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In this paper, aluminum coatings were prepared on a steel substrate by thermal spraying, and the corrosion morphology and corrosion resistance of the coating were investigated by salt spray and immersion tests. The results showed that after three months of salt spray tests, the coating still exhibited a surface morphology without significant damage and had good damage tolerance. Further effective protection of the substrate can be achieved by spraying the coating surface with paint. After three months of immersion test, the corrosion rate of samples with thicker coatings was located between 0.002 mm/y and 0.005 mm/y, and only a small amount of corrosion products was observed on the coating surface. The coated samples after salt spray and immersion tests maintained sufficient adhesion (17.07 MPa and 19.25 MPa), and the surface aluminum coating was highly reliable for protection of the steel substrate. In general, the reliability of the coating can be further improved by painting the surface of the thicker Al coating. This provides more ideas for the protection of transmission and transformation equipment. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the process of synthesis of a composite powder of the aluminum–silicon nitride system in order to identify the mechanism of the formation of granules and the distribution of the hardening phase of the Sialon type (SiAlON) in them. The properties of a powder composite obtained using various modes of mechanosynthesis have been studied. The results of determining the hardness, chemical composition, and distribution of elements in the resulting coating are given. [ABSTRACT FROM AUTHOR]

Purpose: To compare microtensile bond strength and characterize the bond of nano-structured alumina-coated vs tribochemically silica-treated zirconia specimens. Materials and Methods: Eight zirconia blocks were assigned to two groups: nano-structured alumina coating (AlN) and tribochemical silica treatment (CoJet) followed by RelyX Ceramic Primer (COJ). For each group, two identically pre-treated zirconia blocks were bonded with RelyX Unicem 2 Cement and cut into 30 stick-shaped specimens (1 x 1 x 9 mm³). A total of 120 specimens were stored in distilled water at 37°C for 24 h and then assigned to three groups (n = 20/test group): short-term test, thermocycling 5000 cycles, and thermocycling 10,000 cycles. The specimens were tested in tensile mode. The bond strength results were analyzed using two-way ANOVA, followed by one- way ANOVA and Tukey's HSD (α = 0.05). Failure mode and surfaces were analyzed with optical microscopy and SEM. FTIR and EDS were used for chemical analyses on primer-, mechanically and/or chemically pre-treated surfaces. Results: The mean bond strengths of AlN and COJ groups were not statistically significantly different in all aging conditions (p > 0.05). Thermocycling significantly decreased the bond strength of both groups (p < 0.01). The AlN groups exhibited predominantly either adhesive or mixed failure, whereas the specimens in the COJ groups mainly presented either mixed or cohesive failure in composite cement. Silane chemically reacted with mechanically pretreated COJ surface via the absorption of Si-O group. Conclusion: The composite-zirconia bond strength after application of a nano-structured alumina coating was comparable to that after tribochemical silica treatment. [ABSTRACT FROM AUTHOR]

The correlation of microstructural development and the kinetics of film growth has been investigated during the epitaxial film growth of an ultrathin binary Ag0.93Al0.07 solid solution on a Si(111)-7?7 surface at 300K by the combination of high-resolution transmission electron microscopy, X-ray diffraction, scanning tunneling microscopy, low energy electron diffraction, and realtime in-situ stress measurements. Up to a film thickness of 6±2 nm, epitaxial Ag0.93Al0.07 film growth is characterized by the strikingly extensive formation of planar faults parallel to the film/ substrate interface, while at larger thickness the film grows practically defect-free. As revealed by real-time in-situ stress measurements, the extensive formation of planar faults at the very initial stage of growth is not driven by the reduction of the system's elastic strain energy but is rather caused by a striking thickness-dependence of the stacking-fault energy owing to a quantum size effect of the ultrathin metal alloy film, resulting in a frequent succession of fcc and hcp stackings of close-packed layers during the initial stage of film growth. The extensive development of planar faults at the initial stage of film growth (<6±2 nm) is associated with the occurrence of a high density of kinks and corners at thereby atomically rough surface ledges, which strongly enhances the downward transport of adatoms from higher to lower terraces (interlayer mass transport) by a reduction of the effective diffusion barrier at the edge of surface steps and by increasing the driving force for adatoms to attach to the surface ledges. As a result, the epitaxial Ag0.93Al0.07 film initially grows in a 2D layer-by-layer type of growth and thus establishes atomically smooth film surfaces. For the practically planar-fault-free growth at thicknesses beyond 6±2 nm, interlayer mass transport becomes distinctively limited, thereby inducing a transition from 2D to 3D type of film growth. [ABSTRACT FROM AUTHOR]

Conventional benzoxazine resins, in spite of their excellent thermo-mechanical properties and good solvent resistance, suffer from high curing temperatures and limited self-healing/ reprocessability. In this frame, bio-sourced phenol (Phloretic acid), various diols (Dodecandiol/PEG200/Ethylene glycol), and amine (monoethanolamine) have been used in appropriate proportions to synthesize innovative benzoxazine precursors bearing exchangeable ester functions following a solventless method. They can be directly handled and used for coating applications without using any solvent. The overall synthesis was followed by Nuclear Magnetic Resonance and Fourier transform infrared spectroscopy (FT-IR). The reduced curing temperature, thermal stability, good thermo-mechanical performance, and ester bond exchange-ability system were demonstrated by Differential Scanning Calorimetry (DSC), thermogravimetric analysis (TGA), and Dynamic mechanical analysis (DMA - stress relaxation testing), respectively. The elaborated resins were applied on etched aluminum 1050 without solvent and the corrosion resistance of the coatings was investigated by electrochemical impedance spectroscopy (EIS). The electrochemical results showed proper corrosion protection on aluminum substrates. The best result was obtained with Dodecandiol-based benzoxazine coating due to its longer aliphatic chain and hydrophobic property. Comparing this coating with an epoxy-based benchmark showed enhanced corrosion resistance for the benzoxazine after 50 days of immersion, making it an interesting candidate for future industrial use. • Bio-sourced benzoxazines resins were synthesized. • The crosslinked polymers have healing, repair, and recycling properties. • Solvent-free coatings were applied. • Coatings show good anticorrosion behavior on AA1050 aluminum alloy. [ABSTRACT FROM AUTHOR]

In this paper, aluminum coatings were prepared on a steel substrate by thermal spraying, and the corrosion morphology and corrosion resistance of the coating were investigated by salt spray and immersion tests. The results showed that after three months of salt spray tests, the coating still exhibited a surface morphology without significant damage and had good damage tolerance. Further effective protection of the substrate can be achieved by spraying the coating surface with paint. After three months of immersion test, the corrosion rate of samples with thicker coatings was located between 0.002 mm/y and 0.005 mm/y, and only a small amount of corrosion products was observed on the coating surface. The coated samples after salt spray and immersion tests maintained sufficient adhesion (17.07 MPa and 19.25 MPa), and the surface aluminum coating was highly reliable for protection of the steel substrate. In general, the reliability of the coating can be further improved by painting the surface of the thicker Al coating. This provides more ideas for the protection of transmission and transformation equipment.

A conceptually new technology for the application of aluminum coatings on 18G2C steel by the electrolytically deposited NaF-NaCl - AlF3 ionic melt method has been developed. To solve the tasks set in the work, a set of experimental and computational research methods was used: metallographic analysis, energy dispersion microanalysis, mechanical tests, and calculation of the oxidation rate of samples. The mechanical characteristics of the samples of reinforcing steel were determined on a rupture machine FP-100 at an active capture rate of 2.5 mm / min. The relationship between the rates of electrochemical oxidation of the aluminide coating, its mechanical properties, with the distribution of aluminum in the depth of the samples and its phase composition have been determined. The increase of mechanical characteristics of samples from 18G2S steel with an aluminum covering in comparison with usual reinforcing steel is shown. The sequence of structural-phase changes of metal in the process of aluminide coating is determined and its influence on mechanical and corrosion resistance is determined. Experimental evaluation of the rate of oxidation of 18G2C steel samples with aluminum coating under the conditions of sulfuric acid electrolyte at an electric current of 11 to 18 A has been conducted. The developed technology of electrolytic deposition of aluminum has scientific and practical interest for the construction industry. The developed coating makes it possible to increase the mechanical properties of steel by almost 12% and to increase the corrosion resistance.

Thermal sprayed aluminum coatings are widely used for protection against marine corrosion. The high velocity oxy-fuel process (HVOF) makes it possible to deposit aluminum coatings with high particle velocity and, thus, higher coating adhesion than other thermal spray techniques. This work deals with HVOF aluminum coating deposition on complex shapes and investigates the effect of the spray angle on coating formation. It also analyzes the effect of substrate preheating and nitrogen carrier gas flow. The spray angle was the most influential parameter on the HVOF coatings properties. A spraying angle of 60° promoted a better deposition behavior in inner and outer corner complex profiles. However, on internal corners and concave surfaces, the coating microstructure presented voids and cracks. A spray angle of 90° increased the adhesion and resulted in better results for the potentiodynamic polarization tests on concave and convex samples. [ABSTRACT FROM AUTHOR]

For decades, zinc- and aluminum-based coatings have been considered the best material choice for steel corrosion protection since they may act as a protective barrier and show sacrificial behavior. These coatings are often prepared by galvanizing methods. However, their application by thermal spraying techniques (wire arc spraying, WAS and flame spraying, FS) has been proved as a cost-effective solution for the preparation of long-term corrosion-resistant coatings. This review selectively collects the most relevant information about the application and performance of these two techniques on Zn and Al coatings for corrosion protection. The report summarizes separately the Zn and Al data from the effect of the spraying parameters on coating properties on the one hand, and the results shown in long-term studies carried out in relevant and real exposure conditions, on the other. Finally, this review includes a description and comparison of the most recent advances found out with the novel and emerging spray technique, cold gas spray, for the deposition of Zn and Al coatings for corrosion protection purposes. Nevertheless, the use of this technique has not reached the stage of wide industrial application yet and therefore its long-term performance is unknown, which suggests that there is still room for further development. [ABSTRACT FROM AUTHOR]

The preparation of superhydrophobic coating on the surface of aluminum alloy can effectively improve its performance in the harsh environment. In this work, a superhydrophobic coating with water contact angle (WCA) up to 157.5 ± 0.5° and sliding angle less than 3° is prepared on aluminum alloy 6061 substrate by simple and environment-friendly hydrothermal reaction and stearic acid modification. The in situ growth coating is composed of Zn-Al layered double hydroxide and the morphology of the coating was a micro–nano composite structure with micro-sheet and nano-needle. The stearic acid is combined with the coating by physical adsorption and chemical bonding. The superhydrophobic coating imparts the properties of low adhesion, self-cleaning, and anti-corrosion to the aluminum alloy substrate, and it also has good high-temperature stability, acid and alkali resistance, mechanical stability and time durableness. The superhydrophobic coating can spontaneously recover 7 times after damaged by oxygen plasma etching. The outstanding comprehensive performance of the coating makes it a promising application for protection of aluminum alloy. [ABSTRACT FROM AUTHOR]

Sustainable betalain pigments extracted from beetroots were used as eco-friendly film coating over aluminium surface. The film coating was examined and verified by corrosive 1.0 M HCl solution. Characterization of chemical structure of the betalain pigments was done using spectroscopic attenuated total reflectance Fourier transform infrared (ATR-FTIR) and UV–Vis technique. Scanning electron microscope technique was used to demonstrate the eco-friendly film coating before and after been examined via corrosive 1.0 M HCl solution. Various operating conditions were studied to meet highest inhibition efficiency values such as betalain concentration, operating temperature and turbulent flow, and maximum inhibition efficiency = 98.4% was displayed. Multiple adsorption isotherms like Langmuir, Temkin, and Freundlich were used effectively to determine equilibrium constants and adsorption parameters. Dynamic investigations revealed a decline of rate of corrosion (RC) and rise of activation energy values (Ea) at higher betalain concentrations. Thermodynamic investigations revealed physisorption process, exothermic enthalpy, and low entropic values of betalain on aluminium surface. The noticeable specifications of low cost, abundance and sustainability, environmentally friendly, and high technical feasibility of betalain pigments adapt them to be the futuristic outstanding sustainable film coating for metal surfaces. [ABSTRACT FROM AUTHOR]

In this article, zinc and aluminum coatings were deposited on plain carbon structural steel (Q235) substrates by electric arc spraying. The coatings were then pore-sealed with a silicone resin to enhance their corrosion performance. The latter was tested in seawater containing sulfate-reducing bacteria by open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy. The tests showed that the pore-sealed Al coating had a superior corrosion resistance to the pore-sealed Zn coating in all the corrosion tests. The corrosion rates of the pore-sealed Zn coating first increased as the oxide film was easily destroyed. Then, they decreased as the corrosion products delayed the diffusion of the corrosive medium. On the other hand, the corrosion rates of the pore-sealed Al coating consistently decreased, most likely because of the protective effect of the dense Al2O3 film formed at the early stage of immersion and biological film formed by SRB at the later stage of immersion. [ABSTRACT FROM AUTHOR]

Magnesium-based alloys are appropriate materials for transportation applications owing to their high strength-to-weight ratio. However, the poor corrosion performance of Mg alloy limits its lifetime. In this study, the pure Al coating was deposited onto an AZ91D substrate by cold spraying, and then modified by friction stir-spot-processing. The interfacial microstructure and phase were studied in detail, and the effect of the intermetallic compounds on the microhardness and corrosion properties of the coatings was investigated. Results show that the sound and dense coatings were obtained after friction stir-spot-processing at 2400 and 2700 rpm. Al12Mg17 was found in the upper part of the 1/2 radius zone in the processed coating. The thin and thick IMCs were identified at the interface in the center and 1/2 radius areas, respectively. In the thick IMCs, mainly two types of multi-phase coexistence structures were observed. The four-phase coexistence structure dominated by Al3Mg2 revealed a higher microhardness than the three-phase coexistence structure dominated by Al12Mg17. In the processed coating, the upper part of the 1/2 radius zone containing Al12Mg17 exhibited a higher microhardness than the center zone. Moreover, the cold-sprayed Al coating provided more effective corrosion protection for the AZ91D substrate after FSSP. [ABSTRACT FROM AUTHOR]

Superhydrophobic silane/graphene oxide (GO) composite coating was successfully synthesized on aluminum surface by a facile dipping and curing process. The structure and composition of the obtained composite coating was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectra and X-ray photoelectron spectroscopy. Surface characterization results suggested that the single-layer GO functionalized with silane and formed uniform coating on aluminum surface. Electrochemical impedance spectroscopy (EIS) and electrochemical noise were used to investigate the anti-corrosion behavior of the prepared superhydrophobic silane/GO coating on aluminum in 1 M NaCl solution. The EIS results indicated that the prepared silane/GO coating exhibited the largest impedance compared with the silane coating and bare aluminum substrate. Besides, the values of Rct for the prepared superhydrophobic silane (936 Ω cm2) and silane/GO coatings (1670 Ω cm2) are more than 24 and 43 times that of the bare aluminum substrate (38.5 Ω cm2), respectively. Moreover, the pitting corrosion process of aluminum in NaCl solution was strongly inhibited in the prepared superhydrophobic silane and silane/GO coatings. Therefore, this work supplies an easy and economical way to prepare outstanding anti-corrosion coatings on aluminum surface, which promises a significant potential for practical applications. [ABSTRACT FROM AUTHOR]

Ni–Cu composite coatings have been fabricated on a 6061 aluminium alloy surface using a pulsed Nd-YAG laser. The basic coating was Ni–Cu powder with a Ni:Cu ratio of 4:1. The effects of adding to this powder 0.9 wt.% CeO2, 0.9 wt.% Si and 0.9 wt.% Co on the microstructure, microhardness and wear properties of the coatings have been investigated. The results show that, on adding the CeO2, Si or Co powders, the microstructure of the top region of the coating is mainly composed of equiaxed grains, dendritic crystals and fine equiaxed crystals, whereas the bottom region mainly consists of long rod-like, dendritic crystals and some particles. The average microhardness of the 99.1 wt.% Ni–Cu + 0.9 wt.% CeO2 coating is 529.05 HV, which was about four times higher than that of the bare 6061 aluminium alloy. In addition, the average friction coefficient decreased on adding CeO2, Si and Co powder to the Ni–Cu composite coating. [ABSTRACT FROM AUTHOR]

Recently it has been unearthed that many potable water sources around the world are contaminated with arsenic, which has got long-term health hazards for the consumers. Among different arsenic removal techniques, adsorption is widely used and easily achievable. Through the use of suitable adsorbent, arsenic can be significantly removed from potable water, which is a dire need for many distant communities where there is scarcity of alternative potable water source. This paper presents arsenic removal characteristics of different synthetic and natural sand samples through adsorption. To replicate the Skye sand which was found to be effective in removing arsenic, two synthetic sand samples (one coated with iron and the other coated with aluminium) were prepared in the laboratory. Different combinations of these samples were tested through batch experiments to evaluate their arsenic removal efficiencies under different conditions. It is found that among the synthetic adsorbents, the ones dried at 80 °C (during their preparation) showed the highest arsenic removal efficiencies. Also, among all the samples, iron oxide-coated sand (IOCS) showed the highest arsenic removal efficiencies, varying from 71 to 100% depending on the amount of doses, whereas with the use of natural Skye sand with the same variation in doses, arsenic removal efficiencies varied from 26 to 90%. [ABSTRACT FROM AUTHOR]

An investigation on joining of carbon fiber-reinforced thermoplastics to an aluminum alloy 6061 has been demonstrated using ultrasonic plastic welding process. A separate energy director, as required for focusing heat generation at interface during ultrasonic plastic welding, is replaced by high-performance thermoplastic coating on aluminum via a fluidized bed to make the process convenient for industrialization. Besides this, the functional coating acts as an insulator that resists galvanic corrosion and avoids fretting damage on metallic substrates. Critical welding parameters were experimentally realized (weld time: 900 ms, hold time: 1200 ms, and horn pressure: 0.5 MPa) for a maximum shear failure load in a lap-type joint configuration that showed uniform melting with higher fusion between thermoplastics. The fracture surface and cross-section morphology were examined for different joint nomenclatures. Delamination and first-layer ply failures associated with interlaminar shear of composites were predominant with an effective interfacial adhesion (mechanical anchoring) on aluminum asperities yielding a structurally rigid joints. A significant strength improvement of 40% was attained in mechanically treated aluminum substrates. An appreciable joint strength in comparison with adhesive bonding was obtained within a cycle time of 2.1 s. The real-time transient temperature analysis during welding provided a strong correlation with the weld formation. [ABSTRACT FROM AUTHOR]

Micron-diameter aluminum particles (μAl) are highly reactive when combined with a solid oxidizer. However, μAl powder is less reactive in a gaseous air environment, where oxygen is the only available oxidizer, unless very well dispersed. While enthalpy of oxidation for Al is high, many variables influence the viability of harnessing stored chemical energy within a single Al particle whose reaction is diffusion controlled. One way to enhance Al particle reaction is to coat the particle surface with a condensed phase oxidizing agent that is in immediate contact with the particle surface to promote diffusion reactions. Fluorocarbons such as perfluorocarboxylic acids have been used to enhance Al combustion for nanoscale Al (nAl) particles because fluorinated species are also reactive with the Al2O3 passivation shell surrounding the Al core particle. This study extends previous work on nAl toward μAl particles coated with perfluorotetradecanoic acid (PFTD) (F3C(CF2)11CO2H) and then characterizes the μAl-PFTD thermal reactivity. Samples were prepared with varying PFTD concentrations ranging from 0 to 20 mass percent, and experiments were performed using thermogravimetric analysis and high-speed infrared imaging on powder samples. Results show the PFTD-coated μAl particles provide higher apparent reaction temperatures (by about 500 °C) and longer burn times at elevated temperatures (by about 20%). Higher concentrations of PFTD tend to produce more gas-generating reactions with particles ejecting from the loose powder pile, but 9% PFTD coating on μAl particles provides a good balance of stable reactivity with high-temperature reactions (~ 1800 °C) and high-temperature burn times (~ 18 s). The higher temperatures for PFTD-coated μAl particles are attributed to the increased (nearly double) energy produced in the formation of AlF3 (56.10 kJ g−1) compared to Al2O3 (30.98 kJ g−1); both of these product species are identified in XRD analysis. In addition, the formation of AlF3 may reduce the melting and phase transition temperature of Al2O3 by several hundred degrees and contribute to catalytically activating the Al reaction. Overall, coating μAl particles with a fluorinated polymer facilitates reaction in an air environment, even for small concentrations of PFTD coating. [ABSTRACT FROM AUTHOR]

Recently, the temperature sensing using the fluorescence intensity ratio (FIR) of two thermally coupled emission bands of upconversion nanoparticles (UCNPs) has attracted more and more attention. Here, we report optical temperature sensing based on UCNPs with enhanced sensitivity via dielectric superlensing modulation. UCNPs are first deposed on an aluminium flake and then coated with a monolayer of polystyrene microspheres (PS spheres) to form a composite film. Under the excitation of near-infrared 980 nm laser, FIR of the transitions 1I6→3H6 (310 nm) and 1D2→3H6 (360 nm) of Tm3+ ions in UCNPs is highly sensitive to temperature variation. The thermal sensitivity of the composite film is enhanced by more than 70% at the temperature of 350 K relative to that without PS sphere superlens, which is ascribed to the modulation of the dielectric superlensing effect on the wave front of upconversion ultraviolet fluorescence. [ABSTRACT FROM AUTHOR]

During electric arc spraying, during the transfer of molten metal by air flow, there is a significant burnout of alloying elements with the formation of a large amount of oxides, which negatively affects the adhesion of the coating to the base. A solution to the problem of increasing the adhesion strength by using pulsation of the atomizing air flow is proposed. At the optimal frequency of the pulsed flow shut-off, the time of formation of liquid metal droplets at the ends of the electrodes coincides with the frequency of pulses of the spraying flow. As a result, the droplets acquire an optimal size, they are transported by an air flow with conservation of energy, a lower mass of oxygen and, as a consequence, a significant decrease in the oxidation of alloying elements in the sprayed material. The existing test methods of sprayed coatings for adhesion strength to the base are analyzed. The design of a modernized device for determining the adhesion strength is developed and described, which provides complex loading of the coating with a combination of tear-off and shear. The tests revealed a significant (up to two times) increase in the adhesion strength of aluminum, zinc-aluminum and steel (Sv08A) coatings applied with air pulsation. This is achieved by increasing the number of fusion zones of the coating particles between themselves and with the base. It is shown that the effect of the pulsation frequency on the adhesion strength changes along a curve with a maximum corresponding to a frequency of 70–80 Hz, regardless of the coating material. It has been established that the aluminum coating has an increased tendency to oxidation, as a result of which it is 15–20 % inferior to the zinc-aluminum coating in adhesion strength. The data obtained substantiate the use of the proposed spraying technology in production. [ABSTRACT FROM AUTHOR]

A coating based on boron carbide, aluminum oxide slip, and also aluminosilicate adhesive is used to improve the service properties of Cu–Al diffusion layer on blast furnace air tuyeres. An abrasive-resistant coating prepared from tungsten carbide powder wire is considered as an alternative to aluminium coating. KhN45Yu steel with a slip covering is tested to evaluate the possibility of using it for protecting a tuyere outer surface from burn-out. It is established that Kh20N80 nichrome coating and aluminosilicate adhesive coating applied to a diffusion layer increases the average life of standard aluminized tuyeres. [ABSTRACT FROM AUTHOR]

The aluminum nanopowder (nAl) was coated using hydroxyl-terminated polybutadiene (HTPB) as a coating agent. The morphology and structure of the coated samples (nAl/HTPB) were characterized by Transmission Electron Microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The active aluminum content of nAl and nAl/HTPB was measured by potassium permanganate titration methods and thermogravimetry (TG). The oxidation processes at high temperature were studied by thermogravimetry and differential scanning calorimetry (TG–DSC). The results indicated that the coated nAl showed core-shell structure, and HTPB can prevent the oxidation of nAl to a certain extent. The coating agent has an effect on the oxidative exothermic reaction temperature of aluminum powder, especially in high-temperature range. Due to the simultaneous action of HTPB and nAl, both the exothermic rate and exothermic calorific value increase. The thermal decomposition kinetics of nAl and nAl/HTPB was studied by the Kissinger method and the Ozawa method. The results showed that the average activation energies of nAl and nAl/HTPB were 428.05 and 300.8 kJ·mol−1, respectively. Mechanical sensitivity shows that the coating of HTPB is good to the friction and electrostatic sensitivity of nAl to a certain extent but not to the impact sensitivity. [ABSTRACT FROM AUTHOR]

CdSe capped with Tri sodium citrate (TSC), nanoparticles were organized by chemical process at ambient conditions. Spin casting technique was used to deposit thin films on substrates from glass at room temperature. Schottky junctions have been fabricated by depositing CdSe thin films using the spin coating on Aluminum (Al) and Florien Tin Oxide (FTO) coated glass substrates and their properties have been investigated by current-voltage measurements. The characteristics obey the pure thermionic emission theory and the contact showed a good rectifying behavior in both structures. [ABSTRACT FROM AUTHOR]

When writing this overview, a literary search was conducted in open sources in the Russian Federation and abroad on patents issued, overview publications in journals and books focusing on fluorine-based coatings over the past 15 years. We selected references related to fluorine-containing coatings on aluminum and magnesium alloys, on glass and plastics, with good indicators of resistance to corrosion and aggressive factors. [ABSTRACT FROM AUTHOR]

This study aims to improve the wear resistance of nickel-aluminum bronze (NAB) substrates by micro-arc oxidation (MAO). As this treatment is difficult to apply to NAB surface, cold spraying (CS) was first used to deposit aluminum with a purity of 99.5% onto the NAB substrates. The aluminum-coated substrate was then treated by MAO to convert the aluminum layer into Al2O3 coating in order to enhance the wear resistance. The tribological behavior of NAB substrates with or without the alumina coating was evaluated with a dry sliding wear test using a ball-on-flat reciprocating tester with varied testing loads ranging from 1 to 5 N. The results demonstrated that the oxide layer (Al2O3) formed on the aluminum layer enhanced the wear resistance of NAB alloy against 100Cr6 steel ball. Compared to uncoated NAB alloy, the wear resistance (inverse of wear rate) of the NAB alloy with the MAO coating was at least nine times higher than that of the uncoated NAB alloy at all testing loads. [ABSTRACT FROM AUTHOR]

Thermal management in a heat source-based electronic package is a necessity for reliable, long-lasting performance, as it is compulsory to dissipate the generated heat effectively. In this study, a novel nickel–phosphorous (Ni–P) alloy coating on an aluminum substrate is proposed to obtain improved thermal properties such as thermal conductivity (k), total thermal resistance (Rth-tot), and device junction temperature (Tj). The performance of the electroless Ni–P coating is observed under different deposition times and test conditions. The morphology of Ni–P coating results in a cauliflower-like grown structure on a substrate with 91.2 wt% of Ni and 8.8 wt% of P. X-ray diffraction spectra indicate the presence of crystalline Ni (111) and (220) peaks and an average crystallite size of 541 nm. The thermal conductivity of the Ni–P coated substrate results in 14.42 W/mK, whereas bare Al results in 8.03 W/mK. The thermal transient measurement results in an impressive difference in both Δ Rth-tot (6.31 K/W, 4.68 K/W) and Δ Tj (11.84 °C, 5.82 °C) under different test conditions. It is found that 0.33-μm surface roughness with a 7.5- μm coating thickness potentially improves the thermal behavior of Ni–P substrates, and it is believed that Ni–P is suitable for being used as an alternative coating option for electronic packages. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to improve the tribological properties of aluminum cylinder liner. Higher martensite contents were closely related to the higher hardness and excellent wear resistance of Fe-based coatings. Furthermore, the grain size of the Fe-based coating was approximately 40 nm, which provides an excellent fine grain strengthening effect. Design/methodology/approach: To improve the tribological properties of aluminum cylinder liners, a Fe-based martensite coating was prepared by internal plasma spraying technology, whose microstructure and tribological properties were then investigated. Findings: Sprayed Fe-based coating possessed a low contact angle and strong adhesion with lubricating oil. In a simulated engine condition, Fe-based coating exhibited a decreased friction coefficient and increased wear resistance under oil lubrication, which was dominated by a stronger adhesive force with lubricating oil, higher martensite contents on the worn surface, higher hardness and higher H/E value than those of the reference HT 200 and Al-19Si cylinder material. Originality/value: Nanostructure Fe-based martensite coating was sprayed on an aluminum cylinder liner, which demonstrated remarkable advantages over the reference cylinder material. [ABSTRACT FROM AUTHOR]

In this work, SiO2 nanoparticle–embedded polyurethane superhydrophobic coating on aluminium substrate was fabricated using spin coating technique. By embedding SiO2 nanoparticles into the polyurethane matrix, superhydrophobicity is successfully achieved with water static contact angle of 156 ± 3° and tilt angle of 6 ± 1°. Coating exhibits excellent self-cleaning and antifouling properties. Wetting stability of coating was further evaluated by performing water jet, bending, sand falling, tape peeling, floating, annealing, and chemical stability tests. It is found that coating is mechanically, thermally, and chemically stable. Water droplet impact test shows the bouncing, pinning, and splashing behaviour of water droplets at different impact velocities. The electrochemical experiment has demonstrated that the corrosion potential of aluminium after coating increases and the corrosion current density decreases, revealing the corrosion resistance property of coating. We envision that the self-cleaning, antifouling, and anticorrosive superhydrophobic coating of the polyurethane/SiO2 nanoparticle composite can effectively prevent the corrosion of aluminium and the aforesaid coating has great industrial applications. [ABSTRACT FROM AUTHOR]

Aluminum is an appropriate candidate for bipolar plates in proton exchange membrane (PEM) fuel cells because it reduces the final cost and weight of the fuel cell stack in comparison to stainless steel, titanium and graphite. However, a conductive coating layer is essential to protect it against corrosion. In this study, the electrochemical behavior of aluminum coated with titanium and amorphous carbon layers by physical vapor deposition is evaluated. The main goal is to investigate the corrosion protection performance and the possible failure reasons of the coating in sulfuric acid solutions (with different pH values) in the presence of 3 ppm sodium fluoride and elevated temperature (80 °C) to mimic the working conditions of PEM fuel cells. To reach our aim, electrochemical tests are combined with surface analysis techniques. It is revealed that at low pH values (pH = 2 and 3), the coating fails due to the acidity of the electrolyte solutions. However, in the electrolyte with pH = 4, present fluoride ions interfere and consequently lead to localized failures. It is noticed that the presence of defects in the coating is a key parameter in the application of coated aluminum as bipolar plates in PEM fuel cells. [ABSTRACT FROM AUTHOR]

Plasma electrolytic oxidation (PEO) with in situ anatase particle addition is applied to functionalize the surface of AA2024 alloy. A base potassium titanium oxide oxalate dihydrate aqueous electrolyte is used with up to 30 g L−1 anatase particle addition. The coatings' morphology and phase composition as a function of the anatase concentration in the electrolyte are characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), and glow discharge optical emission spectroscopy (GDOES). Photocatalytic activity, stability in chloride solution, and tribological properties are also determined. The main coating forming phases are anatase and rutile on top of a mixed interface region consisting of TiAl2O5 as reaction product between the TiO2 and an Al2O3 barrier layer on top of the Al substrate. The mixed layer is extending with increasing amount of particles added, due to intensified discharges. In addition, anatase‐to‐rutile phase ratio increases due to the additional anatase particles in the electrolyte. Thus, the photocatalytic activity is improving with the particle addition. The coatings' mechanical resistance is dropping first before increasing again with more particles added. Chemical and restored mechanical stability seems to be related to the extended mixed interface formation, which strengthens the bond to the substrate when more particles are added. [ABSTRACT FROM AUTHOR]

Air conditioning energy consumption accounts for most building energy consumption, indoor dehumidification is the main cause of air conditioning energy consumption. Optimize the dehumidification methods of air conditioning systems have great significance to the development of green buildings and people's pursuit of comfort. Improvement of fins on air conditioning heat exchangers is a hot topic of current research and has achieved considerable results in terms of indoor dehumidification and energy saving compared to traditional air conditioners. This paper reviews two kinds of heat exchangers modified by coating, including desiccant-coated heat exchangers and hydrophobic/hydrophilic coated heat exchangers. For desiccant-coated heat exchangers, the preparation methods of advanced desiccant materials and the possibilities of using this material to achieve excellent energy efficiencies were presented, and the operating parameters that affect thermal performance and dehumidification are determined, including airflow temperature, air velocity, inlet air relative humidity, and regeneration temperature. For hydrophobic/hydrophilic coated heat exchangers, different kinds of hybrid hydrophobic-hydrophilic surfaces are highlighted for they are a high water droplet nucleation rate and surface heat transfer efficiency. In addition, the challenges and future works are explained at last. This paper will provide a valuable reference for the follow-up research, which will be helpful for indoor humidity control and reducing the energy consumption of air conditioning. [ABSTRACT FROM AUTHOR]

• A medium-temperature selective coating obtained by co-sputtering titanium and aluminum targets was studied. • A novel CPC evacuated tube solar collector using the selective coating was developed. The instantaneous efficiency based the gross solar collector area is significantly higher than that of ordinary collectors. • An experimental steam system was built to verify the practical performance of the collector, it shows that after several years of operation, the collector still has excellent performance. This paper describes the development of a novel CPC (compound parabolic collector) evacuated tube solar collector, using a medium-temperature selective coating. The medium-temperature selective coating was obtained by co-sputtering titanium and aluminum targets. The absorptance and the thermal emittance of the heat treated coating is 0.95, and 0.04 at 80℃ respectively. The collector was optimized, using a manifold of copper U-tube with anti-oxidized coating and aluminum fin. An anti-reflection layer is added on the cover glass tube, and non-flash getter are used for maintaining the vacuum of the collector tubes. Thermal test results shown that the instantaneous efficiency based on gross area η G can reach 0.46 at the temperature of 150℃ and the normalized temperature difference T m * is 0.13 [(m2-°C)/W]. The experimental steam system application showed that the novel CPC solar collector can produce steam from water with temperatures about 108–145 °C during sunny days. It was also shown that the thermal performance of the solar collector did not degraded significantly. [ABSTRACT FROM AUTHOR]

The effect of high-intensity short-pulsed ion irradiation on the optical properties of multilayer coatings, consisting from thin layers of aluminum and silicon nitrides, deposited by reactive magnetron sputtering on glass, steel and silicon substrates, has been investigated. The larger the thickness of AlN layers, the stronger the effect of growth and radiation defects on multilayer coating properties. When the concentration of growth defects increases and its interaction intensifies, the radiation resistance of coatings grows. In general, the radiation resistance of coatings was due to the wide band gap of their constituent nitrides and the high concentration of strongly interacting growth defects distributed along the inter-crystallite and interlayer boundaries. [ABSTRACT FROM AUTHOR]

Present study reports the detailed nanomechanical and corrosion behaviours of crystalline and amorphous plasma electrolytic oxidation (PEO) coatings developed on Aluminium alloy-6061. The concentration of sodium silicate in the electrolyte is tailored to achieve crystalline and amorphous natures of the PEO coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM) and nanoprofilometry techniques are utilized to investigate microstructural and morphological properties of the PEO coatings. XRD studies confirmed that crystalline ceramic phases are obtained at lower silicate concentration while amorphous nature occurred for comparatively higher concentration of silicate in the electrolyte. Nanoindentation technique is utilized to study the mechanical properties such as hardness (H) and Young's modulus (E) of the PEO coatings. The scatter of the data is treated with well-established Weibull statistical method. Finally, in depth corrosion behaviour of the coatings are investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Amorphous coatings exhibited superior mechanical properties compared to the crystalline coatings. This is possibly linked with the presence of aluminosilicate phases and difference in silicon content in the coatings. However, as expected crystalline PEO coatings offer better corrosion resistance than the amorphous coatings and this behaviour is explained in terms of porosity contents of the coatings. [ABSTRACT FROM AUTHOR]

A process for producing a black oxide coating on aluminum alloy was investigated in the present work. The blackening process is widely used in industrial applications, but it was not deeply studied for aluminum alloys. The aim of this work is to study the black coating obtained on AA6060 surfaces employing two different solutions, both containing potassium permanganate, copper nitrate and nitric acid. The first solution carried out the coloring treatment at 50 °C, whereas the second one was done at room temperature. Different immersion times were investigated. The morphology of the coating was investigated by means of optical and electron microscopy to evaluate the color of the layer and the presence of defects, porosities, and cracks. X-ray diffraction analysis was performed to evaluate the protective layer composition. The corrosion properties were studied with potentiodynamic polarization tests and electrochemical impedance spectroscopy tests. The results showed that the blackening process performed at room temperature, besides the clear advantages in term of costs and safety, obtained more uniform coatings with increased corrosion performance in comparison with the ones obtained at higher temperatures. [ABSTRACT FROM AUTHOR]

The vacuum-arc plasma-assisted method is used to deposit a multilayer coating based on Ti and Al in two discharge systems – in a traditional plasma-assisted vacuum-arc spraying system and in a gas-metal beam-plasma generation system in a hollow cathode of a non-self-sustained low pressure glow discharge. The coatings synthesized in these discharge schemes have close elemental and phase compositions. The aluminum content in the coating deposited in the plasma-beam formation is 8% lower, which is probably due to a higher overall average value of the ion flux density on the surface of the growing film in a non-self-sustained glow discharge. In the coating deposited by sputtering in a beam-plasma formation, no elements are part of the material of the sputtered hollow cathode. The gas-metal beam-plasma formations generated at low pressure are promising in the processes of functional coating deposition by the vacuum-arc plasma-assisted method. [ABSTRACT FROM AUTHOR]

A silica-based organic–inorganic hybrid coating has been developed for corrosion protection of aluminum substrates by dip-coating technique. The hybrid sols were prepared by hydrolysis and condensation of trimethoxy(7-octen-1-yl)silane (TMOS) and tetraethyl orthosilicate (TEOS) in the presence of acetic acid. Structural characterization of the hybrid coatings was performed using powder X-ray diffraction analysis (PXRD). The morphology of the coating has been studied by scanning electron microscope (SEM). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests have been performed, and the results showed that the silane coatings had high corrosion resistance. The heat treatment of the coatings at various temperatures have been investigated, and the results show that 130∘C is an optimized temperature. The results expose that the hybrid coating enhanced the corrosion protection of aluminum in aqueous 3.5% NaCl solution. [ABSTRACT FROM AUTHOR]

The development of plasma electrolyte oxidation of aluminum alloys with the aim of using the dielectric properties of coatings is presented. Investigations of the morphology of oxide coatings formed on alternating current in the regime of an arbitrarily falling power in alkali-silicate solutions are presented. The data on the roughness and dielectric properties of the coating surface are used for joint consideration. In the discussion of the results, the functional tasks of local electrical insulating coatings of the tool of highly efficient processing technologies with the introduction of energy of electric discharges into the cutting zone to maintain the performance of grinding wheels with a diamond-metal composition of the working part were taken into account. [ABSTRACT FROM AUTHOR]

The dependences of the protective properties of the anodic oxide coatings on the AD31 aluminum alloy surface modified with nitrates of magnesium, potassium, and some 3d-elements on the composition of sealing solutions and parameters of finishing treatment were established by scanning electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy, and salt spray chamber tests. A mechanism of the formation of modified anodic oxide coatings during sealing and subsequent thermal treating was proposed. [ABSTRACT FROM AUTHOR]

Surface-engineered aluminum current collectors were developed through laser-based surface modification methods. Their performances as current collectors in supercapacitors clearly outperformed state-of-the-art carbon-coated commercial foils and were close to ideal gold foils, thanks to the enhanced interfaces provided by their engineered surfaces. Surface modifications included roughening by laser ablation in high vacuum, and coating with a carbon-nickel (C0.97Ni0.03) composite thin film deposited using pulsed laser deposition. The main improvement was obtained after coating the aluminum foil with the carbon-nickel protective layer, which was attributed to the almost pure sp² bonding state of the carbon and a mostly metallic nickel phase. The surface roughening treatment further decreased the interface resistance by providing a higher contact surface and a better mechanical anchorage of the active materials layer. The combination of laser roughening in vacuum conditions and subsequent deposition of an electronically conductive protective coating was therefore demonstrated as an efficient approach to improve the performance of current collectors for supercapacitors. [ABSTRACT FROM AUTHOR]

A novel fluorine-free and silicon-free superhydrophobic aluminum alloy (treated-Al) is fabricated by chemical etching using hydrochloric acid and hydrogen peroxide and modified with an organic carbon dot (OCD) coating. The water contact angle (CA) of the treated-Al surface increases with the OCD concentration. When etched aluminum (etched-Al) is modified with 0.5 mg/ml OCDs, a CA of 161.4° is achieved, which indicates good nonwettability. SEM results verify that porous microstructures with cavities are uniformly distributed on the surface of etched-Al, in contrast to the bare aluminum alloy, which forms a primary rough structure. After treatment with 0.5 mg/ml OCDs, a nanoparticle coating is dispersed on the rough structures of treated-Al-0.5, which can trap air and make a water droplet essentially rest on a layer of air. The treated-Al-0.5 material has good self-cleaning properties and can sweep away contaminants at both 20 and 0°C. The Ecorr and Icorr of treated-Al-0.5 are − 0.56 V and 2.82 × 10−6 A/cm2, respectively, which shows good anticorrosion performance. [ABSTRACT FROM AUTHOR]

To expand the applications of graphene which has so far been limited by the expensive nature of single-layer graphene, the effects of varying percentages of low-cost functionalized multilayer graphene nanosheets in siloxane-modified organic coatings were studied. The hydrophobic organic siloxane–acrylic resin was prepared by solution polymerization of acrylic monomers, and the graphene nanosheets were functionalized using fluorosilane. The coatings were sprayed on the LY12 aluminum substrate, and the wettability, anticorrosion, conductive, and accelerated weathering behaviors were comprehensively examined. It is shown that the increasing addition of functionalized graphene nanosheets increases the water contact angle and the surface conductivity. At 5% graphene loading, coating–substrate adhesion remains almost unchanged, while the electrochemical impedance parameters revealed good anticorrosion performance up to 10% loading. The surface measurements and Fourier transform infrared spectroscopy (FTIR) results confirmed the photostabilization ability of graphene loading in acrylic coatings during the accelerated weathering test. Also, the mechanical properties of the coatings were not damaged during the exposure, and pitting corrosion sites were observed only on the 20% graphene-filled coatings after 1000 h of exposure. These integrated analyses of mechanical properties and environmental accelerated tests are beneficial to engineering applications of graphene coatings. [ABSTRACT FROM AUTHOR]

Silicon oxide‐coated lithium aluminum layered double hydroxide (LixAl2‐LDH@SiO2) nanocrystals (NCs) are investigated to selectively separate lithium cations in aqueous lithium resources. We directly synthesized LixAl2‐LDH NC arrays by oxidation of aluminum foil substrate under a urea and lithium solution. Various lithium salts, including Cl−, CO32−, NO3−, and SO42−, were applied in aqueous solution to confirm the anion effect on the captured and released lithium quantity of the LixAl2‐LDH NCs. In a 5% solution of sulfate ions mix with lithium chloride, the LixAl2‐LDH NCs separated a larger quantity of lithium than in other anion conditions. To enhance regeneration stability and lithium selectivity, thin layers of SiO2 were coated onto the LixAl2‐LDH nanostructure arrays for inhibition of nanostructure destruction after desorption of lithium cations in hot water. The LixAl2‐LDH@SiO2 nanostructures showed enhanced properties for lithium adsorption, including increase of stable regeneration cycles from three to five cycles, and they showed high lithium selectivity in the Mg2+, Na+, and K+ cation mixed aqueous resource. Our nanostructured LDH lithium adsorbents would provide a facile and efficient application for cost‐efficient and large‐scale lithium production. [ABSTRACT FROM AUTHOR]

A model of combustion of aluminum nanopowder in water vapor has been analyzed with allowance for the formation of a condensed phase of aluminum oxide on aluminum particles. Various processes affecting the growth rate of the oxide coating have been considered including adsorption and surface diffusion of Al 2 O 3 molecules on aluminum particles, and condensation of the molecules on the oxide coating. Model calculations have yielded the time profiles of system temperature, phase and fractional composition, as well as the shape of oxide coated aluminum particles. The heterogeneous processes forming the condensed phase of aluminum oxide on Al particles have shown to increase heat generation in the system. On the other hand, shielding aluminum particles by oxide coating retards aluminum evaporation. The competition of these processes during the formation of oxide coating is one of the factors affecting the combustion of aluminum nanopowder in water vapor. [ABSTRACT FROM AUTHOR]

In this paper, the free vibration of an aluminum beam coated with imperfect and damaged functionally graded material is investigated. The imperfections consist of porosities, while 4 evenly distributed cracks represent the damage profile. A polynomial function is used to vary the density and elasticity through the thickness of the coating, while the effective elastic modulus and density are found with classical lamination theory. To achieve a truthful modeling, the gradually changing mechanical properties of the coating are modeled with 25 layers of material. The individual layers are isotropic and homogeneous. Numerical solutions are found with the finite element method using Timoshenko beam elements. MATLAB is used to write a finite element code, and the beam natural frequencies are found. To show the influences of porosity, crack depth, coating thickness and the polynomial function index (n) on the natural beam frequencies, a parametric study is conducted. It was found that the natural frequency values were significantly affected by the studied parameters. [ABSTRACT FROM AUTHOR]

To improve the passive radiative heat dissipation property of aluminum alloy, a novel-structural SiC/ h BN nanocomposite ceramic coating with high emissivity value (>0.86) was fabricated by one-pot liquid-phase plasma assisted electrophoresis and sintering (LPES) method. The special formation conditions of nanocomposite coating were optimized as: applied voltage was not lower than 600 V, temperature of electrolyte was ranged from 70 to 90 °C and the concentrations of SiC and h BN nanoparticles were 8 g/L and 40 g/L, respectively. The unique parameters contributed to the plasma assisted SiC and hBN nanoparticles synergistic electrophoresis and then sintering together by SiO 2 based glassy phase. The infrared emissivity in the wavelength of 3–20 μm was enhanced by SiC/ h BN nanocomposite coating, especially the value was up to 0.86 in 3–8 μm wavelength. The nanocomposite coating enabled the temperature drop by 10.4 °C for 1 W LED compared with the bare aluminum alloy, which leds to the cooling efficiency of 19.8%, respectively. The SiC/ h BN ceramic nanocomposite coating fabricated by one-pot LPES process shows a novel strategy to design excellent radiative heat dissipation property coatings. [ABSTRACT FROM AUTHOR]