Insights into the Fe3+ Doping Effects on the Structure and Electron Distribution of Cr2O3 Nanoparticles

Herein, we carefully investigated the Fe3+ doping effects on the structure and electron distribution of Cr2O3 nanoparticles using X-ray diffraction analysis (XRD), maximum entropy method (MEM), and density functional theory (DFT) calculations. We showed that increasing the Fe doping induces an enlargement in the axial ratio of c/a, which is associated with an anisotropic expansion of the unit cell. We found that as Fe3+ replaces Cr in the Cr2O3 lattice, it caused a higher interaction between the metal 3d states and the oxygen 2p states, which led to a slight increase in the Cr/Fe-O1 bond length followed by an opposite effect for the Cr/Fe-O2 bonds. Our results also suggest that the excitations characterize a well-localized bandgap region from occupied Cr d to unoccupied Fe d states. The Cr2O3 and Fe-doped Cr2O3 nanoparticles behave as Mott-Hubbard insulators due to their band gap being in the d-d gap, and Cr 3d orbitals dominate the conduction band. These findings suggest that the magnitude and the character of the electronic density near the O atom bonds in Cr2O3 nanoparticles are modulated by the Cr-Cr distances until its stabilization at the induced quasi-equilibrium of the Cr2O3 lattice when the Fe3+ doping values reaches the saturation level range.

Electrolyte pH dependence of composition, roughness parameters, particle diameter and magnetic features of nanostructured Fe-Co-Ni/ITO deposits prepared by electrochemical deposition method

The composition, structural features, surface morphology, roughness parameters, particle size, and magnetic features of nanostructured Fe-Co-Ni deposits manufactured on conducting indium tin oxide-coated glasses at various electrolyte pH values are studied. The deposit produced at low electrolyte pH contains slightly higher Fe and Co contents but lower Ni content compared to deposits fabricated at high pH values. Further composition analysis confirms that the reduction rates of Fe²⁺ and Co²⁺ are higher than the Ni²⁺ reduction rate. The films consist of nano-sized crystallites with a strong [111] preferred orientation. The results also reveal that the crystallization of the thin films is affected by the electrolyte pH. Surface analysis shows that the deposit surfaces are composed of nano-sized particles with different diameters. The mean particle diameter and surface roughness decrease as the pH of the electrolyte decreases. The effect of the electrolyte pH on the morphology is also discussed in terms of surface skewness and kurtosis parameters. Magnetic analysis shows that the resultant deposits have in-plane hysteresis loops with low and close SQR parameters ranging from 0.079 to 0.108. The results also reveal that the coercive field of the deposits increases from 29.4 Oe to 41.3 Oe as the electrolyte pH decreases from 4.7 to 3.2.

Tuning structural properties, morphology and magnetic characteristics of nanostructured Ni-Co-Fe/ITO ternary alloys by galvanostatic pretreatment process

In this research, the structural properties, surface morphology, and magnetic characteristics of nanostructured ternary ferromagnetic alloys grown by a cost-effective and effortless two-step electrochemical deposition method on indium tin oxide (ITO) substrates with and without a galvanostatic pretreatment process (GPP) were examined. The GPP was applied at various pretreatment current densities (PCDs) such as -10, -20, and - 30 mA/cm² . The effect of the PCD on the Ni, Co, and Fe contents is found to be insignificant and all resultant Ni-Co-Fe thin films show an abnormal co-deposition. The films have nano-sized crystallites ranging from 17.3 to 19.6 nm and showed a face-centered cubic structure with the [111] preferential growth. Compared to the non-GPP applied Ni-Co-Fe film, growing the ternary Ni-Co-Fe film on ITO at the PCD of -30 mA/cm² causes an improvement in the crystal quality and a reduction in the particle size from 150 ± 50 to 70 ± 20 nm. A decrement in the surface roughness and coercivity was also achieved by applying the GPP at the PCD of -30 mA/cm² , but the opposite is true for the GPP performed at the PCD of -10 mA/cm² . The GPP has an effect on the magnetic Squareness Ratio (SQR), but the influence of the PCD on the SQR parameter is negligible. The obtained findings reveal that the properties of the Ni-Co-Fe/ITO ternary alloys can be tuned through the GPP applied in various PCDs. HIGHLIGHTS: • The effect of the PCD on the Ni, Co, and Fe contents is found to be insignificant. • The films have nano-sized crystallites and showed a face-centered cubic structure with the [111] preferential growth. • The analysis reveals that the GPP changes the crystal quality, H_c parameter, surface roughness, and particle size of the films. • The GPP has an effect on the magnetic squareness ratio (SQR), but the influence of the PCD on the SQR parameter is negligible. • The films had nano-sized crystallites ranging from 17.3 to 19.6 nm. • The films were ferromagnetic, and the H_c and SQR parameters of the films ranged from 30.2 to 42.7 Oe and from 8.8% to 19.6%.

Synthesis and Characterization of Polypyrrole Film Doped with Both Molybdate and Salicylate and Its Application in the Corrosion Protection for Low Carbon Steel

Polypyrrole (PPy) films doped with molybdate and salicylate have been successfully electropolymerized on low carbon steel in aqueous solutions containing both molybdate and salicylate in a one-step process that did not require any pre-treatment of the steel substrate. Salicylate-doped PPy films were synthesized in the same way for comparison. The steel surface was rapidly inhibited and the PPy-based films were formed on it easily. The PPy-based films were characterized by Fourier transform infrared, scanning electron microscopy, energy dispersive X-ray, and thermal gravimetric analysis methods. The corrosion protection performance of the coatings was investigated with electrochemical impedance spectroscopy, open circuit potential (OCP), salt spray test, and Tafel polarization. It was found that in the presence of both molybdate and salicylate as dopants, the films on steel could present a better corrosion resistance than PPy film doped with only salicylate. The self-healing property of PPy-based films was observed on the OCP measurement with the fluctuation of rest potential. The salt spray test results showed that the PPy film doped with both salicylate and molybdate was more salt-resistant than the PPy film doped with only salicylate. The results suggest that the PPy coatings doped with both molybdate and salicylate are potential for application as metallic anti-corrosion coatings.

DFT study on some polythiophenes containing benzo[d]thiazole and benzo[d]oxazole: structure and band gap

The content of this paper focuses/shed light on the effects of X (X = S in P1 and X = O in P2) in C11H7NSX and R (R = H in P3, R = OCH3 in P4, and R = Cl in P5) in C18H9ON2S2-R on structural features and band gaps of the polythiophenes containing benzo[d]thiazole and benzo[d]oxazole by the Density Function Theory (DFT) method/calculation. The structural features including the electronic structure lattice constant (a), shape, total energy (Etot) per cell, and link length (r), are measured via band gap (Eg) prediction with the package of country density (PDOS) and total country density (DOS) of material studio software. The results obtained showed that the link angle and the link length between atoms were not changed significantly while the Etot was decreased from Etot = - 1904 eV (in P1) to Etot = - 2548 eV (in P2) when replacing O with S; and the Etot of P3 was decreased from Etot = - 3348 eV (in P3) when replacing OCH3, Cl on H of P3 corresponding to Etot = - 3575 eV (P4), - 4264 eV (P5). Similarly, when replacing O in P1 with - S to form P2, the Eg of P1 was dropped from Eg = 0.621 eV to Eg = 0.239 eV for P2. The Eg of P3, P4, and P5 is Eg = 0.006 eV, 0.064 eV, and 0.0645 eV, respectively. When a benzo[d]thiazole was added in P1 (changing into P3), the Eg was extremely strongly decreased, nearly 100 times (from Eg = 0.621 eV to Eg = 0.006 eV). The obtained results serve as a basis for future experimental work and used to fabricate smart electronic device.

Effect of doped H, Br, Cu, Kr, Ge, As and Fe on structural features and bandgap of poly C13H8OS-X: a DFT calculation

Structural features such as the shape, the lattice constant, the bond length, the total energy per cell, and the energy bandgap (Eg) of C13H8OS-X are studied by the calculating Partial Density Of States (PDOS), and DOS package of the Material Studio (MS) software. Calculations show that the bond length and the bond angle between atoms insignificant change as 1.316 Å to 1.514 Å for C-C, 1.211 Å for C-O, 1.077 Å to 1.105 Å for C-H; bond angle of round one changes from 118.883° to 121.107° for C-C-C, from 117.199° to 122.635° for H-C-C, from 119.554° to 123.147° for C-C-O and from 109.956° to 117.537° for C-C-H. When C13H8OS-X doped in the order of -Br, -Cu, -Kr, -Ge, -As, and -Fe then bond lengths, bond angles between atoms have a nearly constant value. Particularly for links C-X, there is a huge change in value, respectively 1.876, 1.909, 10.675, 2.025, 2.016, 2.014 Å; the total energy change from Etot = -121,794 eV to Etot = -202,859 eV, and the energy band gap decreases from Eg = 2.001 eV to Eg = 0.915 eV. The obtained results are useful and serve as a basis for future experimental research.

Influence of heating rate, temperature, pressure on the structure, and phase transition of amorphous Ni material: A molecular dynamics study

The present article is aimed to investigate influence of the heating rate, temperature (T), pressure (P) on the structure and phase transition of amorphous Ni material with heating rate 2 × 10⁵, 2 × 10⁶ and 2 × 10⁷ K/s at T = 300 K; T = 300, 400, 500, 600, 700, 800, 900 and 1000 K at heating rate 2 × 10⁶ K/s; T = 300, 621 and 900 K at P = 1, 2, 3, 4 and 5 GPa by molecular dynamics simulation method with Sutton-Chen embedded potential and periodic boundary conditions. The structure of amorphous Ni material determined through the radial distribution function, the total energy, the size and the average coordination number. The phase transition and the glass transition temperature determined through the relationship between the total energy and temperature. The result shows that when the heating rate increases, the first peak's position for the radial distribution function is 2.45 Å and a constant, the first peak's height, the total energy and the size increase, the average coordination number decreases from 13 to 12. When temperature increases from 300 to 1000 K at P = 0 GPa, the position decreases from 2.45 Å to 2.40 Å, the average coordination number is 13 and a constant, glass transition temperature is 631 K, the total energy increases, the size increases and happens the phase transition from the amorphous state to the liquid state. When pressure increases from 0 GPa to 5 GPa at T = 300, 621 and 900 K, the position decreases, the height increases, the total energy increases, the size decreases, the average coordination number decreases from 13 to 12, that shows with amorphous Ni material when increasing heating rate, T, P lead to structural change, phase transition of materials is significant.

Ab Initio Calculations on the Structural and Electronic Properties of AgAu Alloys

In our paper, we study the effects of pseudopotential and concentration of Au doping (0, 25, 50, 75, 100%) on the geometric structure and electronic structures of AgAu alloys. For this purpose, we use ab initio quantum calculations in the Material Studios software. The geometric structures of materials are confirmed through the lattice constant, crystal structure, and total energy of the unit cells (E _tot). Electronic structures of the materials are confirmed by band gap (E_g), projected density of states (PDOS), and total density of states (DOS). The obtained results show that the pseudopotential and concentration of Au doping on AgAu alloys play an important role in the origin of the physical properties of AgAu alloys.