Al Substrate Research Articles

Microstructural evolution and mechanical properties of Al2O3/Al joint bonded by Bi2O3-B2O3-SiO2-ZnO-Al2O3 glass

A glass filler of 60Bi2O3-20B2O3-10SiO2-5ZnO-5Al2O3(mol%) was utilized to join 99Al2O3 ceramic and Al alloy 1060 at low temperature, which effectively addressed the negative impact caused by the indelible oxide film on the aluminum surface during the conventional process. Prior to the joining process, the surface morphology and thermophysical properties of the glass filler were investigated. Additionally, the wetting behavior of the glass on both the Al2O3 substrate and Al substrate was confirmed. Subsequently, the interfacial microstructure of the Al2O3/Al joints was analyzed in detail and the mechanical properties of the joints were evaluated under different temperatures and holding times. The shear strength of the joints reached a maximum value of 30.25 ± 1.0 MPa at 460 °C for 30 min. The precipitation and growth of the Bi24B2O39 phase improved the mechanical properties of the joints with increasing temperature and holding time. However, high temperatures and long holding times resulted in the precipitation of a large number of crystals in the joints, leading to embrittlement, which severely reduced the mechanical properties of the joints.

Erosion Wear Behavior of HVAF-Sprayed WC/Cr3C2-Based Cermet and Martensitic Stainless Steel Coatings on AlSi7Mg0.3 Alloy: A Comparative Study

The paper presents a comparative study of the erosion wear resistance of WC-10Co4Cr, Cr3C2-25NiCr and martensitic stainless steel (SS) coatings deposited onto an AlSi7Mg0.3 (Al) alloy substrate by high-velocity air‒fuel (HVAF) spraying. The influence of the abrasive type (quartz sand or granite gravel), erodent attack angle, thickness, and microhardness of the coatings on their and Al substrate’s wear resistance was comprehensively investigated under dry erosion conditions typical for fan blades. The HVAF-spraying process did not affect the Al substrate’s structure, except for when the near-surface layer was 20‒40 μm thick. This was attributed to the formation of a modified Al-Si eutectic with enhanced microhardness and strength in the near-substrate area. Mechanical characterization revealed significantly higher microhardness values for the cermet WC-10Co4Cr (~12 GPa) and Cr3C2-25NiCr (~9 GPa) coatings, while for the SS coating, the value was ~5.7 GPa. Erosion wear tests established that while Cr3C2-25NiCr and SS coatings were more sensitive to abrasive type, the WC-10Co4Cr coating exhibited significantly higher wear resistance, outperforming the alternatives by 2‒17 times under high abrasive intensity. These findings highlight the potential of HVAF-sprayed WC-10Co4Cr coatings for extending the service life of AlSi7Mg0.3-based fan blades exposed to erosion wear at normal temperatures.

Exploring wear, corrosion, and microstructure in PEO coatings via laser surface treatments on aluminum substrates

The inadequate resistance to corrosion and wear of Al-based alloys is a major hindrance to their extensive use. Plasma electrolytic oxidation (PEO), a common and efficient coating technique, creates an oxide coating similar to ceramic on the surface of Al-based alloys, thereby improving their ability to withstand corrosion and wear. Studies have shown that PEO treatment can significantly enhance the short-term corrosion and wear resistance of Al-based alloys. To improve the long-term corrosion resistance of PEO coatings, researchers are now exploring the combination of laser processes with the PEO process. Laser processing is a simple yet efficient technique known for its flexibility, precision, and control. Various laser procedures are recognized for their ability to improve the resistance to wear and corrosion of PEO coatings applied on Al substrates and their alloys. Laser melting procedures have the capability to standardize and modify the microstructure of aluminum-based alloys. This review focuses on enhancing the anti-corrosion and anti-wear properties of aluminum alloys through the integration of laser surface treatments with PEO technology.

Physical and microstructural properties of YSZ + Cr2O3 thermal barrier coatings developed using HVOF technique

A composite coating material of Yttria-Stabilized Zirconia (YSZ) and Chromium Oxide (Cr2O3) was developed on the surface of Al-6061 substrates. The coating consisting of equal measures of the composite material of YSZ and Cr2O3 was successfully obtained using the High-Velocity Oxy Fuel (HVOF) technique. The surface roughness and coating thickness of the composite coatings are evaluated. The surface roughness (Ra) was evaluated showing an average of 6.0848 µm using the Surface Roughness Tester (SRT). The coating thickness was evaluated showing an average of 220.8 µm using the Coating Thickness Tester (CTT). The surface roughness and the coating thickness obtained are comparable to typical physical properties of Thermal Barrier Coatings (TBC’s). The microstructural evaluation of the coated specimens was performed through the Scanning Electron Microscope (SEM), showing the clear unification of materials The determination of the elemental composition of surface coatings was performed through the EDAX tests, which clearly established the elements in the coatings. This article is indicative of the achievement of TBC’s consisting of composite materials though HVOF technique as an alternative to TBC’s obtained through surface coats and bond coats.

Liquid-phase shear exfoliation of graphite and its application as corrosion protection coating on aluminum substrate

Although aluminum (Al) or its alloys are moderately protected by a native oxide layer, the presence of chloride ions in aqueous media in direct contact causes pitting attacks and accelerates corrosion. Using graphene as a coating protector can obstruct corrosion due to its numerous chemical and physical properties. This study investigates corrosion protection of Al using graphene nanosheets (GNSs) produced by liquid phase shear exfoliation method (LPE). To do so, few layer-thick graphene nanosheet colloidal solutions were produced by a scalable eco-friendlier lower cost approach. The GNSs were thoroughly characterized using complementary characterization techniques to determine its quality. Spectroscopic and microscopic analyses indicate the synthesis of few-layers graphene (≤ 5 layers) with a high quality. Once approved, the colloidal solution of GNSs was spread over Al substrate by spray coating method, widely used in industrial manufacturing. Raman and near infrared spectroscopies, X-ray diffraction, microscopy techniques including scanning electron, transmission electron and atomic force microscopies were used to investigate morphological and structural behavior of coated GNSs films either on glass or Al substrates. Density functional theory (DFT) calculations revealed the interaction between the two materials is of the physisorption type, with almost no charge transfer and almost no effect of the number of graphene layers. Electrochemical measurements enabled to investigate the corrosion resistance of GNSs films and its stability over time in a 0.5 M sodium chloride (NaCl) solution, similar to marine surroundings. It was found that introducing a GNSs film can indeed reduce the corrosion rate and preserve Al substrate for an extended period.

INVESTIGATION OF WETTABILITY, ANTIBACTERIAL ACTIVITY, THERMAL INSULATION, AND MECHANICAL CHARACTERISTICS OF ELASTOMER BLEND ADHESIVES WITH HIGH-DENSITY FIBERBOARD WOOD AND ALUMINUM

Attention has recently been given to finding alternative and sustainable raw material sources for wood and metal adhesives, such as polyvinyl alcohol (PVA), corn starch (CS), arabic gum (AG), and dextrins (D). Modifying polymer dispersion using unique substances, such as modifying reactive elastomer liquid (EL) using PVA, CS, AG, or D results in sufficiently moisture-resistant adhesive joins. In the present study, the physical characteristics of EL/blended with the natural polymers PVA, CS, AG, and D, based on high-density fiberboard (HDF) wood and aluminum (Al) adhesives and coatings, were investigated and compared to those of pure EL. The EL was blended with PVA, CS, AG, or D at a ratio of 60/40 (w/w) to form EL/blends. The chemical structures, surface and interface morphology, adhesion strengths (including shear strength and pull-off strength), surface roughness, wettings, color intensity, and thermal insulation of the prepared EL and EL/blends were investigated. A scanning electron microscopy (SEM) investigation confirmed filler dispersion and adhesion between the blends, and coated HDF wood, or Al. The developed EL/AG blend had a pull-off strength of 144±5 and 102±3 MPa and a shear strength of 771±11, and 52±3 N with HDF wood and Al substrate, respectively. The EL/PVA blend had a maximum surface roughness value 4.57 µm, and its average water contact angle (WCA) was 85.6°. A plasma jet was used to treat the surface roughness and hence the wettability of the pure EL and the EL/blends, for example, plasma treatment decreased the roughness of the EL/AG blend from 4.36 to 3.28 μm. WCA, and hence wettability, was also significantly influenced by plasma treatment, for example, plasma treatment decreased the WCA of the pure EL from 71.7±0.4° to 30.7±0.7°. The lightness value of the EL/blends was less than that of the pure EL, indicating that (the color adhesives have darkened). Similarly, the yellowness-blueness and redness-greenness values of the EL/blends were greater than those of the pure EL,( rendering the blended adhesives more reddish and bluish). The EL/AG blend was found to have a minimum thermal conductivity (of 0.27 W/m.K), indicating maximum insulation.

A facile route derived solar selective nickel-cobalt oxide thin films via spraying process

Abstract This work focuses on understanding the role of annealing temperature on the solar selective performance of nickel-cobalt oxide thin films successfully sprayed onto Al substrates using the spray pyrolysis technique. The synthesized nickel-cobalt oxide thin films (~ 725± 20 nm thick) were post annealed at (400, 500 and 600) °C. The XRD and FESEM outcomes appeared high crystalline quality with crystal grains in the range of (27 – 52) nm and improved surface morphology for the sprayed thin films. The optical properties reflect solar absorptance ~ (85.2 %) and the thermal emittance ~ (4.45 %). The hardness and the Young’s modulus were (19.1 GPa) and (104 GPa) respectively. The aforementioned results are for the film annealed at 600 °C. The prepared and post annealed nickel-cobalt oxide thin films show band gap energies in the range of (1.15 – 1.38) eV. The nickel-cobalt oxide thin films also possess excellent thermal stability at higher temperature which makes them interesting candidate for solar absorbing and thermal collector applications.

Localized Surface Modification during Alternating Current Scanning Electrochemical Microscopy: Origin and Mechanism

In the current study, we report for the first time the observation of unintended localized surface modification on commercially pure aluminum (Al) during an alternating current scanning electrochemical microscopy (AC-SECM) analysis, its origin, and the probable mechanism responsible for it. Application of an AC perturbation potential (∼100 mV amplitude at ∼100 kHz frequency) to the Platinum ultramicroelectrode (Pt UME), during AC-SECM in acidic, neutral chloride, tap water, and alkaline electrolytes was found to cause surface modification on the scanned region of Al. An increase in the local pH of the electrolyte between the UME and the Al substrate, irrespective of the electrolyte pH (3–11) and UME biasing conditions, led to the local surface modification. The reason for the enhancement of local pH is attributed to the occurrence of higher rates of cathodic reduction reactions than that of anodic oxidation reactions. The reduction of dissolved oxygen/protons/water in the electrolytes led to the generation or consumption of OH−/H+ ions, respectively, and thus increased the pH, whereas the oxidation of Pt UME/Al surfaces decreased the pH with the generation of H+ or consumption of OH− ions. These results contribute significantly to accurately analyzing Al and its alloys using the AC-SECM technique.

Rapid Fabrication of Antilunar Dust Aluminum Surface by Nanosecond Laser Etching.

Although a dust-repellent surface is desirable for lunar exploration missions, its fabrication process is complicated and time-consuming. Herein, we report a simple and fast method to fabricate a lunar dust-repellent surface by texturing on an Al substrate via nanosecond laser etching. The laser-induced photothermal effect can rapidly create hierarchical papillary structures on 25 × 25 mm Al substrates (within 30 s). Both atomic force microscopy (AFM) and in situ scanning electron microscopy (SEM) reveal that such structures enable a reduced contact area between the Al substrate and lunar dust and thus reduced adhesion. The reduced dust adhesion force of Al substrates facilitates improving their antidust performance. By optimizing processing parameters, the Al substrate etched with a laser scanning spacing of 80 μm exhibits a lower dust adhesion force (9.58 nN) due to the smallest contact area with dust. Accordingly, its static antilunar dust performance (dust coverage of 1.95%) is significantly improved compared to the pristine Al substrate (dust coverage of 12.98%). Besides, the accumulated dust on the laser-etched Al substrates with low surface adhesion force is easily cleaned up by flipping and gravity (the dust residual rates are less than 17%). The Al substrate with excellent antidust ability presents good potential for lunar exploration missions.

Increasing joint strength by achieving carbon fibers’ continuity with ultrasonic assistance during soldering Cf/Al using ZnAl

Ultrasonic assistance was utilized during the soldering of carbon fiber-reinforced aluminum composites (Cf/Al) using ZnAl solder to enhance joint strength. The results indicated that carbon fibers migrated into the joint seam after Al substrate was eroded and the solder was expelled, effectively maintaining the continuity of the carbon fibers. A joint fully reinforced by carbon fibers was achieved with an ultrasonic application time of 60 s. Transmission electron microscopy revealed rapid wetting of the carbon fibers facilitated by ultrasound, characterized by an amorphous/nanocrystalline interface. The maximum joint strength reached 23.5 MPa, which is equivalent to 77.5 % of the Cf/Al.

Wear and neutron shielding resilience of titanium-hexagonal boron nitride coatings against extreme lunar radiation and thermal cycles

Ti6Al4V and Al6061 are aerospace alloys used in lunar structural components and rovers owing to their high specific strength. However, they deteriorate rapidly when subjected to demanding conditions of the lunar environment, such as extreme thermal cycles, solar particle radiation, and abrasive regolith. Cryo-milled powders were employed to deposit hBN-reinforced protective titanium coatings through plasma spray (atmospheric-APS and vacuum-VPS) with 2 and 10 vol% of hBN on Ti6Al4V and Al6061 substrates. These coatings were evaluated for durability under extreme lunar-like conditions, including thermal cycling, electron radiation, and synergistic (electron radiation-thermal cycle) exposure. The coatings exhibited radiation-induced hardening, resulting in a substantial increase in their microhardness ~20–40 % compared to virgin condition. Bright-field transmission electron microscopy (TEM) analysis reveals the presence of high dislocation densities, black dot defects, and dislocation clusters, providing evidence of the severe impact of synergistic environmental stresses. Ball-on-disk tribological tests were conducted in the presence of JSC-1 A lunar regolith simulant to evaluate the wear performance of coatings. Compared to conventional Ti6Al4V substrate, 50 %, 90 %, and 70 % reductions in wear volume were observed in the Ti/2 vol% hBN coatings in thermal-only, radiation-only, and synergistic environments. Neutron shielding tests indicate that the synergistic coatings offer higher neutron shielding performance by up to 28 % compared to virgin coatings, attributed to improved neutron capture by 10B isotopes. Upon a comprehensive assessment and ranking of multiple coatings under varying conditions, the VPS Ti/2 vol% hBN coating emerges as the top choice for protection against extreme radiation and thermal cycles for future lunar explorations.

Characterization of silicon-based chromium (VI) replacement coatings by using time-of-flight secondary ion mass spectrometry and salt spray tests

This paper proposes an innovative approach in characterization of silicon-based chromium (VI) replacement coatings on an Al substrate by using, salt spray tests and time-of-flight secondary ion mass spectrometry (ToF-SIMS) performed in profile mode by a gas cluster ion beam source (GCIB). While salt spray tests highlight the difference in anticorrosion behaviour, ToF-SIMS provides molecular information on the entire coating and even down to the interface with the Al substrate. ToF-SIMS revealed Si2O2+ and SiOAl + fragments which both contribute to understanding the differences in the anticorrosion performance which are found in the salt spray tests. Si2O2+ moieties relate to the cross-linking density of the coating and subsequently determines the barrier properties. SiOAl+ originates from the interface and characterizes the actual “conversion” of Al at the interface by the deposited layer. The differences in the profile of Si2O2+ and SiOAl + explained the respective anticorrosion performance. From the tested coatings PCT161 showed the highest intensity for both Si2O2+ and SiOAl + while simultaneously performing the best results in the salt spray test. These observations highlight that Si2O2+ and SiOAl + fragments are good indicators of anticorrosion performance and are confirmed by salt spray tests. Moreover, PCT161 and PCT146 are true conversion coatings capable of replacing chromium-based systems.

TinyML-Raman: A novel IoT based field-deployable spectra analysis for accurate identification of pharmaceuticals and trace dye-pesticide mixtures from facile SERS method

BackgroundUpcoming inexpensive, compact Internet of Things (IoT) microcontrollers i.e., tiny-machine learning (TinyML) takes the ML driven Raman spectroscopy one step ahead for realization of more affordable and highly compact field deployable instruments. Further, lack of large spectral datasets and need for numerous specialized SERS substrates impede the development of various ML-based surface enhanced Raman spectroscopy (SERS) applications. The aim is to introduce TinyML analysis on wide range of spectra classes using customized dataset obtained with low-cost SERS. In this regard, it is vital to establish an optimum ML model and efficient data handling methodology for low memory TinyML units. ResultsWe introduce a novel TinyML methodology for accurate classification of large spectra classes with smartphone assistance for data communication and results visualization. To generate large customized spectral dataset, we present a facile, micro-drop SERS using Au colloids and reusable grooved Al substrates. The results demonstrated that memory efficient 8-bit data quantization based convolutional neural network is effective for accurate identification of 22 different spectra classes of trace dye-pesticide mixtures and pharmaceuticals. In this novel quantized data analysis on significantly varied intensity and complex variation spectra classes i.e., many individual, binary-mixtures and some with varied compositions, data normalization is shown to be powerful for improving ML classification accuracy from about 55 % to >99.5 %. Its robustness is demonstrated using inter-instrument driven data variations such as spectral shifts, high noise, and abscissa-flip, with five-fold cross validation of model performance. In addition, on-site quantification of analyte through spectral intensity is also demonstrated. SignificanceThis study opens up a new approach of ML analysis towards realization of next generation field deployable analytical instruments maintaining data privacy. It presents a detailed procedure of quantized spectral data analysis and its implementation in TinyML, attractive for various users and instrument manufacturers. The presented innovative computer-free ML analysis can be employed in all types of spectrometers, meeting the common goal of Raman spectroscopy i.e., accurate identification of complex spectra classes.

Antimicrobial Activity of Anodic Porous Alumina with Controlled Surface Structures.

The antimicrobial properties of anodic porous alumina (APA) formed by the anodization of Al substrates were evaluated. APA surfaces with needle-like projections fabricated under controlled preparation conditions exhibited high antibacterial activity against Escherichia coli and Staphylococcus aureus. In antibacterial tests using APA with different interpore distances, all APA surfaces showed high antibacterial activity against E. coli, regardless of the interpore distance. In the case of S. aureus, in contrast, the smaller the interpore distance in APA is, the higher the antibacterial activity. These results indicate that different bacterial species require different optimal surface structures for antimicrobial activity. The needle-like projections formed on the surface of APA became finer as the interpore distance decreased; the finer the projections, the more efficiently the soft cell membrane of S. aureus is disrupted and the higher the antibacterial activity. On an APA with an interpore distance of 60 nm, the colony formation rate of S. aureus and E. coli was reduced to less than 1/100,000 compared to that of a nonanodized Al substrate. The fabrication process described in this article is expected to make it possible to impart antimicrobial properties to the surfaces of various Al products.

Interfacial structure and properties of anodized 6061 Al alloy joints by ultrasonic-assisted hot dipping and soldering using a Sn–9Zn–2Al filler metal

Al alloy joints soldered with Sn-based filler metal are susceptible to corrosion and early failure when exposed to moisture, resulting in severe accidents and substantial economic losses. This study proposes a method to prevent galvanic corrosion by separating Al alloys and Sn-based filler metals with an insulating barrier layer of anodized aluminum oxide (AAO) composed of Al2O3. The successful joining of anodized aluminum alloy (AAA) with Sn–9Zn–2Al was achieved through ultrasonic-assisted hot dipping and soldering in air at 240 °C. Microstructural examination revealed strong bonding between the solder alloy and AAO, with the solder infiltrating the AAO nanotubes and a transition layer consisting of two sublayers at the interface: amorphous ZnO mixed with nanocrystals (ZnO and Al2O3) and amorphous Al2O3. The shear strength of the joints ranged from 31.8 to 32.8 MPa when subjected to ultrasonic hot dipping for 0.5–2.0 s, with no significant difference observed. Fracture initiation and propagation occur within the transition layer at the interface. The shear strength of joints subjected to dipping for more than 3.0 s decreased slightly to 27.9 MPa due to localized peeling off of AAO from the Al substrate. The formation of the interface involves the segregation of Al and Zn on the liquid filler metal surface, driven by differences in atomic activity. Due to the jet force from cavitation, an Al-rich liquid infiltrates the nanotube, resulting in the formation of Zn–O at the interface and Al–O both at the interface and within the nanotube. Throughout this process, the wetting model shifts from a Cassie state to a near-Wenzel state. Immersion tests of two types of joints, Al/SnZnAl/Al and AAA/SnZnAl/AAA, confirmed that galvanic corrosion of Sn/Al was completely inhibited by the latter. Consequently, AAA joints demonstrate excellent corrosion resistance, validating this approach as a promising solution to the Al/Sn galvanic corrosion issue.

A Rapid, Efficient Method for Anodic Aluminum Oxide Membrane Room-Temperature Multi-Detachment from Commercial 1050 Aluminum Alloy.

For commercial processes, through-hole AAO membranes are fabricated from high-purity aluminum by chemical etching. However, this method has the disadvantages of using heavy-metal solutions, creating large amounts of material waste, and leading to an irregular pore structure. Through-hole porous alumina membrane fabrication has been widely investigated due to applications in filters, nanomaterial synthesis, and surface-enhanced Raman scattering. There are several means to obtain freestanding through-hole AAO membranes, but a fast, low-cost, and repetitive process to create complete, high-quality membranes has not yet been established. Here, we propose a rapid and efficient method for the multi-detachment of an AAO membrane at room temperature by integrating the one-time potentiostatic (OTP) method and two-step electrochemical polishing. Economical commercial AA1050 was used instead of traditional high-cost high-purity aluminum for AAO membrane fabrication at 25 °C. The OTP method, which is a single-step process, was applied to achieve a high-quality membrane with unimodal pore distribution and diameters between 35 and 40 nm, maintaining a high consistency over five repetitions. To repeatedly detach the AAO membrane, two-step electrochemical polishing was developed to minimize damage on the AA1050 substrate caused by membrane separation. The mechanism for creating AAO membranes using the OTP method can be divided into three major components, including the Joule heating effect, the dissolution of the barrier layer, and stress effects. The stress is attributed to two factors: bubble formation and the difference in the coefficient of thermal expansion between the AAO membrane and the Al substrate. This highly efficient AAO membrane detachment method will facilitate the rapid production and applications of AAO films.

Characterization of electro-adhesion using surface waves generated and detected by Laser-Ultrasonics

Studying and understanding adhesion characteristics between a coating and its substrate is important for improving the reliability of a thin film’s adhesion. To the best of the authors’ knowledge, this work studies for the first time a specific electro-adhesion process using Laser-Ultrasonics. An electric field source is applied to a convenient sample composed of a polyvinyl chloride (PVC) layer on an aluminum (Al) substrate. The aim is to investigate the impact of different electro-adhesion levels on the propagation of surface acoustic waves (SAW), which are generated by a pulsed laser and detected using an interferometer. This non-destructive and non-contact experimental setup allows us to determine the surface modes dispersion curves for each adhesion level. A theoretical model is developed to numerically solve the dispersion relation in order to analyze the influence of the interface quality on the dispersion curves. These ones have also been obtained by the finite element method (FEM) allowing us to predict the shape of the experimental signals. This research paves the way for future studies of specific adhesion phenomena across different materials.

Scanning Acoustic Microscopy Characterization of Cold-Sprayed Coatings Deposited on Grooved Substrates

AbstractThe effect of non-planar substrate surface on homogeneity and quality of cold-sprayed (CS) deposits was studied by scanning acoustic microscopy (SAM). Fe coatings were cold-sprayed onto Al substrates containing artificially introduced grooves of square- and trapezoid-shaped geometries, with flat or cylindrical bottoms. The Al substrates were either wrought or cold-sprayed, to comprehend their prospective influence on the Fe coatings buildup. SAM was then used to assess morphological properties of the materials from the cross-view and top-view directions. The microstructure below the surface of the studied samples was visualized by measuring the amplitudes of the reflection echoes and the velocity of the ultrasonic waves. The SAM analysis revealed that the regions of coating imperfections around the grooves are larger than what is suggested by standard scanning electron microscopy (SEM) observations. Furthermore, we found that the seemingly non-influenced coating regions that appear perfectly homogeneous and dense in SEM do, in fact, possess heterogeneous microstructure associated with the individual CS nozzle passes.

Solar to Thermal Energy Conversion Potential of Carbon Nanotubes Modified Copper Oxide Nanocomposite Thin Film Solar Selective Absorbers

AbstractCarbon nanotubes modified copper oxide nanocomposite (CNTs–CuO NC) selective absorbers were prepared through a sol‐gel method by varying weight percentage of CNTs and coated on aluminum (Al) substrates using a dip coating technique to form thin films (TFs). The surface morphology of CNTs–CuO NC TF examined by scanning electron microscopy disclosed linear arrangement of CNTs–CuO NC TF with average particle diameter of 200±30 nm. The X‐ray diffractometer analysis of the CNTs–CuO NC TF revealed the presence of CuO in monoclinic crystal structure. Moreover, the X‐ray diffractometer analysis disclosed good crystalline quality of the CNTs–CuO NC TF and average crystallite size of the CuO and CNTs–CuO NC TF was found to be 69.38 and 85.94 nm, respectively. The energy dispersive X‐ray spectrum of CNTs–CuO NC TF ascertained the presence of Cu, O and C elements with atomic weight proportion of 71.07, 21.61 and 7.32 %, respectively. The functional groups investigation by FTIR spectroscopy exhibited distinct spectral features of CNTs and the peaks observed at 516.78 and 588.70 cm−1 correspond to the characteristic vibrations of metal‐oxygen (M−O) bond that indicates the presence of CuO in the hybrid CNTs‐CuO NC TF. The optical property of the CNTs–CuO NC TF with CNTs weight proportion of 0.5 % inspected through UV‐Vis‐NIR spectroscopy exhibited high solar absorptance and thermal emittance values of 85.9 and 4.3 %, respectively. The observed highest solar selectivity value of 19.98 suggests that the CNTs–CuO NC TF coating can be apparently used as solar selective absorber.

Surface pre-treatment of aluminum alloy for mechanical improvement of adhesive bonding by maple-assisted pulsed laser evaporation technique.

Adhesive joints are widely used for structural bonding in various industrial sectors. The performance of bonded joints is commonly attributed to the cleanliness of the substrate and the pre-treatment of the surfaces to be bonded. In this study, the Matrix Assisted Pulsed Laser Evaporation (MAPLE) deposition technique was used for surface modification of aluminum (Al) plates by the deposition of poly(propylene glycol) bis(2-aminopropyl ether) (PPG-NH2) of different number average molecular weights (Mn) of 400 g mol-1, 2000 g mol-1, and 4000 g mol-1, respectively. Fourier-transformed infrared spectroscopy (FT-IR) analysis indicated the characteristic peaks for the deposited layers of PPG-NH2 of different molecular weights in all cases while scanning electron microscopy (SEM) revealed continuous layers on the surface of Al plates. In order to demonstrate alterations in the wettability of Al substrates, a crucial aspect in surface treatment and adhesive bonding, measurements of contact angles, surface free energies (SFE), and adhesion work (W a) were conducted. The tensile strength measurements were performed using the lap-joint test after applying the commercial silyl-based polymer adhesive Bison Max Repair Extreme Adhesive®. It was evidenced that at higher values of the SFE and W a, the tensile strength was almost 3 times higher for PPG-NH2 with Mn = 4000 g mol-1 compared with the untreated Al sample. This study provides valuable insights into the successful application of the MAPLE technique as a pre-treatment method for reinforcing adhesive bonding of Al plates, which can lead to improved mechanical performance in various industrial applications.