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Gd2O3 nanoparticles modified g-C3N4 photocatalytic composites were synthesized by a simple one-step hydrothermal method. The structure, morphology, optical properties of the prepared photocatalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and X-ray photoelectron spectroscopy (XPS). The result demonstrates that gadolinium is mainly dispersed on the surface of g-C3N4 in the form of Gd2O3, and does not destroy the lattice structure of g-C3N4. Besides, the gadolinium can cause the red shift of the absorption edge of light, narrow the band gap, and increase the separation efficiency of the photogenerated electron and hole of g-C3N4. Especially, the specific surface area of g-C3N4 can be significantly increased. Furthermore, g-C3N4/Gd-0.05 displays the highest photodegradation performance when it is used for degradation of methyl orange (MO), methylene blue (MB) and Rhodamine B (RhB). The photodegradation rate of g-C3N4/Gd-0.05 composites is 72.4% for MO, 95.5% for RhB, 100% for MB after 120 min under visible light (λ > 420 nm) irradiation. Narrow band gap promotes the separation of photogenerated electron and hole, which enhances the photocatalytic activity of g-C3N4. It is noted that g-C3N4/Gd-0.05 exhibits excellent photocatalytic stability by the photocurrent and the cyclic photodegradation of MO.

In this paper, the transient numerical simulation was used to study the effects of temperature variation in three ways (the open downward parabola, the straight line and the open upward parabola) of side heater in multi-crystalline silicon directional solidification system during solidification period. The melt-crystal (m/c) interface, thermal field and thermal stress during directional solidification of polysilicon have been simulated. The results show that in the process of solidification, compared with the open downward parabola and straight line temperature variation, the temperature change of the side heater depends on the open upward parabola can better control the horizontal and vertical temperature difference in polysilicon, making the deflection of m/c interfaces smaller. Smaller thermal stress distribution can be obtained from the middle stage to the end of solidification while temperature change of side heater according to upward parabola, which is beneficial to improve the quality of polysilicon ingots.

As a new and emerging technology, photocatalytic oxidation is widely used in the fields of sewage treatment and organic pollution control. In this study, CdS nanoparticles were prepared at room temperature by an innovative preparation method, then TiO2 nanorod&ndash, CdS nanoparticle heterojunction photocatalysts were prepared using the solvothermal method, with TiCl3 used as the precursor for TiO2 nanorods. This study mainly took advantage of the small size of the CdS nanoparticles in combination with TiO2 nanorods, and the resultant heterojunctions had large specific surface areas, thereby increasing the contact area between the catalysts and the contaminants. In addition, due to the lower band gap energy (2.4 eV) of CdS, the photo response range of the heterojunction photocatalysts was also increased. In an experimental study, through photocatalytic performance tests of the catalysts with different weight ratios, it was found that the TiO2(40%)@CdS composite had the best photocatalytic performance and the highest catalytic rate. BET, SEM, and other tests showed that the specific surface area of the TiO2(40%)@CdS composite was the largest. TiO2 nanorods and CdS particles were uniformly distributed in the composite, and the optical response range was extended to the visible light region.

The conformation and electronic structure of DNA in single-walled carbon nanotubes (SWCNT) were studied by combining molecular dynamics and first-principles methods. It was found that the π orbital of the SWCNT inner wall induces a conformational change in single stranded DNA (ssDNA) and promotes the adsorption of general-sequence oligonucleotides on the inner walls of the SWCNTs due to π–π stacking interactions. Moreover, they found that the adsorbed oligonucleotides form a helix because of electrostatic and torsional interactions within the sugar–phosphate backbone.

Melt convection during the directional solidification process of multi-crystalline silicon plays a critical role in the transport of impurities. The utilization of a static magnetic field is an effective way to control the melt convection pattern. Studying the effect of the Lorentz force induced by the vertical magnetic field (VMF) on the melt convection of silicon in detail is beneficial to optimize the magnetic field parameters in the production process. Based on the numerical simulation method of multi-physics coupling, this paper explores the effects of different VMF intensities on the convection of silicon melt and the transport of oxygen in the melt during the directional solidification of polycrystalline silicon. The results show that in the first 125 minutes of the crystallization stage, the melt convection velocity is affected significantly by the magnetic field intensities. When different convection circulations are present in the silicon melt, the upper circulation easily transports oxygen to the furnace atmosphere, and the subjacent circulation easily lead to the retention and accumulation of oxygen. Enhancing the VMF intensity to a certain extent can reduce the size of the oxygen retention region in the silicon melt, and the time of the first disappearance of the subjacent circulation near the sidewall of the crucible is shortened. Then the average oxygen concentration in the silicon melt can be reduced. However, a larger vertical magnetic field intensity can result in greater average oxygen concentration in the oxygen retention region.

The sectional heater of industrial-scale directional solidification furnace was designed for improving the quality of the high performance multi-crystalline silicon ingots used for solar cell fabrication. A global numerical model was adopted to investigate the effect of the modified furnace on the thermal field distribution, the shape of the crystal-melt interface and the thermal stress distribution in the solidified silicon ingot during the directional solidification process. Simulation results indicate that the crystal-melt interface shape in the modified furnace with the sectional heater changes from convex at the earlier stage to slightly flat at the later stage, and the thermal stress level at the bottom corner of the solidified ingots is clearly lower than that in the conventional furnace. Furthermore, the designed furnace with the sectional heater was built and experiments corresponding to the numerical simulations were carried out. It was found that a more uniform minority carrier lifetime distribution, lower dislocation cluster density, and lower oxygen concentration were obtained for the silicon ingot grown using the modified furnace. Additionally, the average conversion efficiency of the solar cells fabricated using the grown ingots was evaluated, and it was found that a higher efficiency was obtained for the cells fabricated using the ingots obtained with the modified furnace (18.64%) compared to that for the cells fabricated using the ingots obtained with the conventional furnace (18.54%).

This study proposes two kinds of bottom insulation with a moveable insulation block, with either a narrower or large horizontal width, for use in an industrial-size seeded directional solidification (DS) furnace to produce high-performance multi-crystalline silicon ingot. A transient global model was established to study the effects of the modified configurations on the thermal field in the solidified silicon ingot during the DS process. The numerical results indicate that the shapes of the s-m and m-c interfaces remained relatively flat or slightly convex throughout the entire DS process when the narrower bottom insulation block design was used, and the highest thermal stress in the bottom corner areas of the ingots was obviously lower. To further verify the simulation results, ingot casting experiments and testing were carried out with the use of photoluminescence and minority lifetime mappings. The results show that the dislocation clusters exhibited a lower density in the modified designs. This phenomenon could be attributed to the uniform impurity and lower thermal stress distributions induced by the flat or slightly convex interface. Additionally, the corresponding average conversion efficiency is discussed.