Papers by Author: Yi Qing Chen

Abstract: This paper investigates the applicability of the dynamic friction polishing (DFP) technique to process the chemical vapour deposition (CVD) diamond surfaces. Two types of CVD diamond specimens were studied. A stepwise polishing process was introduced to minimise the cracking in CVD thin films. The investigation focused on the polished surface quality in relation to the polishing conditions and material remove rates. It was found that by selecting proper polishing parameters, surfaces of quality finish with a roughness of less than 70 nm Ra could be obtained in 15 minutes when the specimens were CVD diamond wafers with an initial roughness of 17 μm. The polishing time could be reduced to only 2.5 minutes in the case of diamond thin film specimens of initial roughness of 1.6 μm.

Abstract: This paper reports the specimen preparation using an advanced dual beam focused ion beam (FIB) technique for bulk polycrystalline diamond (PCD) composites after dynamic friction polishing (DFP). The technique adapted allows for precisely processing diamond materials at the specific polishing track sites of PCD surface, from which large cross-sectional specimens for SEM/EDS/Raman microanalysis could be successfully created. In addition, an in-situ lift-out method was developed to prepare the site-specific HRTEM specimens which were thin enough for imaging the atomic lattice of diamond and for conducting EELS analysis.

Abstract: With the aid of the Raman spectroscopy, this paper investigates the phase transformation and residual stress distribution in surfaces of polycrystalline diamond composites polished by dynamic friction technique. To clarify the contribution of phase transformations to residual stresses, the study focused on the surface which was incompletely polished such that the transformed phases remained. It was found that amorphous non-diamond carbon and amorphous graphite phase appeared in grain boundaries, but pristine diamond phase was predominant within gain areas. The residual stresses vary across the polished surfaces and the maximum stress locates at the grain boundaries.

Abstract: This paper investigates the polishing of single crystal diamond using the dynamic friction method. It was found that by selecting a proper polishing pressure and sliding speed, a very high polishing rate at 10,300 µm/h (or 2.8 X 10-2 mg/s) with a high quality surface finish can be reached, which is hundreds times faster than the other polishing process reported in the literature. This method can be used to manufacture diamond products and to repair worn diamond components such as diamond cutting tools and diamond dressers for grinding wheels.

Abstract: This paper investigates the effect of tool and workpiece motions on the machining efficiency in the fabrication of hip joint prosthesis. The finite element method was used to characterize the three-dimensional motion of the system, using the uniformity or even distribution of a cutting tool tip trajectory as an efficiency indicator. It was found that a proper combination of the rotational speeds of a cutting tool and a workpiece can improve significantly the efficiency of the machining operation.