Experimental, quantum chemical calculations and molecular dynamics (MD) simulation studies of methionine and valine as corrosion inhibitors on carbon steel in phase change materials (PCMs) solution

Insight into the Corrosion Inhibition Mechanism of Sodium Silicate on the Magnesium Alloy Surface: Experimental and Theoretical Calculations

The corrosion inhibition mechanism of sodium silicate (SS) for WE43 magnesium alloy in NaCl solution was investigated by in situ observation, electron probe microanalysis (EPMA), electrochemical test, and theoretical calculations. In situ observation showed that local corrosion was markedly inhibited after the addition of the SS inhibitor. Electrochemical data revealed that a protective layer was formed on the metal/solution interface and an optimum inhibition efficiency of 98.3% in the case of 2.5 g/L SS. A uniform magnesium silicate layer with a thickness of ∼2 μm formed on the uncorroded area was confirmed. Quantum chemical calculations revealed that SiO32- could absorb on the MgO (1 0 0) surface in a parallel orientation through the coordinate bonds between the O and Mg atoms. The distances of Mg-O bonds are 2.052 and 2.249 Å, suggesting that they are coordinated. The adsorption/interaction mechanisms of SiO32- were also analyzed through charge density distribution and atomic densities. Molecular dynamics simulations further confirmed that a uniform SiO32- layer was absorbed on the MgO surface. In the local corroded area, free SiO32- would react with Mg2+ and OH- produced by corrosion to form the insoluble magnesium silicate compound, which hindered the spread of corrosion.

Experimental and Computational Study on Inhibitory Effect and Adsorption Properties of N-Acetylcysteine Amino Acid in Acid Environment

Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were applied to study the inhibitory effect of N-acetylcysteine (NAC) on corrosion inhibition of carbon steel in hydrochloric acid solution. N-acetylcysteine influenced the iron dissolution to a greater extent than the hydrogen evolution reaction acting as a mixed inhibitor, predominantly anodic. The charge transfer resistance (Rct) gradually increased with the inhibitor concentration. From both methods, the inhibition efficiency (IE) reached a value of 89 ± 1% and NAC adsorption followed the Temkin isotherm. The value of adsorption Gibbs energy (ΔGadso), around -35 kJ mol-1, indicated a spontaneous adsorption and mixed action mechanism, with NAC chemical adsorption prevailing over physical one. New data will be reported by the computational study, that was performed using the density functional theory (DFT) method in aqueous phase. Quantum chemical descriptors were determined by B3LYP theory level with 6-31G+(d) basis set. Metropolis Monte Carlo atomistic simulation was used to reveal the adsorption configuration and interactions between acetylcysteine molecules and the carbon steel surface. Theoretical results were consistent with the experimental data, showing that the inhibitor action mechanism consisted of mainly chemisorption of its molecules on the carbon steel surface accompanied by van der Waals forces and electrostatic interactions.

Comprehensive analysis (aerobic/anaerobic, molecular recognitions, band-position and degradation-mechanism) of undoped and Co-doped anatase-brookite - An experimental/theoretical evaluation of the less-studied TiO2 mixed phase

The molecular recognition (MRec) effect is required in the initial phase of organic reactions. The second stage involves molecular-orientations and molecular-orbitals energy-levels (MOrbE). The components of a reaction must be compatible in terms MRec and MOrbE. Therefore, the comprehension of photocatalytic systems applied in wastewater treatment will be improved if the MRec effect is also considered as an important factor. The purpose of this study is to provide a comprehensive understanding of the less studied anatase-brookite mixed-phase (doped and undoped). Anatase/brookite photocatalytic systems were evaluated utilizing experimental/theoretical approaches in H₂O (aerobic/anaerobic) environments with Vis-light and the organic pollutant (OrPo) methyl orange (MO). The compatibility of MRec and MOrbE of anatase-brookite mixed-phase (with the different reactive system components) confirmed this is the optimal combination for photocatalytic application. Using the sol-gel method, AM-TiO₂NP (amorphous), TiO₂NP (crystalline), and TiO₂NP-Co0.1 at% (crystalline Co-doped) anatase-brookite mixed-phase photocatalysts were obtained. The morphology and surface were characterized using XRD, BET, SEM, HR-TEM, FT-IR and XPS. Employing UV-vis DRS and PL, photo-response and electron-hole recombination were studied. LVS and Mott-Schottky plot were employed to determine photo-electrochemical activity. The results of TiO₂NP photocatalytic degradation in both aerobic and anaerobic environments are remarkable. The results of molecular dynamics (MD) simulation and Fukui Function (FF) based on density functional theory (DFT) validate the remarkable photocatalytic MO degradation.

A structure-property study for konjac glucomannan and guar galactomannan: Selective carboxylation and scale inhibition

The effect of structural difference for konjac glucomannan (KGM) and guar galactomannan (GGM) on their physicochemical properties including selective carboxylation, biodegradation and scale inhibition was firstly investigated. Compared with GGM, KGM can be specially modified by amino acid to prepare carboxyl-functionalized polysaccharides. The structure-activity relationship explaining the difference in carboxylation activity and the anti-scaling abilities of polysaccharides and carboxylated derivatives were explored by static anti-scaling, iron oxide dispersion and biodegradation tests coupled with structural and morphological characterizations. KGM with linear structure was preferred for carboxylated modification by glutamic acid (KGMG) and aspartic acid (KGMA) while GGM with branched structure failed to accomplish that due to steric hindrance. GGM and KGM showed limited scale inhibition performance, which was probably attributed to the moderate adsorption and isolation effect of macromolecular stereoscopic structure. While KGMA and KGMG performed as effective and degradable inhibitors for CaCO₃ scale with inhibitory efficiencies > 90 %.

The Role of Some Cationic Surfactants Based on Thiazine as Corrosion Inhibitors in Petroleum Applications: Experimental and Theoretical Approach

Two cationic surfactants based on thiazine, dodecyl thiazin bromide (DTB) and hexyl thiazin bromide (HTB), were synthesized, characterized, and investigated as corrosion inhibitors for API X-65 type steel in oil wells' formation water under an H₂S environment. Various spectroscopic techniques such as FTIR and ¹H NMR were used to confirm the DTB and HTB chemical structures. The corrosion inhibition efficiency of the selected compounds was investigated using both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The innovation of the current study is the existence of a long chain in the inhibitor molecule, which leads to an increase in the performance of the surfactant as a corrosion inhibitor, due to the increase in the surface area per molecule. It was found that these surfactants act as mixed-type inhibitors, leading to suppression of both the cathodic and the anodic processes by its adsorption on the electrode surface according to the Langmuir adsorption isotherm. Carbon steel's inhibitory mechanism was studied using an analogous circuit. The scanning electron microscope technique was used as a suitable analysis tool to show the nature of the layer designed on carbon steel. Quantum chemical calculations and Monte Carlo simulation techniques were used to support the obtained experimental results. Finally, a suitable mechanism for the inhibition process was proposed and discussed.

Calcite Scale Inhibition Using Environmental-Friendly Amino Acid Inhibitors: DFT Investigation

Scale prevention is a long-term challenge. It is essential for ensuring the optimum utilization of oil and gas wells and minimizing economic losses due to disruptions in the hydrocarbon flow. Among the commonly precipitated scales is calcite, especially in oilfield production facilities. Previous studies on scale inhibitors have focused on investigating the performance of several phosphonates and carboxylates. However, the increased environmental awareness has pushed toward investigating environmental-friendly inhibitors. Research studies demonstrated the potential of using amino acids as standalone inhibitors or as inhibitor-modifying reagents. In this study, 10 amino acids for calcite inhibitors have been investigated using molecular simulations. Eco-toxicity, quantum chemical calculations, binding energy, geometrical, and charge analyses were all evaluated to gain a holistic view of the behavior and interaction of these inhibitors with the calcite {1 0 4} surface. According to the DFT simulation, alanine, aspartic acid, phenylalanine, and tyrosine amino acids have the best inhibitor features. The results revealed that the binding energies were -2.16, -1.75, -2.24, and -2.66 eV for alanine, aspartic acid, phenylalanine, and tyrosine, respectively. Therefore, this study predicted an inhibition efficiency of the order tyrosine > phenylalanine > alanine > aspartic acid. The predicted inhibition efficiency order reveals agreement with the reported experimental results. Finally, the geometrical and charge analyses illustrated that the adsorption onto calcite is physisorption in the acquired adsorption energy range.

Thermal Energy Storage Materials (TESMs)—What Does It Take to Make Them Fly?

Thermal Energy Storage Materials (TESMs) may be the missing link to the “carbon neutral future” of our dreams. TESMs already cater to many renewable heating, cooling and thermal management applications. However, many challenges remain in finding optimal TESMs for specific requirements. Here, we combine literature, a bibliometric analysis and our experiences to elaborate on the true potential of TESMs. This starts with the evolution, fundamentals, and categorization of TESMs: phase change materials (PCMs), thermochemical heat storage materials (TCMs) and sensible thermal energy storage materials (STESMs). PCMs are the most researched, followed by STESMs and TCMs. China, the European Union (EU), the USA, India and the UK lead TESM publications globally, with Spain, France, Germany, Italy and Sweden leading in the EU. Dissemination and communication gaps on TESMs appear to hinder their deployment. Salt hydrates, alkanes, fatty acids, polyols, and esters lead amongst PCMs. Salt hydrates, hydroxides, hydrides, carbonates, ammines and composites dominate TCMs. Besides water, ceramics, rocks and molten salts lead as STESMs for large-scale applications. We discuss TESMs’ trends, gaps and barriers for commercialization, plus missing links from laboratory-to-applications. In conclusion, we present research paths and tasks to make these remarkable materials fly on the market by unveiling their potential to realize a carbon neutral future.

Optoelectronic parameters of peripherally tetra-substituted copper(ii) phthalocyanines and fabrication of a photoconductive diode for various conditions

In this study, the molecular structure of 4-(4-(trifluoromethoxy)phenoxy)phthalonitrile (1) has been elucidated and its supra-molecular dynamics have been revealed by the analysis of single crystal X-ray diffraction measurements.

Synthesis of non-peripherally tetra-substituted copper(ii) phthalocyanines: characterization, optical and surface properties, fabrication and photo-electrical properties of a photosensitive diode

This study describes the synthesis and characterization of a non-peripherally tetra-substituted copper(ii) phthalocyanine bearing 4-(trifluoromethoxy)phenol groups.