Passive Phenomenon Research Articles

Effects of varying pH on the passive film formation in high-strength anti-seismic rebar

ABSTRACT In this paper, electrochemical measurements (CV, PDP, M-S and EIS) and surface characterisation techniques (SEM, EDS, AFM, TEM and XPS) were used to study the passivation phenomenon in high-strength anti-seismic rebar under varying pH conditions. The results show that a passive film with a polycrystalline structure with a certain roughness is formed on the surface of the rebar. The passive film is mainly composed of Fe oxides and hydroxides, and there are also oxides of Nb, Mn, Si and Cr. The existence of these oxides builds a dense and stable passive film. The passive film is basically stable at 7d, but the early growth of the passive film at higher alkalinity show instability. After 10 days of passivation, with the decrease of pH, the passive film gradually densifies, the pitting potential increased by about 0.03–0.14 V, the carrier density decreased by 30% on average, the phase angle increased slightly, and the ratios of Fe2+/Fe3+ and O2−/OH− increased, resulting in a passive film thickness of 6.2 nm.

Passive behavior of TNB intermetallic and Inconel 625 in electrochemical machining

The TNB alloy, a novel lightweight material, shows great potential for application in crucial aero-engine parts. This paper reveals the passive behavior of TNB alloy in electrochemical machining (ECM), Inconel 625 alloy was used for comparison. The polarization curve shows that TNB and Inconel 625 alloys have obvious passivation phenomenon at the passivation potential. Research reveals that the passive film structure of TNB alloy comprises a compact layer (about 7 nm) and a loose layer (about 13 nm), with significantly higher corrosion resistance in the compact layer compared to the loose layer. In contrast, the passive film structure of Inconel 625 alloy is a single layer with a thickness of approximately 11 nm. It was also found that the passive film composition for TNB alloy is TiO2, Al2O3, and Nb2O5. The composition of passive film for Inconel 625 alloy is NiO, Ni(OH)2, Cr2O3, MoO3, Nb2O5, FeO, and Fe2O3, and the content of Ni and Cr is high. TNB alloys exhibit uneven and loose lamellar morphology at low current densities, but can reach Ra 0.15 μm at greater than 15 A/cm2. There are always some disordered carbides rich in Nb and Mo on the surface of Inconel 625 alloy. Quantitative models were developed for both alloys to describe their electrochemical dissolution behavior.

Electrode reactions on the aluminum electrode in 1-butyl-3-methylimidazolium chloride chloroaluminate ionic liquid: A comprehensive study

Mechanisms of Al electrochemical deposition/dissolution in acidic AlCl3–1-butyl-3-methylimidazolium chloride (BMImCl) ionic liquids are studied. Stationary polarization curves (SPCs) are obtained in the anodic range of potentials. The anodic SPCs are characteristic of electrode processes, which are complicated by passivation phenomena. The peaks intensity of AlCl4−, Al2Cl7− ions were obtained by in-situ Raman spectroscopy during the aluminum electrode polarization and correlated with the behavior of the SPCs. Based on the results obtained, a mechanism of electrochemical oxidation of aluminum in AlCl3–BMImCl IL is proposed. According to the mechanism in question, the anodic process is complicated by the presence of a following chemical reaction involving AlCl3. Chronopotentiometric studies were carried out to determine diffusion coefficients of Al2Cl7− anion, which are unaffected by the change in the molar ratio of AlCl3 to BMImCl (N). The activation energy (Ea) for the Al2Cl7− diffusion coefficient is independent of N and equals 14.5 ± 0.4 kJ mol−1. Exchange current density (i0) at the Al | AlCl3–BMImCl interface was determined using impedance spectroscopy for the compositions with 1.1 ≤ N ≤ 2.0 at temperatures from 303 to 386 K. The i0 increases from 0.54 ± 0.13 to 2.73 ± 0.22 mA cm−2 with the concentration of the electrochemically active Al2Cl7− anion in the concentration range indicated above at 303 K. The data on i0 is used to calculate the transfer coefficient of cathodic reaction (α = 0.18 ± 0.02), the electrochemical reaction rate constant (ks= (1.1 ± 0.3)∙10−6 cm s−1 (at T = 303 K)) and the Ea for the ks (Eaks = 36.5 ± 0.9 kJ mol−1), which do not depend on the IL composition.

HepG2 cells undergo regulatory volume decrease by mechanically induced efflux of water and solutes.

This study challenges the conventional belief that animal cell membranes lack a significant hydrostatic gradient, particularly under anisotonic conditions, as demonstrated in the human hepatoma cell line HepG2. The Boyle van't Hoff (BvH) relation describes volumetric equilibration to anisotonic conditions for many cells. However, the BvH relation is simple and does not include many cellular components such as the cytoskeleton and actin cortex, mechanosensitive channels, and ion pumps. Here we present alternative models that account for mechanical resistance to volumetric expansion, solute leakage, and active ion pumping. We found the BvH relation works well to describe hypertonic volume equilibration but not hypotonic volume equilibration. After anisotonic exposure and return isotonic conditions cell volumes were smaller than their initial isotonic volume, indicating solutes had leaked out of the cell during swelling. Finally, we observed HepG2 cells undergo regulatory volume decrease at both 20°C and 4°C, indicating regulatory volume decrease to be a relatively passive phenomenon and not driven by ion pumps. We determined the turgor-leak model, which accounts for mechanical resistance and solute leakage, best fits the observations found in the suite of experiments performed, while other models were rejected.

Advances in Electrocatalyst Design and Mechanism for Sulfide Oxidation Reaction in Hydrogen Sulfide Splitting

AbstractSulfide oxidation reaction (SOR) is a semi‐reaction for the electrochemical decomposition of hydrogen sulfide. Combining SOR with the hydrogen evolution reaction (HER) allows for the simultaneous splitting of hydrogen sulfide (H2S) to produce green hydrogen, reducing energy input and environmental pollution. However, the phenomenon of sulfur passivation on the anode leads to catalyst deactivation, posing a bottleneck in developing efficient SOR. Electrocatalysts with decent performance and sulfur‐tolerance play a central role in the application of SOR. Here, recent progress on electrocatalysis mechanisms and catalyst design strategies of SOR are summarized. A summary of recent progress is made in materials such as alloys, metal oxides, metal sulfides, metal selenides, and heterostructures as SOR catalysts. Additionally, some valuable design and modulation strategies are highlighted and included. Finally, this review offers an outlook on the future directions in this emerging field.

Opportunities of building tall and green – an overview from a European perspective

The purpose of the article is to answer the question of whether a tall building, throughout its entire life cycle, can be sustainable. A literature review and online searches were conducted in order to gather data on the impact of environmental trends on chosen aspects of tall European building design. The conducted analyses confirm the hypothesis that the European approach considers sustainable aspects and can be the basis for general guidelines for the construction of green tall buildings, ensuring that the tall building’s location, floor areas and heights are functionally justified. Despite the demanding climate conditions, high-rise buildings are designed using bioclimatic solutions and take the use of passive phenomena and a reduction in the operating time of mechanical systems into account. The necessary technical infrastructure uses highly efficient, energy-saving equipment and solutions. Obtaining energy from renewable sources is present in architectural solutions but not very popular – these technologies are still growing and gaining importance.

Relationships between trauma types and psychotic symptoms: A network analysis of patients with psychotic disorders in a large, multi-country study in East Africa

BackgroundThe link between trauma exposure and psychotic disorders is well-established. Further, specific types of trauma may be associated with specific psychotic symptoms. Network analysis is an approach that can advance our understanding of the associations across trauma types and psychotic symptoms. MethodsWe conducted a network analysis with data from 16,628 adult participants (mean age [standard deviation] = 36.3 years [11.5]; 55.8% males) with psychotic disorders in East Africa recruited between 2018 and 2023. We used the Life Events Checklist and the Mini International Neuropsychiatric Interview to determine whether specific trauma types experienced over the life course and specific psychotic symptoms were connected. We used an Ising model to estimate the network connections and bridge centrality statistics to identify nodes that may influence trauma types and psychotic symptoms. ResultsThe trauma type “exposure to a war zone” had the highest bridge strength, betweenness, and closeness. The psychotic symptom “odd or unusual beliefs” had the second highest bridge strength. Exposure to a war zone was directly connected to visual hallucinations, odd or unusual beliefs, passivity phenomena, and disorganized speech. Odd or unusual beliefs were directly connected to transportation accidents, physical assault, war, and witnessing sudden accidental death. ConclusionSpecific trauma types and psychotic symptoms may interact bidirectionally. Screening for psychotic symptoms in patients with war-related trauma and evaluating lifetime trauma in patients with odd or unusual beliefs in clinical care may be considered points of intervention to limit stimulating additional psychotic symptoms and trauma exposure. This work reaffirms the importance of trauma-informed care for patients with psychotic disorders.

Research on N-type silicon crystal processing by liquid-immersion wire electrical discharge machining

Passivation at the input end of N-type silicon crystals leads to a decrease in the efficiency of wire electrical discharge machining (WEDM). In response to this problem, this paper proposes a method for the liquid-immersion WEDM of N-type silicon crystals. An equivalent circuit model for the WEDM of N-type silicon crystals was established, the volt-ampere characteristics of N-type silicon crystals immersed in different liquids at the incoming end were studied, and an experimental platform for the liquid-immersion WEDM of N-type silicon crystals was established. The experimental results demonstrate that immersion in deionized water can effectively suppress the passivation phenomenon at the input end of N-type silicon crystals, thus improving the chip removal conditions between electrodes. Compared to open-loop control machining, the machining efficiency was found to increase by 42.7 % and the surface roughness was decreased by 32.8 %. After continuous machining for 1 h, the current in the machining circuit did not significantly decrease, and the machining efficiency remained unchanged.

Editors' Choice—Improving Quality of EDMed Micro-Holes on Titanium via In Situ Electrochemical Post-processing: A Transient Simulation and Experimental Study

Electrical discharge micromachining (EDM) poses challenges to the fatigue-life performance of machined surfaces due to thermal damage, including recast layers, heat-affected zones, residual stress, micro-cracks, and pores. Existing literature proposes various ex situ post-processing techniques to mitigate these effects, albeit requiring separate facilities, leading to increased time and costs. This research involves an in situ sequential electrochemical post-processing (ECPP) technique to enhance the quality of EDMed micro-holes on titanium. The study develops an understanding of the evolution of overcutting during ECPP, conducting unique experiments that involve adjusting the initial radial interelectrode gap (utilizing in situ wire-electrical discharge grinding) and applied voltage. Additionally, an experimentally validated transient finite element method (FEM) model is developed, incorporating the passive film formation phenomenon for improved accuracy. Compared to EDM alone, the sequential EDM-ECPP approach produced micro-holes with superior surface integrity and form accuracy, completely eliminating thermal damage. Notably, surface roughness (Sa) was reduced by 80% after the ECPP. Increasing the voltage from 8 to 16 V or decreasing the gap from 60 to 20 μm rendered a larger overcut. This research’s novelty lies in using a two-phase dielectric (water-air), effectively addressing dielectric and electrolyte cross-contamination issues, rendering it suitable for commercial applications.

ZTA/high Ni–Cr alloy steel composites prepared by liquid phase sintering

The interfacial bonding, wear resistance, corrosion resistance and high temperature oxidation resistance of ZTA/high Ni–Cr alloy steel composites prepared by liquid phase sintering were investigated. The results showed that the ZTA particles bonded well with high Ni–Cr alloy steel matrix and produced transition new phases, including (Al, Cr)2O3, Al60Mn11Ni4, Mn2SiO4, MnCr2O4, (Mn, Fe)2SiO4 and MnSiO3. With the addition of ZTA particles, the wear resistance of the composites was reduced substantially. When the ZTA content is 40 vol%, the wear resistance is two times of the matrix, which is better than that of the Cr16 material. The small content of ZTA particles added can enhance the corrosion resistance of the composites. When ZTA was in small amounts, there was passivation of the samples and the corrosion resistance increased. When the content of ZTA reaches 30 vol%, the passivation phenomenon disappears. The corrosion resistance of the composites is much higher than that of the Cr16 material. The composites have good resistance to high temperature oxidation at temperatures below 700 °C. Industrial testing of plate hammers was carried out on a corrosive slag machine at a high temperature of 700 °C. The results show that the ZTA/high Ni–Cr alloy steel composite has twice the service life of the Cr26 material.

Characterization of solar cell passivating contacts using time-of-flight elastic recoil detection analysis

The unambiguous detection of hydrogen in solar cell contact structures is critical to understanding passivation and degradation phenomena. Deuterium is often used to depict the distribution of hydrogen more clearly. However, experimental noise and artifacts can hinder the clear identification of species. This work provides a report of time-of-flight elastic recoil detection (ToF-ERD) analysis to identify H/D contents in a thin poly-Si/SiOx passivating contact. The structure contained a 1.3 nm interfacial SiOx and an n+ doped poly-Si layer with a partly deuterated SiNx coating. The samples were annealed to release H/D, and ToF-ERD was used to detect H/D in monatomic, singly charged forms, without the detection artifacts associated with conventional secondary ion mass spectroscopy. Chlorine ions were used to recoil surface species, which were analyzed to clearly and unambiguously resolve H and D. Depth profiles for the recoiled Si, N, O, D, and H atoms were calculated from the energy and velocity information registered after scattering events, which enabled the analysis of the structure of the multilayer stack. Even though the surface roughness and experimental limitations cause visible broadening of the profiles, which can hinder clear detection at the interfacial oxide, the ability to resolve hydrogen-related species makes ToF-ERD a significant and promising tool for studying the role of hydrogen in the performance and degradation of solar cell passivating contacts.

Passivation bypassed Zero valent Iron based heterostructures for effective removal of persistent antibiotics by solar driven photo-Fenton process

The natural passivation phenomena in nano zerovalent iron (nZVI) through formation of surface oxide layer is a bottleneck for exploring the complete potential of the material. This problem is addressed by the in-situ synthesis of nZVI/Cu bimetallic heterostructure and exploring its improved potential towards solar-driven photodegradation of persistent antibiotics and their mixture in contaminated water. Effect of passivation bypassing by Cu0 on the stability of nZVI as a photo-Fenton candidate is scrutinized through aging of the materials and their effect on degradation performance. Post-aging studies reveal a higher performance of nZVI/Cu as compared to bare nZVI. A systematic comparative study of photo-Fenton activity for nZVI and nZVI/Cu is estimated through degradation of toxic organic pollutants such as Tetracycline (TET) and Ciprofloxacin (CIP) and also a mixture of both antibiotics using High performance Liquid Chromatography (HPLC). The degradation efficiencies achieved with nZVI/Cu for TET and CIP were 99.99% and 98.59% with rate constant of 0.0631 min−1 and 0.032 min−1 respectively. Furthermore, nZVI/Cu showed a removal efficiency of 99.34% and 99.9% for TET and CIP in antibiotic mixture. Hydroxyl radicals are found to be the prominent active species from radical trapping experiments. The degradation pathway is traced with LC-MS/MS analysis to identify the intermediates and byproducts formed during degradation process. The reusability of nZVI/Cu catalyst is evaluated with five successive cycles of CIP and TET degradation. The inherent magnetic property of nZVI/Cu sample is employed for the effortless retrieval of catalyst. Finally, a plausible explanation for the photo-Fenton degradation mechanism of nZVI/Cu for the antibiotics is put forward.

CO2 reduction employing MgH2 for CH4–H2 mixtures production through mechano-chemical processes

The CO2 methanation employing MgH2 as a source of hydrogen is investigated via mechano-chemical processes through ball milling at room temperature under different experimental conditions such as the presence/absence of catalyst, the milling duration, the molar ratio between the hydride and CO2 and the pre-milling of Ni–MgH2 mixture. The positive effect of Ni addition is demonstrated. After 5h of milling under CO2, the absence of catalyst causes the CH4 yield to drop from 70.0 to 59.0%, from 73.0 to 33.5% and from 54.0 to 40.1%, considering molar ratios of 4:1, 3:1 and 2:1, respectively. The pre-milling of nickel-catalyzed system or the addition of CNTs do not provide significant improvements. This investigation shows that similar methane yields to those obtained by thermo-chemical methods can be achieved, but involving shorter times (5 h versus 24 h) and lower temperatures (room temperature versus 400 °C). The ball collisions during milling allow overcoming passivation phenomena of MgH2 and Mg, promoting the methanation process but with lower selectivity as contamination with Fe from the milling jar provides a catalytic alternative route for the generation of C2–C3 hydrocarbons.

EECO: An AI-Based Algorithm for Energy-Efficient Comfort Optimisation

Environmental comfort takes a central role in the well-being and health of people. In modern industrial, commercial, and residential buildings, passive energy sources (such as solar irradiance and heat exchangers) and heating, ventilation, and air conditioning (HVAC) systems are usually employed to achieve the required comfort. While passive strategies can effectively enhance the livability of indoor spaces with limited or no energy cost, active strategies based on HVAC machines are often preferred to have direct control over the environment. Commonly, the working parameters of such machines are manually tuned to a fixed set point during working hours or throughout the whole day, leading to inefficiencies in terms of comfort and energy consumption. Albeit effective, previous works that tackle the comfort–energy tradeoff are tailored to the specific environment under study (in terms of geometry, characteristics of the building, etc.) and thus cannot be applied on a large industrial scale. We address the problem from a different angle and propose an adaptive and practical solution for comfort optimisation. It does not require the intervention of expert personnel or any customisations around the environment while it implicitly analyses the influence of different agents (e.g., passive phenomena) on the monitored parameters. A convolutional neural network (CNN) predicts the long-term impact on thermal comfort and energy consumption of a range of possible actuation strategies for the HVAC system. The decision on the best HVAC settings is taken by choosing the combination of ON/OFF and set point (SP), which optimises thermal comfort and, at the same time, minimises energy consumption. We validate our solution in a real-world scenario and through software simulations, providing a performance comparison against the fixed set point strategy and a greedy approach. The evaluation results show that our solution achieves the desired thermal comfort while reducing the energy footprint by up to approximately 16% in a real environment.

Facet-Dependent Passivation for Efficient Perovskite Solar Cells.

Understanding the interplay between the surface structure and the passivation materials and their effects associated with surface structure modification is of fundamental importance; however, it remains an unsolved problem in the perovskite passivation field. Here, we report a surface passivation principle for efficient perovskite solar cells via a facet-dependent passivation phenomenon. The passivation process selectively occurs on facets, which is observed with various post-treatment materials with different functionality, and the atomic arrangements of the facets determine the alignments of the passivation layers. The profound understanding of facet-dependent passivation leads to the finding of 2-amidinopyridine hydroiodide as the material for a uniform and effective passivation on both (100) and (111) facets. Consequently, we achieved perovskite solar cells with an efficiency of 25.10% and enhanced stability. The concept of facet-dependent passivation can provide an important clue on unidentified passivation principles for perovskite materials and a novel means to enhance the performance and stability of perovskite-based devices.

Passivation phenomenon and variable properties of ytterbium in different Lewis acid AlCl3-NaCl melts

To further explore the application of the low-temperature molten salt in processing heavy rare earths, the properties of ytterbium in AlCl3-NaCl melts have been investigated. In this melt, YbCl2 powder products are prepared by electrolysis based on the dissolution reaction of Yb metal. The properties of Yb(II) in AlCl3-NaCl melts have also been studied in detail. In-situ UV–VIS absorption spectroscopy demonstrates that the coordination of Yb(II) changes in AlCl3-NaCl melts with different Lewis acidity, leading to variations in its diffusion ability. In addition, the conversion of Yb(II)/Yb(III) shows typical soluble-soluble reversible electrochemical behavior in strongly acidic AlCl3-NaCl. However, the electrochemical behavior of Yb(II) on inert electrodes becomes complicated when the amount of AlCl3 in AlCl3-NaCl melts less than 52 mol%. This change is attributed to the formation of a YbCl3 passivation film on the inert electrode during the electro-oxidation of Yb(II). Soaking the passivated electrode in the melt can alleviate the passivation. Understanding the electrochemical and spectroscopic properties of ytterbium in AlCl3-NaCl melts paves the way for its subsequent applications.

Mad Pride and the Creation of Culture

AbstractAmong the different approaches in mental health activism, there is an ongoing concern with the concepts and meanings that should be brought to bear upon mental health phenomena. Aspects of Mad Pride activism resist the medicalisation of madness, and seek to introduce new, non-pathologizing narratives of psychological, emotional, and experiential states. This essay proposes a view of Mad Pride activism as engaged in no less than the creation of a new culture of madness. The revisioning and revaluing of madness requires transformations in the basic concepts constitutive of current mental health narratives. This process is illustrated with the concept of self and its relation to passivity phenomena (thought insertion). The essay concludes with some of the challenges facing Mad Pride's ambition to enrich the cultural repertoire.

Experimental demonstration of passive microwave pulse amplification via temporal Talbot effect

The temporal Talbot effect is a passive phenomenon that occurs when a periodic signal propagates through a dispersive medium with a quadratic phase response that modulates the output pulse repetition rate based on the input period. As previously proposed, this effect enables innovative applications such as passive amplification. However, its observation in the microwave regime has been impractical due to the requirement for controlled propagation through a highly dispersive waveguide. To overcome this challenge, we employed an ultra-wide band linearly chirped Bragg grating within a standard microwave X-Band waveguide. By utilizing backwards Talbot array illuminators aided by particle swarm optimization, we achieved passive amplification with a gain of 3.45 dB and 4.03 dB for gaussian and raised cosine pulses, respectively. Furthermore, we numerically verified that with higher quality substrates this gain can be theoretically increased to over 8 dB. Our work paves the way for numerous applications of the Talbot effect in the microwave regime, such as temporal cloaking, sub-noise microwave signal detection, microwave pulse shaping, and microwave noise reduction.

Visualization of electrographic flow fields of increasing complexity and detection of simulated sources during spontaneously persistent AF in an animal model.

Mapping algorithms have thus far been unable to localize triggers that serve as drivers of AF, but electrographic flow (EGF) mapping provides an innovative method of estimating and visualizing in vivo, near real-time cardiac wavefront propagation. One-minute unipolar EGMs were recorded in the right atrium (RA) from a 64-electrode basket catheter to generate EGF maps during atrial rhythms of increasing complexity. They were obtained from 3 normal, animals in sinus rhythm (SR) and from 6 animals in which persistent AF which was induced by rapid atrial pacing. Concurrent EGF maps and high-resolution bipolar EGMs at the location of all EGF-identified sources were acquired. Pacing was subsequently conducted to create focal drivers of AF, and the accuracy of source detection at the pacing site was assessed during subthreshold, threshold and high-output pacing in the ipsilateral or contralateral atria (n = 78). EGF recordings showed strong coherent flow emanating from the sinus node in SR that changed direction during pacing and were blocked by ablation lesions. Additional passive rotational phenomena and lower activity sources were visualized in atrial flutter (AFL) and AF. During the AF recordings, source activity was not found to be correlated to dominant frequency or f wave amplitude observed in concurrently recorded EGMs. While pacing in AF, subthreshold pacing did not affect map properties but pacing at or above threshold created active sources that could be accurately localized without any spurious detection in 95% of cases of ipsilateral mapping when the basket covered the pacing source. EGF mapping can be used to visualize flow patterns and accurately identify sources of AF in an animal model. Source activity was not correlated to spectral properties of f-waves in concurrently obtained EGMs. The locations of sources could be pinpointed with high precision, suggesting that they may serve as prime targets for focal ablations.

Modeling electrochemical oxide film growth—passive and transpassive behavior of iron electrodes in halide-free solution

The phenomenon of passivity is crucial for many areas of our technological and metal-based civilization. Nevertheless, the mechanisms leading to passivity are still under investigation and not fully understood. Modeling passive film growth can bring insights into these processes, which are experimentally hard or impossible to access. Therefore, this paper presents a comprehensive model which can describe oxide film growth and dissolution under an external potential for various metal oxides. The simulation gives insights into the defect concentrations and electric field during passive film growth and film dissolution and delivers an anodic transpassive dissolution mechanism. The simulation is compared to experiments derived from the oxidation of iron electrodes and shows very good agreement. The addition of a transpassive dissolution mechanism to oxide film models is the next step toward model-based corrosion prediction.