Protective Coatings Research Articles

Polyoxometalate-Ionic Liquids for Mitigating the Effects of Iron Gall Ink Corrosion on Cellulosic Supports.

Iron gall ink (IGI), renowned for its indelibility, was the most important writing ink in the Western world from the 15th to the late 19th century. However, it is now known that IGIs induce acid-catalyzed hydrolysis and iron-catalyzed oxidation of the cellulose in historical paper documents. These mechanisms of deterioration cause significant damage to the writing support materials, including color alteration and burn-through appearance, and in the worst scenarios, physical disintegration of the supports. Minimally invasive, long-term effective conservation treatments that tackle the underlying mechanisms of IGI degradation and their corrosion effects are yet to be developed. This study introduces the deployment of hydrophobic and anticorrosive polyoxometalate-ionic liquids (POM-ILs) as colorless coatings to counteract IGI-corrosion of cellulosic supports. Model IGI-containing papers (mockups) were prepared, coated with POM-ILs, and artificially aged to assess the compatibility of POM-ILs with IGI-containing documents. Comprehensive monitoring using colorimetric and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM/EDS) analyses showed minimal interference with the aesthetic properties and morphology of the IGI mockups. In addition, polyoxometalates (POMs) with vacant metal atom sites in the cluster shell can be used to coordinate free transition metal ions. The ability of a monolacunary Keggin-type polyoxotungstate to coordinate free Fe(II) from IGI solution was demonstrated using UV-vis analysis. This led to the formation of a dimeric species, [(SiW11O39Fe)2O]K12·28H2O, which was characterized by single-crystal X-ray diffraction. Altogether, this study points to POM-ILs as promising protective coatings for effectively preserving historical IGI-written heritage.

The history and the current state of the art related to structures under stress and corrosion

The paper deals with the current state of the art arising in the design of the structures, operating under traditional mechanical loading in the aggressive environment causing their corrosion. The express goal in this case is establishing the corrosion rate dependence on the stress state of the structure and considering its durability. Thus, the use of basic mathematical models that describe the effect of corrosion rate depending on the stress state of the structure is considered. The main objective of this paper is to provide a review of useful approximations that have been suggested to deal with interaction of stress and corrosion fields. The first model that considers such a relationship is the Dolinsky model, which uses a linear dependence of the stress effect on the corrosion rate. Additionally, the Gutman model, in which the dependence of the corrosion rate on stress is expressed by an exponential law, is considered. When constructing mathematical models of structures’ corrosion wear, it is also necessary to take into account the protective coatings operation and determine the incubation period duration, which is the durability of the applied protective coatings. In this regard, the use of one of these models, which takes into account the decrease in the polymer coatings’ protective properties and a combined approach to accounting for corrosion and the anti-corrosion coatings’ protective properties are presented. Determining their reliability is an equally important aspect in the design of structures subject to corrosion. Therefore, the main theories of reliability and their practical application were considered on specific examples. A characteristic feature of the work is the coverage of issues related to the optimal design of structures operating in corrosion conditions. Two classes of problems were studied. First, determining the optimal form of structures under various types of mechanical loading and the use of the above corrosion models is considered. In the second class, the use of promising optimization models related to the solution of multi-criteria problems (using the fuzzy sets theory), as well as models with a pronounced economic bias, which allow making a cost estimate of structures failure-free operation during their lifetime, is considered. This article's novelty consists of preparing a comprehensive review of the interaction of stress and corrosion conditions. Researchers are deemed to greatly benefit from knowing the existing literature along with their strengths and weaknesses.

Manipulation of facet zincophilicity of protective coatings for long lifetime zinc anodes

Aqueous zinc-ion batteries are considered to be a promising technology for large scale energy storage deployment due to their advantages of low cost and high security. However, the zinc anodes suffer long-standing problems of uncontrollable dendrite growth and unstable interfacial chemistry that hinder their industrial applications. In this work, we manage to manipulate the facet zincophilicity of commercial titanium oxide (TiO2) by nitrogen implanting as a protective coating to realize long-term zinc plating/stripping. The nitrogen-implanting significantly increases the habitual facet zincophilicity of TiO2 layer to enable uniform and fast zinc deposition kinetics. Impressively, the as-protected Zn anode could be operated for a long lifespan of 2400 h accompanying with a high cumulative capacity of 4.1 Ah cm-2 and a stable Coulombic efficiency of 99.53 % over 900 cycles. This work will shed new insight on the importance of manipulating the facet zincophicility of protective coatings for dendrite-free metal anodes beyond zinc chemistry.

Bilayer period and ratio dependent structure and mechanical properties of TiN/MoN superlattices

Transition metal nitrides are widely used in the hard materials and protective coatings industry, but are limited by their low fracture toughness. Encouraged by previous studies on remarkable simultaneous improvements in strength and ductility through superlattice (SL) architectures, various TiN/MoN SL thin films were developed on MgO (100) substrates. By varying their bilayer periods (Λ) between 2 and 23 nm with bilayer ratios (Γ = ℓMoN:ℓTiN) of 0.5, 1, 2, and 2.7, their individual effects on structure and mechanical properties can be revealed. All SLs—independent of Λ, Γ, and nitrogen-to-metal (N/Me) ratio (within the analysed variations)—exhibit a rocksalt structure with high-order satellite peaks in X-ray diffraction. While the SLs with Γ = 2 have the lowest hardness (H)—presumably due to their overall lowest N/Me ratio—the SLs with Γ = 2.7 are the hardest with a neat superlattice effect. The SLs with Γ = 1 and 2.7 have a comparable superlattice effect on fracture toughness (KIC), peaking at Λ = 9.9 and 9.3 nm, respectively. Of all the SLs investigated, those with Γ = 1 provide the best blend of mechanical properties and dry sliding coefficient of friction (µ), such as H = 34.8±1.6 GPa, KIC = 4.1±0.2 MPa√m, and µ = 0.27 when Λ = 9.9 nm. Deepening current understanding of superlattice effects in general—particularly the influence of bilayer periods and ratios—in relation to the nitrogen supply and heterogeneous microstructures, our study accelerates the design of nanolayered coatings with desired structure-property combinations.

The Influence of Variable Plasma Welding Parameters on Weld Geometry, Dilution Factor, and Microhardness

Weld surfacing is the process of applying a layer of metal to the surface of metal objects by simultaneously melting the substrate. As a result of this process, the metal content of the padding weld can be as high as several tens of percents. It is a method used to regenerate machine parts and improve the properties of the surface layer, increasing its resistance to abrasion, corrosion, erosion, and cavitation. It also supports the repair and creation of permanent protective coatings in the engineering, automotive, energy, and aerospace industries. This makes it possible to repair damaged parts instead of completely replacing them, saving time and production costs. Plasma surfacing technology is used for components that require high hardness and corrosion resistance under various environmental conditions. Plasma wire surfacing is not sufficiently presented and described in the current literature, which creates problems in determining the appropriate process parameters. The influence of variable plasma surfacing parameters on steel C45 significantly affects surfacing weld geometry, the dilution factor, and microhardness. Higher currents can increase the dilution factor, integrating more base metal into the weld pool, which may alter the chemical composition and mechanical properties of the weld. Variations in surfacing speed and heat input also affect the microhardness of the surfaced joint, with higher heat inputs potentially leading to softer welds due to slower cooling rates. Optimizing these parameters is essential to achieving desired surfacing weld characteristics and ensuring the structural integrity of C45 steel joints. This paper presents the influence of varying plasma surfacing parameters on the surfacing geometry, the dilution factor, and microhardness. The tests were carried out on a Panasonic TM-1400 GIII automated surfacing machine with CastoMag 45554S solid wire as the filler material. Flat bars of C45 steel were prepared, and then the variable parameters of the surfacing process were developed. Tests were carried out to determine the dilution factor, followed by microhardness measurements. The results showed a significant dependence of the effect of the parameters on the surfacing geometry and the dilution factor.

Analysis, Assessment, and Mitigation of Stress Corrosion Cracking in Austenitic Stainless Steels in the Oil and Gas Sector: A Review

This comprehensive review examines the phenomena of stress corrosion cracking (SCC) and chloride-induced stress corrosion cracking (Cl-SCC) in materials commonly used in the oil and gas industry, with a focus on austenitic stainless steels. The study reveals that SCC initiation can occur at temperatures as low as 20 °C, while Cl-SCC propagation rates significantly increase above 60 °C, reaching up to 0.1 mm/day in environments with high chloride concentrations. Experimental methods such as Slow Strain Rate Tests (SSRTs), Small Punch Tests (SPTs), and Constant-Load Tests (CLTs) were employed to quantify the impacts of temperature, chloride concentration, and pH on SCC susceptibility. The results highlight the critical role of these factors in determining the susceptibility of materials to SCC. The review emphasizes the importance of implementing various mitigation strategies to prevent SCC, including the use of corrosion-resistant alloys, protective coatings, cathodic protection, and corrosion inhibitors. Additionally, regular monitoring using advanced sensor technologies capable of detecting early signs of SCC is crucial for preventing the onset of SCC. The study concludes with practical recommendations for enhancing infrastructure resilience through meticulous material selection, comprehensive environmental monitoring, and proactive maintenance strategies, aimed at safeguarding operational integrity and ensuring environmental compliance. The review underscores the significance of considering the interplay between mechanical stresses and corrosive environments in the selection and application of materials in the oil and gas industry. Low pH levels and high temperatures facilitate the rapid progression of SCC, with experimental results indicating that stainless steel forms passive films with more defects under these conditions, reducing corrosion resistance. This interplay highlights the need for a comprehensive understanding of the complex interactions between materials, environments, and mechanical stresses to ensure the long-term integrity of critical infrastructure.

Development of Heat-Resistant Coatings for Protection of Niobium and Tantalum from the Oxidizing Effect of Air at Temperatures 1700–1900°C

Development of Heat-Resistant Coatings for Protection of Niobium and Tantalum from the Oxidizing Effect of Air at Temperatures 1700–1900°C

Static and dynamic friction and wear of cobalt-based coatings at elevated temperatures

Advanced ultra-supercritical power plants, in which steam temperatures exceed 700 °C, demand the development of protective coatings, particularly for valves governing the steam flow where sealing surfaces are subjected to high static tribological solicitations. In this context, we systematically investigated the friction (static and dynamic) and wear of two cobalt-based coatings and one nickel-based substrate. Results indicate that oxidation kinetics exhibits a double-edged sword effect in terms of tribological properties at elevated temperatures. Fast oxidation kinetics promotes the sintering of oxides, generating a smoother oxide tribofilm and lowering the dynamic coefficient of friction (COF). However, this can also significantly increase the static COF over loading time due to welding/sintering of oxidized asperities, leading to increased torque requirements for valve operation.

Bionic repair protective coatings with high toughness and bond strength based on anionic waterborne polyurethane-modified cement

Protection and repair of surface cracks play pivotal roles in enhancing their effective service life. Inspired by the bionic shell principle, an anionic waterborne polyurethane (WPU) was designed. The Synthetic WPU was applied to sulphoaluminate (SAC) and ordinary Portland (OPC) cements to prepare composite coatings. The results showed that with the increase in polymer-to-cement ratio (P/C), attributable to the electrostatic adsorption and complexation of R-COO-, the content of CH, AH3 and AFm increased, while the content of AFt decreased due to the inhibitory effect of WPU on hydration reactions. The molecular dynamics model indicated that the oxygen atoms in WPU can not only form ion pairs with Ca2+ in AFt but also form strong hydrogen bonds with the H in the hydroxyl group of AFt and the H in water molecules. Hence, for P/C exceeding 10 %, combined with Flory-Huggins theory, a continuous interpenetration polymer network (IPN) comprising multiphase composites was successfully demonstrated, bolstered by the macromolecular structure composed of —OH, —COOH, Ca2+ and Al3+ serving as a bridge. The network was more pronounced in coatings with SAC than in those with OPC due to synergistic effects caused by rapid hydration reactions. Due to the presence of IPN and the Si-O-Si bonds caused by the hydrolysis condensation reaction of silane coupling agent, the tensile and bond strengths exhibited an upward trend with increasing P/C, surging by up to 326 % and 180 %, respectively. The value reached 6.81 MPa and 2.2 MPa. And the addition of WPU enhanced crack resistance.

Comprehensive Characterization of Porous Transport Electrodes with SEM, XPS, and Tof-SIMS

Advancements towards more efficient design and manufacturability of polymer electrolyte membrane electrolyzers include recent efforts to better integrate the porous transport layer (PTL) and adjacent anodic catalyst layer (CL), forming the porous transport electrode (PTE). It is well known that characterizations of the PTL alone, especially when combined with a protective coating, present numerous challenges. The PTE structure is even more complex, and it is difficult to comprehensively characterize all components and interfaces. In prior work, we established Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) as a characterization technique for the PTLs coated with protective coatings. This work demonstrates ToF-SIMS as a powerful technique for the characterization of PTLs integrated with CLs. A series of sintered Ti PTLs were first coated with protective Pt coatings and then coated with various IrOx and IrRuOx catalysts via electrodeposition. Prepared PTE samples ranged in catalyst loadings and catalyst composition. Selected samples were also subjected to annealing post-treatments to further modify catalyst composition. X-ray photoelectron spectroscopy (XPS) was conducted to identify surface chemical speciation and states of the catalysts. ToF-SIMS analysis was conducted using Cs in both positive and negative modes to identify chemical species, including Ir, Ru, and their oxides as a function of catalyst layer depth. These two methods were complemented by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM- EDS) analysis to evaluate morphology and distribution of catalysts. This comprehensive physical and chemical characterization of the PTEs provides insights that are useful for the characterization of as produced, modified, and degraded PTE samples.

(Invited) The U.S. Department of Energy’s Hydrogen Consortium for Advanced Water Splitting Materials

The goals of the Hydrogen and Fuel Cell Technologies Office (HFTO) support those of the Biden Administration to build a clean and equitable energy economy and address the climate crisis through development and deployment of hydrogen technologies to the benefit of all Americans. HFTO is dedicated to meeting the goals of DOE’s Hydrogen Shot,1 which targets affordable clean hydrogen production at $1/kg within the decade, and the H2@Scale Initiative,2 which aims to advance affordable hydrogen to enable decarbonization and revenue opportunities across multiple sectors.HFTO’s HydroGEN consortium (https://www.h2awsm.org) for advanced water splitting (AWS) materials, part of the DOE’s Energy Materials Network (EMN), focuses on multiple clean hydrogen production pathways, including several relevant to renewable fuels via artificial photosynthesis. Since the consortium’s establishment in 2016, HydroGEN researchers have made significant progress in the areas of low and high temperature electrolysis, as well as solar thermochemical (STCH), and most relevant here, photoelectrochemical (PEC) hydrogen production pathways. The HydroGEN consortium facilitates collaborations between national laboratories, academia, and industry, bringing together world-class technical expertise with state-of-the-art facilities made available to project partners. HydroGEN offers an extensive collection of materials research capabilities for addressing R&D challenges. Project participants can choose from over 40 unique capability nodes. Each capability node is comprised of a combination of a tool, technique, and expertise that is unique to the national laboratory system.HydroGEN has supported over 30 competitively selected R&D projects with industry and academic partners by providing streamlined access to national lab resources and expertise. The consortium is also involved in fostering cross-cutting activities to advance material performance and durability through community engagement and protocol development and initiating critical laboratory-led efforts to address specific R&D gaps in the AWS portfolio.A new cohort of solar fuels focused projects were recently selected through the Funding Opportunity Announcement (FOA) Number: DE-FOA-0002792 with additional funding in this area expected in the future. A total of 11 new projects were selected, six in PEC and five in STCH, to work with the HydroGEN consortium towards advancing solar fuels production technology. Projects from both technology pathways must define materials metrics and targets for meeting the interim hydrogen cost target of $2/kg-H2 with extrapolation to additional requirements for meeting $1/kg-H2.Selected PEC projects focused on the development of materials or material systems for efficient and durable PEC water-splitting with a focus on innovations in bandgap and bandgap alignment, functional interfaces, stable surface catalysis, and protective coatings. A successful PEC photoelectrode project will need to achieve 15% STH efficiency for the entirety of operation exceeding 1,000 hours, with proposed pathways for achieving efficiencies up to 25% and durability up to 10,000 hours. Further, PEC systems will be required to demonstrate hydrogen production at a rate of 0.1 g/h for diurnal operation over two weeks.Selected STCH projects focused on accelerating discovery, development, and demonstration of alternative redox materials for a two-step STCH process and addressing projected costs and materials challenges associated with the required operating temperatures. Successful STCH projects will need to include a demonstration of the STCH process using sunlight or simulated sunlight. STCH systems must demonstrate hydrogen production at a rate of 1 g/h for diurnal operation over two weeks.For the first time, in line with the Justice40 Initiative,3 applicants were required to submit DEIA (diversity equity, inclusion, and accessibility) plans. Objectives from these plans were incorporated into the project objectives with specific goals identified for each year.Despite the progress, there is still significant ground to be covered through water splitting materials R&D. With the support of HydroGEN, these selected projects will help to address remaining challenges and enable low-cost and large-scale hydrogen production. An overview of consortium and project goals and objectives will be discussed. Hydrogen Shot | Department of EnergyH2@Scale | Department of Energy,The Justice40 initiative, created by Executive Order 14008, establishes a goal that 40% of the overall benefits of certain federal investments flow to disadvantaged communities. Figure 1

Elucidating Photoelectrochemical Corrosion at III-V Semiconductor/Electrolyte Interfaces Using Electrochemical Impedance Spectroscopy

As the energy transition matures and society looks to mitigate the negative impact of hard-to-decarbonize sectors, the production of green sustainable fuels becomes increasingly important. Photoelectrochemical (PEC) water splitting offers a path towards direct solar-to-hydrogen conversion through its integrated all-in-one design. However, practical device efficiency goals (>20%) necessitate the use of high efficiency III-V semiconductor materials that are unstable in aqueous electrolyte. The rapid degradation of these materials in aqueous media limits their utility to short-lifetime lab-scale devices. Some of the highest efficiency PEC devices to date employ GaInP in the photocathode to drive the hydrogen evolution reaction despite its limited stability. Protective coatings and catalyst layers improve the stability of GaInP photocathodes, but much remains unknown about the exact degradation mechanisms. Here, we use electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis to gain insight into the processes underpinning the degradation of GaInP-based photocathodes in PEC devices.The EIS technique can monitor charge transfer resistance investigation in PEC devices, but it has had suspect utility for III-V photocathode degradation studies due to rapid material corrosion and slow measurement times. However, the emerging technique of rapid, hybrid EIS measurements provides immense value as a non-destructive and frequency-dependent probe which distinguishes physical processes by their time constants with high resolution. The DRT analysis deconvolutes features of an impedance spectrum without requiring a priori knowledge of the physical processes that contribute to the observed response and ensures unbiased assessment of the data. In this work, we test the effects of Pt nanoparticulate catalyst loading and illumination level on the device impedance and correlate the results to semiconductor corrosion. By varying the cell operating conditions, we perform a robust assignment of the impedance response to physical phenomena. EIS corrosion studies can be complemented by chemical (ICP-MS) and microscopic (optical interferometry) techniques to enhance their correlation. The impedance and material dissolution data provide a better understanding of III-V semiconductor photocorrosion mechanisms.

Scanning Electron Microscopy Energy-Dispersive X-Ray Spectroscopy Analysis of Catalyst-Coated Porous Transport Layers

The transition of the United States energy infrastructure towards hydrogen energy involves the optimization of proton exchange membrane water electrolyzers (PEMWEs) for reliable hydrogen generation. PEMWE device typically consists of titanium porous transport layer (PTL) and an iridium-based anode catalyst layer. Several directions are being pursued to improve performance and to reduce the costs. To mitigate naturally occurring titanium passivation, protective coatings, typically platinum or other platinum-group metals (PGMs) are commonly applied to the PTLs. The drive to decrease the cost and the use of scarce materials has led to the development of catalyst layers with lower catalyst loadings. Reducing fabrication time and cost as well as increasing efficiency of the anode has led to the investigation of direct application of the iridium-based catalyst onto the Pt-coated Ti PTL. This motivated our investigation of porous-transport electrodes (PTEs) prepared with a variety of deposition methods, using different ink formulations, and targeting different catalyst loadings. There is need to develop a characterization approach that can be used to assess and compare quality of coatings across large parameter space or to monitor quality during production.Several sets of PTEs samples consisting of a titanium porous layer, platinum protective coating and iridium-based catalyst layer were prepared using a wide range of catalyst layer coating methods and parameters, including spray coating, gravure, airbrush and electrodeposition. All samples were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) to analyze the elemental composition and assess the distribution of elements of interest (Ti, Pt, and Ir). First, the atomic% of each element was used to calculate elemental ratios for quantitative assessment of the amount of deposited catalyst. However, it is crucial to recognize the limitations of relying solely on this information for assessing catalyst coating since it doesn’t account for heterogeneity of the coatings. Although elemental maps provide valuable insights into spatial distribution, they alone do not offer a complete picture. To better understand the catalyst coating distribution, each individual EDS elemental map was used to calculate the surface area, which served as a measure of PTL area covered by the catalyst. Further, surface area ratios (Pt/Ir) were calculated to determine variations in surface coverage. This poster will highlight differences between fabricated samples and will demonstrate that together, at% and surface area ratio values allow for a comprehensive quantitative assessment of the composition and distribution of catalyst surfaces that were produced through a wide range of fabrication variables. The implementation of proper characterization of these PTEs can help aid future decisions on which parameters should be used moving forward. This approach can also be used for quality control, enabling quick screening of commercially produced samples.

Functional Protective Coatings Based on Polysaccharides and Single-Ion Conducting Polymers for Li Metal Batteries

This work aims to study a protective coating based on cellulose and P(LiMTFSI) single-ion conductor polymer and its effects on Li metal anode stability and reversibility. The strategy used involves the physical mixture of the aforementioned polymers to enhance the electrochemical performance through Li-ion flux homogenization at the Li metal surface, promoting the formation of a dense plating. Single-ion conducting polymers (SICPs) are incorporated due to their beneficial effects such as enhancing lithium ion transport, boosting lithium transference number (𝑡𝐿𝑖 +), and diminishing the effects of concentration polarization, avoiding the initiation and propagation of high surface area lithium (HSAL). Furthermore, a quasi-solid-state Li metal battery system is explored which brings additional advantages over the typically used organic electrolytes. In this sense, during this study we propose using the protective coating based on cellulose and P(LiMTFSI) to tailor an adequate interphase that creates a good adhesion, by taking advantage of the polymers film formation ability, and therefore improving the lifespan and safety of the battery. The coating effectiveness is tested by casting the solution on an activated lithium surface and performing lithium platting/stripping protocols in Li/Li and Li/Cu pouch cells under selected current densities (0.5, 1 and 2 mA/cm2). Complementary electrochemical tests are carried out to study transport, conductivity parameters, and its performance in full cell coupled with LFP cathode. Finally, we analyze the correlation with the physicochemical properties and electrochemical performed based on spectroscopic techniques and microscopy to study the most relevant parameters influencing a high Coulombic Efficiency. Acknowledgments This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska – Curie Grant Agreement N° 945357, and co-financing from the Slovenian Research and Innovation Agency (ARIS) is fully acknowledged.

Application of Hipims Coatings to Enhance the Durability and Performance of Structural Components of PEM Electrolyzer Anodes

Porous transport layers (PTL) and bipolar plates (BPP) are structural elements that transport water, gases, electrons as well as heat within the electrolysis cells. On the anode side, the state-of-the-art material for BPP and PTL is titanium due its higher corrosion resistance under the operating conditions of electrolysis (high electrochemical potential, acidic and oxidizing environment) compared to other materials [1]. However, titanium components tend to form an oxide layer that rises the interfacial contact resistance (ICR) and leads to a poor performance since metal oxides are semiconductors or insulators. This issue is usually addressed by applying precious metal coatings, such as platinum or gold. In this work, we present the potential of high power sputtering techniques (HiPIMS) to manufacture ultra-low loading Pt coatings (<20 nm) with good homogeneity and high performance at an industrial scale. The influence of HiPIMS parameters on coating-substrate interface, as well as the coating properties have been evaluated. SEM, AFM and HRTEM microscopy have been used to evaluate the coating thickness and morphology. XRD analysis has been carried out to evaluate the influence of the HiPIMS parameters on the growth mode of Pt coatings, tailoring the coating texture from [200] to [111]. HiPIMS technique also provide enhanced density compared with other coating techniques due to the higher ionization achieved in the plasma [2]. The deposition of denser and defect-free coatings by HiPIMS enables the application of stainless steel components. HiPIMS prevents the formation of columnar structures and reduces oxygen diffusion. In this work, Nb- and Ti-based protective coatings have been deposited by HiPIMS on stainless steel 316L. A comparative between coated Ti Gr2 and SS316L has been set, showing the potential to reduce costs in the next generation of PEMWE structural components.

Mechanisms of Ni Dissolution from Ni-Rich Cathode in Li-Ion Batteries

Nickel-rich cathodes are the most promising candidates for realizing high-energy-density Li-ion batteries because of the high theoretical capacity. However, their structural instability detrimentally affects the battery performance during cell cycling, which restricts its large-scale commercial application. One impediment to their commercialization is the dissolution of transition metal ions, which can diffuse to the anode, corrupt the solid electrolyte interphase (SEI) films protecting the anode, and accelerate battery capacity fading. Here, we use ab initio molecular dynamics (AIMD) simulations to investigate the mechanism of Ni dissolution from the LiNiO2 cathode surfaces. Our calculations identified that the proton-transfer reactions between electrolytes and cathode surfaces cause the reduction of surface Ni atoms from Ni3+ to Ni2+, which weakened the Ni-O bonding. As the LiNiO2 cathode surface gets delithiated, more surface protonation reactions were observed, and the reduced Ni atoms were found to be dissolved from the cathode surfaces in the form of NiOOH, which is the fundamental origin of phase transition of LiNiO2 cathode from a layered to electrochemically inactive spinel-like structure, accompanied by H2O elimination and O2 evolution. Besides, we also studied the impact of various factors on Ni dissolution rates such as the presence of fluorine attachment and the coordination of Ni atoms and electrolyte species. These findings help inform future design of protective coatings, electrolytes, additives, and interfaces for Ni-rich cathode.

Designing a smart polyurethane anti-corrosion coating loaded with APTES/IMZ modified halloysite nanotubes

Protective coatings are efficient for preventing corrosion, but they may not be sufficient for applications in aggressive and extreme environments, such as in coastal areas that could be subjected to corrosion. Inhibitors can suppress the corrosion rate significantly, but direct addition to the coating is ineffective because the inhibitor is easily soluble in water and can reduce the effectiveness of the barrier properties of the coating. Encapsulating the inhibitor into a nanocontainer is a promising alternative that may lead to a self-healing coating technology. Halloysite nanotubes (HNT) have been successfully reported for their application in smart coatings, and they exhibit superior aerodynamic and hydrodynamic properties and better process ability than spherical capsules for the same amount of load. Therefore, nanotubes are appropriate candidates to be used as nanocontainers for inhibitors over smart coating applications. This research discusses the design of a polyurethane coating loaded with modified halloysite nanotubes for corrosion protection of steel. Halloysite nanotubes were first functionalized using aminopropyltriethoxysilane (APTES) to improve their dispersion in the polyurethane matrix. The modified halloysite nanotubes were then loaded with the corrosion inhibitor 2-mercaptobenzimidazole (IMZ). The loaded nanotubes were incorporated into polyurethane coatings. Various characterization techniques were used to confirm the successful modification and loading of the halloysite nanotubes. The distribution of particles in the matrix was investigated by Transmission Electron Microscopy (TEM) test. The modified nanotubes showed better dispersion in the polyurethane coating, which improved the coating's barrier properties and corrosion resistance. Electrochemical Impedance Spectroscopy (EIS) and salt spray tests showed that the polyurethane coating containing the loaded and modified halloysite nanotubes exhibited the highest resistance to corrosion. The adhesion strength of the coating was also improved after immersion in a saline solution, particularly for the coating with modified and loaded halloysite nanotubes. In summary, the functionalization and loading of halloysite nanotubes improved their dispersion in the polyurethane coating, which in turn enhanced the coating's barrier properties, corrosion resistance, and adhesion strength, making it a promising approach for designing smart corrosion protective coatings.

Harnessing Polar Interactions Tunes the Stability of Ultrathin Polymer Solution Films.

The stability of ultrathin (<100 nm) polymer films is essential in applications like protective coatings. On the contrary, their instability may actually be desirable for the emergence of self-assembled nanoscale patterns utilized in the fabrication of functional devices. Polymer solution films exhibit two distinct kinds of instabilities, viz., dewetting (long-wave) and decomposition (short-wave). Dewetting refers to the rupture of the continuous film to form isolated domains, while decomposition leads to phase separation within the polymer solution. The focus of this work is on leveraging polar interactions between the solute and solvent molecules to tune the stability of the film. A gradient dynamics-based thin film model is developed to investigate pattern formation in a thin polar polymer solution film. The Flory-Huggins theory is suitably modified by introducing a polar interaction parameter that depends upon the concentration of the polymer and the dipole moments of monomer (μ1) and solvent molecules (μ0). A linear stability analysis is performed to determine the characteristic length scale and growth rate of the instabilities. It is shown that the range of concentration space for the occurrence of the decomposition mode is directly affected by the Flory interaction parameter (χ0), μ0, and μ1, thereby serving as control parameters to tune the width of the concentration range. It is further shown that ignoring polar interactions may lead to incorrect predictions of the instability mode, including a complete loss of the decomposition mode. In addition, the long-wave dewetting length scale is found to decrease due to bulk dipolar interactions at higher polymer concentrations. Finally, numerical simulations are carried out to track the nonlinear evolution of the interface and concentration field for both the decomposition and dewetting modes of instability.

Suppressing hydrogen evolution and promoting dendrite free zinc deposition by fluorinated triazine framework towards robust aqueous zinc ion batteries

Aqueous zinc-ion batteries (AZIBs) have become a research hotspot, but the inevitable zinc dendrites and parasitic reactions in the zinc anode seriously hinder their further development. In this study, three covalent triazine frameworks (DCPY-CTF, CTF-1 and FCTF) have been synthesized and used as artificial protective coatings, in which the fluorinated triazine framework (FCTF) increases the zinc-philic site, thus better promoting dendritic free zinc deposition and inhibiting hydrogen evolution reactions. Excitingly, both experimental results and theoretical calculations indicate that the FCTF interface adjusts the deposition of Zn2+ along the (002) plane, effectively alleviating the formation of zinc dendrites. As expected, Zn@FCTF symmetric cells exhibit cycling stability of over 4000 h (0.25 mA cm−2), meanwhile Zn@FCTF//NHVO full cells provide a high specific capacity of 280 mAh/g at 1.0 A/g, which are superior to those of bare Zn anode. This work provides new insights for suppressing hydrogen evolution and promoting dendrite-free zinc deposition to construct highly stable and reversible AZIBs.

Corrosion protective properties on 2024‐T3 of chitosan‐modified montmorillonite epoxy coatings based on Ce3+ loading

Abstract2024 aluminum alloy has high strength, processing performance, and good damage tolerance performance, but it is prone to intergranular corrosion and pitting. Therefore, the development of corrosion protective coatings is essential for the aluminum alloy. In this paper, cerium ion (Ce3+) was doped into chitosan‐modified montmorillonite (Ce‐CS‐MMT) by ion exchange method, and the corrosion protective performance of Ce‐CS‐MMT epoxy coating (Ce‐CS‐MMT/EP) was investigated. The electrochemical analysis of aluminum alloy in cerium‐containing solution showed the corrosion inhibition efficiency reached 95.52%. The result indicates the corrosion inhibition effect of cerium‐containing solution was better than pure NaCl solution and MMT solution. The corrosion study of the coating illustrates that the protection rate of Ce‐CS‐MMT/EP reached 95.82%, which was higher than that 91.83% of Ce‐MMT/EP. The result indicates the resistance of charge transfer was greater and the better shielding effect for electrolyte corrosion ions than MMT and Ce‐MMT epoxy coatings, and the corrosion protective performance was excellent.