Smooth Coatings Research Articles

Surfactant-enhanced chitosan coating extends postharvest shelf-life of Keitt mango

The surface properties of Keitt mango and wettability of chitosan (CH) coatings containing ethyl lauroyl arginate (LAE, an ionic surfactant), and sucrose monolaurate (SML, a non-ionic surfactant) were investigated. The Keitt mangoes were coated with different chitosan-based solutions and stored at room temperature (25.0 ± 0.6 °C) for 35 days. The Keitt mango surface had low surface energy (<100 mN/m) with high dispersive component (17.70 ± 1.49–22.86 ± 1.02 mN/m). SML and LAE surfactants significantly (P < 0.05) lowered the surface tension of the CH coating solution by 6.94, and 24.13 mN/m, respectively. As a result, the wettability of CH based coating on mangoes was improved to −68.37 ± 0.01 mN/m (CH-SML), and −30.29 ± 0.00 mN/m (CH-LAE) compared with CH (−76.45 ± 0.04 mN/m), resulting in smooth and homogeneous coatings. The storage test results indicated a significant reduction (P < 0.05) in disease incidence and weight loss by the CH-SML and CH-LAE coatings and the coated mangoes were firmer with lower pH values compared with the control. This study suggests that CH-LAE and CH-SML coatings can effectively extend the shelf-life of Keitt mangoes by 10 and > 15 days, respectively.

Microstructural and mechanical properties of TiN/CrN and TiSiN/CrN multilayer coatings deposited in an industrial-scale HiPIMS system: Effect of the Si incorporation

Surface engineering through the deposition of advanced coatings, particularly multilayer coatings has gained significant interest for enhancing the performance of coated parts. The incorporation of Si into TiN coatings has shown promise for improving hardness, oxidation resistance, and thermal stability, while high-power impulse magnetron sputtering (HiPIMS) has emerged as a technique to deposit coatings with exceptional properties. However, TiN/CrN and TiSiN/CrN coatings deposited by HiPIMS remain relatively unexplored. In this study, different TiN/CrN and TiSiN/CrN multilayer coatings with different bilayer periods from 5 to 85 nm were deposited using an industrial-scale HiPIMS reactor, and their microstructure and mechanical properties were investigated using advanced characterization techniques. Results revealed successful deposition of smooth and compact coatings with controlled bilayer periods. X-ray diffraction analysis showed separate crystalline phases for coatings with high bilayer periods, while those with smaller bilayer periods exhibited peak-overlapping and superlattice overtones, especially for the TiN/CrN coatings. Epitaxial grain growth was confirmed by high-resolution transmission electron microscopy (HRTEM). HRTEM and electron energy-loss spectroscopy measurements confirmed Si incorporation into the TiN crystal lattice of TiSiN/CrN coatings reducing the crystallinity, especially for coatings with smaller bilayer periods. Nanoindentation tests revealed that coatings with a bilayer period of 15–20 nm displayed the highest hardness values regardless of the composition. The mechanical properties of the TiSiN/CrN coatings showed no improvement over those of the TiN/CrN coatings, attributed to the Si induced amorphization of the Ti(Si)N phase and the absence of SiNx phase segregation within the TiN nanocrystals in these coatings. These findings provide valuable insights into the microstructure and mechanical properties of TiN/CrN and TiSiN/CrN multilayer coatings deposited by HiPIMS in an industrial scale reactor, paving the way for their application in various industrial sectors.

WSCF coatings tested under various environmental conditions: A multivariate tribological analysis

This study examines the influence of carbon (C) and fluorine (F) on the tribological and mechanical properties of WSCF coatings. WSCF-coated substrates were prepared with varying levels of C (10.4 to 18.7 at%) and F (5.3 to 9.3 at%) using DC reactive magnetron sputtering. Tribological performance was evaluated at 25 °C and 200 °C in dry and lubricated conditions. Alloying led to thicker, more amorphous, denser, and smoother coatings. An exceptional coefficient of friction (COF) as low as 0.008 was observed for WSCF2 (15.4 at% C and 9.3 at% F). Principal component analysis (PCA) revealed high F-doped coating in WSCF2 demonstrated improved tribological performance, resulting in a 38 % reduction in COF at 25 °C and dry conditions.

Two-step ALD process for non-oxide ceramic deposition: the example of boron nitride

Atomic layer deposition (ALD) based on polymer-derived ceramics (PDCs) chemistry is used for the fabrication of boron nitride thin films from reaction between trichloroborazine and hexamethyldisilazane. The transposition of the PDCs route to ALD is highly appealing for depositing ceramics, especially non-oxide ones, as it offers various molecular precursors. From a two-step approach composed of an ALD process forming a so-called preceramic film and its subsequent ceramization, conformal and homogenous BN layers are successfully synthesized on various inorganic substrates. In the first stage, smooth polyborazine coatings are obtained at a temperature as low as 90 °C. The saturation and self-limitation of the ALD gas-surface reactions are verified. Intriguingly, three ALD windows seem to exist and are attributed to change in ligand exchange. After the ceramization stage using a heat treatment, conformal near-stoichiometric BN layers are obtained. Their structure in terms of crystallinity can be adjusted from amorphous to well-crystalline sp2 phase by controlling the treatment temperature. In particular, a crystallization onset occurs at 1000 °C and well defined sp2 crystalline planes oriented parallel to the surface are noted after ceramization at 1350 °C. Finally, side-modification of the substrate surface induced by the thermal treatment appears to impact on the final BN topography and defect generation.

Zirconium-modified organosiloxane resin for high-temperature-resistant coatings

Organosiloxane resins typically undergo significant thermal degradation, with notable mass loss between 400 °C and 800 °C, which limits its applications in wider fields. To address this problem, zirconium (Zr) was incorporated into the backbone of organosiloxane resins via the sol-gel process. The mass retention of the Zr-modified organosiloxane resins at 1000 °C increased with Zr content, reaching 95.47 wt% and 97.29 wt% in air and argon, respectively. The accretion of the mass retention can be attributed to the formation of crystalline zirconium oxide (ZrO2) structures within the resin matrix. The Zr-modified organosiloxane resins showed storage stability even after 3 months. Uniform, smooth and discernible defect free coatings with thickness of approximately 1 μm were obtained through spin-coating. Compared with the pure organosiloxane coating, the Zr-modified organosiloxane coating showed better thermal stability without significant cracks after heat treatment in air at 450 °C. The results suggest potential applications of this Zr-modified ploysiloxane in thermal barrier protection technologies.

Evaluating the corrosion and tribological performance of nanostructured CrN/TiN and TiN/CrN configurations applied on 410 stainless steel

ABSTRACT This study aims to compare the corrosion and tribological performance of TiN/CrN and CrN/TiN nanostructured multi-layer coatings deposited through cathodic arc evaporation PVD on 410-grade stainless steel. Both coating configurations were available in smooth (polished) and rough states. For the deposition of multi-layer coatings, a middle layer containing Cr and CrN was deposited to the substrate, followed by alternating nanolayers of TiN and CrN. finally, an upper layer of either CrN or TiN was applied. The nanoindentation test revealed that the hardness, Young’s modulus, H/E, and H3/E2 ratios of the coating with a TiN upper layer were 5.57, 1.42, 3.86, and 85.39 times of the substrate, respectively. At the coating with CrN upper layer, these values were 4.04, 1.13, 3.53, and 51.68 times of the substrate, respectively. Results showed that increasing the H/E and H3/E2 ratios increased wear resistance. Wear rates of smooth and rough TiN coatings and smooth and rough CrN coatings were reduced by 86%, 99%, 53%, and 26%, respectively, compared to the substrate. Results of the corrosion test showed that the rough CrN coating had greater corrosion resistance than the coating with a TiN upper layer and the substrate due to its higher hydrophobicity.

One-step rapid formation of wrinkled fractal antibiofouling coatings from environmentally friendly, waste-derived terpenes

Wrinkled coatings are a potential drug-free method for mitigating bacterial attachment and biofilm formation on materials such as medical and food grade steel. However, their fabrication typically requires multiple steps and often the use of a stimulus to induce wrinkle formation. Here, we report a facile plasma-based method for rapid fabrication of thin (<250 nm) polymer coatings from a single environmentally friendly precursor, where wrinkle formation and fractal pattern development are controlled solely by varying the deposition time from 3 s to 60 s. We propose a mechanism behind the observed in situ development of wrinkles in plasma, as well as demonstrate how introducing specific topographical features on the surface of the substrata can result int the formation of even more complex, ordered wrinkle patterns arising from the non-uniformity of plasma when in contact with structured surfaces. Thus-fabricated wrinkled surfaces show good adhesion to substrate and an antifouling activity that is not observed in the equivalent smooth coatings and hence is attributed to the specific pattern of wrinkles.

Thermo-mechanical finite element analysis of the solid-state metal deposition via lateral friction surfacing

Lateral friction surfacing (LFS) is a novel variation of the friction surfacing (FS) process for solid-state fabrication of ultra-thin and smooth metal coatings. In the LFS technique, pressing the lateral side of a rotating rod against the substrate's surface generates frictional heat and plastic deformation, leading to the deposition of consumable material from the lateral surface of the rod onto the substrate. This study presents numerical analysis for such a complex coupled thermo-mechanical process to investigate the distribution of various variables such as temperatures, local pressure, stress, and strain throughout the consumable rod and substrate. A finite element model of the process was developed through ABAQUS/Explicit method to investigate the thermo-mechanical response of rod and substrate materials by incorporating various features such as process parameters, mechanical behaviors of materials, temperature-dependent material properties, and failure criteria. The finite element model was validated by conducting experimental analysis using the same materials and values of process parameters. The finite element simulation results were consistent with previous experiments and affirmed that process temperature is lower than in conventional FS and localized in a small area, which can reduce thermal impacts on the consumable rod and substrate materials. Although the majority of the frictional heat was transferred to the Al6061-T6 rod due to its higher thermal conductivity, it was revealed that the maximum process temperature occurred on the mild steel substrate. The results of the study demonstrate that selecting an appropriate dwell-phase duration not only enhances the material's temperature to facilitate improved deposition but also ensures more consistent contact across all points along the rod's side, resulting in a uniform deposition.

APPLICATION OF INTERNAL COATINGS IN ORDER TO INCREASE THE EFFICIENCY OF NATURAL GAS TRANSPORTATION AND REDUCE CORROSION DAMAGE TO THE PIPELINE WALL

With the development of the fuel and energy complex of the Russian Federation, new problems and challenges are emerging that require new scientific and technical solutions. At the moment, the length of pipelines through which various types of hydrocarbons are transported is growing. At the same time, the number of easily recoverable hydrocarbon reserves decreases every year, and at the same time their quality characteristics deteriorate, there is a need for a higher degree of their preparation for further transportation and additional purification. As a result, the corrosion effect on the pipe wall increases, leading to a decrease in the service life of the pipeline. Along with this, the share of heavy components in hydrocarbon mixtures transported through pipeline systems increases, which leads to an increase in energy costs for their transportation. These factors lead to a qualitative change in transportation conditions and, accordingly, to the need for additional technical solutions to protect pipes from corrosion and ensure the efficient operation of pipeline systems due to the increase in pressure losses along the length of the pipeline. As a result, it is necessary to achieve a reduction in energy costs for the transportation of natural gas. The problems of reducing pressure losses during natural gas transportation, as well as preventing corrosion wear of the internal cavity of the main gas pipelines are very relevant and require serious research to solve them.One of the effective ways to reduce energy loss during natural gas transportation and protect the inner wall of the pipeline from corrosion damage is the use of internal smooth polymer coatings of steel pipelines. At the same time, due to the growing influence of the negative factors listed earlier, there is a need for a critical analysis of existing technical solutions for their compliance with the current state and prospects for the development of the oil and gas complex.The article discusses existing and promising developments in the field of application of internal coatings in order to increase the efficiency of natural gas transportation and reduce the amount of corrosion damage to the pipeline wall.

Exploring dengue genome to design effective multi epitope-based peptide vaccine by immunoinformatics approach against all serotypes of dengue virus

Dengue fever is an acute tropical disease that is spread by Aedes species mosquitoes. It is a virus-mediated illness that causes headaches, fever, severe joint and muscle pain, swollen glands (lymphadenopathy), and rashes. Every year, 390 million people around the world suffer from it and ∼20 % die from cases that are left untreated. The virus is transmitted to humans by mosquito bites of infected Aedes species. When it gets into the body, its envelope protein attaches to the host cell surface receptor and initiates the viral infection cycle by the formation of a smooth coat with icosahedral symmetry. Due to its high mutation-prone nature and differences in protein sequences among serotypes, it is difficult to develop a stable vaccine suitable against all serotypes. In this study, a software-based vaccinology approach was used to design a vaccine construct against the envelope protein of all four subtypes of the dengue virus. This construct was designed by joining two epitopes of the protein. One epitope was taken from the envelope protein of DEN-2 which was conserved for DEN-1, DEN-2, and DEN-3, and another epitope from the same protein of DEN-4 serotype as the sequence composition of the protein is slightly different in these two groups of serotypes. Here, firstly 18 epitopes for dengue virus-1, 2, 3, and 12 epitopes for dengue virus-4 were retrieved based on the highest combined score of NetCTL server analysis of human leukocyte antigen (HLA) supertypes. Among them, the epitope MAILGDTAW has shown 100 % conservancy in strains of dengue virus 1, 2, 3, and KLRIKGMSY, TTAKEVALL, TPRSPSVEV, FRKGSSIGK, KTWLVHKQW have shown 100 % conservancy in dengue virus 4. In population coverage analysis, MAILGDTAW has shown 88.63 % and FRKGSSIGK has shown 90.72 % (highest among other DEN-4 epitopes) population coverage of the entire world population. These two epitopes along with their 15-mer extensions (MHCII binding peptides) were found as non-allergen and non-toxic. Finally, the two different 15-mer extensions (to get 100 % sequence conservancy) of the epitope MAILGDTAW and the 15-mer extension of the epitope FRKGSSIGK were put together using an EAAAK linker to construct the multi-epitope vaccine. In-vivo analysis of the proposed vaccine construct would aid in the development of a functional immune response that would eradicate dengue complications worldwide.

Inkjet Printed Ti3C2 Electrodes for Anode-Free Zinc-Ion Battery

Additive manufacturing techniques are coming to the fore in many technological fields as cheaper and more versatile manufacturing routes alternative to the physical deposition methods. In particular, when miniaturized, thin-film or patterned structures are needed, Inkjet printing (IJP) has been widely demonstrated as suitable techniques to fabricate coated electrodes and microdevices for many applications including energy storage 1. In this regard, Zinc-ion batteries (ZIBs) are a promising alternative to the traditional lithium-ion batteries due to the abundance and low cost of zinc. In ZIBs, a metallic Zn chips is usually employed as the anode and a variety of materials, such as metal oxides or polymers, as the cathode. Zinc-ion batteries have the potential for high energy density and long cycle life, however they suffer of the well-known issue of Zn dendritic growth and poor efficiency of the plating-dissolution process 2. Ti3C2 MXene have been recently demonstrated as a high-performance “zincophilic” substrate for smooth and efficient zinc with high reversibility 3,4.In this work, we investigate inkjet-printed Ti3C2 MXene thin coatings as an ideal substrate for anode-free ZIBs. Stable aqueous Ti3C2 MXene inks were formulated and successfully inkjet printed on different substrates. The zinc metal nucleation phenomena on MXene 2D sheets were investigated by electrochemical potentiodynamic polarization techniques as well as galvanostatic ones, comparing them to a zinc metallic foil. Ex-situ electron scanning microscopy (SEM) analyses were employed to observe the plated Zn morphology after cycling at both low and high current density. Taking advantage of the smooth inkjet-printed Ti3C2 MXene coatings, electrochemical atomic force microscopy (EC-AFM) was used for the first time to perform in-operando investigation of the Zn plating process, allowing to reveal the early stage Zn plating mechanism on the as-printed Bibliography C. Li, F. Bu, Q. Wang, and X. Liu, Advanced Materials Interfaces, 9, 2201051 (2022).K. Wang, ACS Omega, 5, 10225–10227 (2020).J. M. Park et al., Journal of Energy Chemistry, 76, 187–194 (2023).Z. Gong et al., Journal of Colloid and Interface Science, 625, 700–710 (2022).

Hard and Highly Adhesive AlMgB14 Coatings RF Sputtered on Tungsten Carbide and High-Speed Steel

We report a new industrial application of aluminum magnesium boride AlMgB14 (BAM) coatings to enhance the hardness of tungsten carbide ceramic (WC-Co) and high-speed steel tools. BAM films were deposited by RF magnetron sputtering of a single dense stoichiometric ceramic target onto commercial WC-Co turning inserts and R6M5 steel drill bits. High target sputtering power and sufficiently short target-to-substrate distance were found to be critical processing conditions. Very smooth (6.6 nm RMS surface roughness onto Si wafers) and hard AlMgB14 coatings enhance the hardness of WC-Co inserts and high-speed R6M5 steel by a factor of two and three, respectively. Complete coating spallation failure occurred at a scratch adhesion strength of 18 N. High work of adhesion and low friction coefficient, estimated for BAM onto drill bits, was as high as 64 J/m2 and as low as 0.07, respectively, more than twice the surpass characteristics of N-doped diamond-like carbon (DLC) films deposited onto nitride high-speed W6Mo5Cr4V2 steel.

Degradable Plasma-Polymerized Poly(Ethylene Glycol)-Like Coating as a Matrix for Food-Packaging Applications.

Currently, there is considerable interest in seeking an environmentally friendly technique that is neither thermally nor organic solvent-dependent for producing advanced polymer films for food-packaging applications. Among different approaches, plasma polymerization is a promising method that can deposit biodegradable coatings on top of polymer films. In this study, an atmospheric-pressure aerosol-assisted plasma deposition method was employed to develop a poly(ethylene glycol) (PEG)-like coating, which can act as a potential matrix for antimicrobial agents, by envisioning controlled-release food-packaging applications. Different plasma operating parameters, including the input power, monomer flow rate, and gap between the edge of the plasma head and substrate, were optimized to produce a PEG-like coating with a desirable water stability level and that can be biodegradable. The findings revealed that increased distance between the plasma head and substrate intensified gas-phase nucleation and diluted the active plasma species, which in turn led to the formation of a non-conformal rough coating. Conversely, at short plasma-substrate distances, smooth conformal coatings were obtained. Furthermore, at low input powers (<250 W), the chemical structure of the precursor was mostly preserved with a high retention of C-O functional groups due to limited monomer fragmentation. At the same time, these coatings exhibit low stability in water, which could be attributed to their low cross-linking degree. Increasing the power to 350 W resulted in the loss of the PEG-like chemical structure, which is due to the enhanced monomer fragmentation at high power. Nevertheless, owing to the enhanced cross-linking degree, these coatings were more stable in water. Finally, it could be concluded that a moderate input power (250-300 W) should be applied to obtain an acceptable tradeoff between the coating stability and PEG resemblance.

Construction of silver-coated high translucent zirconia implanting abutment material and its property of antibacterial

High translucent zirconia (HTZ) has excellent mechanical properties, biocompatibility, and good semi-translucency making it an ideal material for aesthetic anterior dental implant abutments without antibacterial properties. In the oral environment, the surface of the abutment material is susceptible to microbial adhesion and biofilm formation, which can lead to infection or peri-implantitis and even implant failure. This study aims to promote the formation of a biological seal at the implant-soft tissue interface by modifying the HTZ surface, using the load-bearing capacity of the aluminosilicate porous structure and the broad-spectrum antibacterial effect of silver nanoparticles to prevent peri-implant bacterial infection and inflammation and to improve the success rate and prolong the use of the implant. FE-SEM (field emission scanning electron microscopes), EDS (energy dispersive spectroscopy), and XPS (X-ray photoelectron spectroscopy) results showed that aluminosilicate non-vacuum sintering can form open micro- and nanoporous structures on HTZ surfaces, and that porous aluminosilicate coatings obtain a larger number, smaller size, and more uniformly shaped silver nanoparticles than smooth aluminosilicate coatings, and could be deposited deeper in the coating. The ICP-AES (inductively coupled plasma-atomic emission spectroscopy) results showed that the early silver ion release of both the smooth silver coating and the porous silver coating was obvious, the silver ion concentration released by the former was higher than that of the latter. However, the silver ion concentration released by the porous silver coating was higher than that of the smooth coating when the release slowed down. Both smooth and porous silver coatings both inhibited E. coli (Escherichia coli), S. aureus (Staphylococcus aureus), and L. acidophilus (L. acidophilus), and porous silver coatings had stronger antibacterial properties. The silver coating was successfully constructed on the surface of HTZ, through aluminium silicate sintering and silver nitrate solution impregnation. It was found that the high concentration environment of silver nitrate solution was more advantageous for nano-Ag deposition, and the non-vacuum sintered porous surface was able to obtain a larger number of nano-Ag particles with smaller sizes. The porous Ag coating exhibited superior antibacterial properties. It was suggested that the HTZ with silver coating had clinical application, and good antibacterial properties that can improve the survival rate and service life of implants.

Silver nanoparticles with plasma-polymerized hexamethyldisiloxane coating on 3D printed substrates are non-cytotoxic and effective against respiratory pathogens.

Due to the emerging resistance of microorganisms and viruses to conventional treatments, the importance of self-disinfecting materials is highly increasing. Such materials could be silver or its nanoparticles (AgNPs), both of which have been studied for their antimicrobial effect. In this study, we compared the biological effects of AgNP coatings with and without a plasma-polymerized hexamethyldisiloxane (ppHMDSO) protective film to smooth silver or copper coatings under three ambient conditions that mimic their potential medical use (dry or wet environments and an environment simulating the human body). The coatings were deposited on 3D printed polylactic acid substrates by DC magnetron sputtering, and their surface morphology was visualized using scanning electron microscopy. Cytotoxicity of the samples was evaluated using human lung epithelial cells A549. Furthermore, antibacterial activity was determined against the Gram-negative pathogenic bacterium Pseudomonas aeruginosa PAO1 and antiviral activity was assessed using human rhinovirus species A/type 2. The obtained results showed that overcoating of AgNPs with ppHMDSO creates the material with antibacterial and antiviral activity and at the same time without a cytotoxic effect for the surrounding tissue cells. These findings suggest that the production of 3D printed substrates coated with a layer of AgNPs-ppHMDSO could have potential applications in the medical field as functional materials.

Dihydroxy Indole-free Poly(catecholamine) for Smooth Surface Coating with Amine Functionality

Dihydroxy Indole-free Poly(catecholamine) for Smooth Surface Coating with Amine Functionality

Enhanced High Power Impulse Magnetron Sputter Processes

SummaryHigh power impulse magnetron sputtering (HIPMS) has emerged as a useful approach for depositing highly dense and smooth coatings of electrically conductive materials. Recent advances in power supply technology have further enabled HIPMS through the addition of a positive kick in the pulse cycle which supplies a bias at the surface of the sputter target which expels sputter target ions and sends more charged adatoms toward the substrate. This has been demonstrated with critical materials like diamond‐like carbon and plasmonic materials. Material specific pulse magnitudes and durations can be developed to achieve new novel thin film morphologies.

A Study of Tibial Cyst Formation in Modular Stemmed Total Ankle Arthroplasty: Exploring a Possible Relationship to Smooth and Porous Coating on the Stem Segments

Vertical fixation through stemmed components has been a successful strategy in total ankle arthroplasty. Research in hip replacement surgery has demonstrated increased rates of stress shielding, aseptic loosening, thigh pain, and cystic formation around stemmed femoral implants extensively coated with porous surfaces. While some ankle prostheses have integrated porous coating technology with stemmed tibial implants, there is little to no research investigating the potential negative effects of bone bonding to the tibial stems and possible impact on tibial cyst formation. We performed a retrospective cohort study comparing the incidence of periprosthetic tibial cyst formation in smooth versus fully porous-coated stemmed tibial implants after undergoing total ankle implant arthroplasty. Radiographs were compared for postoperative rates of tibial cyst formation and bone bonding to the tibial stems. Relative risk for reoperation between the smooth and porous-coated implants was investigated. The smooth-stem group showed no incidence of tibial cyst formation nor signs of significant bone bonding to the tibial stems; however, the follow-up matched porous-coated group showed a rate of 63% of cystic formation with associated evidence of bone bonding on final radiographic follow-up (p < .01). Relative risk for reoperation was 0.74. Despite a higher incidence of tibial cyst formation in the stemmed ankle arthroplasty groups with porous coating, reoperation rates were similar. We theorize that the proximal bonding to the porous stem surface could impact the distal stems and result in the observed increase in cyst formation.

The effect of MOx (M = Zr, Ce, La, Y) additives on the electrochemical preparation of tungsten in eutectic Na2WO4–WO3 melt

In order to prepare dense and smooth tungsten coatings, a class of additives MOx (M = Zr, Ce, La, Y) were mixed into Na2WO4–WO3 molten salt. Composition and microstructure of tungsten coatings were characterized by X–ray diffraction (XRD), and scanning electron microscopy (SEM). Different MOx additives produce significant differences in the phase, micromorphology and performance of the coatings. The coatings electrodeposited in Na2WO4–WO3–CeO2 molten salt have the finest grains, resulting in the microhardness of coating surface reaches the maximum value of 643.5 HV. The thermal shock resistance in air atmosphere is related to the phase and grains size of the coatings. The electrodeposition mechanism was explored by cyclic voltammetry (CV), linear scan voltammetry (LSV), square wave voltammetry (SWV), chronoamperometry (CA) and open circuit chronopotentiometry (OCP). The results indicated that the electrodeposition of tungsten ions is W(VI) → W(IV) → W, and Zr4+ and Ce4+ ions are electroreduced in two steps, while La3+ and Y3+ are electroreduced in one step. The differences between cathodic electroreduction potential and overpotential induced by different additives were probed. What’s more, the relationship between micromorphology and performance of coatings is discussed.

Electropolymerized Poly(3,4‐ethylenedioxythiophene) Coatings on Porous Carbon Electrodes for Electrochemical Separation of Metals

AbstractElectrode‐assisted techniques are well suited for the separation of ions from solutions with reduced energy and chemical consumption. This emerging platform can benefit greatly from the convection enhanced and zero‐gap reactor designs unlocked by macroporous electrodes, but immobilizing ion‐selective layers on such complex 3D architectures is challenging. Electropolymerization of conductive polymers is proposed as a coating methodology to fabricate highly conformal coatings with electrochemically switchable ion‐exchange functionality. To demonstrate this, the synthetic parameters, resulting morphology, and ionic separation performance of poly(3,4‐ethylenedioxythiophene) (PEDOT) on commercially available carbon paper electrodes are studied. Electropolymerization of PEDOT in organic solvents results in rougher morphologies with high sensitivity to electrochemical protocols employed. When polymerized in aqueous solutions of poly(4‐styrenesulfonate) (PSS−), the resulting PEDOT/PSS blend polymer forms smooth coatings with a controllable thickness down to 0.1 µm. With appropriate voltage bias, PEDOT/PSS coated electrodes can take up and release Ni2+ in the presence of excess Na+. Increasing the coating thickness decreases the adsorption capacity due to mass transfer limitations, and the maximum adsorption capacity for Ni2+ is reached for the thinnest coatings at 228 mg g−1. Through a systematic study of PEDOT/PSS coated carbon paper, electropolymerization is identified to be a promising avenue for porous electrode functionalization.