The inhibition effect of ionic liquid (IL) 1-ethyl-3- methylimidazolium thiocyanate (EMIM)+(SCN)− on the corrosion of API 5L X52 steel in 0.5 M H2SO4 solution at different temperatures were studied, ...using gravimetrical, electrochemical, spectroscopic and simulation methods. The highest efficiency and the optimal concentrations were 90.1% and 75 ppm of the IL, respectively. Scanning electron microscopy characterization reveals less surface damage in the corroded samples confirming the effectiveness of the IL, while X-ray photoelectron spectroscopy analysis evidenced the formation of an interfacial protective layer, composed by the inhibitor molecules and corrosion products. Polarization measurements showed that the IL is a mixed-type inhibitor, retarding the dissolution of mild steel and hydrogen evolution reactions, enhancing its efficiency as a function of its concentration; besides a minor influence of the temperature in the inhibition efficiency is recorded by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques. A competitive chemisorption process is observed on steel obeying a Langmuir isotherm. Ultraviolet-visible spectroscopy confirmed chemical interaction between IL and metal surface. The density functional theory and molecular dynamic (MD) simulation were used to correlate with the experimental results and determine the adsorption energy of the inhibitor in different substrate's crystallographic planes. Furthermore, from the results of the interaction between the inhibitor molecules in the presence of water on the steel surface using MD on seven most compact planes of BCC system, it was capable of establishing a correlation between adsorption energies of the inhibitor and the crystallographic texture and the surface roughness of the studied steel.
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•1-Ethyl-3methylimidazolium thiocyanate is a corrosion inhibitor of the API 5L X52.•Gravimetrical, electrochemical, and spectroscopic studies confirm the efficiency.•The IL is a mixed-type inhibitor and is adsorbed by chemisorption.•Adsorption energy on different crystallographic planes was calculated by DFT and MS.•The adsorption energies of the IL and the crystallographic texture are correlated.
This paper presents insights on the thermodynamics and kinetics of the cobalt electronucleation and growth mechanisms onto glassy carbon electrode from a eutectic mixture of choline chloride and ...urea. The behavior of the current density transients can be described by a model capable of considering the cobalt three-dimensional nucleation and diffusion-controlled growth from metallic nuclei and the induction-time. Using the proposed model, typical kinetic parameters such as nucleation frequency A, number density of nuclei, N0, and diffusion coefficient, D, were determined at different temperatures and applied potentials. It was found that the residual water has some effects on the early stage of the Co electrodeposition, especially on the nucleation types. Thus, at low temperature it is predominant by progressive nucleation, while at high temperature it is governed by instantaneous nucleation mechanism. Furthermore, from the temperature-dependent relationship of the diffusion coefficient, the Gibbs free energy for cobalt nucleation in DES was able to be estimated.
•Mechanisms and kinetics of cobalt nucleation and growth from DES were investigated.•Chemical species of DES containing Co (II) were established using UV–vis spectra.•A model comprising (3D) nucleation and growth and induction-time was proposed.•Gibbs free energy for nucleation was determined through a model fitting method.
Although the prevalence of HIV among men who have sex with men (MSM) in Vietnam has been increasing in recent years, there are no estimates of the population size of MSM based on tested empirical ...methods.
This study aimed to estimate the size of the MSM population in 12 provinces in Vietnam and extrapolate from those areas to generate a national population estimate of MSM. A secondary aim of this study was to compare the feasibility of obtaining the number of users of a mobile social (chat and dating) app for MSM using 3 different approaches.
This study used the social app multiplier method to estimate the size of MSM populations in 12 provinces using the count of users on a social app popular with MSM in Vietnam as the first data source and a questionnaire propagated through the MSM community using respondent-driven sampling as the second data source. A national estimation of the MSM population is extrapolated from the results in the study provinces, and the percentage of MSM reachable through online social networks is clarified.
The highest MSM population size among the 12 provinces is estimated in Hanoi and the lowest is estimated in Binh Dinh. On average, 37% of MSM in the provinces surveyed had used the social app Jack'd in the last 30 days (95% CI 27-48). Extrapolation of the results from the study provinces with reliable estimations results in an estimated national population of 178,000 MSM (95% CI 122,000-512,000) aged 15 to 49 years in Vietnam. The percentage of MSM among adult males aged 15 to 49 years in Vietnam is 0.68% (95% CI 0.46-1.95).
This study is the first attempt to empirically estimate the population of MSM in Vietnam and highlights the feasibility of reaching a large proportion of MSM through a social app. The estimation reported in this study is within the bounds suggested by the Joint United Nations Programme on HIV/AIDS. This study provides valuable information on MSM population sizes in provinces where reliable estimates were obtained, which they can begin to work with in program planning and resource allocation.
In this paper, a novel material based on Er-Yb-Mo tri-doped HA/β-TCP phosphor for intense green up-conversion (UC) emission was successfully synthesized by solid-state reaction method. X-ray ...diffraction (XRD) measurements verified that the materials including a trace amount of HA phase has a hexagonal structure and main β-TCP phase has a rhombohedral structure, which is controlled by the doped ions. Under excitation wavelength of 976 nm laser diode, the HA/β-TCP:Er-Yb-Mo phosphor showed strong green UC emission band at 520/556 nm and weak red emission band at 656 nm which are attributed to (2H11/2, 4S3/2) - 4I15/2, 4F9/2 - 4I15/2 transition of the Er3+ ion, respectively. Remarkably, compared with the sample without Mo6+, the green emission intensities increased ∼650 times was achieved by using Er3+-Yb3+-Mo6+ doped phosphor. The high efficiency of the UC can be attributed to novel energy transfer process from |2F7/2, 3T2> state of Yb3+ - MoO42− dimer to the 4F7/2 of Er3+ ions. Moreover, the grain orientations due to the effect of Mo6+ ions doped in β-TCP phosphor could play an important role in the enhancement of UC emission intensity. These results indicate that the HA/β-TCP: Er-Yb-Mo phosphor has potential application in biological imaging and medicine.
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•Novel upconversion material (Er-Yb-Mo tri-doped HA/β-TCP phosphor) was facilely synthesized by solid-state reaction method.•The crystalline single – phase of β-TCP was achieved by doping with Mo6+ ions.•The green emission intensity of the sample doped with Mo was 650 times higher compared with the sample without Mo.•The selective green upconversion emission can be controlled by controlling the doping Mo6+ concentration in HA/β-TCP: Er3+-Yb3+.
•1-Ethyl 3-methylimidazolium thiocyanate is experimentally and theoretically evaluated as corrosion inhibitor in H2SO4 and HCl solutions.•Ethyl 3-methylimidazolium thiocyanate as inhibitor presents a ...better efficiency in H2SO4 than that in HCl solution.•The behavior of 1- ethyl 3-methylimidazolium thiocyanate in acid media follows the Langmuir´s adsorption isotherm.•Simulation of interactions between 1- ethyl 3-methylimidazolium thiocyanate and SO42− and Cl- on Fe and Fe2O3 (110) plane surfaces confirms a better adsorption behavior in H2SO4.
The corrosion inhibition behavior of 1-ethyl 3-methylimidazolium thiocyanate, (EMIM)+(SCN)− ionic liquid (IL), on API 5 L X52 steel immersed in 0.5 M H2SO4 and 0.5 M HCl aqueous solutions were studied. The kinetic corrosion parameters were determined using a gravimetrical method and electrochemical tests (polarization curves, electrochemical impedance spectroscopy). The (EMIM)+(SCN)− exhibited good inhibition efficiency, IE, (82.9% and 77.4% for H2SO4 (75 ppm) and HCl (100 ppm) solutions) properties in both solutions acting as a mixed-type inhibitor. In H2SO4 the IE increased with increasing IL concentration and temperature, while in HCl IE decreased with the temperature increase. The IL adsorption mechanism followed the Langmuir isotherm, presenting a competition between the physical and chemical interactions. Surface analysis techniques (energy dispersive spectroscopy and X-ray photoelectron spectroscopy) indicate that the inhibitor formed a protective film on the steel surface, evidencing the adsorption of the cation (EMIM)+ and the anion (SCN)− of the IL on the steel surface, which corroborates that both the (EMIM)+ and the (SCN)− of IL interact with the substrate. The evaluation of interactions of (EMIM)+(SCN)− molecules with H2SO4 and HCl in the presence of water on different surfaces of iron Fe and Fe2O3 (110) plane was performed, using molecular dynamics to determine the inhibitor adsorption energies in both acid media. The simulation results are in close agreement with the experimental observations that the inhibition efficiency is better in H2SO4 solution in comparison with that in HCl due to the higher adsorption energy values obtained in H2SO4 medium.
Two ionic liquids, 1-(2-hydroxyethyl)-3-methylimidazolium dicyanamide (HEMIM)+ (CN)- and 1,3- didecyl-2-methylimidazolium chloride (DMIM)+ (Cl)-, were evaluated as corrosion inhibitors of the API 5L ...X52 in 0.5 M HCl using electrochemical method, weight loss, and surface characterization techniques. Gravimetric tests showed that the ILs display high corrosion protection efficiency, % EI, (92 % and 97 %) with 100 and 5 ppm of (HEMIM)+ (CN)- and (DMIM)+ (Cl)-, respectively. Electrochemical tests showed that the % EI depends on the IL concentration and the temperature. The polarization studies showed that the ILs are mixed type inhibitors and the adsorption of the ILs on the API 5L X52 obeyed the Langmuir adsorption isotherm displaying chemical interaction between the steel and the IL. SEM and AFM verified a considerable reduction of the corrosion process after the addition of the ILs. Uv-vis also confirmed the interaction between ILs and steel. Theoretical quantum chemical calculation studies agree with experimental results. The adsorption energy of (DMIM)+ (Cl)- on Fe (110) surface is higher than that of (HEMIM)+ (CN)-, but both inhibitors are expected to bind strongly to the API 5L X52.
In the present work a model for the correlation between magnetocrystalline anisotropy energy and Barkhausen noise is proposed. The link between the magnetocrystalline anisotropy energy and the ...magnetic Barkhausen noise is due to the influence of the crystallographic texture on the domain nucleation process which produces the Barkhausen signal in the branch from saturation to remanence. The statistical distributions of magnetic free poles and local fields of nucleation and subsequent growth of reversed domains were obtained for a large number of grain boundaries and used to estimate the number and size of Barkhausen events at each angular position from 0 to 360° in ten degree-steps. The good agreement observed between the modeled magnetocrystalline energy and the prediction of this energy made from X-ray texture and Barkhausen noise measurements corroborates the validity of the proposed model.
The orthorhombic phases of CH3NH3PbX3 (X = Br, I) have garnered significant research interest for their potential applications in optoelectronics. This work presents our findings regarding the ...geometric, electronic, and optical properties of CH3NH3PbX3 utilizing first-principles calculations based on density functions theory (DFT), and many-body perturbation theory (MBPT). Our investigation reveals that CH3NH3PbX3 exhibits direct band gap semiconductors, low effective mass, and high carrier mobility. Furthermore, CH3NH3PbX3 processes interesting optical properties, including a low exciton energy binding, and low reflectivity/high absorption efficiency. Additionally, the identified bound exciton states manifest as bright states in both materials. More importantly, the intimate correlation between optical and electronic characteristics is convincingly established through the orbital hybridization concept. These features suggest that CH3NH3PbX3 materials hold promise as an active layer for perovskite-based solar cells.
Coastal protection, shoreline stabilization and mangrove forest restoration are pressing issues in such coastal regions worldwide as the Mekong Delta. A hollow triangle breakwater TC1 was developed ...to protect the coastline against erosion. The TC1 breakwater consists of holes arranged on the waveward and leeward sides, allowing for wave energy dissipation, water exchange, and sediment deposition to facilitate mangrove restoration. To evaluate comprehensively the working principles of the TC1, we investigate herein the wave-structure interaction under regular waves by means of an advanced computational fluid dynamics (CFD) platform, i.e. FLOW-3D. The numerical model was calibrated against experimental results with great agreement across three different water depths where the breakwater was tested. We also analyzed the velocity dynamics in the waveward and leeward sides of the breakwater and it revealed a significant difference of approximately 50% following the change in water depths from 0.66 m to 0.96 m. Furthermore, we examined the wave forces on both solid and hollow forms of TC1 structures, the wave forces on a hollow form were found to decrease by 20–30% in comparison with the forces on a solid form. In addition, the effect of liquid characteristics, i.e., density, viscosity and temperature showed slightly impact on wave transmission coefficients through the breakwater by 0.4–0.7 %.
•Investigation of wave transmission coefficients of the hollow triangle breakwater (TC1) under variable wave conditions.•Investigating the hydrodynamics and changes in kinetic energy dissipation through TC1.•Quantification of the difference in wave forces on the hollow and solid forms of TC1.•Quantification of the impact of liquid characteristics on the wave transmission coefficients through TC1.
In this study, the geometric, mechanical, electronic, and optical properties of two-dimensional XC (X = Si, Ge, Sn) monolayers are investigated using first-principles calculation based on density ...functional theory (DFT) and the many-body perturbation calculation (GW-BSE). The physical and chemical characteristics, along with orbital hybridizations in all Si–C, Ge–C, and Sn–C chemical bonds are presented, such as the structurally stable, the elastic anisotropy, a sizable electronic band gap, sp2 orbital hybridizations, the identification of the type of chemical bonds through the band-decomposed charge densities, and appearance of the van Hove singularities in the density of states. Furthermore, the effects of electron-hole interactions in optical responses are achieved through the imaginary part, the real part of dielectric functions, and energy loss functions. More importantly, the direct connection between the initial and final electronic states associated with each optical excitation peak has been accomplished. The distinct qualities exhibited by monolayers of group IV-IV compounds make them well-suited for high-performance applications in nanoelectronics and optics.
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