Xin Sui

Fluorescence of silicon nanoparticles prepared by nanosecond pulsed laser

A pulsed laser fabrication method is used to prepare fluorescent microstructures on silicon substrates in this paper. A 355 nm nanosecond pulsed laser micromachining system was designed, and the performance was verified and optimized. Fluorescence microscopy was used to analyze the photoluminescence of the microstructures which were formed using the pulsed laser processing technique. Photoluminescence spectra of the microstructure reveal a peak emission around 500 nm, from 370 nm laser irradiation. The light intensity also shows an exponential decay with irradiation time, which is similar to attenuation processes seen in porous silicon. The surface morphology and chemical composition of the microstructure in the fabricated region was also analyzed with multifunction scanning electron microscopy. Spherical particles are produced with diameters around 100 nm. The structure is compared with porous silicon. It is likely that these nanoparticles act as luminescence recombination centers on the silicon surface. The small diameter of the particles modifies the band gap of silicon by quantum confinement effects. Electron-hole pairs recombine and the fluorescence emission shifts into the visible range. The chemical elements of the processed region are also changed during the interaction between laser and silicon. Oxidation and carbonization play an important role in the enhancement of fluorescence emission.

Fabrication and Tribological Behavior of Ni-ZrO2 Nanocomposite Coatings Prepared by Electrodeposition in Ultrasonic Field

Ni-ZrO2 nanocomposite coatings were fabricated by electrodeposition from a modified Watt’s type electrolyte containing ZrO2 nanoparticles, where an ultrasonic field was imposed during electrodeposition process. The weight percent of ZrO2 in coatings and the surface morphology of coatings were examined. The microhardness and tribological properties of Ni-ZrO2 nanocomposite coatings and pure Ni coating were investigated. The results show that ultrasonic agitation can greatly affect the microstructure and the tribological behavior of Ni-ZrO2 nanocomposite coatings. The Ni-ZrO2 nanocomposite coatings record variable ZrO2 contents and surface morphologies by modifying ZrO2 concentration in electrolyte and ultrasonic parameters. The Ni-ZrO2 nanocomposite coating fabricated with ultrasonic agitation exhibits finer grains and more compact structure compared to pure Ni coating and the Ni-ZrO2 nanocomposite coating fabricated without ultrasonic agitation. The dispersed ZrO2 nanoparticles in coatings and ultrasonic agitation during electrodeposition synthetically contribute to the grain refinement of the coatings. Therefore, the Ni-ZrO2 nanocomposite coating by ultrasonic electrodeposition exhibits high microhardness and excellent tribological behavior. In general, the improvement in friction and wear properties of Ni-ZrO2 nanocomposite coatings can be attributed to the homogeneously dispersed ZrO2 nanoparticles and the finer-grained structure.Copyright

Laser-based measurement for micro-unbalance of cylindrical rollers of the high-speed precision rolling bearings

It is a stringent requirement for China to develop the technology on the measurement for the unavoidable micro residual unbalance of tiny cylindrical rollers of the high-speed precision bearings, which are widely equipped on high-end advanced equipment. During the measurement process, the vibration response excited by micro unbalance, which is easy to be messed up with background noise, is hard to be detected and a soft support mounting bracket is proposed to enhance the amplitude of vibration response, while maintaining the steady rotation of test roller. Accordingly, a dynamic model of both test roller and mounting bracket is constructed to analyze and simulate the vibration response. Furthermore, a μm level high precision laser-based non-contact measurement system consisting of a roller rotation drive system and a vibration signal acquisition system is developed to measure the synchronized vibration of the unbalance. Finally, by comparing experiment results of a standard roller with a special prepared unbalanced roller and comparing experiment results with simulated results, the validity of the proposed measurement method is verified.

Development of On-Line Condition Monitoring System for Wind Turbines in Plant Level

The maintenance cost of wind turbines has become the significant challenge for the wind power enterprise. One available way to reduce the cost is to monitor the wind turbines and make preventative maintenance. In this paper, an on-line condition monitoring system for wind turbines in plant level was presented. A 4-level monitoring structure was designed for the system, and the network communication was used to transmit the data efficiently. A high performance digital signal processor (DSP) was used as the processing core in the signal acquisition device. A computer software was also developed for data analysis and remote management of the monitoring device. The vibrations, temperature, and some other information of the turbines were gathered synchronously. The monitoring center in wind farm, the data center of wind power enterprise and the remote service center of equipment supplier can know the operation condition of wind turbines well. It would be useful for wind power enterprise to obtain the operation condition of wind turbine and reduce the cost of maintenance.Copyright