Polishing Behavior and Surface Quality of Alumina and Alumina/Silicon Carbide Nanocomposites

The response of Al₂O₃ and Al₂O₃/SiC nanocomposites to lapping and polishing after initial grinding was investigated in terms of changes in surface quality with time for various grit sizes. The surface quality was quantified by surface roughness ( R _a ) and by the relative areas of smooth polished surfaces as opposed to rough as-ground areas. Polishing behavior of the materials was discussed in terms of SiC content and grain size. It was concluded that nanocomposites are more resistant to surface damage than Al₂O₃, and this behavior does not depend on the amount of SiC in the range 1–5 vol%. SiC addition ≥1 vol% is enough to produce a noticeable improvement in surface quality during lapping and polishing.     

A comparison of mechanical lapping versus chemical-assisted mechanical polishing and planarization of chemical vapor deposited (CVD) diamond

Polishing and planarization of CVD diamond substrates are essential steps in the processing of synthetic diamond for applications in the semiconductor industry. Using the methods of mechanical lapping and chemical-assisted mechanical polishing (CAMP), CVD diamond samples were polished against a cast-iron scaife and an alumina plate, respectively, using the same pressure on the samples. A diamond slurry was used in the mechanical lapping process, and a heated liquid chemical was used in a patented chemical-assisted mechanical polishing and planarization (CAMPP) process. The diamond samples were analyzed at several time intervals during the lapping and polishing processes, and during a combination of the two processes in which mechanical lapping preceded CAMPP. The polishing rate and surface characteristics of the diamond samples were the primary analytical measurements made, and the data were used to compare the relative lapping/polishing efficiencies of the two processes in an effort to develop an optimized process for producing highly polished CVD diamond substrates.     

Study of Optical Glass Surfaces by Leaching with Nitric Acid: I, Polishing Lines

A study was made of the origin of fine lines that appeared on polished glass surfaces after leaching with nitric acid. The results were considered on the basis of theories of nonreflecting films and the polishing lines developed by hydrofluoric acid etching. The conclusions reached are compatible with the existence of deep fields of compression where the ionic exchange is enhanced.     

Diamond surfaces polished both mechanically and manually; an atomic force microscopy (AFM) study

Diamond surfaces that are polished both mechanically and manually have been studied using atomic force microscopy and compared with optical micrographs obtained within the Nomarski interference mode. The extra gentle manual polishing which follows the mechanical polishing was developed to produce much smoother, well characterized and flat diamond surfaces than those prepared through mechanical polishing only. Both the AFM and optical micrographs showed the manually polished diamond surfaces being smoother and also exhibiting lower roughness parameters than those polished mechanically only. Annealing the surfaces to 250 °C did not show any noticeable changes in the surface roughnesses, but a 750 °C vacuum-anneal did show some differences that were attributed to possible surface etching through the desorption of the surface-bonded species.     

Effect of polishing method on surface roughness and bacterial adhesion of zirconia-porcelain veneer

The purpose of this study was to evaluate the effect of various polishing methods on surface roughness of zirconia-porcelain veneer and to correlate the findings with early bacterial adhesion. The study specimens were glazed (control group), glazed after fine polishing (glazed group) and polished with Exa Cerapol (Cerapol group) or with Shofu porcelain adjustment kit (Shofu group) (n =20). Surface roughness was then measured using profilometer and scanning electron microscope (SEM). After artificial saliva coating, the specimens were incubated in Streptococcus mitis suspension for 4 h at 37 °C. Adherent bacteria were quantified from SEM images. Streptococcal viability was assessed by LIVE/DEAD staining kit and fluorescent microscope. There were significant differences in surface roughness according to polishing method and surface material. Relatively smoother surfaces were found in zirconia surfaces and glazed porcelain surfaces. There were also significant differences in bacterial adhesion according to polishing method and surface material. Cerapol group showed minimal bacterial adhesion with more dead cells when compared to other groups. A positive correlation between surface roughness and bacterial adhesion was found in glazed porcelain surface and a negative correlation in zirconia surface of Cerapol group, both with no statistical significance. Within the limitations of in vitro study, surface roughness and bacteria adhesion were significantly influenced by polishing method and surface material. Also, there was a positive correlation and negative correlation between surface roughness and bacterial adhesion in glazed porcelain surface and in zirconia surface of Cerapol group, respectively.     

撞击流反应制取“超细”白炭黑

用反应-沉淀法制取超细固体产物最重要的条件之一是高且均匀的过饱和度环境.在有关撞击流性质研究的基础上，研发了浸没循环撞击流反应器(SCISR).它具有全混流-无混合流串联循环的特殊流动结构和撞击区微观混合强烈的特点.后者可以创造高且均匀的过饱和度，产生大量晶核；低过饱和度的无混合区有利于微晶表面稳定和钝化.利用该反应器进行普通沉淀法制取“超细”白炭黑的实验研究，确定了最优操作条件，并与传统的搅拌槽反应器(STR)进行了比较.SCISR可以半间歇或连续操作.制得产品粒径范围0.5～2.0μm，平均粒径1.1～1.6μm，比STR产品细、粒径分布窄.反应产物干燥实验结果表明后处理过程中粒径稳定，不发生微细颗粒并聚.     

H2O2-草酸体系化学抛光不锈钢的研究

采用H2O2-草酸体系在室温条件下对不锈钢制品抛光,讨论了抛光液各组分、抛光温度及抛光时间对抛光效果的影响.实验发现:该抛光液对不锈钢在适宜条件下均可得到满意的抛光效果.     

手工抛光塑料模具的型腔

叙述了手工抛光塑料模具型腔的要点，包括对被抛光模具型腔的材料及处理的具体要求，以及粗磨，细磨，粗抛，精抛和操作注意事项。     

Preparation of a coal surface for contact angle measurements

Coal specimens of different ranks were polished using silicon carbide abrasive papers (with a grit from #60 to #1200) and alumina powder of varying size (from 5 to 0.05 μm). The coal surface roughness and contamination (by alumina powder) were examined with both scanning electron microscopy and atomic force microscopy. The water advancing and receding contact angles were measured on such surfaces by varying the bubble size, using the captive-bubble technique. It was found that silicon carbide paper abraded all components of the coal surface, i.e. both organic and inorganic matter, to a similar depth. The roughness of the coal surface due to polishing with silicon carbide abrasive papers affected the contact angle hysteresis and the contact angle vs. bubble size relationship. Polishing of coal specimens with alumina powder reduced the microroughness of the coal surface but produced rough features at the macro level and caused mineral inclusions rising above the smooth organic matter. This phenomenon results from the heterogeneity of coal specimens consisting of minerals and macerals with different hardness values. The roughness at the macro level was easily distinguishable and had a significant impact on the measured contact angles when the coal surface was polished with coarse alumina powders, 5 and 1 μm in diameter. The effect of surface roughness on the advancing and receding water contact angles was significantly reduced (if not completely eliminated) when the coal surface was polished with a fibrous cloth (CHEMOMET) in the final step, after having been polished with 0.05 (0.06) μm alumina powder. Microscopic observation of the coal surfaces revealed that an appropriate ultrasonic treatment (8-10 min in an ultrasonic bath filled with water) and mechanical cleaning (polishing with a CHEMOMET cloth) of coal samples were required to remove the alumina particles left on the surface due to the previous polishing procedure. An improved methodology for coal surface preparation, prior to contact angle measurements, as proposed in this paper, includes polishing with a series of abrasive papers and 0.05 (0.06) μm alumina powder, polishing and cleaning with a fibrous cloth (e.g. CHEMOMET), and, finally, an extended cleaning in an ultrasonic bath filled with water.     

Molecular dynamics simulation of SiC removal mechanism in a fixed abrasive polishing process

Precision polishing of mono-crystalline SiC wafers on a fixed abrasive pad is investigated by double-nano-abrasives cutting at micro/nano scale in this report. Prior to this report, a single abrasive approach in molecular dynamics simulation had been employed to illustrate the material removal mechanism in SiC polishing process, which is quite different from the real situation of the fixed abrasive polishing process. Cutting depth and spacing of abrasive particles in a fixed abrasive pads were tested to gain insights on phase transformation, subsurface damage, surface quality, material removal and friction characteristics of polished SiC wafers by molecular dynamics simulation. By following the coordination number and radial distribution function, we clearly see that the number of phase transformation atoms caused by cutting and abrasion increases with the cutting depth of nano-abrasives on the surface of SiC workpiece. Simulation results also suggest that the phase transformation of the SiC crystal phase increases with the lateral spacing of abrasive particles in pads, while does not change much with the increase of the longitudinal spacing. It is also found that the deeper the abrasive cutting depth, the deeper subsurface damage, resulting more materials’ removal from SiC workpiece. The lateral and longitudinal abrasive spacings lead to little change the depth of subsurface damage on the wafer in MD simulation for a fixed double abrasive polishing. The surface roughness is better with the larger lateral abrasive spacing, but no clear correlation with the longitudinal abrasive spacing.     

Mechanism and Simulation of Removal Rate and Surface Roughness During Optical Polishing of Glasses

Glass optics with ultra‐low roughness surfaces (<2 Å rms) are strongly desired for high‐end optical applications (e.g., lasers, spectroscopy, etc.). The complex microscopic interactions that occur between slurry particles and the glass workpiece during optical polishing ultimately determine the removal rate and resulting surface roughness of the workpiece. In this study, a comprehensive set of 100 mm diameter glass samples (fused silica, phosphate, and borosilicate) were polished using various slurry particle size distributions (PSD), slurry concentrations, and pad treatments. The removal rate and surface roughness of the glasses were characterized using white light interferometry and atomic force microscopy. The material removal mechanism for a given slurry particle is proposed to occur via nano‐plastic deformation (plastic removal) or via chemical reaction (molecular removal) depending on the slurry particle load on the glass surface. Using an expanded Hertzian contact model, called the Ensemble Hertzian Multi‐gap (EHMG) model, a platform has been developed to understand the microscopic interface interactions and to predict trends of the removal rate and surface roughness for a variety of polishing parameters. The EHMG model is based on multiple Hertzian contacts of slurry particles at the workpiece–pad interface in which the pad deflection and the effective interface gap at each pad asperity height are determined. Using this, the interface contact area and each particle's penetration, load, and contact zone are determined which are used to calculate the material removal rate and simulate the surface roughness. Each of the key polishing variables investigated is shown to affect the material removal rate, whose changes are dominated by very different microscopic interactions. Slurry PSD impacts the load per particle distribution and the fraction of particles removing material by plastic removal. The slurry concentration impacts the areal number density of particles and fraction of load on particles versus pad. The pad topography impacts the fraction of pad area making contact with the workpiece. The glass composition predominantly impacts the depth of plastic removal. Also, the results show that the dominant factor controlling surface roughness is the slurry PSD followed by the glass material's removal function and the pad topography. The model compares well with the experimental data over a variety of polishing conditions for both removal rate and roughness and can be extended to provide insights and strategies to develop practical, economic processes for obtaining ultra‐low roughness surfaces while simultaneously maintaining high material removal rates.     

The reliability of polished porcelain stoneware tiles

The flexural strength and the Young’s modulus of as fired and polished porcelain stoneware tiles were investigated. Bending tests were carried out on suitable specimens, cut from five commercial products before and after polishing. The differences found in the flexural strength data were evaluated by the analysis of variance and the determination of the Weibull parameters. The results showed that: (i) the as fired tiles and the corresponding polished tiles cannot be always considered the same material and (ii) the data scattering is usually greater for the polished products, i.e., the reliability of the polished products, in terms of the Weibull modulus m, decreases. The results, supported by microstructural observations, surface roughness and Vickers hardness measurements, were directly attributed to the severe damage induced by the first step of machining, i.e., calibrating or grinding. Young’s modulus data showed a clear dependence on the pre-existing porosity, i.e., the production process, rather than on the machining induced damage. It was also shown that the conditions and the characteristics of the polished working surfaces strongly depend on the microstructure of the as fired material.     

Chemistry and Formation of the Beilby Layer During Polishing of Fused Silica Glass

The chemical characteristics and the proposed formation mechanisms of the modified surface layer (called the Beilby layer) on polished fused silica glasses are described. Fused silica glass samples were polished using different slurries, polyurethane pads, and at different rotation rates. The concentration profiles of several key contaminants, such as Ce, K, and H, were measured in the near surface layer of the polished samples using Secondary Ion Mass Spectroscopy (SIMS). The penetration of K, originating from KOH used for pH control during polishing, decreased with increase in polishing material removal rate. In contrast, penetration of the Ce and H increased with increase in polishing removal rate. In addition, Ce penetration was largely independent of the other polishing parameters (e.g., particle size distribution and the properties of the polishing pad). The resulting K concentration depth profiles are described using a two‐step diffusion process: (1) steady‐state moving boundary diffusion (due to material removal during polishing) followed by (2) simple diffusion during ambient postpolishing storage. Using known alkali metal diffusion coefficients in fused silica glass, this diffusion model predicts concentration profiles that are consistent with the measured data at various polishing material removal rates. On the other hand, the observed Ce profiles are inconsistent with diffusion based transport. Rather we propose that Ce penetration is governed by the ratio of Ce–O–Si and Si–O–Si hydrolysis rates; where this ratio increases with interface temperature (which increases with polishing material removal rate) resulting in greater Ce penetration into the Beilby layer. Calculated Ce surface concentrations using this mechanism are in good agreement to the observed change in measured Ce surface concentrations with polishing material removal rate. These new insights into the chemistry of the Beilby layer, combined together with details of the single particle removal function during polishing, are used to develop a more detailed and quantitative picture of the polishing process and the formation of the Beilby layer.     

Preparations of silica slurry for wafer polishing via controlled growth of commercial silica seeds

Silica slurry in aqueous medium for wafer polishing was prepared by sol-gel reaction of silicon alkoxide utilizing commercial silica particles as seeds that were grown stepwise through intermittent additions of tetraethylorthosilicate (TEOS) as a silica precursor. Before the growth reaction, the commercial silica particles were pre-treated in the vibratory mill partially filled with zirconia ball and the sonicator to ensure good dispersion. The alcohol left after growth reaction was removed by vacuum distillation and repeated washings with distilled water followed by centrifugations. Then, the alcohol-free silica particles were redispersed in water. The dispersion stability of the silica slurries was examined by measuring surface charge of silica particles and rheological properties. Finally, wafer-polishing performance of the prepared silica slurries was considered by measuring the polishing (or removal) rate, and RMS (root mean square) roughness of the polished wafer surface. For the polishing, MEA (monoethanolamine) and TMAH (tetramethylammonium hydroxide) were used as polishing accelerators. The polishing result showed that the removal rate was nearly independent of the concentrations of MEA and TMAH in the range of 0.3-0.5 wt% and 100-500 ppm, respectively. One of the most interesting features is that hydrothermal treatment of the prepared silica slurries in autoclave increased the removal rate as high as ten times. Although the removal rate was increased by the increased size of the abrasive particle, surface roughness of the polished wafer surface was deteriorated.     

Microstructural Features and Dislocations on Thermally Etched Sapphire Surfaces

Basal-, prism-, and rhombohedral-plane specimens cut and polished from flame-grown sapphire boules developed fine surface textures during heat-treatment in the range 1700° to 1900°C. Microscopic examinations of such surfaces revealed low-angle grain boundaries, dislocations, and other crystal imperfections. Thermally etched textures apparently were generated by three overlapping processes, namely annealing, etching, and decoration. Thermal etching gave evidence of high-temperature relaxation of residual strain energy introduced at low temperature (analogous to cold work in metals), including that introduced by fracture, microindentation, and cutting and polishing during surface preparation.     

Preparation of polyurethane foam fine polishing wheel for stainless steel surface

Comparing with dry polishing, the wet-polishing of the stainless steel surface can significantly reduce dust, noise and other pollution, and improve the polished quality. Thus, it is important to develop new polishing tools. In this work, the effects of the foaming agent and diluents on the mechanical properties of the polyurethane foam (PUF) system were investigated, and then the effect of the filler of graphite on the structure and mechanical properties of PUF was studied. Furthermore, the PUF fine polishing wheel with aluminum oxide was prepared. Results show that the bi-component diluents combined cyclohexane and dimethylformamide significantly affects the porosity and hardness of the PUF matrix. The filler of graphite can decrease the mechanical properties of the polyurethane matrix and increase the porosity of PUF, consequently, improve the self-sharpening of the PUF polishing wheel. The PUF fine polishing wheel with aluminum oxide shows fine polishing performance.     

Mechanochemical Polishing of Silicon Nitride

Two oxides of iron, Fe₂O₃ and Fe₃O₄, were identified as suitable soft abrasives for mechanochemical polishing of Si₃N₄. Removal rates up to 1.6 μ.m /h were observed when hot-pressed Si₃N₄ samples were mechanochemically polished using these abrasives on a linen plastic lap. The polished surfaces were flat and scratch-free, with a peak-to-valley roughness of <20 nm. Auger electron spectroscopy of these surfaces revealed a thin layer (≤10 nm) of a silicon oxynitride that contained carbon and ∼0.5 at.% iron.     

沥青中间相的光反射显微分析方法优化

对沥青样品采用冷镶嵌树脂成型,用自动磨抛机配不同粒级防水砂纸对成型样品多次研磨、抛光;将待测样品在反射式偏光显微镜下观察、测量,采用面积百分比法测得中间相含量。可避免计数法中间相粒径的影响,分别测量不同粒级中间相的比例。     

金刚石固结磨料研磨K9玻璃的研究

为提高光学材料的研磨效率与质量,提出一种亲水性固结磨料研磨方法.采用图形转移与UV固化工艺,将粒径为5～10 μm的金刚石磨料固结于亲水性光固化树脂中,制备固结磨料研磨抛光垫(FAP).选取工件的材料去除率(MRR)和表面粗糙度(Sa)来评价研磨的加工性能.对比研究了在相同粒径磨粒下的游离磨料研磨、固结磨料丸片研磨、及亲水性FAP研磨三种不同方法对K9光学玻璃的加工性能.实验结果表明:采用FAP研磨K9玻璃,MRR为350 nm/min,表面粗糙度Sa为3.24 nm,达到了精研的加工效率和抛光的表面质量.提出了固结磨料抛光丸片和亲水性FAP的加工模型,以及亲水性FAP的自修整机理.