greatly developed and successfully applied in many areas, such as information, medicine, energy and consumer goods. Meanwhile, as an important fossil energy, crude oil and its derivatives have been widely used in various aspects of our daily lives. However, along with the increasing difficulties of oil development and the decreasing amount of remaining oil reserve, how to get oil more efficiently and economically has become big challenge to oil industry. Because of its small size and unique multi-function, nano-materials provide many creative solutions to oil industry. For this, what are nano-materials and their key properties are reviewed firstly. Then the current research and applications of nano-materials in oil exploration and production are introduced respectively. Finally, the future trends and potentials of nano-material in oil industry are put forward prospectively.