Chuanhai Gan

Fabrication and characterization of SiO2@TiO2@silicalite-1 catalyst and its application for degradation of rhodamine B

SiO2@TiO2@silicalite-1 catalyst, with TiO2 (Degussa P25) nanoparticles encapsulated by SiO2 and adhered on the surface of silicalite-1 zeolite, was successfully fabricated by combining pressing, sintering and infiltration methods. The samples were characterized by XRD, SEM, FT-IR, TEM, nitrogen sorption, and UV-vis diffuse reflectance spectra. The photocatalytic properties were investigated by degradation of rhodamine B (RhB) aqueous solution under UV light. The results show that TiO2 nanoparticles are coated with a SiO2 shell and bonded together. The core/shell structure of TiO2@SiO2 is attached to the surface of silicalite-1 particles. The photocatalytic efficiency of TiO2@silicalite-1 is 97.4%. When the catalyst is coated with SiO2, its photocatalytic efficiency is significantly improved to 99.7%. Furthermore, the rate of degradation using SiO2@TiO2@silicalite-1 is 1.54 times faster than that using TiO2@silicalite-1.

Redistribution of iron during directional solidification of metallurgical-grade silicon at low growth rate

Redistribution of iron during directional solidification of metallurgical-grade silicon (MG-Si) was conducted at low growth rate. Concentrations of iron were examined by ICP-MS and figured in solid and liquid phases, at grain boundary and in growth direction. Concentrations are significantly different between solid and liquid phases. The thickness of the solute boundary layer is about 4 mm verified by mass balance law, and the effective distribution coefficient is 2.98×10−4. Iron element easily segregates at grain boundary at low growth rate. In growth direction, concentrations are almost constant until 86% ingot height, and they do not meet the Scheil equation completely, which is caused by the low growth rate. The effect of convection on the redistribution of iron was discussed in detail. Especially, the “dead zone” of convection plays an important role in the iron redistribution.

Formation and Orientational Distribution of Cracks Induced by Electromagnetic Induction Soldering in Crystalline Silicon Solar Cells

Soldering technology has major influence on the performance of crystalline silicon (c-Si) solar cells in the photovoltaic (PV) module. The mechanism of formation of cracks due to soldering is still highly debatable. In this paper, the formation and orientational distribution of cracks induced by electromagnetic induction soldering were investigated. For this purpose, the numbers of cracked cells and poorly soldered cells were counted, and different types of cracks and poor soldering were compared and analyzed. The results show that the diagonal crack is predominant in mono-c-Si cells, while the short crack perpendicular to bus-bar is the main type of crack in multi-c-Si cells. Moreover, the intersect crack is common in mono-and multi-c-Si cells. Thereafter, a model was put forward to explain the formation and propagation of cracks. Finally, the quality of electromagnetic induction soldering was investigated, which established that the defective cells, including cracks or poor soldering, constituted only about 0.4% of the total soldered cells.