Advanced Materials Research Vols. 24-25

Abstract: Cryogenic polishing single silicon wafer with nano-sized CeO2 abrasives can be known as cryogenic fixed abrasives CMP (CFA-CMP). The abrasive slurry was made of nano-sized CeO2 particles dispersed in de-ionized water with a surfactant and the polishing slurry froze to form cryogenic polishing pad. Then the polishing tests of the blanket silicon wafers in the presence of the cryogenic polishing pad containing the nano-particulates were carried out. The morphologies and surfaces roughness of the polished silicon wafers were observed and examined on an atomic force microscope (AFM). The results show that a super smooth surface with roughness of 0. 293 nm is obtained within 5000 nm× 5000 nm and the removal of material is dominated by plastic flowage.

Abstract: In this study, rock minerals of natural stone were finely polished with loose abrasive and ELID technology to study the surface behaviours. After these rock specimens were polished to ultra smooth surfaces, the surface characteristics were observed with microscope and analyzed with surface texture analyzer. It was found that the calcite and fluorite minerals could be polished to high surface quality with fine loose aluminum oxide abrasive. But ultra smooth quartz surface must be finished with superabrasive ELID polishing technology. The weakly acidic coolant might bring chemical damage to calcite and fluorite minerals under the condition of ELID polishing process.

Abstract: Laser surface texturing (LST) technology that is firstly used in rollers, is a specialized surface engineering process capable of enhancing the surface material properties, wear resistance, fretting fatigue life and reducing friction. This practical technology of the LST process is based on a pulsating laser beam that, by material ablation, generates the optimum topographical surface. In order to exploit the full potential of the process, a great amount of research has explored from the material removal mechanics to the development of the LST process. This paper reports on the LST research involving the LST technology surveying process optimization, LST equipment and its industrial applications. The paper also highlights the forming theory describing the skin-pass process of transferring the textured roller’s surface structure onto the steel sheet, and the laser-matter interaction that occurs when and intense laser beam is tightly focused in the workpiece surface. It presents the influence of various factors affecting the textured workpiece performance together with the investigations into tribology of textured components. The paper also discusses these developments and some fundamental on future LST research.

Abstract: The potential of abrasive waterjet technology was investigated as a method to polish Z-blocks of synthetic quartz crystals. The polished surfaces were characterized by surface roughometer and scanning electron microscopy. The main factors affecting the surface roughness and the erosion mechanisms related to material removal were analysed. It is found that abrasive mesh, water pressure and jet incidence angle are the main factors affecting the surface roughness. By contrast, the influence of traverse speed on the surface roughness is small. Under certain controlled conditions, the erosion mechanisms of synthetic quartz crystals are plastic flow, leaving a crack-free surface by low-middle pressure micro abrasive waterjet.

Abstract: Cd1−xZnxTe (CZT) is an excellent ternary compound semiconductor. CZT is the most suitable substrate material for Hg1−yCdyTe epitaxial growth and can make the detector itself. The researchers have done a lot of works on the hard and brittle material removal mechanism in lapping process. however, no published articles are available regarding the removal mechanism and the abrasives embedding mechanism of the soft and brittle material in lapping progress .and there is its own characteristic if the hard abrasives machining the soft and brittle material in lapping progress, the objective of this paper is to build the physical model ,and divide the abrasive into four kinds of abrasives , they are two-body abrasive ,three-body abrasive ,embedded abrasive and small abrasive, and the authors analyze the effects on the material surface of the above abrasives. At last, design series of experiments, through analyzing the results and observe the surface morphology, the authors prove that the physical model is correct.

Abstract: A novel truing and dressing method, namely dry electrical discharge (dry-ECD) assisted truing and dressing, is proposed to overcome the shortcomings associated with conventional mechanical dressing methods, ELID and ECD methods. The macro/micro complex feed mechanism in dry –ECD assisted truing and dressing equipment is designed to maintain continuous discharge between the tool electrode and diamond wheel in dry-ECD automatically. A series of basic performance experiments of the micro feed mechanism show that the position accuracy of the micro-feed mechanism is below 0.35μm using the micro-positioning control system. Whereas，the position accuracy of the mobile negative electrode is 1μm without macro/micro complex feed mechanism.

Abstract: The grinding force was one of the most important parameters, almost related with all the parameters in grinding. In this paper, the grinding force model was established by a new method. The abrasive grains were analyzed using the statistical probability method. The abrasive grains were divided into two types, one was the cutting abrasive grain, and the other was contacting abrasive grain. The force analysis of a single abrasive grain was done. The grinding force model was established on the basis of the statistical probability method and the force analysis of a single abrasive grain. Theoretical analysis was verified by the experiment. The results indicated, the experimental results agree well with the theoretical prediction. The model can accurately predict the grinding force.

Abstract: Based on the kinematic analysis of the double sided polishing process, the equation of relative velocity (the workpiece to the polishing plate) is established. According to the Preston’s equation, the function of stock removal uniformity is presented. By computer simulations of the machining process, the effects of rotating speed ratios (the carrier revolution speed to plate rotating speed, carrier rotating speed to plate speed) on the stock removal uniformity are discussed in this paper. At last, some experiments have been done for validating the theoretical study of stock removal uniformity. The results show that, the computer simulation can estimate and conduct the experiment result in double-sided polishing process.

Abstract: Tungsten carbide which is a hard and brittle material was ground by cast-iron bonded diamond wheel with ELID (Electrolytic In-Process Dressing) technique, for the purpose of getting high efficiency, super-precision machining. Three kinds of cast-iron bonded diamond wheels with different grain size were adopted to get different grinding efficiency and surface quality of workpieces. The grinding properties of cast-iron bonded grinding wheels with different grain size and the ground surface quality of tungsten carbide are discussed in this paper. The experiment results indicate that, under the same feeding amount, the grinding efficiency of the wheel with bigger grain size is higher, and it could make the dimension accuracy of the workpiece controllable, but the wheel with smaller grain size could get better ground surface quality. The two grinding phases are decided by the ratio between the size of abrasive grain and the thickness of the oxide layer on the grinding wheel.

Abstract: Grinding forces, protrusion and wear of diamond grit have been studied in grinding granite with a single-layer brazed diamond wheel. The experiment results indicate that the primary wear progression of diamond grits in the whole grinding process follows the mode of whole, micro-fractured, macro-fractured and pull-out when grinding granite with the brazed diamond wheel. The proportions of the whole, fractured, pull-out, break flat and the mean height protrusion of grains are more closely related to grinding forces. The grinding forces decreased with the increasing proportions of whole and break flat grains, and the tangential and normal force components increased with the gradual wear of the brazed diamond wheel during a long-time grinding process.