Synthesis and corrosion inhibition evaluation of a new schiff base hydrazone for mild steel corrosion in HCl medium: electrochemical,DFT, and molecular dynamics simulations studies

Abstract

The development of cost-effective, sustainable, eco-friendly and efficient compounds is a renovated science and a demanding assignment for today’s chemists and technology specialists. In this context, the anticorrosion effect of a new Schiff base hydrazone, namely (E)-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)benzylidiene)hydrazine-1-carboxamide (MPAH) against the mild steel (MS) surface in 1.0?M HCl has been analyzed utilizing experimental methods, thermodynamic characterizations, and computational studies. MPAH has proven to be an effective inhibitor in 1.0?M HCl solution. Its inhibition performance improved by raising the concentration of the compound to an optimal concentration of 5?×?10^?3 M, and 97% efficiency was achieved at 303?K. Inhibitor adsorption on the MS has been explicated with both physical and chemical interactions. The adsorption was in accordance with the isotherm of Langmuir. The impact of MPAH on the surface of MS had been confirmed utilizing SEM/EDX, electrochemical impedance spectroscopy (EIS), gravimetric measurements (WL), and potentiodynamic polarization (PDP). The adsorption of the studied compound on the MS surface has also been investigated by DFT and the molecular dynamics (MD) simulations.     

Probing Site Symmetry Around Eu3+ in Nanocrystalline ThO2 Using Time Resolved Emission Spectroscopy

ThO₂:Eu³⁺ nanoparticles were synthesized at 300°C by combustion route using urea as a fuel and characterized by thermogravimetric/differential thermal analysis, X‐ray diffraction, transmission electron microscopy, and photoluminescence techniques. To investigate the effect of annealing temperature, as synthesized powder were heated further at 500°C, 700°C, and 900°C. It was observed that extent of asymmetry around Eu³⁺ at 700°C/900°C is very high as compared to as‐prepared or 500°C annealed sample. Based on the time resolved emission spectroscopic investigations, it was inferred that two different types of Eu³⁺ ions were present in the ThO₂ nanoparticles. In ThO₂ structure, Eu³⁺ ions occupy two sites; cubic (O_h) and noncubic (<C_2v) as can be confirmed from our emission studies. Short‐lived species T₁ (~1.3–3.4 ms) predominates at higher annealing temperature arises because of Eu³⁺ ions occupying noncubic (<C_2v) sites without inversion symmetry, whereas long‐lived species T₂ (~4.6–6.6 ms) can be ascribed to Eu³⁺ ions occupying cubic sites (O_h) with inversion symmetry.     

An experimental study on on-line optimizing control of free radical bulk polymerization in a rheometer-reactor assembly under conditions of power failure

An experimental study on the on-line optimizing control of a sample free radical bulk polymerization system, namely, methyl methacrylate (MMA), is carried out in a rheometer-reactor assembly. Two initiator loadings and three cases involving external disturbances (power failure) are studied. The disturbances are assumed to be of two kinds: one that leads to a sudden increase in the temperature of the reaction mass (cooling water pump failure) over the planned temperature history, T(t), and one leading to a sudden drop in the temperature (heater failure). The temperature and the viscosity, η, histories are used to describe the ‘state’ (conversion, x_m, and weight-average molecular weight, M_w) of the polymerizing mass. The polymerization is first carried out under an off-line computed optimal temperature history, T_op(t), obtained using the adapted jumping gene version of the elitist genetic algorithm (GA-II-aJG). A planned disturbance is introduced after the start of polymerization and continues for a pre-specified duration. A new optimal temperature history, T_reop(t), is calculated on-line (in about 3 min of real time) using GA-II-aJG. This is implemented as soon as the disturbance is rectified. Experimental values of x_m(t), M_w(t) and η(t) are also measured. These are observed to be in good agreement with model predictions for all the cases. It is found that the information on the viscosity of the reaction mass can be used effectively for on-line optimizing control. This can help ‘save’ the batch (give a product having the desired values of the average molecular weights) optimally, in as short a reaction time as possible. The effect of re-tuning of the model parameters using experimental data on the temperature, T_exp(t), and the viscosity, η(t), is also demonstrated.     

Structural,optical, and Raman studies of Gd doped sodium bismuth titanate

The effects of gadolinium (Gd) on lead free sodium bismuth titanate (Na_0.5Bi_0.5TiO₃, NBT) ceramics are investigated. X-ray diffraction (XRD) studies indicate that perovskite phase (rhombohedral, R3c) is formed for all Gd doped NBT (Gd_x:NBT) compositions (x?=?0, 0.02, 0.04, 0.06, 0.08). XRD peak shifts to the higher angles for all compositions except for x?=?0.08. Amphoteric nature of Gd in NBT sites are observed i.e., it occupies Bi-site up to x?=?0.06 and then distributes to Ti-site. Octahedral distortion (c/a) increases in the range 0.02?≤?x?≤?0.06 and then decreases. Raman spectra suggest that the introduction of Gd⁺³ ion induces structural changes without disturbing the long range order. The material can be readily excited using UV (360?nm) and shows emission peaks at ~592?nm and 687?nm. Optical property evaluation indicates that the lowest band gap (E_g = 2.78?eV) is observed at x?=?0.08. When x?>?0.04, the photoluminescence (PL) intensity decreases indicating the onset of concentration quenching. The critical energy distance (found to be 14?Å) and Dexter's theory based analysis indicate that concentration quenching is attributable to multipole-multipole (specifically dipole-dipole) interactions in the system. Commission International de Eclairage (CIE) chromatic color coordinates are reported for all doped systems; the observed patterns mirror PL analysis results. For instance, PL intensity shrinks beyond 4?at%; this corresponds to a regression in the CIE trajectory with respect to concentration.