Search Results (40)

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

Declining natural resources make the recovery of metals from waste solutions a promising alternative. Moreover, processing waste into a finished product has its economic justification and benefits. Thus, the aim of this research was developing a Waste for Product strategy, indicating the possibility of processing solutions with a low content of platinum-group metals for catalyst synthesis. The results obtained confirmed that diluted synthetic waste solutions containing trace amount of valuable metal ions (Pd, Pt) can be used for the process of catalyst synthesis. Catalysts produced in the form of palladium and platinum nanoparticles were successfully deposited on a Ni foam due to the galvanic displacement mechanism. Synthesized catalysts were characterized using UV-Vis spectrophotometry, SEM/EDS, and XRD techniques. Electro- and catalytic properties were tested for hydrogen/oxygen evolution reactions and methyl orange degradation, respectively. The results obtained from electrocatalytic tests indicated that the modification of the nickel foam surface by waste solutions consisting of noble metals ions as Pd and Pt can significantly increase the activity in hydrogen and oxygen evolution reactions in comparison to non-treated samples. Catalytic tests performed for the process of methyl orange degradation shorten the time of the process from several hours to 15 min. The most favorable results were obtained for the catalysts in the following order Pd1.0Pt0@Ni > Pd0Pt1.0@Ni > Pd0.5Pt0.5@Ni > Ni foam > no catalyst, indicating the best catalytic performance for catalyst containing pure palladium nanoparticles deposited on the nickel surface. Full article

Background/Objectives: Galvanic vestibular stimulation (GVS) integrated into virtual reality (VR) environments enhances immersion and mitigates cybersickness. It is well known that GVS can affect standing balance. Most studies have investigated the effects of GVS in VR in seated conditions. The purpose of this study was to evaluate the impact of joint GVS and VR with moving visual stimulus on standing balance. Methods: Using a repeated measures counter-balanced design, motion sickness, postural sway, and velocity utilizing the center of pressure (COP) along the mediolateral (ML) and anteroposterior (AP) axes were obtained in 18 subjects during optokinetic (OPK) stimulus (black and white vertical bars moving from left to the right) in VR across three interventions: GVS in the same direction of visual stimulus—left to right ear (Positive GVS), GVS in the opposite direction of visual stimulus—right to left ear (Negative GVS), and without GVS (Null GVS). Motion sickness symptom scoring was obtained using the Pensacola Diagnostic Index. Results: The PDI score was increased significantly in the Negative GVS. The root mean square and sway range of COP along ML was greater during the Positive GVS and Negative GVS than the Null GVS, while, along AP, it was only greater during Negative GVS. During Positive GVS, mean positive and negative peak velocities, only in ML, were increased and decreased, respectively. During Negative GVS, only negative peak velocities in both ML and AP directions were decreased. Conclusions: This research highlights the importance of testing combined VR and GVS to assess standing balance while mitigating cybersickness. Full article

This study explores the feasibility of using low-intensity focused ultrasound (LIFU) to induce rotational sensations in the human semicircular canal (SCC) through the acoustic streaming effect. Existing vestibular stimulation methods, such as galvanic vestibular stimulation (GVS), caloric vestibular stimulation (CVS), and magnetic vestibular stimulation (MVS), face limitations in spatial and temporal resolution, with unclear mechanisms. This study investigates whether LIFU can overcome these limitations by modulating endolymph motion within SCC. A 3D finite element model was constructed to simulate the effects of LIFU-induced acoustic streaming on SCC (particularly the endolymph), with thermal effects evaluated to ensure safety. Fluid–structure interaction (FSI) was used to analyze the relationship between endolymph flow and cupula deformation. By adjusting the focal point of the ultrasound transducer, we were able to alter fluid flow pattern, which resulted in variations in cupula displacement. The results demonstrated that LIFU successfully induces fluid motion in SCC without exceeding thermal safety limits (<1 °C), suggesting its potential for controlling rotational sensations, with cupula displacement exceeding 1 μm. This novel approach enhances the understanding of LIFU’s thermal and neuromodulatory effects on the vestibular system, and thereby offers promising implications for future therapeutic applications. Full article

The population surge has led to a corresponding increase in the demand for high-rise buildings, bridges, and other heavy structures. In addition to gravity loads, these structures must withstand lateral loads from earthquakes, wind, ships, vehicles, etc. A piled raft foundation (PRF) has emerged as the most favored system for high-rise buildings due to its ability to resist lateral loads. An experimental study was conducted on three different piled raft model configurations with three different relative densities (D_r) to determine the effect of D_r on the lateral response of a PRF. A model raft was constructed using a 25 mm thick aluminum plate with dimensions of 304.8 mm × 304.8 mm, and galvanized iron (GI) pipes, each 457.2 mm in length, were used to represent the piles. The lateral and vertical load cells were connected to measure the applied loads. It was found that an increase in D_r increased the soil stiffness and led to a decrease in the lateral displacement for all three PRF models. Additionally, the contribution of the piles in resisting the lateral load decreased, whereas the contribution of the raft portion in resisting the lateral load increased. With an increase in D_r from 30% to 90%, the percentage contribution of the raft increased from 42% to 66% for 2PRF, 38% to 61% for 4PRF, and 46% to 70% for 6PRF. Full article

The paper deals with the joining of dissimilar steels by adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, and hot-dip galvanized HSLA steel HX340LAD+Z. Adhesive bonding was performed using rubber-based and epoxy-based adhesives. The research aimed to verify the importance of surface preparation of steel substrates using a formulation with organically modified silica nanoparticles and epoxy organic functional groups, where one end of the functional group can be incorporated into the organic binder of the coating material and the other end can be firmly bonded to substances of an inorganic nature (metals). Since the binder base of adhesives is very similar to that of coatings, verifying the performance of this surface preparation when interacting with the adhesive is necessary. The load-bearing tensile shear capacity of single-lapped joints and the resistance of the joints against corrosion-induced disbanding in a climate chamber were tested. The energy dissipated by the joints up to fracture was calculated from the load-displacement curves. Bonded joints with organosilane were compared with joints without surface preparation and joints prepared by chroman-free zirconate passivation treatment. Exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints. Organosilicate formulation was proved effective when bonding ungalvanized steels with a rubber-based structural adhesive, where it improves the bond quality between the adhesive and the substrate. Full article

In the realm of analysis, the lateral flow immunoassay (LFIA) is frequently utilized due to its capability to be fast and immediate. However, the biggest challenge of the LFIA is its low detection sensitivity and tolerance to matrix interference, making it impossible to enable accurate, qualitative analyses. In this study, we developed a new LFIA with higher affinity and sensitivity, based on a nanobody (G8-DIG) and CuS nanoflowers-Au (CuS NFs-Au), for the detection of aflatoxin B₁ (AFB₁) in maize. We synthesized the immunoprobe G8-DIG@CuS NFs-Au, stimulated the in situ development of Au nanoparticles (Au NPs) on Cu NFs by electrical displacement, and obtained Cu NFs-Au for fixing the G8-DIG. G8-DIG@CuS NFs-Au probe-based LFIAs may, in ideal circumstances, use a strip chromatography reader to accomplish sensitive quantitative detection and qualitative visualization. AFB₁ has a detection range of 2.82–89.56 µg/L and a detection limit of 0.87 µg/L. When compared with an LFIA based on CuS NFs, this sensitivity is increased by 2.76 times. The practical application of this method in corn flour demonstrated a recovery rate of 81.7% to 117%. Therefore, CuS NFs-Au show great potential for detecting analytes. Full article

This paper describes the use of wireless smart sensors for examining the underlying mechanism for the wind-induced vibration of high-mast illumination pole (HMIP) structures. HMIPs are tall, slender structures with low inherent damping. Video recordings of multiple HMIPs showed considerable vibrations of these HMIPs under wind loading in the state of Kansas. The HMIPs experienced cyclic large-amplitude displacements at the top, which can produce high-stress demand and lead to fatigue cracking at the bottom of the pole. In this study, the natural frequencies of the HMIP were assessed using pluck tests and finite element modeling, and the recorded vibration frequencies were obtained through computer vision-based video analysis. Meanwhile, a 30.48 m tall HMIP with three LED luminaires made of galvanized steel located in Wakeeney, Kansas, was selected for long-term vibration monitoring using wireless smart sensors to investigate the underlying mechanism for the excessive wind-induced vibrations. Data analysis with the long-term monitoring data indicates that while vortex-induced vibration occurs frequently at relatively low amplitude, buffeting-induced vibration was the leading cause of the excessive vibrations of the monitored HMIP. The findings provide crucial information to guide the design of vibration mitigation strategies for these HMIP structures. Full article

Mechanically stabilized earth (MSE) walls have been widely applied in construction to maintain the stability of high embankments. In Vietnam, imported reinforcement materials are expensive; thus, finding locally available materials for MSE walls is beneficial. This study examines the behavior of an MSE wall using local reinforcement materials in Danang, Vietnam. The MSE was reinforced by self-fabricated galvanized steel grids using CB300V steel with 3 cm ribs. The backfill soil was sandy clay soil from the local area with a low cohesion. A full-scale model with full instrumentation was installed to investigate the distribution of tensile forces along the reinforcement layers. The highest load that caused the wall to collapse due to internal instability (reinforcement rupture) was 302 kN/m², which is 15 times greater than the design load of 20 kN/m². The failure surface within the reinforced soil had a parabolic sliding shape that was similar to the theoretical studies. At the failure load level, the maximum lateral displacement at the top of the wall facing was small (3.9 mm), significantly lower than the allowable displacement for a retaining wall. Furthermore, a numerical model using FLAC software 7.0 was applied to simulate the performance of the MSE wall. The modeling results were in good agreement with the physical model. Thus, self-fabricated galvanized steel grids could confidently be used in combination with the local backfill soil for MSE walls. Full article

This work reports the influence of a reduced graphene oxide (rGO) support on the catalytic performance of Cu@PtRu/rGO electrocatalysts toward methanol oxidation in an acidic medium. These electrocatalysts are synthesized via a two-step reduction method; the first step utilizes ethylene glycol for the reduction of Cu²⁺ ions, forming Cu/rGO. In the second step, spontaneous redox reactions take place, in a process known as galvanic displacement, where the Pt²⁺ and Ru³⁺ species are reduced to form PtRu layers, and the copper is partially oxidized to the solution. Then, the Cu@PtRu/rGO core–shell is produced, comprising Cu in the inner structure (core) and PtRu on the outer part (shell). To compare the catalytic performance of the prepared nanocatalysts (NCs), Pt/C, PtRu/C, and Cu@PtRu/C are also synthesized on Vulcan XC-72R carbon. All catalysts are characterized via X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Cyclic voltammetry (CV) and chronoamperometry (CA) are employed to measure the electrochemical performance. The core–shell/rGO combination is superior in catalytic activity to the traditional Pt/C, PtRu/C, and Cu@PtRu/C catalysts for the methanol oxidation reaction. These results suggest that Cu@PtRu/rGO exhibits a high bulk activity for methanol electrooxidation, a high stability, and a high tolerance to CO poisoning, meaning it is possible to reduce the platinum loading in proton-exchange membrane fuel cells (PEMFCs). Full article

In this work, the synthesis of bimetallic Ag and Cu particles on carbon vulcan (AgCu/C) is reported, synthesized by a simple galvanic displacement method using citrate tribasic hydrate as a co-reducing agent and a commercial material based on Cu/C as a template. The materials were characterized by several physicochemical techniques, including TGA, ICP-OES, XRD, SEM, and BET. The catalysts were evaluated as cathodic catalysts for the oxygen reduction reaction (ORR) and were used for the preparation of membrane electrode assemblies for evaluation in an Anion Exchange Membrane Fuel Cell (AEMFC). The results were compared with the commercial Ag/C and Cu/C catalysts; the bimetallic catalyst obtained a higher power density, which was attributed to a synergistic effect between Ag and Cu particles. Full article

The current article discusses surface-enhanced Raman spectroscopy (SERS) as a powerful technique for detecting molecules or ions by analyzing their molecular vibration signals for fingerprint peak recognition. We utilized a patterned sapphire substrate (PSS) featuring periodic micron cone arrays. Subsequently, we prepared a three-dimensional (3D) PSS-loaded regular Ag nanobowls (AgNBs) array using self-assembly and surface galvanic displacement reactions based on polystyrene (PS) nanospheres. The SERS performance and structure of the nanobowl arrays were optimized by manipulating the reaction time. We discovered that the PSS substrates featuring periodic patterns exhibited superior light-trapping effects compared to the planar substrates. The SERS performance of the prepared AgNBs-PSS substrates was tested under the optimized experimental parameters with 4-mercaptobenzoic acid (4-MBA) as the probe molecule, and the enhancement factor (EF) was calculated to be 8.96 × 10⁴. Finite-difference time-domain (FDTD) simulations were conducted to explain that the AgNBs arrays’ hot spots were distributed at the bowl wall locations. Overall, the current research offers a potential route for developing high-performance, low-cost 3D SERS substrates. Full article

Ni coatings with high catalytic efficiency were synthesised in this work, obtained by increasing the active surface and modifying Pd as a noble metal. Porous Ni foam electrodes were obtained by electrodeposition of Al on a nickel substrate. Deposition of Al was carried out with potential −1.9 V for a time of 60 min in NaCl–KCl-3.5 mol%AlF₃ molten salt mixture at 900 °C, which is connected with the formation of the Al-Ni phase in the solid state. Dissolution of Al and Al-Ni phases was performed by application of the potential −0.5 V, which provided the porous layer formation. The obtained porous material was compared to flat Ni plates in terms of electrocatalytic properties for ethanol oxidation in alkaline solutions. Cyclic voltammetry measurements in the non-Faradaic region revealed the improvement in morphology development for Ni foams, with an active surface area 5.5-times more developed than flat Ni electrodes. The catalytic activity was improved by the galvanic displacement process of Pd(II) ions from dilute chloride solutions (1 mM) at different times. In cyclic voltammetry scans, the highest catalytic activity was registered for porous Ni/Pd decorated at 60 min, where the maximum oxidation peak for 1 M ethanol achieved +393 mA cm⁻² compared to the porous unmodified Ni electrode at +152 mA cm⁻² and flat Ni at +55 mA cm⁻². Chronoamperometric measurements in ethanol oxidation showed that porous electrodes were characterised by higher catalytic activity than flat electrodes. In addition, applying a thin layer of precious metal on the surface of nickel increased the recorded anode current density associated with the electrochemical oxidation process. The highest activity was recorded for porous coatings after modification in a solution containing palladium ions, obtaining a current density value of about 55 mA cm⁻², and for a flat unmodified electrode, only 5 mA cm⁻² after 1800 s. Full article

In this study, NiMo catalysts that have different metal loadings in the range of ca. 28–106 µg cm⁻² were electrodeposited on the Ti substrate followed by their decoration with a very low amount of Au-crystallites in the range of ca. 1–5 µg cm⁻² using the galvanic displacement method. The catalytic performance for hydrogen evolution reaction (HER) was evaluated on the NiMo/Ti and Au(NiMo)/Ti catalysts in an alkaline medium. It was found that among the investigated NiMo/Ti and Au(NiMo)/Ti catalysts, the Au(NiMo)/Ti-3 catalyst with the Au loading of 5.2 µg cm⁻² gives the lowest overpotential of 252 mV for the HER to reach a current density of 10 mA·cm⁻². The current densities for HER increase ca. 1.1–2.7 and ca. 1.1–2.2 times on the NiMo/Ti and Au(NiMo)/Ti catalysts, respectively, at −0.424 V, with an increase in temperature from 25 °C to 75 °C. Full article

Reducing the amount of noble metals in catalysts for electrochemical conversion devices is paramount if these devices are to be commercialized. Taking advantage of the high degree of particle property control displayed by the sonochemical method, we set out to synthesize Cu@Pt bimetallic nanocatalysts in an effort to improve the mass activity towards the hydrogen evolution reaction. At least 17 times higher mass activity was found for the carbon supported Cu@Pt bimetallic nanocatalyst (737 mA mg⁻¹, E = $-20$$\mathrm{m}$$\mathrm{V}$) compared to carbon supported Pt nanocatalysts prepared with the same ultrasound conditions (44 mA mg⁻¹, E = $-20$$\mathrm{m}$$\mathrm{V}$). The synthesis was found to proceed with the sonochemical formation of Cu and Cu₂O nanoparticles with the addition of PtCl₄ leading to galvanic displacement of the Cu-nanoparticles and the formation of a Pt-shell around the Cu-core. Full article