Materials Science Forum Vols. 745-746

Abstract: CuInS₂ quantum dots have been deposited onto mesoporous TiO₂ films on TCO glass substrate via successive ionic layer absorption and reaction process (SILAR) by using three different routes and post-deposition annealing in sulfur ambiance. The influence of the deposition sequence of the In-S and Cu-S on the microstructure of CuInS₂ sensitized TiO₂ electrodes and the photovoltaic performance of the solar cells have been investigated. The microstructure of CuInS₂ sensitized TiO₂ electrodes has been investigated by using X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The optical absorption property of the electrodes has been detected by using UV-Vis spectroscopy, and the photovoltaic performance of CuInS₂ quantum dots sensitized solar cells has been determined by cyclic voltammetry measurement. It has been found that when the Cu-S was deposited prior to In-S, the chalcopyrite phase CuInS₂ could not be observed due to the sublimation of InxS during the annealing under low pressure. A small amount of CuInS₂ has been detected when In-S and Cu-S was deposited alternately onto the TiO₂ films. However, chalcopyrite phase CuInS₂ can be obtained when In-S was deposited prior to Cu-S, and a relative high efficiency of ca. 0.92% (V_oc = 0.35V, J_sc = 8.49 mA·cm^-2, FF = 0.31) has been achieved via SILAR without KCN treatment and rapid thermal annealing.

Abstract: In this study, nanoCe-Zr mixed oxides (CeZrO) were prepared, and XRD, BET surface areas, TEM and TPD-MS were employed for characterization and mechanism analysis. CeZrO was initially used as support for solid tungstophosphoric acid (H₃PW₁₂O₄₀ or HPW) and was found to have promotion effect on the adsorption and decomposition of NOx. After loading with HPW, the NO_x adsorption efficiency increased, and the highest efficiency of HPW/CeZrO was 98%, much higher than that of pure HPW (ca. 60%). With the increase of HPW loading, the NO_x adsorption efficiency tended to reach a peak value before dropping down. The mechanical grinding method was much more suitable than the incipient impregnation method for CeZrO to load HPW. Furthermore, the adsorbed NO_x was found to decompose into N₂, O₂ and N₂O, and yields of N₂ of 29.7% for HPW/CeZrO was obtained upon heating at a ramp rate of 50 °C/min.

Abstract: Hierarchical porous ceria with nanocrystalline was successfully synthesized using filter paper as biotemplate. Unique biomorphic microstructures were characterized by Field Emission Scanning Electron Microscope (FESEM), transmission electron microscopy (TEM) and nitrogen absorption-desorption technique. The obtained ceria material showed the repetitious biomimetic structure consisting of fibre with diameter of ca. 1-3 μm and nanopores which had 2-4 nm apertures. The small crystallite diameter (6-8 nm) and the high specific surface area (71.3 m²·g^-1) of porous CeO₂ were measured by wide-angle X-ray Diffraction (XRD), high resolution TEM (HRTEM) and the BET method. While the concentration of acid fuchsine was 20 mg/L, the porous sample had a higher decoloring rate in a shorter time than others. The decoloring rate can reach 100% after 200 min.

Abstract: A novel hybrid hydrogel (SAT gel) based on covalent crosslinking was prepared by photoinitiated polymerization. Photoactive polystyrene (PS) nanoparticles were successfully synthesized by grafting photoinitiator 2-[p-(2-hydroxy-2-methylpropiophenone)] ethylene glycol methacrylate (HMEM) onto the surface of PS nanoparticles, and characterized by nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscope (HRTEM) and dynamic light scattering (DLS). In the presence of monomer (AAm), PS nanoparticles acting as multifunctional cross-linking agents, and in-situ polymerization was carried out on the surface of photoactive particles. This study focused on the effect of photoactive PS nanoparticles concentration and illumination time on the morphology and swelling behavior of SAT hydrogels. It revealed that the three-dimensional structure and swelling ratio decreased with the increasing concentration of PS nanoparticles. Moreover, the pore size compressed with extending the illumination time. Embedding photoactive nanoparticles into hydrogels network to prepare novel hydrogels had advantages of controllable polymerization process and short forming time. This method provided a new way to prepare soft materials and to design the intelligent hydrogels.

Abstract: A series of Al₂O₃-SiO₂ ceramic cores with titanium sol sintered at 1350, 1450, 1500 and 1550for 2h, respectively, were prepared, and the phase and microstructure were characterized by X-ray Diffraction and Scanning Electron Microscopy. The influence of titanium sol on the phase transformation, shrinkage rate and flexural strength at room temperature has been investigated. The mullite phase formation temperature decreased by at least 150with the addition of 1wt% to 5wt% TiO₂. Additionally, the titania additive promoted the combination of Al₂O₃ and SiO₂, producing mullite phase which reduced the shrinkage and improved the flexural strength.

Abstract: The Pr₂O₃ doped SnO₂ dense ceramic was prepared by co-precipitation method and further sintering. Through the micrograph of the cross-sectional microstructure of the electrodes, the sintering process was analyzed and discussed. Results showed that the solid phase sintering was exhibited at the early stage; when sintering was kept going on, the instant liquid phase could be emerged due to the rich dopants in the grain boundary. Finally, there would be much secondary phase existe as the concentration of dopants reached to a certain value.

Abstract: h-BN/Si₃N₄ composite ceramics were fabricated by gel-casting method and pressureless sintering using Si₃N₄ and h-BN as raw materials. The effect of h-BN on the microstructure and comprehensive properties of h-BN/Si₃N₄ ceramic were investigated. The results showed that the introduction of h-BN hindered the densification of h-BN/Si₃N₄ ceramic as well as the transformation of α-Si₃N₄ to β-Si₃N₄. The mechanical properties of Si₃N₄ based ceramics decreased with the increase of h-BN content, while the thermal property, dielectric properties and machinability increased.

Abstract: Alumina ceramic, with high mechanical strength, good electric insulation, high hardness and good corrosion resistance performance, has been widely used in machinery, electronic and electrical, chemical, medicine, construction and other high-tech areas. In this study, both silicon sol and zirconia particles are incorporated into the system and dense alumina composite ceramics were prepared by cold isostatic processing and pressureless sintering at 1550 . The influence of additives on phase composition, microstructure and mechanical properties were investigated. The XRD results show that mullite phase was generated in the composite ceramic. The composite ceramic has excellent comprehensive performance. For example, the sample with 3wt.% SiO₂ and 5wt.% ZrO₂ has density of 3.87g·cm^-3, Vickers hardness of 17.6GPa, flexural strength of 369.0MPa, youngs modulus of 374.2GPa and fracture toughness of 3.57MPa·m^1/2.

Abstract: The luminescent material, composed of rare-earth-doped alkaline earth aluminate, has been paid wide attention because of its chemical stability, usability and non-radioactive. In this study, the luminous material SrAl₂O₄:Eu²⁺,Dy³⁺ was prepared by a microwave method. The effect of microwave parameters on the performance of the luminous powder was investigated. The excitation and emission spectrum of the luminous material were measured by fluorospectrophotometer. The phase composition of the powder was analyzed by XRD. The results show that the luminous powder can be synthesized only when the microwave power is higher than the med-high fire (640W). The sample has the best luminous property when the molar ratio of Sr (NO₃)₂:Al (NO₃)₃·9H₂O:H₃BO₃:Eu (NO₃)₃·6H₂O:Dy (NO₃)₃·6H₂O is about 1:2:0.5:0.04:0.08, and it is processed by high power for 20min in microwave oven.

Abstract: Graphene nanosheet (GNS)/ Al₂O₃ composite powder with homogeneously distributed GNSs has been fabricated from wet ball milled expanded graphite and Al₂O₃, and then followed by the rotary evaporator at relatively low temperature to dry the mixture and the residual solvent was removed in atmosphere-vacuum pipe-type furnace accessing mixed gases of Argon and Hydrogen at 600 for 6h. During the process, homogeneously dispersed and mixed GNS/ Al₂O₃ composite powders with quite few damage of GNSs structure and properties have been obtained. The microstructures and grain sizes of GNS/ Al₂O₃ composite powders have been investigated. The results showed that the addition of GNSs had diminished the size of Al₂O₃ particles and also the as-prepared GNSs/ Al₂O₃ composite powders can be dispersed and mixed more homogeneously remarkably with the presence of GNSs.