Surfaces Of Various Materials Research Articles

High-Contrast Marking of Stainless-Steel Using Bursts of Femtosecond Laser Pulses.

The marking and surface structuring of various materials is important in various industrial fields such as biomaterials, luxury goods, anti-counterfeiting, automotive and aerospace, electronics and semiconductor industries, and others. Recent advances in laser technology, such as burst-mode lasers, have opened new ways of affecting the surfaces of various materials, inducing a different appearance and/or properties of the laser-exposed areas. From earlier studies, it is known that when splitting a single pulse into multiple pulses and thus creating a quasi-MHz-GHz repetition rate regime, it is possible to increase not only the ablation efficiency but it also provides the possibility to tune the heat in-flow into the surface. Such new regimes enable the control of the surface roughness as well as the optical properties and corrosion resistance. In this work, we analyze the effect of the different burst-mode regimes for the marking of stainless-steel samples, aiming to produce high-contrast marking having different shades of black/white color (black-gray-white). Moreover, we investigate the angular dependence of the reflected light after laser treatment numerically from the measured surface morphology.

THE EXPERIMENTAL STUDY OF EVAPORATION OF WATER AND NANOFLUID DROPLETS ON THE SURFACES OF MATERIALS WITH DIFFERENT THERMAL CONDUCTIVITIES

The article presents the results of experimental studying evaporation of water and nanofluid droplets on the surfaces of various materials. Plates made of materials with significantly different thermal conductivity coefficients have been used as substrates: copper (λ = 401 W/m °С), Teflon (λ = 0.25 W/m °С), and extruded foamed polystyrene (λ = 0.03 W/m °С). In the experiments, the evaporation of water and nanofluid droplets with a volume of 5 μL has been considered at a constant temperature and humidity of the ambient air. A nanofluid (a mixture of water with gold nanoparticles) has been prepared by laser ablation. The concentration of nanoparticles in the nanofluid is about 0.1 wt %. Infrared thermography has been employed to determine the average temperatures of evaporating droplet surfaces. The results obtained have shown that, for all studied materials, the surface temperature of evaporating water droplets is higher than the temperature of adiabatic evaporation. Therewith, the lower the thermal conductivity coefficient of a substrate material, the lower the surface temperature of the droplet and the longer the time of its evaporation. The performed experiments have shown that the minimum temperature of nanofluid droplets is lower than that of water droplets, and the evaporation time of nanofluid droplets is longer than that of water droplets on the corresponding surfaces.

Study on Ion Bombardment Semiconductor Shaped Self-Assembled Nanostructures

Through Surface nanopatterning induced by ion beam bombardment has become an effective nanostructure technology, in a short period, large-area patterning can be induced on the surface of various materials through ion bombardment technology, and island-like, porous, and corrugated morphology can be formed on the surface of the material, effectively improving its surface morphology. In this review, we provide an updated description of the progress made when ions bombard semiconductor surfaces, focusing on the influence of different parameters on the evolution of surface morphology. Secondly, the physical model of the evolution of surface nanostructures and the application of nanostructures generated by low-energy ion bombardment are summarized.

Glycopolymer-based multifunctional antibacterial hydrogel dressings for accelerating cutaneous wound healing.

Antimicrobial hydrogel dressings have received extensive attention for their wide and promising applications in preventing infections associated with wound healing. However, the development of versatile antibacterial hydrogels inevitably leads to complex structures, which restricts their applications. In this work, a multifunctional antibacterial hydrogel based on a reversible diolborate bond crosslinked network was prepared via the interactions between the zwitterionic glycopolymer poly[(2-methacryloyloxyethyl phosphorylcholine)-co-(N,N-dimethylacrylamide)-co-(2-lactobionamidoethyl methacrylamide)] (PMDL) and borax in conjunction with a simple mixing of Ag NPs within 10 s. The obtained PMDL-12%/borax/Ag NP hydrogel displays a rapid self-healing ability and excellent injectability, as well as good adhesiveness to biological tissues and surfaces of various materials. Moreover, the hydrogels exhibit efficient antibacterial activities against Escherichia coli and Staphylococcus aureus, which could prevent bacterial infections in wound care. The multifunctional hydrogel also shows good cytocompatibility and hemocompatibility. Importantly, in vivo wound healing evaluation of a mouse full-thickness skin defect model confirms that the hydrogel effectively accelerates cutaneous regeneration and wound healing by regulating inflammation and promoting collagen deposition. This multifunctional wound dressing hydrogel prepared using a facile strategy has promising application in biomedical areas.

Integrated Video and Acoustic Emission Data Fusion for Intelligent Decision Making in Material Surface Inspection System

In the field of intelligent surface inspection systems, particular attention is paid to decision making problems, based on data from different sensors. The combination of such data helps to make an intelligent decision. In this research, an approach to intelligent decision making based on a data integration strategy to raise awareness of a controlled object is used. In the following article, this approach is considered in the context of reasonable decisions when detecting defects on the surface of welds that arise after the metal pipe welding processes. The main data types were RGB, RGB-D images, and acoustic emission signals. The fusion of such multimodality data, which mimics the eyes and ears of an experienced person through computer vision and digital signal processing, provides more concrete and meaningful information for intelligent decision making. The main results of this study include an overview of the architecture of the system with a detailed description of its parts, methods for acquiring data from various sensors, pseudocodes for data processing algorithms, and an approach to data fusion meant to improve the efficiency of decision making in detecting defects on the surface of various materials.

True Atomic-Resolution Surface Imaging and Manipulation under Ambient Conditions via Conductive Atomic Force Microscopy.

A great number of chemical and mechanical phenomena, ranging from catalysis to friction, are dictated by the atomic-scale structure and properties of material surfaces. Yet, the principal tools utilized to characterize surfaces at the atomic level rely on strict environmental conditions such as ultrahigh vacuum and low temperature. Results obtained under such well-controlled, pristine conditions bear little relevance to the great majority of processes and applications that often occur under ambient conditions. Here, we report true atomic-resolution surface imaging via conductive atomic force microscopy (C-AFM) under ambient conditions, performed at high scanning speeds. Our approach delivers atomic-resolution maps on a variety of material surfaces that comprise defects including single atomic vacancies. We hypothesize that atomic resolution can be enabled by either a confined, electrically conductive pathway or an individual, atomically sharp asperity at the tip-sample contact. Using our method, we report the capability of in situ charge state manipulation of defects on MoS2 and the observation of an exotic electronic effect: room-temperature charge ordering in a thin transition metal carbide (TMC) crystal (i.e., an MXene), α-Mo2C. Our findings demonstrate that C-AFM can be utilized as a powerful tool for atomic-resolution imaging and manipulation of surface structure and electronics under ambient conditions, with wide-ranging applicability.

History, Current Practice, and the Future of Wound Care for Occupational and Physical Therapists.

History, Current Practice, and the Future of Wound Care for Occupational and Physical Therapists.

The Influence of Glow and Afterglow Cold Plasma Treatment on Biochemistry, Morphology, and Physiology of Wheat Seeds.

Cold plasma (CP) technology is a technique used to change chemical and morphological characteristics of the surface of various materials. It is a newly emerging technology in agriculture used for seed treatment with the potential of improving seed germination and yield of crops. Wheat seeds were treated with glow (direct) or afterglow (indirect) low-pressure radio-frequency oxygen plasma. Chemical characteristics of the seed surface were evaluated by XPS and FTIR analysis, changes in the morphology of the seed pericarp were analysed by SEM and AFM, and physiological characteristics of the seedlings were determined by germination tests, growth studies, and the evaluation of α-amylase activity. Changes in seed wettability were also studied, mainly in correlation with functionalization of the seed surface and oxidation of lipid molecules. Only prolonged direct CP treatment resulted in altered morphology of the seed pericarp and increased its roughness. The degree of functionalization is more evident in direct compared to indirect CP treatment. CP treatment slowed the germination of seedlings, decreased the activity of α-amylase in seeds after imbibition, and affected the root system of seedlings.

Industrial character recognition based on improved CRNN in complex environments

Automatic character recognition is being gradually adopted in several everyday applications. In industrial settings, it can free up manpower required for reading and tracking product information. However, character recognition in industrial environments is particularly challenging. The main challenges are as follows: (1) There are no publicly available datasets that would aid the development of robust industrial character recognition methods; (2) Industrial characters may be printed in complex and uneven shapes on the surface of various materials, resulting in blurred characters, low contrast and distortion; (3) Industrial character recognition in complex industrial environments can suffers from various difficulties, such as uneven lighting conditions, oxidation of characters caused by long-term storage, etc. To address these challenges, we propose a convolutional recurrent neural network based on a residual structure and a “Squeeze-and-Excitation” block, namely RS-CRNN. The feature extraction of this method is inspired by ResNet and SEnet, and the method uses gate recurrent units for sequence label prediction. The model was trained and tested on constructed real and synthetic datasets, and experimental results show that the method has better performance than state-of-the-art character recognition models.

Investigations for improving fatigue strength by low energy laser peening via bending fatigue test

Laser peening can introduce compressive residual stresses on the surface of various materials, thereby effectively prolonging their fatigue lives. In this study, the effects of laser peening with pulse energies of 20 and 70 mJ on residual stress and fatigue life were investigated on two types of HT780 box-welded specimens of different sizes, considering the realization of a portable laser peening system equipped with a small laser device with low pulse energy. As a result of such low pulse energy laser peening, it was found that the depth of compressive residual stress becomes shallower compared to the current laser peening with a pulse energy of 200 mJ, while the residual stress on the surface remains at the same level. Bending fatigue tests were conducted with the stress ranges at 100 and 150 MPa, which revealed that the fatigue life of the specimens with low pulse energy laser peening was at least 50 times and eight times longer than that of the as-welded specimens, respectively. Comparing the fatigue test results of different size specimens, it is clear that laser peening with low pulse energy is effective in extending the fatigue life of HT780 box-welded specimen regardless of its size.

Evaluation of the Level of Biotic and Abiotic Contamination of Surfaces Using the Principle of Light Absorption for the Purpose of Sanitary and Microbiological Control

Relevance. The environment, represented by many components, can have an unfavorable influence on human health. One of the components of air pollution, a solid-phase aerosol, that interacting with a droplet aerosol released from the mucous membrane of the upper airway of a sick person, forms dispersed structures containing various species of microorganisms. Dust fractions, being a source of microorganisms with a diverse phenotype, can become a useful object of environmental monitoring carried out for preventive purposes. Aims. Determination of the possibility of use of the physical phenomenon of light absorption for detection of the pollutions and their quantification on surfaces made from various materials and on environmental objects with unequal conditions of use.Materials and methods. The surfaces of various materials with natural and artificial contamination in the closed rooms of an educational institution were studied in order to classify the level of their biotic and abiotic contamination based on the analysis of the spectrum of absorbed and reflected radiation registered by the photodiodes of the prototype device. Internal control of the levels of biotic contamination of the examined surfaces was carried out with use of ATP-luminometer and a cultural method. Results. The third level classification of the contaminations on the surfaces in public areas: clean, uncertain and dirty was developed on the results of experimental studies with use of «PROBER» test system, expressed in units. Statistically significant differences in the indicators of the test system were confirmed in the study of surfaces with different levels of contamination (p < 0.01) and the correlation of the test system indicators with control measurements of the levels of surface contamination by ATPluminometer (φ * emp = 1.281) and a cultural method.Conclusions. Physical parameters such as the spectra of absorbed and reflected light and their differences can be used to determine the levels of dust contamination of surfaces in order to assess the safety of the environment for human health.

Luminescence of Reichardt's dye in polyelectrolyte-modified saponite colloids

Reichardt’s dye (RD) exhibits solvatochromic properties across the entire visible spectrum. This work reports, for the first time, luminescence of RD in colloidal systems of layered silicate saponite (Sap) modified with poly(diallyldimethylammonium) polycations (PDDA), and provides an interpretation of this unique phenomenon. The application of tailored theoretical chemistry methods such as DFT and other approaches supplies a theoretical interpretation of the phenomenon to supplement the results of the experiments. RD luminescence was achieved by preventing the movement of molecules and suppressing non-radiative relaxation processes. This effect only occurred if the negatively-charged phenolate group in the RD molecule interacted with the positively-charged groups of the PDDA cations, while at the same time the positively-charged pyridinium group was also adsorbed onto the negatively-charged Sap siloxane surface. Only at small coverage of the Sap surface by PDDA cations is there sufficient fixation of the RD molecules for them to exhibit luminescent properties. The results suggest that the application of this dye may be extended to luminescent probes, which could be used to characterize the distribution of charge centers on the surfaces of various materials, biopolymers, biological tissues, etc.

Silver nanoparticles embedded cotton swab as surface-enhanced Raman scattering substrate combination of smartphone app for detection of carbofuran residues

A surface-enhanced Raman scattering (SERS) substrate, consisting of a cotton swab with silver nanoparticles (AgNPs) embedded on common cotton, was fabricated in this study. The substrate consisted of AgNPs encapsulated in N-[3-(trimethoxysilyl)propyl]diethylenetriamine (ATS) hydrogels, and the resulting ATS-Ag SERS substrate presented good viscoelasticity, allowing it to conform to the surface of various materials of arbitrary roughness. The SERS peak intensity concentration change was rapidly captured and analyzed using a self-developed smartphone-based app system, which implements quantitative detection of carbofuran. The results showed that carbofuran can be detected with high sensitivity, with a linear range of 0.01–1.0 ppm and a detection limit of 0.05 ppm. In combination with a website, the proposed approach features high sensitivity, high simplicity of implementation, and a high throughput, which provides a promising means for the in situ determination of targets in practical applications.

Immobilization of phenol‐containing compounds via electrochemical activation of a urazole derivative

AbstractWe introduce an efficient method for the immobilization of phenolic compounds, based on 1,2,4,‐triazoline‐3,5‐dione (TAD), which selectively reacts with phenolic compounds at the α position to the phenolic hydroxyl group, ensuring intact phenol functionality, and therefore, maintaining the biological activity of the phenolic compound. We prepared self‐assembled monolayers on gold that presented urazole (the reduced form of TAD) as the terminal group and which were activated electrochemically without treatment with chemical oxidants, allowing on‐demand activation and in situ immobilization of the phenolic compounds. We examined the immobilization of various phenolic compounds and verified the surface chemistry using electrochemistry and mass spectrometry. The proposed method is simple and straightforward and does not require complicated protocols and reagents, and thus, it can be a general and practical platform for the immobilization of phenol‐containing molecules on the surfaces of various materials.

Special Issue “Coatings Imparting Multifunctional Properties to Materials”

Coating the surface of various materials and products has been used for a long time for protection against corrosion and erosion, in order to increase the service life and productivity of equipment [...]

Effect of Laser Peening with a Microchip Laser on Fatigue Life in Butt-Welded High-Strength Steel

Laser peening introduces compressive residual stresses on the surfaces of various materials and is effective in enhancing fatigue strength. Using a small microchip laser, with energies of 5, 10, and 15 mJ, the authors applied laser peening to the base material of an HT780 high-strength steel, and confirmed compressive residual stresses in the near-surface layer. Laser peening with a pulse energy of 15 mJ was then applied to fatigue samples of an HT780 butt-welded joint. It was confirmed that laser peening with the microchip laser prolonged the fatigue life of the welded joint samples to the same level as in previous studies with a conventional laser.

Using Accelerometer Smartphone Sensor and Phyphyox for Friction Experiment in High School

Experiments related to friction in schools are mostly done by direct observation, and it becomes more difficult to determine the value of the coefficients of static and kinetic friction due to the low level of accuracy. This study aims to develop a friction coefficient practicum tool using the accelerometer sensor on a smartphone with the Phyphox application. The research was conducted using the 4D Thiagarajan method (Define, Design, Develop, Disseminate). This tool demonstrates experimental friction on an inclined plane with a variety of surface materials (aluminium, wood, glass, acrylic). The results recorded by Phyphox are spreadsheets of object acceleration data per unit time in x, y, and z coordinate graphs. The sliding plane frame is designed using an Arduino microcontroller which can make it easier for students to automatically form inclined plane angles. This tool has been tested by experts with an average score are 85.25% and has been tested on physics teachers with an average score of 82.5% in the good category. This friction coefficient practicum tool is feasible and can help students understand the concept of friction

Nitrogen-doped graphene on a curved nickel surface

Graphene growth and doping are well studied on flat surfaces of various materials. To further advance the technological implementation of graphene-based systems, fundamental studies need more appropriate model templates, whose surfaces would mimic substrates with non-trivial topography. Here, using electron and photoelectron diffraction and photoemission spectroscopy as well, we demonstrate how a curved tungsten crystal covered by a thin nickel film can properly be used as such platform, allowing the fabrication and comprehensive characterization of nitrogen-doped graphene. We show the way in which nitrogen impurities prefer to embed into the graphene matrix at different areas of the curved metallic surface with variable density of atomic steps. In particular, at atomically flat regions with a strong graphene-metal interaction, pyridinic configuration is the most abundant form of dopants, while graphitic nitrogen strongly dominates in places with a weak coupling of graphene to the substrate, i.e., in the vicinity of the surface irregularities. We recognize single crystals with curvilinear surfaces as versatile platforms for the studies of not only low-dimensional materials, but also molecular adsorption, chemical reactions and catalysis on surfaces with complex structure.

Investigation of the influence of the nature of surface deformation on coating adhesion

The effect of deformation of the surface of a supporting metal element on the adhesion of a thin polymer film has been studied by an experimental-theoretical method. A setup has been developed that allows testing of adhesive coatings at various deformations of the substrate surface of various materials. The adhesion properties of a polymer film to a metal substrate have been determined. An explanation of the results obtained is given.

Extension and validation of a revised Cassie-Baxter model for tailor-made surface topography design and controlled wettability

Predicting wettability accurately across various materials, surface topographies and wetting liquids is undeniably of paramount importance as it sets the foundations for technological developments related to improved life quality, energy saving and economization of resources, thereby reducing the environmental impact for recycling and reuse. In this work, we extend and validate our recently published wetting model, constituting a refinement of the original Cassie-Baxter model after consideration of realistic curved liquid-air interfaces. Our model enabled more meaningful contact angle predictions, while it captured the experimentally observed trends between contact angle and surface roughness. Here, the formalism of our wetting model is further extended to 3D surface topographies, whereas the validity of our model, in its entirety, is evaluated. To this end, a total of thirty-two experimentally engineered surfaces of various materials exhibiting single- and multilevel hierarchical topographies of increasing complexity were utilized. Our model predictions were consistently in remarkable agreement with experimental data (deviations of 3%–6%) and, in most cases, within statistical inaccuracies of the experimental measurements. Direct comparison between experiments and modeling results corroborated that surface topographies featuring re-entrant geometries promoted enhanced liquid-repellency, whereas hierarchical multilevel surface topographies enabled even more pronounced nonwetting behaviors. For the sinusoidal topography, consideration of a second superimposing topography level almost doubled the observed water contact angles, whereas addition of a third level brought about an extra 12.5% increase in water contact angle.