Aluminum Surface Research Articles

Decoding the surface of a complex oxide.

Atomic force microscopy reveals the elusive structure of the aluminum oxide surface.

The shear bond strength of orthodontic brackets after surface conditioning of Zirconia, Ceramic and E. max models

The current study aims to evaluate the shear bond strength (SBS) of metal orthodontic brackets after surface conditioning by hydrofluoric acid (HF) and aluminum oxide air abrasion (Al2O3) and using two prime types and to determines the adhesive remnant index (ARI). We compared the bond strength of different types of models (full glazed zirconia, ceramic faced zirconia and E. max faced zirconia) with different surface conditioning methods for attaching metal orthodontic brackets. The study used 60 models for each material, divided into subgroups based on the type of prime material and surface preparation method. The bond strength was measured using a universal testing machine and the results were analyzed using statistical software. Shear bond strength of the Aluminum oxide was statistically (p<0.05) higher than the hydrofluoric acid and control groups in all groups (full glazed zirconia, ceramic faced zirconia and E. max faced zirconia). The Assure® Plus primer with Aluminum oxide surface treatment give rise to the highest shear bond strength than 3M™ Transbond™ XT, while there was no significant difference between Assure® Plus and 3M™ Transbond™ XT primer for both control and hydrofluoric acid groups. The highest shear bond strength was obtained with Aluminum oxide conditioning method for all types of ceramic materials used in this study.

Stoichiometric reconstruction of the Al2O3(0001) surface.

Macroscopic properties of materials stem from fundamental atomic-scale details, yet for insulators, resolving surface structures remains a challenge. We imaged the basal (0001) plane of α-aluminum oxide (α-Al2O3) using noncontact atomic force microscopy with an atomically defined tip apex. The surface formed a complex ([Formula: see text] × [Formula: see text])R±9° reconstruction. The lateral positions of the individual oxygen and aluminum surface atoms come directly from experiment; we determined with computational modeling how these connect to the underlying crystal bulk. Before the restructuring, the surface Al atoms assume an unfavorable, threefold planar coordination; the reconstruction allows a rehybridization with subsurface O that leads to a substantial energy gain. The reconstructed surface remains stoichiometric, Al2O3.

Zeolite-modified alumina-bead catalyst for hierarchical cracking of bulky molecules

A novel zeolite-modified alumina-bead catalyst (ZSM-5/Al2O3-b) was prepared via calcining zeolite-coated alumina-bead material (Al2O3-b@ZSM-5) to graft zeolitic acid sites on the alumina-bead surface. The acid catalyst proved high activity and more 8 times catalytic efficiency than the corresponding ZSM-5(5 %) + Al2O3 mechanically mixed catalyst for cracking of 1, 3, 5-triisopropylbenzene (TIPB) in the FCC simulation reactor with short contact time. The characterization results showed that the surface property of the alumina-beads has been modified and the interface connection of Si-O-Al bonds between zeolitic nanoparticles and alumina resulted in stable zeolite particles on the alumina surface and the structural stability in hot water. The excellent catalytic performances are ascribed to the decrease of diffusion limitation of reactants and intermediates and the increase of Brønsted acid sites on the ZSM-5/Al2O3-b catalyst. The grafted/modified alumina-bead catalyst can be directly used in practical catalytic cracking of large molecules without forming. This strategy can be extended to the preparation of other types of zeolite-containing catalysts and industrial applications.

Anti-corrosion and anti-icing properties of superhydrophobic laser-textured aluminum surfaces

Superhydrophobic surfaces have favorable properties in simultaneously reducing the negative effects of corrosion and ice accumulation. In this study, laser-texturing was employed as a facile and environmentally friendly surface method to prepare a surface with hierarchical roughness for subsequent grafting by immersion in an ethanol solution containing 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS-10). Various analytical techniques were utilized to assess the characteristics of the laser-textured aluminum surfaces before and after grafting, such as a contact profilometer, optical tensiometer, scanning electron microscope with energy-dispersive spectroscope, and X-ray photoelectron spectroscope. These methods were used to evaluate surface roughness, wettability, morphology, and composition. The corrosion properties were evaluated through potentiodynamic and impedance measurements in a dilute Harrison's solution (DHS) composed of 0.35 wt% (NH4)2SO4 + 0.05 wt% NaCl. Additionally, freezing delay tests at various surface temperatures were performed to assess the surface's ability to prevent the freezing of water droplets on the treated surface. The laser-textured aluminum surface, featuring micro/nanostructures and a grafted nanoscopic perfluoroalkyl silane film, exhibited outstanding superhydrophobicity and enhanced corrosion protection. The developed surface has been shown to significantly delay the onset of ice nucleation and extend the freezing delay.

Flexible fabrication of core/shell nanoparticles for tailored infrared emissivity on aluminum via femtosecond laser self-deposition.

A metal surface with controllable infrared emissivity has a wide range of applications. However, a flexible and simple fabrication method is needed. Here, a controllable femtosecond laser self-deposition technology was developed to fabricate Al@AlOx core/shell micropillars (MPs) with diverse size distribution on the aluminum surface in a single-step operation under ambient conditions. By establishing a deterministic relationship between pulse-repetition frequency (PRF) and particle size distribution (PSD), we achieved continuous control of the infrared emissivity of the surface by lower PRF, ranging from low (0.31) to high (0.93). Additionally, by using higher PRF, we attained dual-band emissivity control, featuring high emissivity in the range of 10-14 µm and near-continuous change in the range of 2.5-10 µm.

Simple hot water treatment to form nanostructures for the preparation of polyphenylene sulfide-aluminum alloy hybrids

ABSTRACT Polymer-metal hybrids (PMH) are providing the driving force for the development of automotive lightweighting. In this paper, the surface of aluminum (Al) alloy was modified by a simple, environmentally friendly surface treatment technique (hot water treatment) to form certain nanostructures. Polyphenylene sulfide (PPS) was attached to the treated Al surface by an injection molding process to fabricate PPS-Al hybrids. The nanostructures formed on the aluminum surface by hot water treatment were found to be composed of AlOOH, thus the Al surface acquires better wettability properties. With increasing treatment temperature and treatment time, the nanostructures were continuously increasing and becoming larger in scale, but with a consequent decrease in stability. Therefore, when the treatment temperature was 70°C and the treatment time was 10 min, the medium-scale AlOOH formed the strongest mechanical anchoring effect with PPS. The joining strength of the PPS-Al hybrid was enhanced by 200% against the hybrid prepared by sandpaper sanding treatment, which reached 12.16 MPa. After tensile failure, the failure mode of the hot water-treated hybrids was a mixed failure mode of interfacial failure and polymer cohesion destruction. In short, these results provide insights for the preparation of environmentally friendly PMH products.

Producing Freestanding Single-Crystal BaTiO3 Films through Full-Solution Deposition.

Strontium aluminate, with suitable lattice parameters and environmentally friendly water solubility, has been strongly sought for use as a sacrificial layer in the preparation of freestanding perovskite oxide thin films in recent years. However, due to this material's inherent water solubility, the methods used for the preparation of epitaxial films have mainly been limited to high-vacuum techniques, which greatly limits these films' development. In this study, we prepared freestanding single-crystal perovskite oxide thin films on strontium aluminate using a simple, easy-to-develop, and low-cost chemical full-solution deposition technique. We demonstrate that a reasonable choice of solvent molecules can effectively reduce the damage to the strontium aluminate layer, allowing successful epitaxy of perovskite oxide thin films, such as 2-methoxyethanol and acetic acid. Molecular dynamics simulations further demonstrated that this is because of their stronger adsorption capacity on the strontium aluminate surface, which enables them to form an effective protective layer to inhibit the hydration reaction of strontium aluminate. Moreover, the freestanding film can still maintain stable ferroelectricity after release from the substrate, which provides an idea for the development of single-crystal perovskite oxide films and creates an opportunity for their development in the field of flexible electronic devices.

A new insight on efficient ammonia borane dehydrogenation withRu-Imine@Al2O3 catalyst

Ammonia borane is widely recognized as a reliable source of hydrogen. However, for efficiently generate hydrogen from ammonia borane, the use of appropriate catalysts is necessary. Transition metal catalysts, significantly enhance the hydrogen production. In our study, we focused on synthesizing a catalyst, Ru-Imine@Al2O3, by incorporating ruthenium-imine onto the surface of alumina in an ethanoic solution. We conducted this synthesis under ambient conditions. We employed advanced analytical techniques to characterize it. To better understand the structure and composition of catalyst. Notably, this is the first time that Ru-Imine and Ru-Imine@Al2O3 have been used for dehydrogenation of ammonia borane. During our experiments, we found that the Ru-Imine@Al2O3 catalyst exhibited excellent activity in the dehydrogenation process of ammonia borane, releasing hydrogen. We tested different levels of Ru-Imine usage and observed the best performance with 10 % Ru-Imine complex in a 10 mg catalyst. Under these conditions, the catalyst produced 19531 mL H2gcat.−1min−1, at 30.0 ± 1 °C. the catalytic activity of 100 % Ru-Imine was also tested under the specified conditions and produced 14183 mL H2gcat.−1min−1. To gain further insights into the reaction, we thoroughly determined the kinetics and proposed a mechanism for the dehydrogenation process. Our findings revealed that Ru-Imine@Al2O3 catalyzed dehydrogenation of ammonia borane exhibited a lower activation energy (Ea) of 21.9 kJ mol−1. This implies that the reaction can proceed more easily and efficiently with the presence of the catalyst. Furthermore, we assessed the reusability of the catalyst and found that it demonstrated excellent performance even after eight cycles with 100 % conversion of ammonia borane. This highlights the potential of the Ru-Imine@Al2O3 catalyst for repeated use without significant degradation in its activity. These findings contribute to the advancing of hydrogen generation technologies and offer promising prospects for utilizing ammonia borane as a hydrogen source.

Enhancing vacuum surface flashover voltage of alumina insulator by self-assembly of fluorine-containing molecule

In this study, a fluorocarbon chain was grafted on the surface of the alumina insulator through the molecule self-assembly of perfluorododecyl trichlorosilane to enhance the vacuum surface flashover voltage. A hydrocarbon chain with the same molecular structure, devoid of fluorine element, was also grafted through the self-assembly of dodecyl trichlorosilane to enable comparison. The surface state examination of the self-assembled alumina insulators shows that both the molecules are attached to the alumina surface. The arrangement of the molecules on the surface is regular. Surface property tests reveal that the fluorocarbon chain endows the surface of alumina with a lower secondary electron emission yield and a lower gas adsorption volume than the hydrocarbon chain. Correspondingly, the surface flashover voltage of the fluorocarbon chain grafted insulator is higher than that of the hydrocarbon chain. This implies that the surface flashover voltage can be improved through surface fluorination, which converts hydrocarbon bonds to fluorocarbon bonds. The study demonstrates this possibility at the molecule level.

Assessment of machine learning models trained by molecular dynamics simulations results for inferring ethanol adsorption on an aluminium surface

Molecular dynamics (MD) simulations can reduce our need for experimental tests and provide detailed insight into the chemical reactions and binding kinetics. There are two challenges while dealing with MD simulations: one is the time and length scale limitations, and the latter is efficiently processing the massive amount of data resulting from the MD simulations and generating the proper reaction rates. In this work, we evaluated the use of regression machine learning (ML) methods to solve these two challenges by developing a framework for ethanol adsorption on an Aluminium (Al) slab. This framework comprises three main stages: first, an all-atom molecular dynamics model; second, ML regression models; and third, validation and testing. In stage one, the adsorption of ethanol molecules on the Al surface for various temperatures, velocities and concentrations is simulated using the large-scale atomic/molecular massively parallel simulator (LAMMPS) and ReaxFF. The outcome of stage one is utilised for training, testing, and validating the predictive models in stages two and three. We developed and evaluated 28 different ML models for predicting the number of adsorbed molecules over time, including linear regression, support vector machine (SVM), decision trees, ensemble, Gaussian process regression (GPR), neural network (NN) and Bayesian hyper-parameter optimisation models. Based on the results, the Bayesian-based GPR showed the highest accuracy and the lowest training time. The developed model can predict the number of adsorbed molecules for new cases within seconds, while MD simulations take a few weeks. This adsorption rate can then be used in macroscale simulations to tackle the time and length scale limitations. The proposed numerical framework has the potential to be generalised and, therefore, contribute to future low-cost binding reaction estimations, providing a valuable tool for industry and experimentalists.

Interfacial activation of anode in aluminum-air battery through incorporating 5-carboxyl benzotriazole@β-cyclodextrin assembly in synthetic seawater electrolyte

Neutral electrolyte, such as synthetic seawater (SW), is a promising candidate for aluminum-air (Al-air) battery due to the alleviated hydrogen evolution along with anode self-corrosion. However, aluminum surface passivation in SW poses a serious challenge for battery's power generation. Following molecular self-assembly theory, 5-carboxylate benzotriazole (CB) was incorporated into β-cyclodextrin (β-CD), which (CB@β-CD) was utilized as an interfacial activator for aluminum anode in SW. CB could be released from β-CD, and activated aluminum surface, facilitating anode discharge. The specific capacity and energy density of Al-air battery were achieved as 2607.4 mAh/gAl and 2.37 kWh/kgAl, respectively, at an optimal CB@β-CD concentration of 120 mg/L. Density functional theory calculations revealed that the overwhelming adsorption energy of guest molecule (CB) on Al (111) plane over its binding energy inside host (β-CD) accounted for the release of CB on anode surface, and the ensuing interfacial activation effect.

Investigation of Rosemary Oil as Environmentally Friendly Corrosion Inhibitor of Aluminum Alloy

The inhibitory effect of Rosemary oil on the corrosion of aluminum alloy EN AW-2011 in 1M H2SO4 solution was studied by weight loss and electrochemical methods such as open circuit potential (OCP), linear sweep voltammetry (LSV) and linear polarization resistance (LPR). The inhibition efficiency increases with increasing the concentration and shows maximum inhibition efficiency (70.7 %) at optimum concentration (0.05 g.L-1). The linear polarization resistance measurements show that the presence of Rosemary oil in 1M H2SO4 solution influences polarization resistance increasing and corrosion current decreasing. The voltammetric curve shows that Rosemary oil reduces the anodic process. Open circuit potential results confirmed that organic compounds present in Rosemary oil can form a protective layer on aluminum surfaces. The inhibitive effect was probably caused by the adsorption of organic compounds such as 1,8-cineole, α-pinene, borneol, limonene, and myrcene on aluminum surfaces which are non-toxic and environmentally friendly. This study showed that the essential oil of Rosemary could be used as an environmentally friendly inhibitor of the corrosion of alloy EN AW-2011 in an acidic medium.

Microstructure and mechanical characteristics of Al1050/B2O3+Cu hybrid surface nanocomposite fabricated using friction stir processing

Abstract In the realm of advanced materials engineering, the development of hybrid nanocomposites has garnered significant attention due to their superior mechanical properties and potential applications. The primary aim of this research is to develop a surface hybrid nanocomposite using Al1050 aluminium alloy (5 mm thickness) as the base material through friction stir processing. B2O3 nano-powder, averaging 100 nm in size, and Cu micro-powder, averaging 5 μm in size, were incorporated into the aluminium surface in various volume ratios using the Friction Stir Processing (FSP). The processing parameters included a tool rotational speed of 1250 rpm, a feed rate of 50 mm min−1, and a tilt angle of 3°. The number of passes was set at two levels: 1 and 3 passes. The influence of the volume ratio of constituents and the number of passes on the microstructure and mechanical properties of the resulting composite was thoroughly explored. The samples underwent tensile tests, microhardness tests, and metallographic examinations using both Optical Microscopy (OM) and Field Emission Scanning Electron Microscopy (FE-SEM). The composite with 25%-B2O3-75%-Cu composition exhibited the highest stress and hardness values, measuring 139 MPa and 58.14 HV, respectively. The enhanced strength of this sample is attributed to the presence of additives and the resultant grain size.

Scale-independent model based on fractal theory for calculating the adhesion force between a particle and rough surfaces.

The elimination of the scale-dependent statistical parameters is a challenge in the estimation of the van der Waals force between a particle and rough surfaces. Herein, a scale-independent parameter, the fractal dimension, was introduced into the Rabinovich model to calculate the microadhesion force. First, a Weierstrass-Mandelbrot function is proposed to generate a random 2D contour, which has a simplified form and is more reasonable for spectrum analysis. And then, the roughness scale extraction method was employed to calculate the fractal-dimension value of the real aluminum (Al) surface. And last, the proposed scale-independent Rabinovich-Fractal model was used to calculate the adhesion forces, which are consistent with the results of the atomic force microscopy adhesion test. Aside from providing a more accurate estimation of the van der Waals forces, the proposed model is not influenced by the sampling scale of the surface roughness measurement, which eliminates the related error in van der Waals force estimation.

Anti-icing performance and influencing factors of super-lubricated surface in simulated glaze icing

Abstract The icing of the overhead aluminum conductor has caused the conductor load to be too heavy or uneven, which results in huge accidents. The super-lubricated surface (SLIPS) shows great potential in anti-icing. Glaze ice is a common type of icing, and its damage to transmission lines is the most serious. However, the properties and influencing factors of anti-icing lubricated surfaces at glaze ice surroundings are rarely reported. In this study, the super-lubricated surface was prepared by the anodic oxidation method, and the anti-icing properties and influencing factors of surfaces were investigated in glaze ice surroundings. The results demonstrate that the SLIPS can decrease the icing amount, which is only 41% of the original aluminum surface. SLIPS exhibits excellent anti-icing performance in different environments temperatures and rainfalls. This study provides experimental guidance for the practice application of SLIPS in anti-icing aluminum conductors.

Effect of spinach (Spinacia oleracea) leaf extract on the aluminum (Al) as a green corrosion inhibitor in HCl medium

Green corrosion inhibitors have recently attracted much attention due to their non-toxic properties, especially plant extracts. This study used spinach leaf extract (Spinacia oleracea) as a corrosion inhibitor on aluminum in an HCl medium. Spinach leaf extract (Spinacia oleracea) was obtained by maceration method, using ethanol as the solvent, which was then distilled to purify the extract. The corrosion inhibition properties were studied by the gravimetric method. The results showed that spinach leaf extract (Spinacia oleracea) can efficiently decrease the corrosion rate of aluminum in an HCl medium, achieving a maximum efficiency of 96.7742 %. Spinach leaf extract (Spinacia oleracea) formed a protective layer on the aluminum surface via adsorption and chemisorption, thus increasing surface coverage and blocking mass transfers. As the inhibitor concentration increases, the corrosion rate decreases, and the corrosion inhibition efficiency increases. This study shows that spinach leaf extract (Spinacia oleracea) is a viable organic corrosion inhibitor option with high efficiency.

Alumina coatings on Ni-based superalloys: The impact of annealing on heavy oil fouling

As the sweet crude oil reserves decline, refiners must treat sulfur-rich heavy oil, requiring harsher operating conditions, which are detrimental to process equipment. Application of coatings on critical components protects surfaces against sulfidation, corrosion, and fouling, extends the equipment's lifetime, and reduces the frequency of costly turnarounds. In the present work, we coated Inconel 625 and Inconel 718 substrates with amorphous alumina thin films at room temperature using reactive RF magnetron sputtering. Annealing of the deposited coatings at 800, 900, and 1000 °C increased hardness, improved adhesion, and generated crystalline polymorphs, predominantly γ-Al2O3 at lower temperatures, while α-Al2O3 was present at 1000 °C. The annealed substrates formed thermally grown oxides (TGOs), which interacted with the alumina coatings. The TGOs followed grain boundaries in the case of IN718 and a crater-like pattern on IN625. Annealed substrate precipitates generated columnar-like protrusions responsible for inducing crack propagation, which exhibited TGO formation. After 2 h exposure to heavy oil (containing 0.06 g g−1 sulfur) at 450 °C and 11.3 MPa the as-deposited amorphous alumina presented no clear sign of adherent fouling, while the 1000 °C annealed crystalline alumina surfaces presented evidence of fouling.

Combined Experimental and Periodic DFT Study of the Size Dependence of Adsorption Properties of Oxide‐Supported Metal Nanoclusters: A Case of NO on Ni/Al2O3

ABSTRACTIt is demonstrated by means of ultra high vacuum (UHV) surface‐sensitive techniques and periodic density functional theory (DFT) calculations that the electronic and NO− adsorption properties of nanosized Ni clusters deposited onto the α‐Al2O3 (0001) surface significantly depend upon the size of the cluster. The properties of the Ni cluster of the size of 2 nm and lower are predominantly determined by the formation of the Ni/Al2O3 interface bond notably polarized towards the oxide. As a result, the metal cluster acquires a net positive charge manifested by the bond strengthening of adsorbed NO compared to the bulk Ni substrate. With the increasing size of the cluster, the Ni/Al2O3 interfacial bond depolarizes due to the growing of lateral Ni–Ni interaction. With a mean coverage of Ni on the alumina surface exceeding 0.25 equivalent monolayers, their properties in terms of adsorption behavior of NO resemble those that are characteristic for the bulk Ni substrate. Such a size dependence offers an opportunity to tune the properties of metal clusters and the metal/oxide system as a whole, for example, to achieve the required electronic and adsorption‐reaction properties.

Theoretical and experimental studies of cephalexin adsorption on aluminium as a new alternative of removal from wastewater

ABSTRACT Cephalexin (CPX) is an antibiotic widely used to treat many infections. CPX has become an emerging pollutant present in wastewater. On the other hand, it is well known that organic compounds can be adsorbed over metal surfaces when the metal is in active state such as when it is rusting. This work proposes an alternative for the elimination of CPX from wastewater, applying electrochemical principles using a conventional and cheap substrate, aluminium. The first part consisted of obtaining the active states of aluminium electrodes carrying out voltametric curves at different pH (4, 7 and 9) to find the particular condition of interaction between CPX and metal surface. The potential was used in the potentiostatic tests to set the activation potential of metal at different times. After the treatment, electrolyte solutions were analysed using UV-vis spectra, and the aluminium surfaces were studied by optical micrographs and X-ray diffraction. In addition, aluminium-CPX interactions were corroborated by quantum-chemical calculations and adsorption isotherms. All results indicate that it was possible for the CPX removal at basic pH conditions, where the molecule adsorption on the aluminium substrate occurs due to a strong electrostatic interaction.