Polishing Technique Research Articles

Efficient Ablation, further GHz Burst Polishing, and Surface Texturing by Ultrafast Laser

A large variety of ultrafast laser‐matter interaction regimes and different processed surface finishing qualities of stainless steel can be achieved by varying the laser processing parameters. The optimization of the laser fluence to the most efficient ablation also leads to the lowest surface roughness of the ablated material. High laser fluence together with a high pulse repetition rate leads to heat accumulation, which results in the formation of microstructures with various morphology and scales. The use of GHz bursts allows a rough stainless‐steel surface to be smoothed and even polished. In this work, the fast and high‐quality milling of 2.5D cavities is demonstrated. Laser beam spot optimization is used to increase the throughput of the high‐power femtosecond laser (67.8 W), resulting in an ablation rate of 13 mm3 min−1. The complex cavities are produced by laser milling and cutting in layers. The formation of surface structures on stainless steel because of laser irradiation has been demonstrated. The possibilities of further GHz burst polishing are examined on previously laser‐milled stainless steel using with lowest possible surface roughness. The ability to polish the surface with microstructures below the original roughness is demonstrated by bursts of ultrashort pulses with a repetition rate in the GHz range. It has been demonstrated that mold milling in stainless steel designed for LED diffusers can be fabricated using a modern femtosecond laser source together with beam size optimization technique for efficient ablation with low surface roughness, layer‐by‐layer milling techniques, and GHz burst polishing techniques.

Global flattening realization and kinematic analysis of UV-assisted low-speed 3D dynamic friction-polished diamonds

Diamond has attracted extensive attention from many scholars because of its unique properties. However, there are still bottlenecks in how to achieve high efficiency polishing and global flattening of diamond which restrict its application. The aim of this study is to obtain a globally homogeneous flattened diamond surface in macro dimension by introducing a compound motion of the polished workpiece. It is shown that ultra-smooth diamond surface machining with global flattening can be realized by UV-assisted low-speed dynamic friction polishing technique, and the typical roughness is 0.175 nm as measured by 3D optical surface profiler. These experimental results demonstrate that the catalytic phase transition process of UV light is the underlying mechanism to realize the diamond surface polishing under low rotational speed conditions. Additionally, the composite motion of the diamond sample with the metal disk brings large enhancement to the effect of polishing global flattening on the sample surface. The theoretical and experimental studies in this paper provide novel ideas for achieving efficient and polished global flattening of diamond.

Microscopic modeling and experimental investigation of inner surface magnetorheological polishing based on particle micromechanics

Traditional surface polishing methods are no longer able to meet the ultra-precision requirements of the high-tech industry for the inner surface of the pipe, but magnetorheological polishing technology is very suitable due to its advantages of high precision, fast controllability and good deposition stability. However, there is even less investigation on the microforce analysis, chaining mechanism and micromodeling methods of magnetorheological polishing fluid (MRPF), and the polishing mechanism of MRPF has not been explored yet. As a step to completely develop the magnetorheological polishing (MRP) technique, this paper proposed the simulation method of MRPF based on particle dynamics, and the shear stress model of magnetorheological fluid (MRF) is optimized under the action of the magnetic field after performing the chain simulation. On the basis of the optimized shear stress model and the hexagonal close-packed structure of MRF, the holding mechanism of polishing abrasive particles is explored for the MRPF and the corresponding holding models are proposed. Then, the shear yield stress models and material removal model are also established for the inner surface polishing, respectively. Eventually, the above theoretical analysis and related models have been verified though the polishing experiment of the titanium alloy pipe.

Noninvasive characterization methods for ultra-short laser pulse induced volume modifications

We present two noninvasive characterization methods to investigate laser induced modifications in bulk fused silica glasses. The methods discussed are immersion microscopy and scanning acoustic microscopy (SAM). SAM shows merits in measuring the distance from sample surface to the first detectable density change of the modification, while immersion microscopy offers a look into the modification. Both noninvasive methods are preferred over conventional polishing or etching techniques due to the facts, that multiple investigations can be done with only one sample and lower time expenditure. The type II modifications were introduced by focusing laser pulses with high repetition rates into the fused silica.

Structural and Color Alterations of Teeth following Orthodontic Debonding: A Systematic Review.

The objective of this study was to explore the effects of fixed orthodontic appliances on enamel structure by assessing microfractures, surface roughness, and alterations in color. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A systematic search of online databases was conducted using the keywords 'enamel' AND 'orthodontic debonding'. Eligibility criteria included both in vivo and ex vivo clinical trials conducted on human teeth. A total of 14 relevant papers were analyzed. Various instruments and techniques were utilized across different studies to assess surface roughness, color change, and surface fractures. The findings of this study suggest that ceramic brackets may lead to an increase in enamel fractures, particularly during bracket removal. The surface roughness of enamel exhibits variability depending on the adhesive substance and polishing methods used post-removal. Fixed orthodontic appliances could induce changes in enamel color, which may be alleviated by the use of nano-hydroxyapatite or specific polishing techniques. Further research is necessary to identify effective strategies for managing these color changes and improving the overall outcomes of fixed orthodontic treatment.

Investigations towards nanoscale precise polishing of Nb3Sn thin films for SRF applications

The superconducting radio frequency performance of Nb3Sn is significantly impacted by its near-surface composition and nanostructure. In this study, an innovative polishing technique for Nb3Sn thin films with nanoscale precision is proposed. Systematic angle-resolved X-ray photoelectron spectroscopy (ARXPS) analysis reveal that the mechanism of this polishing process involves the formation of a few nanometer-thick oxide layer on the film's surface, followed by the uniform removal of the oxide layers with HF rinse. It is approximated that the polishing depth achieved in a single cycle can reach several nanometers. Advanced material characterization demonstrates that optimized polishing process effectively eliminates compulsive tin droplets and potential tin-rich phases with poor superconductivity generated on the surface during the preparation of Nb3Sn thin films. Simultaneously, no additional impurity phase will be formed on the surface, and the surface roughness will remain undamaged. Meanwhile, the results of magnetic and electrical analysis show that the superconducting properties of the polished films are not affected. This polishing technique is anticipated to ease the stringent coating conditions for the preparation of high-performance Nb3Sn thin film superconducting cavity, and will be a valuable addition to the post-treatment process of Nb3Sn thin films.

Effect of chemical action on shear thickening polishing of YAG

The shear-thickening polishing (STP) method, a flexible polishing technique developed in recent years, was utilized to obtain high surface quality of yttrium aluminum garnet (YAG) crystal effectively. The effect of polishing slurry pH value, which characterizes the chemical action between slurry and YAG crystal, on the material removal rate and surface roughness of YAG crystal was investigated, and the mechanism of the chemical action between YAG and slurry in STP process was revealed through X-ray photoelectron spectroscopy (XPS) analysis. The influence of polishing speed and abrasive concentration, which were relating with mechanical action, on the polishing effects was also studied. The experimental results show that when the pH value of the polishing slurry is lower than 11, the dissociation of chemical bonds and the formation of new bonds on the surface of the YAG crystal are predominantly found, resulting in a lower material removal rate. While the pH value of polishing slurry reaches 13, a reaction layer consisting of Al2SiO5 and Y2SiO5, which has lower hardness than abrasive, is formed on the surface, and this reaction layer can be removed by mechanical action efficiently. The surface roughness Sa decreases from 60 ± 10 nm to 0.38 ± 0.06 nm in 15 min with MRR reaches 117.30 nm/min, which is 4.3 times higher than that of chemical mechanical polishing. Based on the results of XPS analysis, the material removal mechanism of YAG polished by STP is proposed. As revealed by the results, STP with chemical action provide a high efficiency polishing method for the high surface quality YAG crystal.

Effect of different beverages and polishing techniques on colour stability of CAD/CAM composite restorative materials.

The aim of this article was to compare the colour stability of short fibre-reinforced computer-assisted design/computer-assisted manufacturing (CAD/CAM) composite (SFRC CAD) to commercially available CAD/CAM materials following prolonged immersion in a variety of beverages. Furthermore, the influence of the polishing technique was evaluated. A total of 120 rectangular specimens (10 mm length × 14 mm width × 2 mm thickness) were prepared from SFRC CAD, IPS e-max, Cerasmart 270, Celtra Duo, Enamic, and Brilliant Crios. The specimens underwent polishing through either a laboratory polishing machine equipped with 4000-grit silicon carbide paper or chairside polishing using Sof-Lex spiral. Twenty specimens of each tested CAD/CAM material were randomly divided into four groups (n = 5) based on the staining solution used in order to evaluate the colour stability of the materials. Group 1: distilled water, Group 2: coffee, Group 3: red wine, Group 4: coke. Using a spectrophotometer, the colour changes (∆E) of all CAD/CAM materials were assessed at baseline, and after 1 and 12 weeks of staining. Three-way analysis of variance was used to analyse the data (α = 0.05). The staining solution and material type showed a significant influence on the CAD/CAM specimens' colour stability (p < 0.05), while polishing method had no significant influence (p > 0.05). The average ∆E values for specimens submerged in wine were considerably higher (p < 0.05) than those for the other solutions. SFRC CAD, Cerasmart 270, and Enamic displayed the highest ∆E values in wine (p < 0.05). The colour stability of tested SFRC CAD was comparable to other composite-based CAD/CAM materials, while IPS e.max exhibited the highest level of colour stability.

Investigating the impact of laser polishing parameters on surface roughness, mass ablation rate, and optical transmittance of 3D‐printed PLA substrates

AbstractLaser polishing technique is one of the most effective post‐processing methods for 3D‐printed Polylactic acid (PLA) substrates and has gained significant interest of scientific research community in past few years. This paper aims to investigate the effect of fill density, laser power, and scanning speed on the polishing responses of 3D‐printed PLA substrates. These include surface roughness, mass ablation rate, and optical transmittance of PLA substrates printed using the fused deposition modeling technique. The optical transmittance was measured using Fourier‐transform infrared spectroscopy technique and surfaces were characterized using scanning electron microscope, and optical microscope. Minimum surface roughness of 1.04 μm was achieved at 5% laser power and 55% fill density constituting a decrease of 61.8% from unpolished PLA (2.735 μm). The lowest mass ablation rate (0.015 μg/pulse) was observed for the specimens with 40% infill density. Higher scanning speed enhanced the molecular bonding in PLA‐55 specimen indicated by increased peak transmittance ratios of CH bonds at stretching (1.021) and bending modes (1.045).

Green chemical mechanical polishing of copper with 2,5-dihydroxy-1,4-dithianeas as the inhibitor: Experimental and theoretical studies

It is a great challenge to develop green chemical mechanical polishing (CMP) technique owing to the limited inhibitory performance of green inhibitors. In this study, 2,5-dihydroxy-1,4-dithiane (DHD) was found and utilized as a superior inhibitor in CMP slurry, which realized nanometer-scale smoothness for copper surface. The strong inhibition effect of DHD, in both static and dynamic situations, was demonstrated by microscopic observations and electrochemical characterizations. The effectiveness of DHD was achieved mainly through its chemisorption onto copper surface, determined by Langmuir adsorption isotherm. X-ray photoelectron spectroscopy and density-functional-theory calculations proved that the chemisorption occurred between the S atom of DHD and Cu. Overall, DHD as an efficient and eco-friendly inhibitor with low-cost exhibits immense potential for applications in chip fabrication, particularly at a low technology node.

Effect of Two Different Intraoral Polishing Systems on Surface Roughness, Color Stability, and Bacterial Accumulation of Zirconia-Reinforced Lithium Silicate Ceramic.

The aim of this study was to investigate the effects of two intraoral polishing methods on zirconia-reinforced lithium silicate ceramic after ultrasonic scaling. Thirty disc-shaped samples of zirconia-reinforced lithium silicate were constructed. Freshly extracted bovine teeth were collected and cleaned then the discs were cemented into a cavity prepared onto their labial surface. The samples were divided into three groups (10 samples per group); S: Scaling only, SE: Scaling followed by polishing using Eve Diapro lithium disilicate polishers, SD: Scaling followed by polishing using Diatech ShapeGuard ceramic polishing plus kit. The surface roughness was evaluated after scaling and polishing the samples. For color stability, the samples were stored for 12 days at 37°C in an incubator to simulate 1-year consumption of coffee. L*a*b* color parameters were assessed using VITA Easyshade Advance 4.0 before and after the staining procedure and the color difference was measured. Finally, bacterial accumulation was evaluated by incubating the samples with a suspension of Streptococcus mutans ( S. mutans), after that the S. mutans colonies were counted to obtain the values of colony-forming units (CFU). The final overall roughness, change in color and bacterial count were compared between all groups using one-way ANOVA and Tukey's post-hoc analysis. The Pearson correlation coefficient was used to determine the correlation between continuous variables. The cutoff for significance was chosen at p ≤ 0.05. Scaling induced surface roughness of the zirconia-reinforced lithium silicate ceramic was significantly decreased after using both intraoral polishing systems and this was accompanied by a significant decrease in color change and bacterial count. Intraoral polishing techniques can reduce the roughness of the surface of zirconia reinforced lithium silicate restorations induced due to scaling and subsequently reduce the stainability and bacterial accumulation.

Experimental study on ultrasonic-assisted electrochemical polishing of NiTi alloy

NiTi alloy has a wide range of applications due to its unique superelasticity and shape memory, the superelastic function of NiTi alloy made it had been applied in building shock absorption, advanced bearings and other scenes, the shape memory function made it also applied in the fields of aerospace engine heat exchanger, cardiac medical stent and so on. In order to made NiTi alloy better applied in practice and improve its surface quality, it was crucial to polish it. In this paper, a new method of ultrasonic-assisted electrochemical polishing of NiTi alloy was innovatively proposed, and an ultrasonic electrochemical polishing device was built independently. The effects of ultrasonic amplitude, voltage and temperature on roughness were explored by Box-Behnken experimental design method. The results show that after ultrasonic-assisted electrochemical polishing, the roughness Ra had been reduced from about 2 μm to the minimum of 0.048 μm. The surface quality of NiTi alloy was improved. The impact of micro-jet of cavitation bubble on NiTi alloy mainly occurs in the early stage, and the equivalent stress on the surface of NiTi alloy was annular, showing an increasing and decreasing trend. In the whole ultrasonic electrochemical polishing solution, a large number of micro-jets will impact the surface of NiTi alloy, thus realizing the material removal. This study enhances traditional electrochemical polishing techniques by integrating ultrasonic energy fields, thus broadening the scope of electrochemical polishing applications. Additionally, it presents a novel approach and establishes a foundation for the polishing of NiTi alloys with intricate geometries in additive manufacturing.

Surface Roughness Evaluation of Pre- Versus Post-Crystallization Polish of Two High-Strength Silicate Ceramics for Chairside CAD/CAM Technology

This in vitro study evaluated the surface roughness (Sa) of two high-strength silicate ceramics, lithium disilicate IPS e.max CAD, Ivoclar Vivadent (LDS group), and zirconia-reinforced lithium silicate Vita Suprinity, VITA Zahnfabrik (ZLS group). The surface roughness was investigated before and after milling using different polishing systems and timings relative to the final crystallization of the ceramics. Forty-eight samples per group were polished by a single calibrated operator using two polishing systems: Dialite LD (Brasseler) and Lithium Silicate Polishers (Meisinger) for the LDS group and Dialite LD (Brasseler) and Vita Suprinity Polishing Set Technical (VITA Zahnfabrik) for the ZLS group, both pre- and post-crystallization. Surface roughness was measured using a confocal laser microscope (OLS4000 LEXT/Olympus), with scanning electron microscopy (SEM) used to evaluate surface morphological changes. Significant differences in Sa values were found between baseline groups, with ZLS exhibiting lower values. All polishing methods significantly reduced surface roughness compared to baseline (p ≤ 0.05). No significant differences were found in LDS samples when polishing pre- or post-crystallization (p = 0.129), while for ZLS samples, post-crystallization polishing achieved significantly smoother surfaces (p &lt; 0.001). The study concluded that the choice of polishing system and timing did not significantly affect surface roughness for LDS. However, it is recommended that post-crystallization polishing be performed for the optimal smoothness of ZLS. This study aimed to evaluate the post-milling polishing procedures of CAD/CAM high-strength restorations, emphasizing the importance of an optimal surface roughness to prevent issues such as increased risk of abrasion on opposing teeth, enhanced plaque adhesion, and mechanical failures. Investigating these polishing techniques enables clinicians to optimize clinical performance, thereby improving the quality and longevity of high-strength silicate ceramics.

Angularly offset multiline dispersive optical phased array enabling large field of view and plateau envelope

We propose and demonstrate an angularly offset multiline (AOML) dispersive silicon nitride optical phased array (OPA) that enables efficient line beam scanning with an expanded field of view (FOV) and plateau envelope. The suggested AOML OPA incorporates multiline OPA units, which were seamlessly integrated with a 45° angular offset through a thermo-optic switch based on a multimode interference coupler, resulting in a wide FOV that combines three consecutive scanning ranges. Simultaneously, a periodic diffraction envelope rendered by the multiline OPA units contributes to reduced peak intensity fluctuation of the main lobe across the large FOV. An expedient polishing enabling the angled facet was diligently accomplished through the implementation of oblique polishing techniques applied to the 90° angle of the chip. For each dispersive OPA unit, we engineered an array of delay lines with progressively adjustable delay lengths, enabling a passive wavelength-tunable beam scanning. Experimental validation of the proposed OPA revealed efficient beam scanning, achieved by wavelength tuning from 1530 to 1600 nm and seamless switching between multiline OPAs, yielding an FOV of 152° with a main lobe intensity fluctuation of 2.8 dB. The measured efficiency of dispersive scanning was estimated at 0.97°/nm, as intended.

Heterogeneous integration of thick GaN and polycrystalline diamond at room temperature through dynamic plasma polishing and surface-activated bonding

Direct heterogeneous integration of GaN on diamond enhances device performance and reliability for high-power applications, while the implementation on thick GaN films and polycrystalline diamond (p-diamond) substrates remains challenging. In this study, the direct bonding between thick GaN films (∼370 μm) and p-diamond substrates was achieved. A dynamic plasma polishing (DPP) technique was adopted on the diamond to flatten surficial spikes from maximum 15 nm to 1.2 nm, obtaining a smooth surface with 0.29 nm Ra, achieving a robust GaN/diamond bonding with high bonding rate of ∼92% at room temperature combining the surface-activated bonding (SAB) method. The chemical status, thermal stress, and interfacial microstructures of GaN/diamond heterostructures were analyzed, revealing a residual stress of ∼200 MPa at the GaN/diamond interface, and the asymmetric increase of interfacial stress at rising temperature demonstrates the effectiveness of amorphous interlayer to release the stress.

High-Efficiency Polishing of Polymer Surface Using Catalyst-Referred Etching

Previously, we developed an abrasive-free polishing technique called catalyst-referred etching (CARE) for inorganic materials. In this method, the topmost site of the workpiece surface is preferentially removed via an indirect hydrolysis reaction promoted by a metal catalyst. In this study, we proposed applying the CARE method to polymer material polishing and demonstrated the polishing characteristics. Using the CARE method, polycarbonate, which has an easy cleavage of ester bond via hydrolysis, was polished, resulting in the smoothness of the surface roughness below 1.0 nm. Based on the surface observations, the removal mechanism was estimated as follows. Molecule chains are entangled to form clusters constituting the polymer surface and help determine the surface roughness. In the CARE method, the top of this cluster was selectively removed, thus creating a smooth surface. Polymers with C–C bonds, such as polymethyl methacrylate and fluorinated ethylene propylene, were also smoothed using the CARE method. These results indicate that the CARE method is highly effective in polishing polymer materials.

Analysis of Physical and Mechanical Properties of Universal Composites under Different Types of Polishing before and after Acid Challenge.

This study aimed to evaluate in vitro the degree of surface smoothness provided by two different polishing techniques and the effect of acid challenge on the alteration of surface roughness (Ra), microhardness (Knoop), and color (ΔE00) of three nanoparticulate composites, simulating 1 year of exposure to hydrochloric acid (HCl). Eighty specimens for each composite were divided into four groups (n = 240), being control without polishing, control with wear, WPC (wear + polishing with Cosmedent Kit), and WPB (wear + BisCover LV liquid polish). Repeated measures ANOVA was applied for Ra and Knoop Microhardness. For the color (ΔE) three-way ANOVA was applied. In cases of statistically significant the Tukey posttest was applied (α = 0.05). Both types of polishing tested resulted in a surface smoothness below the critical value established by the studies (Ra ≥ 0.2 μm), even after immersion. The microhardness of all composite resins decreased after the challenges. The specimens immersed in HCl showed a lower microhardness (42.2 Kgf/mm2) when compared to the specimens immersed in artificial saliva (44.7 Kgf/mm2). Regarding the color change, the composites presented values compatible with clinical acceptability, with a statistically significant difference only between the control group and the other types of polishing for the Z350 XT resin (ΔE00 = 3.78). It was concluded that both mechanical and chemical polishing produced a satisfactory surface smoothness, even after immersions in artificial saliva and HCl. The microhardness of the composites was affected by the challenges and the composites tested were within clinical acceptability with regard to color change.

Effect of dry and wet finishing and polishing on color change and opacity of nanofill and nanohybrid composites

BackgroundAs superior esthetic is one of the main reasons for using composite resins, it is very important to be familiar with factors and techniques affecting their optical properties and appearance.AimThe aim of this study was comparing the effect of finishing and polishing with and without water coolant, on the color change and opacity of composite resin materials.MethodsComposites used for preparing samples were Z250 (microhybrid), Z350XT (nanofilled), and Z550 (nanohybrid). Then divided into 4 groups of 5 depending on finishing and polishing technique (dry or wet) and time (immediate and after twenty-four hours). After polishing, samples were assessed using a spectrophotometer. Color change and opacity were determined. Data was analyzed using Kolmogorov-Smirnov, ANOVA and Tukey HSD tests.ResultsType of material at both time had a significant effect on ΔE and opacity. Our results in dry and wet technique immediately(T0) showed that the highest and lowest ΔE and opacity belong to Z350XT (p < 0.001). After Twenty-four hours (T24), opacity of Z250 in wet condition was higher than dry condition (p < 0.001).ConclusionsWet or dry technique was only effective on color in immediate polishing. Regarding opacity, technique was only effective in case of delayed polishing.

Investigation of cluster magnetorheological electro-Fenton composite polishing process for single-crystal GaN wafer based on BBD experimental method

A cluster magnetorheological (MR) electro-Fenton composite polishing technique was proposed in this work, which can realize high efficiency, ultra-smooth and damage-free of GaN wafer by the synergistic effect of electro-Fenton reaction and flexible mechanical removal of MR polishing. The key parameters of electro-Fenton were optimized through methyl orange degradation experiments based on BBD experimental method. The results showed that the decolorization rate had a strong dependence on H2O2 concentration, Fe–C concentration and pH value, where the decolorization rate had the maximum value when the H2O2 concentration of 5 wt%, Fe–C concentration of 3 wt% and pH value of 3. Compared with the Fenton reaction, the decolorization and REDOX potential of methyl orange solution were significantly improved in the electro-Fenton reaction. Furthermore, the process parameters of the cluster MR electro-Fenton composite polishing were optimized to obtain the best polishing result, which was realized under the conditions of 3 wt% diamond (grain size: 0.5 µm), a polishing gap of 0.9 mm and a polishing time of 60 min. The novel method achieved a material removal rate of 10.79 μm h−1, which was much higher than that of the conventional technique. In addition, an ultra-smooth and damage-free surface with a roughness of 1.29 nm Ra was obtained.

Spectrophotometric evaluation of color stability of composite resin after exposure to cold drinks: An in vitro study.

The aim of this study was to evaluate the color stability of two composite resins after exposure to beverages such as Cola, Pepsi, Red Bull, and distilled water after 15 days. The color stability of a microhybrid and nanohybrid composite was evaluated after storage in distilled water, Coca-Cola, Pepsi, and Red Bull for 15 days. Color measurement was done using a reflectance spectrophotometer based on the CIE L*a*b* color scale. All tested resin composites showed color change after a period of 15 days. One-way analysis of variance and Tukey post hoc were done to assess the significance of color change within the group and an independent t-test was done to assess the change between micro and nanohybrid composite. Among the resin composites studied, microhybrid composite was found to be more color stable. The microhybrid and nanohybrid composite discolored most in Coca-Cola and Pepsi. In both groups, distilled water showed very less color change. Every endeavor should be undertaken to minimize the potential for discoloration in composite restorations by employing meticulous polishing techniques and also to use newer composite material with submicron particles. Furthermore, it is imperative to educate patients about the likelihood of the restoration being susceptible to staining from various beverages.