Advanced Engineering Materials最新文献

The difficult determination of morphological properties in metal foams stands behind the reasons why metal foams are not widely used in industry, since quality control of the batches produced is limited to destructive methods. To approach this challenge, a new method of analysis of morphological properties based on 2D X-Ray radiograms and the employment of a new Convolutional Neural Network architecture is proposed. The training of this model is based on a combined approach of simulating simplified foams as pretraining data and the acquisition of real experimental data, extracted from X-Ray computer tomographies. The network is trained successfully with 41 foams to obtain predictions for cell size distribution between 0.3 and 5 mm, as well as sphericities in ranges from 0.4 to 1. In addition, tests are carried out to get an insight into the robustness of the model when confronted with similar data that are not included in the training process. It is found that the effectiveness of the neural network increases with a larger number of cells in the observed volume where above 500 cells per volume 92.5% of sphericity predictions and 99.4% of cell size predictions passed the Kolmogorov-Smirnov test.

Enhancing carbon dioxide (CO₂) detection is crucial for improving indoor air quality and environmental surveillance. Traditional CO₂ sensors face drawbacks like high costs, large sizes, environmental impact, and reliance on external power, limiting their practicality for continuous indoor monitoring. In this research, an innovative indoor CO₂-sensing system using a self-powered bio-solar cell (BSC) platform is introduced. Utilizing cyanobacteria as a sensitive biocatalyst and sustainable power source, the system offers a cost-effective, eco-friendly, and maintenance-free alternative to conventional sensors. It operates by monitoring electron-transfer processes in cyanobacteria during photosynthesis, converting CO₂ and water into oxygen and chemical energy, enabling accurate CO₂ level monitoring. The system responds to CO₂ fluctuations and issues alerts when levels are outside the recommended range of 500–1000 ppm for human health and productivity. A self-sustaining configuration of eight BSCs—one for sensing and others for power generation—ensures continuous operation without external power. An integrated energy-harvesting board efficiently manages power distribution to a microcontroller and display system for real-time data visualization, with the array producing up to 400 μW. Additionally, a machine-learning model interprets BSC outputs to accurately quantify CO₂ levels, enhancing the sensor's adaptive performance.

Pneumatic manipulation has the advantages of low cost, lightweight design, fast response, and ease of integration. However, its application in the field of phononic crystals remains limited. Inspired by pneumatic soft robots, this article proposes a pneumatic soft phononic crystal arranged in a square lattice, incorporating four pneumatic actuators within the scatterer. By manipulating air pressure, the bandgap can be effectively opened and closed. The finite element analysis is employed to examine the deformation and bandgaps of the pneumatic soft phononic crystal under varying air pressures. Moreover, the effect of the scatterer's rotation angle on the bandgap evolution in the phononic crystal is parametrically investigated. The results show that varying both the volume and the rotation angle of the scatterer can achieve bandgap opening, closing, and tuning. The proposed phononic crystal presents obvious practical applications and provides important insights for the design of soft-tunable acoustic devices.

Electron cyclotron resonance-chemical vapor carbon deposition technique was altered via incorporation of nitrogen gas in the methane (CH₄)-based plasma, thermal annealing of the substrates, and Arduino-controlled sample rotating mechanism to bombard the contact surface of the piston ring samples. By placing the substrates very close to the plasma gun, various carbon-based structures including graphene oxide, nanodiamond, and reduced graphene oxide were successfully deposited. The formed structures were characterized via scanning electron microscopy, atomic force microscopy, Raman spectroscopy, X-ray diffraction, and energy dispersive X-ray. Related tribological analyses such as surface hardness-roughness, coefficient of friction (COF), and wear rate were also carried out on the coated surfaces. The morphology and chemical composition of the worn surfaces were observed via SEM and EDX. The coated samples were installed in a small spark-ignition engine to determine the effect of coating on brake power (P_e), specific energy consumption (β), carbon monoxide (CO), and unburned hydrocarbon (UHC) emissions. Very promising results of 14% increase in surface hardness, 11% reduction in β, 15% enhancement in P_e, 50% decrease in COF, 12.5% and 9% improvements in CO, and UHC emissions were obtained.

The objective of the current study is to produce metal matrix composites (MMCs) using ultrasonic-assisted stir casting and Al6061 alloy reinforced with silicon carbide (SiC) microparticle reinforcement in weight percentages of 0, 2, 4, and 6. The microstructural alterations of Al6061–SiC composites are investigated using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDAX). By adding more nucleation sites for the formation of smaller grains, SiC reinforcement of the Al6061 matrix encourages grain refining. The SiC addition significantly changes the microstructure of Al6061 composites, enhancing their mechanical qualities. In addition to increasing density by 0.6%, hardness by 33%, and tensile strength by 33%. The increased SiC content dramatically decreases elongation by 42%. The strength of Al6061–SiC MMCs is predicted using several strengthening mechanism concepts as part of the continuing investigation. For Al6061–SiC composites, the strengthening contribution from thermal mismatch is more significant than that from Orowan strengthening, Hall–Petch mechanism, and load transmitting effect. Grain refinement interactions, load transmission mechanisms, and the strengthening effects of CTE differences and dislocations between matrix and reinforcement particles are studied. The composite with 6-weight percent SiC reinforcement performs better in dry sliding wear and corrosion resistance.

A significant challenge in many electrochemical systems is finding a stable, high-performing current collector material that is mechanically robust, adaptable in form factor, and free of precious metals. Titanium electrodes are robust in many of these regards but exhibit poor charge transfer performance due to self-passivation. Herein, a new materials processing paradigm based on the titanium/titanium nitride (Ti/TiN) system which allows for robust, stable, and low-resistance current collectors of arbitrary form factor is presented. Specifically, a gas-nitriding process for 3D-printed titanium electrodes that results in a 20-fold improvement of charge transfer characteristics relative to the untreated material is outlined. The ability to utilize 3D-structured current collectors with a net 40-fold improvement in performance over nonstructured electrodes is further demonstrated. This novel approach to creating electrochemical current collectors requires minimal laboratory resources and can be widely adapted for a variety of applications, including desalination, electrolysis, energy storage, and basic research. The work described herein provides both a means for accelerating research and opens the door to hierarchical tuneability for enhanced performance.

The effect of pulse current on the mechanical properties of ultrasonic welded joints of 5052-H32 aluminum alloy (Al5052-H32) plate with a thickness of 2 mm is investigated experimentally. First, ultrasonic lap welding is performed to prepare the welded joint. Then, the pulsed current with different current densities and durations is applied to the welded joint. The impact of pulsed current on the properties of the welded joints is evaluated through tensile lap shear testing, observation using a metallographic microscope, and hardness testing. In the results, it is indicated that the tensile lap shear strength, elongation, and hardness of the welded joints can be improved by applying pulsed current properly. However, excessive input of electrical energy can lead to a decrease in the mechanical properties of the welded joints. Compared to the joint without pulse current treatment, the microstructure shows significant healing of the weld seam under the action of pulsed current. The feasibility of enhancing the mechanical performance of ultrasonically welded joints through the utilization of pulsed current is highlighted by these findings.

Micron-sized powders of neat aluminum and aluminum combined with 5 wt% gallium are prepared as flakes and spherical composites by emulsion-assisted milling. Such powders are of interest as high-energy-density fuel additives to solid propellants, explosives, and pyrotechnics. Added gallium does not affect the size or shape of the prepared composites; it also does not change appreciably the oxidation kinetics of the prepared powders. All milled powders ignite readily when coated on an electrically heated filament, unlike the starting aluminum powder. Powders with added gallium ignite at slightly lower temperatures when heated rapidly. The liquid metal embrittlement effect due to added gallium might have caused a smaller microstrain in the refined, milled powders. However, it does not affect the oxidation. Instead, it is proposed that added gallium alters the natural amorphous alumina film, affecting its transition to a crystalline γ-phase during rapid heating, and thus affecting the powder ignition.

This study explored the impact of multiple reprocessing cycles on the thermomechanical properties of polystyrene (PS) and low-density polyethylene (LDPE), simulated through reprocessing with a twin-screw extruder. Additionally, it compared the thermal and mechanical properties of graphene nanoplatelets (1% w/w) reinforced polypropylene (PP-GNP) nanocomposites with PP. The materials undergo seven consecutive extrusion cycles at varying screw speeds (100 and 150 rpm) and temperatures (180 and 200 °C). Increasing the screw speed from 100 to 150 rpm raised LDPE's screw torque by about 40% at the first reprocessing cycle. Processing PS at 200 °C reduced screw torque by ≈20% compared to 180 °C at 1–5 reprocessing cycles. Both torque and power decrease for PP and PP-GNP with each reprocessing cycle. LDPE's tensile modulus decreases with more cycles at 200 °C, while PS shows no consistent variation. PP's tensile modulus and ultimate tensile strength drop by 24% and 12%, respectively, from the first to the fifth cycle, while PP-GNP exhibits no consistent variation. Differential scanning calorimetry shows no clear change in LDPE's melting point, but an increase in PP and PP-GNP's melting points up to the fifth cycle. This research provides crucial insights to advance the recycling of polymers reducing environmental impact.

In this article, a systematic investigation into the corrosion and discharge behaviors of as-rolled a represents aluminum, Z represents zinc, 9 and 1 represent their respective contents of 9% and 1% in the alloy (AZ91) magnesium alloy after electro pulsing treatment (EPT), considering rolling deformations of 0% (as-cast AZ91 magnesium alloy), 20%, 30%, and 40%, is presented. In this investigation, immersion weight loss tests, electrochemical tests, and other experimental methods are employed. In the results, it is revealed that the content of the β-Mg₁₇Al₁₂ phase gradually decreases with increasing rolling deformation after EPT. Notably, the highest content of β-Mg₁₇Al₁₂ phase and the most outstanding corrosion resistance are achieved with as-cast AZ91 magnesium alloy. Furthermore, at low current densities (5 and 10 mA cm⁻²), the 30% rolling deformation exhibits superior discharge activity, while the discharge activity of the 40% rolling deformation is most excellent at high current densities (40 and 50 mA cm⁻²). The microstructure observations support these findings, highlighting the close relationship between the corrosion resistance and discharge activity of as-rolled AZ91 magnesium alloy after EPT, and the content of the β-Mg₁₇Al₁₂ phase and the area of high-energy grain boundaries.