Al Substrate Research Articles

Microwave‐Assisted Fabrication of Superamphiphobic Surfaces on Aluminum Substrates

The field of superamphiphobic surface fabrication has evolved rapidly in the last decade; however, research on important issues such as sustainability and green chemistry procedures is still scarce. Herein, a simple method of microwave irradiation (MW) to minimize energy consumption during the preparation of superamphiphobic aluminum (Al) surfaces is reported. Al substrates are first etched in diluted HCl solutions to generate a microstructure and then irradiated in a commercial microwave unit for several time intervals, temperatures, and pressures. The surfaces are then coated with different compounds, and the wettability is tested with high and very‐low surface tension liquids. Optical profilometry and scanning electron microscopy images show that the density of hierarchical micro‐nanostructures increases with MW time, temperature, and pressure. At 170 °C and 7.9 bar, the surfaces present a high density of structures and re‐entrant topographies. The obtained coatings display excellent repellence to liquids with surface tensions as low as 27.5 mN m−1. X‐ray photoelectron spectroscopy data show the importance of efficient surface functionalization for the production of superamphiphobicity in Al substrates. The results show that MW irradiation of Al substrates can be a green and efficient method for fabricating superamphiphobic surfaces.

A bifunctional epoxy coating doped by cerium (III)-8-hydroxyquinoline: Early self-reporting and stimuli-responsive inhibition on corrosion of Al substrate

Recently, anti-corrosion coatings with auto-inhibition and self-reporting on their premature flaws are becoming more and more attractive. In this work, we engineered a cerium nitrate/8-hydroxyquinoline (Ce-HQ) hybrid pigment to endow epoxy coatings with corrosion self-inhibiting and fluorescent self-reporting performances via molecule design. The Ce-HQ pigments were synthesized by physical mixture and then dispersed into the commercial epoxy coating. Once the epoxy coating gets degraded, the underneath aluminum alloy matrix may corrode to produce Al3+ ions, which can compete with Ce3+ ions in the Ce-HQ complex, and then chelate with dissociative 8-HQ to form fluorescent Al-HQ complex, due to the higher bonding strength of Al3+ with 8-HQ than Ce3+ ions. Thus, not only the responsive releasing of Ce3+ ions and 8-HQ can inhibit the underlying Al alloy, but the newly formed Al-HQ complex could indicate the location and severity of coating flaws through fluorescent emission under UV light. Electrochemical impedance evidenced that the composite epoxy coating containing 1 % mass Ce-HQ presents high corrosion resistance even after 504 h of salt spray test, showing 90 % corrosion refraining efficiency. This work may enlighten an approach to developing self-healing and self-diagnosis coating for premature corroded Al alloy beneath coatings via reactive release and fluorescent visualization.

Anodization Time Effect on Silver Particles Deposition on Anodic Oxide Coating over Al Produced by Plasma Electrolytic Oxidation

In this study, 6061 Al alloy was galvanostatically anodized under the Plasma Electrolytic Oxidation (PEO) condition. A factorial design of 22 was carried out using two variables (anodization time and presence of silver in the electrolyte) on two levels, i.e., 20 and 60 min of anodization and the absence/presence of silver ions in the electrolyte. The Al anodization was performed in sodium silicate electrolyte, applying a constant current density of 20 mA cm−2. The oxide characterization was performed by Scanning Electron Microscopy (SEM), surface roughness analysis (RMS), Energy Dispersive Spectroscopy (EDS), Rutherford Backscattered Spectroscopy (RBS), and Grazing Incidence X-ray Diffraction (GIXRD). The SEM micrographs revealed an irregular porous structure with cracks on the oxide surface composed of a thin crystalline layer of γ-Al2O3 over the Al substrate. From EDS and RBS analysis, it was possible to identify the elements Al, O, Si, Ag, and Na, demonstrating that a shorter anodization time (20 min) led to a significant amount of silver deposits on the outer layer of the oxide coating, mainly deposited in the surroundings of the pores. Conversely, the silver content on the PEO film anodized for 60 min was meager. These results demonstrated that the anodization time was the critical control variable for the amount of silver deposited over the oxide film. The shorter the anodizing time, the higher the silver content on the PEO coating.

Wetting and Interfacial Chemistry of New Pb-Free Sn-Zn-Ag-Al-Li (SZAAL) Solder with Cu, Ni, and Al Substrates

This paper presents the results of the Ni substrate wetted with the liquid Sn-Zn eutectic alloy with the addition of Ag, Al, and Li (84.3 at.% Sn, 13.7 at.% Zn, 1 at.% Ag, 0.5 at.% Al, and 0.5 at.% Li-SZAAL). The wetting tests were performed using two methods: the wetting balance tests (WBT) and the sessile drop (SD) method at 250 °C, in the presence of an ALU33® flux. The wetting times were 5, 20, 60, 180, and 1800 s. Next, the microstructure of selected solidified solder joints was investigated using scanning electron microscope. The Ni-Zn system's intermetallic phases (IMCs) were identified at the solder–Ni substrate interface. The kinetics of the formation and growth of the IMC layer was determined. Interfacial tension and contact angle (CA) values were calculated from WBT measurements in the presence of the ALU33® flux. Interfacial tension was compared to surface tension from the maximum bubble pressure and CA values to those obtained using the SD method. The value of the contact angle of SZAAL on Cu (39°) substrate is lower than on Ni (43°). For the comparison, also the interaction between SZAAL and Cu substrate was measured. After 1800 s, the IMCs thickness is significantly reduced for Ni pad than for Cu substrate. The study found that the addition of Al, Ag, and Li improved the tensile strength and wettability of Sn-Zn eutectic-based alloys.

A photothermal self-healing superhydrophobic coating with anti-frosting and anti-corrosion properties

The surface frosting and corrosion of Al alloy limit its diversified application. The self-healing superhydrophobic coating opens a new door for the durability and stability of aluminum alloys. However, it remains challenges to simultaneously achieve efficient self-healing efficiency and strong coating adhesion. Here, a coating with great wear resistance and fast self-healing was constructed by introducing thermodynamically stable coordination bonds and highly mobile hydrogen bonds. The prepared coatings (named Al/ZnO-P.I.Z-FAS@PDA) exhibited excellent wear resistance, the super-hydrophobicity (water contact angle >150°) remained after 200 wear cycles. The coating could repair scratches for only 5 min at 80°C. And chemical damage repair could be achieved with the coating at room temperature for 40 min. This was mainly due to the hierarchical structure of non-covalent bond gradient distribution. Hydrogen bonds facilitate the migration of the fluorine chains, and coordination bonds ensure a tight connection between the coating and the base layer. In addition, the interfacial interactions between the materials in the coating were discussed. Based on the super-hydrophobicity of the coating and the dual repair of physical-chemical damage, the coating exhibits excellent self-cleaning, abrasion resistance, frost and corrosion resistance as well as outstanding frost repair and corrosion repair capabilities. In particular, thanks to the photothermal effect of PDA, the self-healing performance of as-prepared coating could come true under sunlight. The coatings in this paper provide directions for the application of Al substrates under harsh conditions.

Structure-Performance Relationships of Complexing Agents on the Chemical Mechanical Polishing of 6063 Aluminum Alloy

Aluminum alloy has wide applications in many industries due to its unique properties. Chemical mechanical polishing (CMP) is commonly used to treat aluminum alloy to generate mirror-finish surface. In this study, the effects of pH and H2O2 concentration on the CMP of 6063 aluminum alloy were studied. Better CMP performance was obtained in basic media with 1.0 wt% H2O2. Moreover, complexing agents with different structures and functional groups were evaluated for the CMP of Al-alloy, and their structure-performance relationship was systematically studied. It was found that complexing power, steric hindrance and electrostatic repulsion of complexing agents were important factors determining material removal rate and surface roughness. The complexing agent with high complexing power can favor the dissolution and Al substrate. The complexing agent with large steric hindrance and high charge density can form a stable boundary layer on the surface of substrate and improve its dispersion ability, thereby improving MRR and surface quality. In addition, the amino functional groups of complexing agents exist in the form of neutral molecules at pH 10, which is inferior to carboxyl complexing agents due to their poor static repulsion. XPS analysis confirmed the anchoring of carboxylate anions on the sample surface.

Reinforcement study of anodizing treatment with various temperatures on aluminum substrates for stronger adhesive bonding with carbon fiber composites

Aluminum alloy and carbon fiber reinforced plastic (Al-CFRP) composite are usually applied to the lightweight design and manufacture of important field equipment due to the lightweight and high strength. However, the high performance and industrialization of Al-CFRP composites are restricted by degumming issues caused by poor wetting and compatibility, and weak mechanical occlusion of bonding interface between epoxy resin and substrates. In this study, anodizing treatments with three temperatures were employed to etch Al substrate surface for various pore structure, CFRP panels were grinded to create a strong CFRP/epoxy bonding interface to compare the performances changing resulting from treatments on Al substrate surface. Resin pre-coating (RPC) technique was used to eliminate the originally existing defect caused by macromolecular epoxy at the root of porous Al substrate in common adhesive bonding. The carbon nanotubes (CNTs) were utilized to improve the bonding interfaces and adhesive layers. The single lap shear results showed the best shear strength of anodized specimen at 30 °C was up to 23.4 MPa improved by 268.9 % than base. Failure modes exhibited the weaker debonding failure at Al/epoxy interface was converted into dominated fiber fracture and delamination failure of CFRP after combined surface treatments. These results indicate associative treatments of anodizing at 30 °C and CNTs-contained RPC are effective and contribute to developing a solution in industrial application of high-performance Al-CFRP composites.

Interaction between bilayer borophene and metal or inert substrates

Bilayer borophene have gradually come into our horizons in experimental and theoretical studies due to the superior antioxidation and advantageous to the exfoliation compared with monolayer borophene. Using systematical first-principles calculations, we explore the interactions between bilayer borophene and various metal surfaces of Ag (111), Au (111), Al (111), Cu (111) and inert substrates of monolayer hexagonal boron nitride (h-BN), monolayer MoS2 and GaN (0001) surface. The electronic band structures, partial density of states, total electron distribution and Bader charge analysis have been systematically calculated to explore for the interaction strength. The orbital hybridization and chemical bonding occur in the interface of four metals and GaN heterostructures attributed to the active surficial atoms, differ from Van Der Waals interaction of borophene-MoS2 and h-BN inert substrates. In addition, we find that metal Al (111) with smaller work function and inert substrates of monolayer h-BN and MoS2 have tiny tunneling barrier at the interface of bilayer borophene-substrates, and might be appropriate to the synthesis of bilayer borophene.

Comparative strengthening of intermetallic compounds produced in situ by friction stir processing on different aluminum alloy matrixes

The composite technology based on friction stir processing (FSP) can enhance the strength of Al alloys while retaining the original toughness and ductility of Al alloys, thus achieving an improvement in the overall performance of the composites. Ni/Al composites were prepared in three typical Al matrixes by optimized FSP, and the effect of in situ generated intermetallic compounds on the strengthening of different Al substrates during the FSP was investigated. It was found that the reinforcing phase of Ni/Al composites was mainly in situ generation of Al3Ni intermetallic compound using energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM), and the more the number and more uniform the distribution of Al3Ni reinforcing phase, the better the mechanical properties of Ni/Al composites. The results indicate that the Ni/Al composites formed from different series of Al alloy matrix, the Ni/6061Al composite has the most remarkable microstructure uniformity, the greatest strength increase and the least elongation decrease, which is conducive to improving its strength without affecting the processing properties of the 6061 Al alloy. The finding opens new opportunities for the preparation of Ni/Al composites with excellent properties from 6061 Al alloys.

UV-durable superhydrophobic ZnO/SiO2 nanorod arrays on an aluminum substrate using catalyst-free chemical vapor deposition and their corrosion performance

Dense ZnO nanorod arrays were obtained directly on Al substrate for the first time using catalyst-free chemical vapor deposition. The influence of temperature on the surface topography of ZnO nanostructures was analyzed. Then the ZnO nanorod arrays surface was coated with SiO2 films via pulsed laser deposition. After modifying with stearic acid, the Al/ZnO/SiO2 nanorod arrays showed superhydrophobic properties with a water contact angle of up to 157.9°. Notably, these Al/ZnO/SiO2 nanorod arrays exhibited UV resistance, and the water contact angle remained almost constant under UV light exposure for a long time. The electrochemical measurements showed that ZnO/SiO2 nanorod arrays had an excellent protective effect on metal Al. These results provided a basis for a feasible method for the corrosion protection of metals.

Ultraviolet ultranarrow second-order magnetic plasmon induced reflection of lifted 3D metamaterials for slow light and optical sensing

We theoretically demonstrate the ultraviolet (UV) high-order magnetic plasmon induced reflection (PIR) by lifting metamaterials consisting of three-dimensional aluminum split-ring resonators (3D-AlSRRs) with the effect of substrate being reduced. The strong plasmonic coupling between the second-order magnetic plasmon (2nd MP) of the lifted 3D-AlSRRs and the surface plasmons polaritons propagated on the Al substrate is achieved and leads to an ultranarrow PIR with linewidth of 4.6 nm in the UV range. The UV PIR effect is theoretically explained by an analytical Fano coupling model. In addition, the lineshape and position of the UV 2nd MP induced PIR can be artificially adjusted through varying the geometric parameters. The maximum of the group index of about 120 is achieved in the UV range. In addition, the sensitivity (S) and figure of merit (FoM) of the lifted 3D-AlSRRs are obtained to be 240 nm/RIU and 52, respectively. Our designed 3D metamaterials open a new path for the designing of multi-functional devices for such as slow-light and high sensitive optical sensor in the UV range.

Realizing high-resistivity and low-loss Fe–Si–Al based soft magnetic powder cores through interfacial chemistry regulation

As a symbolic ceramic oxide, SiO2 is one of the most important insulating layers of soft magnetic powder cores (SMPCs). Thus, the reaction of SiO2 with Fe–Si–Al based SMPC substrates during annealing, the induced phase transition of the core-shell structure, and the influence of the latter on the magnetic characteristics of SMPCs are worth investigating. In this study, Fe–Si–Al based SMPCs were successfully synthesised using fluidised-bed chemical vapour deposition (FB-CVD) at various times, combined with an electric pressure-assisted sintering method and high-temperature annealing. The evolution of the insulating layers with different thicknesses was investigated. With increasing thickness, the insulating layers (shell) gradually transformed into Al2O3 and the Fe–Si–Al substrate (core) to Fe3Si. The newly formed Al2O3 and Fe3Si increased the coercivity and saturation magnetisation of the SMPCs, while the hysteresis loss increased with thicker insulating layers. The generated Al2O3 improved the integrity of the insulating layers, preventing possible point contact between particles, and significantly reduced the Eddy current losses. The SMPCs with the thickest insulating layers (7#) exhibited superior magnetic properties (Ms = 129.3 emu/g, resistivity = 2.51 mΩ cm, total loss = 593.1 kW/m3 at 10 mT and 100 kHz; 18.0% reduction from the maximum). Thus, a precise method of adjusting the magnetic behaviour of Fe–Si–Al based SMPCs was developed through the novel approach of building SMPCs with inorganic ceramic insulating layers, enabling a comprehensive understanding of the relationship between the thickness of insulating layers and magnetic properties, which is of significance for industrial production.

Infusing Silicone and Camellia Seed Oils into Micro-/Nanostructures for Developing Novel Anti-Icing/Frosting Surfaces for Food Freezing Applications.

Undesired ice/frost formation and accretion often occur on food freezing facility surfaces, lowering freezing efficiency. In the current study, two slippery liquid-infused porous surfaces (SLIPS) were fabricated by spraying hexadecyltrimethoxysilane (HDTMS) and stearic acid (SA)-modified SiO2 nanoparticles (NPs) suspensions, separately onto aluminum (Al) substrates coated with epoxy resin to obtain two superhydrophobic surfaces (SHS), and then infusing food-safe silicone and camellia seed oils into the SHS, respectively, achieving anti-frosting/icing performance. In comparison with bare Al, SLIPS not only exhibited excellent frost resistance and defrost properties but also showed ice adhesion strength much lower than that of SHS. In addition, pork and potato were frozen on SLIPS, showing an extremely low adhesion strength of <10 kPa, and after 10 icing/deicing cycles, the final ice adhesion strength of 29.07 kPa was still much lower than that of SHS (112.13 kPa). Therefore, the SLIPS showed great potential for developing into robust anti-icing/frosting materials for the freezing industry.

Optimization of heat-dissipated structures with cuprous oxide deposits to improve thermal management of high-brightness LED arrays

This project reports on improving the thermal performance of light-emitting diode (LED) packages based on an optimized thermal structure with a sprayed cuprous oxide coating. Eighteen orthogonal arrays of LED aluminum plates were used and the influence of the parameters of thermal dissipation structure on the LED junction temperature was established. The junction temperature of the LED assembly is developed by various heat dissipation structures based on Taguchi methods. The experimental results show that by measuring the temperature of the 12W LED module, the best results were compared with the lowest values in the overall experiment, where the junction temperature dropped from 67°C to 51°C Also, the contribution of the error to the total variance is about 0.8%, indicating that the experiment is quite successful and robust results. It was found that lower junction temperature values were obtained with optimized heat sink structures with Cu2O-coated Al substrates, and the thermal performance of the LEDs was further improved.

Corrosion Behavior of Fe2O3/Alumina Layer Produced by Plasma Electrolytic Oxidation of 6061 Al Alloy

This study looked into the influence of iron nitrate (Fe(NO3)3 on the corrosion behavior of a 6061 Al alloy treated by a plasma electrolytic oxidation coating (PEO). PEO coatings were fabricated on Al alloy samples under AC conditions utilizing an alkaline-aluminate electrolyte containing 0 and 5 gr of Fe(NO3)3. Surface examination demonstrated that some Fe2O3 particles were effectively integrated into the coating layer produced in a solution containing Fe(NO3)3. In addition, the porosity and the size of micropores made due to plasma activity were significantly reduced after the PEOO treatment of the 6061 Al substrate in an electrolyte containing Fe(NO3)3. Accordingly, the coating formed in the electrolyte with Fe(NO3)3 exhibited superior corrosion resistance to that treated in the electrolyte without Fe(NO3)3.

Inorganic ferrite brown; transformation towards a versatile pigment for energy efficient constructions

The present work demonstrates a multifunctional brown inorganic ferrite pigment series, which is free of highly toxic elements, via solid-state ceramic method. Partial replacement of chromophore Fe3+ by Al3+ in the pigment composition (ZnFe1.9Al0.1O4) brought structural distortion in its octahedral geometry that further induced compressive stress inside the crystal unit cell. The introduction of even 5 mol% of Al3+ ions incorporated in place of Fe3+ could able to promote the pigment reflectance profile 25 units higher compared to parent system, particularly with significant colour improvement. Acrylic coating of the pigment on Al substrate was equally well in displaying good colour strength and temperature shielding ability (∼2 °C) with respect to ZnFe2O4. The pigment stands out with its promising anticorrosive performance over the commercial toxic candidates, chromates and phosphates, exhibiting excellent Rct = 4.1 × 109 Ωcm2. The durability of 20 wt% pigment loaded epoxy coating on steel activates through combined action of Zn(OH)2 and FeOOH film mechanism. Since, the pigment exhibits intense colour, high NIR solar reflectance and robust corrosion resistance properties, their use as a high-performance multifunctional pigment is indispensable.

Alumina Coatings Containing Niobium Pentoxide Polymorphs Prepared by Plasma Electrolytic Oxidation of Aluminum

This study explores the experimental parameters related to the production of Nb2O5 over alumina coatings produced by plasma electrolytic oxidation (PEO) and evaluates its use in photocatalytic applications. The influence of niobium precursor concentration and the electrolyte temperature on the electrochemical, morphological, and compositional responses are investigated using chemometric tools. The experimental design provides a geometrical representation of experimental parameters and shows the effect of the anodizing conditions on the pore density and the anodization curves. The samples are prepared at a constant current (10 mA cm−2) under the PEO regime. The coatings reveal a porous structure and crystalline phases of Nb2O5 and γ‐Al2O3. A preliminary photodegradation test under UV radiation and utilizing Rhodamine B (RhB) solution shows the best photocatalytic performance for the sample produced by the highest Nb salt concentration (16.0 g L−1) and highest temperature (18.7 °C). These results are attributed to a higher niobium content in this sample and crystalline phases of Nb2O5 over the Al substrate.

Layer-by-layer fabrication of self-cleaning superhydrophobic surface made from Carboxymethylcellulose and ZnO quantum dots: A combined experimental and computational study

Non-health hazardous self-clean coating materials have fascinated and assumed immense significance from both academia and industries. Herein, we put forward a facile and efficient technique to design a self-clean coating material by employing selective organic (carboxymethylcellulose (CMC)) and inorganic (ZnO quantum dots (QDs)) fillers. Computed water repellence nature through interfacial solid-liquid-vapor interactions well compared with experimental outcomes. Interestingly, experimental water contact angle (WCA) (159.2 ± 2°) and simulated binding energy with aluminum (Al) substrate (−3044.12 kcal/mol) revealed the subtle balance of the excellent water repellence on one side while interfacial interactions confirmed sufficient adhesion with the substrate on the other side of the proposed coating. Fluoro functionalized CMC and ZnO QDs weaken the matrix interactions with water molecules by providing a much desirable combination of micro and nano-scale grooves to the exposed coating surface. The adopted technique for synthesis of such a superior coating is simple for application with commercially available materials and across surfaces in automobiles, biomedical instruments, and structural glasses.

Directional fretting wear behaviour of constrained groove pressed aluminium sheet

Wear behavior of the constrained groove pressed (CGP) aluminium (Al) sheet was examined along both the longitudinal as well as transverse direction using fretting wear tester. The results unequivocally showed a significant diminution (up to 1.2 times for one pass) in the coefficient of friction (COF) which leads to significant improvement in the wear resistance after each pass of CGP when compared to the as-received (AR) sample. Subsequently, wear rate in the CGP processed sample was found to be lower along the transverse direction (∼ 0.38 ± 0.08 ×102 µm3/N.mm) compared to that in the longitudinal direction (∼ 0.87 ± 0.12 ×102 µm3/N.mm) for one pass sample. Along longitudinal direction the major wear mechanism is discerned to be severe abrasion followed by crater formation in the samples with lower strain (i.e. 1 pass), however, it is delamination followed by dense tribolayer formation in the highly strained sample along transverse direction. Increasing fraction of oxygen content in energy dispersive spectroscopy result support the formation of dense tribolayer along transverse direction which attribute to formation of protective layer in the wear scar. The substantial decrement in the wear volume and hence wear rate after severe deformation is credited to the significant strain imposed in the sample, which leads to significant hardness up to ∼ 1.5 times for 3 pass CGP (44.5 VHN) due to the grain refinement from AR to 3 pass CGP i.e., ∼ 21.64 µm to ∼ 5.60 µm. Therefore, effect of grain refinement on the mechanical as well as wear properties with CGP on Al substrate has also been established.

Icephobicity of Hierarchically Rough Aluminum Surfaces Sequentially Coated with Fluoroalkyl and PDMS Alkoxysilanes.

Superhydrophobic surfaces fabricated by grafting 1H,1H,2H,2H-heptadecafluorodecyl trimethoxysilane (FD-TMS) and polydimethylsiloxane triethoxysilane (PDMS-TES) onto a nano-micro hierarchical aluminum (Al) surface are considered to possess substantial anti-icing functionality, with delayed freezing and low ice-adhesion strength (IAS). Verifying the impacts of PDMS and the synergism of PDMS and FD on the anti-icing performance is the goal of this study. Roughness, one of the prerequisites for superhydrophobicity, was obtained by etching Al substrates in aqueous HCl, followed by immersion in boiling water. FD-TMS and PDMS-TES were then coated on the rough Al substrates layer by layer; a congener coated with a single layer was also prepared for comparison. The FD-PDMS1.92 (1.92 wt.%) coating, in which FD-TMS and PDMS-TES were used as primary and secondary coating materials, respectively, exhibited superior icephobicity, with the lowest IAS of 28 kPa under extremely condensing weather conditions (-20 °C and 70% relative humidity, RH) and the longest freezing delay time of 230 min (at -18 °C). These features are attributed to the incorporation of a dense coating layer with a low-surface-tension FD and the high mobility of PDMS, which lowered the contact area and interaction between the ice and substrate. The substrate coated with FD-PDMS1.92 exhibited improved durability with an IAS of 63 kPa after 40 icing/melting cycles, which is far less than that achieved with the FD single-layer coating.