Papers by Keyword: Mechanical Polishing

Abstract: The hydrolytic properties of LiAlO₂ (LAO) are important factors for its applications on LED fabrication. During soft pad polishing process, the H₂O in the slurry is deleterious for LAO surface polishing results. The current study develops a material removal rate model for materials with hydrolysis reaction to predict the result of polishing process.The current research conducts the experimental studies to investigate the material removal rate and its mechanism during the soft pad polishing process. In the experimental study, the hydrolytic properties of LAO have been tested to understand the hydrolysis speed with different operation parameters to assist the development of the theoretical model. Also the material removal rates of LAO with hydrolytic property have been measured under different soft pad polishing operating conditions. The experimental results provide the hydrolytic properties of LiAlO₂ to understanding of the mechanism on polishing process.

Abstract: To remove the surface damages induced during mechanical polishing (MP) of 4H-SiC, a variety of wet etching recipes and etching conditions were studied. By evaluating the epilayers grown on these etching-treated wafers, it has been found that triangular defects (TRDs) are the main defects originated from the MP-induced damages in these samples. High temperature molten KCl etching at 1100 °C with KOH additive is very effective to remove the damaged surface while keeping a relatively flat surface. Epilayer grown on the KCl+KOH etched wafer showed a TRD density <0.9 cm^-2.

Abstract: There are numerous parameters and steps involved in a computer controlled ultra-precision polishing process (CCUP). The success of CCUP relies heavily on the understanding and optimization of material removal when new materials and new surfaces are polished. It is crucial to optimize the polishing parameters to enhance the effectiveness of the polishing process and to assess the impact of different process parameters on the material removal rate of particular difficult-to-machine materials such as CoCr alloys, which is commonly used in orthopedic implants. This paper aims at studying the process parameters and optimization of the parameter to enhance the material removal rate and quantify the contribution of process parameters.

Abstract: A three-dimensional molecular dynamics (MD) simulation is conducted to investigate the effect of the abrasive rotating velocity on monocrystalline silicon specimen by mechanical polishing at atomistic scale. By monitoring relative positions of atoms in the monocrystalline silicon specimen, the microstructure of monocrystalline silicon is clearly identified and analyzed. The simulation results show that better machined surface quality is obtained and more phase transformation atoms occur with small abrasive rotating velocity. When the abrasive rotating is high, the surface quality deteriorates and amorphous layer thickens.These results provide us an effective approach to analyze the mechanism of material deformation and the formation of the machined surface after ultra-precision polishing.

Abstract: High temperature (>1000 °C) chemical etching using molten KCl or molten KCl+KOH as the etchant has been carried out to remove the mechanical-polishing (MP) induced damage layer from 4H-SiC surface. Atomic force microscopy observations have shown that line-shaped surface scratches that have appeared on the as-MPed surface could be completely removed by KCl-only etching or by KCl+KOH etching (KCl:KOH=99:1 in weight) at ~1100 °C. Between the two recipes, KCl+KOH etching has shown a higher etch rate (6~7 times) and is able to remove ~9 μm and ~36 μm-thick damage layer from the Si (0001) and the C(000-1) surface, respectively. Besides, KCl+KOH etching seems to have formed a Si (0001) surface covered with atomic steps while KCl-only etched surface is featured with nanometer-scale pores.

Abstract: Electron beam induced current (EBIC) observations have been carried out to investigate the influence of mechanical polishing (MP) direction on the dislocations formation at the Si-face c(0001) of 4H-SiC epitaxial layers. Two opposite MP directions (defined by polish pad moving direction) have been compared, which are [11-20] off-cut directions along step-up and step-down, respectively. It has been found that high density of dislocations have been formed along the polish paths for the 8o off samples with polishing pad moved in step-up direction. By contrast, step-down polishing samples have shown no significant dislocation increase although shallow polish scratches were observed. Similar experiments have also been carried out for 4o off samples, showing step-up MPs introduced more dislocations than step-down ones. The results are discussed in terms of forces along the slip plane [11-20](0001) effectively exerted by the abrasive particles on the steps.

Abstract: Using the surface self-nanocrystalline technology can produce dense nano layer without the defects such as pores. The surface self-nanocrystalline technology can improve the micro hardness, abrasive resistance, fatigue durability, corrosion resistance and other combination properties. It is with wide application prospect in the industrial area. In this article, the application investigation of the surface self-nanocrystalline technology such as the surface mechanical polishing method, ultrasonic impacting method, ultra sound peening ect. improving the prehensive properties of the materials are summed up. And the study work of the surface self-nanocrystalline technology in the future is prospected here.

Abstract: In the paper, the ELID grinding is, first of all, adopted to pre-process the surface of WC-Co cemented carbide, obtaining the precision machined surface, Ra=18nm.Then the mechanical polishing process is implemented. When conducting mechanical polishing, the polishing liquid with W1 diamond grits is used to process the surface about 100 minutes after ELID grinding, aiming to achieve rapid removal. About 100 minutes again, the ultra-precision surface, Ra=4nm, is obtained, by the mechanical polishing ,using the polishing liquid with W0.5 diamond grits .Meanwhile, on the surface roughness effects of abrasive type, grain size, polishing liquid solvents, polishing pressure, polishing machining time and so on, are researched in-depth for the process of mechanical polishing.

Abstract: Mechanical polishing is a primary technique for planarization of material surface in manufacture fabrication. Because the theoretical polishing mechanism is inadequately understood and because higher levels of polishing performance are desired, the investigation of experiment becomes more important. In this paper, a high precision polishing machine has established. With an improved design, a test rig can be easily used to simulate the mechanical polishing process and acquire the signals of polishing. The temperature-rise and shear force are measured for three different materials (i.e. copper, aluminum and silicon wafer) during mechanical polishing process. For the self-design test rig in the mechanical polishing process, its surface temperature is measured by T-type thermocouples screwed behind the polishing interface of the carrier. And shear force is measured by a load transducer mounted on the lever and connected with the polishing head. Furthermore, the roughness and particle size effects during polishing are demonstrated. The experimental results not only provide a good index to end-point-detection, but also increase the understanding of mechanical polishing process.

Abstract: The interaction between the tungsten steel surface and the polishing fluid & abrasive were discussed by AFM, SEM and XRD test in order to compare the chemical performances and mechanical action of the tungsten steel polishing in the paper. The chemical mechanical polishing (CMP) and the mechanical polishing (MP) was employed, respectively. The experiments results indicated that the CMP with a higher the materials removal ratio than by MP. Because a chemical corrosion effect implies that slurries with the highest removal rate have high dissolution rate, and have a lower the residual stress, however the surface took on wrinkling.