Single-crystalline ZnO nanowire arrays with different aspect ratios and nanowire densities were prepared by the hydrothermal growing method using polyethyleneimine (PEI) as a surfactant. PEI can only hinder the latera...Single-crystalline ZnO nanowire arrays with different aspect ratios and nanowire densities were prepared by the hydrothermal growing method using polyethyleneimine (PEI) as a surfactant. PEI can only hinder the lateral growth of the ZnO nanowires, which is observed by high resolution transmission electron microscopy (HRTEM) analysis. Dye-sensitized solar cells were assembled by the ZnO nanowire arrays with different thicknesses, which can be controlled by the growing time and characterized using photocurrent-voltage measurements. Their photocurrent densities and energy allover conversion efficiencies increased with increasing ZnO nanowire lengths. Short-circuit current den-sity of 4.31 mA-cm-2 and allover energy conversion efficiency of 0.87% were achieved with 12.9-μm-long ZnO nanowire arrays.展开更多
Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sinter...Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the Sm2O3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900°C. The results indicated that the ionic conductivi- ties of Sm0.20Ce0.8O1.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the Arrhenius equation. Then the Sm2O3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.展开更多
By using micron α-Si3N4, SiO2, Al2O3 and h-BN as starting materials, O’-SiAlON-BN （Si 2-Z AlZO 1+Z N<sub> 2-Z , z=0.3） composite was synthesized by reaction sintering. According to theoretical proportion rat...By using micron α-Si3N4, SiO2, Al2O3 and h-BN as starting materials, O’-SiAlON-BN （Si 2-Z AlZO 1+Z N<sub> 2-Z , z=0.3） composite was synthesized by reaction sintering. According to theoretical proportion ratio: n（SiO2）/n（α-Si3N4） =1, the effects of two sintering aid composites, Y2O3+B2O3 and Y2O3+TiO2 at 1700℃ for 2h, were studied. The results indicate that Y2O3+TiO2 as sintering aid can accelerate reaction sintering of O’-SiAlON-BN more effectively than Y2O3+B2O3, and the relative density of the composites declined with the increase of BN addition （10%, 20% and 30% respectively）; XRD analysis found that excessive β-Si3N4 existed in the O’-SiAlON-BN composite. Therefore, in order to get more pure O’-SiAlON and BN phases in the composites ore SiO2 is needed. When Y2O3+TiO2 was used as sintering aid and addition of BN was 10%, the result of cross experiment on condition of A—n（SiO2）/n（α-Si3N4） was 1.05, 1.1 and 1.2; B—addition of sintering aid was 2%, 4% and 6%; C—firing temperature was 1600℃, 1650℃ and 1700℃; D—soaking time was 1h, 2h and 3h, shows that the sintering properties were influenced by factors of firing temperature, soaking time, addition of sintering aid and n（SiO2）/n（α-Si3N4） in order of importance. In addition, the technical parameter A3B3C3D3 can achieve the highest relative density. Besides, using Pattern Recognition method, the optimized parameter range to form pure O’-SiAlON and BN without β-Si3N4 remained was determined as Y>1024X2-230.400X+11.088（X=0.9999A-0.0006C-0.0163D,Y=0.0163A+ 0.0009B -0.0014C+0.9999D）.展开更多
基金financially supported by the National Science Foundation of China (Nos.10775096 and 51072112)China Postdoctoral Science Foundation (No.20100480579)+4 种基金Key Subject of Shanghai Municipal Education Commission (No.J50102)Special Research Foundation for Training and Selecting Outstanding Young Teachers of Universities in ShanghaiInnovation Foundation of Shanghai UniversityNature Science Foundation of Shanghai (No.06ZR14035)Shanghai Leading Academic Disciplines (No.T0101)
文摘Single-crystalline ZnO nanowire arrays with different aspect ratios and nanowire densities were prepared by the hydrothermal growing method using polyethyleneimine (PEI) as a surfactant. PEI can only hinder the lateral growth of the ZnO nanowires, which is observed by high resolution transmission electron microscopy (HRTEM) analysis. Dye-sensitized solar cells were assembled by the ZnO nanowire arrays with different thicknesses, which can be controlled by the growing time and characterized using photocurrent-voltage measurements. Their photocurrent densities and energy allover conversion efficiencies increased with increasing ZnO nanowire lengths. Short-circuit current den-sity of 4.31 mA-cm-2 and allover energy conversion efficiency of 0.87% were achieved with 12.9-μm-long ZnO nanowire arrays.
文摘Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the Sm2O3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900°C. The results indicated that the ionic conductivi- ties of Sm0.20Ce0.8O1.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the Arrhenius equation. Then the Sm2O3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.
文摘By using micron α-Si3N4, SiO2, Al2O3 and h-BN as starting materials, O’-SiAlON-BN （Si 2-Z AlZO 1+Z N<sub> 2-Z , z=0.3） composite was synthesized by reaction sintering. According to theoretical proportion ratio: n（SiO2）/n（α-Si3N4） =1, the effects of two sintering aid composites, Y2O3+B2O3 and Y2O3+TiO2 at 1700℃ for 2h, were studied. The results indicate that Y2O3+TiO2 as sintering aid can accelerate reaction sintering of O’-SiAlON-BN more effectively than Y2O3+B2O3, and the relative density of the composites declined with the increase of BN addition （10%, 20% and 30% respectively）; XRD analysis found that excessive β-Si3N4 existed in the O’-SiAlON-BN composite. Therefore, in order to get more pure O’-SiAlON and BN phases in the composites ore SiO2 is needed. When Y2O3+TiO2 was used as sintering aid and addition of BN was 10%, the result of cross experiment on condition of A—n（SiO2）/n（α-Si3N4） was 1.05, 1.1 and 1.2; B—addition of sintering aid was 2%, 4% and 6%; C—firing temperature was 1600℃, 1650℃ and 1700℃; D—soaking time was 1h, 2h and 3h, shows that the sintering properties were influenced by factors of firing temperature, soaking time, addition of sintering aid and n（SiO2）/n（α-Si3N4） in order of importance. In addition, the technical parameter A3B3C3D3 can achieve the highest relative density. Besides, using Pattern Recognition method, the optimized parameter range to form pure O’-SiAlON and BN without β-Si3N4 remained was determined as Y>1024X2-230.400X+11.088（X=0.9999A-0.0006C-0.0163D,Y=0.0163A+ 0.0009B -0.0014C+0.9999D）.
