Papers by Author: Wei Li

Abstract: Boron-BiVO₄ samples were synthesized by sol-gel method. They were characterized by UV-vis diffuse reflectance spectroscopy, X-ray diffraction. Photocatalytic activity of the obtained BiVO₄ samples was investigated through degrading methylene blue (MB). The results reveal that boron-BiVO₄ catalysts have monoclinic scheelite structure. The BiVO₄ and Co-BiVO₄ photocatalysts were responsive to visible light. Co-BiVO₄ photocatalyst showed higher photocatalytic activity than pure BiVO₄, resulting in the significantly improved efficiency of degradation of MB.

Abstract: BCB(Bamboo Charcoal Bonded) grinding wheel is a new kind of grinding wheel developed by bamboo charcoal-phenolic resin composite for ELID(Electrolysis In-process Dressing) grinding technique. To study the affection of the ground workpiece surface roughness and removal rate with this new kind of grinding technique, the stainless steel SUS304 was ground using BCB grinding wheel in different machining parameters with ELID grinding condition, and the machining characteristics of BCB grinding wheel has been researched. The experimental results indicated that the ground workpiece surface roughness can be reached to Ra 0.010μm, and the efficient and precision machining with BCB grinding wheel by ELID grinding technique has been achieved for hard-to-cut materials. Finally, by studying of the grinding wheel surface condition and wear, the BCB grinding wheel grinding mechanism has been preliminary discussed.

Abstract: This paper introduced a polishing process for planarization of gallium nitride (GaN) wafer by polishing slurry that is made up by the chemical reaction with H₂O₂ solution and iron. Some different polishing parameters in the polishing process has been analyzed, which affect the surface quality of wafers, such as slurry particle size, polishing times, polishing slurry etc., and trying to improve the polishing process by optimization of the polishing parameters. The experimental result showed that this polishing method has an effect on the surface quality of GaN wafers, finally, the efficient and precision machining with surface roughness of GaN wafers of Ra0.81 nm has been gained by the CMP polishing process.

Abstract: Electronic in-process dressing (ELID) grinding will be a main technology of ultra-precision grinding which has been widely adopted to the ultra-precision and high effectively machining of hard and brittle materials. This study puts forward a new environmental friendly bamboo charcoal bonded (BCB) grinding wheel and develops a new ELID grinding fluid. An oxide layer is mostly determined by the electric performance of grinding fluid in the experiment. This paper founds a model to forecast grinding fluid’s electric performance by BP neural network and MATLAB. This method can be used in developing of ELID grinding machining fluid to improve the ELID grinding effect.

Abstract: The permeated grinding wheel was a new kind of grinding wheel, which was permeated by the chemical additives and solid lubricant into the interior gaps of the grinding wheel. Therefore, the grinding wheel can form a lubrication film on the surface of the grinding wheel. This grinding wheel has some good features, such as lower grinding temperature, smaller grinding force, higher life of the grinding wheel, and can prevent the adhesion of chip onto the grinding wheel surface. The experimental results indicate that the ground surface quality and grinding efficiency have been remarkably improved for more hard-to-cut materials.

Abstract: In this paper, the mechanism of Electrolysis In-process Dressing (ELID) lapping process using new BCB (bamboo charcoal bonded) abrasive wheel is researched. Some experiments of machining for silicon wafers were carried out for exploring the effect of some machining process parameters on material removal rate and surface roughness. Experiments show that: Material removal rate and machined workpiece surface roughness are increased with increase of the lapping wheel’s rotation speed and processing loading; The machined workpiece surface quality is affected with the lapping wheel surface condition, due to the abrasives are trued by electrolysis dressing in the lapping process, therefore the BCB lapping wheel always keeps better machining condition to obtain excellent machined workpiece surface quality efficiently.

Abstract: Electrolytic in-process dressing (ELID) Grinding was an effective machining method for gaining of super smooth surface for hard and brittle materials due to its excellent surface generation capabilities. Bamboo charcoal bonded (BCB) grinding wheel was an environmental friendly ELID grinding wheel which was made up of bamboo charcoal and phenolic resin as bonding agent with high temperature sintering process. In this paper, the electrolysis performances of the BCB grinding wheel with the different resin ratios were researched, and the surface of BCB grinding wheel formed a dense oxide layer in electrolysis action, was illustrated with SEM and XRD analysis.

Abstract: How to achieve the precision double-sided polishing process is a important issue for wafer manufacturing, it depends on machining condition such as machining environment, polishing speed, polishing operation mode, polishing pressure, polishing fluid etc. The key factor to the wafer surface quality is the stability of the polishing pressure. This paper analyzes the impact of double-sided polishing pressure in polishing process, using AMESim software to simulate the pressure standard deviation’s changes under diffrent polishing pressures, and carries out some experiments to identify the impact of polishing parameters (such as the ring gear ratio, polishing speed, polishing pressure) to the polishing pressure stability and the wafer surface quality.

Abstract: A new BCB (Bamboo Charcoal Bonded) grinding wheel was developed by bamboo charcoal-phenolic resin composite under vacuum for ELID grinding technology. The pyrolysis behavior of the new bamboo charcoal-phenolic resin material was studied by thermo gravimetric analysis (TGA), and structural characterization of the new material was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), the friction characteristics was also investigated in this paper.

Abstract: Dual-rotating plates lapping method is a new type of ball machining technology, in which the spin axis angle of the ball could wiggle up to 180°. An investigation was made to verify the motion model of the dual-rotating plates lapping. The ball motion parameters, such as revolution speed, spin speed and spin axis angle were detected experimentally. The results show that the calculated values and the measured ones of the ball motion parameters are almost identical. The motion model of the dual-rotating plates lapping method is thus verified valid.