Surface Morphology Of Coatings Research Articles

Integrated processing of Al2O3/ZrO2 eutectic implants with bioactive Ca-P coatings by laser cladding

Al2O3/ZrO2 composites are currently popular for orthopaedic and dental restorations. However, the long-term reliability of Al2O3/ZrO2 implants should be further improved by reducing the aging sensitivity and enhancing the osteointegration performance. In this paper, melt-grown Al2O3/ZrO2 eutectics with bioactive Ca-P coatings are successfully prepared by successive laser cladding technique. The processing strategy is studied to show that the laser power has a significant influence on the phase constituent, surface morphology and mechanical properties of Ca-P coatings. The aggravated elements interdiffusion and strong metallurgical bonding between coating and substrate is found with increased laser power from 50 W to 70 W under the same laser energy density, which leads to reduced bioactivity and enhanced adhesion strength of Ca-P coating (3.5 ± 1.1 N to 14.9 ± 1.4 N). The bioactivity of Al2O3/ZrO2 eutectics is greatly improved by the coating of highest content of 55.9% Ca-P phase under the optimized parameters with laser power of 50 W and scanning rate of 50 mm/s. A thick bone-like apatite layer with Ca/P of 1.71 similar to that of bone can be observed on the coating surface after soaking tests. Thus, laser cladding is a potential and efficient strategy to modify Al2O3/ZrO2 eutectics with desired biological properties, which may be applied as load-bearing implants for clinical application.

Research on wettability of nickel coating changes induced in the electrodeposition process

• The sample-based stochastic convergence analysis were adopted to estimate the uncertainty. • Appling CCD method to design electrodeposition experiment selected five main electrodeposition parameters as variables. • Surrogate coupling models was established based on experimental results. • The concentration of ion and brightener have significant effects on the wettability of the coating. In this study, nickel coatings were electrodeposited on copper substrate. The effect of electrodeposition process parameters on surface morphology and wettability of nickel coatings were studied, such as ions source, anode activator, pH buffer, brightener and current density. According to the experiment plan established by Central Composite Design (CCD) with five parameters as mentioned above, nickel coatings have been fabricated on the copper sample using one-step electrodeposition method. Then, response surface methodology was utilized to establish surrogate models based on the static contact angle of nickel coatings which were measured by water liquids. 3D digital microscope, scanning electron microscope (SEM) and energy dispersive X-Ray spectroscopy (EDS) showed rough hierarchical structure, surface morphology and chemical composition on the coating surface, respectively. Subsequently, a sampling-based stochastic model was devoted to weigh the effects of uncertainty in each electrodeposition process parameter on the variability of water contact angle. According to the obtained results, the concentration of brightener as well as ions source greatly affects the wettability of nickel coating. The method of uncertainty analysis can be applied to study the uncertain influence factors in electrochemistry research.

Fabrication and characterization of Ni–Fe–P–TiO2 nanocomposite coatings

This study develops the Ni–Fe–P–TiO2 nanocomposite coatings via an electroless deposition process. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine the coating structures. Hardness and wear tests were conducted to measure the coating’s mechanical performance, and polarization curves were recorded to evaluate the corrosion behavior. The results show that the TiO2 nanoparticles are incorporated into the coatings. The proper addition of TiO2 refines the coating surface morphology without changing the coating phase constituents. The best mechanical and corrosion performance is obtained for the 0.5-g/L modified Ni–Fe–P–TiO2 sample, owing to its compact surface feature and well-dispersed TiO2 nanoparticles.

Preparation and characterization of silk fibroin/silica thermal insulation coatings on catheters

Clinical practice of therapeutic hypothermia for neuroprotection in acute cerebral ischemia has been hindered by the warming effect on the cold infusate along the pathway, which results from the poor thermal resistance of the traditional interventional catheter. In this study, thermal insulation coatings with different spray parameters and coating suspension compositions were prepared by air-spraying on a nylon substrate for biomedical application. The surface morphology and microstructure of coatings were investigated by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. Silk fibroin (SF) and hollow silica-based nanospheres (HSBNSs) were successfully sprayed on the nylon substrate. The thermal conductivity of the coating measured by a light flash apparatus was down to 0.00105 W/(m K). The tape test indicated that the coatings containing SF, HSBNSs and glyceryl had good adhesion, showing that air-spraying is a promising method to enhance the thermal insulation performance of traditional catheters for cerebral hypothermia therapy.

Microstructural Properties and Wear Resistance of Fe-Cr-Co-Ni-Mo-Based High Entropy Alloy Coatings Deposited with Different Coating Techniques

Materials can be subjected to severe wear and corrosion due to high temperature, high pressure and mechanical loads when used in components for the production of geothermal power. In an effort to increase the lifetime of these components and thus decrease cost due to maintenance High-Entropy Alloy Coatings (HEACs) were developed with different coating techniques for anti-wear properties. The microstructure, mechanical and tribological properties of CoCrFeNiMox (at% x = 20, 27) HEACs deposited by three different technologies—high-velocity oxygen fuel (HVOF), laser cladding (LC) and electro-spark deposition (ESD)—are presented in this study. The relationship between surface morphology and microstructural properties of the as-deposited coatings and their friction and wear behavior is assessed to evaluate their candidacy as coatings for the geothermal environment. The wear rates were lower for the HVOF coatings compared to LC and ESD-produced coatings. Similarly, a higher hardness (445 ± 51 HV) was observed for the HVOF HEACs. The mixed FCC, BCC structure and the extent of σ + µ nano precipitates are considered responsible for the increased hardness and improved tribological performance of the HEACs. The findings from the study are valuable for the development of wear-resistant HEAC for geothermal energy industry applications where high wear is encountered.

The influence of substrate bias on the surface morphology, microstructure and mechanical behaviour of TiNiN coatings

The application of a negative substrate bias during physical vapor deposition can have important effects on the surface morphology, structure and properties of ceramic-based coatings. In this study, a number of TiNiN coatings were prepared onto AISI M2 steel substrates via cathodic arc deposition method by employing a range of different negative substrate bias voltages. The objective of this work is to study the influence of bias voltage on the surface morphology, microstructure and mechanical characteristics of these thin films. A change from a fine columnar grained structure to highly refined equiaxed grains was noted with increasing bias from 0 to −50 V, associated with the energetic ion bombardment at the higher substrate bias. A very high hardness value of ∼ 34.2 GPa was attained at a −100 V substrate bias, which was attributed to the synergistic effects of a number of factors such as the presence of compressive residual stresses, solid solution hardening effects along with grain refinement. In addition, significant reduction in the density of microparticle-related defects generated in these coatings was achieved at ≥ -100 V, which can presumably be ascribed to the higher repulsive force induced at higher substrate bias values.

ZrO2/ZnO/TiO2 Nanocomposite Coatings on Stainless Steel for Improved Corrosion Resistance, Biocompatibility, and Antimicrobial Activity.

The ultrathin nanocomposite coatings made of zirconium oxide (ZrO2), zinc oxide (ZnO), and titanium oxide (TiO2) on stainless steel (SS) were prepared by the radio frequency sputtering method, and the effects of the nanocomposite coating on corrosion protection and antibacterial activities of nanocomposite coated SS were investigated. Scanning electron microscopy was conducted to observe surface morphology of nanocomposite coatings with distinct distribution of grains with the formation on SS substrate. From the electrochemical impedance spectroscopy results, ZrO2/ZnO/TiO2 nanocomposite coating showed excellent corrosion protection performance at 37 °C during immersion in simulated body fluid and saliva solution for 12 and 4 weeks, respectively. The impedance of ZrO2/ZnO/TiO2 (40/10/50) nanocomposite coated SS exhibited values about 5 orders of magnitude higher than that of uncoated SS with polarization at the low-frequency region. Cell viability of ZrO2/ZnO/TiO2 nanocomposite coated SS was examined under mouse fibroblasts culture (L929), and it was observed that the nanocomposite coating improves proliferation through effective cellular attachment compared to uncoated SS. From the antimicrobial activity results, ZrO2/ZnO/TiO2 nanocomposite-coated SS showed killing efficiency of 81.2% and 72.4% against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, respectively.

Quantitative analysis of the pigment coating structure influenced by the spreading of latex binder: In situ analysis of correlations between different structural properties

The spreading and adhesion of latex binder in pigment coating layer plays a decisive role in the structure and properties of paper coating. However, some aspects of its influence are still controversial. This study deals with a comprehensive analysis of pigment coating structure prepared with different latex binders with varying levels of spreading. In situ analysis of different structural characteristics by cross-section SEM image analysis method revealed various correlations between the structural properties of coating layers. To vary the extents of latex spreading, coating layers were prepared with latexes of different glass transition temperatures and exposed to different drying and dry-sintering conditions. Quantitative analyses of the microscopic surface roughness, dimensional changes and pore structures were performed using cross-section image analysis. The resulting data was compared with the morphological characteristics of latex binder within the coating structure. Coating surface morphologies were found to be strongly correlated with the extent of latex spreading, while the thickness and porosity of coating layers did not show correlation with latex spreading. Pore size distributions were significantly different when the extent of spreading of latex binder was low, which showed high correlation with the change in adhesion behavior of binder to pigment particles. Pore shapes were strongly correlated with the extent of latex spreading.

Mathematical modelling of sound transmission loss (STL) in metallic and graphite based coatings

ABSTRACT This study aimed to investigate the relationship between the sound transmission loss (STL) properties and surface morphologies of metallic-based and graphite-based coatings. Aluminium (22 µm average particle size (APS) and 12 µm APS), copper (12 µm APS), silver (14 µm APS) as conductive metal pigments and graphite (18 µm APS) as a semi-conductive pigment were used to create coatings and STL properties were measured with an in-house designed sound wave modulation device. Laser beams with different carrier wavelengths were used in the experiment, for which the wavelength with the highest R2 and number of significant variables was used to create a mathematical model to help in measuring the sound transmission loss properties. Surface tension energy, conductivity, permeability, reflectivity, concentration and the type of pigment were found to be significant in determining the STL properties.

Effect of Au ion irradiation on the surface morphology, microstructure and mechanical properties of AlNbTiZr medium-entropy alloy coatings with various Al content for ATF

The AlNbTiZr medium-entropy alloy (MEA) coatings with different Al content were irradiated by 6 MeV Au-ions. The effect of the irradiation fluence on the surface morphology, microstructure and mechanical properties of the coatings with different Al content were investigated by SEM, XRD, TEM and nano-indenter. The results showed that the surface of coatings became flatter and smoother with increasing ion irradiation fluence. The crystal structure of all the coatings remained stable at lower fluence. However, the crystallization phenomena occurred at higher irradiation fluence and crystallization degree of the coatings decreased with increasing Al content, which the average crystal size was proportional to the irradiation damage level. The irradiation-induced crystallization changed the uniformity of element distribution, and element segregation phenomenon appeared in the Al-containing coating. The change of coatings hardness after irradiation is related to the amount of free volume content introduced by irradiation and the degree of crystallization. All of these results will help us to understand the response of the AlNbTiZr MEA coatings with different Al content under ion irradiation.

The Effect of Non-Thermal Atmospheric Pressure Plasma Treatment of Wheat Seeds on Germination Parameters and α-Amylase Enzyme Activity

This contribution presents the results of a study of the germination rate and growth parameters of wheat seeds after atmospheric pressure surface coplanar dielectric barrier discharge (DBD) plasma treatment. The germination rate and biometric parameters such as the root, shoot length, mass of the seedlings, and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> -amylase enzyme activity were studied at different plasma exposure time. The seed coat surface wettability and morphology were determined by apparent contact angle measurement and scanning electron microscope (SEM) analysis. Seed surface disinfection and the presence of filamentous fungi have also been investigated at different discharge parameters. It is shown that the optimal plasma treatment duration for increasing the growth parameters and enhancing the enzymatic activity is 5–15 s. It was found that the longer plasma exposure requires complete sterilization of the seed surface from pathogens, compared to the optimal treatment time for high germination. Based on the obtained results, the possible mechanisms of the positive effect of plasma treatment on the enhanced germination of wheat seeds are discussed.

Tuning mechanical and corrosion performance of SiOC glass coatings prepared by thermal MOCVD

In this study, silicon oxycarbide (SiOC) glass coatings were successfully deposited by thermal metal organic chemical vapor deposition (MOCVD). The composition, chemical bonding and mechanical properties of the prepared SiOC glass coatings were studied using X-ray photoelectron spectroscopy (XPS) and nano indentation techniques. The surface morphologies of SiOC coatings were characterized by field emission scanning electron microscopy (FESEM) before and after etching with HF acid for prolong time. The results showed that the percentage of Si-C bonds in SiOC glass coatings increases with increasing the content of HMDS in liquid precursors mixture. Raman spectroscopy results revealed the presence of amorphous carbon (with high content of sp3 bonds) in the prepared SiOC coatings. Consequently, the hardness and modulus of SiOC glass coatings increased from 8.99 GPa and 82.6 GPa to 17.93 GPa and 195.6 GPa, respectively. Further, the prepared SiOC glass coatings exhibited excellent corrosion resistance against HF acid.

Effect of Ni Concentration on the Surface Morphology and Corrosion Behavior of Zn-Ni Alloy Coatings

This research work aims to develop electrodeposited Zn-Ni alloy coatings with controlled dissolution tendencies on a mild steel substrate. The varying Ni concentration in the electroplating bath, i.e., 10, 15, 20 and 25 g·L−1, affected the surface morphology and electrochemical properties of the deposited Zn-Ni alloy coatings. SEM and EDS analysis revealed the resulting variation in surface morphology and composition. The electrochemical behavior of different coatings was evaluated by measuring the open circuit potential and cyclic polarization trends in 3.5 wt.% NaCl solution. The degradation behavior of the electrodeposited Zn-Ni coatings was estimated by conducting a salt spray test for 96 h. The addition of Ni in the coating influenced the coating thickness and surface morphology of the coatings. The coating thickness decreased from 38.2 ± 0.5 μm to 20.7 ± 0.5 μm with the increase in Ni concentration. Relatively negative corrosion potential (&lt;−1074 ± 10 mV) of the Zn-Ni alloy coatings compared to the steel substrate (−969 mV) indicated the sacrificial dissolution behavior of the Zn-rich coatings. On the other hand, compared to the pure Zn (26.12 mpy), ~4 times lower corrosion rate of the Zn-Ni coating (7.85 mpy) was observed by the addition of 25 g·L−1 Ni+2 in the bath solution. These results highlighted that the dissolution rate of the sacrificial Zn-Ni alloy coatings can effectively be tuned by the addition of Ni in the alloy coating during the electrodeposition process.

TiO2 Nanocoatings with Controllable Crystal Type and Nanoscale Topography on Zirconia Implants to Accelerate Bone Formation.

In dentistry, zirconia implants have emerged as a promising alternative for replacing missing teeth due to their superior aesthetic performance and chemical stability. To improve the osseointegration of zirconia implants, modifying their surface with hierarchical micro/nanotopography and bioactive chemical composition are two effective ways. In this work, a microscale topography was prepared on a zirconia surface using hydrofluoric acid etching, and then a 50 nm TiO2 nanocoating was deposited via atomic layer deposition (ALD). Subsequently, an annealing treatment was used to transform the TiO2 from amorphous to anatase and simultaneously generate nanoscale topography. Various investigations into the coating surface morphology, topography, wettability, and chemical composition were carried out using scanning electron microscopy, white light interferometry, contact-angle measurement, X-ray diffraction, and X-ray photoelectron spectroscopy. In addition, in vitro cytocompatibility and osteogenic potential performance of the coatings were evaluated by human bone marrow mesenchymal stem cells (hBMSCs), and in vivo osseointegration performance was assessed in a rat femoral condyle model. Moreover, the possible mechanism was also investigated. The deposition of TiO2 film with/without annealing treatment did not alter the microscale roughness of the zirconia surface, whereas the nanotopography changed significantly after annealing. The in vitro studies revealed that the anatase TiO2 coating with regular wavelike nanostructure could promote the adhesion and proliferation of osteoblasts and further improve the osteogenic potential in vitro and osseointegration in vivo. These positive effects may be caused by nanoscale topography via the canonical Wnt/β-catenin pathway. The results suggest that using ALD in combination with annealing treatment to fabricate a nanotopographic TiO2 coating is a promising way to improve the osteogenic properties of zirconia implants.

Electrodeposition of Chitosan on Ti-6Al-4V Surfaces: A Study of Process Parameters

The effect of different electrodeposition variables of chitosan coatings on Ti-6Al-4V substrates is studied. Electrolytic solutions containing chitosan at 0.1, 0.5, and 1.0 wt/v% was used to coat Ti-6Al-4V grit-blasted samples through electrodeposition, at 1.5 and 3.0 V, for 2.5, 20 and 30 min. Coating surface morphology was analyzed by scanning electron microscopy. Adhesion behavior was characterized by scratch testing, and coating stability under physiological conditions was assessed by swelling test. Electrodeposited coatings with longer times and high chitosan concentrations produced porous coatings, with a hydrogel-like structure, with better surface adhesion than those at lower concentrations and times. Swelling tests displayed a high initial swelling with posterior rapid degradation and stabilization at 3h, indicating the potential need for a crosslinking agent. These results suggest that chitosan electrodeposition has great potential for coating applications of metallic implants, and further in vitro cell assays are proposed for future studies.

Anomalous codeposition of NiCo alloy coatings and their corrosion behaviour

Here, we report the electrodeposition NiCo alloy coatings from a new bath using the glycine, as additive. A bright and uniform coatings NiCo alloy have been developed at different current densities and their corrosion performances have been evaluated. The surface morphology, composition and phase structure of alloy coatings have been analyzed using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray diffraction (XRD) techniques, respectively. The compositional information of NiCo alloy coatings revealed that the proposed bath follows anomalous type of codeposition over range of current density studied (1.0–4.0 A dm−2), by demonstrating more Wt. % of Co in the deposits, than in the bath. A constant increase in the Wt. % of Ni with current density was found, supported by XRD analyses; and it may be attributed to the depletion of more readily depositable Co+2 ions at cathode film by following the principle of codeposition of NiCo alloy. The corrosion study revealed that NiCo alloy deposited at 4.0 A dm−2, represented as (NiCo) 4.0 A dm-2 coating is the most corrosion resistant compared to all other coatings. The highest corrosion stability of (NiCo) 4.0 A dm-2 alloy attributed to its highest Ni content (38.6 wt%) and increased surface smoothness, supported by EDS and SEM study.

Role of heat treatment on the friction and wear behavior of duplex electroless nickel deposits

In the present investigation, duplex electroless Ni-P/Ni-Cu-P and Ni-P/Ni–W-P coatings are deposited on mild steel specimens using the dual bath technique. Both the coatings are developed with Ni-P as the inner layer. The scanning electron microscope (SEM), X-ray diffraction techniques (XRD) and energy dispersive X-ray analysis (EDX) are used to characterize the duplex coatings at pre and post-heat treatment state. Heat treatment is carried out at a temperature range between 200 °C and 800 °C. The surface morphology of the as-deposited coatings is nodular. Grain growth and grain boundaries are clearly visible in heat treated coatings. The EDX of Ni-P/Ni-Cu-P and Ni-P/Ni–W-P coating showed the phosphorus content as 12% and 9% respectively indicating high-P deposits. The copper and tungsten content of the coatings are 10% and 3% respectively. XRD analysis of both the as-deposited coatings indicate amorphous phase while heat-treated ones have crystalline phase structure. The crystalline structure increases the hardness of coating along with its wear resistance. The friction and wear behavior are assessed by a pin on disc tribometer. Overall, it can be seen that Ni-P/Ni–W-P system performs better compared to Ni-P/Ni-Cu-P in terms of friction and wear. However, heat treatment at higher temperature has negative impact on both the coatings as far as the tribological behavior is concerned.

ВЗАИМОСВЯЗЬ ПАРАМЕТРОВ ЭЛЕКТРООСАЖДЕНИЯ И МОРФОЛОГИИ ПОВЕРХНОСТИ НИКЕЛЕВЫХ ПОКРЫТИЙ В ПРИСУТСТВИИ ИНГИБИТОРА РОСТА

On the one hand, nickel and nickel coatings are well-studied objects in terms of their wide practical application; on the other hand, the application of various approaches to their production and structuring gives new possibilities for changing their properties. At present, the research activities related to the change in nickel physicochemical properties through nanostructuring are being carried out. Methods and techniques for producing nanostructured materials are very diverse. However, many of them are considered energy-intensive and economically unviable. The work solves the problem of obtaining nickel coatings and changing their properties through electrodeposition from aqueous solutions of electrolytes. The paper studies the effect of additives to a nickel electrolyte on the habit of crystals formed in the coating and, consequently, the nickel coating morphology. The authors used sodium, potassium, and calcium chlorides in the same molar concentration to be additives. During the electrodeposition of coating samples, the substrate nature and the electrolysis regimes changed. The deposition was carried out in the stationary mode of electrodeposition within one or two stages of electrolysis. The authors studied the obtained samples by scanning electron microscopy methods using X-ray diffraction analysis. The study identified that chlorides can significantly change the coating surface morphology. Depending on chloride concentration and deposition regimes, the surface morphology of nickel coatings changes from the three-dimensional cone-shaped structures to the lamellar habit. Chlorides allow forming crystals with pentagonal symmetry as well. The addition of chlorides affects the growth of crystals in certain crystallographic directions (111), which may be the result of their inhibitory effect. The obtained nickel coatings have a regular microrelief.

Evaluation of sliding wear, oxidation, and corrosion behaviour sustainable hybrid composite coating

Antifriction eco-friendly coatings are in massive demand into the automobile sectors for piston ring applications in the present scenario. In the current research work, HVOF sprayed composite coatings were developed to fulfil the manufacturer's need. The developed coating surface morphology was studied using SEM, EDS, corrosion tester, and oxidation test at high temperature. Pebbles like shapes were also visible in obtained images with the changing size of 10–100-µm. As the resolution has increased to 1500X and 2.50KX, a flake type of microstructure is visible beside the broken flakes at the time of milling operations. Carbon based coating has been applied consistently uniform and homogeneously. The developed coating was tested at evaluated temperatures of 50, 150, 250 and 350 °C, to study the behavior of micro-hardness and sliding wear resistance on the developed coatings by using hardness measuring tester and pin-on-disk tribometer. The obtained experimental results showed a significant increase in the value of hardness, lower COF and sliding wear at the temperature of 350 °C. The micro-hardness was found be 470HV whereas COF and sliding wear was about 0.07 and 45 µm respectively. The mass loss of deposited coating was 75% decreased (mass loss per area) at 2 hr of exposed time, 65% decreased at 4 h, and 58.53% at 6 h. The conducted results show the mass gain on the deposited coatings at the exposed testing time of 2 h was 56.0.25%, 75% at 4 h, and 54.83% at 6 h.

Evaluation of as deposit HVOF coating for corrosion and sliding wear resistance

The entire world faces pollution allied problems due to the emission of harmful gases and pollution enabled manufacturing processes at various levels. That's why the demand for cost-effective and less polluting coatings is in colossal need to decrease carbon footprints, reduce pollution, save energy, and reduce friction among the mating parts. In the present work, the carbon mixed composite coatings were by using HVOF technology. The developed coating surface morphology was studied using SEM, EDS, corrosion tester, and pin on disc tribometer at high temperature. The tribological behaviour of developed coatings was tested and following results were obtained, value of COF changes from 0.15 to 0.58 during the experiment. In contrast, wear results varies from 55 to 140 µm in the considered tested condition. The coated and uncoated samples were dipped in solution for 6 h to study the corrosion behaviour of developed coating, where the candidate recorded, 0.22–0.06 g decrement in mass loss, when sample was dipped for 6 h due to the presence of protective coatings onto the sample of substrates. The experimental results shows decrease in mass loss about 72.7% at the time of corrosion test, while 74.13% and 60.7% of the decrease in COF and wear respectively at tested condition.