Concentration Of Abrasive Particles Research Articles

Predicting the Material Removal in Polishing: The Applicability of Two Types of Statistical Models

This article develops two statistical rough surface models to investigate the material removal rate in surface polishing. Model I implies that the contact between two surfaces is equivalent to that between a composite surface and a plane; but Model II is without the equivalent surface concept. The prediction differences of the two models were first investigated with the aid of contact mechanics. The analysis shows that the relative error of the predictions by the two models could be minimized by considering the interactions between asperities, and that this error increases with the separation of the mean planes, but decreases with the asperity density, asperity radius and standard deviation of the asperity height. By extending the models to study the material removal rate in polishing, it was found that asperity interaction is an important factor in a statistical modelling of polishing, and that with a given separation of the reference planes of the pad and workpiece surfaces, the material removal rate increases with the volume concentration of abrasive particles and varies with the pad roughness. The study also showed that the microstructure of a polishing pad has a significant effect on the material removal rate of a polishing.

Experimental and Morphological Investigations Into Electrical Discharge Surface Grinding (EDSG) of 6061Al/Al2O3p 10% Composite by Composite Tool Electrode

In this study, a special experimental setup of EDSG using EDM and surface grinding machine has been developed in the laboratory to investigate the effect of seven input parameters namely tool polarity, peak current, pulse on-time, pulse off-time, rotational speed, abrasive particle size, and abrasive particle concentration on material removal rate (MRR) as performance measure of the process. The novelty of the present research work is that successful efforts have been made to machine the 6061Al/Al2O3p 10% metal matrix composites (MMC) by composite tool itself. The copper-based composite tool electrodes were fabricated by powder metallurgy route with different sizes of abrasives of silicon carbide, while 6061Al/Al2O3p 10% MMC were fabricated through stir-casting process. The research outcome will identify the important parameters and their effect on MRR of 6061Al/Al2O3p 10% composite in EDSG. The experimental results reveal that tool polarity, peak current, and rotational speed are the most influential parameters that affect MRR in EDSG process. The micro-structural and morphological analysis of machined surfaces has also been carried out to analyze the surface topography. It has been concluded that the abrasive particles substantially improves the MRR after removing the resolidified layer from the machined surface.

Effect of Polishing Parameters on Chemical Mechanical Planarization of C-Plane (0001) Gallium Nitride Surface Using SiO2 and Al2O3 Abrasives

In this study, Chemical Mechanical Planarization (CMP) of (0001) GaN surface, using two different slurries containing colloidal silica and alumina as abrasive nanoparticles, has been reported. Effect of processing parameters, such as concentration of the oxidizer, downward pressure, head rpm, base rpm, pH of the slurries, and type and concentration of abrasive particles, on the material removal rate (MRR) and surface quality (roughness) have been studied in details. The maximum MRR has been found to be ∼39 nm/hr and ∼85 nm/hr for slurries containing SiO2 and Al2O3 abrasives, respectively, under 38 kPa pressure, 90 rpm base speed (100 rpm for Al2O3 containing slurry), 30 rpm carrier speed, slurry pH 1 (2 for Al2O3 containing slurry), 0.3 M Oxidizer concentration, and 3.75 wt% abrasive particle concentration. RMS surface roughness of 1.3 Å and 0.7 Å, over scanning area of 10 μm × 10 μm and 5 μm × 5 μm, respectively, has been achieved on polished Ga-faced GaN surface for SiO2 containing slurry using optimized slurry chemistry and processing parameters.

Machining Performance and Surface Integrity of AISI D2 Die Steel Machined Using Electrical Discharge Surface Grinding Process

The aim of this study is to establish optimum machining conditions for EDSG of AISI D2 die steel through an experimental investigation using Taguchi Methodology. To achieve combined grinding and electrical discharge machining, metal matrix composite electrodes (Cu-SiCp) were processed through powder metallurgy route. A rotary spindle attachment was developed to perform the EDSG experimental runs on EDM machine. Relationships were developed between various input parameters such as peak current, speed, pulse-on time, pulse-off time, abrasive particle size, and abrasive particle concentration, and output characteristics such as material removal rate and surface roughness. The optimized parameters were further validated by conducting confirmation experiments.

Elastohydrodynamic Lubrication Modeling of Hydrodynamic Nanopolishing Process

Nanopolishing processes are used in medical, industrial, telecommunication, optics, and military fields. Hydrodynamic polishing (HDP) is one of the prominent nanopolishing methods in creating nanopolished surfaces on hard and profiled surfaces, where rigid tool-based methods like diamond turning, grinding, and honing have many limitations. This work is focused on modeling of hydrodynamic polishing method. In this method, a film of abrasive suspension is formed between the work-piece surface and a rotating soft tool, which helps in nanopolishing. The past experimental research gives an insight into the process but the process has not been explicitly modeled. Consequently, besides experimental characterization, a numerical/mathematical model of hydrodynamic polishing process is important. This paper presents a model of the HDP process which takes into account the polishing process variables, such as, contact load, spindle speed, tool and work-piece material properties/geometry, and abrasive suspension properties. The response of the model is the pressure distribution and the abrasive film thickness in the polishing zone. To model the elastohydrodynamic process encountered in HDP, the pressure and the film thickness profiles of lubricated isothermal point contacts have been evaluated using the multilevel multi-integration (MLMI) scheme coded in C programming language. Finally, load, tool stiffness, speed, and particle concentration in the suspension have been implicitly correlated to the surface roughness (SR) to evolve a semi-empirical model for surface roughness as a function of mean film thickness and mean pressure. Empirical models for mean film thickness and mean pressure have also been developed as a function of process variables. These models have been developed from a Taguchi L27 orthogonal array wherein the mean pressure/film thickness values have been determined from the model and the average surface roughness values have been measured experimentally. It has been observed that the load does not affect the surface roughness significantly and mean pressure does not change with the change in abrasive size and spindle speed. Abrasive particle concentration has been found to be the most important parameter and it affects the surface roughness significantly.

Experimental investigations into surface roughness and yield stress in magnetorheological fluid based nano-finishing process

Magnetorheological fluid based finishing process is particularly useful for finishing of optical materials. Magnetorheological (MR) fluid consists of magnetic particles, abrasive particles, carrier fluid such as water or oil, and additive. Under the influence of magnetic field, magnetic particles form chain like structure and they support abrasive particles to perform finishing. Stiffness and abrasive holding power of MR fluid significantly depend on the size of magnetic particles while concentration and type of abrasive particles are also important parameters which affect the quality of finished surface. An experimental investigation is carried out to study the effect of size, concentration and type of abrasive particles as well as the size of magnetic particles on material removal rate and % change in surface roughness (Ra) of final finished surface of single crystal silicon workpiece. A rheological study in terms of yield stress is also carried out to analyze MR fluid behavior under magnetic field.

Nano–level finishing of single crystal silicon blank using magnetorheological finishing process

Magnetorheological finishing (MRF) utilizes magnetorheological (MR) fluid, which consists of magnetic particles, nonmagnetic abrasives, and some additives in water or other carrier to polish the materials. An experimental study is conducted to predict the effect of process parameters (concentration of magnetic particles and abrasive particles, carrier wheel speed, and initial surface roughness) on surface finish and material removal rate in MRF of single crystal silicon blank. The final surface roughness value in terms of arithmetical mean roughness (Ra) obtained is as low as 8nm from the initial value of 1300nm. An optimization study is also carried out to find optimum values of process parameters from the selected range.

Parameter Optimization of Ultrasonic Machining Process Using Nontraditional Optimization Algorithms

The optimum selection of process parameters is essential for advanced machining processes, as these processes incur high initial investment, tooling cost, and operating and maintenance costs. This article presents optimization aspects of an important advanced machining process known as ultrasonic machining (USM). The objective considered is maximization of material removal rate (MRR) subjected to the constraint of surface roughness. The process variables considered for optimization are amplitude of ultrasonic vibration, frequency of ultrasonic vibration, mean diameter of abrasive particles, volumetric concentration of abrasive particles, and static feed force. The optimization is carried out using three nontraditional optimization algorithms, namely, artificial bee colony (ABC), harmony search (HS), and particle swarm optimization (PSO). An application example is presented and solved to illustrate the effectiveness of the presented algorithms. The results of the presented algorithms are compared with the previously published results obtained by using genetic algorithm (GA).

ILD CMP with Silica Abrasive Particles: Interfacial Removal Kinetics and Effect of Pad Surface Textures

The removal mechanism for interlevel dielectric (ILD) chemical mechanical polishing (CMP) with fumed silica abrasive slurry was studied by measuring silicon dioxide wafer removal rates as a function of abrasive concentration and pH and also by examining the surface charges of the abrasive particles at different pH’s. The interfacial removal kinetics indicates that the wafer removal rate is consistent with a first-order reaction and is proportional to the concentration of surface silanolates on the abrasive particles. The actual removal is proposed to be achieved by a direct nucleophillic attack of the silica particle silanolates on the wafer Si–O bond. Pad surface texture provides the means to transport the slurry to the contact zone and the effective concentration of abrasive particles doing actual removal is greatly influenced by the pad surface macrotexture by grooving design and the microtexture by conditioning. The observed correlation between the pad surface parameters that are used to characterize the pad microtexture and the removal rate highlights the importance of the pad surface texture to ILD CMP.

Modeling effects of abrasive particle size and concentration on material removal at molecular scale in chemical mechanical polishing

A novel material removal model as a function of abrasive particle size and concentration was established in chemical mechanical polishing (CMP) based on molecular scale mechanism, micro-contact mechanics and probability statistics. A close-form equation was firstly developed to calculate the number of effective particles. It found nonlinear dependences of removal rate on the particle size and concentration, being qualitatively agreement with the published experimental data. The nonlinear relation results from the couple relationship among abrasive number, slurry concentration and surface atoms’ binding energy with the particle size. Finally, the system parameters such as the operational conditions and materials properties were incorporated into the model as well.

Influence of quartz particles on wear in vertical roller mills. Part I: Quartz concentration

The standard closed circuit comminution process commonly employed in industrial vertical roller mills has been analyzed to determine the influence of typical abrasive minerals on wear rates. With the main focus on raw mixes used in cement plants, synthetic mixtures imitating were prepared. Using statistical planning, a total of 10 tests were carried out with two different limestones and one type of quartz sand. The size distributions were kept constant and only the mixing ratios were varied. It appears from the investigation that mixtures consisting of minerals with different grindabilities result in an increased concentration of abrasive particles in the grinding bed (R2>0.99). The present study shows that the quartz concentration in the grinding bed is determining the wear rate.

Effect of abrasive particle concentration on preliminary chemical mechanical polishing of glass substrate

Effect of abrasive particle concentration on material removal rate (MRR), MRR per particle and the surface quality in the preliminary chemical mechanical polishing (CMP) of rough glass substrate was investigated. Experimental results showed that the MRR increases linearly with the increase of abrasive concentration and reaches to the maximum when the abrasive concentration is 20 wt.%, and then tends to be stable. When the abrasive concentration increases from 2 to 5 wt.%, the MRR per particle increases greatly and reaches a peak. Then the MRR per particle decreases almost linearly with the increase of the abrasive concentration. The root mean squares (RMS) roughness almost decreases with increasing particle concentration. In addition, in situ coefficient of friction (COF) was also conducted during the polishing process and the zeta potentials of abrasive particles in slurry with different solid concentration were also characterized. Results show that COF value is not related to zeta potential but be sensitive to glass surface conditions in terms of rough peaks in preliminary polishing of glass substrate.

Study on the Surface Integrity of Micro-Ultrasonic Machined Glass-Ceramic Material

Ultrasonic machining (USM) technique has long been used for fabricating various patterns and drilling holes on brittle materials. However, the surfaces generated by USM are normally rather rough and covered by deep penetrated cracks. This has greatly limited USM being used in micro-machining and fine machining. This research aimed to study the surface integrity of the USMed surface and develop a feasible way to minimize the scattered cracks so that good surface finish could be achieved. Machining parameters such as type and concentration of abrasive particles, grit size, and feed rate were systematically investigated to check their influences on the surface obtained. A ‘multi-stage’ micro-USM process was developed in this study and surface with Ra value better than 0.2m was achieved using the proposed process.

CMP Friction as a Function of Slurry Silica Nanoparticle Concentration and Diameter

Chemical mechanical polishing (CMP) is vital in the manufacturing of integrated circuits (IC). CMP removes unwanted material from an IC surface by rubbing it with numerous nanoscale abrasives that are brought into contact by polishing pad asperities. Friction is a consequence of this rubbing, and this friction may damage the next generation of porous IC dielectric materials with lower dielectric constants (low k). Fundamental experiments were done to understand the source of the friction to enable less damaging CMP. The coefficient of friction of an SiO 2 substrate on a polyurethane CMP pad was measured as a function of the slurry's SiO 2 abrasive particle concentration and size with a commercial pin on disk tribometer. Very low speeds (∼10− 3 m/s) were used to remove confounding hydrodynamic effects. The coefficient of friction increased by 10% with higher weight percentages of SiO 2 particles in the slurry, suggesting that a constant real area of contact is distributed between bare pad asperity contacts and higher friction SiO 2 particle contacts. The coefficient of friction also increased for the smallest slurry SiO 2 particle size. These results suggested possible routes for controlling CMP friction by controlling slurry particle size and concentration as well as the pad material.

Study on the Surface Integrity of Micro-Ultrasonic Machined Glass-Ceramic Material

Ultrasonic machining (USM) technique has long been used for fabricating various patterns and drilling holes on brittle materials. However, the surfaces generated by USM are normally rather rough and covered by deep penetrated cracks. This has greatly limited USM being used in micro-machining and fine machining. This research aimed to study the surface integrity of the USMed surface and develop a feasible way to minimize the scattered cracks so that good surface finish could be achieved. Machining parameters such as type and concentration of abrasive particles, grit size, and feed rate were systematically investigated to check their influences on the surface obtained. A ‘multi-stage’ micro-USM process was developed in this study and surface with Ra value better than 0.2m was achieved using the proposed process.

Effect of SiC powder-suspended dielectric fluid on the surface finish of 6061Al/Al<SUB align=right>2O<SUB align=right>3P/20p composites during electric discharge machining

Electrical Discharge Machining (EDM), one of the most widely used unconventional machining processes particularly for producing complex shapes on hard materials with high geometrical and dimensional accuracy. The work material surface obtained after EDM is characterised by a series of randomly laid out tiny craters produced by the high energy spark discharges and recast (white) layer formed due to resolidification and deposition of materials ejected from the craters. This requires some form of supplementary finishing operations. This paper presents the results obtained from a comparative machinability study carried out on stir-casted 6061Al/Al2O3P/20p work specimens with copper electrode tools by using plain dielectric fluid and Silicon Carbide (SiC) abrasive powder-suspended dielectric fluid and evaluating the machinability in terms of Surface Roughness (SR). The results of both the processes have been analysed using Lenth's method to find the significant parameters and obtaining optimum machining parameter settings. It was found experimentally that Abrasive Particle Size (APS); Abrasive Particle Concentration (APC) and pulse current are the most significant parameters that affect the surface characteristics.

Finishing effect of abrasive flow machining on micro slit fabricated by wire-EDM

This experimental research use the method of abrasive flow machining (AFM) to evaluate the characteristics of various levels of roughness and finishing of the complex shaped micro slits fabricated by wire electrical discharge machining (Wire-EDM). An investigative methodology based on the Taguchi experimental method for the micro slits of biomedicine was developed to determine the parameters of AFM, including abrasive particle size, concentration, extrusion pressure and machining time. The parameters that influenced the machining quality of the micro slits were also analyzed. Furthermore, in the shape precision of the micro slit fabricated by wire-EDM and subsequently fine-finished by AFM was also elucidated using a scanning electron microscope (SEM). The significant machining parameters and the optimal combinations of the machining parameters were identified by ANOVA (analysis of variation) and the S/N (-to-noise) ratio response graph. ANOVA was proposed to obtain the surface finishing and the shape precision in this study.

Some views on the erosion–corrosion response of bulk chromium carbide based cermets

Chromium carbide/nickel based composites are applicable in many environments involving tribo-corrosion due to their combined ability to resist wear and corrosion. Hence, they are candidate materials for use either in bulk as surface coatings in crude oil (offshore) or in power and marine industries. The aim of this work was to study the effect of material parameters such as composition and surface roughness, together with test conditions such as abrasive particle concentration, applied potential, temperature and time of experiment on the performance of chromium carbide based cermets. Potentiodynamic and potentiostatic tests were carried out as part of this work. SEM studies were also conducted to establish the mechanisms of the material degradation processes. Finally, erosion–corrosion maps were constructed based on the results. Material wastage, synergy and regime maps were developed for these materials and demonstrated that the performance of the cermet depends on the interplay of material and process variables.

Dependence of Non-Prestonian Behavior of Ceria Slurry with Anionic Surfactant on Abrasive Concentration and Size in Shallow Trench Isolation Chemical Mechanical Polishing

The dependencies of the non-Prestonian behavior of ceria slurry with anionic surfactant on the size and concentration of abrasive particles were investigated by performing chemical mechanical polishing (CMP) experiments using blanket wafers. We found that not only the abrasive size but also the abrasive concentration with surfactant addition influences the non-Prestonian behavior. Such behavior is clearly exhibited with small abrasive sizes and a higher concentrations of abrasives with surfactant addition, because the abrasive particles can locally contact the film surface more effectively with applied pressure. We introduce a factor to quantify these relations with the non-Prestonian behavior of a slurry. For ceria slurry, this non-Prestonian factor, βNP, was determined to be almost independent of the abrasive concentration for a larger size and a smaller weight conentration of abrasive particles, but it increased with the surfactant concentration for a smaller size and a higher concentration of abrasives with surfactant addition.

Self-modulating abrasive medium and its application to abrasive flow machining for finishing micro channel surfaces

This study developed a self-modulating abrasive medium whose viscosity and fluidity can be adjusted during the processing period. The complex micro channel was fabricated on the stainless steel (SUS304) by using wire electrical discharge machining (wire-EDM). An experiment of employing abrasive flow machining (AFM) was conducted to evaluate the characteristics of various levels of roughness and finishing of the micro channel surface. In the experiment, the parameters of affecting AFM machining including abrasive particle size, concentration, extrusion pressure and machining time were selected to verify the machining quality of the micro channel.