Porous Si/TiO 2 nanowire photoanodes were prepared by a combination of hydrothermal synthesis and metal-assisted chemical etching. Characterization of samples was conducted using scanning electron microscopy and X-ray diffraction, the results showing that a porous Si/TiO 2 heterojunction structure was synthesized. Diffuse reflection spectra show that the porous Si/TiO 2 nanowire photoanodes have a strong absorption. Photocurrent measurement shows that the photocurrent of the porous Si/TiO 2 nanowire photoanodes at 6 h is higher than that of others in the measuring region. The photoelectric catalysis (PEC) activities of porous Si/TiO 2 nanowire photoanodes were evaluated in degradation experiments of methylene blue under simulated solar light irradiation, and the sample at 6 h shows the highest PEC activity. Meanwhile, the PEC activity of the porous Si/TiO 2 nanowire photoanode is higher than that of the single direct photocatalysis process or electric catalysis. The mechanism of the PEC of the porous Si/TiO 2 nanowire photoanodes has been explained.

No abstract

No abstract

A 1.3-GHz copper cavity chemical polishing system has been developed by the Institute of High Energy Physics. It has been used for the surface treatment of copper cavity substrates before the niobium sputtering. The system uses the SUBU polishing agent developed by the European Organization for Nuclear Research (CERN), which is a four-component mixed acid with a working temperature of 72∘C. For environmental protection reasons, the system adopts a fully closed-cycle mode, which prevents acid volatility at high temperatures to the ambient environment. Based on the sample experiments, polishing steps have been optimized to avoid as much as possible the oxidation phenomenon which is easily introduced to the copper cavity inner surface, including cooling, dilution, and passivation process. Finally, the surface treatment process of the closed polishing system was determined based on the optimized polishing steps, and the oxygen isolation protection method after treatment was put forward to accommodate long-distance transportation of the copper cavity before coating. The experimental results show that the surface of the copper cavity after chemical polishing was smooth and bright with an average roughness of 0.12 μm.