scholarly journals Mannich Base as an Efficient Corrosion Inhibitor of AA6061 in 0.5 M HCl: Electrochemical, Surface Morphological and Theoretical Investigations

2021 ◽  
Author(s):  
K. Maithili ◽  
Prakasha Shetty ◽  
P. Preethi Kumari ◽  
Sneha Kagatikar
Keyword(s):  
Density Functional ◽  
Mannich Base ◽  
Electrochemical Impedance ◽  
Alloy Surface ◽  
Functional Theory ◽  
Atomic Force ◽  
Theoretical Investigations ◽  
Langmuir Isotherm Model ◽  
Inhibition Performance ◽  
Good Agreement

AbstractThe inhibition action of a Mannich base, N-(1- morpholinobenzyl) semicarbazide (MBS), was examined on AA6061 corrosion in 0.5 M HCl solution at varied temperatures (303 to 323 K). The testing was performed by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The inhibition performance of MBS was improved with an increment in its concentration (0.01–2.56 mM) and temperature rise (303 to 323 K). MBS showed a mixed inhibitor behavior at all concentrations and temperatures range studied. MBS displayed the highest inhibition efficiency of 98% at 2.56 mM and 323 K. Inhibitor followed mixed adsorption on the alloy surface and obeyed the Langmuir isotherm model. The results obtained from the EIS were in good agreement with that of the PDP results. An appropriate mechanism was proposed for the corrosion inhibition of AA6061. Inhibitor molecules adsorption on alloy surface was confirmed by surface morphology testing by a scanning electron microscope (SEM) and atomic force microscope (AFM). Theoretical studies using density-functional theory (DFT) confirmed the experimental results.

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

scholarly journals Solid-State and Theoretical Investigations of Some Banister-Type Macrocycles with 2,2’-Aldoxime-1,1’-Biphenyl Units

2021 ◽  
Vol 9 ◽  
Author(s):  
Ioan Stroia ◽  
Ionuţ -Tudor Moraru ◽  
Maria Miclăuş ◽  
Ion Grosu ◽  
Claudia Lar ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Density Functional ◽  
Alkali Metal Ions ◽  
Functional Theory ◽  
State Data ◽  
Supramolecular Associations ◽  
Theoretical Investigations ◽  
The Stability ◽  
Good Agreement

In the context of helical chirality, bridging of biphenyl units leads to banister-type compounds and the stability of the resulted atropisomers may increase dramatically if suitable changes are performed in the linker unit that coils around the biphenyl moiety. A rigorous density functional theory (DFT) study was conducted for macrocycles containing rigid oxime ether segments connected to the biphenyl backbone in order to determine how the rotation barriers are influenced by the presence of either a flexible oligoethyleneoxide or a more rigid m–xylylene component in the macrocycle. The calculated values for the racemization barrier were in good agreement with those obtained experimentally and confirm the benefit of introducing a more rigid unit in the macrocycle on the stability of atropisomers. Solid-state data were obtained and computed data were used to assess the contribution brought by supramolecular associations observed in the lattice to the stabilization of the crystal structure. Beside introducing rigidity in the linker, complexation of flexible macrocycles with alkali metal ions is also contributing to the stability of atropisomers, leading to values for the racemization barrier matching that of the rigid macrocycle. Using diethylammonium cation as guest for the macrocycle, a spectacular increase in the barrier to rotation was observed for the resulted pseudo[2]rotaxane.

scholarly journals Electrochemical and Surface Analytical Study on the Role of Poly(butylene-succinate)-l-proline during Corrosion of Mild Steel in 1 M HCl

Chemistry ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 900-917
Author(s):  
George M. Tsoeunyane ◽  
Elizabeth M. Makhatha
Keyword(s):  
Mild Steel ◽  
Corrosion Inhibition ◽  
Electrochemical Impedance ◽  
Inhibition Mechanism ◽  
Butylene Succinate ◽  
Atomic Force ◽  
Langmuir Isotherm Model ◽  
Corrosion Inhibition Efficiency ◽  
Inhibition Performance

The synthesis and corrosion inhibition performance of poly(butylene-succinate)-L-proline (PBSLP) prepared by solution polymerization are reported. PBSLP was characterized by FTIR, XRD, and SEM/energy dispersive X-ray (EDX). PBSLP was used to protect mild steel in 1 M hydrochloric acid. An SEM and an atomic force microscope (AFM) were used to characterize the surface morphology of the mild steel coupons. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to characterize the inhibition mechanism of PBSLP, and the inhibitor was a mixed-type corrosion inhibitor with a maximum corrosion inhibition efficiency of 93.0%. Adsorption studies revealed the adsorption of PBSLP to be a monolayer process and therefore, obeyed the Langmuir isotherm model.

scholarly journals Effet of edge fluorination and chlorination on structures, stability, electronic and charge transport properties of benzo[o]bistriphenyleno[2,1,12,11-efghi:2',1',12',11'-uvabc]ovalene molecule : DFT study.

2021 ◽  
Author(s):  
Marius Ousmanou Bouba ◽  
Fridolin Tchangnwa Nya ◽  
Christine Yvette Ngui ◽  
Jean Marie Ndjaka
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Charge Carriers ◽  
Bandgap Energy ◽  
Electron Affinities ◽  
New Materials ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Theoretical Investigations ◽  
Good Agreement

Abstract We have investigated the structures, electronic properties, hole and electron mobilities of fluorinated and chlorinated nanographene of benzo[o]bistriphenyleno[2,1,12,11-efghi:2',1',12',11'-uvabc]ovalene (TCHG) molecules, us- ing the density functional theory (DFT) and Markus-Hush charge transfer theory. The calculated geometric parameters and the IR spectrum for chlorinated TCHG are in good agreement with the experimental data. Our theoretical investigations have shown that fluorination and chlorination significantly reduce the bandgap energy of TCHG. The obtained adiabatic electron affinities (AEAs) values are 2.76 and 2.93 eV respectively, indicating the air-stable materials. The calculation of charge carriers mobilities in chlorinated dimer shows that the mobility of the electrons is ten times that of the holes, suggesting an n-type behavior. We have shown that the fluorination and chlorination of TCHG are promising pathways for the design of new materials useful in optoelectronics

scholarly journals Electrochemical And DFT Investigations of Anticorrosive Potentials of Selected Sulphonamides Based On Adsorption At Aluminium/Aqueous Acid Interface

2021 ◽  
Author(s):  
Lutendo C. Murulana ◽  
Tshimangadzo Nesane ◽  
Mwadham M. Kabanda ◽  
Lukman O. Olasunkanmi ◽  
Eno E. Ebenso
Keyword(s):  
Density Functional ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Functional Theory ◽  
Surface Protection ◽  
Adsorption Sites ◽  
Aqueous Acid ◽  
Langmuir Isotherm Model ◽  
Current Densities ◽  
Eis Measurements

Abstract The anticorrosive properties of six (6) selected sulphonamide derivatives on the aluminium surface were investigated in order to reveal their mechanism and mode of adsorption on Al/HCl interface, as well as the strength of the interactions between the inhibitor and Al surface. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques were utilised to evaluate the inhibition efficiencies of the selected compounds, while scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy techniques were utilised to understand the surface morphology of Al and adsorption sites of the sulphonamides. Density functional theory (DFT) calculations were utilised to investigate the strength of interactions between the inhibitor molecules and Al. Corrosive electrolyte of 1 M hydrochloric acid was employed in the study. All the studied sulphonamides showed excellent corrosion inhibition efficiencies with maximum values of up to 95%-97% at the optimum concentrations (4 × 10-5 M - 4 × 10-5 M), based on EIS measurements. The EIS parameters further revealed adsorbed film of the sulphonamides on the Al surface with capacitive-inductive characters. All the six sulphonamides reduced the corrosion current densities for both anodic and cathodic half-reactions and shifted the corrosion potentials to some anodically nobler values as revealed by the PDP data. Adsorption of the sulphonamides at the Al/HCl interface was described by the Langmuir isotherm model. Surface protection properties of the sulphonamides were further confirmed by SEM plates that showed less damaged surface of Al for the inhibited process compared to the uninhibited one. DFT results suggest that the binding energy for the inhibitors on the Al surface results in an energy that is less than 30 kJ/mol, which is an indication that the interactions are van der Waal type of interaction, suggesting physisorption mechanism.

Theoretical investigation on the photoelectrochemical anticorrosion mechanism of SnO2–TiO2nanotube

2019 ◽  
Vol 18 (03) ◽  
pp. 1950016 ◽  
Author(s):  
Yang Meng ◽  
Jianjun Zhang ◽  
Zhunzhun Wang ◽  
Jin-Xia Liang ◽  
Chun Zhu
Keyword(s):  
Density Functional ◽  
Composite Films ◽  
Photocurrent Density ◽  
304 Stainless Steel ◽  
Functional Theory ◽  
Photogenerated Electrons ◽  
Theoretical Investigations ◽  
Charge Analysis ◽  
Good Agreement

In this work, the calculated electron density difference, Bader charge analysis and the density of states (DOS) of SnO2–TiO2-nanotubes (NTs) indicate that the electrons are transferred from the Ti atoms of TiO2into the O atoms of (SnO[Formula: see text] in SnO2–TiO2-NTs and the supported (SnO[Formula: see text] cluster acts as the role of storage for photogenerated electrons excited from TiO2-NTs, which is in good agreement with experimental results that the SnO2–TiO2-NTs composite films have higher photocurrent density for photocathodic protection of 304 stainless steel (304SS). The theoretical investigations provide a plausible explanation for the photoelectrochemical anticorrosion mechanism of SnO2–TiO2-NTs using periodic density functional theory (DFT).

scholarly journals Perhalogenation and Percyanation of Coronene for Characterization of the New Efficient Organic Semiconductors for Charge Transport

2021 ◽  
Author(s):  
Marius Ousmanou Bouba ◽  
Fridolin Tchangnwa Nya ◽  
Alhadji Malloum ◽  
Jeanet Conradie ◽  
Jean Marie Ndjaka
Keyword(s):  
Organic Semiconductors ◽  
Density Functional ◽  
Functional Theory ◽  
Vibrational Assignments ◽  
Ambipolar Behavior ◽  
The Density Functional Theory ◽  
Theoretical Investigations ◽  
Stable Material ◽  
Good Agreement

Abstract We have investigated the structures, electronic properties, hole and electron mobilities of perfluorinated, perchlorinated and percyanated coronene molecules, using the density functional theory (DFT) at the B3LYP-D3/6-311++G(d,p) and ωB97XD/6-311++G(d,p) levels and Markus-Hush charge transfer theory. The calculated geometric parameters for coronene and perchlorocoronene are in good agreement with the experimental data. Our theoretical investigations have shown B3LYP-D3 functional is suitable to well define vibrational assignments for studied molecules. We have shown that the per-halogenation and per-cyanation of coronene increases the adiabatic electron affinities (AEAs) and reduces the LUMO levels and the hole mobilities thus indicating an ambipolar behavior and air-stable material. We have shown that the percyanation of coronene is a promising pathway for the design of new materials useful in optoelectronics.

Synthesis of New α-Amino Phosphonates Containing 3-Amino-4(3H) Quinazolinone Moiety as Anticancer and Antimicrobial Agents: DFT, NBO, and Vibrational Studies

2018 ◽  
Vol 15 (2) ◽  
pp. 286-296 ◽  
Author(s):  
Mohamed K. Awad ◽  
Mahmoud F. Abdel-Aal ◽  
Faten M. Atlam ◽  
Hend A. Hekal
Keyword(s):  
Biological Activity ◽  
Cell Line ◽  
Quantum Chemical ◽  
Density Functional ◽  
Carcinoma Cell ◽  
Liver Carcinoma ◽  
Anticancer Activities ◽  
Functional Theory ◽  
Ft Ir ◽  
Good Agreement

Aim and Objective: Synthesis of new .-aminophosphonates containing quinazoline moiety through Kabachnik-Fields reaction in the presence of copper triflate catalyst [32], followed by studying their antimicrobial activities and in vitro anticancer activities against liver carcinoma cell line (HepG2) with the hope that new anticancer agents could be developed. Also, the quantum chemical calculations are performed using density functional theory (DFT) to study the effect of the changes of molecular and electronic structures on the biological activity of the investigated compounds. Materials and Method: The structures of the synthesized compounds are confirmed by FT-IR, 1H NMR, 13C NMR, 31P NMR and MS spectral data. The synthesized compounds show significant antimicrobial and also remarkable cytotoxicity anticancer activities against liver carcinoma cell line (HepG2). Density functional theory (DFT) was performed to study the effect of the molecular and electronic structure changes on the biological activity. Results: It was found that the electronic structure of the substituents affects on the reaction yield. The electron withdrawing substituent, NO2 group 3b, on the aromatic aldehydes gave a good yield more than the electron donating substituent, OH group 3c. The electron deficient on the carbon atom of the aldehydic group may increase the interaction of the Lewis acid (Cu(OTf)2) and the Lewis base (imine nitrogen), and accordingly, facilitate the formation of imine easily, which is attacked by the nucleophilic phosphite species to give the α- aminophosphonates. Conclusion: The newly synthesized compounds exhibit a remarkable inhibition of the growth of Grampositive, Gram-negative bacteria and fungi at low concentrations. The cytotoxicity of the synthesized compounds showed a significant cytotoxicity against the liver cancer cell line (HepG 2). Also, it was shown from the quantum chemical calculations that the electron-withdrawing substituent increases the biological activity of the α-aminophosphonates more than the electron donating group which was in a good agreement with the experimental results. Also, a good agreement between the experimental FT-IR and the calculated one was found.

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

scholarly journals Changes in CO2 Adsorption Affinity Related to Ni Doping in FeS Surfaces: A DFT-D3 Study

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 486
Author(s):  
Aleksandar Zivković ◽  
Michiel Somers ◽  
Eloi Camprubi ◽  
Helen E. King ◽  
Mariette Wolthers ◽  
...  
Keyword(s):  
Density Functional ◽  
Organic Molecules ◽  
Ni Doping ◽  
Functional Theory ◽  
Small Organic Molecules ◽  
Adsorption Affinity ◽  
The Origin Of Life ◽  
Carbon Dioxide Co2 ◽  
Partial Desorption ◽  
Good Agreement

Metal sulphides constitute cheap, naturally abundant, and environmentally friendly materials for energy storage applications and chemistry. In particular, iron (II) monosulphide (FeS, mackinawite) is a material of relevance in theories of the origin of life and for heterogenous catalytic applications in the conversion of carbon dioxide (CO2) towards small organic molecules. In natural mackinawite, Fe is often substituted by other metals, however, little is known about how such substitutions alter the chemical activity of the material. Herein, the effect of Ni doping on the structural, electronic, and catalytic properties of FeS surfaces is explored via dispersion-corrected density functional theory simulations. Substitutional Ni dopants, introduced on the Fe site, are readily incorporated into the pristine matrix of FeS, in good agreement with experimental measurements. The CO2 molecule was found to undergo deactivation and partial desorption from the doped surfaces, mainly at the Ni site when compared to undoped FeS surfaces. This behaviour is attributed to the energetically lowered d-band centre position of the doped surface, as a consequence of the increased number of paired electrons originating from the Ni dopant. The reaction and activation energies of CO2 dissociation atop the doped surfaces were found to be increased when compared to pristine surfaces, thus helping to further elucidate the role Ni could have played in the reactivity of FeS. It is expected that Ni doping in other Fe-sulphides may have a similar effect, limiting the catalytic activity of these phases when this dopant is present at their surfaces.

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