Advanced Materials Research Vols. 476-478

Abstract: Aluminum films were evaporated on quartz substrates, and then an npp+ structure was formed by a p/n junction deposited on the aluminum film. The Raman, XRD and SEM were used to analyze the crystallization and components of the samples before and after annealed. The results showed that they were compact and almost 100% in crystallization after annealing and carrier motility also increase. The mechanism of the rapid thermal process is also proposed, its superior effect mainly contributes to the photoelectron induced diffusion process, in which the short wavelength of the tungsten plays an important role.

Abstract: Electron beam melting is an effective method to remove volatile impurities in silicon, during which impurities such as P, Al and Ca etc. can be removed to less than 0.3×10^-4wt.%. However, so far there is few research on the influence of electron beam parameters, such as beam density and beam size, on molten pool morphology, hence electron beam melting process has not been completely understood, which leads to low energy utilization. In this paper, on the basis of beam size calibration, the influence of beam density and beam size on molten pool morphology is investigated and the concept of melting angle is proposed to characterize molten pool morphology. At the same time, the optimal molten pool morphology for impurities removal and the corresponding electron beam parameters are also analyzed.

Abstract: In this paper, the applicability of Gd0.9Ca0.1AlO3-δ (GCAO) oxygen-ion conductor as ceramic electrolyte for intermediate temperature solid oxide fuel cells (SOFCs) was systematically investigated. XRD and TGA results demonstrate that GCAO material is in possession of sufficient structural stability from low to high temperature, desirable chemical stability against humidified reducing atmosphere and fine high-temperature thermal stability in air. Thermal shrinkage research during high temperature sintering shows that complete sintering of pressed green GCAO disk is around 1500 oC and the corresponding thermal expansion coefficient of sintered GCAO is 9.2×10-6 K-1 from room temperature to 1000 oC. In addition, total conductivity of GCAO ranges from 0.00073 to 0.0081 S•cm-1 in air as function of temperature increasing from 600 to 800 oC where the corresponding activation energy is determined as 96.19 KJ•mol-1. A 2-mm-thick electrolyte-supported single fuel cell was prepared with La0.8Sr0.2TiO3-δ/Ce0.8Gd0.2O2-δ and La0.8Sr0.2MnO3-δ/Ce0.8Gd0.2O2-δ as anode and cathode, and tested at 800 oC with humidified hydrogen and static air as fuel and oxidizer, respectively. The OCV reaches as high as 1.1 V which prove the pure oxygen-ion conduction of GCAO; and the corresponding maximum output and electrode polarization resistance reach 42 mW/cm2 and 0.15 Ώcm2, respectively. In summary, GCAO could be a possible electrolyte candidate for intermediate temperature SOFCs.

Abstract: In the article, blade element momentum theory is used for calculated aerodynamic load of blade under the different wind velocities. 3D model of key functional components such as blade, tower, hub and nacelle are modeled in Solidworks, the MNF files of blade and tower are gained in finite element analysis software after flexible processed, and the rigid-flexible multi-body dynamic model of the wind turbine’s key components is created in ADAMS. Through simulation of the model under constant rotate speed, kinematics and dynamics curves are got while the wind speed rise from 5m/s to 25m/s. This simulation can imitate vibration performance ideally. A feasible method is provided for the virtual prototype simulation of wind turbines.

Abstract: The porous silicon layer was fabricated by electrochemical etching process using an aqueous HF-based electrolyte. The characterizations of porous silicon layer were investigated by Emission-type scanning electron microscope (SEM), Raman spectra and X-ray diffraction (XRD). With the current density increasing, the pore diameter and density become much bigger. This result also was confirmed by Raman spectra and XRD result of samples, which revealed the decreasing of grain size of silicon. The resistivity of crystalline silicon increased when the porous layer was removed after heat treatment at 850°C for 2.5h, which should be attributed to the gettering process of porous silicon.

Abstract: In this paper, we created some microstructures on the surface of silicon by irradiating a silicon wafer for soalr cell with trains of short pulses in the presence of an ambient gas.The laser pulse produced by TEA CO2 laser is high power and shorter than a microsecond in duration. We found that the morphology of the structures is highly dependent on the species of ambient gas and the number of laser pulses used. I note that surfaces covered with these microstructures have striking optical properties: structures absorb approximately 90% of incident light with wavelengths between 250 nm and 0.85μm.The remarkable and potentially useful optical properties of the structures should be beneficial in increasing the efficiency of crystalline silicon soalr cell.

Abstract: Hydrogen generation through high temperature solid oxide electrolysis cells (SOEC) has recently received increasingly international interest in the large-scale, highly efficient nuclear hydrogen production field. To achieve cost competitive electrolysis cells that are both high performing i.e. minimum internal resistance of the cell, and long-term stable, it is critical to develop electrode materials that are optimal for steam electrolysis. In this paper, the cathode materials of SOEC are reviewed. Ni-YSZ and Ni-SDC/GDC cermets are promising cathode materials for SOEC working at high temperature. The solid oxide matierials are promising cathode materials for SOEC working in atmospheres with low content of H2,e.g. in smaller scale generators used intermittently without H2 purging. More works, both experimental and theoretical, are needed to further develop SOEC cathode materials.

Abstract: Well-dispersed TiO2 nanoparticles were successfully prepared ultrasonic microemulsion method in this paper. The morphology and microstructure of the products were characterized by the laser particle size analyzer, Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and transmission electron microscope (TEM). It was found that the TiO2 nanoparticles obtained from this method have well-proportioned size distributions; the surfactant (CTAB) molecule was adsorbed on the surface of TiO2 nanoparticles precursor, which is favorable for the dispersion of TiO2 nanoparticles; the TiO2 nanoparticles calcined was a crystal of the cubic structure. In addition, the mechanism on the formation of the TiO2 nanoparticles was also proposed in this paper.

Abstract: CO2 adsorbent, MgO/γ-Al2O3, was prepared by impregnation methods. The structure and surface properties of the prepared materials were characterized by XRD, N2 adsorption-desorption, in situ FIIR and CO2-TPD techniques. The results indicated that the surface area, pore size and pore volume of materials decreased with the introduction of MgO. Their capacity for CO2 adsorption could be significantly improved when the MgO loading increased from 0 to 10 wt %. CO2-TPD and in-situ FTIR showed that the materials have three basic sites which can react with CO2 to form bicarbonate, bidentate carbonate and monodentate carbonate species.

Abstract: Pyramidal texture is one traditional method to realize antireflection for c-Si solar cells, due to its low cost and simplicity. As one high efficiency silicon solar cell, amorphous/crystalline silicon heterojunction (SHJ) solar cell has attracted much attention all over the world. The heterojunction interface with very low defects and interface states is critical to the SHJ solar cell performance. In order to obtain high quality interface passivation by depositing a very thin intrinsic amorphous silicon layer on the textured Si conformally, large size pyramidal texture with no metal ion contamination is required. In this work, we utilized tetra-methyl ammonium hydroxide (TMAH) instead of NaOH in the alkaline etching to prepare pyramidal texture on N-type monocrystalline silicon to avoid the possible Na+ contamination. By optimizing the etching conditions, uniform large size pyramidal texture with pyramid size of about 10 μm was fabricated successfully. Furthermore, excellent antireflection performance was demonstrated on such textured Si surface. The average reflectance was lower than 10% in the visible and near infrared spectrum range. Such pyramidally textured Si wafers will be very suitable for SHJ solar cells.