Aluminum Surface Research Articles

Spectroscopic and Microscopic Characterization of Microbial Biofouling on Aircraft Fuel Tanks.

Avoiding microbial contamination and biofilm formation on the surfaces of aircraft fuel tanks is a major challenge in the aviation industry. The inevitable presence of water in fuel systems and nutrients provided by the fuel makes an ideal environment for bacteria, fungi, and yeast to grow. Understanding how microbes grow on different fuel tank materials is the first step to control biofilm formation in aviation fuel systems. In this study, biofilms of Pseudomonas putida, a model Gram-negative bacterium previously found in aircraft fuel tanks, were characterized on aluminum 7075-T6 surfaces, which is an alloy used by the aviation industry due to favorable properties including high strength and fatigue resistance. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX) showed that extracellular polymeric substances (EPS) produced by P. putida were important components of biofilms with a likely role in biofilm stability and adhesion to the surfaces. EDX analysis showed that the proportion of phosphorus with respect to nitrogen is higher in the EPS than in the bacterial cells. Additionally, different morphologies in biofilm formation were observed in the fuel phase compared to the water phase. Micro-Fourier transform infrared spectroscopy (micro-FTIR) analysis suggested that phosphoryl and carboxyl functional groups are fundamental for the irreversible attachment between the EPS of bacteria and the aluminum surface, by the formation of hydrogen bonds and inner-sphere complexes between the macromolecules and the aluminum surface. Based on the hypothesis that nucleic acids (particularly DNA) are an important component of EPS in P. putida biofilms, the impact of degrading extracellular DNA was tested. Treatment with the enzyme DNase I affected both water and fuel phase biofilms─with the cell structure disrupted in the aqueous phase, but cells remained attached to the aluminum coupons.

Comparison of oxidation behavior of NiCrAlY coatings before and after surface aluminizing modification

Surface aluminizing of the coating can effectively balance its high-temperature oxidation resistance and mechanical properties, while also minimizing the rumpling in the oxide layer caused by the phase transition. In this study, NiCrAlY coatings prepared using arc ion plating were aluminized with different Al content, which was reflected by the thickness of the Al layer deposited via magnetron sputtering. The effects of the aluminizing treatment on high-temperature oxidation resistance was investigated. After 150 h of oxidation, the original coating exhibited complete failure, evident through the flaking of the oxide layer and severe internal oxidation. The aluminizing treatment delayed the formation of an Al-depletion zone within the coating, which effectively prolonged the high-temperature durability of the coatings. Moreover, the different levers of Al content also influenced the thickness of the subsequently generated oxide layer.

Multifunctional Aluminum Pre-treatments from End-Functionalized Phosphonic Acid Self-Assembled Monolayers.

Aluminum alloys are used in advanced engineering applications as they possess a combination of favorable properties, including high strength, lightweightness, good corrosion resistance, machineability, and recyclability. Such applications often require forming the sheets into the final components, which is typically aided by an oil-based lubricant, followed by joining them using adhesives, which is hampered by residual lubricant. In this work, aluminum surfaces were modified with different self-assembled monolayers (SAMs), with the goal of significantly reducing the amount of lubricant while simultaneously improving friction properties, forming, and bonding performance. Our results show that SAMs terminated with hydrophilic and nucleophilic end groups give rise to high-energy surfaces with wetting properties that are stable over time. These surfaces showed significantly improved surface wetting by the lubricant, which in turn resulted in an improved forming performance at reduced lubricant coat weights. Moreover, the nucleophilic SAM termination provided outstanding performance in adhesive bonding tests under corrosive conditions.

Numerical erosion prediction of aluminum induced by cavitating jet using an Eulerian–Lagrangian method

Cavitation-induced erosion in pump machinery is a significant issue that leads to material loss and increased operating costs. This study develops a numerical method based on an energy balance approach to address the risk of cavitation erosion. Compared with other published methods, three improvements are made. Firstly, it assumes that the local instantaneous pressure is the driving force behind cavity collapse, rather than the far-away ambient pressure field. Secondly, it counts erosion only at the moment that the released shock wave is strong enough to cause surface damage. Thirdly, an Eulerian–Lagrangian method is introduced to simulate multiscale cavitation, in which the volume of fluid (VOF) method and a discrete bubble model (DBM) are combined to reproduce resolvable water-vapor interfaces and unresolvable discrete bubbles, respectively. The developed numerical modeling framework is validated by predicting the erosion of pure aluminum surface caused by a cavitating jet, and it is shown that the simulated erosion region fits well against the experimental results. Additionally, appropriate model coefficients of the erosion prediction method are introduced to achieve quantitative prediction of material mass loss, and the detailed erosion behavior is discussed.

Engineering a robust, multifunctional superhydrophobic/oleophobic microporous aluminum surface via a two-step chemical etching process

Surfaces with unique wettability properties are gaining attention for their widespread applications. Particularly, superhydrophobic surfaces, known for their remarkable water-repellent properties and low adhesion, have gained substantial interest in recent years owing to their versatile applications. Despite their versatile applications, the durability of such surfaces faces challenges like mechanical abrasion, chemical deterioration, and environmental factors, limiting their effectiveness in real-world scenarios. In this study, we successfully fabricated a mechanically robust, cost-effective, and easy-to-process superhydrophobic surface on an aluminum substrate using a two-step chemical etching process. Initially, the hierarchical microporous (HMP) structure was created through chemical etching, followed by the deposition of a self-assembled layer of PFOTS onto the fabricated aluminum substrate, attaining superhydrophobic and oleophobic properties. The surface exhibits remarkable superhydrophobicity with a water contact angle of 162°, while coupled with oleophobic characteristics against a wide spectrum of oils with surface tensions ranging from 21.5–63.3 mN m − 1. We conducted comprehensive characterizations of surface morphology and chemical composition, while also investigating the impact of surface morphology on wettability, physicochemical stability, and antibacterial properties. Mechanical testing revealed that the surface maintained its superhydrophobicity even after undergoing linear abrasion for a distance of 120 cm under an applied pressure of 12.25 kPa. Furthermore, the surface displayed self-cleaning, and anti-fouling, along with significant antibacterial properties against Staphylococcus aureus bacteria, creating a 23 mm zone of inhibition. We believe the proposed method will inspire the fabrication of large-scale superhydrophobic metallic surfaces endowed with multifunctional properties, making them highly suitable for a wide range of industrial applications.

Assessment of temperature and time on the survivability of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV) on experimentally contaminated surfaces.

Fomites might be responsible for virus introduction in swine farms, highlighting the importance of implementing practices to minimize the probability of virus introduction. The study's objective was to assess the efficacy of different combinations of temperatures and holding-times on detecting live PRRSV and PEDV on surfaces commonly found in supply entry rooms in swine farms. Two PRRSV isolates (MN 184 and 1-4-4 L1C variant) and one PEDV isolate (NC 49469/2013) were inoculated on cardboard and aluminum. An experimental study tested combinations of four temperatures (20°C, 30°C, 40°C, and 50°C) and six holding-times (15 minutes, 60 minutes, 6 hours, 12 hours, 24 hours, and 36 hours) for the presence of the viruses on each surface type. After virus titration, virus presence was assessed by assessing the cytopathic effects and immunofluorescence staining. The titers were expressed as log10 TCID50/ml, and regression models; half-lives equations were calculated to assess differences between treatments and time to not detect the live virus. The results suggest that the minimum time that surfaces should be held to not detect the virus at 30°C was 24 hours, 40°C required 12 hours, and 50°C required 6 hours; aluminum surfaces took longer to reach the desired temperature compared to cardboard. The results suggest that PRRSV 1-4-4 L1C variant had higher half-lives at higher temperatures than PRRSV MN 184. In conclusion, time and temperature combinations effectively decrease the concentration of PRRSV and PEDV on different surfaces found in supply entry rooms in swine farms.

Robustness defect detection: Improving the performance of surface defect detection in interference environment

In industrial production environments, the performance of surface defect detection methods for products is affected by disturbances in the equipment, manufacturing processes, and the environment, resulting in poor robustness of the training model. In this paper, an improved defect detection method based on feature extraction fusion and dynamic label assignment is proposed. Three improved network structures, i.e., the adaptive feature recognition convolution (AFRC), path aggregation balanced feature pyramid, and dynamic label assignment, are proposed for the feature extraction, feature fusion, and detection phases of the existing Faster RCNN model, respectively. The AFRC is employed to improve the feature extraction ability of the model for irregular defects, the path balance feature pyramid is utilized to enhance the recognition ability of the model for different levels of feature maps, and the dynamic label assignment is employed to improve the quality of the candidate frames. Under disturbed environments, the results of the proposed improvements outperform the benchmark faster RCNN model in terms of average precision (AP) by 4.1%, 3.7%, and 4.2% on an aluminum surface defect dataset and by 1.8%, 2.2%, and 3.7% AP on a magnetic tile surface defect dataset. The experimental results demonstrate that the proposed scheme effectively improves the robustness of the baseline model in environments with various disturbances.

Solution blending preparation of polyurethane/graphene composite: Improving the mechanical and anti-corrosive properties of the coating on aluminum surface

Graphene-based polyurethane composites (PU/G) are prepared by a simple solution blending method to disperse defect-free graphene flakes (prepared via liquid phase exfoliation process) into the polyurethane matrix. The PU/G composite with 1 wt% of graphene flakes performs the significant improvement (∼50 %) of the impact strength (124 kg.cm) and adhesion behavior (∼2.3 MPa) with respect to that of pristine PU. The PU/G coating with 2 wt% of graphene achieves the highest long-term anti-corrosion performance after 150 immersed days in 3 wt% NaCl solution (with the stable impedance modulus of ∼2.7 × 1010 Ω.cm2) or after 2500 h of salt spray exposure in 5 wt% NaCl solution (no corrosive traces detected on aluminum substrate).

Wetting of Al2O3 by Cu-xTi alloys at 1373 K

Wetting of Al2O3 by molten Cu-xTi alloys with wide composition range was deeply studied. The results show that the precipitation of TiO at the interface is depended on the Ti concentration in the alloys as well as the oxygen partial pressure in the atmosphere. When Ti concentration is lower than the critical Ti concentration, the wettability of the system is mainly determined by the precipitated TiO and the adsorption of Ti-O clusters at the interface; conversely, it is mainly determined by the adsorption of Ti-O clusters on the surface of alumina. For the spreading dynamics of: Cu-Ti alloys on the sapphire surface, the existence of two stages were observed: firstly, an initial fast spreading stage, which is mainly limited by the reaction rate of TiO precipitation; followed by a later slow spreading stage, which is mainly limited by the precipitation reaction of Al2O, and exhibits a stepwise spreading characteristic.

Hydrogen and DA bond-based self-healing epoxy-modified polyurea composite coating with anti-cavitation, anticorrosion, antifouling, and strong adhesion properties

Cavitation, corrosion, and fouling are critical factors that significantly impact the performance of power components in large cargo ships. To address these issues, a composite coating called epoxy-modified polyurea (PUE-FD) has been developed with reproducible self-healing properties. The incorporation of functionally reduced graphene oxide (FrGO) with multiple hydrogen bonds in the coating led to a notable increase of 5.6 MPa in the tensile strength of PUE-FD. This enhancement was accompanied by excellent resistance to cavitation, as evidenced by a mere 2.8 mg mass loss after 60 h of continuous cavitation. Furthermore, the inclusion of FrGO exhibited an exceptional barrier effect, providing PUE-FD with superior corrosion protection. The |Z|0.01 Hz value of PUE-FD was 9.01 × 109 Ω cm2 after 15 days of immersion in 3.5 wt% NaCl solution. Additionally, the synergistic effect of 2-octyl-4,5-dichloroisothiazolinone (DCOIT) and FrGO resulted in remarkable antifouling performance, with a bacterial removal rate exceeding 99.4 % and a microalgae removal rate of up to nearly 100 % for PUE-FD. PUE-FD also demonstrated remarkable photothermal self-healing ability, achieving a self-healing efficiency of 89 % within just 60 s of near-infrared irradiation. Moreover, the presence of hydrogen bonds in FrGO contributes to the excellent adhesion properties of PUE-FD, resulting in adhesion strengths of more than 10 MPa on copper, stainless steel, and aluminum surfaces. This work presents new inspirations for the preparation of multifunctional coatings with anti-cavitation, anticorrosion, antifouling, and self-healing properties.

Enhancing the Electromagnetic Shielding Effectiveness of Alumina (AL2O4) by Coating with Nano Gold (AuNp)

With the rapid development of Industry 4.0 and 5G technologies, new challenges are emerging and among them is electromagnetic interference (EMI). EMI may not only affect the performance of the devices operating around it but can also harm human health. Therefore, the issue of EMI shielding is becoming increasingly relevant. EMI shielding is most effectively achieved by using materials with high surface conductivity. This theoretical starting point provided the motivation to increase surface conductivity. To achieve this, in this study, electromagnetic shielding effectiveness (SE) of pure alumina (Al2O4) and nanogold-coated alumina is investigated, with the aim of enhancing the understanding of effective EMI shielding strategies.Through a series of carefully designed experiments and in-depth analysis, a significant finding emerges: nanogold-coated Al2O4 exhibits superior shielding performance, surpassing the effectiveness of its pure counterpart. The study evaluates key SE factors, including reflection loss and absorption loss, and highlights the remarkable improvement achieved by applying nanogold coatings to the aluminium oxide surface. In addition, this research also pioneers the combination of SE assessment with material characterization using cutting-edge techniques such as energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and X-ray diffraction (XRD). This multidisciplinary approach provides valuable insights into the electromagnetic interaction mechanisms responsible for the enhanced shielding performance of nanogold-coated AL2O4. The results of this study emphasize its potential significance in modern electronic systems, while also highlighting the lack of existing studies that combine SE evaluation with comprehensive material characterization, thereby contributing to the advancement of electromagnetic shielding research.

SO3-COF@Al2O3 modified cathode electrode materials enhance the cycling ability of lithium sulfur batteries.

Herein, a covalent organic framework (SO3-COF) containing sulfonic acid groups has been developed on the surface of alumina by a one-step method, labeled as SO3-COF@Al2O3. The experimental results show that SO3-COF@Al2O3 can effectively inhibit the shuttle effect of soluble lithium polysulfide (LiPSs) in LSBs after loading the active material sulfur, and exhibits better cycling behavior than the initial polymer SO3-COF. The initial discharge specific capacity of this electrode material at 0.05C is as high as 1141 mA h g-1, and the capacity can be maintained at 466 mA h g-1 after 500 cycles with a capacity decay rate of 0.08% per cycle.

Investigating the behaviour of NaCl brines and hydrocarbons in porous alumina using low-field NMR relaxation and diffusion methods.

The behaviour of multiple fluid phases within a porous medium is hard to predict. NMR measurements offer an excellent tool to probe such systems in a fast and non-invasive way. Such systems can be relevant to hydrocarbon recovery, catalysis, and CO2 and H2 geo-storage, among others. Since electrolyte solutions are always present in subsurface reservoirs, understanding their behaviour within porous media is highly important. In this study, we use NMR relaxation and diffusion methods to investigate the diffusion coefficients and strength of interactions between alumina surfaces and brines at various NaCl concentrations, focusing on the effect of salt concentration on transport and interactions within the porous structure. Furthermore, we study the spontaneous displacement of dodecane, a model hydrocarbon, from the same alumina pellets using the same brine solutions. Results show that brines of lower salinity consistently displace more dodecane in total, after soaking dodecane-saturated pellets in a brine solution for several days. This indicates that increased salt concentrations can reduce wettability towards the aqueous phase in simple metal oxide surfaces and highlights the capabilities of NMR to efficiently study such systems.

A PHYSICAL MODEL FOR THE PREDICTION OF ALUMINUM OXIDE RESIDUES

This work proposes a new model to estimate the size of oxide residues produced during the combustion of aluminum. Such large oxide residues contribute to the two-phase loss performance in solid rocket motors. The model includes two physical mechanisms: deposition of oxide smoke from the surrounding flame and oxide creation on aluminum surface by heterogeneous reactions. Parametric numerical simulations at the aluminum droplet scale are performed to estimate the rate of deposition and surface production, in order to feed a zero-dimensional model of oxide lobe growth and final oxide residue. Results are in line with available measurements with an oxide residue-to-aluminum size ratio in the range 0.5 ~ 0.8, depending on conditions. The model suggests that surface reactions are important for low pressures and small particles, while deposition prevails otherwise.

Corrosion inhibition of 8-HQ for AA5052 in 3 wt% NaCl solution in presence of trace Cu2+ ions: Electrochemical/surface studies, DFT/MD modeling

In this paper, the effect of Cu2+ ions on corrosion inhibition of 8-hydroxyquinoline (8-HQ) for AA5052 aluminum alloy in the simulated seawater solution has been studied by weight loss experiments, electrochemical measurements and surface analysis. 8-HQ inhibits the corrosion of AA5052 aluminum alloy in 3 wt% NaCl solutions very well, resulting in a positive shift in corrosion potential. The 0.01 mg/L of Cu2+ ions can deteriorate the corrosion inhibition of 8-HQ at low concentrations. This behavior is interpreted on the basis of deposition of copper by displacement on the defects of the corrosion inhibition film of 8-HQ. When the concentration of 8-HQ reached 5 mg/L, the presence of 0.01 mg/L Cu2+ ions increase the corrosion inhibition efficiency of 8-HQ by 6.27%. 8-HQ shows efficient inhibition at a relative high concentration, suggesting that the chelate formed by Cu2+ ions and 8-HQ can repair the defects of the 8-HQ inhibitive film on aluminum surface. The complex film would suppress the partial cathodic reaction and lead to the improved corrosion inhibition.

Experimental and Theoretical Investigations on the Use of Pumpkin Peel as a Sustainable Biomass Anticorrosion Agent for Aluminum in HCl Solutions

The sustainable plant‐derived biomass are now understood to be important sources for the prevention of corrosion in metallic alloys. This study examined the effect of a potential novel low‐cost, low‐toxicity inhibitor utilizing pumpkin peel extract (PPE) on aluminum corrosion hydrochloric acid 1M HCl medium. Several experimental methods were used to investigate the inhibitor effect of PPE which include, AFM‐XPS surface analysis, electrochemical studies (electrochemical impedance spectroscopy‐electrochemical frequency modulation‐potentiodynamics), and weight loss procedures. According to the weight loss results, when PPE is introduced to a 1M HCl solution, the inhibitory performance rises up to 95.42% with an increase in PPE concentration in the range of 0–300 ppm at 25°C. Potentiodynamic results showed the investigated PPE inhibitor is a mixed‐type inhibitor. Corrosion inhibition at different temperatures was also examined, and the thermodynamic activation parameters were identified. It was found that the adsorption of the inhibitor on the aluminum followed the Langmuir and kinetic isotherm models. Quantum chemical indices contributed to a greater comprehension of the inhibitory mechanism. To investigate the configurational adsorption performance of the investigated PPE on the aluminum surface, molecular dynamics (MD) simulations were carried out.

Adsorption mechanisms of decomposition species of CHON-containing explosives on aluminum surfaces.

Aluminum (Al) possesses high combustion enthalpy and is thus extensively used as the fuel additive in explosives to form aluminized explosives with excellent energy performance. In the energy release process of aluminized explosives, the adsorption of Al surfaces plays an important role in catalyzing the explosive decomposition and triggering the oxidation of themselves. However, it still remains elusive owing to the multiplicity of adsorbed substances. Herein, the adsorption mechanism of decomposition species of CHON-containing explosives on Al surfaces is studied synoptically by combining reactive molecular dynamics simulations with density functional theory calculations. The results indicate that the Al surface structure and the activity of adsorbed molecules both have an impact on adsorption. The cluster surface generally outperforms the slab one in adsorptivity due to the lower coordination number of Al atoms. Meanwhile, the more active adsorbed molecules lead to chemisorption or even dissociative adsorption, beneficial to the subsequent Al oxidation. Besides, electrons will transfer from the Al surface to the adsorbed molecules as chemisorption occurs; while the density of states of the Al surface and molecules are altered, especially for carbon oxides with significant electronic delocalization. This work is expected to deepen insights into the energy release of aluminized explosives and help provide a proposal for enhancing energy release efficiency.

An efficient strategy for the preparation of a MIL-53(Al)-NH<sub>2</sub> membranes with high ion selectivity and desalination performance

The efficient extraction of sodium (Na<sup>+</sup>) and lithium (Li<sup>+</sup>) from seawater and salt lakes is increasingly demanding due to their great application value in chemical industries. However, coexisting cations such as divalent calcium (Ca<sup>2+</sup>) and magnesium (Mg<sup>2+</sup>) ions are at the subnanometer scale in diameter, similar to target monovalent ions, making ion separation a great challenge. Here, we propose a simple and fast secondary growth method for the preparation of MIL-53(Al)-NH<sub>2</sub> membranes on the surface of anodic aluminum oxide. Such membranes contain angstrom-scale (~7 Å) channels for the entrance of small monovalent ions and water molecules, endowing the selectivities for monovalent cations over divalent cations and water over salt molecules. The resulting high-connectivity MIL-53(Al)-NH<sub>2</sub> membranes exhibit excellent ion separation performance (a selectivity of 121.42 for Na<sup>+</sup>/Ca<sup>2+</sup> and 93.81 for Li<sup>+</sup>/Mg<sup>2+</sup>) and desalination performance (a water/salt selectivity of up to 5196). This work highlights metal-organic framework membranes as potential candidates for realizing ion separation and desalination in liquid treatment.

Corrosion and microstructure evolution of ultrasonic (UaFSW), induction (i-FSW) and laser heating assisted macro and micro (μFSW) dissimilar friction stir welding and friction stir spot welding (FSSW) (surface and underwater deep sea) steels and Aluminum alloys.

Corrosion and microstructure evolution of ultrasonic (UaFSW), induction (i-FSW) and laser heating assisted macro and micro (μFSW) dissimilar friction stir welding and friction stir spot welding (FSSW) (surface and underwater deep sea) steels and Aluminum alloys.

Effect of molybdenum on the oxidation resistance of FeCrAl alloy in lower temperature (400 °C) and higher temperature (1200 °C) steam environments

The effect of 0, 1, 3 wt% Mo addition on the corrosion behavior of Fe21Cr5.5Al was studied through steam tests at 400 °C and 1200 °C. At 400 °C, Mo addition leads to non-protective Fe-Mo oxide growth on the surface, compromising protective uniform Cr oxide growth and subsequent Al2O3 layers as in the Mo-free specimen. At 1200 °C, the presence of Mo causes the spallation of the surface oxide scale. However, a thin alumina surface film was present. Current results show that Mo addition is detrimental to the corrosion resistance of FeCrAl alloy under both operational and accidental temperature scenarios.