Aluminum Structures Research Articles

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.

The TU Wien Turbulent Water Channel: Flow control loop and three-dimensional reconstruction of anisotropic particle dynamics.

A horizontal water channel facility was built to study particle dynamics in a turbulent flow. The channel is sufficiently long to produce fully developed turbulence at the test section, and the width-to-height ratio is sufficiently large to avoid the sidewall effect for a large proportion of the cross-section. The system was designed to study the dynamics of complex-shaped particles in wall-bounded turbulence, the characteristics of which can be finely controlled. A maximum bulk velocity of up to 0.8ms-1 can be achieved, corresponding to a bulk Reynolds number of up to 7 × 104 (shear Reynolds number ≈1580), and flow parameters can be controlled within ±0.1%. The transparent channel design and aluminum structures allow easy optical access, which enables multiple laser and camera arrangements. With the current optical setup, a measurement volume of up to 54 × 14 × 54 mm3 can be imaged and reconstructed with six cameras from the top, bottom, and sides of the channel. Finally, the in-house developed reconstruction and tracking procedure allows us to measure the full motion of complex objects (i.e., shape reconstruction, translational, and rotational motions), and in this instance, it is applied to the case of microscopic, non-isotropic polyamide fibers.

Out-of-plane static loading performance of lightweight aluminum/composite FML structures for retrofitting applications: Effectiveness of bonded, bolted and hybrid bonded/bolted joining techniques under hydrothermal aging environment

This study evaluates the mechanical response for different flexural loading direction scenarios of the fiber metal laminates (FMLs), an aluminum structure retrofitted with basalt fiber-reinforced epoxy-based composites for aircraft applications. The static bending load-carrying effectiveness under hydrothermal aging of FMLs joining with bolted, bonded, and hybrid bolted/bonded (HBB) techniques were investigated, and damage formations were discussed through post-fracture morphological analyses. Besides, the adhesive was modified by adding halloysite nanotubes (HNTs) to increase the bond durability, especially against the aging environment. Test results showed that HBB structures generally provided superior aging durability compared to other connection types. It was also concluded that the basalt/aluminum FMLs exhibit a more effective load-carrying performance when the aluminum component is positioned under the neutral axis, preventing abrupt load drops. For untreated, wet, and dried conditions, the load-carrying capacities of HBB (nano-adhesive and four bolts) specimens exhibited enhanced load-bearing performance by 24–34%, 25–42%, and 29–30% compared to neat-adhesively bonded samples. Moreover, HBB structures improved performance for the same conditions by 114–141%, 127–155%, and 102–146%, respectively, compared to only-bolted (two bolts) specimens. This study provides insights into the potential use of basalt fiber-reinforced polymer composites BFRPCs in retrofitting aluminum for aerospace applications.

Hard-templated macroporous alumina with thick mesoporous walls: The key factors of pore formation

This paper focuses on the key factors contributing to pore formation in hard-templated macroporous alumina. Special attention is paid to the formation of a connected pore structure. Two series of samples were prepared, each with different content of the polymeric template. The pore structure of alumina was designed using polystyrene and acrylic copolymers as hard templates. Alumina differed in crystallite morphology (round-like and rod-like) and pore structure (bottleneck-like and slit-like). The templates differed in particle size (100 and 250 nm) and physical state (powder and suspension). All the samples were characterized by N2 adsorption, Hg porosimetry, XRD, and SEM. The data obtained indicate that a hard template made of polymeric particles has the following functions: fixing the pore size and shape, sintering small pores of the material, and creating additional channels to connect macropores. Regardless of the type of polymeric template and Al2O3 precursor, a connected pore system can be formed by adding more than 20 wt% of the template.

Interface catalytic reduction of alumina by nickle for the aluminum nanowire growth: Dynamics observed by in situ TEM

Metal nanowires show promise in a broad range of applications and can be fabricated via a number of methods, such as vapor–liquid–solid process and template-based electrodeposition. However, the synthesis of Al nanowires (NWs) is still challenging from the stable alumina substrate. In this work, the Ni-catalyzed fabrication of Al NWs has been realized using various Al2O3 substrates. The growth dynamics of Al NWs on Ni/Al2O3 was studied using in situ transmission electron microscopy (TEM). The effect of alumina structures, compositions, and growth temperature were investigated. The growth of Al NWs correlates with the Na addition to the alumina support. Since no eutectic mixture of nickel aluminide was formed, a mechanism of Ni-catalyzed reduction of Al2O3 for Al NWs growth has been proposed instead of the vapor–liquid–solid mechanism. The key insights reported here are not restricted to Ni-catalyzed Al NWs growth but can be extended to understanding the dynamic change and catalytic performance of Ni/Al2O3 under working conditions.

Domain structure and structural transformation of melt alumina under compression: insight from visualization method and molecular dynamic simulation

Domain structure and structural transformation of melt alumina under compression: insight from visualization method and molecular dynamic simulation

Anion-Dependent Structure, Dehydration, and Hydroxide Ion Conductivity of Magnesium Aluminum Layered Double Hydroxides

Anion-Dependent Structure, Dehydration, and Hydroxide Ion Conductivity of Magnesium Aluminum Layered Double Hydroxides

Effect of interlayer particles on the bonding improvement of aluminum laminated composites

Aluminum-based composites (AMMCs) have become a popular topic in industrial progress. The aluminum (Al) structure is such that, while it is very light, it also has significant strength. This capability has increased the use of Al in various industries, especially the aerospace and marine industries, even more. Other properties of Al include the favorable plasticity of these structures. It is worth mentioning that many methods can be used to produce Al metal matrix composite (AMMC). One of these methods is Accumulated Press Bonding (APB). APB is one of the most powerful processes as a solid welding method for making MMCs. This method can be called a complex technology that has many advantages. One of the main advantages of this method is that it has a high potential to refine the nanostructures that make up a composite, making it possible to design, produce and refine composites consisting of several layers. In addition to advantages, this process also has disadvantages. Actually, in this process, the bond strength (BS) is weak. This study uses Sn particles to improve the BS of Al laminates as filler metal. So, AA1060 bars with different wt% of Sn particles (interlayer filler material) were manufactured at various pressing temperatures (Temp’s) and APB steps. The peeling test was used to evaluate the bonding strength. It was found that the pressing Temp increased APB number of steps and Sn wt%, popular bonds with upper strength were shaped. Also, to illustrate the peeling surface of AA1060/Sn samples, scanning electron microscope (SEM) was used.

Electronic structure of boron and aluminum δ-doped layers in silicon

Recent work on atomic-precision dopant incorporation technologies has led to the creation of both boron and aluminum δ-doped layers in silicon with densities above the solid solubility limit. We use density functional theory to predict the band structure and effective mass values of such δ layers, first modeling them as ordered supercells. Structural relaxation is found to have a significant impact on the impurity band energies and effective masses of the boron layers, but not the aluminum layers. However, disorder in the δ layers is found to lead to a significant flattening of the bands in both cases. We calculate the local density of states and doping potential for these δ-doped layers, demonstrating that their influence is highly localized with spatial extents at most 4 nm. We conclude that acceptor δ-doped layers exhibit different electronic structure features dependent on both the dopant atom and spatial ordering. This suggests prospects for controlling the electronic properties of these layers if the local details of the incorporation chemistry can be fine-tuned.

Quasi-static and fatigue analyses of aluminium structures repaired by CFRP patch bonding

In this work, quasi-static and fatigue analyses of the three most common adhesive repair geometries were performed considering composite patches and aluminium as parent material. Experimental three-point bending tests were accomplished on single-strap, double-strap and scarf repairs in order to obtain the load–displacement curves for quasi-static analysis, and compliance versus number of cycles curves for the fatigue studies. The main goals are to identify the static strength and fatigue lives for each type of adhesive repair. In addition, progressive damage analyses that rely on two cohesive zone models appropriate for quasi-static and high-cycle fatigue under mixed-mode I + II loading were performed. These models allow the simulation of damage initiation and propagation in the repairs under quasi-static and fatigue loading. It was found that both models are able to replicate the fundamental trends observed experimentally, thus establishing their effectiveness.

Study of the Effects of Adhesive Damage and Plasticity on the Repair of Cracked Aluminum Structures

Study of the Effects of Adhesive Damage and Plasticity on the Repair of Cracked Aluminum Structures

Effect of coordination structure of aluminum on its activation from minerals and Oxisols during their acidification

The types and contents of phyllosilicate minerals in soils play an important role in soil acidification, as soil acid buffering capacity varies with the composition of the phyllosilicate minerals. In addition to aluminum-oxygen (Al-O) octahedrons, a certain number of Al-O tetrahedrons exist in phyllosilicate minerals due to the isomorphic substitution of silicon ion (Si4+) by aluminum ion (Al3+) in Si-O tetrahedrons of minerals. However, the effect of the two coordination structures of Al on the release of Al during mineral acidification has not yet been investigated. Therefore, the differences in Al activation in phyllosilicate minerals and soils with different Al coordination structures were investigated through constant-pH experiments and 27Al magic-angle spinning nuclear magnetic resonance (MAS-NMR) measurements. The results of 27Al MAS-NMR spectra showed that kaolinite contained Al-O octahedrons, phlogopite and illite contained Al-O tetrahedrons, and vermiculite composite contained both octahedral and tetrahedral Al. At pH < 5.1, the content of Al released from minerals during simulated acidification followed the order: illite > vermiculite composite > phlogopite > kaolinite, which was consistent with the orders of cation exchange capacity and content of tetrahedral Al of the minerals. According to the rate constants, the Al release rates were in the order of phlogopite > illite > vermiculite composite > kaolinite at pH 4.8. Except for phlogopite, the Al release rates in these minerals increased with decreasing suspension pH. Therefore, the Al release contents and rates were greater in phlogopite, illite, and vermiculite composite containing Al-O tetrahedrons than in kaolinite containing only Al-O octahedrons. Two Oxisols derived from basalt with different ages were selected for similar studies. The 27Al MAS-NMR spectra of the Oxisols showed that the 0.01-million-year (Ma) Oxisol contained both octahedral and tetrahedral Al, while the 1.33-Ma Oxisol contained only Al-O octahedrons. The contents of both exchangeable and soluble Al released from the 0.01-Ma Oxisol were greater than those from the 1.33-Ma Oxisol when the two soils were acidified to the same pH. The results from minerals and soils confirmed that Al was more readily released into solution and exchangeable sites as soluble and exchangeable Al in Al-O tetrahedrons than in Al-O octahedrons during the acidification of soils and minerals. The findings of this study will provide useful references for investigating the mechanisms of solid phase Al release and for mitigating soil acidification and inhibiting Al activation in different soil types.

Optimum design of pin-jointed aluminum structures to AA-ASD using three Meta-heuristic algorithms

The main motivation for the current study is to investigate the weight advantage of the aluminum material on pin-jointed (truss) structures. For this purpose, optimization algorithms that find the most suitable structural designs with aluminum and steel materials have been developed. The criterion for finding optimum designs is to minimize the weight of the structure and met the design constraints. The constraint functions are derived according to the “American Institute of Steel Structures – Allowable Stress Design” (AISC-ASD) and “Aluminum Association - Allowable Stress Design” (AA-ASD) design codes. To increase the reliability of the obtained results, three robust methods named the Artificial Bee Colony (ABC), Biogeography Based Optimization (BBO), and Brainstorming Optimization (BSO) algorithms are utilized for the proposed optimization problem. Four real-scale pin-jointed structures are used to research the weight advantage of aluminum structures. Three of these structures are real-scale truss structures that were previously optimized as made of steel elements by other metaheuristics. The last pin-jointed structure is the real case project which is modeled and optimized for the first time in this study. According to the obtained results, significant optimal design differences are determined between the construction of the tackled pin-jointed structures with aluminum or steel structural elements. Considering other advantages such as transportation and maintenance, using aluminum material in pin-jointed structures is recommended.

Aluminium Bridges under Fire Conditions: Structural Behaviour

Due to a number of advantages, aluminium is used in the attachment units of mullion and transom systems for decorative panels and translucent fillings, as well as for bridge structures. Despite its advantages, aluminium has a low melting point and does not have fire resistance performances required by regulatory documents under fire conditions. Therefore, this article is aimed at studying the behaviour of aluminium structures under high temperatures. To achieve this objective, we have analysed the aluminium structures most commonly used in construction—the attachment units of mullion and transom systems, with different protections against fire, columns and orthotropic decks used in bridge construction. In order to assess the behaviour of selected structures under fire conditions, we have developed methods for studying temperature distributions in structures in detail. Using the developed methods, tests have been carried out. Based on the received experimental data, we analysed the behaviour of aluminium structures in fire conditions and developed measures to increase the fire resistance of aluminium structures. Such measures include using hollow profiles to ensure air exchange with the cold sections of the structure, applying dedicated cooling agents to cool the structure and removing heat to the atmosphere and thermal barriers so as to protect aluminium structures. We found that fire resistance measures enhance the fire resistance of aluminium attachment units of mullion and transom systems by 1.5 times. The use of hollow air-permeable profiles and cooling agents in orthotropic decks increases fire resistance by 3 times by removing heat from the structures. The fire resistance rating of hollow profile aluminium columns is 1.5 times higher than that of structures without air-permeable profiles. The obtained results can be used as the most effective basis for the design of aluminium structures. The principles of increasing fire resistance given in this article are applicable to other types of structures, and can also be used with other methods of fire protection. Increasing the fire resistance of aluminium structures enables the expansion of the scope of their applications.

Diffusion and Interdiffusion Study at Al- and O-Terminated Al2O3/AlSi12 Interface Using Molecular Dynamics Simulations.

The equivalent characteristics of the materials' interfaces are known to impact the overall mechanical properties of ceramic-metal composites significantly. One technological method that has been suggested is raising the temperature of the liquid metal to improve the weak wettability of ceramic particles with liquid metals. Therefore, as the first step, it is necessary to produce the diffusion zone at the interface by heating the system and maintaining it at a preset temperature to develop the cohesive zone model of the interface using mode I and mode II fracture tests. This study uses the molecular dynamics method to study the interdiffusion at the interface of α-Al2O3/AlSi12. The hexagonal crystal structure of aluminum oxide with the Al- and O-terminated interfaces with AlSi12 are considered. A single diffusion couple is used for each system to determine the average main and cross ternary interdiffusion coefficients. In addition, the effect of temperature and the termination type on the interdiffusion coefficients is examined. The results demonstrate that the thickness of the interdiffusion zone is proportional to the annealing temperature and time, and Al- and O-terminated interfaces exhibit similar interdiffusion properties.

Single source with series modifications: New method for preparing modified clay to control harmful algae blooms

Modified clay (MC) is an effective and eco-friendly material that is widely used for controlling harmful algae blooms (HABs). In this study, a new method—single source with series modifications (SSSM)—was optimized for preparing a high-quality MC, and aluminum-rich clay (kaolin) was activated with a multistep treatment that included calcination (Cal), acid etching with alkali neutralization (Al–An), and raw clay supplementation and aging (RSA). The results showed that the removal efficiency of Prorocentrum donghaiense by the SSSM–MC exceeded 85%; Cal, Al–An, and RSA were indispensable processing steps for preparing the best MC with the SSSM method. The changes occurring in the mineral structure and chemical composition of kaolin treated by the different steps were characterized by FT-IR, XRD, 27Al-NMR and Al-Ferron. Surface dehydroxylation and disruption of the kaolin lattice after calcination significantly changed the aluminum structure from AlVI to AlV and AlIV. The relatively reactive AlV was readily released from the kaolin lattice with acid etching, and it subsequently reacted with external OH– to generate different polyhydroxyaluminum species because alkali was added during the Al–An step. The acidity of the above complex was further decreased by RSA, greatly increasing the yield of SSSM–MC while assuring the quality.

Facilely adjusting acidity features of zeolites by steaming treatment for enhanced methanol conversion to aromatics: A mechanism study

In this contribution, the effects of the steaming treatment on the acidity and aluminum structure of ZSM-5 were systematically investigated by using different types of zeolite catalysts. The relationships between the acid properties and the catalytic performance of the methanol-to-aromatics (MTA) reaction were also elucidated. The results revealed that different kinds of acid sites showed varied stability during the steaming treatment. Especially for Brønsted acid sites (BAS), the reduction of the acid site was highly related to the stability of different distributed framework Al sites (Alsingle > Alpairs) and the existence of non-framework species (“neutralization” by the EFAL and ZnO). Additionally, the presence of the extra-framework aluminum (EFAl) and metal compensation ions could enhance the stability of the zeolite framework Si-O(H)-Al. Besides, it was found that the reduction degree in the content of the Zn-LAS (LAS = Lewis acid sites) was less than the Al-LAS. The effects of steaming treatment on acid properties over zeolites with different particle sizes were also explored. Furthermore, the catalytic performance for the MTA reaction showed that the stability of the ZSM-5 catalyst was significantly enhanced after the steaming treatment. Moreover, the reduction in the proportion of the Alpairs sites may inhibit the hydrogen-transfer aromatization process of alkenes, while the increase of the Alsingle species enhanced the cracking process of higher olefins, leading to the reduction of aromatics selectivity and the increase of light olefins selectivity, respectively.

Young’s Modulus-Independent Determination of Fibre Parameters for Rayleigh-Based Optical Frequency Domain Reflectometry from Cryogenic Temperatures up to 353 K

The magnetic spectrometer AMS-100, which includes a superconducting coil, is designed to measure cosmic rays and detect cosmic antimatter in space. This extreme environment requires a suitable sensing solution to monitor critical changes in the structure such as the beginning of a quench in the superconducting coil. Rayleigh-scattering-based distributed optical fibre sensors (DOFS) fulfil the high requirements for these extreme conditions but require precise calibration of the temperature and strain coefficients of the optical fibre. Therefore, the fibre-dependent strain and temperature coefficients KT and Kϵ for the temperature range from 77 K to 353 K were investigated in this study. The fibre was integrated into an aluminium tensile test sample with well-calibrated strain gauges to determine the fibre’s Kϵ independently of its Young’s modulus. Simulations were used to validate that the strain caused by changes in temperature or mechanical conditions was the same in the optical fibre as in the aluminium test sample. The results indicated a linear temperature dependence of Kϵ and a non-linear temperature dependence of KT. With the parameters presented in this work, it was possible to accurately determine the strain or temperature of an aluminium structure over the entire temperature range from 77 K to 353 K using the DOFS.

Enhancing Fe content tolerance in A356 alloys for achieving low carbon footprint aluminum structure castings

Low carbon footprint aluminum structure castings are the mainstream development direction of aluminum alloys in the future. Enhancing the Fe content tolerance upper limit in casting aluminum alloys is considered an effective way to promote the application of recycled aluminum production. In this work, it was found that with the Ce and TiCN NPs (nanoparticles) addition simultaneously to A356 alloys, the acicular Fe-rich phases (β-Al5FeSi) which damages the properties can be changed into beneficial phases (core-shell heterostructures) for the alloy, and hence the mechanical properties of A356 alloys can be improved. The TiCN nanoparticles and rare element Ce play crucial roles in the formation of core-shell heterostructures. The formation mechanism of core-shell heterostructure was also systematically researched from the perspective of thermodynamics and kinetics. This study provides a simple and feasible strategy to eliminate the harmful effects of Fe impurity and contributes to the industrialization of low carbon footprint aluminum structure castings.

Experimental Evaluation of Curved Aluminum Structures Subjected to Underwater Explosions

Experimental Evaluation of Curved Aluminum Structures Subjected to Underwater Explosions