Advanced Engineering Materials最新文献

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.

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.

This article introduces a novel method to enhance the damping performance of triply periodic minimal surface (TPMS) structures by integrating metamaterials with constrained layer damping (CLD) applications. This objective is accomplished by combining a viscoelastic silicone polymer layer with a primitive TPMS structure fabricated through laser powder bed fusion using aluminum alloy powder. Finite-element method (FEM) models using voxel elements, due to their high accuracy and computational efficiency, are developed to analyze the damping behavior of the TPMS-based CLD structure across various frequencies. Experimental modal test results validate the FEM model with high accuracy. Two distinct damping characterization methods, both time-domain and frequency-based, are employed to quantify the damping performance. The results reveal a fivefold improvement in damping performance in the time domain compared to the metal TPMS structure. In the frequency domain, the structure demonstrates 76% lower cumulative vibration compared to the metallic reference using the integral of frequency response method.

Direct-methanol fuel cells (DMFCs) have become a hot research topic in the energy field due to their excellent energy conversion efficiency and environmental sustainability. Optimization of catalyst preparation strategy is the key to enhance the performance of DMFC. In this study, melt quenching is employed to synthesize Al–Pd–Ag precursor alloy ribbons, and self-supported nanoporous Pd–Ag catalysts with high activity are successfully prepared by a precisely controlled dealloying process. The catalysts are characterized microstructurally and tested electrochemically, and their performance is compared with samples without sodium terephthalate addition and with commercial Pt/C and Pd/C catalysts. In the results, it is shown that the maximum peak current density of methanol electrocatalytic oxidation is significantly enhanced to 1451.16 mA mg⁻¹ with the addition of 15 mM sodium terephthalate, which is about 6.6 times higher than that of the unadded samples, and the catalytic performance is improved by a factor of 7.7 and 12.0, respectively, compared to those of commercial Pt/C and Pd/C. This remarkable performance enhancement is attributed to the innovative dealloying method, which not only refines the catalyst structure but also achieves a significant increase in catalytic performance through the assistance of active self-supporting nanoporous structures and interfacial synergistic effects between palladium and silver.

Flexible paper-based electronics are trending currently for its biodegradability, light weight, and compactness. A flexible film with 10, 20, 30 wt% of BCST-CNF multiferroic filler is systematically investigated by initially simulating electromagnetic interference (EMI) shielding parameters using CST Studio Suite Software. Nicolson–Ross wire algorithm is used to estimate the EM parameters of PVDF/(Ba_0.945Ca_0.055Sn_0.07Ti_0.93)O₃–Co_0.9Ni_0.1Fe₂O₄)(BCST-CNF) (PBC) films. By adaption of PBC on mulberry paper, the shielding effect of the screen-printed EMI shielding material with 30 wt% of multiferroic filler reveals over 65.24 dB, which is the highest value of shielding effect for X-band compared to other tested films. Moreover, it shows enhanced microwave absorption of 63.48 dB. This study opens up an effective avenue for designing strong microwave absorption materials to satisfy the increasingly demanding requirements of advanced and integrated electronics.

Surface icing issues have a significant impact on industries such as aviation, transportation, and construction. Superhydrophobic surfaces can delay ice formation due to their liquid-repellent properties, but their effectiveness is not pronounced in extremely cold environments. Electric heating coatings can effectively prevent ice formation, but they have limitations in environments with insufficient electrical energy supply. The anti-icing effect of photothermal superhydrophobic coatings is restricted under conditions of insufficient sunlight. To enhance the ice-preventing performance of superhydrophobic coatings in extremely cold environments, this article employs a template spraying method to prepare a carbon black and graphene composite coating that provides superhydrophobic passive anti-icing and photo/electrothermal active deicing capabilities. The micro-nanostructured superhydrophobic surface exhibits exceptional ice-preventing performance. The excellent electrothermal and photothermal performance, along with high energy conversion efficiency, significantly enhance the coating's deicing efficiency. Under the synergistic effect of solar and electrical energy, the ice layer is completely melted within just 135 s. Furthermore, the material possesses excellent durability (resistance to mechanical wear, acid and alkali corrosion, and UV aging), as well as thermal stability. This research provides new avenues and insights for the development of advanced anti-icing and deicing materials for applications in aviation, transportation, construction, and other fields.