Search Results (57)

This study addresses the critical challenges of hydrogen permeation and embrittlement in metallic pipelines for hydrogen storage and transportation by developing an epoxy resin-based composite coating with enhanced hydrogen barrier properties. Using cold spray technology, the fabricated coatings with controlled 250–320 μm thicknesses incorporating graphene/ceramic composite particles uniformly dispersed in the epoxy matrix. Microstructural characterization revealed dense morphology and excellent interfacial bonding. Electrochemical hydrogen charging tests demonstrated remarkable hydrogen permeation reduction, showing a strong positive correlation between coating thickness and barrier performance. The optimal 320 μm-thick coating achieved a hydrogen content of only 0.28 ± 0.09 ppm, representing an 89% reduction compared to that in uncoated substrates. The superior performance originates from the Al₂O₃/SiO₂ networks providing physical barriers, graphene offering high-surface-area adsorption sites, and MgO chemically trapping hydrogen atoms. Post-charging analysis identified interfacial stress concentration and hydrogen-induced plasticization as primary causes of ceramic particle delamination. This work provides both fundamental insights and practical solutions for designing high-performance protective coatings in long-distance hydrogen pipelines. Full article

Lead (Pb) and cadmium (Cd) ions have serious negative impacts on human health and the ecological environment due to toxicity, persistence and nonbiodegradability. Among various trace Pb and Cd ions detection technologies, electrochemical analysis is considered as one of the most promising methods. The deposition of Bi nanoparticles on delaminated Ti₃C₂T_x (DL-Ti₃C₂T_x) develops a sensor with good conductivity and performance. Square wave anodic stripping voltammetry (SWASV) technology was applied to simultaneously deposit Bi on DL-Ti₃C₂T_x/GCE and achieve the rapid detection of Pb and Cd ions. The Bi nanoparticles effectively improved the sensitivity of Bi/DL-Ti₃C₂T_x/GCE sensors to detect Pb and Cd ions. The preparation conditions of the Bi/DL-Ti₃C₂T_x/GCE were optimized, including DL-Ti₃C₂T_x droplet amount, solution pH, Bi³⁺ concentration, deposition time and deposition potential, to improve the detection ability. The Bi/DL-Ti₃C₂T_x/GCE sensor has detection limits of 1.73 and 1.06 μg/L for Pb and Cd ions, respectively (S/N > 3). This electrochemical sensor is easy, sensitive and selective to apply in actual water samples for trace Pb and Cd ions detection. Full article

Antidepressants are emerging contaminants that have raised global concern due to their abuse. Venlafaxine (VFX), a serotonin and norepinephrine reuptake inhibitor, can cause adverse and potentially toxic effects on aquatic organisms. Electrochemical advanced oxidation processes (EAOPs) are gaining attention as promising degradation techniques for a variety of drugs. EAOP methods proposed for VFX degradation mainly utilize boron-doped diamond (BDD) electrodes, characterized by low background current and high oxygen overpotential. However, challenges arise, including delamination from the substrate, difficulties in scaling up, and limited service life. In this study, platinum was employed as an anode for the galvanostatic degradation of VFX, due to its stability and well-established surface cleaning procedure, which ensured high reproducibility. A 0.1 M Na₂SO₄ solution at pH 9 was used as the supporting electrolyte, and a current density of 25 mA/cm² was applied. After 7 h, a degradation efficiency of 94% was achieved for a 25 ppm VFX solution. The hydroxyl and sulfate radicals generated in the electrochemical system were the active species responsible for VFX degradation, which followed a first-order kinetic model with a rate constant of 0.0084 min⁻¹. The main degradation intermediates were identified through LC-MS, including two isomers with a nominal m/z of 276 and three isomers with a nominal m/z of 294. The toxicity of the VFX degradation products was assessed by an in silico prediction model. This evaluation confirmed the sustainability of the developed method. Full article

This study presents a novel approach to evaluate the galvanic corrosion risk of mild steel coated with graphene-embedded epoxy coatings. The potential for graphene platelets to promote anodic dissolution of the underlying steel substrate via galvanic corrosion mechanisms was systematically assessed through the accelerated alternating current-direct current-alternating current (AC-DC-AC) technique and cathodic disbondment testing. The possible risk of displacing cathodic reactions from the coating–steel interface to the dispersed graphene platelets within the epoxy matrix was investigated by evaluating the degradation trend of the graphene-containing coating under the AC-DC-AC test. The degradation behaviour of both pure epoxy and graphene-embedded epoxy coatings during accelerated aging was characterized using electrochemical impedance spectroscopy (EIS) measurements. The finding highlighted the negligible catalytic effect of incorporated graphene platelets on the anodic dissolution of steel substrate. On the other hand, as an inert filler, graphene platelets contributed to the enhancement of the structural integrity of the epoxy matrix during the AC-DC-AC test and natural immersion in NaCl 3.5 wt % solution by enhancing the barrier performance of the coating. Despite their spectacular barrier performance, damaged graphene-containing coatings performed inferiorly against corrosion-induced delamination compared to pure epoxy. Samples underwent the cathodic disbondment test to eliminate the effect of substrate anodic dissolution from corrosion-induced delamination. The accelerated delamination of graphene-embedded epoxy coatings was attributed to the destructive impact of graphene platelets on the interfacial adhesion of the epoxy matrix to the steel substrate. Full article

In this work, two alloys of Ni₃₅Al₃₀(FeCo)₂₅Cr_10-xMo_x (x = 0, 5) were prepared via the vacuum arc melting method, and the effects of Mo on the microstructure, mechanical properties, and friction and wear properties of the alloys were investigated. The addition of Mo improved the mechanical properties, wear resistance, and corrosion resistance of the alloy system. With the addition of trace amounts of Mo, the precipitate phase of the alloys transformed from spherical to acicular and plate-like. The precipitated phases in a co-lattice relationship with the matrix allow for a substantial increase in the strength of the alloy at both room and elevated temperatures without a significant loss of plasticity. Ni₃₅Al₃₀(FeCo)₂₅Cr₅Mo₅ has excellent mechanical properties, with a hardness of 558.2 HV; a yield strength of 1320 MPa at 600 °C; and a yield strength of 537 MPa at 850 °C. As the temperature increased, the wear mechanism changed from abrasive wear to adhesive wear. At 600 °C, Ni₃₅Al₃₀(FeCo)₂₅Cr₅Mo₅ had the lowest wear rate of 1.78 × 10⁻⁵ (mm³/Nm). The precipitated phases, which have high hardness and maintain a conformal interface with the matrix, play an important role in slowing delamination wear, keeping the wear rate of this alloy low at both room and high temperatures. Electrochemical experiments on the two alloys at room temperature revealed that Ni₃₅Al₃₀(FeCo)₂₅Cr₅Mo₅ exhibited excellent resistance to pitting, with a pitting potential of 0.016 V. Full article

This article outlines the method of creating electrodes for electrochemical sensors using hybrid nanostructures composed of graphene and conducting polymers with insertion of gold nanoparticles. The technology employed for graphene dispersion and support stabilization was based on the chemical vapor deposition technique followed by electrochemical delamination. The method used to obtain hybrid nanostructures from graphene and conductive polymers was drop-casting, utilizing solutions of P3HT, PANI-EB, and F8T2. Additionally, the insertion of gold nanoparticles utilized an innovative dip-coating technique, with the graphene-conducting polymer frameworks submerged in a HAuCl₄/2-propanol solution and subsequently subjected to controlled heating. The integration of gold nanoparticles differs notably, with P3HT showing the least adhesion of gold nanoparticles, while PANI-EB exhibits the highest. An inkjet printer was employed to create electrodes with metallization accomplished through the use of commercial silver ink. Notable variations in roughness (grain size) result in unique behaviors of these structures, and therefore, any potential differences in the sensitivity of the generated sensing structures can be more thoroughly understood through this spatial arrangement. The electrochemical experiments utilized a diluted sulfuric acid solution at three different scan rates. The oxidation and reduction potentials of the structures seem fairly alike. Nevertheless, a notable difference is seen in the anodic and cathodic current densities, which appear to be largely influenced by the active surface of gold nanoparticles linked to the polymeric grains. The graphene–PANI-EB structure with Au nanoparticles showed the highest responsiveness and will be further evaluated for biomedical applications. Full article

Marine environment-induced apparatus failures have led to substantial losses in marine engineering. Graphite/copper composites, known for their excellent electrical conductivity and wear resistance, are extensively utilized in various electric contact devices. However, research on the current-carrying friction and wear behavior of graphite/copper composites in marine environments is still limited. This study investigates the effects of mating materials, graphite content (30 wt.% and 45 wt.%), and electric voltage on the friction and wear mechanisms of graphite/copper composites in seawater. The results show that under seawater coupled with electricity, no mass loss was observed in the 30 wt.% graphite composites after friction tests against different counterparts. Electric voltage (3 V) affects the composite’s damage mechanism, inducing delamination wear, arc erosion and accelerating corrosion. Specifically, the electricity factor promotes oxidation recreations while inhibiting chlorine formation. Notably, when the composite is paired with gold-coated copper, it undergoes electrochemical reactions, leading to the formation of needle-like copper oxide. These oxides alter the surface morphology, elevate the mass of worn composites, and raise the friction coefficient of the tribopair to approximately 0.3, an increase from 0.2. Full article

Despite their high specific capacity, magnetron-sputtered Si/Al thin films face rapid capacity decay due to stress-induced cracking, delamination, and detrimental electrolyte reactions. This study introduces a carbon-coated composite anode that overcomes these limitations, delivering superior reversible capacity, exceptional rate capability, and stable cycling performance. An electrochemical evaluation reveals that the CF-Si/Al@C-500-1h composite exhibits marked enhancements in capacity retention (43.5% after 100 cycles at 0.6 A·g⁻¹) and rate capability, maintaining 579.1 mAh·g⁻¹ at 3 A·g⁻¹ (1 C). The carbon layer enhances electrical conductivity, buffers volume expansion during lithiation/delithiation, and suppresses silicon aggregation and electrolyte side reactions. Coupled with an aluminum framework, this architecture ensures robust structural integrity and efficient lithium-ion transport. These advancements position CF-Si/Al@C-500-1h as a promising anode material for next-generation lithium-ion batteries, while insights into scalable fabrication and carbon integration strategies pave the way for practical applications. Full article

Cortisol, a steroid hormone, is closely associated with human mental stress. The rapid, real-time, and continuous detection of cortisol using wearable devices offers a promising approach for individual mental health. These devices must exhibit high sensitivity and long-term stability to ensure reliable performance. This study developed a wearable electrochemical sensor based on molecularly imprinted polymer (MIP) technology for real-time and dynamic monitoring of cortisol in sweat. A flexible gold (Au) electrode with interfacial hydrophilic treatment was employed to construct a highly stable electrode. The integration of a silk fibroin/polyvinylidene fluoride (SF/PVDF) composite membrane facilitates directional sweat transport, while liquid metal bonding enhances electrode flexibility and mechanical anti-delamination capability. The sensor exhibits an ultrawide detection range (0.1 pM to 5 μM), high selectivity (over 100-fold against interferents such as glucose and lactic acid), and long-term stability (less than 3.76% signal attenuation over 120 cycles). Additionally, a gradient modulus design was implemented to mitigate mechanical deformation interference under wearable conditions. As a flexible wearable device for cortisol monitoring in human sweat, the sensor’s response closely aligns with the diurnal cortisol rhythm, offering a highly sensitive and interference-resistant wearable solution for mental health monitoring and advancing personalized dynamic assessment of stress-related disorders. Full article

Shells are primarily composed of calcite and aragonite, making the inclusion of micronized shells as bio-based fillers in organic coatings a potential means to enhance the mechanical properties of the layers. A water-based coating was reinforced with 5 wt.% Acanthocardia tuberculata powder, 5 wt.% Mytilus galloprovincialis powder, and 5 wt.% of an LDPE/ceramic/nanoceramic composite. An improvement in abrasion resistance was achieved using micronized seashells, as demonstrated by the Taber test (evaluating both weight loss and thickness reduction). Additionally, Buchholz hardness improved with powders derived from Mytilus galloprovincialis. No significant differences were observed among the samples in terms of color and gloss after 200 h of UV-B exposure. However, the delamination length from the scratch after 168 h of exposure in a salt spray chamber indicated that the addition of particles to the polymeric matrix resulted in premature degradation, likely due to the formation of preferential paths for water penetration from the scratch. This hypothesis was supported by electrochemical impedance spectroscopy measurements, which revealed a decrease in total impedance at 0.01 Hz shortly after immersion in a 3.5% NaCl solution. In conclusion, the particle size and shape of the micronized shells improved abrasion resistance without altering color and gloss but led to a decrease in the coating’s isolation properties. Full article

The preparation of 2H-phase MoS₂ thin nanosheets by electrochemical delamination remains a challenge, despite numerous efforts in this direction. In this work, by choosing appropriate intercalating cations for cathodic delamination, the insertion process was facilitated, leading to a higher degree of exfoliation while maintaining the original 2H-phase of the starting bulk MoS₂ material. Specifically, trimethylalkylammonium cations were tested as electrolytes, outperforming their bulkier tetraalkylammonium counterparts, which have been the focus of past studies. The performance of novel electrochemically derived 2H-phase MoS₂ nanosheets as electrode material for electrochemical energy storage in lithium-ion batteries was investigated. The lower thickness and thus higher flexibility of cathodically exfoliated MoS₂ promoted better electrochemical performance compared to liquid-phase and ultrasonically assisted exfoliated MoS₂, both in terms of capacity (447 vs. 371 mA·h·g⁻¹ at 0.2 A·g⁻¹) and rate capability (30% vs. 8% capacity retained when the current density was increased from 0.2 A·g⁻¹ to 5 A·g⁻¹), as well as cycle life (44% vs. 17% capacity retention at 0.2 A·g⁻¹ after 580 cycles). Overall, the present work provides a convenient route for obtaining MoS₂ thin nanosheets for their advantageous use as anode material for lithium storage. Full article

The study investigated the effect of sebacate as a corrosion inhibitor for acrylic-coated steel. Specifically, it examined its impact on mitigating a frequent case of paint delamination, known as filiform corrosion (FFC), through a chosen weathering test designed to stress the degradation of the produced samples. Sebacate was demonstrated to be an efficient organic molecule for enhancing the corrosion resistance of steel. This efficacy was evaluated through electrochemical characterization based on electrochemical impedance spectroscopy measurements and potentiodynamic polarization curves, including the application of an FFC susceptibility prediction methodology based on measurements obtained in FFC-simulated electrolytes. An inhibition efficiency of 98% was measured in near-neutral saline solutions compared to conditions lacking inhibitor presence. During FFC simulation, the primary effect observed was associated with a reduction in cathodic activity evolution. Furthermore, a significant reduction in corrosion creep evolution of 35% was found. These experimental findings aligned closely with the outcomes projected by the simulated investigations. Full article

This paper describes the process of producing chemiresistors based on hybrid nanostructures obtained from graphene and conducting polymers. The technology of graphene presumed the following: dispersion and support stabilization based on the chemical vapor deposition technique; transfer of the graphene to the substrate by spin-coating of polymethyl methacrylate; and thermal treatment and electrochemical delamination. For the process at T = 950 °C, a better settlement of the grains was noticed, with the formation of layers predominantly characterized by peaks and not by depressions. The technology for obtaining hybrid nanostructures from graphene and conducting polymers was drop-casting, with solutions of Poly(3-hexylthiophene (P3HT) and Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2). In the case of F8T2, compared to P3HT, a 10 times larger dimension of grain size and about 7 times larger distances between the peak clusters were noticed. To generate chemiresistors from graphene–polymer structures, an ink-jet printer was used, and the metallization was made with commercial copper ink for printed electronics, leading to a structure of a resistor with an active surface of about 1 cm². Experimental calibration curves were plotted for both sensing structures, for a domain of CH₄ of up to 1000 ppm concentration in air. A linearity of the curve for the low concentration of CH₄ was noticed for the graphene structure with F8T2, presenting a sensitivity of about 6 times higher compared with the graphene structure with P3HT, which makes the sensing structure of graphene with F8T2 more feasible and reliable for the medical application of irritable bowel syndrome evaluation. Full article

Surgical ASTM F139 stainless steel is used for temporary fixtures in the biomedical field. Tribocorrosion is a major concern in this application. The aim of the present work was to study the interplay between tribocorrosion behavior and the surface chemistry of the ASTM F139 stainless steel in phosphate-buffered saline solution (PBS). Sliding wear tests were conducted against alumina balls at different electrochemical potentials: open circuit potential (OCP), cathodic potential (−100 mV versus the OCP), and anodic potentials (+200 mV_Ag/AgCl and +700 mV_Ag/AgCl). The normal load was 20 N. The wear volume was estimated based on micrographs obtained from the wear tracks using confocal laser scanning microscopy. Moreover, the wear tracks were also examined by scanning electron microscopy (SEM). The surface chemistry of the ASTM F139 specimens was analyzed by X-ray photoelectron spectroscopy (XPS). The wear volume was dependent on the electrochemical potential, being maximized at +700 mVAg/AgCl. Delamination areas and grooves were observed in the wear tracks. Detailed assessment of the surface chemistry inside the wear tracks allowed identification of the main chemical species and their relative quantities, thus enabling correlation of the passive film composition with the observed tribocorrosion behavior. Full article

Alloy coatings protect steel from corrosion in various applications. We investigated the effects of Si addition on the microstructure, electrochemical behavior, and corrosion resistance of steel sheets coated with a hot-dip Zn–Mg–Al–Si alloy using a batch-type galvanization process. Microstructural analysis revealed that the Zn–Al–Mg alloy coating layer contained a significant amount of Fe that diffused from the substrate, leading to delamination due to the formation of brittle Fe–Zn intermetallic compounds. However, the introduction of Si resulted in the formation of a stable Fe₂Al₃Si inhibition layer at the substrate–coating interface; this layer prevented interdiffusion of Fe as well as enhanced the coating adhesion. Additionally, the formation of acicular Mg₂Si phases on the coating surface improved the surface roughness. As the Si content increased, the corrosion resistance of the coating improved. Specifically, the Zn–Al–Mg coating layer with 0.5 wt.% Si exhibited excellent anti-corrosion performance, without red rust formation on its surface even after 2600 h, during a salt spray test. Full article