Search Results (1,739)

This study systematically investigates the high-velocity impact response and energy absorption characteristics of carbon fiber-reinforced plastic (CFRP)—aluminum foam (AlF) hybrid composite structures, aiming to address the growing demand for lightweight yet high-performance energy-absorbing materials in aerospace and protective engineering applications. Particular emphasis is placed on elucidating the influence of key geometric and material parameters, including the aspect ratio of the columns and the relative density of the AlF core. Experimental characterization was first performed using a split Hopkinson pressure bar (SHPB) apparatus to evaluate the dynamic compressive behavior of AlF specimens with four different relative densities (i.e., 0.163, 0.245, 0.374, and 0.437). A finite element (FE) model was then developed and rigorously validated against the experimental data, demonstrating excellent agreement in terms of deformation modes and force–displacement responses. Extensive parametric studies based on the validated FE framework revealed that the proposed CFRP-AlF composite structure achieves a balance between specific energy absorption (SEA) and peak crushing force, showing a significant improvement over conventional CFRP or AlF. The confinement effect of CFRP enables AlF to undergo progressive collapse along designated orientations, thereby endowing the CFRP-AlF composite structure with superior impact resistance. These findings provide critical insight for the design of next-generation lightweight protective structures subjected to extreme dynamic loading conditions. Full article

Alloys and metals exhibit high sensitivity to corrosion and aggressive environments. Hence, the development of protective treatments through accessible methods with a high degree of protection has become a necessity. This paper presents a method for treating the hydrophilic surface of aluminum alloys using two types of unsaturated fatty acids, thereby increasing the degree of hydrophobicity and protecting the material. The samples were cleaned by a chemical process, followed by immersion in oleic acid (C₁₈H₃₄O₂, 18:1 cis-9) and elaidic acid (C₁₈H₃₄O₂, 18:1 trans-9), and they were then treated at a temperature of 80 °C. Morphological and microstructural analyses were conducted using OM, FE-SEM, EDX, and FTIR to understand the influence of unsaturated monocarboxylic fatty acids on the alloy surfaces. The wettability capacity of the alloys was investigated by measuring the contact angle (CA). The results revealed that the cleaning step and modification treatment with fatty acids are essential steps for increasing the hydrophobic character of the surface. This study can be applied to various types of metallic substrates to enhance their corrosion resistance and long-term chemical stability in aggressive environments, making it adaptable for use in different industrial fields. Full article

Transparent conductive aluminum-doped zinc oxide (AZO) films were investigated as potential recombination layers for perovskite/silicon tandem solar cells, comparing the results of atomic layer deposition (ALD) and magnetron sputtering (MS) on vertically aligned silicon nanowire (SiNW) scaffolds. Conformality and thickness control were examined by cross-sectional SEM/TEM and profilometry, revealing fully conformal ALD coatings with tunable thicknesses (40–120 nm) versus tip-capped, semi-uniform MS films (100–120 nm). Optical transmission measurements on glass substrates showed that both 120 nm ALD and MS layers exhibit interference maxima near 450–500 nm and 72–89% transmission across 800–1200 nm; the thinnest ALD films reached up to 86% near-IR transparency. Four-point probe analysis demonstrated that ALD reduces surface resistance from 1150 Ω/□ at 40 nm to 245 Ω/□ at 120 nm, while MS layers achieved 317 Ω/□ at 120 nm. These results delineate the balance between conformality, transparency, and conductivity, providing design guidelines for AZO recombination interfaces in next-generation tandem photovoltaics. Full article

In resistance spot welding (RSW), the total electrical resistance (dynamic resistance) as the sum of bulk and contact resistance is a key variable. Both of these respective resistances influence the welding result, but the exact ratio to the total resistance of a real existing sheet is not known. Due to the high scatter in the RSW of aluminum alloys compared to steel, it is of interest to be able to explicitly determine the individual resistance components in order to gain a better understanding of the relationship between the initial state and the lower reproducibility of aluminum welding in the future. So far, only the total resistance and the bulk resistance could be determined experimentally. Due to the different sample shapes, it was not possible to consistently determine the contact resistance from the measurements. In order to realize this, a method was developed that contains the following innovations with the aid of simulation: determination of the absolute bulk resistance at room temperature (RT), determination of the absolute contact resistance at RT and determination of the ratio of bulk and contact resistance. This method makes it possible to compare the resistances of the bulk material and the surface in the initial state quantitatively. This now allows the comparison of batches regarding the surface resistance, especially for welding processes. For the aluminum sheets (EN AW-5182-O, EN AW-6014-T4) investigated, the method showed that the contact resistance dominates and the bulk resistance is less than 20%. These data can also be used to make predictions about the weldability of the alloy using artificial intelligence (AI). If experimental data are available, the method can also be applied to higher temperatures. Full article

This article focuses on the fire safety risks associated with conventional glass–aluminum façades—with a particular focus on stick and unitized curtain walling systems—providing an overview of possible fire spread mechanisms, considering the role of the curtain wall in maintaining compartmentation at the spandrel zone. First, it analyzes some of the relevant requirements of different European building regulations. Then, it provides a test evidence-based critical analysis of the gaps and loopholes in the relevant fire resistance standard for partial curtain wall configurations (EN 1364-4), where the evaluation of the propagation within the façade system is not necessarily considered in the fire-resistant spandrel zone. Finally, it presents a proposal for addressing these gaps in the form of a theoretical concept for a new test configuration and additional assessment criteria. This is followed by an initial experimental analysis of the concept. The standard testing campaign showed that temperature rise in mullions can exceed 180 °C after 30 min if limiting measures are not considered in the façade design. However, this can be only detected if framing is in the non-exposed area of the sample, being part of the evaluation surface. Meanwhile, differences are detected between the results from standard and new assessment criteria in the new configuration proposed, including a more rapid temperature rise for framing elements (207 K in a second level mullion at minute 90) than for the common non-exposed assessment surface of the sample (172 K at the same time) in cases where cavities are not protected. Accordingly, the proposed configuration successfully detected vertical temperature transfer within mullions, which can remain undetected in standard EN 1364-4 tests, highlighting the potential for fire spread even in EI120-rated assemblies. Full article

Chromium–aluminum nitride (CrAlN) coatings were deposited on polished H13 tool steel substrates using direct current (DC) magnetron sputtering. The Cr/Al composition in the target was varied by inserting either four or eight chromium (Cr) plugs into cavities machined into an aluminum (Al) plate target. Nitrogen was introduced as a reactive gas to facilitate the formation of the nitride phase. Coatings were deposited at substrate bias voltages of −30 V, −50 V, and −60 V to study the combined effects of composition and ion energy on coating properties. Compositional analysis of coatings deposited at a −50 V bias revealed Cr/Al ratios of approximately 0.8 and 1.7 for the 4- and 8-plug configurations, respectively. This increase in the Cr/Al ratio led to a 2.6-fold improvement in coating hardness. Coatings produced using the eight-Cr-plug target exhibited a nearly linear increase in hardness with increasing substrate bias voltage. Cross-sectional scanning electron microscopy revealed a uniform bilayer structure consisting of an approximately 0.5 µm metal interlayer beneath a 2–3 µm CrAlN coating. Surface morphology analysis indicated the presence of coarse microdroplets in coatings with the lower Cr/Al ratio. These microdroplets were significantly suppressed in coatings with higher Cr/Al content, especially at increased bias voltages. This suppression is likely due to enhanced ion bombardment associated with the increased Cr content, attributed to Cr’s relatively higher atomic mass compared to Al. Coatings with lower hardness exhibited greater scratch resistance, likely due to the influence of residual compressive stresses. The findings highlight the critical role of both Cr/Al content and substrate bias in tailoring the tribo-mechanical performance of PVD CrAlN coatings for wear-resistant applications. Full article

TiAl alloy offers advantages including low density, high specific strength and stiffness, and excellent high-temperature creep resistance. It is widely used in the aerospace, automotive, and chemical sectors, as well as in other fields. However, at temperatures of 800 °C and above, it forms a porous oxide film predominantly composed of TiO₂, which fails to provide adequate protection. Applying high-temperature protective coatings is therefore essential. Oxides demonstrating protective efficacy at elevated temperatures include Al₂O₃, Cr₂O₃, and SiO₂. The Pilling–Bedworth Ratio (PBR)—defined as the ratio of the volume of the oxide formed to the volume of the metal consumed—serves as a critical criterion for assessing oxide film integrity. A PBR value greater than 1 but less than 2 indicates superior film integrity and enhanced oxidation resistance. Among common oxides, Al₂O₃ exhibits a PBR value within this optimal range (1−2), rendering aluminum-based compound coatings the most extensively utilized. Aluminum coatings can be applied via methods such as pack cementation, thermal spraying, and hot-dip aluminizing. Pack cementation, being the simplest to operate, is widely employed. In this study, a powder mixture with the composition Al:Al₂O₃:NH₄Cl:CeO₂ = 30:66:3:1 was used to aluminize γ-TiAl intermetallic compound specimens via pack cementation at 600 °C for 5 h. Subsequent isothermal oxidation at 900 °C for 20 h yielded an oxidation kinetic curve adhering to the parabolic rate law. This treatment significantly enhanced the high-temperature oxidation resistance of the γ-TiAl intermetallic compound, thereby broadening its potential application scenarios. Full article

Ultrahigh-temperature ceramic composites based on hafnium diboride have a wide range of applications, including as components for high-speed aircraft and energy generation and storage devices. Consequently, developing methodologies for their fabrication and studying their properties are of paramount importance, in particular in using them as an electrode material for energy storage devices with increased oxidation resistance. This study investigates the behavior of ceramic composites based on the HfB₂-HfO₂-SiC system, obtained using 15 vol% Ti₂AlC MAX-phase as a sintering component, under the influence of subsonic flow of dissociated air. It was determined that incorporating the modifying component (Ti₂AlC) altered the composition of the silicate melt formed on the surface during ceramic oxidation. This modification led to the observation of a protective antioxidant function. Consequently, liquation was observed in the silicate melt layer, resulting in the formation of spherical phase inhomogeneities in its volume with increased content of titanium, aluminum, and hafnium. It is hypothesized that the increase in the high-temperature viscosity of this melt prevents it from being carried away in the form of drops, even at a surface temperature of ~1900–2000 °C. Despite the established temperature, there is no sharp increase in its values above 2400–2500 °C. This is due to the evaporation of silicate melt from the surface. In addition, the electrochemical behavior of the obtained material in a liquid electrolyte medium (KOH, 3 mol/L) was examined, and it was shown that according to the value of electrical conductivity and specific capacitance, it is a promising electrode material for supercapacitors. Full article

Difficult, extreme operating conditions of parabolic antennas under precipitation and sub-zero temperatures require the creation of effective heating systems. The purpose of the research is to develop a multilayer coating containing two metal-ceramic layers, epoxy composite layers, carbon fabric, and an outer layer of basalt fabric, which allows for effective heating of the antenna, and to study the properties of this coating. The multilayer coating was formed on an aluminum base that was subjected to abrasive jet processing. The first and second metal-ceramic layers, Al₂O₃ + 5% Al, which were applied by high-speed multi-chamber cumulative detonation spraying (CDS), respectively, provide maximum adhesion strength to the aluminum base and high adhesion strength to the third layer of the epoxy composite containing Al₂O₃. On this not-yet-polymerized layer of epoxy composite containing Al₂O₃, a layer of carbon fabric (impregnated with epoxy resin) was formed, which serves as a resistive heating element. On top of this carbon fabric, a layer of epoxy composite containing Cr₂O₃ and SiO₂ was applied. Next, basalt fabric was applied to this still-not-yet-polymerized layer. Then, the resulting layered coating was compacted and dried. To study this multilayer coating, X-ray analysis, light and raster scanning microscopy, and transmission electron microscopy were used. The thickness of the coating layers and microhardness were measured on transverse microsections. The adhesion strength of the metal-ceramic coating layers to the aluminum base was determined by both bending testing and peeling using the adhesive method. It was established that CDS provides the formation of metal-ceramic layers with a maximum fraction of lamellae and a microhardness of 7900–10,520 MPa. In these metal-ceramic layers, a dispersed subgrain structure, a uniform distribution of nanoparticles, and a gradient-free level of dislocation density are observed. Such a structure prevents the formation of local concentrators of internal stresses, thereby increasing the level of dispersion and substructural strengthening of the metal-ceramic layers’ material. The formation of materials with a nanostructure increases their strength and crack resistance. The effectiveness of using aluminum, chromium, and silicon oxides as nanofillers in epoxy composite layers was demonstrated. The presence of structures near the surface of these nanofillers, which differ from the properties of the epoxy matrix in the coating, was established. Such zones, specifically the outer surface layers (OSL), significantly affect the properties of the epoxy composite. The results of industrial tests showed the high performance of the multilayer coating during antenna heating. Full article

Cr/Ti bilayer coatings were deposited on 7050 aluminum alloy via magnetron sputtering at substrate temperatures of room temperature (RT), 150 °C, and 300 °C to investigate temperature effects on microstructure, hardness, and corrosion resistance. All coatings exhibited Cr(110) and Ti(002) phases. Temperature significantly modulated corrosion resistance by altering pore density, grain boundary density, and passivation film composition. Increasing temperature from RT to 150 °C raised corrosion rates primarily due to increased pore density. Further increasing to 300 °C reduced corrosion rates mainly through decreased grain boundary density, while passivation film composition changes altered electrochemical reaction kinetics. Substrate-coating interface defect density primarily influenced hardness with minimal effect on corrosion. Consequently, the RT-deposited coating, despite lower hardness, demonstrated optimal corrosion resistance: polarization resistance (7.17 × 10⁴ Ω·cm²), charge transfer resistance (12,400 Ω·cm²), and corrosion current density (2.47 × 10⁻⁷ A/cm²), the latter being two orders of magnitude lower than the substrate. Full article

Aluminum matrix composites provide an ideal solution for lightweight brake disks, but conventional casting processes are prone to crack initiation due to inhomogeneous reinforcement dispersion, gas porosity, and inadequate toughness. To break the conventional trade-off between high wear resistance and low toughness of brake disks, this study fabricated a bimetallic structure of SiC_p/Al–Fe–V–Si aluminum matrix composite and cast ZL101 alloy using friction stir lap welding (FSLW). Then, the microstructural evolution, mechanical properties, and tribological behavior of the FSLW joints were studied by XRD, SEM, TEM, tensile testing, and tribological tests. The results showed that the FSLW process homogenized the distribution of SiC particle reinforcements in the SiC_p/Al–Fe–V–Si composites. The Al₁₂(Fe,V)₃Si heat-resistant phase was not decomposed or coarsened, and the mechanical properties were maintained. The FSLW process refined the grains of the ZL101 aluminum alloy through recrystallization and fragmented eutectic silicon, improving elongation to 22%. A metallurgical bond formed at the joint interface. Tensile fracture occurred within the ZL101 matrix, demonstrating that the interfacial bond strength exceeded the alloy’s load-bearing capacity. In addition, the composites exhibited significantly enhanced wear resistance after FSLW, with their wear rate reduced by approximately 40% compared to the as-received materials, which was attributed to the homogenized SiC particle distribution and the activation of an oxidative wear mechanism. Full article

Corrosion fatigue damage significantly affects the long-term service of marine platforms such as propellers. Fatigue testing of pre-corrosion specimens is essential for understanding damage mechanisms and accurately predicting fatigue life. However, traditional seawater-based tests are time-consuming and yield inconsistent results, making them unsuitable for rapid evaluation of newly developed equipment. This study proposes an accelerated corrosion testing method for ZCuAl₈Mn₁₃Fe₃Ni₂ nickel–aluminum bronze, simulating the marine full immersion zone by increasing temperature, adding H₂O₂, reducing the solution pH, and preparing the special solution. Coupled with the fatigue test of pre-corrosion specimens, the corrosion damage characteristics and their influence on fatigue performance were analyzed. A numerical simulation method was developed to predict the fatigue life of pre-corrosion specimens, showing an average error of 13.82%. The S–N curves under different pre-corrosion cycles were also established. The research results show that using the test solution of 0.6 mol/L NaCl + 0.1 mol/L H₃PO₄-NaH₂PO₄ buffer solution + 1.0 mol/L H₂O₂ + 0.1 mL/500 mL concentrated hydrochloric acid for corrosion acceleration testing shows good corrosion acceleration. Moreover, the test methods ensure accuracy and reliability of the fatigue behavior evaluation of pre-corrosion specimens of the structure under actual service environments, offering a robust foundation for the material selection, corrosion resistance evaluation, and fatigue life prediction of marine structural components. Full article

Aluminum–copper casting alloys are potential candidate materials for use in marine applications where high mechanical strength and superior fatigue resistance are desired. The corrosion and protection of aluminum alloy B206 in seawater through surface passivation continues to pose challenges, hampering its widespread use in marine structures. In this study, the electrochemical behavior of B206 is investigated in artificial seawater at temperatures and dissolved oxygen (DO) concentrations anticipated during service in marine environments. In particular, the influence of anodizing B206 in deaerated seawater on the subsequent corrosion behavior of the alloy is studied using potentiodynamic and potentiostatic polarization, electrochemical impedance spectroscopy (EIS), and Mott–Schottky analysis. The results showed that the effect of DO on the corrosion of B206 is more significant than the effect of temperature. In the absence of DO, results of potentiostatic polarization, EIS, and Mott–Schottky analysis at anodic potentials all indicated the development of a thicker, more protective passive layer in colder seawater. Moreover, passive layer thickness modeled using Power-Law was found to range between 3 and 9 nm, whilst decreasing in thickness with temperature. Donor densities of the n-type passive layer are on the order of 1021 cm⁻³ and increase with temperature. The findings presented in this study support the feasibility of implementing anodizing for B206 in marine service environments. Full article

Silica/alumina composite particles were synthesized via the sol–gel method to promote fine dispersion and homogenous mixing. Aluminum chloride hydroxide served as the alumina precursor, while amorphous silica, obtained from rice husk, was directly incorporated into the alumina sol. Following synthesis, the material was calcined at 1000 °C, yielding an α-cristobalite form of silica and corundum-phase alumina. These hybrid particles were introduced into polymer composites at reinforcement levels of 1 wt.%, 3 wt.%, and 5 wt.%. Mechanical behavior was evaluated through three-point bending tests, Shore D hardness measurements, and controlled-energy impact testing. Among the formulations, the 3 wt.% composite exhibited optimal performance, displaying the highest flexural modulus and strength, along with enhanced impact resistance. Hardness increased with rising particle content. Fractographic analysis revealed that the 3 wt.% loading produced a notably rougher fracture surface, correlating with improved energy absorption. In contrast, the 5 wt.% composite, although harder than the matrix and other composites, exhibited diminished toughness due to particle agglomeration. Full article

Transparent conductive oxides (TCOs) have become essential components in a broad range of modern devices, including smartphones, flat-panel displays, and photovoltaic cells. Currently, indium tin oxide (ITO) is used in approximately 90% of these devices. However, ITO prices continue to rise due to the limited supply of indium (In), making the development of alternative materials for TCOs indispensable. Therefore, this study highlights the latest advances in creating new, affordable materials, with a focus on aluminum-doped zinc oxide (AZO). Over the last few decades, this material has been widely studied to improve its physical properties, particularly its low electrical resistivity, which can affect the performance of various devices. Now, it is close to replacing ITO due to several advantages including cost-effectiveness, stability under hydrogen plasma, low processing temperatures, and lack of toxicity. Besides that, in comparison to other TCOs such as IZO, IGZO, or IZrO, AZO achieved a low electrical resistivity (10⁻⁵ ohm cm) while maintaining a high transparency across the visible spectrum (over 85%). Additionally, due to the increasing development of technologies utilizing such materials, it is essential to develop more effective techniques for producing TCOs on a larger scale. Additionally, due to the increasing development of technologies utilizing such materials, it is essential to develop more effective techniques for producing TCOs on a larger scale. This review emphasizes the potential of AZO as a cost-effective and scalable alternative to ITO, highlighting key advancements in deposition techniques such as pulsed laser deposition (PLD). Full article