Effect Of Mechanical Polishing Research Articles

INFLUENCE OF MECHANICAL POLISHING ON THE PHYSICAL-MECHANICAL PROPERTIES OF MONOCRYSTALLINE p-SiGe SUBSTRATES

The effect of mechanical polishing on the structural-sensitive physical properties of the monocrystalline p-SiGe substrates has been investigated. Non-monotonic changes in the electrical characteristics, optical absorption spectra of infrared radiation, internal friction and shear modulus values on the (111) surfaces of SiGe substrates treated with a polishing compound containing different dispersions diamond particles have been shown. Defects formed in the polishing process interact with boron and technological origin oxygen and carbon atoms. Defects of deformation origin are formed in the mechanical processing at room temperature. In the absorption spectra of infrared irradiation a decrease of the concentration of carbon and oxygen atoms and Ci-Cs, Ci-Oi, V-O defects have been revealed. It is supposed that the non-monotonic changes in the electrophysical and physical-mechanical properties on the (111) surfaces of SiGe substrates are caused by changes in the electrical activity of defects and mechanisms of the dislocation-defect associations interaction, formed in the polishing processes.

Effect of mechanical polishing of aluminum alloy surfaces on wetting and droplet evaporation at constant and cyclically varying pressure in the chamber

Effect of mechanical polishing of aluminum alloy surfaces on wetting and droplet evaporation at constant and cyclically varying pressure in the chamber

Mechanism study of the residual stress evaluation of low-carbon steels using the eddy current magnetic signature method

The eddy current magnetic signature (EC-MS) method is a relatively new method used to evaluate the residual stresses of ferromagnetic steels with higher sensitivity than other magnetic techniques. In this study, the effects of mechanical polishing and the ferrite–pearlite structure on the shape of the EC-MS signal were investigated in two experiments to clarify the effect of compressive residual stress on the EC-MS signal shape. In the first experiment, the work-hardened layers of the specimens were removed by electrolytic polishing and the EC-MS signals of the specimens were investigated. The second experiment involved the EC-MS measurements of materials with different pearlite contents, i.e., low-carbon steel with 0.17% and 0.27% carbon and pure iron. Specimens with different residual strains were prepared using a tensile test apparatus and their EC-MS signals were compared. In both experiments, the residual stresses acting on the specimens were measured adopting X-ray diffraction. The results reveal that the non-anisotropic compressive residual stress acting on the specimen surface changed the EC-MS signal in an anti-clockwise manner while the unidirectional compressive residual stress inside the specimen changed the EC-MS signal in a clockwise manner.

The influence of substrate electropolishing on anodization behavior, corrosion resistance, cytocompatibility and antibacterial ability of NiTi alloy

Ni-Ti-O nanotubes (NTs) anodically grown on nearly equiatomic NiTi alloy are promising in biomedical field, but mechanical polishing pretreatment of the substrate usually results in severe pitting. The present work proposes to use electropolishing (EP) as pretreatment of anodization of the NiTi alloy to eliminate the side effect of mechanical polishing. Scanning electron microscopy was used to observe the morphology of the samples. Potentiodynamic polarization test was carried out to evaluate the corrosion behavior. Biological experiments were performed to assay their cytocomaptibility and antibacterial ability. Our results show pitting can be completely avoided after substrate EP pretreatment, yielding a macro smooth surface, while micro ordered nanotubular structure is well preserved. EP pretreatment enhances the corrosion resistance and antibacterial ability of the NiTi alloy when compared with that of mechanically polished sample, and all the samples show no appreciable cytotoxicity, clearly indicating EP is a promising pretreatment for fabricating Ni-Ti-O NTs on the NiTi alloy for biomedical applications.

The influence of polishing techniques on pre-polymerized CAD\CAM acrylic resin denture bases.

BackgroundLately, computer-aided design and computer-aided manufacturing (CAD/CAM) has broadly been successfully employed in dentistry. The CAD/CAM systems have recently become commercially available for fabrication of complete dentures, and are considered as an alternative technique to conventionally processed acrylic resin bases. However, they have not yet been fully investigated.ObjectiveThe purpose of this study was to inspect the effects of mechanical polishing and chemical polishing on the surface roughness (Ra) and contact angle (wettability) of heat-cured, auto-cured and CAD/CAM denture base acrylic resins.MethodsThis study was conducted at the Advanced Dental Research Laboratory Center of King Abdulaziz University from March to June 2017. Three denture base materials were selected: heat cure poly-methylmethacrylate resin, thermoplastic (polyamide resin) and (CAD\\CAM) denture base resin. Sixty specimens were prepared and divided into three groups, twenty in each. Each group was divided according to the polishing techniques into (Mech P) and (Chem P), ten specimens in each; surface roughness and wettability were investigated. Data were analyzed by SPSS version 22, using one-way ANOVA and Pearson coefficient.ResultsOne-way analysis of variance (ANOVA) and post hoc tests were used for comparing the surface roughness values between three groups which revealed a statistical significant difference between them (p1<0.001). Heat-cured denture base material of (Group I) in both methods, showed the highest mean surface roughness value (2.44±0.07, 2.72±0.09, Mech P and Chem P respectively); while CAD\\CAM denture base material (group III) showed the least mean values (1.08±0.23, 1.39±0.31, Mech P and Chem P respectively). CAD/CAM showed the least contact angle in both polishing methods, which were statistically significant at 5% level (p=0.034 and p<0.001).ConclusionMechanical polishing produced lower surface roughness of CAD\\CAM denture base resin with superior smooth surface compared to chemical polishing. Mechanical polishing is considered the best effective polishing technique. CAD/CAM denture base material should be considered as the material of choice for complete denture construction in the near future, especially for older dental patients with changed salivary functions, because of its wettability.

Role and effect of mechanical polishing on the enhancement of the duplex mechanical attrition/plasma nitriding treatment of AISI 316L steel

This paper analyses a recently developed duplex process combining a Surface Mechanical Attrition Treatment (SMAT) with low-temperature plasma nitriding. The thickness of the nitrided layer significantly increased by adding a polishing step between SMAT and plasma nitriding at 425°C for AISI 316 austenitic steel. Contrarily it was also observed that without this polishing step the hardness decreased and the thickness and the homogeneity of the nitrided layer diminished with respect to the standard duplex process. The reason for this phenomenon is not well understood.Therefore, the aim of this investigation is to characterize and to discuss the effect of SMAT on the nitrogen diffusion into an austenitic stainless steel AISI 316 subjected to the duplex surface treatment. A second objective is to study the effects of the intermediate polishing step on the friction coefficient and hardness. In order to better understand the link between the generated microstructures and the diffusion kinetics and tribological responses, samples have been characterised by many different techniques such as Optical and Scanning Electron Microscopy (OM and SEM), X-Ray diffraction, hardness and ball-on-disc tests. Special attention was paid to the formation of oxide layers. The superficial and in-depth chemical composition of the SMATed samples were characterised by Energy Dispersive X-ray spectrometry (EDS) and Glow Discharge Spectrometry Profiles (GDOES), respectively.

The effect of mechanical polishing and finishing on the corrosion resistance of AISI 304 stainless steel

The aim of the present work was to study the influence of surface finishing on the corrosion resistance of AISI 304 stainless steel samples. Samples were submitted to lathe-turning, milling, lapping and grinding. Roughness parameters were determined by confocal laser scanning microscopy (CLSM). The corrosion resistance was evaluated using potentiodynamic polarisation curves and the corrosion morphology was assessed using CLSM and scanning electron microscopy. The results showed that the surface state had a remarkable influence on the corrosion behaviour of the samples, especially surface imperfections, whereas the roughness parameters did not directly correlate with the corrosion resistance.

Freestanding GaN 기판의 Ga-polar 면에 기계적 연마 방법을 적용한 Bow 제어 및 그 특성 연구

In this paper, we have studied the effect of mechanical polishing to Ga-polar face for reducing the wafer bowing and strain in free-standing GaN. After the mechanical polishing to Ga-polar face, the bowing of the free-standing GaN substrate significantly decreased with increasing the size of diamond slurry, and eventually changed the bowing direction from concave to convex. Furthermore, the full width at half maximum (FWHM) of high-resolution X-ray diffraction (HR-XRD) were decreased, especially the FWHM of (1 0 2) reflection for 1.0 μm size of diamond slurry was significantly decreased from 630 to 203 arcsec. In the case, we confirmed that the compressive strain in Ga-polar face was fully released by Raman measurement.

Thermal Effects of Mechanical Polishing and Conditioning on Polishing Pads

Polishing process is a primary technique for planarization of material surface in manufacture fabrication. The pad structure and its material properties are important to determine the polish rate and planarity that can be achieved by the polishing process. Besides, the pad conditioning is used to regenerate the surface of the polishing pad surface by breaking up the glazed areas. Because the polishing and pad conditioning mechanism is inadequately understood and because higher levels of pad polishing performance are desired, the investigation of experiment becomes more important.In this paper, a high precision polishing machine has established. With an improved design, a test rig can be easily used to simulate the polishing, pad conditioning process and acquire the signals of temperature. The temperature of test pads (i.e. Rodel IC1000A, Rodel IC 1000B and Opetech SB 660) is measured during polishing and pad conditioning process. For the self-design test rig, its surface temperature is measured by T-type thermocouples screwed behind the polishing (or conditioning) interface of the carrier. The experimental results provide a temperature index to end-point-detection and contribute to understanding of the mechanism on polishing pads.

EFFECT OF POLISHING ON THE FRICTION BEHAVIORS AND CUTTING PERFORMANCE OF BORON-DOPED DIAMOND FILMS ON WC-Co INSERTS

Boron doped ( B -doped) diamond films are deposited onto WC- Co inserts by HFCVD with the mixture of acetone, trimethyl borate ( C 3 H 9 BO 3) and H 2. The as-deposited B -doped diamond films are characterized with scanning electron microscope (SEM), X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, 3D surface topography based on white-light interferometry and Rockwell hardness tester. The effects of mechanical polishing on the friction behavior and cutting performance of B -doped diamond are evaluated by ball-on-plate type reciprocating tribometer and turning of aluminum alloy 7075 materials, respectively. For comparison, the same tests are also conducted for the bare WC- Co inserts with smooth surface. Friction tests suggest that the unpolished and polished B -doped diamond films possess relatively low fluctuation of friction coefficient than as-received bare WC- Co samples. The average stable friction coefficient for B -doped diamond films decreases apparently after mechanical polishing. The values for WC- Co sample, unpolished and polished B -doped diamond films are approximately 0.38, 0.25 and 0.11, respectively. The cutting results demonstrate that the low friction coefficient and high adhesive strength of B -doped diamond films play an essential role in the cutting performance enhancement of the WC- Co inserts. However, the mechanical polishing process may lower the adhesive strength of B -doped diamond films. Consequently, the polished B -doped diamond coated inserts show premature wear in the machining of adhesive aluminum alloy materials.

Microwave plasma deposition and mechanical treatment of single crystals and polycrystalline diamond films

The effect of mechanical polishing on the surface topography of mono-and polycrystalline diamond films produced by microwave plasma deposition and synthetic diamond crystals is investigated. The values of the temperature and friction coefficient of diamond films during polishing on the cast iron disk are measured. After finishing treatment, the surface roughness of a single crystal diamond is ∼0.5 nm and that of a polycrystal one is ∼8.1 nm. Because of the difference in wear rate of misoriented crystallites in the diamond film, nanosteps are formed on the grain boundaries.

Effect of mechanical polishing on corrosion behavior of Hastelloy C22 coating prepared by high power diode laser cladding

Hastelloy C22 coatings were prepared on mild steel by high power diode laser cladding technique. In order to investigate the effect of mechanical polishing on corrosion behavior, the coatings with original surface (coating C1) and new surfaces after mechanical polishing away of 0.3mm (coating C2) and 0.6mm (coating C3) in depth were studied. Their microstructures and compositions were measured, and corrosion resistance in seawater was studied. The planar, cellular and dendritic solidifications were found from the coating/substrate interface to the top surface of coatings. In coating C1, smallest size primary solidification containing mainly Ni and largest quantity of eutectic networks composed of Cr, Mo and W are dominant, and harmful carbide M(Cr, W)2C is found. While Mo6Ni6C phase exists only in coatings C2 and C3. The open circuit potential and electrochemical impedance spectroscopy of coating C1 are higher within two days, and then lower later than the other two coatings. Coatings C2 and C3 display larger stable radius of capacitive loop and lower corrosion current density owing to higher contents of Cr and Mo, as well as no harmful carbide at surface, which reveals higher corrosion resistance and lower corrosion rate than coating C1. Consequently, properly mechanical polishing of original coating surface is beneficial for improving its corrosion resistance.

The effect of mechanical and chemical polishing techniques on the surface roughness of heat-polymerized and visible light-polymerized acrylic denture base resins.

The purpose of this study was to compare the effects of mechanical polishing (MP) and chemical polishing (CP) on the average surface roughness (Ra) of heat-cured (HC) and light-cured (LC) denture base acrylic resins. A total of 120 specimens (30×15×3mm) were prepared from one HC and one LC acrylic resin. To remove nodules and gross surface irregularities, all specimens were finished with a lathe-mounted small acrylic bur and 360-grit sandpaper. Ten finished specimens of each acrylic resin were randomly assigned to each of six polishing techniques: Resilit High-luster Polishing Liquid (RHPL), Universal Polishing Paste, Abraso-star K50, pumice, Jet Seal Liquid, or Acrypoint. MP was performed with an automatic polishing machine for 2min, under 50rpm and 500g of load. CP was performed by immersing the HC and LC specimens in preheated methyl methacrylate at 75±1°C for 10s. The surface roughness of the acrylic resin specimens was measured with a contact profilometer. The Ra values were analyzed by two-way analysis of variance, post hoc Scheffe's test, and paired t-test (p⩽0.05). Polished and tested acrylic resin surfaces were evaluated by scanning electron microscopy. MP was more effective than CP. The smoothest surface was obtained with the use of the RHPL on the LC (0.05±0.01μm) or HC (0.07±0.01μm) acrylic resin. Two-way ANOVA showed a statistically significant difference between MP and CP. MP produced the smoothest surface of denture base acrylic resin. The mean surface roughness values after MP and CP were not influenced by the type of acrylic resin.

Indentation Size Effect (ISE) in Copper Subjected to Severe Plastic Deformation (SPD)

The characteristic length scale of deformation in copper specimens subjected to severe plastic deformation (SPD) through surface mechanical attrition treatment (SMAT) was studied with indentation experiments. Annealed copper disks were shot peened with 6-mm diameter tungsten carbide spheres with an average velocity of 2.3 m/s for 15 minutes in a vibrating chamber. The SMAT-treated specimens were cross-sectioned, and the exposed face was studied under nanoindentation in order to determine the effect of dislocation density on surface hardness and indentation size effect (ISE). Since the specimen preparation of the exposed face involved mechanical polishing, which in turn introduced additional SPD on the indenting face, the effect of mechanical polishing on hardness measurement was investigated first. To this end, the mechanically polished specimens were subjected to various durations of electrochemical polishing. Hardness measurements on these specimens showed that the effect of mechanical polishing was substantial for both microindentation and nanoindentation, the impact being significantly larger for nanoindentation. Consequently, the measured depth of influence of the SMAT process, determined on specimens subjected to longer durations of electrochemical polishing, shows larger values compared to those previously reported in the literature. The ISE shows a bilinear relationship between the square of hardness and the reciprocal of indentation depth. The slope of this behavior, corresponding to smaller indentation loads, which is a measure of the ISE associated with a strain gradient, shows a power-law relationship with an increase in the distance away from the SMAT surface, instead of the constant value expected with the Nix–Gao type model.

The effect of mechanical polishing on current annealed Co67Fe5Si15B13amorphous ribbons: magnetoimpedance response

A systematic current annealing treatment to achieve a high magnetoimpedance (MI) response in CoFeSiB amorphous ribbons is demonstrated. After current annealing in the present of air, although transverse permeability can increase but because of a significant surface oxidization, condition to reach a high MI response cannot be achieved. Additionally, this process leads to asymmetric MI response. In this paper, the effect of mechanical polishing of samples after current annealing is studied. We show a significant MI change by removing the hard magnetic phase on sample surface after current annealing. Results are useful and promising to be employed to reach high MI response for sensing applications.

Potential and pH dependence of photocurrent transients for boron-doped diamond electrodes in aqueous electrolyte

Using illumination at energies below the intrinsic diamond energy gap, photocurrent transients have been recorded for boron-doped diamond (BDD) as an electrode in an aqueous electrolyte of 0.1M KH2PO4. The commercially-supplied BDD was in the form of a free-standing, polycrystalline film grown by chemical vapour deposition (CVD), with a boron acceptor concentration of ≥1020cm−3. The effects of mechanical polishing of the BDD, of electrochemical hydrogen evolution and of electrochemical oxygen evolution (in 0.1M KH2PO4), on the potential dependence of the photocurrent transients have been examined. Measurements of the cathodic photocurrent at light switch-on have been used to determine the photocurrent onset potential as a measure of the flatband potential. Comparison with and between related literature observations has shown broad agreement across considerably varying BDD/electrolyte systems. The flatband potential shifted positively following electrochemical oxygen evolution, indicating the formation of oxygen-containing groups on the diamond surface, these increasing the potential drop across the Helmholtz layer. For the electrochemically oxidised electrode, the cathodic photocurrent transient at a fixed potential changed reproducibly with changing solution pH, owing to the participation of the oxygen-containing surface groups in acid–base equilibrium with the solution. This clear demonstration of BDD as a photoelectrochemical pH sensor is in principle extendable to mapping the spatial variation in pH across a BDD surface by use of a focussed light spot.

The effect of mechanical and chemical polishing techniques on the surface roughness of denture base acrylic resins

Smooth polished surface of dental prostheses is important to prevent bacterial colonization and plaque accumulation. The acrylic base of prosthodontic appliances needs to be adjusted by grinding which often alters the surface of the denture base. It is therefore important to know how different polishing techniques affect surface roughness of acrylic resin. The aim of this study was to evaluate the effect of mechanical polishing (MP) and chemical polishing (CP) on the surface roughness of heat cured (HC) and auto cured (AC) denture base acrylic resins. Sixty acrylic resin specimens (30×15×3mm) were made for each of the two types of acrylic resins. Thirty HC specimens received mechanical conventional lathe polishing using cone with pumice slurry and soft brush with chalk powder. The other thirty HC specimens received chemical polishing by immersing in methyl-methacrylate monomer heated to 75°C±1°C for 10s. The sixty AC specimens received mechanical and chemical polishing in the same manner. Surface roughness was measured using surface analyzing instrument in microns. The data were statistically analyzed by two-way analysis of variance (ANOVA) followed by post hoc Tukey's test (α=0.05). THE SURFACE ROUGHNESS MEAN IN MICRONS IN ORDER OF DECREASING VALUES WERE: CP-HC: 1.4132μm; CP-AC: 1.3494μm; MP-AC: 0.7364μm and MP-HC: 0.6333μm. Two-way ANOVA revealed that the MP-HC was significantly different from CP-HC and CP-AC (P<0.05). The MP-AC is also significantly different from CP-HC and CP-AC (P<0.05). There was no significant difference between MP and CP of HC and AC acrylic resin groups. It can be concluded that MP produced significantly smoother surfaces than CP. The surface roughness obtained by MP was not influenced by acrylic resin type where as this was not true for CP.

Corrosion behaviour of mechanically polished AA7075‐T6 aluminium alloy

AbstractIn the present study, the effects of mechanical polishing on the microstructure and corrosion behaviour of AA7075 aluminium alloy are investigated. It was found that a nano‐grained, near‐surface deformed layer, up to 400 nm thickness, is developed due to significant surface shear stress during mechanically polishing. Within the near‐surface deformed layer, the alloying elements have been redistributed and the microstructure of the alloy is modified; in particular, the normal MgZn2 particles for T6 are absent. However, segregation bands, approximately 10‐nm thick, containing mainly zinc, are found at the grain boundaries within the near‐surface deformed layer. The presence of such segregation bands promoted localised corrosion along the grain boundaries within the near‐surface deformed layer due to microgalvanic action. During anodic polarisation of mechanically polished alloy in sodium chloride solution, two breakdown potentials were observed at −750 mV and −700 mV, respectively. The first breakdown potential is associated with an increased electrochemical activity of the near‐surface deformed layer, and the second breakdown potential is associated with typical pitting of the bulk alloy. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Effect of vacuum ion-plasma treatment on the electrochemical corrosion characteristics of titanium-alloy implants

The effect of mechanical polishing and various types of vacuum ion-plasma treatment of model implants made of VT1-0, VT20, and VT6 titanium alloys on their electrochemical corrosion characteristics in a 0.9% NaCl solution (Ringer’s solution) is studied. Ion nitriding and the evaporation of a titanium nitride coating are shown to form a surface structure that provides an increase in the hardness, wear resistance, and corrosion resistance of these implants.

An atomic force microscopy study of the effects of surface treatments of diamond films produced by chemical vapor deposition

Diamond films produced by chemical vapor deposition (CVD) technique must be polished and machined in order to be used for many applications (windows, heat spreaders, surface acoustic wave devices, etc). We present an Atomic Force Microscopy study of the effects of mechanical polishing, hydrogen plasma etching, and ion implantation followed by annealing and chemical etching, on the morphology of Microwave Plasma CVD polycrystalline diamond films. Both growth and nucleation sides of 0.3–0.5 mm thick free-standing films were characterized. We found that grain boundaries and anisotropy of mechanical properties (hardness and wear rate) mostly contribute to the overall roughness of Microwave Plasma CVD diamond films, which is below 0.2 nm at the single-grain scale. The further deposition of a diamond overlayer, even of small thickness, on highly polished polycrystalline diamond, results in a variety of growth modes and different growth rates depending on the grain orientation, leading to the roughness increase. Hydrogen plasma etching proved to be effective for inducing morphological and chemical changes on the surface, while an ion implantation/annealing/etching can be used for precise removal of thin diamond layers. The latter approach is promising for diamond lithography.