Doctor of Philosophy (PhD) / This thesis aims to establish a sound scientific methodology for the effective and efficient polishing of thermally stable PCD composites (consisting of diamond and SiC) for cutting tools applications. The surface roughness of industrial PCD cutting tools, 0.06 μm Ra is currently achieved by mechanical polishing which is time consuming and costly because it takes about three hours to polish a 12.7 mm diameter PCD surface. An alternative technique, dynamic friction polishing (DFP) which utilizes the thermo-chemical reactions between the PCD surfaces and a catalytic metal disk rotating at high peripheral speed has been comprehensively investigated for highly efficient abrasive-free polishing of PCD composites. A special polishing machine was designed and manufactured in-house to carry out the DFP of PCD composites efficiently and in a controllable manner according to the requirements of DFP. The PCD polishing process and material removal mechanism were comprehensively investigated by using a combination of the various characterization techniques: optical microscopy, SEM and EDX, AFM, XRD, Raman spectroscopy, TEM, STEM and EELS, etc. A theoretical model was developed to predict temperature rise at the interface of the polishing disk and PCD asperities. On-line temperature measurements were carried out to determine subsurface temperatures for a range of polishing conditions. A method was also developed to extrapolate these measured temperatures to the PCD surface, which were compared with the theoretical results. The material removal mechanism was further explored by theoretical study of the interface reactions under these polishing conditions, with particular emphasis on temperature, contact with catalytic metals and polishing environment. Based on the experimental results and theoretical analyses, the material removal mechanism of dynamic friction polishing can be described as follows: conversion of diamond into non-diamond carbon takes place due to the frictional heating and the interaction of diamond with catalyst metal disk; then a part of the transformed material is detached from the PCD surface as it is weakly bonded; another part of the non-diamond carbon oxidizes and escapes as CO or CO2 gas and the rest diffuses into the metal disk. Meanwhile, another component of PCD, SiC also chemically reacted and transformed to amorphous silicon oxide/carbide, which is then mechanically or chemically removed. Finally an attempt was made to optimise the polishing process by investigating the effect of polishing parameters on material removal rate, surface characteristics and cracking /fracture of PCD to achieve the surface roughness requirement. It was found that combining dynamic friction polishing and mechanical abrasive polishing, a very high polishing rate and good quality surface could be obtained. The final surface roughness could be reduced to 50 nm Ra for two types of PCD specimens considered from pre-polishing value of 0.7 or 1.5 μm Ra. The polishing time required was 18 minutes, a ten fold reduction compared with the mechanical abrasive polishing currently used in industry.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available online.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

The Chemical Mechanical polishing (CMP) process is now widely employed in the Integrated Circuit Fabrication. However, due to the complexity of process parameters on the material removal rate (MRR), mechanism of material removal and pattern effect are not well understood. In this paper, three contact regimes between the wafer surface and the polishing pad were proposed: direct contact, mixed or partial contact, and hydroplaning. The interfacial friction force has been employed to characterize these contact conditions. Several polishing models are reviewed with emphasis on the mechanical aspects of CMP. Experiments have been conducted to verify the mechanical polishing models and to identify the dominant mechanism of material removal under typical CMP conditions. / Singapore-MIT Alliance (SMA)

Aggregate properties influence different aspects of asphalt pavement performance. Aggregate polishing characteristics are directly related to pavement surface frictional properties and thus to skid resistance. Aggregate resistance to degradation (abrasion and breakage) is another important property that influences pavement performance. Aggregate degradation could take place during production due to plant operations and during compaction, leading to change in aggregate characteristics and mix properties. In addition, aggregate resistance to degradation is important in mixes such as Stone Matrix Asphalt (SMA) and Open Graded Friction Course (OGFC) that rely on stone-to-stone contacts among coarse aggregates. Some aggregates in these mixes fracture due to the high stresses at contact points. Many test methods exist for measuring aggregate polishing and degradation, but a critical review of these methods reveals that they suffer from being time consuming, are unable to differentiate between aggregates with distinct resistance to polishing, or unable to differentiate between aggregate resistance to abrasion and breakage. New methodologies are needed to give better assessment of aggregate resistance to polishing, abrasion, and breakage. The thesis presents the development of new methods for measuring aggregate resistance to polishing, abrasion, and breakage. These methods rely on measurements using the Aggregate Imaging System (AIMS) and Micro-Deval. The new method for measuring aggregate resistance to polishing monitors change in aggregate texture as a function of polishing time. As such, it provides the initial texture, rate of polishing, and final texture. The new method for measuring aggregate degradation is capable of distinguishing between breakage and abrasion. In this method, abrasion is defined as the reduction in aggregate angularity, while breakage is defined by fracture of particles. The new methods are shown to be rapid and accurate, and they require reasonable training. Since both AIMS and Micro-Deval are used in the new methods, it was necessary to evaluate the repeatability of these two methods. Measurements using two AIMS units and two Micro-Deval machines were used to assess the variability. There was no statistical difference between the measurements of the two AIMS units or between the measurements of the two Micro-Deval units.

In this work, membrane set(s) had been incorporated into different crossflow electrofiltration (CEF) /electrodialysis (ED) treatment modules for treating various CMP wastewaters and simultaneously generating two streams of electrolytic ionized water (EIW). In general, CMP wastewaters have high alkalinity, turbidity, total solids content and silica content. In this investigation, CMP wastewaters were obtained from two wafer fabs in Taiwan and characterized by various standard methods. Then they were treated by the aforementioned treatment modules. Experiments were carried out based on the fractional factorial design and the L8 orthogonal arrays of the Taguchi method. Experimental factors such as electric field strength, transmembrane pressure for CEF, etc. were used to investigate their effects on the permeate qualities (i.e., oxidation-reduction potential, pH, etc.). According to the results of analysis of normal probability plots, analysis of variance (ANOVA) and regular analysis, the electric field strength was presumed to be a very significant parameter. Experimental results showed that filtrate flux increased with the increasing applied electric field strength. The permeate has a turbidity of below 1 NTU, TOC of below 3 mg/L, and TDS of below 250 mg/L under various operating conditions. Other permeate qualities were 15~22 mg/L of K, 53~68 mg/L of silica, 2~4 mg/L of NH4+ and 134~680 £gS/cm of electrical conductivity. But the values of electrical conductivity, pH, and oxidation-reduction potential (ORP) varied substantially for the anolyte EIW and catholyte EIW. Using these novel treatment modules, the optimal ORP and pH values of the anolyte EIW were 211.8 mV, 4.52 and 214.1 mV, 4.83, respectively, for single- and multi-membrane sets. The optimal ORP and pH values of the catholyte EIW were -165.0 mV, 11.21 and -172.0 mV, 10.81, respectively, for single- and multi-membrane sets. It is clear that permeate obtained in this study is suitable for high-level recycling. To further upgrade the water quality of permeate obtained above, a reverse osmosis (RO) unit was added to the treatment system. The water quality of silica for post-RO permeate were decreased from 53.7 to 0.98 mg/L for the anolyte EIW and from 68.05 to 1.32 mg/L for the catholyte EIW. The removal rates of Na and K by the RO unit were not significant. In addition, other unique properties of EIW (e.g., pH, ORP, and cluster size of water molecules) remained almost the same in post-RO permeate. The total recovery rate of the treated water could be above 85%. Therefore, the treated water at this stage could be reused as the cleaning media for the wafer surfaces or reused for the DI water production apparatus.

This study is to investigate that the polishing behavior will be independent of or dependent on the direction of particle motion by the anisotropic polishing phenomenon of hydrodynamic polishing process under the semi-contact lubricating condition. There are two types of experiments to be examined to get to the objectives. First, taking polishing on the work surface which possesses the isotropic surface roughness, to discuss the variation of the smoothing efficiency of the surface irregularities in the five different directions on the work surface. Second, taking three kinds of polishing, ¡§longitudinal, transverse, and oblique roughness polishing¡¨, on the work surface which possesses the anisotropic surface roughness. Then to discuss the variation of the smoothing efficiency of the surface irregularities on the work surface. Both the results of two types experiments should be take to distinguish the difference between one smoothing efficiency and the others from using the hypothesis testing. All hypothesis tests about the experiment results of the work piece which possesses the isotropic surface roughness are accepting . But, most hypothesis tests about the experiment results of the work piece which possesses the anisotropic surface roughness are rejecting . The theory analysis about the smoothing efficiency is discussing. The discussion about the smoothing efficiency can explain the phenomenon due to taking polishing on the work surface which possesses the anisotropic surface roughness. The reason why the phenomenon happened is possible the effects of different lubrication condition. Last, from the lubrication theory, the effects of different lubrication condition due to different surface texture can be employed to verify the explanation about the phenomenon is suitable. The conclusion from the experiment results and the theory analysis is: the polishing behavior is possible independent of the direction of particle motion by the anisotropic polishing phenomenon of hydro- dynamic polishing process under the semi-contact lubricating condition.

In the study, the effects of the machining conditions, ex, machining positions, loads and rotating speed ratio on machining mechanism of wafer are investigated by using the continuous composite electroplated polisher and find the best machining conditions of the polisher. Experimental results show that when the wafer and polisher are full contact, the operating of machinery is most smooth and the flatness is better. When the load is increased, the reducing rate of average roughness¡]Ra¡^and maximum roughness¡]Rmax¡^, removal rate, and the speed of mirror degree are increased. The machining mechanism and the stability of machinery is depended on the value of rotating speed ratio. In the different rotating speed ratio, the flatness of wafer is difference. For example, the rotating speed ratio is 1, the flatness is 1.5 £gm/38 mm. The rotating speed ratio is 2, the flatness is 2.3 £gm/38 mm. Finally, choose the rotating speed ratio, which the values of rotating speed are close and complex on the range of rotating speed which machinery can be operating most stable in machining process. Because of the machining mechanism are similar and the grinding locus are finer. Hence, the flatness of wafer becomes better. When the rotating speed ratio is 1.1, the flatness is 1.46£gm/38 mm. The rotating speed ratio is 1.11, the flatness is 1.45£gm/38 mm. The effect of the rotating speed ratio of the wafer and polisher on the grinding locus type of grinding surface is theoretically analyzed. Results show that when the rotating speed ratio is irregular, the distribution of grinding locus becomes finer. The analyzable results of locus and provable results of experiment are the same.

The ultimate value of surface roughness and its characteristic for the polishing process was investigated in this thesis. To find out the nature of ultimate surface roughness by means of the hydrodynamic polishing process and can be used for all polishing method. A preliminary mathematical model that was proposed to explain the ultimate surface roughness proceedings and a series of experiments was planed to verify suitable of this model. Starting with the rule for ultimate surface roughness happened. The assumption that abrasive particle at roughness peak and valley machining capability differ less than one atom, the ultimate surface roughness be attained. We can propose the mathematical model of ultimate surface roughness based on this rule and the previous study of hydrodynamic polishing process. Following by useing the computer simulation to help us exploring ultimate surface roughness characteristic and testing experiments fit for the forecasting. Finally, we explain reasons that cause the experiment results not agree with the model anticipation and propose better lubrication condition to polish the optimum surface.

Aggregate properties influence different aspects of asphalt pavement performance. Aggregate polishing characteristics are directly related to pavement surface frictional properties and thus to skid resistance. Aggregate resistance to degradation (abrasion and breakage) is another important property that influences pavement performance. Aggregate degradation could take place during production due to plant operations and during compaction, leading to change in aggregate characteristics and mix properties. In addition, aggregate resistance to degradation is important in mixes such as Stone Matrix Asphalt (SMA) and Open Graded Friction Course (OGFC) that rely on stone-to-stone contacts among coarse aggregates. Some aggregates in these mixes fracture due to the high stresses at contact points. Many test methods exist for measuring aggregate polishing and degradation, but a critical review of these methods reveals that they suffer from being time consuming, are unable to differentiate between aggregates with distinct resistance to polishing, or unable to differentiate between aggregate resistance to abrasion and breakage. New methodologies are needed to give better assessment of aggregate resistance to polishing, abrasion, and breakage. The thesis presents the development of new methods for measuring aggregate resistance to polishing, abrasion, and breakage. These methods rely on measurements using the Aggregate Imaging System (AIMS) and Micro-Deval. The new method for measuring aggregate resistance to polishing monitors change in aggregate texture as a function of polishing time. As such, it provides the initial texture, rate of polishing, and final texture. The new method for measuring aggregate degradation is capable of distinguishing between breakage and abrasion. In this method, abrasion is defined as the reduction in aggregate angularity, while breakage is defined by fracture of particles. The new methods are shown to be rapid and accurate, and they require reasonable training. Since both AIMS and Micro-Deval are used in the new methods, it was necessary to evaluate the repeatability of these two methods. Measurements using two AIMS units and two Micro-Deval machines were used to assess the variability. There was no statistical difference between the measurements of the two AIMS units or between the measurements of the two Micro-Deval units.