Morphology Of Coatings Research Articles

Damage regularity and multifractal analysis of sol-gel reflection coating of KDP crystal under low UV irradiation flux.

This study employed multifractal analysis to investigate the changes in surface morphology of SiO2 anti-reflective coatings prepared on KDP substrates using the sol-gel method, under various conditions of ultraviolet (UV) irradiance. The coatings were successfully fabricated, and the chemical structure of the SiO2 sol was comprehensively characterized using Solid-State Nuclear Magnetic Resonance (SSNMR) technology. Under low UV irradiance (4 J/cm2), repeated experiments revealed a crack-induced mechanism of surface fatigue damage. Utilizing Scanning Electron Microscopy (SEM), the study discovered the induction effect of initial crack defects in UV-damaged coatings and established a damage model. Furthermore, Atomic Force Microscopy (AFM) was used to acquire images of the coatings' surface morphology at different damage levels, which were analyzed using the multifractal spectrum f(α). This analysis confirmed the multifractal nature of the coatings both before and after damage. This study identified significant effects of UV irradiation on the width of the multifractal spectrum and Δf, indicating that the SiO2 anti-reflective coatings exhibit multifractal characteristics under various damage states. The coatings displayed a pattern of decreasing and then increasing singularity spectrum width, height distribution unevenness, and surface roughness with increasing damage. This study demonstrates that multifractal analysis is an effective tool for describing the complexity of the surface morphology of sol-gel-derived anti-reflective coatings for the first time and for validating their multifractal properties across different stages of UV damage. HIGHLIGHTS: Damage dynamic process of KDP crystal sol-gel coating was described by SEM&AFM; The crack propagation mechanism of sol-gel coating under UV radiation is proposed; The damage evolution of sol-gel coating was described by multifractal analysis.

Enhanced Surface Mechanical and Tribological Properties of H13 Die Steel with TiAlSiN Coating Deposited by HiPIMS

TiAlSiN is a potential protection coating for die steel to improve the surface hardness, anti-wear performance and suitability. In the present study, TiAlSiN is deposited on H13 die steel by high power impulse magnetron sputtering and the effects of bias voltage, deposition temperature, and film thickness on the performance of coatings are studied. The microstructure, mechanical and tribological properties of coatings are analyzed by energy dispersive spectrometer, X-ray diffraction, nanoindentation, friction and wear tests. The results show that with the changes of sputtering parameters, the content of Ti, Al, Si, and N fluctuates slightly. With the increase of bias voltage, deposition temperature and film thickness, the diffraction peaks of Ti3Al2N2 phase become wider. Higher bias voltage, deposition temperature, and film thickness are beneficial for obtaining coatings with high hardness, and strong wear resistance. By observing the surface morphology of coatings after grinding with Si3N4 balls, it was found that the wear mechanism of coatings contains abrasive wear, fatigue wear, and oxidative wear.

Evaluation of the In Vitro Behavior of Electrochemically Deposited Plate-like Crystal Hydroxyapatite Coatings.

The purpose of coatings is to protect or enhance the functionality of the substrate material, irrespective of the field in which the material was designed. The use of coatings in medicine is rapidly expanding with the objective of enhancing the osseointegration ability of metallic materials such as titanium. The aim of this study was to obtain biomimetic hydroxyapatite (HAp)-based coatings on titanium by using the pulsed galvanostatic method. The morphology of the HAp-based coatings revealed the presence of very thin and wide plate-like crystals, grown perpendicular to the Ti substrate, while the chemical composition highlighted a Ca/P ratio of 1.66, which is close to that of stoichiometric HAp (1.67). The main phases and chemical bonds identified confirmed the presence of the HAp phase in the developed coatings. A roughness of 228 nm and a contact angle of approx. 17° were obtained for the HAp coatings, highlighting a hydrophilic character. In terms of biomineralization and electrochemical behavior, it was shown that the HAp coatings have significantly enhanced the titanium properties. Finally, the in vitro cell tests carried out with human mesenchymal stem cells showed that the Ti samples coated with HAp have increased cell viability, extracellular matrix, and Ca intracellular deposition when compared with the uncoated Ti, indicating the beneficial effect.

The role of FexCu(1‒x) electrodeposits from a deep eutectic solvent in promoting the hydrogen evolution reaction

Hydrogen from water splitting is more powerful, clean, and more energy-efficient than fossil fuels. Since the electrode material influences the performance and operating cost of industrial electrolyzers, this work induces technological innovation through FexCu(1−x) alloys with electrocatalytic action toward the hydrogen evolution reaction (HER). The materials were galvanostatically deposited on 1020 carbon steel. It was used electrolytes formulated with deep eutectic solvents (DES) and aqueous solvents (AQS) were used to verify their influence on the coatings' composition, morphology, and electrocatalytic activity. The results proved that even after fixing the operating conditions (electrochemical potential, current density, and deposition time), the alloys produced in DES are richer in Fe (≅ 77-85%, w/w). For comparison, those obtained from AQS have greater proportion of Cu (≅ 65%, w/w). Stoichiometry changes also alter the topography, surface area, and electrocatalytic activity of FexCu(1−x) alloys for hydrogen production. The electrochemical studies carried out also revealed that the association between Fe and Cu as alloying elements has a positive synergistic effect of reducing the HER overpotential by around 125 mV, using 1 mol L−1 KOH at 296 K. Considering stability and resistance to corrosion, FexCu(1−x) alloys produced in DES stood out as the most promising for possible adaptation in electrolyzers developed for large-scale hydrogen production.

Camouflage or Coincidence? Investigating the Effects of Spatial and Temporal Environmental Features on Feral Cat Morphology in Tasmania.

Variations in coat morphology are well documented among felids and are theorised to aid in camouflage during stalk and ambush hunting. A diverse array of coat types has arisen in Felis catus (feral cats) through domestication and subsequent selective breeding. This species has successfully spread across Australia over the past 200 years, raising the question of whether any specific coat types offer an adaptive advantage. We used 24,657 camera-trap images of feral cats in Tasmania, Australia, and assigned each cat observation a coat colour and pattern. We analysed these data to examine how different spatial features affect the modal coat type present at a site. We also tested if cats with differing coat types were active on different days in response to temporal features, including moon luminosity (full or new). Elevation was positively associated with the presence of orange (odds ratio = 2.5, 97.5% confidence interval = 1.5, 4.4) and tortoiseshell (odds ratio = 4.1, CI = 1.6, 10.5) cats, while blotched brown cats were negatively associated with elevation (odds ratio = 0.64, CI = 0.5, 0.9), relative to black cats. Brown mackerel cats were more common in eucalypt and rainforests (odds ratio = 1.9, CI = 1.1, 3.3), as well as sites with a higher FPAR (odds ratio = 1.3, CI = 1.1, 1.6). All coat types were 1.2-2 times more likely to be active on nights with a new moon, except for orange cats who were equally active regardless of moon luminosity (odds ratio = 0.94, CI = 0.62, 1.42). Our results indicate that coat types are equally successful across Tasmania, perhaps owing to naïve prey or limited predator competition. The high activity of orange cats irrespective of moon phase may be reflective of the male cat's tendency to patrol territory, as opposed to favouring dark nights for hunting. Future studies should consider comparing the coat types found in feral cats to adjacent domestic populations, and against a wider array of habitat types to further investigate the potential for selective pressure on feral cat coat types in Australia.

Zn-phosphate conversion coatings developed on high-strength steels at reduced processing temperature

The effect of process time, ultrasonic stirring, and the addition of H2PO4- on the morphology and corrosion resistance of phosphate conversion coatings was investigated by Scanning Electron Microscopy and electrochemical tests. The phosphating treatments were performed at 50 °C, lower than traditional processes, and pH 2.9 and 2.4. An enhanced film of bigger mass and reduced corrosion rate was produced when the processing time was extended from 6 to 30 min. at pH 2.9. No important changes were identified in the appearance other than a slight crystal coarsening and Zn enrichment. Both the ultrasonic stirring and the addition of H2PO4- (pH 2.9, 6 min.) accelerate the coating formation rate and assist in the formation of more uniform layers with a greater Zn concentration. An important crystal refinement was also obtained in the ultrasound-induced treatment, whereas no relevant changes were found for the corrosion behaviour. The addition of H2PO4- in the amount of 10 g/L (pH 2.9, 6 min.) facilitates the formation of a layer with a quality like that found in the longest treatment (30 min.). None of the tested variables provided an effective modification to improve the performance of the conversion layers developed for the baths considered in this study at pH 2.4.

Boronize Coatings Studied with a New Mass Transfer Model.

This study examined the development of Fe2B (diiron boronize) coatings on the surface of 35NiCrMo4 steel through the thermochemical surface hardening process called boronizing. The morphology and thickness of the boronize coatings were assessed using Scanning Electron Microscopy (SEM) and optical microscopy (OM). A novel mathematical mass transfer model was developed to estimate the diffusion coefficients of boron in hard coating. The presence of uniformly distributed boronize coatings with a typical sawtooth pattern on the surface of the substrate was confirmed. The boronize coating's chemical composition and phase constituents were analyzed utilizing X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The study confirmed the presence of a single-phase boronize coating (Fe2B). Furthermore, microhardness tests indicated that the boronized specimen's surface demonstrated an average hardness of approximately 1953 HV. The wear study were conducted using the pin-on-disk method under dry debonding conditions at room temperature to estimate the coefficient of friction (COF) of the boronized (average ≈ 0.35) and untreated (0.725) specimens. The results revealed approximately 200% improvement in wear resistance due to the boronized coating. The empirical validation of the mathematical model was carried out for two additional boronizing conditions at 1223 K for 3 h and 1273 K for 1.5 h, resulting in an estimated percentage error of around 2.5% for both conditions. Additionally, an ANOVA analysis was performed, taking into account the temperature and time factors. The findings indicate that both factors exert a substantial influence on the dependent variable (u), with temperature (T) contributing 64.68%, time (t) contributing 27.37%, and the interaction of both factors (T × t) contributing 5.13%.

Preparation and Formation Mechanism of β-SiC Coatings Using a SiCl4-CH4-H2-N2 System.

The mechanism of β-SiC preparation via chemical vapor deposition (CVD) of the SiCl4-CH4-H2-N2 system remains unclear. Consequently, the change of molar Gibbs free energy of the CVD β-SiC chemical reaction in the SiCl4-CH4-H2-N2 system has been studied by the Helsinki Software Corporation (HSC) Chemistry code for the first time. The role of nitrogen in the reaction was confirmed. Seven potential reaction pathways of CVD β-SiC were presented, and the thermodynamic equilibrium components of each reaction were calculated systematically. The most viable reaction pathway and corresponding optimal temperature range for CVD β-SiC were determined. In addition, a kinetic study of CVD β-SiC was conducted. The microscopic morphology and crystal structure of β-SiC coatings prepared on the graphite surface at different temperatures were charactered by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, etc. Ultimately, through SEM, XRD, and Raman observation, uniform and dense β-SiC coatings with fine grains and high crystallinity were successfully obtained. Furthermore, large β-SiC-coated graphite trays with diameters of 230 and 465 mm were prepared by CVD using the SiCl4-CH4-H2-N2 system, and the average thickness of β-SiC was about 100.6 μm. This study provides a theoretical basis and technical recommendations for the fabrication of SiC-coated graphite trays used in metal-organic chemical vapor deposition (MOCVD) equipment.

Influences of Sr(OH)2 on the Structure and Corrosion Resistance of Micro‐Arc Oxidation Coatings Formed on TC4 Titanium Alloy

ABSTRACTIn order to improve the comprehensive properties of TC4 titanium alloy, micro‐arc oxidation (MAO) coating is prepared on the surface of a TC4 substrate in a basic electrolyte with varying concentrations of Sr(OH)2. The surface morphology, phase composition, element distribution, and corrosion resistance of MAO coatings are analyzed by scanning electron microscopy, X‐ray diffraction, an energy‐dispersive spectrometer, the electrochemical test, and the erosion–corrosion test. The results show that the voltage of the MAO process increases and then decreases; the surface morphology and density of the coatings are greatly improved after doping Sr(OH)2. When the concentration of Sr(OH)2 is 0.6 g L−1, the thickness, hardness, and adhesion strength of the coating reach the maximum values of 37.04 μm, 836.2 HV, and 21.8 N, respectively. At this time, the wear resistance and corrosion resistance are the best, and the friction coefficient and the corrosion rate are the lowest: 0.3352 and 1.04 × 10−10 mm a−1, respectively.

Effect of adding Sr(OH)2 on the formation process of 2024 aluminum alloy micro-arc oxidation coatings

Micro-arc oxidation coatings with oxidation times of 15 S, 30 S, 60 S, 120 S, 240 S and 1800 S were prepared on 2024 aluminum alloy using silicate-phosphate electrolytes containing 0 g/L and 0.5 g/L Sr(OH)2, respectively. The effects of adding Sr(OH)2 on the oxidation voltage, surface morphology and phase composition of the 2024 aluminum alloy MAO coatings formation process were investigated using SEM, XRD and XPS. The results show that adding Sr(OH)2 increases and then decreases the oxidation voltage compared with that of the unadded Sr(OH)2, which has little effect on the morphology of the oxide coatings, the Sr2+ and PO43- in the solution are jointly involved in the formation of the MAO coatings. The main phase composition of the coating is γ-Al2O3, and the Sr element is uniformly distributed as SrCO3 in the coating.

Spraying Power Effect on Micro-Structure and Mechanical Property of TaSi2 Coating Prepared by Supersonic Air Plasma Spraying for SiC-Coated C/C Composites

In order to further improve the oxidation resistance of SiC-coated C/C composites used in extreme environments, TaSi2 coatings were deposited on the surfaces of SiC-coated C/C composites by supersonic air plasma spraying (SAPS) with different spraying power parameters, under other fixed parameter (gas flow, power feed rate, spraying distance and nozzle diameter) conditions. The micro-structures and phase characteristics of the TaSi2 coatings prepared with the four kinds of spraying powers (40 kW, 45 kW, 50 kW and 55 kW) were analyzed. Also, the inter-facial bonding strengths and fracture modes between the four TaSi2 coatings and the SiC coating were studied. The results showed that with an increase in the spraying power, the morphologies of the TaSi2 coatings appeared from loose to dense to loose. When the spraying power was 50 kW, the deposition rate reached a maximum of 39.8%. The TaSi2 coating presented an excellent micro-structure without obvious pores and microcracks, and its inter-facial bonding strength was 15.3 ± 2.3 N. Meanwhile, the fracture surface of the sample exhibited a brittle characteristic.

Effect of HA ratio on the morphology and characteristics of Ti-HA composite coatings on Ti6Al4V-ELI synthesized via mechanical milling

Effect of HA ratio on the morphology and characteristics of Ti-HA composite coatings on Ti6Al4V-ELI synthesized via mechanical milling

Multiscale textured solar absorber coatings for next-generation concentrating solar power

A high-temperature stable solar absorber is crucial for next-generation (Gen3) concentrating solar power (CSP) plants, to enable high temperature operation, maximize power generation efficiency, and thereby reduce the levelized cost of energy. This study presents novel, fractal-textured solar absorber coatings whose multiscale feature scales effectively match the visible region of the solar spectrum, leading to superb absorptive properties. Single and bimetallic oxide coatings of copper, cobalt and manganese were prepared on Inconel 625 substrates using electrodeposition. The effect of electrodeposition parameters and annealing temperature are systematically studied to optimize the morphology and properties of the oxide coatings. Multiscale textured bimetallic coatings of copper manganese oxide and copper cobalt oxide demonstrate a superior absorptance of 0.985, a remarkably low emittance <0.45 and an exceptional optical efficiency of ∼96 % under Gen3 CSP operating conditions, surpassing previously reported values in the literature by about 5 %. Durability tests confirmed the coatings’ steadfast endurance of mechanical and environmental stress, making them suitable for long-term application in harsh CSP environments.

STRUCTURE FORMATION OF Ni−P ALLOY ELECTROCOATINGS WITH INCREASED CORROSION RESISTANCE

Purpose of research. The main factors that reduce the protective properties of electrocrystallized coatings are the formation of volumetric defects − pores, as well as the occurrence of microgalvanic couples at grain boundaries, that is, on surface defects of the crystalline structure. Creating a non-porous structure in electrocoatings, eliminating the formation of surface defects in metal/alloy layers, as well as the possibility of replacing chromium coatings, which are obtained from toxic electrolytes, are urgent tasks. Materials and methodology. In the work, it was proposed to use electrocoatings with Ni−P alloy as protective layers on products that increase corrosion resistance. An X-ray determination of the phase composition of Ni−P electrochemical deposits was carried out. The surface morphology and corrosion resistance of coatings were studied. Results. Samples of electrochemical coatings of pure nickel and nickel-phosphorus alloy were studied. It has been established that during the formation of nickel coatings with the addition of phosphorus ions, the surface morphology has practically no pores, amorphization of deposits occurs, due to which the protective properties, namely, corrosion resistance, are improved. Scientific novelty. Factors have been identified that influence the increase in corrosion resistance of coatings − the absence of a porous structure and the formation of an amorphous state. Conclusions. The influence on the structure and properties of electrochemical coatings of a nickel-phosphorus alloy has been studied. It has been established that the addition of phosphorus ions to the nickel plating electrolyte leads to the formation of an amorphous structure in the coatings, and layers of the Ni−P alloy appear practically without the presence of pores. It has been established that the effect of increasing the corrosion resistance of the electrochemical coating with a nickel-phosphorus alloy (by 30 %) is due to the formation of an amorphous structure of the solidifying metal liquid while preventing the crystallization process during electrochemical deposition.

Influence of TiO2 Alloying Percentage on the Morphology of APS-deposited Coatings from Cr2O3 Powders

Influence of TiO2 Alloying Percentage on the Morphology of APS-deposited Coatings from Cr2O3 Powders

Microstructure and corrosion-resisting properties of CeO2-SiO2-Al2O3 composite coatings prepared by plasma electrolytic oxidation on aluminum matrix composites

CeO2-SiO2-Al2O3 composite coatings were prepared on aluminum matrix composites by plasma electrolytic oxidation in the electrolyte of a silicate system consisting of Na2SiO3 and NaOH. The effects of the content of the soluble salt additive Ce(NO3)3·6 H2O on the microstructure, elemental composition, phase structure, thickness, corrosion resistance, and resistance to high-temperature oxidation of the PEO coatings were systematically investigated. The results showed that the CeO2-SiO2-Al2O3 ternary composite ceramic coatings were prepared with the main components of the physical phases as α-Al2O3, γ-Al2O3, Al, and SiC. And the addition of Ce(NO3)3·6 H2O increased the thickness of the coatings from 14.75 μm to 82.71 μm. Meanwhile, densification showed a tendency to increase and then decrease with the concentration of Ce(NO3)3·6 H2O. The surface microscopic morphology of the PEO coatings was optimized with the increase of the added concentration when the Ce(NO3)3·6 H2O concentration was lower than 1.0 g/L, and the surface quality of the coatings deteriorated when the Ce(NO3)3·6 H2O concentration was higher than 1.0 g/L. The corrosion resistance of the coatings was improved when the concentration of Ce(NO3)3·6 H2O was increased to 82.71 μm by the electrochemical experiments and the cavitation experiments. The corrosion resistance of the coatings was optimized when the concentration of Ce(NO3)3·6 H2O was added at 1.0 g/L, the coating’s corrosion resistance was optimized.

Characterization and electrodeposition mechanism of Ni–Mo coatings from self-regulating electrolyte

Electrochemical Ni–Mo coatings were obtained on a low-carbon steel substrate using a stable, environmentally safe, self-regulating electrolyte containing 0.2 M NiCl2, 0.3 M Na3C6H5O7, and SrMoO4 (saturated). The effects of electrolyte pH, temperature, deposition current density, and hydrodynamic conditions on chemical composition and morphology of the coatings were studied. It was established that the addition of ammonia to the electrolyte contributes to the deposition of a more uniform, globular, nonporous coatings morphology. The effect of ammonia on the formation mechanism of coatings was substantiated. The stages of deposition and the limiting stage of the formation of Ni–Mo coatings from citrate-ammonia electrolytes, which involves the chemical reduction of molybdenum oxide (IV) to molybdenum, were determined using cyclic voltammetry.

Study on Initial Corrosion Behavior of Arc-thermally Spray Zn, Zn–Al, and Al–Mg Coatings Exposed in Atmospheric Environment for One-Year

AbstractThis paper presents the results of a study comparing the initial corrosion characteristics of thermal spray coatings on Zn, Zn-Al, and Al–Mg thermal spray coatings after one year atmospheric exposure tests at two atmospheric environment sites. The thermal spray coatings were obtained by electroric arc spraying of various metals onto a carbon steel substrate. Atmospheric exposure tests were also conducted for outdoor accelerated exposure tests in which test specimens were applied with artificial seawater. The corrosion properties of these spray coatings were evaluated by surface analysis, film thickness measurements, cross-sectional analysis and anodic/cathodic polarization measurement. After one year of atmospheric exposure testing, white, granular corrosion products were observed on the surface of the Zn and Zn-Al thermal spray coatings, while no significant changes were observed in the Al–Mg thermal spray coating. Similar results were obtained for the surfaces of test specimens in atmospheric exposure tests with artificial seawater. The thickness of the thermal spray coating increased for the Zn thermal spray coating, while no significant change was observed for the other thermal spray coatings. Thus, differences in corrosion behavior were observed due to the composition of the thermal spray coatings. The initial corrosion behavior of the thermal spray coatings was also investigated based on the results of coating morphology and cross-sectional elemental distribution of the coatings.

Study of the Synergistic Influence of Plasma Electrolytic Oxidation and Wet Post-Treatment on the Surface of AA7075.

In this study, we enhanced the corrosion and microbial resistance of aluminum 7075 alloys by applying a thin layer of alumina through plasma electrolytic oxidation (PEO) in an alkali-silicate electrolyte. In addition, the influence of film sealing on coated aluminum alloy 7075 was studied in detail, specifically in oil and water at 100 °C after treatment. The surface and cross-sectional morphology, element composition, and phase composition of the PEO coatings were characterized by using scanning electron microscopy (SEM) assisted with energy-dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD), respectively. The corrosion resistance of the coating on AA7075 PEO was evaluated before and after post-treatment using hot water and hump oil at 100 °C. This assessment was conducted by using various electrochemical techniques, including open-circuit potential (OCP), linear polarization resistance (LPR), potentiodynamic polarization scan (PD), electrochemical impedance spectroscopy (EIS), and cyclic potentiodynamic scan (CPS). The results showed that the corrosion resistance of the AA7075 alloy was significantly improved after the PEO coating. The AA7075 + SF, among all of the examined alloys, exhibited superior corrosion properties, due to its fat sealing. This is probably due to the formation of a mixed fatty acid layer from oil on the surface of the AA7075 PEO, which synthesizes a hydrophobic layer. Interestingly, the samples treated with PEO showed a great resistance to microbial growth.

Response of variation of electrical control parameters to coatings prepared in organo-silicon electrolyte by plasma electrolytic oxidation

This study aims to explore the influence of control parameters from the perspective of the amorphous ceramic coating formation process. Three preparation processes were preferred based on the thickness, appearance and corrosion resistance of the coatings by orthogonal experiment. The surface morphology, cross-sectional structure, phase composition and micro-hardness of PEO coatings were examined using scanning electron microscopy (SEM)/Energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and hardness measurement techniques. Findings indicate that voltage exerts the most significant impact on coating thickness and appearance, whereas the influence of other parameters becomes more pronounced as the voltage increases. Three amorphous ceramic coatings prepared in 20 min with thicknesses of 27.4 μm, 83.2 μm and 193.3 μm increased the surface hardness of 6061 aluminium alloy by 6–8 times, and decreased the corrosion current density of 6061 aluminium alloy by 3 orders of magnitude in 1 mol L−1 HCl solution. Moreover, the thickening of the coating primarily occurs within a few minutes after the voltage reaches its peak, and high frequency and low duty ratio are prerequisites for better appearance under higher voltage conditions.