Uniform Coatings Research Articles

Electrochemically produced films based on individual porphyrins and bimetallic composites: Morphology and electrocatalytic properties in the reaction of oxygen electroreduction

In this work, we obtained polyporphyrin films based on Fe(III)Cl-5,10,15,20-tetrakis(4-pyridyl)porphyrin and Mn(III)acetate-5,10,15,20-tetrakis(4-pyridyl)porphyrin and composite films on their basis by electrooxidation-induced electrochemical polymerization. The obtained films produced uniform coatings. Spectral analysis showed that the composite films were enriched with iron complexes. Comparative analysis of the prepared films demonstrated differences between the morphologies of the composite film and films of individual metal complexes. The oxygen electroreduction process on the obtained materials proceeded at more positive values than that on carbositall. The effective number of transferred electrons demonstrated that replacing catalysts based on individual porphyrins with the bimetallic composite changed the process mechanism: while the four-electron mechanism competed with subsequent two-electron reactions on the Fe(III)Cl-5,10,15,20-tetrakis(4-pyridyl)porphyrin and Mn(III)acetate-5,10,15,20-tetrakis(4-pyridyl)porphyrin films, on the bimetallic composite the process mainly represented a four-electron reaction.

Precursor design and cascade mechanism of RuO2·xH2O atomic layer deposition

As the unique nanofabrication technique, atomic layer deposition (ALD) can be used to deposit high-quality, uniform, and conformal nanoparticle coatings. Ru and its oxides (RuOx) are important materials in the fields of microelectronics and catalysis. In this work, the reaction of Ru precursors with different ligands on the hydroxylated surfaces were explored. The elimination of the pyrrolyl (Py) ligand is easier than that of the cyclopentadienyl (Py) ligand on the hydroxylated surface. The reaction involved in RuO2·xH2O ALD using RuPy2 and H2O as precursors was further investigated. During the RuPy2 reaction, the pyrrolyl ligand is eliminated by the substitution reaction with a surface hydroxyl group. However, the desorption of the pyrrole molecule is difficult due to the strong adsorption between the pyrrole molecule and Ru surface. During the H2O reaction, the H2O molecules further help the elimination of pyrrolyl ligands from the surface and the dissociative desorption of pyrrole molecules This unique reaction mechanism involved in the ALD of RuO2 with the assistance of H2O can be termed new cascade mechanism. These findings provide theoretical guidance for precursor design and ALD growth of metal oxides.

Experimental investigation on the wear characteristics of TiC-Co composite coating deposited on AZ91D Mg alloy substrate by plasma transferred arc (PTA) welding process

Abstract In this investigation, a plasma transferred arc (PTA) cladding process was employed to deposit TiC-Co composite coatings on substrate of AZ91D magnesium (Mg) alloy. The morphology and phases of the recently produced composite coatings were examined using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The microhardness and wear rate were evaluated by Vickers microhardness tester and pin-on-disc wear and friction test apparatus at the room temperature respectively. The results demonstrate that dense, uniform, and crack free coatings, with good metallurgical bonding to the AZ91D Mg alloy substrate were formed. The most of the phases present in composite coatings were TiC, Mg, CoTi, α-Co, AlCo, Al3Ti, and Co3C. The maximum average micro-hardness of TiC-Co composite coating was found to be about 1743 HV, which depends on the PTA currents. Whereas, average micro-hardness of the AZ91D Mg alloy substrate was 65 HV. This indicates that the coated layer produced increase in hardness about 27 times of substrate hardness. The cladding layer exhibited a wear rate of 4.94×10-8 g/N-m, whereas the wear rate of the AZ91D Mg alloy substrate was 58×10-8 g/N-m. This indicates that the wear resistance of cladding layer was 12 times higher as compared to AZ91D Mg alloy substrate. The enhanced micro-hardness and wear resistance of TiC-Co composite coating can be attributed due to the formation of ceramic and intermetallic compounds, unveiling its superiority over the AZ91D substrate.

Everolimus-encapsulation in Pluronic P123 self-assembled micelles as drug delivery systems for drug-coated balloons

Drug-coated balloons (DCBs) are effective tools for cardiovascular interventions, ensuring uniform drug delivery to occluded arteries. This research investigates the potential of Pluronic P123 (P123), a micelle-forming polymer, to solubilize and release Everolimus (EVE) from DCBs. Furthermore, it seeks to understand how the ratio of P123 to EVE affects release rates and micelle formation under physiological conditions. We tested three P123 to EVE ratios: 90:10, 75:25, and 50:50. Microscopy revealed that increasing EVE proportions resulted in more uniform coatings. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed the successful incorporation of EVE into the P123 matrix without altering its chemical properties. Differential scanning calorimetry (DSC) studies showed that EVE incorporation affected the crystalline structure of P123, leading to more uniform coatings. In vitro release studies showed that all formulations had <1% drug loss in the first minute (the tracking phase); furthermore, the 90:10 ratio exhibited optimal drug release in the following 3 min, corresponding to the deployment phase in DCB angioplasty. Analysis of micelle loading capacity (LC), encapsulation efficiency (EE), size, and structure indicated an increase in both LC and EE with higher EVE content and a corresponding enlargement in micelle size. Given these findings, the optimized formula provided a consistent coating on commercial balloons, highlighting the potential of using P123 for DCB drug coating and release.

An integrated design strategy coupling additive manufacturing and matrix-assisted pulsed laser evaporation (MAPLE) towards the development of a new concept 3D scaffold with improved properties for tissue regeneration.

Bioinspired strategies for scaffold design and optimization were improved by the introduction of Additive Manufacturing (AM), thus allowing for replicating and reproducing complex shapes and structures in a reliable manner, adopting different kinds of polymeric and nanocomposite materials properly combined according to the features of the natural host tissues. Benefiting from recent findings in AM, a Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique was employed for obtaining graphene-like material (GL) uniform coatings on 3D scaffolds for tissue repair strategies, towards the development of a new concept 3D scaffold with controlled morphological/architectural and surface features and mechanical and biological properties. The effect of the material-design combination through an integrated technological approach (i.e., MAPLE deposition of GL on 3D AM PCL scaffolds) was assessed through scanning electron microscopy, atomic force microscopy, contact angle measurements, mechanical measurements and biological analyses (cell viability assay and alkaline phosphatase activity) in conjunction with confocal laser scanning microscopy. The differentiation of hMSCs towards the osteoblast phenotype was also investigated analysing the gene expression profile. The obtained findings provided a further insight into the development of improved strategies for the functionalization or combination of GL with other materials and 3D structures in a hybrid fashion for ensuring a tighter adhesion onto the substrates, improving cell fate over time, without negatively altering the mechanical properties and behaviour of the neat constructs. In particular, the results provided interesting information, making 3D AM GL-coated scaffolds potential candidates for bone tissue engineering.

Effects of the substrate rotation speed on the structure and uniformity of YSZ coatings fabricated by electron-beam synthesis in the forevacuum pressure range

Effects of the substrate rotation speed on the structure and uniformity of YSZ coatings fabricated by electron-beam synthesis in the forevacuum pressure range

PDA@α-ZrP/SiO2 incorporated phosphate coating with enhanced corrosion resistance and friction resistance.

In this study, α-ZrP and SiO2 composite nanomaterials were used to as phosphating accelerators. Experiments show that 2D nanosheets and 0D nanoparticles modified by PDA (PDA@α-ZrP/SiO2) play a synergistic role in effectively increasing the number of phosphate crystals and refining the crystal's size, thereby forming dense and uniform phosphate coatings. The friction resistance and corrosion resistance of phosphate coatings are simultaneously enhanced. Especially when the PDA@α-ZrP/SiO2 addition amount is 0.55 g L-1, the coating porosity of phosphate coating drops from 64.24% to 4.38%. The friction resistance coefficient drops from 0.32 to 0.02 and the polarization resistance increased from 1381 Ω cm2 to 20 520 Ω cm2.

Study of protective hard coatings of SiO&lt;sub&gt;2&lt;/sub&gt;-TiO&lt;sub&gt;2&lt;/sub&gt; on aluminum substrates

&lt;abstract&gt; &lt;p&gt;Aluminum alloys are frequently employed in the aeronautics industry due to the remarkable mechanical properties and lightweight nature of these materials. Moreover, thin film coatings are commonly applied in order to improve the corrosion resistance under harsh environments. In this work, Al 7075-T6 substrates were coated with nanostructured SiO&lt;sub&gt;2&lt;/sub&gt;-TiO&lt;sub&gt;2&lt;/sub&gt; films using a sol-gel method. The experimental approach initially consisted in the preparation of a precursor agent using tetraethyl orthosilicate (TEOS) and triethoxy(octyl)silane (ETOS). Subsequently, nanoparticles of SiO&lt;sub&gt;2&lt;/sub&gt;-TiO&lt;sub&gt;2&lt;/sub&gt; were mixed in order to develop thin films using a one-step dip coating method. The roughness, nanoindentation and corrosion properties were evaluated for the coated substrates. A finite element model was created for the nanoindentation test, which determined the mechanical response between the film-contact interface during loading conditions. The average hardness, elastic modulus and critical loads leading to fracture were verified. The nanoindentation test presented a significant increase in hardness for the coated Al 7075-T6 alloy, reaching a value of 4.6 GPa. The SiO&lt;sub&gt;2&lt;/sub&gt;-TiO&lt;sub&gt;2&lt;/sub&gt; thin films presented uniform and compact surface coatings with high mechanical properties. Furthermore, the performed corrosion tests indicated moderate protection by the SiO&lt;sub&gt;2&lt;/sub&gt;-TiO&lt;sub&gt;2&lt;/sub&gt; thin films. The SiO&lt;sub&gt;2&lt;/sub&gt;-TiO&lt;sub&gt;2&lt;/sub&gt; thin films displayed a generalized corrosion throughout the surface, presenting oxides and fractured crystals in localized regions.&lt;/p&gt; &lt;/abstract&gt;

Promoting uniform zinc coatings through the use of quaternary ammonium salts based on phthalimide as electroplating additives

Compound PI5 forms a homogeneous electroplated zinc layer by adsorption.

PHYSICAL AND MECHANICAL PROPERTIES AND OPERATIONAL CHARACTERISTICS OF CORONA SPRAYED POWDER COATINGS

This article presents the results from an examination of the physical and mechanical properties of powder coatings based on different binding agents, including epoxy, epoxy-polyester, polyester, polyurethane, and silicone. The coatings that showed the highest results in all tests are epoxy, epoxy-polyester, and polyester. The study investigated the thickness and uniformity of coatings achieved under different spraying conditions. Specific spraying system modes were identified to achieve uniform coatings with predetermined thicknesses. The research highlights the potential application of powder coatings as protective and matching layers for ultrasonic sensors.

Recent development and applications of electrodeposition biocoatings on medical titanium for bone repair.

Bioactive coatings play a crucial role in enhancing the osseointegration of titanium implants for bone repair. Electrodeposition offers a versatile and efficient technique to deposit uniform coatings onto titanium surfaces, endowing implants with antibacterial properties, controlled drug release, enhanced osteoblast adhesion, and even smart responsiveness. This review summarizes the recent advancements in bioactive coatings for titanium implants used in bone repair, focusing on various electrodeposition strategies based on material-structure synergy. Firstly, it outlines different titanium implant materials and bioactive coating materials suitable for bone repair. Then, it introduces various electrodeposition methods, including electrophoretic deposition, anodization, micro-arc oxidation, electrochemical etching, electrochemical polymerization, and electrochemical deposition, discussing their applications in antibacterial, osteogenic, drug delivery, and smart responsiveness. Finally, it discusses the challenges encountered in the electrodeposition of coatings for titanium implants in bone repair and potential solutions.

Uniformity optimization of ion beam sputtering coating equipment based on strong current ion source

The widespread application of ion beam sputtering coating, especially in optical devices, requires the improvement of beam current intensity and uniformity of large-area uniform coatings. The advent of high current Penning sources offers a potential solution. This study introduces an automated optimization simulation method based on a three-electrode extraction system to investigate its influence on ion beam quality and uniformity. Focusing on high current intensity and uniformity, our simulation explores the effects of plasma electrode, inhibition electrode, and extraction electrode angles and distances on ion beam performance. Evaluation metrics include average beam intensity density, average energy of a single particle, and reciprocal variance of each macro particle position, which are achieved through normalization functions, allowing comprehensive comparison of simulation results. To assess coating efficiency, we estimate sputtering yield and depth. The study identifies patterns among electrodes and emphasizes the influence of different ion ratios on beam extraction. The results indicate that optimizing the angle of the plasma electrode and the distance of the suppressed electrode yields a highly uniform ion beam for low charge ions. However, for highly charged ions, similar optimization will reduce the current strength, so compensation needs to be achieved through electrode shape optimization. This research provides a model for systematically optimizing the three-electrode extraction system, guiding researchers in achieving optimal solutions based on ion source characteristics and application requirements. Additionally, we introduce a method of estimating the sputtering depth of mixed ion beams. This study provides valuable insights for advancing ion beam sputtering coating technology and reference for making the decision on design and application of ion source.

Electrochemical method of deposition of an alumina coating on carbon fiber

Electrochemically produced oxide coatings have a wide range of potential applications. Despite this, works on the electrochemical deposition of aluminum oxide can be counted on the fingers of one hand, and carbon fiber has not previously been used as a substrate. This work aimed to test and study the mentioned method of depositing aluminum oxide coatings, examine the structure of the resulting coatings, and investigate the possibility of using carbon fiber as a substrate. In this work, we proposed a new method for electrochemical deposition of aluminum oxide coatings from an aqueous electrolyte. The method permitted obtaining uniform and continuous coatings with a thickness of about 300 nm on flat glassy carbon substrates. The effect of current density, deposition time, and electrolyte composition on the thickness and uniformity of the coating was studied. The proposed method was successfully applied to the deposition of the coating on carbon fiber. In addition, the coatings had sufficient continuity, and their thickness reached 100 nm.

Gold Ultralow Loading on Nickel Foam for Nitrogen Electrochemical Reduction

Gold electroless deposition on nickel foam offers several advantages over traditional electrodeposition techniques. One of the main advantages is that it can produce uniform thickness coatings on complex shapes and geometries, such as porous and three-dimensional substrates like nickel foam. The resulting gold-nickel foam composite has high surface area and good electrical conductivity, making it suitable for various electrochemical applications, including catalysis, sensing, and energy storage.In this work we focused on the development of synthetic strategies to grow and optimize the surface coverage of gold on nickel foam and the evaluation of its suitability for the electrochemical reduction of nitrogen for ammonia synthesis.The gold electroless deposition on Ni Foam has been obtained by immersion in aqueous solution containing KAuCl4 and HCl, with or without stirring and addition of a surfactant agent (Isopropyl Alcohol). Depositions were performed by varying the immersion time from 30 seconds to 30 minutes. Scanning electron microscopy (SEM) has been employed to compare different deposition conditions and to optimize the morphology of the nanofilms, allowing higher catalytic activity. The electrochemical performance of the gold deposited on nickel foam was evaluated in a standard two compartments electrochemical cell using a Pt wire as counter electrode (CE), a saturated calomel electrode (SCE, saturated KCl) as reference and 0.1 M Na2SO4 solution as electrolyte. Electrochemical active surface area (EASA) and linear sweep voltammetry (LSV) have been adopted to evaluate the active area and the overpotential toward hydrogen evolution reaction (HER). Chronoamperometry experiments were carried out at various potentials to evaluate the performance of the catalyst for the electroreduction of nitrogen and ammonia synthesis.The amount of ammonia produced was measured by the indophenol blue method.The maximum NH3 yield of 2.8x10-11 mol s-1 cm-2 was achieved at -0.045 V vs RHE. The maximum faradaic efficiency of 5.8% was achieved at more positive potential (0.015 V vs RHE) due to the HER.The results show that the gold on nickel foam exhibits excellent electrochemical stability and high conductivity.This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under grant agreement No 101006941. This project started on the 1st of November 2020 with a duration of 42 months.

Pulse and Pulse/Reverse Techniques for Electrodeposition of Rhenium and Refractory Metals

Refractory metals possess unique properties including high melting points, high hardness at room temperature, chemical resistance, and high density. Electrodeposition of refractory metals is of interest as a scalable approach to apply uniform coatings to enable a wide range of applications in aerospace, nuclear, catalysis, biomedical fields. This talk will focus on pulse electrochemical variables to enable methods to electrodeposit high quality metallic rhenium (Re).Re has traditionally been difficult to deposit from aqueous solutions due to the over potential for hydrogen evolution and complex electrochemical reactions. Electrodeposition of rhenium usually occurs from the perrhenate ion (ReO4-) with an oxidation state of +7. The exact mechanism to reduce the perrhenate ion from +7 to metallic rhenium is still unknown. It is unlikely that the 7 electrons transfer in a single step, so reduction likely occurs through intermediate oxide species including ReO2, ReO3 and Re2O5. Combined with the hydrogen evolution reaction, Re coatings are generally deposited at low faradaic efficiency, are brittle, and limited in thickness (sub-micron). In our previous work, water-in-salt electrolytes and complexing additives have enabled resolution of some of the issues associated with this complexity and a range of deposit qualities, though cracking issues remain and coating quality issues still needed optimization.Herein, we present on the effects of pulsed electrochemical approaches to eliminate cracking in the film by balancing nucleation and growth and the competing hydrogen evolution reaction. A custom high-throughput cell was developed to rapidly screen parameters and explore time-dependent evolution of the electrodeposition processes.

Single-Component Hydrophilic Terpolymer Thin Film Systems for Imparting Surface Chemical Versatility on Various Substrates.

We demonstrate a single-component hydrophilic photocrosslinkable copolymer system that incorporates all critical functionalities into one chain. This design allows for the creation of uniform functional organic coatings on a variety of substrates. The copolymers were composed of a poly(ethylene oxide)-containing monomer, a monomer that can release a primary amine upon UV light, and a monomer with reactive epoxide or cyclic dithiocarbonate with a primary amine. These copolymers are easily incorporated into the solution-casting process using polar solvents. Furthermore, the resulting coating can be readily stabilized through UV light-induced crosslinking, providing an advantage for controlling the surface properties of various substrates. The photocrosslinking capability further enables us to photolithographically define stable polymer domains in a desirable region. The resulting copolymer coatings were chemically versatile in immobilizing complex molecules by (i) post-crosslinking functionalization with the reactive groups on the surface and (ii) the formation of a composite coating by mixing varying amounts of a protein of interest, i.e., fish skin gelatin, which can form a uniform dual crosslinked network. The number of functionalization sites in a thin film could be controlled by tuning the composition of the copolymers. In photocrosslinking and subsequent functionalizations, we assessed the reactivity of the epoxide and cyclic dithiocarbonate with the generated primary amine. Moreover, the orthogonality of the possible reactions of the presented reactive functionalities in the crosslinked thin films with complex molecules is assessed. The resulting copolymer coatings were further utilized to define a hydrophobic surface or an active surface for the adhesion of biological objects.

Frequency Response Evaluation as Diagnostic and Optimization Tool for Pulsed Unipolar Plasma Electrolytic Oxidation Process and Resultant Coatings on Zirconium.

This study aims to bridge various diagnostic tools for the development of smart plasma electrolytic oxidation (PEO) technologies. PEO treatments of commercially pure Zr were carried out using the pulsed unipolar polarisation (PUP) regime with frequency sweep in an alkaline phosphate-silicate electrolyte. Methods of in situ impedance spectroscopy and electrical transient analysis were used for the process diagnostics under the video imaging of the PEO. Two cutoff frequencies, 170-190 Hz and 620-650 Hz, were identified for the PEO-assisted charge transfer process. An equivalent circuit for the metal-oxide-electrolyte system under PUP PEO conditions was developed; from the capacitance values, two geometrical dielectric barriers were evaluated: a thinner 0.5-1 µm inner layer of the coating and a thicker 4-6 µm outer layer. These estimates were in agreement with the coating cross-sectional morphology. Based on comparing the results obtained using different techniques, the frequencies at which the uniform coatings with the best protective properties were formed were identified. For the selected electrolyte system and polarisation regime, these frequencies ranged from 2 to 5 kHz where the overall circuit reactance was minimal; therefore, the power factor was as close to one as possible. This opens the possibilities for the optimization of the pulsed PEO process and online control of unobservable surface characteristics, e.g., the thickness of the coating layers, thus contributing towards the development of smart PEO technologies.

Surface Characteristics, Properties and Wear Resistance OF TIB2 BASED Hard-Alloy Coatings Obtained by Electrospark Deposition at Negative Polarity on Ti6Al4V Alloy

In the present work, the possibilities of improving the surface properties of titanium alloy Ti6Al4V by electrospark deposition (ESD) at negative polarity were investigated. The coatings were deposited with a TiB2-TiAl-based hard-alloy electrode with nano-sized additives of NbC and ZrO2. The effect of polarity in ESD at low pulse energy (0.01-0.07 J) on the surface roughness, thickness, composition and structure of coatings was studied by profilometric, metallographic, XRD, SEM and EDS methods. In both polarities, dense and uniform coatings were obtained with roughness and thickness, which could be varied by changing the ESD modes within the range Ra=1.5÷4.5 µm, d= 6÷20 µm and microhardness from 9 to 12 GPa, respectively. It was found that the negative polarity coatings obtained are denser and uniform with higher thickness, lower roughness, finer structure, and lower coefficient of friction, and can be successfully used to reduce the surface roughness and defects of 3D printed titanium alloy. Abrasion and erosion wear tests showed that the wear resistance of coated titanium surfaces at both polarities was 2.2 to 3.5 times higher than that of the substrate. Coatings deposited in positive polarity demonstrated higher resistance to abrasive wear, while those in negative polarity are more resistant to erosive wear.

Controlling lateral thickness distributions of magnetron sputtering deposited coatings using shadow masks

A lateral thickness distribution control model for magnetron sputter-deposited coatings was established using shadow masks. The sputtering yield distributions were investigated in detail, particularly the variation trend from straight to curved tracks, based on the erosion profiles of rectangular targets. On this basis, a mathematical model for a planetary rotation system was established to simulate the thickness distribution of coatings on different substrates, including flat, spherical, and aspherical shapes, accurately. A shadow mask with multi-Gaussian outlines was proposed, and the coating thickness was effectively controlled according to specific distribution requirements by optimizing the profile parameters of the masks using a genetic algorithm. Flat and ellipsoidal substrates were used to prepare Mo and Si monolayer coatings to verify the effectiveness of this model. Although the diameters of the substrates were close to the lengths of the rectangular targets, the results showed that uniform coatings were obtained on the flat substrate, whereas the ellipsoidal substrate exhibited high-precision gradient coatings, with maximum deviations below 0.5%, which proved the validity of this approach.

Silicon Radical-Induced CH4 Dissociation for Uniform Graphene Coating on Silica Surface.

Due to the manufacturability of highly well-defined structures and wide-range versatility in its microstructure, SiO2 is an attractive template for synthesizing graphene frameworks with the desired pore structure. However, its intrinsic inertness constrains the graphene formation via methane chemical vapor deposition. This work overcomes this challenge by successfully achieving uniform graphene coating on a trimethylsilyl-modified SiO2 (denote TMS-MPS). Remarkably, the onset temperature for graphene growth dropped to 720°C for the TMS-MPS, as compared to the 885°C of the pristine SiO2. This is found to be mainly from the Si radicals formed from the decomposition of the surface TMS groups. Both experimental and computational results suggest a strong catalytic effect of the Si radicals on the CH4 dissociation. The surface engineering of SiO2 templates facilitates the synthesis of high-quality graphene sheets. As a result, the graphene-coated SiO2 composite exhibits a high electrical conductivity of 0.25Scm-1. Moreover, the removal of the TMP-MPS template has released a graphene framework that replicates the parental TMS-MPS template on both micro- and nano- scales. This study provides tremendous insights into graphene growth chemistries as well as establishes a promising methodology for synthesizing graphene-based materials with pre-designed microstructures and porosity.