Shuobo Wang

A one-step hydrothermal preparation strategy for layered BiIO4/Bi2WO6 heterojunctions with enhanced visible light photocatalytic activities

Through the introduction of a new Bi-based semiconductor BiIO4, the novel BiIO4/Bi2WO6 heterojunctions composed of two layered structures were successfully fabricated by a one-step hydrothermal method. The as-prepared samples were thoroughly characterized by XRD, SEM, TEM, HRTEM, XPS, ICP, DRS and PL spectra technologies. The photodegradation experiments indicated that the BiIO4/Bi2WO6 composites showed much higher visible-light-driven (VLD) photocatalytic activity than those of either individual BiIO4 and Bi2WO6 for rhodamine B (RhB) degradation, which are attributed to the high separation of photogenerated electron–hole pairs resulted by the BiIO4/Bi2WO6 heterojunctions. This is the first report of the photocatalytic activity of the new Bi-based compound BiIO4 and BiIO4/Bi2WO6 composites under visible light. Moreover, our research provided a new layered semiconductor, which can be applied in the future for heterojunction construction and energy band structure design.

Band gap engineering design for construction of energy-levels well-matched semiconductor heterojunction with enhanced visible-light-driven photocatalytic activity

Energy-levels well-matched Mg1−xCuxWO4 (0.1 < x < 0.5)/Bi2WO6 heterojunctions with Type II staggered conduction bands and valence bands have been successfully constructed by band gap engineering based on solid-solution design and synthesized by a facile one-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra (DRS) were utilized to characterize the crystal structures, morphologies and optical properties of the as-prepared products. The as-designed Mg0.7Cu0.3WO4/Bi2WO6 heterojunctions consisting of nanocube and nanoplate structures exhibit much higher visible-light-driven (VLD) photocatalytic activity than the two individual components for the degradation of RhB and photocurrent generation. The photoluminescence (PL) spectra, photoelectrochemical measurement, active-species trapping and quantification experiments all indicated that the fabrication of energy-levels well-matched overlapping band structures can greatly facilitate the separation and easy transfer of photogenerated electrons and holes, thus resulting in remarkably enhanced photocatalytic activity. This work provides a novel strategy for semiconductor heterojunction construction and energy band structure regulation.

Process window and mechanism of surface property enhancement of 9Cr18 steel using plasma immersion ion implantation

9Cr18 martensite steel is commonly used as a bearing material in the aerospace industry in China. Because of its ability to treat large and irregular industrial components, plasma immersion ion implantation (PIII) is a good technique to enhance the wear resistance of 9Cr18 precision bearings to extend the working lifetime. We have recently conducted a systematic investigation to determine the process window of nitrogen PIII as well as to identify the enhancement mechanism. The surface properties of 9Cr18 steel after nitrogen PIII under different dosage and plasma conditions (filament hot electron discharge and radio frequency glow discharge) are evaluated by measuring the microhardness, wear property, coefficient of friction, corrosion resistance, as well as elemental depth profiles. Our data indicate that the degree of improvement does not differ substantially under the various PIII conditions thereby suggesting a fairly large process window as long as enough nitrogen is incorporated to form nitride phases.

Simulation of dose uniformity for different pulse durations during inner surface plasma immersion ion implantation

Without the line-of-sight limitation, plasma immersion ion implantation (PIII) emulates conventional beam-line ion implantation in inner surface modification of industrial components. However, dose uniformity on the inner surface is critical. Inner surface PIII of a cylindrical bore is modeled using a two-dimensional fluid model. It is found that the retained dose is not uniformly distributed on the inner surface and the maximum dose is observed away from the edge. The exact location of the maximum dose, which varies with the implant pulse duration, is closer to the center when the pulse width is longer. The maximum relative difference of the retained dose along the interior also depends on the implant pulse duration. It is smaller for a longer pulse duration after a threshold value has been exceeded.

Special 10kV solid state power modulator for plasma immersion ion implantation treatment of industrial bearings

Summary form only given. We have recently developed a 10kV solid state power modulator for the processing of industrial bearings by plasma immersion ion implantation. According to our research results, high energy implantation is not preferred in the treatment of industrial bearings because of the geometry of the races, and a dedicated and less expensive power supply will suffice. In our new design, optical communication modules are used to synchronize the control pulse of each IGBT and a new method is used to generate power for the IGBT gate drive in the solid state modulator In addition to a maximum voltage of 10kV, our inexpensive power modulator can output pulses 2 to 100 microseconds in duration with a rise time of 2 microseconds. The maximum pulsing frequency is 2kHz. We will present the details of the design and the experimental results in this paper.