Crystallographic Calculations and First-Principles Calculations of Heterogeneous Nucleation Potency of γ-Fe on La2O2S Particles

Rare earth (RE) inclusions with high melting points as heterogeneous nucleation in liquid steel have stimulated many recent studies. Evaluating the potency of RE inclusions as heterogeneous nucleation sites of the primary phase is still a challenge. In this work, the edge-to-edge matching (E2EM) model was employed to calculate the atomic matching mismatch and predict the orientation relationship between La₂O₂S and γ-Fe from a crystallographic point of view. A rough orientation relationship (OR) was predicted with the minimum values of fr=9.43% and fd=20.72% as follows: [21¯1¯0]La2O2S∥[100]γ-Fe and (0003¯)La2O2S∥(002¯)γ-Fe. The interface energy and bonding characteristics between La₂O₂S and γ-Fe were calculated on the atomic scale based on a crystallographic study using the first-principles calculation method. The calculations of the interface energy showed that the S-terminated and La(S)-terminated interface structures were more stable. The results of difference charge density, electron localization function (ELF), the Bader charges and the partial density of states (PDOS) study indicated that the La(S)-terminated interface possessed metallic bonds and ionic bonds, and the S-terminated interface exhibited metallic bond and covalent bond characteristics. This work addressed the stability and the characteristics of the La₂O₂S/γ-Fe interface structure from the standpoint of crystallography and energetics, which provides an effective theoretical support to the study the heterogeneous nucleation mechanism. As a result, La₂O₂S particles are not an effective heterogeneous nucleation site for the γ-Fe matrix from crystallography and energetics points of view.     

A High-Performance ε-Ga2O3-Based Deep-Ultraviolet Photodetector Array for Solar-Blind Imaging

One of the most important applications of photodetectors is as sensing units in imaging systems. In practical applications, a photodetector array with high uniformity and high performance is an indispensable part of the imaging system. Herein, a photodetector array (5 × 4) consisting of 20 photodetector units, in which the photosensitive layer involves preprocessing commercial ε-Ga₂O₃ films with high temperature annealing, have been constructed by low-cost magnetron sputtering and mask processes. The ε-Ga₂O₃ ultraviolet photodetector unit shows excellent responsivity and detectivity of 6.18 A/W and 5 × 10¹³ Jones, respectively, an ultra-high light-to-dark ratio of 1.45 × 10⁵, and a fast photoresponse speed (0.14/0.09 s). At the same time, the device also shows good solar-blind characteristics and stability. Based on this, we demonstrate an ε-Ga₂O₃-thin-film-based solar-blind ultraviolet detector array with high uniformity and high performance for solar-blind imaging in optoelectronic integration applications.     

Oxygen Vacancy Formation and Migration within the Antiphase Boundaries in Lanthanum Scandate-Based Oxides: Computational Study

The atomic structure of antiphase boundaries in Sr-doped lanthanum scandate (La_1−xSr_xScO_3−δ) perovskite, promising as the proton conductor, was modelled by means of DFT method. Two structural types of interfaces formed by structural octahedral coupling were constructed: edge- and face-shared. The energetic stability of these two interfaces was investigated. The mechanisms of oxygen vacancy formation and migration in both types of interfaces were modelled. It was shown that both interfaces are structurally stable and facilitate oxygen ionic migration. Oxygen vacancy formation energy in interfaces is lower than that in the regular structure, which favours the oxygen vacancy segregation within such interfaces. The calculated energy profile suggests that both types of interfaces are advantageous for oxygen ion migration in the material.     

Phonon Structure,Infra-Red and Raman Spectra of Li2MnO3 by First-Principles Calculations

The layer-structured monoclinic Li₂MnO₃ is a key material, mainly due to its role in Li-ion batteries and as a precursor for adsorbent used in lithium recovery from aqueous solutions. In the present work, we used first-principles calculations based on density functional theory (DFT) to study the crystal structure, optical phonon frequencies, infra-red (IR), and Raman active modes and compared the results with experimental data. First, Li₂MnO₃ powder was synthesized by the hydrothermal method and successively characterized by XRD, TEM, FTIR, and Raman spectroscopy. Secondly, by using Local Density Approximation (LDA), we carried out a DFT study of the crystal structure and electronic properties of Li₂MnO₃. Finally, we calculated the vibrational properties using Density Functional Perturbation Theory (DFPT). Our results show that simulated IR and Raman spectra agree well with the observed phonon structure. Additionally, the IR and Raman theoretical spectra show similar features compared to the experimental ones. This research is useful in investigations involving the physicochemical characterization of Li₂MnO₃ material.     

Cobalt Minimisation in Violet Co3P2O8 Pigment

This study considers the limitations of cobalt violet orthophosphate, Co₃P₂O₈, in the ceramic industry due to its large amount of cobalt. Mg_xCo_3−xP₂O₈ (0 ≤ x ≤ 3) solid solutions with the stable Co₃P₂O₈ structure were synthesised via the chemical coprecipitation method. The formation of solid solutions between the isostructural Co₃P₂O₈ and Mg₃P₂O₈ compounds decreased the toxically large amount of cobalt in this inorganic pigment and increased the melting point to a temperature higher than 1200 °C when x ≥ 1.5. Co₃P₂O₈ melted at 1160 °C, and compositions with x ≥ 1.5 were stable between 800 and 1200 °C. The substitution of Co(II) with Mg(II) decreased the toxicity of these materials and decreased their price; hence, the interest of these materials for the ceramic industry is greater. An interesting purple colour with a* = 31.6 and b* = −24.2 was obtained from a powdered Mg_2.5Co_0.5P₂O₈ composition fired at 1200 °C. It considerably reduced the amount of cobalt, thus improving the colour of the Co₃P₂O₈ pigment (a* = 16.2 and b* = −20.1 at 1000 °C). Co₃P₂O₈ is classified as an inorganic pigment (DCMA-8-11-1), and the solid solutions prepared were also inorganic pigments when unglazed. When introducing 3% of the sample (pigment) together with enamel, spreading the mixture on a ceramic support and calcining the whole in an electric oven, a colour change from violet to blue was observed due to the change in the local environment of Co(II), which could be seen in the UVV spectra of the glazed samples with the displacement of the bands towards higher wavelengths and with the appearance of a new band assigned to tetrahedral Co(II). This blue colour was also obtained with Co₂SiO₄, MgCoSiO₄ or Co₃P₂O₈ pigments containing a greater amount of cobalt.     

Reinforced 3D Composite Structures of γ-, α-Al2O3 with Carbon Nanotubes and Reduced GO Ribbons Printed from Boehmite Gels

The ability of boehmite to form printable inks has sparked interest in the manufacturing of 3D alumina (Al₂O₃) and composite structures by enabling direct ink writing methods while avoiding the use of printing additives. These materials may exhibit high porosity due to the printing and sintering procedures, depending on the intended application. The 3D-printed porous composite structures of γ-Al₂O₃ and α-Al₂O₃ containing 2 wt.% of carbon nanotubes or reduced graphene oxide ribbons were fabricated from boehmite gels, followed by different heat treatments. The reinforcing effect of these carbon nanostructures was evidenced by compression tests carried out on the different alumina structures. A maximum relative increase of 50% in compressive strength was achieved for the γ-Al₂O₃ composite structure reinforced with reduced graphene oxide ribbons, which was also accompanied by an increase in the specific surface area.     

Uptake of Radionuclides 60Co, 137Cs,and 90Sr with α-Fe2O3 and Fe3O4 Particles from Aqueous Environment

In the paper, investigation results of the uptake efficiency of radionuclides ⁶⁰Co, ⁹⁰Sr, and ¹³⁷Cs dissolved in water onto iron oxides α-Fe₂O₃ and Fe₃O₄ are presented. It was found that sorption efficiency increased for higher pH values. Independent of the oxide nature, the uptake characteristics are the best toward ⁶⁰Co and the worst toward ¹³⁷Cs, forming the row as follows: ⁶⁰Co > ⁹⁰Sr > ¹³⁷Cs. The highest sorption ability at pH 9 was found for magnetite Fe₃O₄, which was 93%, 73%, and 26% toward ⁶⁰Co, ⁹⁰Sr, and ¹³⁷Cs, respectively, while the respective percentages for hematite α-Fe₂O₃ were 85%, 41%, and 18%. It was assumed that the main sorption mechanism was ion exchange. That may explain some decrease of the sorption efficiency in drinking water due to the interfering presence of magnesium and calcium cations. The obtained results indicated the feasibility of the tested sorbents and their merits, especially in terms of relatively high uptake coefficients, low costs, availability, and lack of toxicity.     

Drastic Dependence of the pH Sensitivity of Fe2O3-Bi2O3-B2O3 Hydrophobic Glasses with Composition

Fe₂O₃-Bi₂O₃-B₂O₃ (FeBiB) glasses were developed as novel pH responsive hydrophobic glasses. The influence of the glass composition on the pH sensitivity of FeBiB glasses was investigated. The pH sensitivity drastically decreased with decreasing B₂O₃ content. A moderate amount of Fe₂O₃ and a small amount of B₂O₃ respectively produces bulk electronic conduction and a pH response on glass surfaces. Because the remaining components of the glass can be selected freely, this discovery could prove very useful in developing novel pH glass electrodes that are self-cleaning and resist fouling.     

Peculiarities of γ-Al2O3 Crystallization on the Surface of h-BN Particles

The main goal of the present work was to synthesize a composite consisting of h-BN particles coated with a γ-Al₂O₃ nanolayer. A method was proposed for applying nanocrystalline γ-Al₂O₃ to h-BN particles using a sol–gel technique, which ensures the chemical homogeneity of the composite at the nano level. It has been determined that during crystallization on the h-BN surface, the proportion of spinel in alumina decreases from 40 wt.% in pure γ-Al₂O₃ to 30 wt.% as a result of the involvement of the B³⁺ ions from the surface nitride monolayers into the transition complex. For comparison, nano-alumina was synthesized from the same sol under the same conditions as the composite. The characterization of the obtained nanostructured powders was carried out using TEM and XRD. A mechanism is proposed for the formation of a nanostructured γ-Al₂O₃@h-BN composite during the interaction of Al-containing sol and h-BN suspension in aqueous organic media. The resulting composite is a promising model of powdered raw materials for the development of fine-grained ceramic materials for a wide range of applications.     

Structural Features of Y2O2SO4 via DFT Calculations of Electronic and Vibrational Properties

The traditional way for determination of molecular groups structure in crystals is the X-Ray diffraction analysis and it is based on an estimation of the interatomic distances. Here, we report the analysis of structural units in Y₂O₂SO₄ using density functional theory calculations of electronic properties, lattice dynamics and experimental vibrational spectroscopy. The Y₂O₂SO₄ powder was successfully synthesized by decomposition of Y₂(SO₄)₃ at high temperature. According to the electronic band structure calculations, yttrium oxysulfate is a dielectric material. The difference between the oxygen–sulfur and oxygen–yttrium bond nature in Y₂O₂OS₄ was shown based on partial density of states calculations. Vibrational modes of sulfur ions and [Y₂O₂²⁺] chains were obtained theoretically and corresponding spectral lines observed in experimental Infrared and Raman spectra.     

Effective Attenuation of Electromagnetic Waves by Synergetic Effect of α-Fe2O3 and MWCNT/Graphene in LDPE-Based Composites for EMI Applications

In this study, a polymer nanocomposite is synthesized using magnetic and conducting fillers for enhanced electromagnetic interference (EMI) shielding. Alfa-ferrite (α-Fe₂O₃) nanoparticles with minimal multiwalled carbon nanotube (MWCNT) as low as 5 weight % in combination with variable concentrations of graphene nanoplatelets (GNP) are used as fillers in low-density polyethylene (LDPE) polymer matrix. Nanofillers and the polymer matrix are characterized by various techniques such as XRD, SEM, color mapping, EDAX, TGA, etc. The EMI shielding efficiency of the LDPE-based nanocomposites is tested using Vector Network Analyzer (VNA). The results showed that composite with LDPE:MWCNT:GNP:α-FO-50:5:40:5 displayed enhanced EMI shielding (in X-band (8.2–12.4 GHz) compared to other concentrations studied. This is due to the superior ohmic, dielectric, and magnetic losses at this particular composition and to the synergism amongst the filler. An attenuation of 99.99% was achieved for 5% α-Fe₂O₃. The mechanistic aspects of the shielding are discussed using permittivity, conductivity, and attenuation.     

Characterization of Ionic Transport in Li2O-(Mn:Fe)2O3-P2O5 Glasses for Li Batteries

We present a systematic study of the lithium-ion transport upon the mixed manganese-iron oxide phosphate glasses 3Li₂O-xMn₂O₃-(2-x)Fe₂O₃-3P₂O₅(LM_xF_2−xPO; 0≤ x ≤2.0) proposed for the use in a cathode for lithium secondary batteries. The glasses have been fabricated using a solid reaction process. The electrical characteristics of the glass samples have been characterized by electrical impedance in the frequency range from 100 Hz to 30 MHz and temperature from 30 °C to 240 °C. Differential thermal analysis and X-ray diffraction were used to determine the thermal and structural properties. It has been observed that the dc conductivity decreases, but the activation energies of dc and ac and the glass-forming ability increase with the increasing Mn₂O₃ content in LM_xF_2−xPO glasses. The process of the ionic conduction and the relaxation in LM_xF_2−xPO glasses are determined by using power–law, Cole–Cole, and modulus methods. The Li⁺ ions migrate via the conduction pathway of the non-bridging oxygen formed by the depolymerization of the mixed iron–manganese–phosphate network structure. The mixed iron–manganese content in the LM_xF_2−xPO glasses constructs the sites with different depths of the potential well, leading to low ionic conductivity.     

SARS-CoV-2 Infects Human ACE2-Negative Endothelial Cells through an αvβ3 Integrin-Mediated Endocytosis Even in the Presence of Vaccine-Elicited Neutralizing Antibodies

Integrins represent a gateway of entry for many viruses and the Arg-Gly-Asp (RGD) motif is the smallest sequence necessary for proteins to bind integrins. All Severe Acute Respiratory Syndrome Virus type 2 (SARS-CoV-2) lineages own an RGD motif (aa 403–405) in their receptor binding domain (RBD). We recently showed that SARS-CoV-2 gains access into primary human lung microvascular endothelial cells (HL-mECs) lacking Angiotensin-converting enzyme 2 (ACE2) expression through this conserved RGD motif. Following its entry, SARS-CoV-2 remodels cell phenotype and promotes angiogenesis in the absence of productive viral replication. Here, we highlight the α_vβ₃ integrin as the main molecule responsible for SARS-CoV-2 infection of HL-mECs via a clathrin-dependent endocytosis. Indeed, pretreatment of virus with α_vβ₃ integrin or pretreatment of cells with a monoclonal antibody against α_vβ₃ integrin was found to inhibit SARS-CoV-2 entry into HL-mECs. Surprisingly, the anti-Spike antibodies evoked by vaccination were neither able to impair Spike/integrin interaction nor to prevent SARS-CoV-2 entry into HL-mECs. Our data highlight the RGD motif in the Spike protein as a functional constraint aimed to maintain the interaction of the viral envelope with integrins. At the same time, our evidences call for the need of intervention strategies aimed to neutralize the SARS-CoV-2 integrin-mediated infection of ACE2-negative cells in the vaccine era.     

Green Synthesis of Hexagonal Hematite (α-Fe2O3) Flakes Using Pluronic F127-Gelatin Template for Adsorption and Photodegradation of Ibuprofen

Hematite (α-Fe₂O₃) with uniform hexagonal flake morphology has been successfully synthesized using a combination of gelatin as natural template with F127 via hydrothermal method. The resulting hematite was investigated as adsorbent and photocatalyst for removal of ibuprofen as pharmaceutical waste. Hexagonal flake-like hematite was obtained following calcination at 500 °C with the average size was measured at 1–3 µm. Increasing the calcination temperature to 700 °C transformed the uniform hexagonal structure into cubic shape morphology. Hematite also showed high thermal stability with increasing the calcination temperatures; however, the surface area was reduced from 47 m²/g to 9 m²/g. FTIR analysis further confirmed the formation Fe-O-Fe bonds, and the main constituent elements of Fe and O were observed in EDX analysis for all samples. α-Fe₂O₃ samples have an average adsorption capacity of 55–25.5 mg/g at 12–22% of removal efficiency when used as adsorbent for ibuprofen. The adsorption capacity was reduced as the calcination temperatures increased due to the reduction of available surface area of the hexagonal flakes after transforming into cubes. Photocatalytic degradation of ibuprofen using hematite flakes achieved 50% removal efficiency; meanwhile, combination of adsorption and photocatalytic degradation further removed 80% of ibuprofen in water/hexane mixtures.     

First-Principles Calculation of the Bonding Strength of the Al2O3-Fe Interface Enhanced by Amorphous Na2SiO3

In this paper, the interfacial adhesion work (W_ad), tensile strength, and electronic states of the Fe-amorphous Na₂SiO₃-Al₂O₃ and Fe-Al₂O₃ interfaces are well-investigated, utilizing the first-principles calculations. The results indicate that the Fe-amorphous Na₂SiO₃-Al₂O₃ interface is more stable and wettable than the interface of Fe-Al₂O₃. Specifically, the interfacial adhesion work of the Fe-amorphous Na₂SiO₃ interface is 434.89 J/m², which is about forty times that of the Fe-Al₂O₃ interface, implying that the addition of amorphous Na₂SiO₃ promotes the dispersion of Al₂O₃ particle-reinforced. As anticipated, the tensile stress of the Fe-amorphous Na₂SiO₃-Al₂O₃ interface is about 46.58 GPa over the entire critical strain range, which is significantly greater than the Fe-Al₂O₃ interface control group. It could be inferred that the wear resistance of Al₂O₃ particle-reinforced is improved by adding amorphous Na₂SiO₃. To explain the electronic origin of this excellent performance, the charge density and density of states are investigated and the results indicate that the O atom in amorphous Na₂SiO₃ has a bonding action with Fe and Al; the amorphous Na₂SiO₃ acts as a sustained release. This study provides new ideas for particle-reinforced composites.     

Characterization of Al2O3 Samples and NiAl–Al2O3 Composite Consolidated by Pulse Plasma Sintering

The paper describes an investigation of Al₂O₃ samples and NiAl–Al₂O₃ composites consolidated by pulse plasma sintering (PPS). In the experiment, several methods were used to determine the properties and microstructure of the raw Al₂O₃ powder, NiAl–Al₂O₃ powder after mechanical alloying, and samples obtained via the PPS. The microstructural investigation of the alumina and composite properties involves scanning electron microscopy (SEM) analysis and X-ray diffraction (XRD). The relative densities were investigated with helium pycnometer and Archimedes method measurements. Microhardness analysis with fracture toughness (K_IC) measures was applied to estimate the mechanical properties of the investigated materials. Using the PPS technique allows the production of bulk Al₂O₃ samples and intermetallic ceramic composites from the NiAl–Al₂O₃ system. To produce by PPS method the NiAl–Al₂O₃ bulk materials initially, the composite powder NiAl–Al₂O₃ was obtained by mechanical alloying. As initial powders, Ni, Al, and Al₂O₃ were used. After the PPS process, the final composite materials consist of two phases: Al₂O₃ located within the NiAl matrix. The intermetallic ceramic composites have relative densities: for composites with 10 wt.% Al₂O₃ 97.9% and samples containing 20 wt.% Al₂O₃ close to 100%. The hardness of both composites is equal to 5.8 GPa. Moreover, after PPS consolidation, NiAl–Al₂O₃ composites were characterized by high plasticity. The presented results are promising for the subsequent study of consolidation composite NiAl–Al₂O₃ powder with various initial contributions of ceramics (Al₂O₃) and a mixture of intermetallic–ceramic composite powders with the addition of ceramics to fabricate composites with complex microstructures and properties. In composites with complex microstructures that belong to the new class of composites, in particular, the synergistic effect of various mechanisms of improving the fracture toughness will be operated.     

Ga2Te3-Based Composite Anodes for High-Performance Sodium-Ion Batteries

Recently, metal chalcogenides have received considerable attention as prospective anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacities based on their alloying or conversion reactions. Herein, we demonstrate a gallium(III) telluride (Ga₂Te₃)-based ternary composite (Ga₂Te₃–TiO₂–C) synthesized via a simple high-energy ball mill as a great candidate SIB anode material for the first time. The electrochemical performance, as well as the phase transition mechanism of Ga₂Te₃ during sodiation/desodiation, is investigated. Furthermore, the effect of C content on the performance of Ga₂Te₃–TiO₂–C is studied using various electrochemical analyses. As a result, Ga₂Te₃–TiO₂–C with an optimum carbon content of 10% (Ga₂Te₃–TiO₂–C(10%)) exhibited a specific capacity of 437 mAh·g⁻¹ after 300 cycles at 100 mA·g⁻¹ and a high-rate capability (capacity retention of 96% at 10 A·g⁻¹ relative to 0.1 A·g⁻¹). The good electrochemical properties of Ga₂Te₃–TiO₂–C(10%) benefited from the presence of the TiO₂–C hybrid buffering matrix, which improved the mechanical integrity and electrical conductivity of the electrode. This research opens a new direction for the improvement of high-performance advanced SIB anodes with a simple synthesis process.     

Layered Perovskites BaM2In2O7 (M = La,Nd): From the Structure to the Ionic (O2−, H+) Conductivity

The design of new oxide compounds that can be used as oxygen- or proton-conducting electrolytes for solid oxide fuel cells is actively in progress. Despite the intensive research activities regarding electrolytes with perovskite/fluorite structures, the search for other structural alternatives is of paramount importance. In this study we focus on a novel material with significantly improved properties for the electrochemical purposes. The two-layered BaNd₂In₂O₇ perovskite with a Ruddlesden–Popper structure was investigated as a protonic conductor for the first time. In detail, its local structure, water uptake, and the ionic (O²⁻, H⁺) conductivity were comprehensively studied. The nature of rare-earth elements (M = La, Nd) in the structure of BaM₂In₂O₇ on the structural and transport properties was revealed. The presented analysis showed that the composition of BaNd₂In₂O₇ is nearly pure proton conductor below 350 °C. This work opens up a new way in the design of protonic conductors with double-layered perovskite structure.     

Fabrication of Ga2O3 Schottky Barrier Diode and Heterojunction Diode by MOCVD

In this article, we reported on a Ga₂O₃-based Schottky barrier diode and heterojunction diode from MOCVD. The Si-doped n-type Ga₂O₃ drift layer, grown by MOCVD, exhibited high crystal quality, flat surfaces, and uniform doping. The distribution of unintentional impurities in the films was studied. Then nickel Schottky barrier diode and p-NiO/n-Ga₂O₃ heterojunction diode were fabricated and measured. Without any electric field management structure, the Schottky barrier diode and heterojunction diode have specific resistances of 3.0 mΩ·cm² and 6.2 mΩ·cm², breakdown voltages of 380 V and 740 V, thus yielding power figures of merit of 48 MW·cm⁻² and 88 MW·cm⁻², respectively. Besides, both devices exhibit a current on/off ratio of more than 10¹⁰. This shows the prospect of MOCVD in power device manufacture.     

Insight into Point Defects and Complex Defects in β-Mo2C and Carbide Evolution from First Principles

In this paper, first principles method was adopted to investigate the point defects, Vanadium-related defects and defect combinations (vacancy (V), substitutional (S) and/or interstitial (I)) in molybdenum β-Mo₂C and explore the use of first principles calculation data in analysing the link between different carbides and the effects of doping elements. Supercell models with different defect types were established and optimized, and the formation energy data of defects was developed. The structure evolution during the optimization process is analysed in detail to establish the main characteristics of changes and the relevant electronic properties. The data for different types of intrinsic defects and combined defects complexes was developed and key results is analysed. The results show that carbon vacancy (V_C) is stable but does not inevitably exist in pure β-Mo₂C. Interstitial site II is a very unstable position for any type of atoms (Mo, V and C), and analysis of the structure evolution shows that the atom always moves to the interface area near the interstitial site I between two layers. In particular, a C atom can expand the lattice structure when it exists between the layer interfaces. One type of the defects studied, the substitution of Mo with V (designated as ‘S_V-Mo’), is the most stable defect among all single point defects. The data for defect complexes shows that the combination of multiple S_V-Mo defects in the super cell being more stable than the combination of other defects (e.g., ‘V_Mo+I_C’, ‘S_V-Mo+V_C’). The data with increasing S_V-Mo in (Mo, V)₂C system is developed, and typical data (e.g., formation energy) for Mo-rich carbides and V carbides are correlated and the potential of the data in analysing transition of different carbides is highlighted. The relevance of using first principles calculation data in the studying of V-doping and the complex carbides (V- and Mo-rich carbides) evolution in different materials systems and future focus of continuous work is also discussed.