Mechanical Scratches Research Articles

UV-OZONE Treatment for Suppressing Surface Damages on Silicon Solar Cells.

In the preparation process of c-Si solar cells, qualified Si wafers must be processed through mechanical processing during manufacturing. Most of these processes involve mechanical processing, which inevitably results in severe mechanical damage layers and a wafer surface with large roughness. The current industry practice involves etching of the damage layer using an acid/alkali solution, and it is usually followed by deposition of additional passivation layers in the subsequent processes. However, even with these treatments, there still remain non-negligible microscopic saw damage and scratches on the wafer surface, which hinder the urgent development of a higher conversion efficiency of solar cells. Here, we provide a simple method to effectively suppress the impact of this surface damage. UV-OZONE treatment, which involves generation of an oxide layer and subsequent cleaning with hydrofluoric acid, leads to the effective regain of solar cell performance due to the passivation of dangling bonds and removal of sharp microstructures based on the creation of mechanical scratches. In addition, PEDOT:PSS/n-Si solar cells were prepared to exploit their strong surface dependence to investigate the effect of scratches on the overall performance. These results further validate the impact of scratches on solar cells, and a simple and effective method for surface damage suppression is provided.

Fabrication of a multiple-self-healing and self-cleaning polymer coating for mechanical-damaged optical glass surface

Mobile screens and optical glass devices encounter formidable engineering and technological bottlenecks in achieving irreversible restoration from surface mechanical scratches. Conventional methodologies involving glass surface micromachining and coatings technology have proven inadequate in effectively addressing the multiple recovery of optical transparency. Here, the synergistic integration principle of inorganic rigid cage-like structures and organic flexible chain segments is employed. A bionic “octopus” textured surface pattern, featuring ordered arrays of nano nodes acting as “post stations” and micro-nano wrinkles serving as “channels”, is one-step fabricated by a dipping-curing coating process. The polymer coating exhibits smooth, transparent, and multiple-self-healing function with patterned antifouling. Introducing and matching the coating onto mobile screens, transparency of wiped/scratched glass is significantly restored by the synergistic use of protonic/non-protonic solvent systems in a dipping-assisted healing process. Intriguingly, the coating achieves surface/internal pattern reconstruction along with excellent transparency, antifouling, and interfacial adhesion mechanical properties, characterized by surface micro-nano textures and internal micro-nano spheres organization, after undergoing multiple treatments with the biocompatible disinfectant and cleaning agent ethanol. In the future, it is expected to develop highly versatile engineering materials for mobile screens, optical lenses and automotive glass, enabling multiple self-healing, self-cleaning, and antifouling properties with broad industrial applications.

Epoxy-based high-k composite vitrimer: With low dielectric loss, high breakdown strength and surface electrical damage repairability

High dielectric constant/permittivity (high-k) polymer-matrix composites (PMCs) are widely used in the electronics and electrical industries since their high energy density, ease of processing and light weight. However, the high dielectric permittivity (εr) usually leads to a significant increase in dielectric loss (tanδ) and an obvious decrease in breakdown strength (Eb), which is still a major problem that restricts the development of high-k PMCs. In addition, to extend the service life, the next generation electrical/electronic components also demand materials have electrical damage repairability. In this study, a new epoxy-based high-k composite vitrimer was constructed. The dynamic disulfide bonds were introduced into the cross-linked network to provide the high-k composite vitrimer with excellent repairability, while the nanoparticle (NPs) fillers surfaces were modified by grafting disulfides to improve the dynamic rearrangement ability of the composite network and enhance the electrical properties of the high-k composite vitrimer. The results show that this high-k composite vitrimer has low tanδ and high Eb, which is about 0.025 (at 0.1 Hz and room temperature) and 26.0 kV/mm (under 50 Hz AC voltage of 1 mm samples), respectively. Moreover, it has excellent mechanical damages and electrical damages repairability. For mechanical damages, it can repair mechanical scratches by heating at 180 °C for 10 min. For surface electrical damages, it can also eliminate the residual carbons, regain the surface organic structure, and restore more than 94% insulation strength by thoil treatment under 80 °C for 60 min. This study provides a new reference method for the preparation of low tanδ, high Eb and repairable high-k PMCs.

ULTRASONIC METHOD FOR SURFACE TREATMENT OF ANISOTROPIC ELECTRICAL STEEL TO REDUCE ITS TOTAL MAGNETIC LOSSES FOR MAGNETIZATION REVERSAL

The paper describes an ultrasonic method for the formation of locally deformed zones (LDZ) in the form of mechanical scratches applied to the surface of anisotropic electrical steel of nuclear power plants to crush its domain structure in order to reduce the total magnetic losses Р. It is shown that, as a result of such processing, using the example of a 3407 type steel, the value of P decreases by an average of 10-15%. It has been established that exposure to ultrasound leads to a significant increase in the rate of scratching.

A New Slurry for Photocatalysis-Assisted Chemical Mechanical Polishing of Monocrystal Diamond

Diamond needs to have a perfectly smooth surface due to the growing requirements in the fields of electronic semiconductors, optical windows and high-fidelity loudspeakers. However, the polishing of diamonds is highly challenging due to their exceptional hardness and chemical stability. In this study, a new polishing slurry is prepared for the proposed photocatalysis-assisted chemical mechanical polishing (PCMP) approach to obtain an ultra-smooth surface for large-area diamond. The analyses and experimental findings revealed the significance of the photocatalyst, abrasive, electron capture agent and pH regulator as essential components of the PCMP slurry. TiO2 with a 5 nm pore size and P25 TiO2 possess improved photocatalysis efficiency. Moreover, diamond removal is smooth under the acidic environment of H3PO4 due to the high oxidation–reduction potential (ORP) of the slurry, and, during the methyl orange test, P25 TiO2 exhibits reasonable photocatalytic effects. Moreover, in 8 h, a smooth surface free of mechanical scratches can be obtained by reducing the surface roughness from Ra 33.6 nm to Ra 2.6 nm.

Extraction of pipeline defect feature based on variational mode and optimal singular value decomposition

Because the magnetic signal information of pipeline defects obtained by magnetic flux leakage detection contains interference signals, it is difficult to accurately extract the features. Therefore, a novel pipeline defect feature extraction method based on VMD-OSVD (variational modal decomposition - optimal singular value decomposition) is proposed to promote the signal to noise ratio (SNR) and reduce aliasing in the frequency domain. By using the VMD method, the sampled magnetic signal is decomposed, and the optimal variational mode is selected according to the rate of relative change (VMK) of Shannon entropy (SE) to reconstruct the signal. After that, SVD algorithm is used to filter the reconstructed signal again, in which the H-matrix is optimized with the phase-space matrix to enhance SNR and decrease the frequency domain aliasing. The results show that the method has excellent denoising ability for defect magnetic signals, and SNR is increased by 21.01%, 24.04%, 0.96%, 32.14%, and 20.91%, respectively. The improved method has the best denoising effect on transverse mechanical scratches, but a poor denoising effect on spiral welding position. In the frequency domain, the characteristics of different defects are varied, and their corresponding frequency responses are spiral weld corrosion > transverse mechanical cracking > girth weld > deep hole > normal pipe. The high-frequency band is the spiral weld corrosion with f1 = 153.37 Hz. The low-frequency band is normal with f2 = 1 Hz. In general, the VMD-OSVD method is able to improve the SNR of the signal and characterize different pipe defects. And it has a certain guiding significance to the application of pipeline inspection in the field of safety in the future.

Robust Transparent Titanium Dioxide Coating Based on the AACVD Process for Anticorrosion Marine Exploration.

Transparent and robust titanium dioxide (TiO2) coatings were prepared by the facile aerosol-assisted chemical vapor deposition (AACVD) method. The effects of deposition temperature and precursor concentration on the crystal growth and optical properties of TiO2 coating were investigated. It is found that the obtained TiO2 coating has strong adhesion to the substrate, which can effectively avoid mechanical scratches and wear by sharp objects, adhesive tape and steel wool. Besides, in the marine corrosion protection test, both the open circuit potential and electrochemical impedance of TiO2 coating immersed in artificial seawater for different times are greater than those of the bare S420 steel substrate. Particularly, the high-frequency phase angle of the TiO2 coating increases, and the impedance value at low frequency of 0.10 Hz is about 2 orders of magnitude higher than that of the bare S420 substrate. In addition, the significant decrease of corrosion products on the surface further proves that the deposited TiO2 coating exhibits better corrosion inhibition and excellent anticorrosion properties, which is expected in application of the surface coating protection of the marine exploration lens.

AUTOMATIC DETECTION OF SURFACE DEFECTS OF CERAMIC TILES

Ceramic tiles are one of the most demanded finishing materials, and the areas of their use are constantly expanding. The production of ceramic tiles is quite well automated, but the control of manufactured tiles for defects is usually not automated, that limits its speed and does not guarantee the necessary quality. The algorithm for detecting the main surface defects of ceramic tiles, namely, mechanical (scratches, cracks, etc.), geometric (chips on the corners, gouges or protrusions on the edges), color defects (blobs, spots, etc.) is proposed in the paper. It based on digital image processing of tiles and was implemented using the free library of algorithmic primitives OpenCV. The algorithm does not require the presentation of reference tiles. At the same time, a high speed of classifying monochrome tiles into fresh and defective ones is ensured and allows to organize the automatic control of plain tiles on the conveyor in real time with the probability of correct detections 97 %.

Synergistic effect of F- ions and scratch on the dynamic corrosion behavior of ZTi60

The dynamic corrosion behavior of ZTi60 in neutral NaCl solutions containing various F- concentrations was investigated using a rapid scratching equipment, and the effect of F- ions and mechanical scratches on passive film was discussed based on point–defect model. The results indicate that when F- concentrations are higher than critical value, F- ions can migrate from film/solution interface into passive film, and form fluorine-titanium complex. However, the critical F– concentrations for the intact and scratched Ti surface are different. The scratched surface with higher defect density and enrichment of F– around the scratched areas can be damaged at lower F– concentrations.

Surface planarization of zirconia ceramic achieved by polyacrylamide grafted nanodiamond composite abrasives through chemical mechanical polishing

Zirconia ceramics are the promising materials for cell phone backplanes in the 5G era, and smoother surfaces and higher removal efficiency are sought after for their precision machining. Although nanodiamond abrasives have high polishing rates, it is easy to bring mechanical scratches and pits on the ceramic surface because of their high hardness, resulting in degradation of the surface quality of the finished workpiece. Therefore, polyacrylamide grafted nanodiamond particles were prepared by solution polymerization method for polishing ceramic wafers. As confirmed by Fourier transform infrared spectroscopy (FTIR), the polyacrylamide has been grafted on the nanodiamond surface. According to the scanning electron microscopy (SEM) and particle size distribution, the composite abrasives have better dispersion than pure nanodiamond abrasives. The results of chemical mechanical polishing (CMP) experiments showed that the composite abrasives could reduce the average surface roughness (Sa, arithmetic mean height) of zirconia ceramic from 28.31 nm to 2.68 nm (scanning area is 500 μm × 500 μm), and the polishing rate remained high compared to pure nanodiamond abrasives, showing superior CMP performance. X-ray photoelectron spectroscopy (XPS) demonstrated that solid-phase chemical reactions occurred during the polishing process to form ZrSiO4. Meanwhile, contact-wear model combined with contact angle testing indicates that the introduction of polyacrylamide increases the contact area of the nanodiamond on the zirconia wafer surface, thereby significantly enhanced the mechanical effect.

Thermally triggered self-healing epoxy coating towards sustained anti-corrosion

Cracks and mechanical damages are unavoidable during the real-world application of protective epoxy coatings, resulting in localized failure, corrosion attack, and potential safety hazards. Herein, 2-aminophenyl disulfide (APD) was used as a hardener for the design and construction of a novel self-healing epoxy coating (EAPD coating) to recover the micro-scale mechanical scratches. The optical spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR) and electrochemical impedance spectroscopy (EIS) were employed to investigate the macro-micro surface morphologies, chemical compositions, self-healing behaviors, and corrosion resisting properties of the scratch-damaged and scratch-healed EAPD coatings. Due to disulfide-mediated radical exchanges and S–S bonds rearrangement, the developed EAPD coating exhibits superior thermally-triggered self-healing performance with mechanical scratches completely self-repaired after 20 min at 80 °C and sustainable recovered corrosion resistance. The created self-healing EAPD coating is thought to provide a new design strategy for the development of smart and multi-functional protective coating materials with intriguing properties.

Changes in surface roughness and microstructure of 45 steel after irradiation by electron beam

The electron beam technology was used to polish and strengthen the surface of 45 steel. It was established that the mechanical scratches on the surface of 45 steel disappeared completely, and the roughness was reduced to 0.412 ± 0.02 μm. The samples which were irradiated by electron beam contained three areas as follows: fusion zone, heated affected zone and based metal. The fusion zone was mainly composed of acicular martensite, the heated affected zone was composed of martensite and ferrite. The hardness of the 45 steel sub-surface layer was slightly higher than surface layer. The hardness can be increased from 290 HV to 912 HV.

Mechano-Induced Assembly of a Nanocomposite for "Press-N-Go" Coatings with Highly Efficient Surface Disinfection.

Using antimicrobial coatings to control the spread of pathogenic microbes is appreciated in public and healthcare settings, but the performance of most antimicrobial coatings could not fulfill the increasing requirements, particularly the ease of preparation, high durability, rapid response, and high killing efficiency. Herein, we develop a new type of mechano-induced assembly of nanocomposite coating by simple "Press-N-Go" procedures on various substrates such as glassware, gloves, and fabrics, in which the coating shows strong adhesion, high shear stability, and high stiffness, making it durable in daily use to withstand common mechanical deformation and scratches. The coating also shows remarkable disinfection effectiveness over 99.9% to clinically significant multiple drug-resistant bacterial pathogens upon only 6 s near-infrared irradiation, which can be further improved to over 99.9999% upon another 6 s treatment. We envision that the coating can provide convenience and values to control pathogen spread for easily contaminated substrates in high-risk areas.

Two-dimensional pressure field and backflow in the annular skirt of vortex gripper

The vortex gripper is a kind of pneumatic noncontact gripper that does not produce a magnetic field and heat. It can grip a workpiece without physical contact, which avoids any unintentional damage such as mechanical scratches, local stress concentrations, frictional static electricity, and surface stains. This study focused on the two-dimensional pressure distribution field on a workpiece surface under the vortex gripper. Theoretical, experimental, and computational fluid dynamics results were combined to study the backflow phenomenon in the annular skirt, which can decrease the gripper’s suction force after the maximum value is reached. First, the pressure distribution in the annular skirt was theoretically modeled. A comparison with the experimental results showed that increasing the gap height between the gripper and workpiece generates a circumferentially asymmetrical flow field in the skirt. Based on this, it was hypothesized that an airflow in the circumferential direction may exist. The experimental data and simulation results were analyzed under large gap height conditions to observe the backflow in detail and it was found that an uneven pressure distribution with positive and negative pressure regions generated by the uneven flow is the root cause of the backflow. Finally, the effect of the backflow on the flow field in two different flow regions (in the annular skirt and inside the vortex chamber) was analyzed and the reason why the suction force of the vortex gripper has a maximum value was determined.

Research on pipeline internal stress detection technology based on the Barkhausen effect

Focusing on the requirements of pipeline in-line testing for stress concentration, mechanical scratches and corrosion discrimination, a numerical calculation and experimental verification study of the internal testing excitation of oil and gas pipelines based on the Barkhausen effect (magnetic Barkhausen noise (MBN)) is carried out. This paper uses finite element calculation to determine the optimal position of the sensor, quantitatively analyses the influence of parameters, such as the excitation structure size and excitation intensity, on the magnetisation field of the pipeline and obtains the optimal exciting parameters for acquiring continuous Barkhausen signals, which can provide references for designing the pipeline in-line inspection gauge for stress concentration. The feasibility of the continuous Barkhausen noise (CBN) method for long-distance pipeline stress detection is verified by simulating the operating conditions of the internal detector in the pipeline using dynamic rotating excitation.

Self-assembly preparation of popcorn-like colloidal silica and its application on chemical mechanical polishing of zirconia ceramic

Traditional mobile phone backplane materials are difficult to meet the requirements of the 5G era, and zirconia ceramic is one of the most promising backplane materials. However, its precision machining is difficult due to the hard and brittle nature. In this work, a novel popcorn-like colloidal silica was prepared by the self-assembly growth of nanoparticles for chemical mechanical polishing of the yttria-stabilized tetragonal zirconia ceramic sheets. The surface of the popcorn-like colloidal silica particles has a noticeably uneven shape, and the particle size distribution is uniform. The chemical mechanical polishing results show that the material removal rate of the prepared popcorn-like colloidal silica is increased by about 50% compared with the spherical colloidal silica, and the surface morphology is also obtained improvement. In the process of chemical mechanical polishing, the particles form multi-point contact with the ceramic sheet, resulting in an increase in the coefficient of friction, which is beneficial to the tribochemical reaction. In addition, multi-point contact can distribute the load, make the indentation shallower, and help reduce mechanical scratches. In general, the expected results are expected to provide experimental basis for the optimization of the structure of chemical mechanical polishing abrasive particles.

Directly printing of upconversion fluorescence-responsive elastomers for self-healable optical application

Lanthanide ions (Ln3+) doped upconversion crystals (UCCs) have promising application in optical anti-counterfeiting device, biomedical sensors and volumetric displays. However, these designed optical devices cannot recover their functions after mechanical damage and scratches. Herein, the novel upconversion fluorescence-responsive disulfide crosslinked polyurethane (DSPU) self-healing elastomers were designed for the first time, including the impaction of red-green-blue UCCs into DSPU (DSPU-UCCs) films and screen-printed fluorescence patterns on DSPU films. The DSPU-UCCs films exhibit tunable red-green-blue upconversion emissions as well as favorable mechanical properties (1037% stretchability) and self-healing ability (97.8% efficiency). The further investigations of the surface scratches and rheology results show that the disulfide bonds offer more efficient metathesis efficiency at higher temperatures. Moreover, the fluorescence-responsive self-healing elastomers can be reprocessed and reshaped, thus showing outstanding recyclability and sustainability. Directly screen-printing method was employed to fabricate versatile fluorescence patterns on DSPU elastomers, which can replace the traditional methods of relying on high-cost molds or masks to fabricate patterns. Healing scratches electronic patterns and assembling a series of versatile fluorescence patterns suggest that the upconversion fluorescence-responsive DSPU elastomers are highly promising for implementation in practical applications.

Gap flow with circumferential velocity in annular skirt of vortex gripper

The vortex gripper is a noncontact gripper that uses vortex flow that enables it to grip objects without coming into physical contact with them, thus avoiding such damage to the workpiece as mechanical scratches, local stress concentrations, frictional static electricity, and surface stains. This study involves theoretically and experimentally investigating the flow characteristics of the gap flow with a rotational velocity component between the workpiece and the annular skirt of the vortex gripper. Based on this, we discuss the effect of an important structural parameter of the gripper, i.e., the width of the annular skirt, on its performance. We first propose a theoretical model of the pressure gradient of the gap flow in the radial direction, where the pressure gradient is determined by the viscous term dominated by radial velocity, and the inertial terms are dominated by the radial and circumferential velocities. According to this theoretical model, we then analyze the distributions of radial velocity and circumferential velocity in the radial direction when the gap between the workpiece and the gripper varies, and the influence of the viscous term and the inertial terms on the pressure gradient. Further, we clarify the significance of the inertial term dominated by circumferential velocity on the pressure distribution. The validity of the theoretical model was verified by comparing its output with the results of experiments. Finally, by analyzing the force characteristic curves and pressure distributions of the grippers with annular skirts of four widths, we concluded that an increase in the width of the annular skirt can increase the influence of the inertial term dominated by circumferential velocity, and can thus change the region of stable suspension of the gripper and increase its suction capacity.

Removing Stripes, Scratches, and Curtaining with Nonrecoverable Compressed Sensing.

Highly-directional image artifacts such as ion mill curtaining, mechanical scratches, or image striping from beam instability degrade the interpretability of micrographs. These unwanted, aperiodic features extend the image along a primary direction and occupy a small wedge of information in Fourier space. Deleting this wedge of data replaces stripes, scratches, or curtaining, with more complex streaking and blurring artifacts-known within the tomography community as "missing wedge" artifacts. Here, we overcome this problem by recovering the missing region using total variation minimization, which leverages image sparsity-based reconstruction techniques-colloquially referred to as compressed sensing (CS)-to reliably restore images corrupted by stripe-like features. Our approach removes beam instability, ion mill curtaining, mechanical scratches, or any stripe features and remains robust at low signal-to-noise. The success of this approach is achieved by exploiting CS's inability to recover directional structures that are highly localized and missing in Fourier Space.

Diamond nanoscale surface processing and tribochemical wear mechanism

Diamond is widely used in many fields due to its numerous properties. Chemical mechanical polishing can achieve ultra-smooth and low-damage surface processing of diamond. We carried out the chemical mechanical polishing experiment of single crystal diamond using W0.5 diamond powder as abrasive in aqueous H2O2. The smooth surface with roughness (Ra) values of 0.917 nm was obtained and no obvious mechanical scratches. In addition, the atom removal mechanism of Chemical mechanical polishing process on the diamond surface polished with diamond powder in aqueous H2O2 was elucidated using Reactive Force Field molecular dynamics simulations. Hydroxylation on the diamond surface plays a dual role in the removal process. The diamond structure after being oxidized is damaged so the CC bonds become weak. The C atoms on the diamond surface form stronger CC bonds with the C atoms in abrasive, then the C atoms are carried away due to the mechanical action of abrasive. This work helps understand the removal process of C atoms at the atomic scale in the CMP process and provide an effective method to realize ultra-smooth and low-damage surface processing of diamond.