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Inorganic, organic, and metallic coatings have received much attention due to their great protection applications in oil and gas industries and their development through finding eco-friendly materials for the coatings. Their unique structure, low cost, and facile synthesis are some of the few properties of graphitic carbon nitride (g-C3N4) materials that make them useful in a number of applications. Moreover, g-C3N4 offers exceptional chemical and thermal stability and a high specific surface area, and it is well known for its outstanding biocompatibility and biological activity. Numerous investigations have reported various types of C3N4-incorporated coatings that have enhanced corrosion, wear, and mechanical resistance properties. This review highlights the new applications of g-C3N4 (standalone, in an alloy, or composite) as a coating in the wear and corrosion protection fields. Furthermore, a strong focus on the structure, unique properties, and preparation technique of g-C3N4 are summarized, especially in metallic coatings, which is a highly novel trend. Lastly, various important issues based on current research are proposed for future prospective work that should be further studied in this attractive research topic. [ABSTRACT FROM AUTHOR]

304 stainless steel (304SS) powder and novel Mo-cladded 304SS (304SS-Mo) powder were used as feedstocks to prepare metallic coatings with different inter-splat bonding qualities. Wear test was conducted to examine the dependence of wear behavior on the inter-splat bonding quality. The results showed that poor inter-splat bonding leads to much lower wear resistance in conventional 304SS coating relative to that of 304SS bulk, especially at high loading conditions (>75 N), where the wear rate increased to 5.53 × 10−3 mm3/(m⋅N) by 3.5 times higher than that at low-load range. However, the novel 304SS-Mo coating with metallurgical inter-splat bonding and minimized oxide inclusions exhibited a low wear rate comparable to that of 304SS bulk. Failure analysis of worn samples suggests that splat delamination contributes to low wear resistance of the 304SS coating; conversely, the absence of splat delamination results in higher wear resistance of the 304SS-Mo coating. Using Mo-cladded powders, significantly enhanced inter-splat bonding enables the use of plasma-sprayed metallic coating under high-load wear conditions. The strong dependence of wear resistance on the load in conventional coating implies that evaluation of wear performance of thermally sprayed metallic coating should consider both the wear rate and critical load. [ABSTRACT FROM AUTHOR]

Bonded permanent NdFeB magnets are useful in numerous applications, including electric vehicles, and the demand is steadily increasing. A major drawback is corrosion due to inadequate wetting of the magnetic particles by liquid polymers such as polyphenylene sulfide or polyamide. Recently reported methods for corrosion inhibition are summarized, and their applicability is critically evaluated. The phosphorylation of magnetic particles inhibits corrosion but does not enable appropriate properties in harsh environments. The same applies to metallic coatings, which usually contain aluminum and zinc. Advanced epoxy adhesives are a promising solution, although some authors have reported inadequate corrosion resistance. The application of composite coatings seems like an appropriate solution, but the exact mechanisms are yet to be studied. [ABSTRACT FROM AUTHOR]

Historical heritage pieces allow a better comprehension of the characteristics of different civilizations over time. The characterization of such pieces is of paramount importance for their preservation. Energy‐dispersive X‐ray fluorescence (EDXRF) is recommended for this application, mostly because it is non‐destructive and the equipment is portable. However, one of its limitations is the difficulty in separating the signal from the substrate and the coating of multilayered samples, as it does not provide depth resolution. This project investigates the application of EDXRF in the characterization of metallic coatings, in the context of historical heritage. The elemental concentration of electrodeposited Ni coatings onto carbon steel substrates was obtained from EDXRF analyses. The relationship between the layer thickness and the variation of the Kα/Kβ intensity ratio of nickel peaks was exploited and the thicknesses of the coatings were estimated through EDXRF measurements. For comparison, particle‐induced x‐ray emission spectroscopy and scanning electron microscopy of the cross‐section were employed, providing a depth profile of the coatings. The estimated thicknesses from EDXRF analysis were comparable to those observed in the microscopy images for thinner films (up to 8 μm). On the other hand, for thicker films, the thicknesses were underestimated, due to the technique's depth limit and matrix effects, as secondary absorption. Despite these limitations, EDXRF remains valuable for evaluating cultural heritage pieces, often providing sufficient information to address authenticity concerns or to guide restoration processes. A case study was also performed to apply the methodology discussed on historical metallic pieces. [ABSTRACT FROM AUTHOR]

Protective coatings are typically applied to enhance their resistance to corrosion. There is considerable research on the corrosion resistance of coated casings. However, few research studies have focused on the erosion resistance on coated casings. In this work, the erosion resistance of resin- and metallic-coated casings in liquid–solid two-phase fluids were investigated using a self-made erosion facility. The results show that the resin coating tends to peel off the material base in the form of brittle spalling or coating bulge in the high-speed sand-carrying liquid. Both resin and metallic coatings were broken through within 20 min in a liquid–solid two-phase flow environment. Compared to resin coatings, metallic coatings exhibit weaker erosion resistance in similar liquid–solid flow. Through the analysis of experimental results and fitted curves, empirical constants for materials and sand content influencing factors were determined using non-dimensional processing. The erosion prediction model of metallic coatings and resin coatings was established based on the ECRC/Zhang model with the change in flow rate, angle, and sand content. This research contributes to a better understanding of the erosion resistance performance of casings used in oil and gas fields, thereby contributing to potential improvements in their production. [ABSTRACT FROM AUTHOR]

Our investigations show that electrochemical corrosion of copper is faster than electrochemical corrosion of aluminium at temperatures below 180°C and electric current density 3,000 A/m2 (or 30 A/dm2=3 mA/mm2). We have obtained that aluminium anodes (cylindrical or spherical) dissolve into concentrated NaCl solution during electrolysis more rapidly with temperature increasing while copper anodes (cylindrical or spherical) dissolve more slowly with temperature increasing from room temperature to temperature 180°C. Electric current value also increases with temperature increasing. Really, such result is unexpected. General quantity of the H+ and Cl- ions decreases during electrolysis at all temperatures since the H2 and Cl2 gases are formed near electrodes. It decreases electric current value on 1.3%. General quantity of the Cu+ and Cu2+ ions decreases with temperature increasing too. We guess that one reason only should be for electric current value increasing: average charge of copper ions increases from +1 at room temperature to +1.5 at 100°C and to +2 at 180°C while charge of aluminium ions remains the same +3. Corresponding mathematical model is proposed for the analysis, and literature experimental data are used too.

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. [ABSTRACT FROM AUTHOR]

Nickel-based coatings are well known for their good corrosion resistance performance. However, these materials suffer from inferior mechanical properties that limit their wider application. This work investigates the synthesis, and performs an exhaustive characterization, of Ni–P–B4C nanocomposite coatings developed through conventional electrodeposition using a modified Watts bath. The study examines the effect of an increase in the concentration of boron carbide nanoparticles (BCNPs) on the structural, morphological, topographical, mechanical and electrochemical properties of the nanocomposite coating. Vickers microhardness tester and nanoindentation technique were utilized to elucidate the role of BCNPs in modifying the mechanical response of nanocomposite coatings. Furthermore, corrosion resistance of the nanocomposite coatings was investigated through d.c potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Comparison of the properties of the developed coatings revealed the remarkable improvement in the properties of Ni–P–B4C nanocomposite coatings when compared to the bare mild steel substrate and the Ni–P coatings. The enhanced corrosion resistance and superior mechanical properties of Ni–P–B4C nanocomposite coatings make them attractive for many industries. Based upon the experimental findings, a possible mechanism for the synthesis and improved corrosion resistance of Ni–P–B4C nanocomposite coatings was also proposed.

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.

Metallic additive manufacturing is expeditiously gaining attention in advanced industries for manufacturing intricate structures for customized applications. However, the inadequate surface quality has inspired the inception of metallic coatings through additive manufacturing methods. This work presents a brief review of the different genres of metallic coatings adapted by industries through additive manufacturing technologies. The methodologies are classified according to the type of allied energies used in the process, such as direct energy deposition, binder jetting, powder bed fusion, hot spray coatings, sheet lamination, etc. Each method is described in detail and supported by relevant literature. The paper also includes the needs, applications, and challenges involved in each process. [ABSTRACT FROM AUTHOR]

This work reports yarn pull-out studies of commercially available Kevlar® KM2+ individual yarns coated with metallic layers (copper, aluminum, aluminum nitride and silver) via a directed vapor deposition process. The uncoated control and metal-coated Kevlar® yarns are hand-woven into fabric swatches for quasi-static pull-out experiments. To perform these experiments, a yarn pull-out fixture is custom-designed and fabricated to apply transverse pre-tension to the fabric. Three levels of transverse pre-tensions are studied at 100 N, 200 N, and 400 N. The results showed that both peak pull-out force and energy absorption during the pull-out process increase with increase in transverse pre-tension. All the metal-coated groups showed an approximately 200% increase in peak pull-out force and a 20% reduction in tenacity compared to uncoated control. Furthermore, all the metal-coated groups showed an increase in energy absorption, with aluminum-coated yarns showing the highest increase of 230% compared to control. These results suggest enhanced frictional interactions during yarn pull-out in metal-coated yarns compared to uncoated control as evidenced by the surface roughness profile of individual fibers and inter-yarn frictional calculations. [ABSTRACT FROM AUTHOR]

Thermal spray is one of the most used techniques to produce coatings on structural materials. Such coatings are used as protection against high temperatures, corrosion, erosion and wear. The combined action of high pressures, temperatures and spraying conditions give rise to non-uniform residual stresses. The latter plays an important role in coating design and process parameters optimization. The present work highlights the influence of coatings thickness on the evolution of residual stresses in layered materials. Therefore, thick stainless steel coatings (ASTM 301) of different thicknesses are manufactured by wire arc spraying on aluminium alloy substrates (ASTM 2017A). For a better bond strength, a Ni–Al bond coat is first deposited. Furthermore, a numerically supported hole drilling strain gage method for residual stress field evaluation is proposed. Required calibration coefficients, for the strain–stress transformation formalism based on the integral method, are computed through finite element calculations using Abaqus software. The results indicate that the maximum residual stresses, for all thicknesses, are tensile and range from 140 to 275 MPa. The bond coat does not seem to affect the stress field. Also, it was found that the mean equivalent Von-Mises stress decreases with increasing coating thickness; hence reducing the interfacial adhesion energy of the sprayed materials. [ABSTRACT FROM AUTHOR]

A detailed microstructural and electrochemical analysis of electroless nickel phosphorous (NiP) coatings with P contents of 13.2 ± 1.2 wt%, 12.9 ± 0.7 wt%, and 8.3 ± 0.8 wt% on a copper substrate was performed to study the corrosion behaviour of electroless NiP/Cu systems. The P content of the electroless NiP coatings plays an essential role in the microstructure of the coatings in terms of crystallinity. The crystallinity variations, representing the extent of crystalline and amorphous phases within the material, with P content, affect the local electrochemical characteristics and, hence, the corrosion protection behaviour of electroless NiP coatings. The coatings with the highest P content showed the best corrosion performance in a 3.5 wt-% NaCl solution. In contrast, the surface of the electroless NiP coatings with low P content is more susceptible to corrosion due to the presence of locations with heterogeneous electronic properties that initiate localised corrosion. Microgalvanic interactions with a high cathode-to-anode surface ratio govern the localised corrosion kinetics of the low P-content samples. A high concentration of nodule boundaries and/or other existing structural defects on the surface serve as anodic sites, whereas the remainder of the surface serves as cathodic sites. • P content influences the localised corrosion mechanism of electroless NiP coatings. • P contents are associated with changes in NiP microstructure and topography. • Electrochemical and microstructural analyses offer insight into the corrosion mechanism. [ABSTRACT FROM AUTHOR]

On the basis of asymptotic and exact solutions, simulation of an analytical model of a journal bearing with a nonstandard supporting coating adapted to friction conditions upon lubrication by a liquid lubricant and a molten metallic coating of the shaft surface characterized by micropolar rheological properties in a laminar flow regime is described. The analytical dependences have been obtained for the radius of the molten coating surface, field of velocities, pressures upon the zero (without consideration of the molten coating) and the first (with consideration of the molten coating) approximations, as well as for the bearing capacity and friction force. [ABSTRACT FROM AUTHOR]

Compressible metallic porous materials (CMPMs) have great potential for development in the energy and environmental fields. However, the scale-up preparation of CMPMs with stable metal layers, excellent elasticity, and multifunctionality remains exceedingly challenging. In this study, we designed a novel strategy with the aid of polymer-assisted metal deposition to synthesize metallic porous wood (Ni-PW) with a hierarchical cellular structure and excellent elasticity. Our approach can produce highly compressible MPW using intrinsically porous delignified wood with only 15.16% strain loss under a large compressive strain of 40% after 1000 loading-unloading cycles and 129.4 μm of the average porous size of the Ni-PW measured by mercury injection method. The resulting Ni-PW displays excellent antibacterial properties for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) and electric conductivity (Resistance < 7 ty), which renders great potential in energy and environmental applications. This research provides a new insight into the fabrication of CMPMs in a cost-effective (~56.5 ¥ m−2) and scalable way. [ABSTRACT FROM AUTHOR]

This paper describes the use of Supersonic Laser Deposition (SLD) to manufacture nickel/graphite composite coatings on titanium and aluminium substrates. Laser heating is critical for depositing coatings containing up to 13.3 vol% graphite. For a given feedstock composition, the resulting graphite content and average size of the graphite particles retained in the coating increases with laser power, until substrate melting occurs. The effect of the powder type, feedstock composition, and process conditions on coating structure is characterized. The friction and wear behaviour of selected coating compositions is examined. Nickel coatings containing 13.3 vol% graphite demonstrated self-lubricating behaviour with a stable coefficient of friction below 0.14 in pin-on-disc testing. [ABSTRACT FROM AUTHOR]

This work reports yarn pull-out studies of commercially available Kevlar® KM2+ individual yarns coated with metallic layers (copper, aluminum, aluminum nitride and silver) via a directed vapor deposition process. The uncoated control and metal-coated Kevlar® yarns are hand-woven into fabric swatches for quasi-static pull-out experiments. To perform these experiments, a yarn pull-out fixture is custom-designed and fabricated to apply transverse pre-tension to the fabric. Three levels of transverse pre-tensions are studied at 100 N, 200 N, and 400 N. The results showed that both peak pull-out force and energy absorption during the pull-out process increase with increase in transverse pre-tension. All the metal-coated groups showed an approximately 200% increase in peak pull-out force and a 20% reduction in tenacity compared to uncoated control. Furthermore, all the metal-coated groups showed an increase in energy absorption, with aluminum-coated yarns showing the highest increase of 230% compared to control. These results suggest enhanced frictional interactions during yarn pull-out in metal-coated yarns compared to uncoated control as evidenced by the surface roughness profile of individual fibers and inter-yarn frictional calculations.

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The noncoded aromatic 3,4-dihydroxy-L-phenylalanine (DOPA) amino acid has a pivotal role in the remarkable adhesive properties displayed by marine mussels. These properties have inspired the design of adhesive chemical entities through various synthetic approaches. DOPA-containing bioinspired polymers have a broad functional appeal beyond adhesion due to the diverse chemical interactions presented by the catechol moieties. Here, we harnessed the molecular self-assembly abilities of very short peptide motifs to develop analogous DOPA-containing supramolecular polymers. The DOPA-containing DOPA-DOPA and Fmoc-DOPA-DOPA building blocks were designed by substituting the phenylalanines in the well-studied diphenylalanine self-assembling motif and its 9-fluorenylmethoxycarbonyl (Fmoc)-protected derivative. These peptides self-organized into fibrillar nanoassemblies, displaying high density of catechol functional groups. Furthermore, the Fmoc-DOPA-DOPA peptide was found to act as a low molecular weight hydrogelator, forming self-supporting hydrogel which was rheologically characterized. We studied these assemblies using electron microscopy and explored their applicative potential by examining their ability to spontaneously reduce metal cations into elementary metal. By applying ionic silver to the hydrogel, we observed efficient reduction into silver nanoparticles and the remarkable seamless metallic coating of the assemblies. Similar redox abilities were observed with the DOPA-DOPA assemblies. In an effort to impart adhesiveness to the obtained assemblies, we incorporated lysine (Lys) into the Fmoc-DOPA-DOPA building block. The assemblies of Fmoc-DOPA-DOPA-Lys were capable of gluing together glass surfaces, and their adhesion properties were investigated using atomic force microscopy. Taken together, a class of DOPA-containing self-assembling peptides was designed. These nanoassemblies display unique properties and can serve as multifunctional platforms for various biotechnological applications.

Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the action of several damage mechanisms associated with the impact of hard particles from the residue of burnt coal, the ashes. The employment of coatings should be given into consideration particularly for critical components, which are subject to severe erosive conditions is one of the solutions. However, the choice of material will depend on several factors, including the properties of aggressive ashes. This paper aims to characterize ashes generated by a Brazilian coal-based power plant and a FeCrNbNi-based metallic coating obtained by the electric arc spraying process. No trace of sulfur content was found in fly ashes and it was defined that wear is mainly related to the impact and energy of hard particles are the leading causes of degradation in coal-fired boiler equipment. According to the assessment, applied coating showed (5 ± 2)% by volume of pores and cracks, with 1.6% of oxides after the spraying process and hardness 35% greater than ash particles. Preliminary results in field operation suggest that the material showed relatively low wear compared to the original substrate and showed great applicability in controlling material deterioration for this purpose.

This paper presents a study on advanced material designs suitable for lightweight space packaging structures. During this study, several material designs were proposed, evaluated and in the end three packaging structures were designed, manufactured and validated through a test campaign. The material designs proposed consisted in hybrid laminates composed of a composite substrate and integrating metallic foils with high atomic number (Low Z - High Z - Low Z concept) and metallic coatings to increase the structure’s protection against harsh space conditions. The packaging structure design selected was a 2U CubeSat. A FEM analysis was performed on two different designs which showed good mechanical resistance under static loads, and regarding the modal analysis, the natural vibration frequencies of the CubeSat were in the imposed limits (outside of the critical range of 1-125 Hz). To reproduce the dynamic environment encountered during launching stage, vibration tests were performed. The structures were validated through a test campaign (vibration tests) and their first vibration mode overcomes 100 Hz, results predicted by the FEM analysis.

Temperature monitoring is an essential task in cryogenic engineering to ensure the safety of equipment, where highly sensitive and reliable sensors are required to provide real-time and accurate information about temperature. Titanium (Ti)–copper (Cu)-coated fiber Bragg grating (FBG) temperature sensors with a gradient of material properties to minimize thermal stresses are hence fabricated by a combination of Ti/Cu magnetron sputtering and Cu electroplating. The thermal characteristics and thermal fatigue behavior of the sensors are investigated. The sensors exhibit significantly higher sensitivity than that of the bare FBGs at cryogenic temperatures down to 79 K, with good repeatability and stability. Their response to the temperature changes can be precisely described by a quadratic-polynomial equation. No obvious variations in the zero-point, the reflection spectrum, and the temperature sensitivity of the sensors exposed to thermal fatigue from 77 K to room temperature are observed before fatigue failure which could be attributed to the formation and growth of subcritical cracks within the fiber rather than that of fatigue cracks within the metallic coatings, as a result of the cyclic thermal stresses induced by the large differences in coefficient of thermal expansion between the silica optical fiber and the metallic coating materials. The results demonstrate that the multilayer metal-coated FBG sensors provide great potential for temperature measurements or temperature compensation in cryogenic engineering by proper selection of metallic coatings with a gradient of material properties. [ABSTRACT FROM AUTHOR]

The results of studying the properties of carbon cloth with a metallic coating and the related coal plastics prepared by a vacuum infusion technology are presented. It is experimentally found that the metallic coating affects the porosity of the cloth, decreasing it by 17% at a coating thickness of 30 nm. The deposition of the metallic coating on the carbon cloth weakly affects on the total impregnation time, decreasing it only by 3.6–4.1%. A comparative analysis of the two technologies by a standard method with the manual fabrication of a vacuum sack and using a test bench with an elastic membrane shows that the use of the test bench makes it possible to accelerate the impregnation process, to decrease the consumption of a binder, and to level the motion front of the binder. [ABSTRACT FROM AUTHOR]

The adhesion of a metallic coating to a carbon tape after its treatment with cold plasma under various conditions is experimentally studied, and the optimum conditions are selected. Plasma treatment is found to increase the adhesion strength estimated by adhesive tape testing by several times. A metallic coating is deposited onto a carbon tape after plasma treatment by magnetron sputtering. A carbon tape with a metallic coating is used to fabricate carbon-fiber reinforced plastics (CFRPs) with an epoxy binder, and the plastics are molded using vacuum infusion. A metallic coating made of stainless steel on a carbon tape is found to increase the interlayer shear strength of CFRPs by 40%; a titanium coating, by 30%; and a copper coating, by 13%. [ABSTRACT FROM AUTHOR]

The co-deposition of natural particles was studied in zinc electroplating on mild steel in the acidic sulfate bath aiming a composite coating. Despite most papers reported the effect of natural extracts in such process, the evaluation of natural particles adhered to the coating was not explored yet. The process efficiency, surface morphological changes, and corrosion resistance were evaluated in different concentrations of avocado seed powder (ASP, Persea americana), cocoa bean shell powder (CBSP, Theobroma cacao), and garlic peel powder (GPP, Allium sativum). In general, the current efficiency was not significantly influenced by the presence of any natural particles, reaching values over 90 %. The presence of natural particles impacted the active sites on the substrate surface, modifying the grain growth assessed by scanning electron microscopy (SEM) analysis. The GPP samples showed better visual aspect and higher compactivity. By Fourier transform infrared spectroscopy analysis, such natural particles are constituted by molecules of long carbon chains with chemical groups – amines, carboxylic acids, and phenols. Hence, the presence of natural particles in the coating layer led to different responses in the contact angle test, where GPP samples showed higher wettability (θ < 90°), followed by ASP and CBSP samples (θ > 100°). Such behavior indicates a greater bath penetration during the electroplating process in the presence of more hydrophilic particles, which may have resulted in the refined deposits of the GPP samples. The concentration of 0.330 g/L GPP presented higher impedance modulus (6548.3 Ω.cm2 at 0.03 Hz) in the electrochemical impedance spectroscopy (EIE) and reduced the anodic ionic current density at least four times in the scanning vibrating electrode technique (SVET). The same was observed in the salt spray test (SST) adapting ASTM B117 , which revealed to be sensitive enough to indicate that the 0.330 g/L GPP sample showed greater corrosion resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • Effect of the metallic flakes on optical properties of effect coatings using mathematical descriptions of spectrums such as derivatives of reflectance curves and PC analysis method was investigated. • The colorimetric and spectrophotometric changes caused by adding aluminum flakes to the solid base-coat were discussed deeply. • The spectrum derivatives with respect to the wavelength of the spectral reflectance were investigated for metallic samples in comparison to the solid ones. • The basis vectors obtained from PCA method were computed and evaluated for solid and metallic sets and the effect of adding metallic flakes to solid base coats on PC vectors was studied. Abstract Coatings containing aluminum flakes are attractive in terms of appearance in both industry and scientific researches. In the present study, attempts were made to investigate the effect of aluminum flakes presence on the appearance properties of metallic coatings. Therefore, metallic coatings containing three grades of aluminum flakes with different size distributions and solid samples were prepared in nine color centers. In addition to the spectral reflectance and colorimetric values, the derivative of the spectral data with respect to the wavelength and the main components from a Principal Component Analysis on reflectance data of each spectral set were investigated for the prepared solid and metallic samples. The results showed that aluminum flakes in the metallic samples provide more negative values of b* because of higher light scattering of blue wavelengths from the edges and probably rough parts on the surface of the flakes. Depending on the used absorption pigments, aluminum flake size could affect colorimetric variations. The main peak of the spectral derivative, with respect to the wavelength, showed that the intensity and sometimes the wavelength at which the main peak occurred changed for the metallic samples in comparison to the solid ones. Furthermore, more valleys and peaks in the derivative spectrum appeared for the metallic samples, which seem to be a result of interaction between the solid base-coat and the aluminum flakes. Principal Component (PC) analysis showed that although the mean of the spectral curves of the metallic sets have higher values at shorter wavelengths because of the presence of aluminum flakes, the first PC vectors keep the characteristics of the solid set. The main peaks of the other basis vectors shift towards the shorter wavelengths. Moreover, in comparison to the solid set, the significance of the first PC vector decreased and the second one increased which was also influenced by the flake size. [ABSTRACT FROM AUTHOR]

Abstract This work describes the morphology, corrosion resistance, and antibacterial performance of copper coating deposited onto carbon steel by cold gas spray (CGS). Cross-sectional images of the coating showed a dense microstructure, with porosity lower than 1%. XRD analysis revealed no oxides or phases different to pure copper. The results of electrochemical tests demonstrated the efficient barrier properties and the compact microstructure of the coating, which protected the substrate against corrosion in chloride solution for >1000 h. The copper coating was effective as an antimicrobial agent for inhibiting the growth of Staphylococcus aureus , with bacterial growth being completely inhibited after 10 min of direct contact between the bacteria and the coating surface. Graphical abstract Unlabelled Image Highlights • Copper powders were sprayed onto carbon steel using cold gas spray (CGS). • Copper coatings are dense with low porosity and high adhesion. • Coating resisted to corrosion in 3.5 wt% NaCl solution for ~1100 h. • CGS coatings showed an antibacterial rate of the 100% after 10 min of test. [ABSTRACT FROM AUTHOR]

Abstract In this study, novel heat-treated shell-core-structured (SCS) NiCr-23Mo powder is employed to realize the deposition of a bulk-like metallic coating with excellent mechanical performance by plasma spraying. The SCS NiCr-23Mo powder was fabricated by cladding spherical Ni20Cr particles with refractory Mo as an alloying element. This ensures the generation of ultra-high temperature Ni16Cr23Mo droplets during the in-flight process of plasma spraying. The interface bonding between the Ni16Cr23Mo single splats and steel substrate, as well as the microstructure of the Ni16Cr23Mo coating were characterized. Mechanical behavior of the coating was examined by erosion test. Results showed that the Ni16Cr23Mo coating exhibited a dense microstructure with significantly improved adhesive strength. Moreover, effective bonding was formed at 78% of interfaces between the Ni16Cr23Mo splat and steel substrate, which was much higher than the 36% of the conventional NiCr splat. Erosion test revealed that the Ni16Cr23Mo coating presented excellent erosion resistance, being comparable to that of the Ni-based bulk alloy. Moreover, the Ni16Cr23Mo coating presents ductile mechanical behavior during erosion test rather than the brittle behavior of the conventional Ni-based alloy coating. Thus, a mechanically bulk-like coating with excellent interface bonding and excellent erosion resistance can be achieved by plasma spraying of the novel SCS NiCr-23Mo powder. Graphical abstract Unlabelled Image Highlights • A bulk-like NiCrMo coating was obtained by plasma spraying of novel shell-core-structured (SCS) NiCr-23Mo powders. • Effective bonding was formed at 78% of interface between Ni16Cr23Mo splat and steel substrate. • The mechanical behavior of the Ni16Cr23Mo coating becomes ductile rather than brittle based on erosion test results. • The Ni16Cr23Mo coating exhibited excellent erosion resistance comparable to that of the Ni-based alloy bulk. [ABSTRACT FROM AUTHOR]

The corrosion protection of Hastelloy-N alloy in LiF-NaF-KF (commonly referred to as FLiNaK) molten salt has been developed by pure Ni and Co coatings using the laser cladding technique. An immersion experiment with samples was performed in molten FLiNaK salt at 900 °C for 100 h. It was found that the corrosion rates of the pure Ni-coated specimen and the pure Co-coated specimen are 39.9% and 35.7% of that of Hastelloy-N alloy, respectively. A careful microstructural characterization indicates that a selective dissolution of the elemental Cr occurred in the surface of bare Hastelloy-N alloy, showing a severe intergranular corrosion. For pure metal-coated specimens, in contrast, only metal oxide formed during the laser cladding process dissolved into the molten fluoride salt. The dense pure metal (Ni or Co) coatings exhibit a slightly general corrosion and protect the Hastelloy-N substrate effectively. The possible corrosion mechanism for both coated and uncoated Hastelloy-N under the current experimental condition are discussed in this work. [ABSTRACT FROM AUTHOR]

The paper discusses the possibility of improving resistance of heat exchangers made of gray cast iron with flake graphite to hightemperature corrosion by providing them with metallic coatings. A metallic coating containing 76.9% Ni, 19.8% Cr, 1.7% Si, 0.9% Fe, and 0.9% Mn was applied by means of the plasma spraying method and subjected to cyclically variable thermal loads in the atmosphere of solid fuels combustion products (oxygen, sulfur, chlorine, and sodium). In a 30-day thermal load test held at temperature 500°C it has been found that thickness of the metallic coating decreased from the initial (240 ± 6) µm to (231 ± 6) µm. The depth to which sulfur, chlorine, and sodium penetrated the coating was about 30 µm. Increased oxygen content occurred along the whole coating depth. In the coating area adjacent to the substrate surface, the content was twice as high compared to this observed in the initial coating material. Although presence of oxygen was found within the whole depth of the coating, i.e. (231 ± 6) µm, no signs of susceptibility of the sprayed metallic layer to separation from substrate of gray cast iron with flake graphite were found. [ABSTRACT FROM AUTHOR]

In the face of aggressive environment, cathodic protection shows promise as a solution to reducing the risk associated with corrosion initiation and propagation of prestressed concrete structures. This can be achieved by applying an impressed current to the system that brings the electrical potential of steel members to such a level where localized corrosion does not occur. However, atomic hydrogen that evolves at negative potential can cause hydrogen embrittlement of ASTM A416 steel wires used in prestressed concrete, leading to system failure without warning. To reduce the risks of brittle failures, nickel–cobalt alloy was applied to steel wires. The corrosion properties of the coated specimens were studied in simulated concrete and corrosive environments. The steel wires were also placed in an aggressive environment to predict the time to failure of the samples due to hydrogen embrittlement. A brittle crack developed in wires tested in the as-received condition, but samples coated with the proposed coating passed the embrittlement test. Nickel–cobalt coated specimens not only showed corrosion properties similar to as-received samples, but also did not fail the embrittlement test. [ABSTRACT FROM AUTHOR]

• Considerable densification of beneath deposited Al layers caused by Zr particles. • Highest R pol and |Z| f=0.01Hz values were obtained for Zr/Al coated Mg alloy. • Surface film thickness was 34.40 for Al and 29.90 nm for Zr/Al after 24 h immersion. • Zr/Al coating immersed for 24 h showed a passive potential for a wide range of pHs. • Zr with smaller crystallite size/higher dislocation density showed lower wear rate. Commercially pure (CP) Zr coating with high microhardness (387 ± 26 HV 0.025) was produced on CP-Al coated Mg alloy by a high pressure cold spray (HPCS) system. Substantial densification of Al layers, beneath deposited Zr coating, was observed because of shot-peening influence by Zr particles. The electrochemical impedance spectroscopy after 24 h of immersion in 3.5 wt% NaCl electrolyte revealed highest charge transfer resistance (R ct), polarization resistance (R pol), and corrosion resistance (|Z| f=0.01Hz) for the Zr/Al coated Mg alloy. Also, wear rate for the Zr/Al coating was lowest which could be attributed to its higher hardness caused by smaller crystallite size and higher dislocation density. [ABSTRACT FROM AUTHOR]

Variation in the thermal conductivity of a metal-coated tri-walled carbon nanotube (3WCNT), in the presence of vacancies, was studied using non-equilibrium molecular dynamics simulations. A Two-Temperature model was used to account for electronic contribution to heat transfer. For 3WCNT with 0.5% and 1% random vacancies, there was 76%, and 86% decrease in the thermal conductivity, respectively. In that order, an overall ~66% and ~140% increase in the thermal conductivity was recorded when 3 nm thick coating of metal (nickel) was deposited around the defective models. We have also explored the effects of tube specific and random vacancies on thermal conductivity of the 3WCNT. The changes in thermal conductivity have also been justified by the changes in vibrational density of states of the 3WCNT and the individual tubes. The results obtained can prove to be useful for countering the detrimental effects of vacancies in carbon nanotubes.

This paper presents a study on advanced material designs suitable for lightweight space packaging structures. During this study, several material designs were proposed, evaluated and in the end three packaging structures were designed, manufactured and validated through a test campaign. The material designs proposed consisted in hybrid laminates composed of a composite substrate and integrating metallic foils with high atomic number (Low Z - High Z - Low Z concept) and metallic coatings to increase the structure's protection against harsh space conditions. The packaging structure design selected was a 2U CubeSat. A FEM analysis was performed on two different designs which showed good mechanical resistance under static loads, and regarding the modal analysis, the natural vibration frequencies of the CubeSat were in the imposed limits (outside of the critical range of 1-125 Hz). To reproduce the dynamic environment encountered during launching stage, vibration tests were performed. The structures were validated through a test campaign (vibration tests) and their first vibration mode overcomes 100 Hz, results predicted by the FEM analysis. [ABSTRACT FROM AUTHOR]

Insufficient wetting of Na on Na-β'-alumina is responsible for an increased interfacial polarization in Na-batteries if the operating temperature is below 270-300 °C. In this study, Na alloys (Na-Sn, Na-Bi and Na-In) on the ceramic surface are examined on their capability to improve the wetting with molten sodium at medium temperatures and thereby enabling operation of the cell at temperatures in the range of 105 to 150 °C. Metallic coatings with Bi or Sn confirm this improvement at a temperature of 115 °C. The overpotential of a symmetrical Na│Na-β'-alumina│Na cell is determined by galvanostatic cycling and electrochemical impedance spectroscopy and then associated to contact angle measurements. As a result, both the alloys and the metallic coatings have a positive impact on wetting and reduction of the overpotential during galvanostatic cycling. [ABSTRACT FROM AUTHOR]

In this study, the heat transfer augmentation of a two-phase closed thermosiphon (TPCT) with a thin, porous copper coating is studied and compared with an uncoated TPCT. The inner surface of the TPCT is coated using an electrochemical deposition process. The coated and uncoated TPCTs are filled with deionised water and tested with a heat input of 50 to 250 W. The heat transfer coefficient in the evaporator and condenser is assessed and compared with the thermal resistance of coated and uncoated TPCTs. The effects of the inclination angle, power input and thin copper coating on the performance of the TPCTs are explored. The heat transfer coefficient of the evaporator is found to be enhanced up to 44% at a heat flux of 10 W/m 2 for an inclination angle of 45°. TPCTs with an oxide coating are also compared to those with a metallic coating and the metal-coated TPCT was found to perform better than the oxide-coated TPCT. The effect of non-dimensional numbers, such as Bond (Bo), Webber (We), Kutateladze (Ku) and condensation (Co) numbers, with the variation of heat flux, is also investigated. [ABSTRACT FROM AUTHOR]