In this study, two morphologies of cerium oxide (CeO2) abrasive particles, octahedral and spheroidal, are synthesized by solvothermal method using cerium nitrate hexahydrate (Ce(NO3)3‐6H2O) as raw ...material. Fourier infrared spectroscopy, X‐ray diffractometer (XRD) and scanning electron microscopy (SEM) are used to characterize the composition and morphology of CeO2 abrasive particles. The synthesized CeO2 is used for chemical mechanical polishing (CMP) of the Si surface of 6H‐SiC wafers, and the surface morphology of the polished wafers are observed using atomic force microscopy (AFM). After polishing with octahedral and spheroidal abrasive particles, the surface roughness of the wafers are 0.327 and 0.287 nm, and the material removal rates (MRR) are 870 and 742 nm h−1, respectively. Calculations comparing the ultraviolet absorption spectra and bandgap energies of the two types of abrasive particles as well as molecular dynamics (MD) simulations reveal that the synthesized octahedral CeO2 particles possessed stronger surface chemical activity and material removal performance.
Two morphologies of cerium oxide (CeO2) abrasive particles, octahedral, and spheroidal, are synthesized by solvothermal method using cerium nitrate hexahydrate (Ce(NO3)3‐6H2O) as raw material. Comparing the bandgap energies and the polishing performance of the two types of abrasive particles as well as molecular dynamics simulations reveal that the synthesized octahedral CeO2 particles possesses higher surface chemical activity and mechanical destructive effect.
In this research, a one-way abrasive flow machining (AFM) was sketched and built, and the impact of temperature on surface roughness (Ra) values and material removal rate (MRR) before and after each ...test have been investigated considering the SiC. Al2O3, and B2O3 particles as abrasive particles. The abrasive particles were dispersed at 35 wt.% in the prepared media. The findings revealed that the media containing Al2O3 abrasive particles had higher surface roughness compared to the SiC and B2O3 particles. The maximum variation of surface roughness for SiC, Al2O3, and B2O3 particles was observed at −196 °C, which was 2.991, 2.588, and 1.684, respectively. In addition, the material removal rate values decreased for all the prepared samples as the temperature was reduced. At lower temperatures, lower material removal rate values were recorded since the viscosity of the abrasive paste increased.
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•Temperature efficacy on surface roughness and material removal rate were analyzed.•Comparison between SiC, Al2O3, and B2O3 particles as abrasive particle was investigated.•The SEM morphologies of the worn surfaces represented that abrasive particles caused finer surfaces.•Media containing Al2O3 abrasive particles had higher surface roughness.•Material removal rates decreased with the temperature decrement.
•The expansion characteristics of PASJ were explored.•The movement behavior of abrasive particles in PASJ was analyzed.•The flow characteristics of the shear layer in PASJ were investigated.•The ...periodic characteristics of PASJ were demonstrated.
Supercritical carbon dioxide (SC-CO2) jet has a wide range of applications for rock-breaking and fracturing in oil-gas exploration and development due to its special physical properties. Pulsed abrasive SC-CO2 jet (PASJ) created by self-excited oscillation has excellent rock-breaking performance, but its flow characteristics are still unidentified. Hence, the expansion characteristics of the jet, the motion behavior of the abrasive particles, the flow characteristics of the shear layer vortex ring, and the periodic characteristics of the jet were experimentally investigated by high-speed photography in this study. The results show that both the fluid expansion angle θf and abrasive particles expansion angle θp are affected by the nozzle structure and working parameters, while the latter is irrelevant to the length of the nozzle cavity. The tangent of fluid expansion angle θf at supercritical and subcritical environments are in the range of 0.24–0.34 and 0.15–0.27, respectively, while the tangent of abrasive particles expansion angle θp is between 0.22 and 0.3. Furthermore, the process of vortex ring extension, stretching, flipping, folding back, and collapse can be observed at the fluid boundary of the jet. Besides, at the supercritical ambient pressure, the position of the abrasive particles in the jet affects the line grayness variation, while in the subcritical ambient pressure, the line grayness variation is mainly influenced by the phase change of CO2 and the shear layer vortex ring evolution. The clarification of the flow characteristics of PASJ in this study can help promote its rock breaking performance for underground energy exploration.
•Established a micro dynamic model of magnetorheological polishing fluid.•Simulated the formation of magnetic chains and the precipitation of abrasive particles under a magnetic field.•Building a ...test bench to verify the precipitation pattern of abrasive particles.
This study aims to address the issue of poor workpiece surface machining quality due to inadequate abrasive particle precipitation during the processing of magnetorheological polishing fluid. The paper employs magnetic dipole theory and molecular dynamics theory to establish a microdynamics model for magnetorheological polishing fluid and conducts kinematic and dynamic analyses of magnetic and abrasive particles. The chaining process of magnetic particles in magnetorheological polishing fluid was simulated under an external magnetic field, and the precipitation process of abrasive particles under the action of magnetic particles was simulated and analyzed. Furthermore, we established a microscopic observation experimental platform for magnetorheological polishing fluid and verified the precipitation law of abrasive particles under the action of dynamic magnetic field. The study findings indicate that the magnetic particles will form a chain structure, when the rotating magnetic field has an effect on the magnetorheological polishing fluid, and the abrasive particles will precipitate from the magnetorheological polishing fluid and adhere to the upper end of the magnetic chain. Moreover, the precipitation rate of abrasive particles is also affected by the magnetic field strength, the volume fraction of magnetic particles, and the rotating magnetic field speed, with the abrasive particles’ precipitation rate specifically increasing with higher magnetic field strength. At a magnetic field strength of 100 kA/m, the abrasive precipitation rate reaches 80 % in approximately 90 s, which increases to 80 % in only 60 s at a magnetic field strength of 200 kA/m. Additionally, with the increase of magnetic particle volume fraction, the precipitation rate of abrasive particles decreases. Within the first 40 s of the test, the magnetic particle volume fraction increases from 10 % to 30 %, and the precipitation rate of abrasive particles decreases by about 11 %. Similarly, the abrasive precipitation rate is affected differently by the rotating magnetic field speed. As the rotating magnetic field speed increases, the abrasive precipitation rate shows a trend of first increasing and then decreasing. When the rotating magnetic field speed increases from 20 r/min to 40 r/min, the abrasive precipitation rate of the first 40 s increases by about 25 %. When the speed continues to increase to 60 r/min, the precipitation rate of abrasive particles gradually decreases.
This paper uses the weight function to modify the particle volume fraction algorithm. The VOF model is modified by adding the particle phase volume fraction and momentum source to the control ...equation, the semi-resolved VOF-DEM model is established, and PTV experiment is used to verify the model. Based on this model, the flow and distribution characteristics of the abrasive are obtained: 1) The water-abrasive flow near the outlet of the convergent section of the nozzle has a significantly dense two-phase flow characteristic, and the collision between particles dominates particle flow. 2) The particles at the nozzle outlet are distributed in the radial direction of “n”, and with the increase of the stand-off distance of the jet, the particle phase volume transitions from “n” to “m” distribution. The research on the flow characteristics of particles can provide a basis for the nozzle design of pre-mixed abrasive water jets.
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•A two-way coupled CFD-DEM model of an abrasive water jet was proposed and validated.•The semi-resolved VOF-DEM model reduces the dependence of calculation on grids.•Acceleration and distribution of abrasive are obtained based on the modified model.•Collision between particles dominates particle flow at the convergent section exit.
Despite many studies on the subject, brake squeal remains a major concern for the automotive industry. Much progress was made toward understanding and preventing this issue, focusing on the dynamic ...behavior of the brake. However, the problem is far from fully understood. Among many friction material ingredients, abrasives are extensively used to regulate friction and wear and are recognized as the main contributors to brake noise. This work investigates the correlation between characteristics of abrasives and squeal noise occurrence determined through the SAE J2521 dynamometer test procedure, FESEM, EDS, nanoindentation, and roughness profiling analyses. The particle size, hardness, Young's modulus, and resistance to elastic deformation of 13 different grades of abrasives were measured. The correlation between these characteristics and squeal noise occurrence was determined through statistical analysis. Spearman's rank correlation coefficient (ρ) showed that squeal noise strongly correlated with hardness and resistance to elastic deformation (ρ = 0.61 and ρ = 0.56, respectively) of abrasive materials and exhibited a poor correlation with their particle size (ρ = −0.099). However, considering groups of samples of the abrasive type, particle size is a characteristic that should be regarded in analyzing squeal noise propensity. In the case of SiC, coarser particles (D90 = 196.70 μm) showed a significant reduction in squeal noise compared to finer particles (D90 = 6.30 μm). On the other hand, coarse particles markedly increased the mass loss of the brake pad and brake disk.
•Dynamometer was used to evaluate the squeal noise response of thirteen abrasives.•Abrasives hardness affects squeal noise occurrence, friction, and disk wear.•Squeal noise correlates with elastic deformation parameters of abrasive particles.•Squeal noise and wear of friction materials are influenced by tribofilm nature.
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•A molecular dynamics (MD) model for vibration-assisted grinding (VAG) with various vibration directions polycrystalline iron is established.•The MD model considers randomly ...distributed abrasive particles and initial rough surface.•VAG reduces average grinding force but increases instantaneous grinding force.•Lattice rotation and dislocation mediation are the mechanisms of plastic deformation of polycrystalline iron under VAG.•Radial vibration mainly improves surface microstructure, and axial vibration contributes to reducing surface roughness.
Ultrasonic vibration-assisted grinding (UVAG) has attracted plenty of attention to significantly improve surface integrity. However, existing research has not systematically investigated the effect of vibration directions during UVAG at atomic and nanoscales, limiting our understanding of the plastic deformation mechanisms and microstructural evolution of ultra-precision machining. To address this issue, we proposed an MD model for multi-abrasive UVAG of polycrystalline iron considering various vibration directions. We comprehensively analyzed atomic flow fields, surface atom distributions, temperature fields, grinding forces, stress distributions, crystal orientations, and dislocation distributions. The simulation results demonstrate that UVAG effectively reduces grinding force and results in instantaneous grinding forces greater than conventional grinding (CG), and the instantaneous load impact phenomenon of radial vibration is more obvious. In surface morphology, axial vibration contributes to reducing surface roughness, while radial vibration is detrimental to surface smoothness. Microstructural evolution is mainly induced by stress. The primary plastic deformation mechanisms in UVAG of polycrystalline iron involve lattice rotation and dislocation mediation. Compared to axial vibration-assisted grinding (AVAG), radial vibration-assisted grinding (RVAG) and elliptical vibration-assisted grinding (EVAG) exhibit finer grain refinement, with RVAG leading to the highest dislocation density.
This research investigates abrasive particles agglomeration via interaction between O2 bubbles and slurry abrasives during the tungsten chemical mechanical polishing (W CMP) process. The abrasive ...particles in slurry were highly agglomerated due to higher volumes of O2 bubbles produced in the reaction between the catalyst Fe(NO3)3 and the oxidizer H2O2. Results obtained from a gas pressure sensor confirmed the generation of higher O2 volume via the decomposition of H2O2 at a high catalyst concentration and an increase in reaction temperature. The decomposed O2 volume rate at 80 °C was reported at the maximum value of 2.0 × 10−2 L/s at 120 ppm as compared to the moderate and minimum rates of 3.5 × 10−3 and 3.2 × 10−4 L/s for catalyst concentrations of 60 and 30 ppm, respectively. Images of O2 bubbles, captured using a high-speed camera, exhibited subsequent enhancement in average O2 bubble diameters of 91, 427, and 503 μm at 25, 60, and 80 °C, respectively. Analysis of surface scans confirmed large abrasive particles contamination on the TEOS wafer with an increase in the O2 bubble flow rate and bubbling time. Also, large abrasive particles agglomeration was observed in the presence of O2 bubbles as compared to no bubbles, as measured by dynamic light scattering DLS. It is believed that higher hydrophilicity of abrasive particles with O2 bubbles increased the adhesive force between the abrasive particles and the in-situ generated O2 bubbles. The high drag force generated during the collapse of O2 bubbles is essentially attributed a strong attractive force between the abrasive particles and the TEOS wafer which strongly binds with the abrasive particles and intensifies the defect level as particle agglomeration.
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•Effect of O2 bubbles on abrasive particles agglomeration during tungsten CMP•High O2 bubbles resulted via decomposition of H2O2 in presence of catalyst Fe(NO3)3 at 80 °C•Increase in catalyst Fe(NO3)3 concentration increased the formation of O2 bubbles•Large abrasive particles contaminates with increase in the O2 bubble flow rate and bubbling time
