Aluminum Surface Research Articles

Ultrawide Spectra Camouflage Coatings from Metallic Flake Powder.

Ultrawide-spectra-compatible camouflage materials are imperative for military science and national security due to the continuous advancement of various sophisticated multispectral detectors. However, ultrawide spectra camouflage still has challenges, as the spectral requirements for different bands are disparate and even conflicting. This work demonstrates an ultrawide spectra camouflage material compatible with visible (VIS, 400-800 nm), infrared (IR, 3-5 and 8-14 μm), and microwave (S-Ku bands, 2-12 GHz). The carbon nanotubes adsorbed on porous anodic alumina/aluminum flake powder (CNTs@PAA/AFP) material for ultrawide spectra camouflage is composed of bioinspired porous alumina surface layers for low visible reflection and aluminum flake powder substrate for low infrared emissivity, while the surface of the porous alumina layers is loaded with carbon nanotubes for microwave absorption. Compared with previous low-emissivity materials, CNTs@PAA/AFP has omnidirectional low reflectance (Ravg = 0.29) and high gray scale (72%) in the visible band. Further, it exhibits low emissivity (ε3-5μm = 0.15 and ε8-14μm = 0.18) in the dual infrared atmospheric window, which reduces the infrared lock-on range by 59.6%/49.8% in the mid/far-infrared band at high temperatures (573 K). The infrared camouflage performance calculated from the radiation temperature of CNTs@PAA/AFP coatings is enhanced to over 65%, which is at least 4 times greater than that of its substrate. In addition, the CNTs@PAA/AFP coating achieves high microwave absorption (RLmin = -42.46 dB) and an effective absorption bandwidth (EAB = 7.43 GHz) in the microwave band (S-Ku bands) due to the enhancement of interfacial polarization and conductive losses. This study may introduce new insight and feasible methods for multispectral manipulation, electromagnetic signal processing, and thermal management via bioinspired structural design and fabrication.

Super-slippery silicone-based gel coating with a regenerative oil layer for long-term prevention of surface contamination

Polymer-based gel-type coatings, in which oil molecules are absorbed within polymer networks, have drawn attention as functional coatings to address fouling problems. However, surface drought caused by lubricant depletion limits the longevity of conventional gel-type coatings. In this study, a super-slippery long-chain entangled polydimethylsiloxane (LEP) gel that can self-regenerate a low-viscosity oil layer is proposed to enhance its long-term anti-fouling performance in both indoor and marine habitats. The proposed LEP gel coating can effectively prevent contamination from numerous liquids and protect aluminum surfaces from corrosion in seawater. Even when it was incubated with Porphyridium purpureum, marine red algae that readily stick to the surface, no biofilm was formed on the coated samples for 37 weeks. In field tests, no biological adhesion was observed on the coating surface which was applied to port structures and left for two summer months. This enhanced anti-contamination performance is mainly attributed to the dual protective barrier comprising the underlying polymer layer and regenerative oil layer. Due to special property of continuous self-regeneration of oil layer, the proposed LEP gel surface demonstrates much enhanced sustainability, compared to conventional gel-type coatings. Consequently, the long-term anti-contamination performance of the super-slippery LEP gel coating would pave the way for novel approach to its practical applications.

Growth and Redox Properties of Boron on Al(111): Competing Affinities in the Case of Honeycomb AlB2.

The complexity of the geometric and electronic structure of boron allotropes is associated with the multicentric bonding character and the consequent B polymorphism. When growth is limited to two-dimensions (2D), the structural and electronic confinement yields the borophenes family, where the interaction with the templating substrate actually determines the stability of inequivalent boron phases. We report here a detailed study of the growth of the honeycomb AlB2 phase on Al(111), followed by an investigation of its oxidation and reduction properties. By means of a combined experimental and theoretical approach, we show that the structure of the B/Al interface is affected by the complex interplay between B, Al, and common reactive agents like oxygen and hydrogen. While kinetic effects associated with diffusion and strain release influence the AlB2 growth in vacuo, Al, B, O, and H chemical affinities determine its redox behavior. Reduction with atomic hydrogen involves the B layer and yields an ordered honeycomb borophane H/AlB2 phase. Instead, oxidation takes place at the Al interface, giving origin to buried and 1D surface aluminum oxide phases.

A novel Pd-doped perovskite-based LaCo0·9Pd0·1O3–Ba/Al2O3 catalyst enhances NOx to ammonia reaction

The effect of Pd doping on the NOx removal efficiency and NH3 selectivity was studied over lean NOx trap LaCo1-xPdxO3-Ba/Al2O3-type catalysts. Two catalysts were prepared by the sequential impregnation of 15 wt% of LaCo1-xPdxO3-type perovskites and 20 wt% of barium over alumina. The results of X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, temperature programmed techniques, UV–vis diffuse reflection absorption spectroscopy, and X-ray photoelectron spectroscopy demonstrated that perovskite and barium grains uniformly distribution over the alumina surface. Cobalt partial substitution by palladium changed the chemical coordination environment, thus leading to the redox properties of perovskites getting different. Moreover, the LaCoO3–Ba/Al2O3 catalyst exhibited a high reduction on NOx by H2 between 450 and 550 °C. Whereas Pd-doped LaCo0·9Pd0·1O3–Ba/Al2O3 catalyst decreased the best activity interval around 100 °C, as well as improved the NH3 selectivity. The NOx reduction conversion of the LaCo0·9Pd0·1O3–Ba/Al2O3 catalyst increased significantly from 72.9% to around 100% at H2/NO ratio = 1, and the production of NH3 was increased from 20.1% to 58.6% at H2/NO ratio = 3.

Characterization and synthesis of high permeance SSZ-13 membranes to separate CO2 from CH4 for biogas upgrading

Small-pore zeolites, such as CHA (0.38 nm), have pores that are comparable to the size of CH4 but larger than the size of CO2. As a result of the combination of diffusion and adsorption, these membranes are projected to have strong CO2/CH4 selectivity and CO2 permeance. During this work, SSZ-13 CHA membranes were synthesized, evaluated, and characterized by X-ray Diffraction, Field-Emission Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy, Solid-State Nuclear Magnetic Resonance, and Thermogravimetric Analysis. Synthesized membranes on the inner surface of single channel alumina supports with a pore size of 200 nm and a length of 105 mm and an active membrane area of ∼17 cm2 showed an ideal permselectivity for CO2/CH4 of 122 (in the single gas permeation measurement) and a CO2 permeance of 36.1 × 10−7 [mol/(m2 s Pa)] and CO2/CH4 selectivity of 173 and a CO2 permeance of 6.5 × 10−7 [mol/(m2 s Pa)] for equimolar CO2 − CH4 mixture. According to the results, the membranes are capable of separating CO2 from natural gas and upgrading biogas for industrial purposes.

Preparation and properties of micro-arc oxidation ceramic coatings using machine vision technology

In this paper, a machine vision system is combined with non-immersion micro-arc oxidation (MAO) technology, using color as a visual feature, and automatically determining the MAO process through a self-developed color image segmentation program for HSV channel. The robotic arm accurately regulates the machining position and duration. Dense ceramic oxide coatings of similar quality to the artificially prepared coatings were successfully prepared on aluminum (Al) surface. The surface morphology and elemental composition of the samples were characterized using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The performance of the coatings was tested through thickness tests, hardness tests, and roughness tests. The tribological properties were tested by friction experiments, and its corrosion resistance was tested by electrochemical corrosion tests. The results confirm the effectiveness of a machine vision system for MAO process control, which is capable of preparing high-quality coatings comparable to manual operations. This not only solves the need for precise film formation in different application scenarios, but also provides a more efficient, controllable and innovative solution for the MAO process.

Biomimetic papilla texture by femtosecond laser for high-strength CFRTP/A6061-T6 FSSW hybrid structures

The lightweight design concept in structural applications has generated interest in hybrid structures of carbon-fiber-reinforced thermoplastics (CFRTP) and metals as attractive structure components. However, these hybrid structures face challenges due to the significant differences in physical and chemical properties between CFRTP and metals, resulting in limited strength and rendering them unsuitable for advanced transportation. To address these limitations, the current research focuses on creating a biomimetic texture on A6061-T6 (6061) surfaces using femtosecond laser to manufacture high-strength hybrid structures, inspired by organismal body surfaces. The CFRTP and 6061 were joined by friction stir spot welding (FSSW). The femtosecond laser treatment produces double-scale roughness on 6061 surfaces and causes carbon to absorb into alumina. These changes in physical and chemical structures enhance the compatibility between 6061 and CFRTP. The biomimetic rough aluminum surface creates effective mechanical interlock at the interface with CFRTP, preventing the initiation and propagation of fracture cracks. The presence of absorbed carbon enhances the Al-O covalency, which influences the bonding behavior at CFRTP/6061 interfaces. The improved compatibility, mechanical interlock, and enhanced bonding behavior synergistically strengthen the joint strength of CFRTP/6061 hybrid structure modified by the biomimetic papilla structure. Current biomimetic design strategy inherits the remarkable natural wisdom and is expected to provide valuable insights for the development and application of CFRTP/metal hybrid structures.

Predicted Fracture Tendency of Naturally Occurring Aluminum Surface Coatings under Tensile Loading.

Naturally occurring coatings on aluminum metal, such as its oxide or hydroxide, serve to protect the material from corrosion. Understanding the conditions under which these coatings mechanically fail is therefore expected to be an important aspect of predictive models for aluminum component lifetimes. To this end, we develop and apply a molecular dynamics (MD) modeling framework for conducting tension tests that is capable of isolating factors governing the mechanical strength as a function of coating chemistry, defect morphology, and variables associated with the loading path. We consider two representative materials, including γ-Al2O3 and γ-Al(OH)3 (i.e., oxide and hydroxide), both of which form readily as aluminum surface coatings. Our results indicate that defects have a significant bearing on the strength of aluminum oxide, with grain boundaries serving to reduce the strain at failure from εzz = 0.300 to 0.219, relative to perfect single crystal. Our simulations also predict that porosity lowers the elastic stiffness and yield strength of the oxide. Relative to perfect crystal, we find porosity factors of 5%, 10% and 20% decrease the yield stress by 26%, 36% and 53%, respectively. MD predicts that perfect hydroxide and oxide single crystal have respective strains at failure of 0.08 and 0.31 under tensile uniaxial strain loading, and that the corresponding yield stresses are respectively 1.6 and 11.1 GPa. These data indicate that the hydroxide is substantially more susceptible to mechanical failure than the oxide. Our results, coupled with literature findings that indicate hot and humid conditions favor formation of hydroxide and defective oxide coatings, indicate the potential for a complicated dependence of aluminum corrosion susceptibility and stress corrosion cracking on aging history.

Surface Defect Detection of Aluminum Profiles Based on Multiscale and Self-Attention Mechanisms.

To address the various challenges in aluminum surface defect detection, such as multiscale intricacies, sensitivity to lighting variations, occlusion, and noise, this study proposes the AluDef-ClassNet model. Firstly, a Gaussian difference pyramid is utilized to capture multiscale image features. Secondly, a self-attention mechanism is introduced to enhance feature representation. Additionally, an improved residual network structure incorporating dilated convolutions is adopted to increase the receptive field, thereby enhancing the network's ability to learn from extensive information. A small-scale dataset of high-quality aluminum surface defect images is acquired using a CCD camera. To better tackle the challenges in surface defect detection, advanced deep learning techniques and data augmentation strategies are employed. To address the difficulty of data labeling, a transfer learning approach based on fine-tuning is utilized, leveraging prior knowledge to enhance the efficiency and accuracy of model training. In dataset testing, our model achieved a classification accuracy of 97.6%, demonstrating significant advantages over other classification models.

Aluminum-silver nanoalloys supported on a nitrogen-doped edge of bilayer graphite as thermal engineering device for H2 storage

Molecular dynamics simulations suggest that doping nitrogen in the edges of bilayer graphite as a support material near room temperature significantly enhances hydrogen storage on aluminum nanoparticles compared to silver nanoparticles. This finding underscores aluminum's potential for industrial hydrogen storage applications. Hydrogen storage on aluminum and silver nanoparticles, and aluminum-silver nanoalloys supported on bilayer graphite (BG) and nitrogen-doped bilayer graphite edges (NDBGE) exhibits a diminishing trend with increasing temperature. Particularly noteworthy is the observation that higher concentrations of aluminum doping in silver-aluminum nanoalloys, when supported on NDBGE, lead to a decrease in hydrogen storage across various temperatures. Using NDBGE as a supporting material leads to a substantial increase in hydrogen storage on aluminum-silver nanoalloy surfaces, achieved through thermal engineering within the temperature range: 300 K to 350 K. Here, the combination of thermal engineering and nitrogen doping in bilayer graphite edges provides a viable approach to engineer larger aluminum nanoparticles, aligning with international standards criteria such as those set by the United States Department of Energy (SUSDOE) for hydrogen storage. Bilayer graphite, when utilized as a support for aluminum metals, facilitates thermal engineering across a broad temperature range, aligning with SUSDOE's objectives. Concerning the diffusion coefficient of hydrogen, there is no consistent trend observed as a function of temperature for aluminum and silver nanoparticles supported on NDBGE. However, in the case of silver-aluminum nanoalloys supported on NDBGE, hydrogen diffusion increases with temperature. The general trend for hydrogen diffusion on aluminum surfaces versus temperature agrees with available experimental data. Current simulation results predicting a decrease in hydrogen adsorption on aluminum surfaces with increasing temperature also confirm available experimental findings.

Experimental investigation of condensation heat transfer on vertically inclined grooved aluminium surfaces

This study details the experimental investigation of surface condensation heat transfer on vertically inclined aluminium surfaces with simple modifications. A bespoke experimental apparatus was constructed to control the saturation conditions inside the condensation chamber where the test surface is located. The degree of subcooling of the test surface was precisely controlled by an external heat exchanger. The meter bar technique was used to evaluate the condensation heat flux. Using distilled water as the working fluid and a plane aluminium test surface as the baseline case, the experimental apparatus was validated by comparison of the determined heat transfer coefficient with Nusselt’s model of filmwise condensation on a vertical plane surface, where an excellent agreement was obtained. 7 different aluminium test surfaces were subsequently investigated, each one modified with grooves measuring 0.5mm by 0.5mm (height and width), with a consistent spacing of 0.5mm between them. Groove angles relative to the vertical axis of 0° (180°), 30°, 45°, 60°, 90°, 120°, and 150° were investigated, where grooves were symmetrically mirrored at the centre of each test surface. Results highlighted a significant influence of groove angle on the heat transfer coefficient, with the best-performing sample (150˚) producing a maximum enhancement of 45% and an average enhancement of 34% compared to the baseline test surface over the respective range of subcooling.

Realizing the excellent oxidation resistance of an environmental barrier coating through aluminum surface modification

Realizing the excellent oxidation resistance of an environmental barrier coating through aluminum surface modification

Improved stability of aluminum surface plasmon resonance sensor by protective gold layer

The surface plasmon resonance (SPR) sensing in the ultraviolet (UV) region, achieved through the optimization of aluminum (Al) film conditions, has attracted attention due to its heightened energy levels and more plentiful molecular electronic transitions compared to the visible region. In this research, the stability of the UV-SPR sensor is improved by applying a protective thin layer of gold (Au) onto the Al film. This reduces spectral alterations observed when the Al film was uncoated in water pre and post flow system measurements. This exploration presents the initial experimental confirmation of the reliability of Al-Au bilayer coatings as SPR sensors in the UV region, highlighting advancements in UV-SPR sensor technology.

A study of pomegranate peel extract effect on corrosion inhibition performance on aluminum in HNO3 solution

Green corrosion inhibitors have an important role in reducing the corrosion rate of metals and the effects of toxic chemicals in the environment. In this study, the inhibition effect of pomegranate peel extract (PPE) with concentration of 0.5, 1, 1.5, 2, 2.5 and 3 g/L on the aluminum 1050 alloy corrosion behavior in the nitric acid solution investigates using the weight loss, electrochemical techniques, scanning electron microscope (SEM), atomic force microscope (AFM), contact angle images, gas chromatography-mass spectrometer (GC-MS) analysis, fourier transform Infrared spectroscopy (FTIR) and ultraviolet radiation (UV-IR). And, the (UV-IR), (GC-MS), and FTIR results confirm the presence of many organic compounds (Containing the N, S, and O atoms), which are responsible for inhibitor performance and absorption phenomena. Meanwhile, the electrochemical impedance results (EIS) indicate that the double layer capacity decreases and the corrosion resistance (Corrosion current density (icorr) from 0.128 to 0.009 mA/cm2) increases with the increase of the inhibitor concentration (The inhibition efficiency increased with increasing the inhibitor concentration from % 54.29 to the % 92.58 at (1–3 g/L). In addition, the corrosion current density decreases with the increase of the inhibitor concentration using the potentiodynamic polarization (PDP) test. However, the corrosion rate enhances with increasing the temperature. From the other hand, quantum chemical (QC) calculation and molecular dynamics (MD) simulation perform to investigate the theory of the adsorption mechanism. According to these studies, the adsorption of PPE on the aluminum 1050 alloy surface is agreement with the langmuir isotherm and as a result it is a mixed-type inhibitor. In final the SEM and AFM results show that the corrosion rate of the aluminum 1050 alloy surface is significantly reduced after the addition of the inhibitor to the corrosive environment. Furthermore, the contact angle image shows that the inhibited aluminum surface has a hydrophobic property in an aqueous solution. And, the QC calculation and MD simulation clarify well the thin layer formation due to the good adsorption of inhibitor (PPE) on the surface of aluminum 1050 alloy in the nitric acid solution, theoretically. It is concluded that PPE will inhibit the surface of aluminum against the corrosion agents in acidic environment and can use as a green inhibitor.

Analisis Metode Anodizing Aluminium dengan Variasi Kuat Arus sebagai Material Velg Kendaraan

Aluminum Alloy 6061 is widely used in various engineering applications, including automotive vehicle wheels. The selection of aluminum alloy wheels involves aspects such as corrosion resistance. To enhance corrosion resistance, there are several methods, one of which is anodizing. Anodizing is a process that involves an electrolytic coating process that transforms the surface of aluminum into aluminum oxide (Al2O3), which the main process of aluminum anodizing requires a solution of sulfuric acid, chromic acid, or a mixture of sulfuric acid and oxalic acid. The sulfuric acid used must be concentrated acid, and acid is an oxidizing substance. The thickness of the oxide is approximately twice the thickness of the lost aluminum. The purpose of this research is to determine the characteristic such as surface roughness values, corrosion rates, and changes in morphology in Aluminum 6061 after undergoing anodizing. In this study, various current strengths were used, namely 0.75 Amperes, 1.5 Amperes, 2.25 Amperes, and 3 Amperes. The highest surface roughness value was obtained at 0.447 μm in the third specimen of the 0.75 Ampere variation, while the lowest was 0.075 μm in the first specimen of the 3 Ampere variation. The highest corrosion rate was observed in the 0.75 Ampere variation, with a rate of 17.724004 mpy, and the lowest was 0.0731653 mpy in the 3 Ampere variation. SEM results show that, in general, Aluminum 6061 tends to have a bright gray color, which is a surface that has been coated by cathode.

Prediction of thermal shock induced cracking in multi-material ceramics using a stress-energy criterion

Impact of residual stresses on the thermal shock resistance of alumina–zirconia multi-layer ceramics is investigated within the framework of finite fracture mechanics, using astress-energy criterion. The critical temperature difference (ΔTc) for crack formation is strongly dependent on the magnitude of residual stress and the material’s strength. The predicted minimal spacing between cracks, critical time for crack initiation, and initial depth of the induced cracks are compared and discussed for different designs. An increase of up to ∼40 % in ΔTc is predicted for multi-material ceramics with athin alumina surface layer with compressive stresses, compared to bulk reference alumina.

Ignition and combustion characteristics of aluminum-based fluorine-containing composite powder

To improve the combustion characteristics of micron-sized aluminum (Al) powder, a composite powder was prepared by doping a small amount (15 wt%) of magnesium fluoride (MgF2), polytetrafluoroethylene (PTFE), and fluorinated graphite (FG) into the aluminum powder through solution dispersion method. The physical phase composition, micro morphology, thermal reactivity, and combustion performance of the composite powders were also characterized. The findings suggest that the promoting effect of the three fluorides on aluminum combustion can be ranked in the following descending order: FG > PTFE > MgF2. The fluorides can to erode the Al2O3 shell layer directly, thus creating cracks and reaction pathways for the Al core enclosed within the shell. Moreover, the gasification of AlF3 within the combustion products can escape from the surface of Al particles and promote the oxidation combustion of the exposed aluminum, which enhances the diffusion reaction on the active aluminum surface.

Effect of surface microporous copper coatings on corrosion properties of graphene-reinforced aluminium matrix composites

ABSTRACT It is difficult to assess the temperature and pressure resistance of the existing soluble bridge plug seal ring used in fracking for shale gas reservoirs, to go with its high plasticity and good solubility. To overcome this shortcoming, aluminium matrix composites with the addition of 0%, 0.5% and 1.0% of graphene were prepared by spark plasma sintering. Uniaxial static pressure test results show that the composite has the maximum compressive strength and compression ratio when the graphene content is 0.5%. Microporous copper coatings were prepared on graphene/1070 aluminium surface by electroless plating. The synergistic effect of the surface microporous copper coating and the internal graphene on the corrosion performance of 1070 aluminium alloy was analysed by the weight loss and electrochemical methods. The results showed that the surface microporous copper coatings could significantly improve the uniform corrosion rate and pitting depth of graphene/1070 aluminium.

Strengthening the bonding interfaces of carbon reinforced aluminum laminate by slot structure

AbstractA reliable strategy to enhance the bonding ability in carbon reinforced aluminum laminates (CARALL) is proposed, which is based on the mechanical interlocking effect generated by the surface slot structure of aluminum alloy enhances the structural interface between fibers/resins and aluminum alloy. The characteristic of slot structure is determined, and the strengthening mechanism of bonding interfaces is revealed. The CARALL samples with slot structure are fabricated via an hot pressing process. The micro texture morphologies, mechanical, interlayer bonding properties under different conditions are studied. The results indicate that forming a slot structure on the aluminum surface is beneficial for improving the interfacial bonding performance. Compared with the non‐slotted structure, the interlayer type II fracture toughness of the slotted structure is increased by 112.99%. The slotted structure can reduce the defects at the interface between the layers and improve the interface bonding force. In this work, the interlaminar shear strength (ILSS) of the slotted structure sample was 27.08% higher than that of the non‐slotted structure sample.Highlights A slotted structure was proposed to solve the problem of insufficient bonding strength. A slotted structure consistent with the direction of adjacent fibers is designed. The interlayer type II fracture toughness of the slotted structure is increased by 112.99%. The final crack propagation of the slotted structure sample is reduced by 40%. The final failure area of the slotted structure sample is reduced by 53.85%.

Enhanced marine biofouling and corrosion resistance through springtails-inspired papillate-like micropillar arrays surface modified by antimicrobial peptide

Marine biological fouling has a serious impact on artificial facilities, and traditional antifouling coatings are not beneficial to green development, which lead to the urgent to develop green strategies that can effectively prevent fouling. In this study, an innovative confluence of physical and biological approaches was employed to mitigate the harm caused by biofouling on a material substrate. Firstly, a hierarchical microstructured morphology was prepared on an aluminum surface by reactive ion etching and characterised. The antibacterial peptide, A-2S, was surface modified with dopamine as a coupling agent to produce a physico-biological synergistic antifouling surface. X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, and electrochemical experiments were then used to analyse the binding effect and corrosion resistance performance. A-2S was successfully modified on the sample surface and exhibited good corrosion resistance with a corrosion inhibition efficiency of 86.57 %. Compared to a bare aluminum plate, the microstructure surface has a certain inhibitory effect on fouling organisms, and the antifouling performance decreases over time. In contrast, the antimicrobial peptide synergistic surfaces demonstrated superior durable antifouling performance. Compared with the 50 % of the antifouling performance on the microstructure surface, the synergistic surface has a unique contact point effect of the microstructure and excellent antibacterial and bactericidal properties of antimicrobial peptides, resulting in a surface antifouling performance of over 80 %. The synergistic modification method enhanced the corrosion resistance of the material and reduced the adhesion of fouling organisms, mitigating the harm caused by biofouling on the marine equipment substrate.