Materials Science Forum Vols. 663-665

Abstract: This paper studied the low temperature co-fired ceramic (LTCC) powders based on BaOTiO2- B2O3-SiO2 glass-ceramics that is coated with Al2O3 using co-precipitation process. The Al2O3 coating is made from aluminum isopropoxide precursor solutions. Atomic Absorption spectrometer and TEM methods are employed in this experiment. After calcinations, the alumina coating is strongly adhered to the LTCC particles’ surface. The Al2O3 coating is able to prevent soluble Ba2+ from dissolving in water and the effect grows with the increasing mass fraction of aluminum isopropoxide precursor in the co-precipitation system. The optimum mass fraction of alumina isopropoxide coating precursor is about 6wt%.

Abstract: As solar energy is inexhaustible, solar cells have become one of the options to the future energy. The raw material silicon as one of the Earth's most abundant resources elements, have the advantage of non-toxic, no pollution, no radiation, high photoelectric conversion efficiency, stability and reliability of optical performance become the main raw material for production of solar cells. Because of its supply is limited, We used relatively inexpensive metallurgical grade silicon as a starting material to produce solar grade silicon for solar cells is considered relatively inexpensive method. Therefore, the removal of impurities from metal silicon witch reduce solar cell carrier lifetime and thus reducing its power generation efficiency is a significant issue. To this end, according to impurities in molten silicon and solid silicon demonstrated various characteristics and existence forms, in this paper we used acid leaching, directional solidification, electron and magnetic field, vacuum melting, blow reactive gases and so on to fabricate solar grade silicon from metal silicon in theory to analyze and optimize process.

Abstract: This paper describes a theoretical and experimental analysis on full-filed stress distribution from thermoelastic measurements and its application to determination of stress concentration. The sum of the principle stress can be measured by Thermal Stress Analysis (TSA). Lock-in Thermography is very effective tool to measure the structure stress distribution by its high thermal resolving. In this study, the thermoelastic effect theory is described and the relationship between the temperature and the applied stress is developed in an elastic material. Experiments were carried out with 2A12 aluminium alloys plate and ones with hole structure under cyclic load. The thermoelastic effect coefficient is obtained for 2A12 aluminium alloys materials, and the effect law is analyzed that the stress value measured was affected by load frequencies. The optional load frequency is obtained, and that is, the load frequency is selected greater than 3.5Hz for 2Al12 materilas, and it was found that the structure stress can be evaluated with good accuracies by the lock in thermography. The experiment was carried out for aircraft components stress distribution measurement and structure stress analysis. The experimental results show the stress concentration position is easy found from stress distribution by lock-in thermography.

Abstract: The pyramid-like textured ZnO film was prepared directly by magnetron sputtering on the self-supporting substrate of ZnO:Al film fabricated by sol-gel. The performance of amorphous silicon solar cell has been studied using the textured ZnO film as a front electrode. It was found that: (1) using the textured ZnO film as an amorphous silicon solar cell front electrode, it can be improved the open voltage, but the fill factor and conversion efficiency was depraved; and (2) inserting a protocrystalline silicon buffer layer between ZnO and p-a-SiC:H, the performance of solar cell was improved obviously. For example, its conversion efficiency increases from 7.3% for the SnO2: FTCO to 7.9% for the ZnO/pc-Si:H TCO.

Abstract: Zn1-xCoxO magnetic microspheres have been synthesized by a simple solvothermal process. Different Co2+ dopant concentrations have been used as modifier and proved to be efficient at controlling the morphology and magnetic property of Zn1-xCoxO microspheres. The as-synthesized samples are characterized by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, photoluminescence spectrophotometer and vibrating sample magnetometry. Magnetic hysteresis loops reveal the samples exhibit ferromagnetic loops at room temperature. The meta-saturation magnetization value and coercivity of Zn0.8Co0.2O reach 0.09 emu·g-1 and 15.0 Oe.

Abstract: A new process was developed for fabrication of multiferroic 1-3 type nanostructured composite films. In this process, eletrodeposition method was adopted to prepare the arrays of cobalt nanowires as ferromagnetic composition. The images, phase structure and magnetic properties were characterized by SEM, XRD and VSM, respectively. The results showed that applying magnetic field during electrodepostion process could improve the alignment and height uniformity of nanowires arrays, inducing (002)-orientation growth. The PZT (53/47) precursor solution prepared for ferroelectric composition was infiltrated the spaces between nanowires. After annealed at 700 °C for 20 min, the 1-3 type multiferroic composite film was achieved. Preliminary results show this technique to have the potential to become a practical fabrication process for 1-3 type multiferroic composite films.

Abstract: Silver myristate/AgBr composite particles were prepared by using silver nitrate, sodium hydroxide, myristic acid, and sodium bromide as raw materials and PVP as surfactant in water-alcohol system and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), ultraviolet-visible spectroscopy (UV) and differential scanning calorimetry (DSC). The results showed that silver myristate/AgBr composite particles are composed of rod-like silver myristate grains with a layer structure and small silver bromide particles formed on the surface of silver myristate. Silver bromide can extend the ultraviolet absorbance range of silver myristate. The size of silver myristate is about 260nm and the average size of silver bromide is about 44nm. TG and DSC analysis showed that the reaction was carried out completely. The composite particles start to decompose at about 210oC. Silver bromide of the composite particles melts at 418.2oC.

Abstract: A modified rod in tube technique for tellurite glass preform fabrication is reported, and the effects of the fabrication process on the preform quality are discussed in terms of different processing factors. The conditions for obtaining good quality of reproducible preforms were experimentally investigated. Preforms with a good interface between core and cladding were obtained by this technique, then drawn to fiber.

Abstract: The nano-Co/Ce-V-Zr-TiO2 catalysts with the selective catalytic reduction (SCR) were prepared by methods of Sol-gel, impregnation (IM) and co-precipitation (CP). The phase compositions, microstructures and specific surface area of the catalysts were analyzed by BET, XRD and SEM, respectively. The effect of CeO2, CoO, V2O5 and V2O5 loading and reaction temperature on the catalytic performances of the as-prepared catalysts was investigated by using the selective reduction of NOx with NH3. The results showed all the as-prepared Co/Ce-V-Zr-TiO2 catalysts were made up of nanometer grains. Compared to conventional TiO2 catalysts, the as-prepared Co/Ce-V-Zr-TiO2 catalysts possessed better catalytic performance, higher adsorbability and larger area of contact with reactant, which is due to large quantity surface micropores. The NOx conversion of SCR over 8 wt%Co/Ce-V-Zr-TiO2 catalysts reached 98.3% at the reaction temperature of 550 oC. Furthermore, the activity of Co/Ce-V-Zr-TiO2 catalysts were improved by the Co loading, however, further increasing the Co loading lead to decrease the catalysis activity.

Abstract: ZnO nanopowders were prepared via solvothermal synthesis by using methanol, ethanol, isopropanol, n-butanol, n-hexanol and 1-octanol as the reaction medium. Effects of alcohol on the properties of the ZnO nanopowders were investigated. XRD, FSEM and UV-visible absorption spectroscopy were used to characterize ZnO nanopowders. The results show that: the type of alcohol had significantly effect on the morphology of ZnO nanopowders. ZnO nanoparticles with diameter ~100 nm were obtained by using ethanol and isopropanol as reaction solvent. ZnO nanorods were obtained with the n-butanol, n-hexanol and 1-octanol as reaction solvent, and the grain size distribution broadened with the increasing of carbon chain of alcohol. The effect mechanism of alcohol was also discussed in detail.