Aluminum Surface Research Articles

Study on the tribological properties and corrosion resistance of the modified NiZnAl-LDH coating on anodic aluminum surface

The porous structure of anodized aluminum creates an opportunity for corrosive media to contact the aluminum substrate, resulting in diminished corrosion resistance and wear performance under adverse conditions. In this study, ternary hydrotalcite containing Ni, Zn, and Al elements, named NiZnAl-LDH, was synthesized on anodized aluminum surfaces using an in-situ growth method. The corrosion and wear resistance of the aluminum substrate were further enhanced by intercalation modification with sodium molybdate. The impact of synthesis parameters, including pH, reaction temperature, and reaction time, on the corrosion and wear resistance of the coating was investigated. Morphology, structure, and properties of the coating were analyzed. The results confirm the synthesis of NiZnAl-LDH modified with sodium molybdate intercalation. Electrochemical tests revealed that immersing NiZnAl-LDH in a sodium molybdate solution with a pH of 9.5 for 2.5 h at 35 °C resulted in a minimum self-corrosion current density of 4.131 × 10−8 A cm−2, significantly enhancing the corrosion resistance of the coating. Friction tests demonstrated a coating friction coefficient of 0.28, indicating excellent tribological performance. The discussed process parameters in this study provide valuable insights for the synthesis and application of LDH, expanding the application of aluminum alloys in the field of corrosion resistance and wear resistance.

Depth-resolved mechanical behaviour of shot peened 7050-T7451 aluminium surfaces using in-situ synchrotron X-ray diffraction

We have assessed the elasto-plastic (sub)surface behaviour of 7050-T7451 aluminium alloy treated by shot peening using S110 steel shots of 300 μm in diameter and two different intensities, namely Almen intensity (A) of 3.4 (low-intensity) and 10.9 (high-intensity). Shot peening (SP) is a cold work process applied in the aerospace industry to enhance the fatigue tolerance of structural components after machining. The local mechanical response within the SP-induced layer was depth profiled at room temperature by performing an X-ray micro-diffraction experiment in transmission geometry at a synchrotron source, during tensile loading of the specimen to rupture. The presence of a SP-induced layer in the specimen is evidenced by compressive longitudinal lattice strains (∼-540 με for low-intensity and ∼-4200 με for high-intensity at 0.1 mm from the surface for the 311 reflection), parallel with respect to the applied load, i.e. perpendicular to the direction of impact of the steel shots, and also by higher values of the Full-Width-at-Half-Maximum (FWHM) of the diffraction peaks than those measured in the bulk material, due to the local plastic deformation induced by shot peening. High-intensity shot peening produced a higher surface roughness (Sa ∼13 μm), and also two times thicker deformed surface layer (∼0.4 mm), than low-intensity shot peening (Sa ∼2 μm and ∼0.2 mm thick deformed layer). For both shot peening conditions, the local yield stress of the surface layer and bulk material were similar, however the severely affected layers exhibit a non-linear elastic behaviour when applying loads lower than the yield stress of the material. Beyond yielding, the presence of SP-induced layers is mainly evidenced by the relatively higher value of the FWHM near-surface compared to the bulk (∼20 % higher for low-intensity and ∼40 % for high-intensity), due to the initial plastic deformation accumulated during shot peening and additional plasticity during loading of the specimen.

Fluorine-free, corrosion-resistant aluminum surfaces with nickel hydroxide and stearic acid superhydrophobic coatings

Fluorine-free, corrosion-resistant aluminum surfaces with nickel hydroxide and stearic acid superhydrophobic coatings

Characterization, inhibition efficiency and DFT simulation of 1,2-bis(2-bromobenzylidene)hydrazine towards aluminum 1050 in H2SO4 1M

In this study, 1,2-bis(2-bromobenzylidene)hydrazine (BBBH) has been synthesized and for the first time its corrosion inhibition efficiency was studied for pure aluminum corrosion in 1M sulfuric acid using polarization curve technique. After treatment of experimental data at 298 K, the results revealed that the compound is a good inhibitor and the efficiency increase with its concentration, to attain 83.23 % for 600 ppm. The adsorption process of this Schiff base on aluminum surface obeys Langmuir isotherm. To complete the inhibition study, thermodynamic parameters including activation energy, Gibbs free energy, were discussed. In order to characterize the Aluminum surface, scanning electron microscopy (SEM), DRX and X-ray photoelectron XPS were used to demonstrate the effect of the inhibitor and the formation of a protective layer. The molecular electronic structure of the title compound was established using the density functional theory (DFT) approach to understand molecular geometry, stability, and chemical reactivity. The FTIR, UV, 1H-NMR and Raman spectroscopy were further applied to examine its purity.

Diisopropyl Methylphosphonate and Sarin Decomposition on Pristine vs Hydroxylated Alumina Surfaces: Mechanistic Predictions from Ab Initio Molecular Dynamics

Diisopropyl Methylphosphonate and Sarin Decomposition on Pristine vs Hydroxylated Alumina Surfaces: Mechanistic Predictions from Ab Initio Molecular Dynamics

Acid wet blasting method for fabricating superhydrophobic aluminum surface with micro-nano composite structures

Acid wet blasting method for fabricating superhydrophobic aluminum surface with micro-nano composite structures

Regulating the coordination environment of surface alumina on NiMo/Al2O3 to enhance ultra-deep hydrodesulfurization of diesel

Herein, a set of NiMo/Al2O3 catalysts with distinct coordination state of surface alumina were design and prepared by a facile calcination strategy. Various characterization methods were employed to analyze the structural properties of NiMo/Al2O3 catalysts, and the catalytic performances of corresponding catalysts were tested for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The results indicate that the synthesized samples show uniform specific surface area (130 m2·g−1) and pore size (3.5 nm), but varying penta-coordinated aluminum content, which significantly influences the NiMo/Al2O3 catalysts’ surface acidity. Therein, NiMo/Al2O3-600 prepared by calcination at 600 °C exhibits the highest ratio of penta-coordinated aluminum species, which endows more abundant Brønsted acid than that of tetra- and hexa-coordinated aluminum counterparts, thereby substantially promoting the isomerization and direct desulfurization pathways of 4,6-DMDBT HDS, and thereafter considerably boosting the HDS performance of NiMo/Al2O3-600 with 94.5 % 4,6-DMDBT conversion, which is notably higher than that of NiMo/Al2O3-500 (74.4 %) and NiMo/Al2O3-700 (62.7 %).

СТРУКТУРА И ПЕРСПЕКТИВЫ ПРИМЕНЕНИЯ В КАЧЕСТВЕ АДСОРБЕНТА ПОРИСТОГО ОКСИДИРОВАННОГО АЛЮМИНИЯ

The paper presents the results of microarc oxidation of porous aluminum made of alloys AlSi15, Д16 (D16) and AlMg6. According to research, on the surface of the sample, a composite oxide-ceramic coating is formed, consisting of mullite 3Al2O3‧2SiO2 and (or) various forms of aluminum oxide (α-, γ-Al2O3). It is shown that on the surface of porous aluminum, as well as in the pores of a cast sample, a coating is formed consisting of electropositive and electronegative sorption materials, aluminum oxides and aluminosilicates. Moreover, by changing the composition of the aluminum alloy and micro-arc oxidation modes, it is possible to control the phase composition of the coating being formed, which opens up the possibility of creating selective filter devices to retain either anionic or cationic inorganic compounds and microbiological objects.

Effect of Phosphate Concentration on Anodizing Process Efficiency and Aluminium Surface Hardness in 16% Sulfuric Acid Solution

Effect of Phosphate Concentration on Anodizing Process Efficiency and Aluminium Surface Hardness in 16% Sulfuric Acid Solution

Aqueous phosphonic acid treatments of aluminium: Effect of oxide dissolution and re-oxidation on adsorbate formation

Functionalization of Aluminium surfaces by phosphonic acid (PA) treatments is of key industrial importance. This work discloses the effect of PA molecular design on the performance of aqueous PA surface treatments of Aluminium under acidic conditions. Comprehensive XPS and ToF-SIMS analyses show that the “final” nature of the PA adsorbate layer is not only governed by competing in-situ PA adsorption and oxide dissolution processes, but also by modifications of the transient state of the adsorbate layer during subsequent water rinsing in air. Low-soluble organo-metallic-phosphonic (OMP) deposits formed by complexation with Al3+ ions in solution are largely removed upon water-rinsing; only few physisorbed OMP complexes are converted trans-situ to a chemisorbed state. The in-situ oxide dissolution and ex-situ re-oxidation processes are suppressed with increasing steric size of the PA molecule. Moreover, intermolecular phenyl π-π interactions can act as a driving force to increase the surface density of the PA adsorbate layer in-situ, which also effectively suppresses in-situ oxide dissolution and ex-situ re-oxidation. The findings provide profound insights on how PA molecular designs can be tuned to tailor the chemistry and morphology of PA-adsorbate layers, which may contribute to advance surface treatment strategies of Al surfaces for a wealth of applications.

Functionalization of aerosil, titanium dioxide and diatomaceous earth powders by wetting with a low surface energy agent, and study of their properties

The conditions for functionalization of micro- and nanopowders of aerosil, titanium dioxide and diatomaceous earth by wetting them with a liquid hydrophobic agent (tetraethoxysilane) and giving them fobno/philic properties are investigated. Using infrared spectroscopy, derivatography, scanning electron microscopy, and ξ-metry, the mechanism of tetraethoxysilane interaction with the surface of these powders and their morphology were studied. All powders thus modified are characterized by a non-homogeneous distribution of particles with different aggregation levels: predominantly micrometer-sized particle population (diatomaceous earth), micrometer-sized formation combined with nanoclusters (aerosil, titanium dioxide). Diluted suspensions of functionalized powders in fluorinated varnish were used for hydrophobization of glass, aluminum, and steel surfaces. The highest value of the water wetting edge angle (156°) was observed for aluminum coatings obtained using a composition containing functionalized aerosil.

A simple and efficient resin precoating treatment on anodised substrate surfaces for enhancing the adhesive bonding strength between aluminium and mild steel

The primary concerns in the adhesive bonding of metal substrate surfaces include inadequate wettability, compatibility, and insufficient mechanical interaction at the bonding interface. These factors are significant barriers to developing and manufacturing high-strength bonded materials. This study utilized three different anodising techniques, such as H3PO4, H2SO4, and NaOH, to produce micro-rough surfaces that improve the adhesive bond between aluminium alloy and mild steel. A novel and a simple method known as resin pre-coating (RPC) were used to increase the wetting and effectively seal the micro-cavities of mild steel and aluminium surfaces. RPC solution comprises 10 wt% resin (Absence of hardener) and 90 wt% acetone, which facilitated the penetration of resin into the microcavities surface, thereby increasing the bonding surfaces. Subsequently, the normal adhesive mixed with hardener is placed onto the metal surfaces. The adhesive bonding strength was evaluated by conducting the single lap shear test under various surface conditions. The surface topography of anodised samples were examined by X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), and Contact Angle Goniometer. Experimental results of a lap shear test revealed that the adhesive bond strength of H3PO4 anodised samples is greater than those of H2SO4 and NaOH anodised samples. Furthermore, the RPC treatment increased the bond strength of all H3PO4 anodised samples by 46.91–47.26 %, for H2SO4 samples by 39.71–42.22 %, and NaOH samples by 37.89–48.51 %, compared to the readings obtained without RPC treatment. The combined use of H3PO4 and RPC treatment results in the greatest bonding strength of 16.765 MPa, which is 9.17 % and 20.10 % greater than the bonding strength of H2SO4 and NaOH anodised samples. Thus, the H3PO4 anodised method improved the wetting ability of the metal surface and maximized the use of contact area on the rough substrate surfaces. The anodising treatment details in this study are inexpensive and simple for creating strong adhesive joints in aviation, automobile, and aerospace applications.

Gravimetric characteristics and friction parameters of common bean (Phaseolus vulgaris L.)

When designing appropriate machinery systems, equipment, and infrastructures for interacting with, cultivating, gathering, and agriculture-related processing, it is required to have an understanding of the engineering characteristics of agricultural products. This unpredictability makes it difficult to design or develop machines that can efficiently and effectively manage a wide range of product characteristics. Experimental analysis was used to accomplish the study's objective, which was to investigate the implications of variation on the gravimetric characteristics and frictional parameters of common bean (Phaseolus vulgaris L.) concerning the design of the threshing machine. The mean average values of gravimetric parameters were determined by analysing the experimental data: arithmetic mean diameter (7.042 ± 0.473 mm), geometric diameter (6.737 ± 0.463 mm), bulk density (781.20 ± 25.34 kg m-3), true density (1347.03 ± 143.0 kg m-3), porosity (41.385 ± 7.05%), width (6.316 ± 0.502 mm), thickness (4.962 ± 0.50 mm), projected area (49.194 ± 6.715 mm2), and volume of the seed (161.689 ± 3.778 mm3). The average moisture content values were found to be 11.214±1.185% on a dry basis, the static coefficient of friction varied between 0.276 and 0.386 on the surface of iron sheets, 0.294 to 0.435 on stainless steel, 0.317 to 0.434 on galvanized iron, 0.321 to 0.451 on medium density fiberboard, 0.319 to 0.480 on aluminum, 0.310 to 0.470 on painted sheets, 0.320 to 0.440 on glass, 0.333 to 0.447 on plastic, and 0.374 to 0.575 on rubber. Perforated sheet surfaces showed the highest static coefficients of friction, followed by rubber, plastic, plywood, glass, aluminum, galvanized iron, painted sheet, stainless steel, and iron sheet surfaces. These data are not only required for predicting loads in agricultural storage structures but are also needed to establish useful sources for the development of machinery for handling, cleaning, storing, transporting and drying, among other things.

Effect of Redox Mediators on Corrosion Behavior and Scanning Electrochemical Microscopy Response.

Scanning electrochemical microscopy (SECM) is widely used to measure local electrochemical reactivity of corroding surfaces. A major criticism of using SECM in feedback mode for corrosion studies is the requirement of an external redox mediator (RM) as it could react with the metal and affect the Nernst potential at the metal-solution interface. Consequently, it becomes challenging to differentiate the interference caused by the RM from the local reactivity of the metal. Herein, a multiscale electrochemical approach is presented to investigate the effect of RM choice on the corroding substrate. Two common RMs, ferrocenemethanol and hexaammineruthenium(III) chloride, were used to perform SECM over copper and aluminum. It was found during macroscale electrochemical measurements that Ru(NH)63+ acted as an oxidant and promoted corrosion. The SECM feedback behavior varied for copper depending on the RM used, suggesting that the corrosion reactions controlled the negative feedback mechanism, not the formation of an insulating passive film. The passivated aluminum surface consistently exhibited negative feedback, regardless of the RM used. SECM approach curves also displayed a distortion in the steady state current, which was caused by the deposition of substrate-generated species on the microelectrode. These deviations in feedback response were accounted for during analysis through incorporation into a finite element model to accurately extract the RM kinetic rate constants. The importance of understanding these processes is highlighted to avoid misinterpretation of passive behavior and advances toward a more quantitative use of SECM for corrosion studies.

Hardness and Microstructure of TiN Coating on Aluminum Alloy with DC Sputtering

Titanium Nitride coating has attracted much interest in increasing the hardness of aluminum alloys. This study aims to investigate the effect of Ar: N gas mixture and time on increasing the hardness of aluminum alloys using DC sputtering. Preparation of TiN thin films on aluminum alloy substrates using flowing gas mixture parameters and time. First, the layer of TiN was deposited on the sample with a gas mixture of 90Ar:10N; 80Ar:20N; 70Ar:30N; and 60Ar:40N (%) for 60 minutes. Then the optimum gas mixture that produces the highest surface hardness is used in the second process with time variations of 30, 60, 90, and 120 minutes. The results showed that the highest hardness was achieved in a gas mixture of 70Ar:30N and 60 minutes. The TiN phase formed on the aluminum surface was identified by XRD, while the surface morphology was observed by SEM. Compared with untreated samples, the hardness of treated samples increased significantly.

Effect of Condensed Water at an Alumina/Epoxy Resin Interface on Curing Reaction.

The adhesion of epoxy adhesives to aluminum materials is an important issue in assembling parts for lightweight mobility. Aluminum surfaces typically possess an oxide layer, which readily adsorbs water. In this study, the aggregation states of water and its effect on the curing reaction were examined by placing a water layer between an amorphous alumina surface and a mixture of epoxy and amine components. This study used molecular dynamics simulations and density functional theory calculations. Before the reaction, water molecules strongly adsorbed onto the alumina surface, aggregating excess water. Some water diffused into the epoxy/amine mixture, accelerating the diffusion of unreacted substances. This led to faster reaction kinetics, particularly in proximity to the alumina surface. The adsorption of water molecules onto the alumina surface and the aggregation of excess water were similarly observed even after the curing process. Subsequently, the interaction between the alumina surface and various functional groups of the epoxy/amine mixture was evaluated before and after the reaction. Epoxy monomers had little interaction with the alumina surface before the reaction, whereas hydroxy groups formed by the ring-opening reaction of epoxy groups exhibited notable interaction. Conversely, sulfonyl and amino groups in amine compounds formed hydrogen bonds with OH groups on the alumina surface before the reaction. However, after the reaction, amino groups weakened their interaction with the alumina OH groups as they transformed from primary to tertiary during the curing reaction. Both epoxy and amine monomers/fragments similarly interacted with water molecules, both before and after the reaction. The insights gained from this study are expected to contribute to a better understanding of the impact of moisture absorption on the application of epoxy resins.

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.