Polishing Tests Research Articles

The Effect of Sodium Hexametaphosphate on the Dispersion and Polishing Performance of Lanthanum-Cerium-Based Slurry.

A lanthanum-cerium-based abrasive composed of CeO2, LaOF, and LaF3 was commercially obtained. The effect of sodium hexametaphosphate (SHMP) on powder dispersion behavior was systematically investigated using the combined techniques of liquid contact angle, turbidity, zeta potential (ZP), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) combined with Rietveld refinements, X-ray photoelectron spectroscopy (XPS), and polishing tests. The results indicated that the addition of 0.5 wt.% SHMP dispersant to the 5 wt.% lanthanum-cerium-based slurry produced the most stable suspension with a high turbidity of 2715 NTU and a low wetting angle of 45°. The as-obtained slurry displayed good surface polishing quality for K9 glass, with low surface roughness (Ra) of 0.642 and 0.515 nm (in the range of 979 × 979 μm2) at pH = 6 and 11, respectively, which corresponds to the fact that it has local maximum absolute values of ZP at these two pH values. SEM images demonstrated that after appropriate grafting of SHMP, the particle aggregation was reduced and the slurry's dispersion stability was improved. In addition, the dispersion mechanism was explained based on the principle of complexation reaction, which reveals that the dispersant SHMP can increase the interparticle steric hindrance and electrostatic repulsions. In an acidic environment, steric hindrance dominates, while electrostatic repulsion prevails under alkaline conditions. As expected, this polishing slurry may find potential applications in manufacturing optical devices and integrated circuits.

Determination of Total Aflatoxins in Polished Rice by Liquid Chromatography-Fluorescence Detection with Multifunctional Column Cleanup and Precolumn Derivatization: Single-Laboratory and Inter-Laboratory Validation Studies.

Aflatoxins are toxic metabolites produced by Aspergillus spp. Because aflatoxins are potent carcinogens in humans and animals, many countries have set regulatory limits for aflatoxins in foods to prevent dietary exposure. From a global food safety perspective, in 2023, the Codex Alimentarius Commission established the maximum level (ML) of total aflatoxins in certain cereals and cereal-based products, including polished rice. Therefore, validated analytical methods for aflatoxin detection are necessary. In this study, a high performance liquid chromatography (HPLC)-fluorescence method coupled with multifunctional column clean-up and trifluoroacetic acid derivatization was developed for the determination of aflatoxin levels in polished rice. Our method was validated in a single laboratory study using aflatoxin-spiked materials, followed by an inter-laboratory validation study. Twelve laboratories participated in the inter-laboratory validation study, and five polished rice test samples artificially contaminated with aflatoxins were analyzed. In a single laboratory study, the ranges of mean recoveries of aflatoxin B1, B2, G1, G2, and total aflatoxins were 101%, 100-103%, 93-96%, 95-98%, and 97-99%, respectively. The relative standard deviations for within-day and between-day variations were all ≤ 4.4%. In the inter-laboratory validation study, the relative standard deviations for repeatability and reproducibility were from 0.7 to 2.7% and 3.3 to 8.9% for all analytes, respectively. In response to the Codex ML and method performance criteria for aflatoxins in polished rice, an analytical method based on HPLC-fluorescence detection was developed. All method performance parameters estimated from the testing results of the single-laboratory and inter-laboratory validation studies met the criteria required by the Codex. Single- and inter-laboratory studies for the validation of an analytical method for aflatoxin level determination in polished rice were successfully performed. This analytical method will be suitable to determine aflatoxin levels around the Codex ML set for polished rice.

A laboratory investigation for assessing the effectiveness of wastewater treatment using flocculation process in building stone processing industry on stone surface quality and abrasive tool wear

In this study, the effect of presence and concentration of two synthetic polymeric flocculants with different charging mechanisms (anionic and cationic) on surface quality and abrasive tool wear in polishing process of building stones was investigated. The polishing tests were performed in laboratory scale on two stone samples (granite and marble). An index, entitled improvement index (I) was defined for evaluating the effectiveness of flocculants on surface quality and abrasive tool wear. The results revealed that flocculation process had a noticeable effect on enhancement of surface quality and reduction of abrasive tool wear for both stone samples. The cationic flocculant was more effective for granite sample and anionic flocculant was more effective for marble sample. The granite particles mainly exhibit negative surface charge while the marble particles have positive surface charge in the pH range of wastewater used for polishing tests. Therefore, charge neutralization mechanism plays a major role in flocculation process of granite and marble samples. It was found that the use of flocculation process for treatment of wastewater in stone processing plants leads to increase of abrasive tool lifespan and more high-quality products.

Processing Optimization for Halbach Array Magnetic Field-Assisted Magnetic Abrasive Particles Polishing of Titanium Alloy.

To extend the working life of products made of titanium alloy, it is necessary to improve the polishing method to diminish the remaining defects on the workpiece surface. The Halbach array-assisted magnetic abrasive particle polishing method for titanium alloy was employed in this work. The distribution of magnetic field strength was simulated and verified at first to learn the characteristics of the Halbach array used in this work. Then, the polishing performance of the polishing tool was studied by conducting the polishing test, which aimed to display the relationship between shear force and surface roughness with polishing time, and the surface morphology during polishing was also analyzed. Following the establishment of the response surface model, a study on the optimal polishing parameters was conducted to obtain the suitable parameters for maximum shear force and minimum surface roughness. The results show that the maximum shear force 6.11 N and minimum surface roughness Sa 88 nm can be attained, respectively, under the conditions of (1) polishing tool speed of 724.254 r·min-1, working gap of 0.5 mm, and abrasive particle size of 200 μm; and (2) polishing tool speed of 897.87 r·min-1, working gap of 0.52 mm, and abrasive particle size of 160 μm.

Characterization of road surface topography changes during polishing process with characteristic roughness parameter

In this paper, three-dimensional structure feature points of the asphalt mixture were obtained based on the industrial CT. The surface morphology of the asphalt mixture was then extracted through image morphology processing and evolutionary matching algorithms. A series of accelerated polishing tests were utilized to simulate the long-term polishing effect of the tire load on the asphalt pavement. Combining with digital image analysis, the full-life morphology evolution trend of the asphalt pavement was analyzed, and the full-life surface morphology datasets of the asphalt pavement were constructed. By comparing the power spectrum density of the asphalt pavement morphology at different wear stages, a segmented evaluation method based on the spectral fractal method was proposed. Combining the spectral fractal parameters and statistical geometric parameters, a multi-scale asphalt pavement surface morphology feature evaluation index was proposed. This provides a more intricate and detailed analysis of the surface structure of asphalt mixtures.

A novel atomic removal model for chemical mechanical polishing using developed mesoporous shell/core abrasives based on molecular dynamics.

To improve polishing performance and reduce the environmental pollution of chemical mechanical polishing (CMP) tests, mesoporous shell/core silica abrasives were prepared, and a novel green CMP slurry was developed, including sorbitol, hydrogen peroxide and sodium carbonate. Prior to CMP, fused silica was roughly polished with ceria slurry. Using developed mesoporous abrasives, surface roughness Sa is reduced from 0.347 to 0.253 nm for a scanning area of 200 × 200 μm2, and the material removal rate (MRR) is increased from 70 to 127 nm min-1, compared with traditional solid abrasives. Based on molecular dynamics (MD) simulations, a novel atomic removal model is proposed for mesoporous abrasives through the immediate elastic recovery of atoms. MD simulations suggest that the formation of convex peaks and pits was inhibited by the mesoporous structure, promoting uniform distribution of surface atoms and atomic removal. This is different from a conventional simple increase of polishing times. In addition, more bridge bonds of Si-O-Si and a lower average Si-O bond order are produced in fused silica samples due to their mesoporous structure, contributing to a higher MRR.

Preparation and Performance Testing of Green Non-toxic Polishing Solution for Medical Titanium Alloy

To obtain the lower toxic residue on the medical titanium alloy surface in chemical mechanical polishing process, a new green polishing solution was proposed and evaluated in this study. The humoral fluid was selected as the basic solution in which the silica abrasive particles were used for the grinding particles, and the H2O2 was added as the oxidant. A chemical mechanical polishing test was carried out for its performance investigation with titanium alloy material. Then the surface roughness and material remove ratio of test samples were analyzed and compared with that of existed polishing solution condition. At last, the toxic residue of the titanium alloy samples was obtained by scanning electron microscopy technology. The experimental results indicated that the better material removal rate and surface roughness of medical titanium alloy with humoral polishing solution are obtained comparing with existed polishing solution condition. More importantly, the content of toxic elements on the sample surface was significantly reduced due to the more aluminum and vanadium ions dissolved in polishing solution, which is more beneficial for its application in the medical prosthetics field. This study provides a new reference for the toxic residue reduction on the material surface of medical titanium alloy in chemical mechanical polishing process.

Skid-resistance durability and wear/polish-resistance behaviors of ultra-thin friction course designed based on the differential polishing of aggregates

To improve the skid-resistance durability of asphalt pavements in a cost-effective manner, this study introduced a differential-polishing principle based on blending various aggregates. SMA-5 ultra-thin friction courses (UTFC) were prepared using mineral aggregates consisting of 88# calcined bauxite and limestone blended in six proportions. Long-term simulated traffic polishing tests were performed on six types of UTFC surfaces in the laboratory. Direct skid-resistance indexes, BPN20 and μ80, were used to evaluate skid resistance at low and high velocities after different polishing cycles, respectively. Surface texture evolution during long-term polishing was analyzed using bearing area ratio, mean profile depth, and fractal dimension D. Additionally, an attenuation prediction model for skid resistance was developed. Aggregate mechanical properties affecting skid-resistance durability of UTFC were investigated through grey correlation analysis. The results show that a significant differential-polishing effect was generated during long-term polishing due to large differences in the two aggregates’ wear/polish resistance, which can effectively reduce the attenuation rate of skid resistance of UTFC and improve skid-resistance durability by decreasing wear loss of UTFC surface aggregate and forming texture structure difference between aggregates to maintain rough surface texture. The reasonable blending proportion of 88# calcined bauxite was determined to be 40%–60% of the mineral aggregate mass. It was also found that the developed predictive model can reflect the attenuation law of skid resistance, and PSV and LAA loss of aggregates are well correlated with the skid-resistance durability of UTFC.

Cetyltrimethylammonium bromide reformed ceria nanocomposites of chemical mechanical planarization for silica wafers

BackgroundChemical-mechanical planarization (CMP) is the most important process in the semiconductor industry, as it affects the product manufacturing yield. Of the several factors involved in planarization, the choice of abrasive slurries affects the extent to which impurities and roughness are removed. Cerium oxide (CeO2) is considered an outstanding polishing material because of its excellent hardness, well-controlled structure, and chemical force, and CMP requires well-dispersed slurry nanoparticles (NPs) with uniform structure, size, and shape. In this study, urea/alkaline-induced nanocubic MethodsCeO2 was synthesized in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB)-generated cubic CeO2 NPs, which were then used in a silica wafer polishing test. Dynamic laser scattering and transmission electron microscopy indicated that the cubic plate NP size distribution and zeta potential ranged from 18 to 30 nm when measured between –35 and –45 mV. Elemental composition via X-ray photoelectron spectroscopy was studied to demonstrate the mechanism of Ce3+/Ce4+ with crystal information, which matched the X-ray diffraction grain size calculation and finite element–scanning electron microscopy measurements. We also performed a simulation of cubic CeO2 NP formation and pillar CeO2 inhibition under an additional amount of structure-modifying agent (e.g., CTAB). Fourier transform infrared spectra indicated a successful CTAB reaction with CeO2. Small angle X-ray scattering spectra were used to obtain simulated NP shapes and parameters via the SasView model. A confocal laser scanning microscope was then used to measure the roughness and 2-D plane view of an 8-inch tetraethyl orthosilicate coated silica wafer. Significant findingsOur results showed that the bared silica wafer planarize with CTABx-CeO2 NPs reduced the ISO grade number from Level 9 to Level 7, which corresponds to a 70.7–74.5% roughness planarization of the raw material. This study presents a fast, uniform, low-roughness CMP slurry material synthesis and characterization method that can enhance the technique of slurry nanoparticle synthesis from stable materials.

Improving the Polishing Speed and Surface Quality of 4H-SiC Wafers with an MnO<sub>2</sub>- Based Slurry

We carried out chemical mechanical polishing (CMP) on commercially available 6 inch SiC wafers (epi-ready products) with slurries containing different abrasive types and evaluated the latent scratch density from the mapping measurement of the wafers using mirror projection electron microscope (MPJ). Comparing to the wafer before polishing, the latent scratch density decreased on the wafer polished with MnO2+KMnO4, while that increased by polishing with Al2O3+KMnO4. The two-step polishing using first Al2O3+KMnO4 and then SiO2+H2O2 can reduce the latent scratch density to the same level as that with MnO2+KMnO4, but long polishing time is required because of the low polishing rate in the process with SiO2+H2O2. We investigated the reason why MnO2 slurry can suppress the occurrence of latent scratches by a polishing test on a wafer with an SiO2 film on its (0001)Si surface. The results suggest the oxidation of the SiC surface is rate-determining step for polishing with MnO2+KMnO4. It was also found that wafers without an SiO2 film could not be polished with only MnO2 abrasives. Thus the mechanical contribution to polishing by MnO2 abrasives in KMnO4-based slurry is smaller than the chemical contribution, which can suppress the occurrence of latent scratches. KMnO4-based slurry containing MnO2 abrasives performs the CMP process with low latent scratch density in a time shorter than that containing Al2O3 or SiO2 abrasives.

Comparative Analysis of Finite Element Simulation and Experiment on the Polished Surface Quality of Hard Anodized Film of Aluminum Alloy

According to the abrasive morphology and distribution of sandpaper surface, the finite element model of hard anodic oxide film polishing was established by using ABAQUS finite element software, and the hard anodic oxide film and aluminum alloy matrix were defined respectively. The effects of hard anodic oxide film polishing process, polishing surface quality and polishing parameters on the polishing force were simulated. The polishing surface quality and polishing force simulated by finite element model were verified by experiments. The results show that in the polishing process, the residual stress of polishing surface is mainly distributed in the range of 0.0034mm, and the chips produced by polishing are mainly broken and long strips with microscopic morphology, and polishing mainly depends on the front part of abrasive particles in the feeding direction of sandpaper. Under the action of abrasive particles of sandpaper, the results of finite element simulation and test show that there are certain grooves on the surface of oxide film. The finite element simulation of the normal polishing force of hard anodic oxide film is consistent with the polishing test results. During the process of polishing hard anodic oxide film, the normal polishing force increases as the polishing speed increases; the normal polishing force increases as the polishing removal amount increases; the polishing removal amount parameter has a greater degree of influence on the polishing force.

Synthesis, Characterization, and Polishing Properties of a Lanthanum Cerium Fluoride Abrasive.

One kind of lanthanum cerium fluoride abrasive was prepared using the raw materials Ce2(CO3)3, La·Ce(CO3)3, and NH4F at temperatures of 400-1050 °C. The combined techniques of X-ray diffraction with Rietveld refinements, scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to characterize the products. It was found that the materials are all made up of agglomerated irregular block-shaped particles with particle sizes in micrometer ranges. Below 850 °C, the product is a mixture of cubic CeO2 and trigonal LaF3, while above 900 °C, it is a mixture of cubic CeO2 and tetragonal LaOF. A higher calcination temperature suppresses the formation of the LaF3 phase but enhances the LaOF phase. The Ce in the prepared material is present in mixed states of Ce3+ and Ce4+, and the Ce4+/Ce3+ ratio increases with increasing calcination temperature. When the material prepared at 900 °C was used in the polishing test on K9 glass, the obtained polishing surface is very clean and flat, and the thickness difference before and after grinding is moderate, indicating its potential as an abrasive for polishing the surface of optical glass.

Study of monolithically integrated 940 nm AlGaAs distributed Bragg reflectors on graded GaAsP/bulk Si substrates

We report the fabrication of monolithically integrated 940 nm AlGaAs distributed Bragg reflectors (DBRs) on graded GaAsP/Si substrates. Low-density surface bumps and cross-hatch patterns were observed on the DBR surfaces. Cross-sectional DBR layers are smooth and flat. The reflectance spectra of the GaAsP/Si DBRs have lower intensities than those of the GaAs DBRs and have double peaks. Transfer matrix method calculations, surface scratch and polishing tests were conducted, which suggest that the surface cross-hatch was the cause of the inferior DBR reflectance spectra.

Determining the Long-Term Skid Resistance of Steel Slag Asphalt Mixture Based on the Mineral Composition of Aggregates

This study intends to predict the long-term skid resistance of steel slag asphalt mixture (SSAM) from the mineral composition of the aggregates. The polished stone value (PSV) and mineral composition of the aggregates were assessed using the accelerated polishing test and X-ray diffraction, respectively. The hardness (H) and surface texture richness (STR) of the aggregates were calculated from the mineral composition of the aggregates, and then a multivariate linear model was established between PSV and H and STR. The British pendulum number (BPN) and three-dimensional morphology of the SSAM were then evaluated using a British pendulum and a pavement laser scanner, respectively. Finally, an exponential relationship was established between BPN, aggregate PSV, and various aggregate amounts of SSAM. The results show that steel slag with H, STR, and PSV was better than natural aggregates and can significantly improve the skid resistance of pavement, but the relationship between steel slag content and long-term skid resistance of SSAM was not linear, and SSAM with 50% steel slag content had the best skid resistance. The mathematical model developed can predict the long-term skid resistance of SSAM from the mineral composition of the aggregates. The model can be used by designers to predict the long-term skid resistance of steel slag asphalt pavements at the design stage and thus better determine the proportion of steel slag to other aggregates.

Post processing of additively manufactured 316L stainless steel by multi-jet polishing method

Post-process finishing of the additively manufactured (AMed) surfaces is still a critical issue, especially for the AMed surfaces with complex surface geometry, which largely limits the application of additive manufacturing. Hence, this paper presents a multi-jet polishing (MJP) method for post processing of AMed surfaces, utilizing a number of pressurized micro/nanometer abrasive water jets. A group of systematic polishing tests are conducted on 316L stainless steel (SS) prepared by powder bed fusion, to test the polishing performance, as well as the effect of key parameters. Moreover, surface integrity characterization and analysis are also carried out to make full evaluation of the MJP process on AMed 316L SS. The results indicate that MJP is effective for the post processing of AMed 316L SS, to obtain nanometric surface roughness on AMed surfaces, shedding the light on wide application of MJP for AMed complex surfaces.

Mitigation of Urban Heat Island Effects by Thermochromic Asphalt Pavement

Asphalt road pavements are usually dark and, consequently, have a low albedo. Therefore, they absorb energy as heat, increasing the Urban Heat Island (UHI) effect, which impacts the environment, energy consumption, and human health. Through the functionalization with thermochromic materials (TM), this work aims to develop a smart asphalt pavement able to change its surface color, increasing the reflectance, and thus mitigate this phenomenon. To achieve this goal, asphalt substrates were functionalized by a surface spray coating of a thermochromic solution (TS) containing aqueous solution of thermochromic microcapsules (thermocapsules), dye, and epoxy resin. To evaluate the functionalization features, Fourier Transform Infrared Spectroscopy (FTIR), and Thermal Differential test (TDT) with cyclic temperature variation were performed in the functionalized asphalt binder. Moreover, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectrometry (EDS), a Quick Ultraviolet Accelerated Weathering Test (QUV) with Colorimetry test, and an adaptation of the Accelerated Polishing Test (APT) were performed on the functionalized asphalt mixture. The results indicate that the functionalization of asphalt substrates with TS exhibits a reversible color-change ability, higher luminosity values when subjected to temperatures above 30 °C, and wear resistance.

Accelerated polishing test in road marking paint and its connection with water absorption

La durabilidad de los materiales de demarcación vial se evalúa con ensayos que van desde pruebas de campo a equipos de gran escala. Éstos requieren de un tiempo de ensayo considerable para obtener el resultado o de dispositivos costosos. Para evaluar la abrasión se utilizan métodos del ámbito de pinturas en general, que presentan una falencia en la evaluación en servicio relacionada con el comportamiento ante la presencia de agua. Este aspecto genera el interés de adaptar el ensayo de Pulimento Acelerado de Áridos con la finalidad de evaluar el desgaste mediante pérdida de peso de las pinturas. Al ser un equipo utilizado en el ámbito vial, facilita la generalización de su utilización en laboratorios viales de control de calidad. Los valores resultantes se contrastan con los obtenidos en el ensayo Taber Abraser y en una prueba en servicio realizada con este fin. Adicionalmente, se implementa la absorción en agua como parámetro adicional. Finalmente, se destaca que la adaptación del ensayo de Pulimento Acelerado permite tener una estimación del comportamiento en servicio, con la ventaja de poder ensayar varias muestras simultáneamente bajo las mismas condiciones, encontrando que la absorción de agua está relacionada con los resultados obtenidos.

A quantitative study of removal mechanism of copper polishing based on a single pad-asperity polishing test

Continuous requirement for the improvement of chip performance caused an increasing attention on the copper polishing precision. To predict the copper removal rate, it is critical to understand the copper removal mechanism and quantitatively decouple the chemical and mechanical interactions. In this paper, the copper removal mechanism was investigated by a single pad-asperity polishing test with an in situ measurement device, which minimized the effects of random pad-asperity contact states and slurry distribution differences encountered in conventional experiments. Several electrochemical methods were used to monitor the chemical reaction rate and passivation processes, including the chrono-current method, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The results reveal that mechanical action can hardly remove the unreacted copper. The complexing agent can only dissolve the mechanically removed passivation layer rather than dissolve the passivation layer directly. The copper is removed in an alternating process of generation and removal of passivation layers. A model is developed to predict the copper removal depth within 10% error. This research provides a quantitative analysis method for material removal rate of metal polishing. It can answer whether chemical reaction or mechanical action limits the improvement of removal rate or causes the change of removal rate.

The effects of surface finish on the fatigue performance of electron beam melted Ti–6Al–4V

Additive manufacturing (AM) is an advanced manufacturing technique whose uptake within the aerospace industry is being limited by the lack of understanding of the effects of surface finish on the fatigue properties of AM built components. It is known that the surface profile of as-built AM parts is significantly rougher than its traditionally manufactured equivalent, promoting stress raising features that have an adverse effect on fatigue life.This paper will focus on developing a deeper understanding of the fatigue properties of the widely-used alpha-beta titanium alloy, Ti–6Al–4V, as manufactured through electron beam melting (EBM) and the role that surface roughness plays. Results have been generated on as-built and machined & polished EBM test coupons, supported by microstructural and fractographic analysis, X-ray computed tomography (XCT), advanced surface profilometry and hardness testing.Results have shown that as-built EBM Ti–6Al–4V samples have a significantly inferior fatigue life than machined & polished samples, despite the material in each of the surface finish types being hot isostatically pressed (HIP). It has been revealed that while surface parameters, MR2 and Ra, provide no correlation to high cycle fatigue life, it is shown that as the Rp surface parameter decreases, the respective number of cycles to failure increases. It can be concluded that a samples’ surface roughness is a highly contributing factor in influencing fatigue performance, yet it should not be considered in isolation since other features, including porosity, also play an important role.

A robotic polishing parameter optimization method considering time-varying wear

In the automatic polishing process, the wear of polishing tools and the change of polishing parameters will affect the Preston coefficient, which makes it difficult to establish an accurate material removal model to achieve stable and excellent polishing quality. In this paper, a robotic polishing parameter optimization method considering time-varying wear is proposed to address these issues. First, combining the rich information in the theoretical modeling method with the data-driven regression method, a material removal regression model incorporating prior knowledge is proposed, which greatly reduces the large amount of experimental data required by the original regression model. The proposed model is able to track the wear variation of the sandpaper as well as the effect of polishing parameters. Then, based on the proposed prediction model, the genetic algorithm is used to optimize the polishing parameters in order to achieve better machining quality and less energy consumption. Finally, the experimental verification is carried out on the hybrid robot polishing test bench. The results show that the proposed material removal regression model incorporating prior knowledge has higher prediction accuracy and less required experimental data than existing models. The proposed robot polishing parameter optimization method can effectively compensate for tool wear and ensure the consistency of material removal during polishing while reducing energy consumption.