Narrow Results

Different pretreatment methods for electroless nickel and cobalt plating are demonstrated and compared in the present investigation. The surface morphologies of the nickel or cobalt deposits are investigated by scanning electron microscopy (SEM), and the chemical compositions of the coatings are analyzed by energy-dispersive X-ray spectroscopy (EDX). Method of single-step pretreatment is selected as the optimized method for electroless nickel plating process, while improved two-step sensitization-activation and single-step pretreatment methods can be selected for electroless cobalt plating. It can be found that the content of free Co is much lower compared to electroless Ni plating.

This paper presents a model for producing nano-microparticles by ultrasound-aided electric discharge. After machining, scanning electron microscopy (SEM) was used to check the shape and size of the nickel particles; they were found to be distributed in a few micrometers to 80 $\mu$m range. The nickel particles were regular spherical shaped, and the grain sizes of the particles were different. In addition, many small particles were attached to the surface. Various methods such as inlay polishing, nitric acid etching, and direct SEM imaging were employed to determine the hollow nickel particles such as very thin particles, large thickness grains, hollow sponge-like structures, and solid particles.

A unique hollow microsphere TiO₂/ZnO p–n heterojuction was successfully fabricated via a one-step hydrothermal method for degradation of 2,4-Dinitrophenol. The enhancement of mineralization of 2,4-dinitrophenol (2,4-DNP) via photocatalytic degradation of TiO₂/ZnO p–n heterojuction was investigated. The 2,4-DNP was degraded completely by TiO₂/ZnO, and 78% of the total organic carbon (TOC) was removed which is greatly superior to that on the controlled TiO₂, ZnO with 53%, 45%, respectively. A schematic diagram of photocatalytic oxidation mechanism of 2,4-DNP was also presented by $\cdot$OH radical detection. The oxidation of 2,4-DNP and the intermediate productions was based on the hydroxyl (OH) with a high oxidation potential of 2.8V. Moreover, the excellent stability and reliability of the TiO₂/ZnO composite hollow microsphere photocatalyst demonstrated its promising application for removal of organic pollutant from water.

Water pollution caused by intensive use of organic dyes has become an increasingly serious problem recently. Green and efficient processes are desperately needed to remove persistent organic pollutants from waste waters. Herein, Ag nanoparticles loaded ZnO hollow microspheres were synthesized through a simple solvothermal method and used as a photocatalyst for dye degradation. The calculated band gap of Ag/ZnO — 5% (2.97eV) is much narrower than that of pure ZnO (3.37eV). The obtained Ag/ZnO samples show a remarkable photocatalytic activity in photodegradation of Rhodamine B (RhB) under simulated sunlight irradiation. The degradation efficiency of RhB for Ag/ZnO — 5% is 98.8% after 100min irradiation while only 52.8% degradation rate is obtained over pure ZnO. The enhancement is attributed to the exposed active ZnO (001) plane and the surface plasmon resonance (SPR) effect of Ag nanoparticles that promote the separation of photogeneated electrons and holes.