Aluminum Structures Research Articles

Analyzing the Li-Al-O Interphase of Atomic Layer-Deposited Al2O3 Films on Layered Oxide Cathodes Using Atomistic Simulations.

Alumina surface coatings are commonly applied to layered oxide cathode particles for lithium-ion battery applications. Atomic layer deposition (ALD) is one such surface coating technique, and ultrathin alumina ALD films (<2 nm) are shown to improve the electrochemical performance of LiNixMnyCo1-x-yO2 materials, with groups hypothesizing that a beneficial Li-Al-O product is being formed during the alumina ALD process. However, the atomic structure of these films is still not well understood, and quantifying the interface of ultrathin (∼1 nm) ALD films is an arduous experimental task. Here, we perform molecular dynamics simulations of amorphous alumina films of varying thickness in contact with the (0001) LiCoO2 (LCO) surface to quantify the film nanostructure. We calculate elemental mass density profiles through the films and observe that the Li-Al-O interphase extends ∼2 nm from the LCO surface. Additionally, we observe layering of Al and O atoms at the LCO-film interface that extends for ∼1.5 nm. To access the short-range order of the amorphous film, we calculated the Al coordination numbers through the film. We find that while [4]Al is the prevailing coordination environment, significant amounts of [6]Al exist at the interface between the LiCoO2 surface and the film. Taken together, these principal findings point to a pseudomorphic Li-Al-O overlayer that approximates the underlying layered LiCoO2 lattice but does not exactly replicate it. Additionally, with sufficient thickness, the Li-Al-O film transitions to an amorphous alumina structure. We anticipate that our findings on the ALD-like, Li-Al-O film nanostructure can be applied to other layered LiNixMnyCo1-x-yO2 materials because of their shared crystal structure with LiCoO2. This work provides insight into the nanostructure of amorphous ALD alumina films to help inform their use as protective coatings for Li-ion battery cathode active materials.

Hybrid joining of cast aluminum and sheet steel through compound sand casting and induction heating to enable thin-walled lightweight structures

Combining different joining processes to form a hybrid process offers new manufacturing possibilities. Adding induction heating to compound sand casting with additively manufactured lost sand moulds to preheat a metallic solid insert increases the degree of the metallic bond between sheet metal and casting metal. In this study, the manufacturability of thin-walled sheet steel/cast aluminum structures with reduced cast wall thickness in sand casting is characterized for the first time. Enabling lower wall thicknesses of sheet metal/cast metal structures in sand casting shifts the current limits and offers more significant lightweight construction potential. Shear tensile, compression shear, and pullout tests characterize the mechanical properties of the joints. Light microscopic imaging of metallographic samples quantifies the compound zone intermetallic (IMC) thickness. The shear tensile test specimens fail at wall thicknesses below 10 mm in the cast material, so metallurgical bond strength characterization does not occur. Therefore, the compression shear test is used to evaluate the metallurgical bond. Sound metallic bonding with smaller cast wall thicknesses of 8, 6 and 4 mm is achieved. Pullout specimens with 3 mm cast wall thickness further investigate the force-transmitting mechanisms of metallic bond, force-fit and form-locking. It is shown that metallic bonding is the predominant mechanism for force transmission when the compound sand casting process is enhanced by induction heating.

Local structure and ordering of Al atoms in AlxGa1−xN epilayers

In this study, we investigate the local structure of aluminum (Al) in a comprehensive series of AlxGa1−xN epilayers, where the Al concentration spans from the dilute limit to 100%. We analyze grazing incidence Al K-edge tender x-ray absorption spectroscopy data using both linear combination fitting based on reference limit spectra and full quantitative analysis. The results indicate deviations from random cation distribution with varying signs within the explored concentration range. Additionally, we observe a reduction in cationic interatomic distances over a wide concentration range, which contrasts with some previous studies conducted at hard x-ray absorption edges.

Rapid degradation of Omeprazole and highly effective inactivation of E. coli in the UVA-light photocatalytic process with Cu-doped in spinel-structured ɣAl2O3 as a stable catalyst

Herein, a spinel alumina structure photocatalyst was prepared by a one-pot modified sol–gel technique with rational design and unique electronic structure evolution by Cu doping in the γAl2O3 lattice. Based on the obtained results of a full material characterization (incl. NH3-TPD, 27Al solid-state NMR, XPS, HAADF-STEM), the Cu-γAl2O3 xerogel nanomaterial displayed high dispersion of copper, significant quantities of high-density acid sites, an increase of the oxygen vacancies (OVs) on its surface, and high light absorption efficiency. This mesoporous Cu-γAl2O xerogel displayed brilliant photocatalytic performance under UVA-LED, owing to its suitable band gap, degrading around 92 % of 20 mg/L Omeprazole (OMP) in 30 min (pH = 7, catalyst = 50 mg/L). The effect of operating parameters was investigated, such as pH, concentration of Cu-ɣAl2O3/OMP, water matrix, and stability; the synthesized nanomaterial has shown outstanding stability and recyclability for four runs. The reaction mechanism was proposed using scavenging experiments, and EPR spectroscopy, Cu-doping-induced oxygen vacancies to promote charge separation and molecular oxygen activation, generating mainly ∙OH. The OMP degradation pathway was proposed (LC-MS), while the produced Cu-ɣAl2O3 nanomaterial effectively catalyzed the inactivation of >99.99 % E. coli.

Thermal and structural performance of additively manufactured ceramic porous media burners

This study examines the effect of porosity, topology and material composition on the performance of additively manufactured ceramic porous media burners. Thermal-structural simulations of triply periodic minimal surfaces (TPMS) were performed to investigate thermal-stress magnitude and distribution. Alumina and mullite TPMS structures were 3D-printed and tested in a methane-air combustion experiment, where the mullite structures showed superior durability compared to alumina. X-ray imaging revealed notable correlation between predicted high tensile stress regions and experimental crack formation. At equivalent porosity and cell size, TPMS structures with higher specific surface area and tortuosity were found to have lower thermal strain and propensity for structural failure. Structures with these features, namely diamond and I-WP, demonstrated favorable thermal and structural behavior under identical thermal conditions. These findings can guide the design and manufacturing of high-temperature applications with embedded porous structures, such as heat exchangers, catalytic converters, and thermal management systems.

Bending behavior of structured steel sheets with undercuts for interlocking with Al die-cast metal

Due to the current changes in mobility, lightweight design concepts continue to be of particular interest to the automotive industry. One form is the multi-material design, in which the advantageous properties of different materials are combined in one component. In this work, a component made of a steel sheet with stiffening structures of cast aluminum is considered. The joint is created by channel structures with undercuts on the surface of the steel sheet, into which the molten aluminum can flow. After solidification, an interlocking connection is created. The aim of this work is to investigate the influence of a bending operation on the surface structure before the die casting process. Numerical simulations and experimental validations were performed with different bending angles and radii as well as orientations between the channel structure and the punch. The results show that the undercuts on the outer radius are reduced by up to 75% by the bending operation, thus weakening the resulting joint. On the inner radius, the channel opening width narrows by up to 73% and can thus impede the filling with the melt.

Parametric Optimization of a New Gear Pump Casing Based on Weight Using a Finite Element Method

Reducing the weight of the structures and choosing the materials used in mechanical engineering is an important and pressing economic and environmental problem. The design of a gear pump is developed from the point of view of the geometry of the gears, as well as the casing. This paper tested a gear pump casing using the environment of the ABAQUS 2020 system in the field of statistical strength analysis using the finite element method. The tests were carried out on the pump body and the front and rear covers, which were made of three types of materials (cast iron, aluminum, and polycarbonate), at a pressure of 28 MPa. After loading, the maximum stresses in the aluminum casing (177 MPa), the cast iron casing (157 MPa), and the polycarbonate (200 MPa) were determined. The largest stress concentrators are the grooves at the bottom of the pump casing. Rounding the internal chamber of the casing with a radius of 4 mm made it possible to reduce stress in this zone by 10 MPa. The parametric optimization of the front and back covers of the gear pump made it possible to reduce the total weight of the aluminum structure by 14%, the cast iron by 12%, and the polycarbonate by 16%. The 3D models show areas of minimal stress where the size and weight of the structure could be reduced in the future using a comprehensive approach involving parametric and topological analysis.

Co–Fe–oxide nanoparticles supported on the various highly dispersed matrices: the effect of the carrier on structural and magnetic properties

sA series of mixed oxides was synthesized by deposition of the guest phase on the highly dispersed oxide matrix. Fumed nanooxides SiO2, Al2O3, SiO2/Al2O3, and SiO2/Al2O3/TiO2 with the specific surface area of 65–91 m2/g were selected as highly dispersed matrices. Co–Fe mixed oxides with the general formula Co4xFexOy (Co: Fe = 4: 1) were deposited as the guest oxides using the two-step method: (i) solvate-stimulated modification of the surface of fumed nanocarriers with the mixture of cobalt nitrate (II) and iron (III) formate and (ii) subsequent heat treatment up to 600 °C to form Co4xFexOy. The aim of this paper was to study the influence of the composition and structure of fumed oxide matrices and deposited guest phase on the morphology of the resulting composites in the gaseous and aqueous media using the XRD, XPS, FTIR, nitrogen adsorption and SEM/EDX, as well as quasi-elastic light scattering (QELS) methods. The low-temperature nitrogen adsorption isotherms have a sigmoidal shape with a narrow hysteresis loop characteristic of mesoporous materials. The specific surface area (SBET) of the composites varies from 48 to 82 m2/g, showing a tendency towards a decrease in the SBET values by 10–26% in comparison with the initial nanocarriers. The SEM data show the denser aggregate structure of nanocomposites compared to the initial carriers. The primary particle size was in the 30–60 nm range and the EDX data confirm the formation of a guest phase on the mixed aluminosilicate carriers, mainly in the surface patches corresponding to the alumina structure. According to the QELS data, there is a tendency to form aggregates of 100–10 μm in size in the aqueous media. The XRD method shows that the deposited metal oxides are in the form of crystalline phases of Co3O4 with the crystallites of 25–26 nm in size for the individual SiO2 and Al2O3 nanocarriers and 34–37 for the mixed ones, but the iron oxide reflections were not identified for the composites. XPS observation demonstrates the signal of Fe 2p electrons as the form of Fe2O3 oxide in the surface layer of nanocomposites as well as Co 2p as the Co3O4 and Co(OH)2.

Investigation and optimization of load characteristics of a multi-stage load-reduction structure for vehicles during high-speed vertical water entry

Vehicles are subjected to intense impact loads during water entry at high speed, so some appropriate measures are taken to reduce the impact response of the structure. In this paper, a multi-stage load-reduction structure composed of foam aluminum and cavitation structure is designed to improve the load characteristics of high-speed vehicles. Its three-dimensional numerical model is established based on the Coupled Euler-Lagrange (CEL) method. The accuracy of the numerical simulation was verified by comparison with various experimental results of the sphere and AUV head section, and irrelevant grids were obtained. The simulation of a vehicle with and without a multi-stage load-reduction structure was carried out to study the load characteristics under the influence of different parameters such as vertical velocity and relative density of foam aluminum. Researches were also carried out to select the optimal parameters. The results show that the impact acceleration and the optimal density increase synchronously with the initial velocity. The installation of the multi-stage structure transforms the single impact of direct water entry into three reduced acceleration peaks, and finally realizes the load reduction. When the velocity is 100, 200 or 300 m/s, the load reduction rates under the optimum density are up to 84.6%, 83.7% and 79.3%.

The effect of subgrain mobility on recrystallization kinetics: phase-field simulation study

The influence of grain boundary mobility on the recrystallization process (ReX) was investigated in this study using the phase-field approach. In accordance with the Read-Shockley equation, for the interfacial mobility as a function of the misorientation angle, the resulting microstructural evolution was studied. It was observed that the disappearance of low-angle grain boundaries (LAGBs) during the ReX process caused high-angle grain boundaries to move faster during the subsequent ReX stages. For materials with high stacking energy, such as aluminum, LAGBs were additionally found to play a significant role in the ReX process. The kinetics of the ReX process, coupled with grain growth, showed the typical behavior observed in fine-grained structures of pure aluminum.

The effect of layer interface on recrystallization behavior of layered aluminum: An in-situ EBSD study

In recent years, layered heterogeneous metallic materials have received considerable attention. In this work, we fabricated an AA3003/AA1060 layered aluminum and introduced heterogeneity by regulating recrystallization behavior via accumulative roll bonding and annealing processes. The annealing process was studied by in-situ electron backscatter diffraction (EBSD) observation. The present work shows that the recrystallization rate in the AA1060 layer is significantly higher than that in the AA3003 layer. This disparity can be attributed to the varying element composition, which generates a layered aluminum structure comprising alternating fine-grained and coarse-grained layers. Moreover, the influence of layer interface on the recrystallization behavior of the AA1060 layer was investigated. The result shows that high energy storage near the interface promotes recrystallization nucleation and grain growth. This study reveals the formation mechanism of layered heterogeneous metallic materials, which can help the design and preparation of high-performance heterogeneous metallic materials.

Oxidation Behavior and Outward Diffusion of Al Along Oxide Grain Boundaries of FeCrAl Alloys Overdoped with Zr and Hf

AbstractThe formation of the α-Al2O3 scale on reactive element (RE)-doped FeCrAl alloys is commonly believed to be primarily caused by inward oxygen transport along grain boundaries. However, this study suggests that metal ion outward diffusion also plays a role in the development of the oxide scales and their microstructural characteristics. The study examines the oxidation behavior and grain boundary outward diffusion of iron-chromium alloys containing ~ 10 at% aluminum and ~ 22 at% chromium, doped with an over-critical concentration of REs, i.e., Zr and Hf. All samples were investigated after thermal exposure at 1100 °C by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT). As a result of the overdoping, a considerable increase in oxide growth, an increase in the depth of internal oxidation, and RE-oxide formation near and at oxide grain boundaries (GBs) were observed as a consequence of increased inward and outward diffusion. The effect of overdoping manifests itself differently depending on the RE type and amount due to different solubility, ionic size, and electronic structure of alumina. The sample with Zr retained the adhesion of alumina to the alloy after the first and second thermal exposure, while Hf overdoping resulted in severe spallation after the second thermal exposure.

Additive manufacturing of complex structures and flow channels using wire-arc thermal spray

The development of a cost-effective additive manufacturing method for millimeter-scale metal structures is essential for the fabrication of novel, high-efficiency heat exchangers and heat sinks. The millimeter-scale fluid channels produced by these structures provide a large surface area to promote heat transfer while minimizing system volume and mass. Traditional additive manufacturing methods are limited by their high cost, high energy consumption, and long processing times. This study presents an efficient additive manufacturing method by using wire-arc thermal spray through a polymer mask. Aluminum and copper structures with arbitrary shapes and a height of 1.3 mm were deposited on a plate 74 mm × 51 mm in size in 30 min and 15 min, respectively. Masks were fabricated by 3D-printing with a high-temperature photopolymer resin. All fabricated structures exhibited a dense center region, a porous side wall region, and a porous satellite particle region between deposited structures. The development of the deposited structures throughout the process is investigated for aluminum (having a low density, surface tension, and melting temperature) and copper (having a high density, surface tension, and melting temperature). The influence of the distance between the mask and the substrate on structure geometry and porosity is studied. The fabrication steps of a liquid-cooled mini-channel heat sink containing an enclosed flow channel are demonstrated using the proposed additive manufacturing method. The results suggest that using wire-arc thermal spray through a polymer mask can be used as a cost-efficient method to additively manufacture metal structures on the millimeter scale.

Mechanical properties and micro characterization of coal slime water-based cementitious material-gangue filling: A novel method for co-treatment of mining waste

With the improvement of coal mining depth and mechanization level, the difficulty of coal slime water (CSW) disposal increases. The preparation of cementitious materials with CSW can not only solve the disposal problems, but improve the structural stability and mechanical properties of coal gangue (CG) piles as a cementitious material. At the same time, it realizes the cooperative resource utilization of mining waste and reduces environmental pollution. In this study, it is proposed to prepare high water contained coal slime water-based cementitious material (CSCA) with 6 types of additives to bond CG particles and improve mechanical properties. Study on property of compressive strength CSCA-CG (CGSB) show that five factors (f1-f5) influence the property order as: calcination temperature of CG (f5) > CG particle size distribution (f4) > ratio of CG and CSCA (f1) > additives content (f2) > volume of water glass (f3). The optimal experimental parameters were that f5 calcined at 800 °C for 30 min, f4 with 0 ∼ 0.18 mm (6 %), 0.18 ∼ 2 mm (24 %) and 2 ∼ 5 mm (70 %), f1 of 4:1, f2 of 5 %, and f3 with 3 ml. The mechanical experiments shows that the uniaxial compressive strength of aged 28 d could reach 1.48 MPa, and results of variable angle shear test at 50°showed that principal stress of 1.26 MPa and shear strength of 1.45 MPa were obtained. The CGSB prepared with by non-calcined CG has better plastic deformation ability and less strength loss after peaking. The reason for improved uniaxial compressive mechanical properties of CGSB with calcined CG are suggested as following: densifying the structure of CG, strengthening the hydration process of cementitious materials, and promoting the growth of calcium alumina structure. Therefore, it is suggested that this study provides new ideas for CSW-CG co-disposal and provides a reference solution for mechanical property optimization.

Role of support bio-templating in Ni/Al2O3 catalysts for hydrogen production via dry reforming of methane

Bio-templating, a synthetic approach inspired by nature, is an emerging area in material engineering. In this study, waste leaves of Sycamore were utilized as a bio-template for producing alumina support to prepare catalyst. The performance of Ni and Ce impregnated on bio-templated alumina support was investigated in dry reforming of methane for the first time. The effect of process and catalytic variables were examined in detail. The results showed that impregnation of 20% Ni and 3% Ce on the bio-templated alumina led to improved Ni dispersion and achieving the maximum CH4 conversion of 88.7%, CO2 conversion of 78.5%, and H2 yield of 85.3%, compared to 84.4%, 75.6% and 83.4% for the non-templated catalyst at 700 °C, respectively. Detailed characterization of the catalysts revealed that the enhanced performance in the bio-templated catalyst could be attributed to smaller Ni particles, superior dispersion of Ni on the support, the mesoporous structure of alumina, and the larger surface area of support. Furthermore, analysis of the used catalyst showed reduced coke formation on the catalyst surface and high stability of bio-templated catalysts, highlighting the main advantage of bio-templated catalysts over non-templated ones. The findings presented in this study contribute to the potential future applications of bio-templating materials and shed light on the rational design of bio-templating materials.

A combined effect of the structure of aluminium – silicon and aluminium – titanium master alloys on the structure and properties of Al – Si – Mg alloy

A combined effect of the structure of aluminium – silicon and aluminium – titanium master alloys on the structure and properties of Al – Si – Mg alloy

Investigation and optimization of energy absorption of squared-section thin-walled structure under lateral dynamic loading

In many engineering structures, especially transportation systems, energy-absorbing structures are used to prevent or reduce collision damage. Thin wall structures are an important category of these systems. The present study investigates the level of energy absorption and crushing behavior of thin-walled aluminum structures with multi-cell square sections under lateral impact loading. The material used to produce the samples is AL-6061. The samples were subjected to lateral impact loading by combining different wall thicknesses to determine the optimal cross-section geometry. For this purpose, numerical simulation was conducted using Abaqus software. Firstly, the simulation method was validated, and after validation, different combinations of multi-cell square sections with varying wall thicknesses were designed using the Design of Experiment (DOE) method. Additionally, due to the assumption of thin walls in the structures, the wall thicknesses of the samples were considered in the range of 1 to 3 mm. The mass and initial velocity of the impactor are 35.7 kg and 6.26 m/s, respectively. The results showed that the wall thickness of the structures and their different combinations can have a significant effect on their energy absorption parameters. These effects are generally nonlinear, with severe effects observed in some cases. Finally, through the analysis of the energy absorption process of the structures and the use of the response surface method (RSM), an optimal sample was designed and simulated. The results indicate an increase of approximately 246% in the specific energy absorption of the optimal sample compared to the sample with the same wall thickness.

Evaluation of Intergranular Corrosion in 7050-T7451 Aluminum Structures Influenced by Temperature and Contact with Cutting Fluid

This research presents a practical approach to the development of the intergranular corrosion in 7050 - T7451 aluminum alloy used in the construction of manifold components of an aircraft structure. At first, it is presented what type of corrosion this is and how it develops in the crystalline structure, noting which variables contribute to the aggravation of this problem and their impacts on aviation, since this is the beginning of a number of structural defects included fatigue, which stands out even more because of the circumstances that are presented. The performance of the tests in laboratory seeks to evaluate the reactions of the material when exposed to cutting fluid and thermal variations for a long period; the development of corrosion in the microstructure has been simulated, and with this the loss of mechanical resistance of the samples could be evaluated. The results obtained indicate that the cutting fluid even slowly, showed effects in the propagation of corrosion in the alloy of aluminum studied and reduced your mechanical strength.

Fatigue Analysis of Welded Joints Using a Thin-Walled Al/Fe Explosive Welded Transition Joints.

The study presents an analysis of S355J2+N steel and AA5083 aluminum alloy welded structural joints using explosion welded transition joints of reduced thickness. The transition joint thickness reduction significantly hinders the welding of the joints due to the risk of damage to the Al/steel interface as a result of the high temperatures during welding. In the previous article, the strength of the transition joint was analyzed but ship structures, apart from static loads, are subjected to many different cyclical loads. Welded structural joints are analyzed to determine the welding influence on the fatigue life and fracture type of the transition joints. The results of the fatigue tests show that the fatigue damage in the specimens occurs in the aluminum welded joint, and not in the explosively welded joint. The damage obtained was characteristic of cruciform welded joint specimens and both types of root and toe damage occurred. Based on the obtained results, fatigue curves for the joint were determined and compared to the fatigue curves for the AA5083 base material. The experimental fatigue curve was also compared with the design curve for welded aluminum structures from Eurocode. The conducted analysis showed the possibility of using Al/steel explosion welded transition joints of reduced thickness to transfer cyclical loads.

Fabrication of Au‐Decorated Al Nanoconcavities Platform for Augmented SERS

AbstractA robust and competitive technology to synthesize arranged high‐density gold nanoparticles on highly uniform Al nanoconcavities substrates is presented. The nanoparticles are formed through sputtering and thermal annealing treatment on Al templates, which are synthesized through particular removal of nanoporous anodic alumina structure with controlled anodization conditions and with phosphoric acid as electrolyte. This scalable fabrication mechanism regulates the particle size, arrangement, shape and interparticle separation across large surface areas, which empowers the optimization of their surface enhanced Raman scattering (SERS) activities. 4‐mercaptopyridine is selected as a probe molecule. Analysis reveals that Au‐decorated Al nanoconcavities substrates are highly competitive for the enhancement of Raman signals and could be employed as self‐sustaining nanosensors. By using these templates, a concentration as low as 10−7 M of 4‐mercaptopyridine is easily detected. Finally, the calculated EF factor of 1.1 × 107 confirms the suitability for effective and sensitive SERS detection of the developed substrates.