Superlight pairs in face-centred-cubic extended Hubbard models with strong Coulomb repulsion

The majority of fulleride superconductors with unusually high transition-temperature to kinetic-energy ratios have a face-centred-cubic (FCC) structure. We demonstrate that, within extended Hubbard models with strong Coulomb repulsion, paired fermions in FCC lattices have qualitatively different properties than pairs in other three-dimensional cubic lattices. Our results show that strongly bound, light, and small pairs can be generated in FCC lattices across a wide range of the parameter space. We estimate that such pairs can Bose condense at high temperatures even if thelattice constant is large (as in the fullerides).

Microstructural Stability of the CoCrFe2Ni2 High Entropy Alloys with Additions of Cu and Mo

New High Entropy Alloys based on the CoCrFe2Ni2 system have been developed by adding up to 10 at. % of Cu, Mo, and Cu + Mo in different amounts. These alloys showed a single face-centred cubic (FCC) structure after homogenization at 1200 °C. In order to evaluate their thermal stability, aging heat treatments at 500, 700, and 900 °C for 8 h were applied to study the possible precipitation phenomena. In the alloys where only Cu or Mo was added, we found the precipitation of an FCC Cu-rich phase or the µ phase rich in Mo, respectively, in agreement with some of the results previously shown in the literature. Nevertheless, we have observed that when both elements are present, Cu precipitation does not occur, and the formation of the Mo-rich phase is inhibited (or delayed). This is a surprising result as Cu and Mo have a positive enthalpy of mixing, being immiscible in a binary system, while added together they improve the stability of this system and maintain a single FCC crystal structure from medium to high temperatures

Synthesis of silver nanoparticles from electronic scrap by chemical reduction

In the present research, the use of electronic waste in the synthesis of silver nanoparticles was investigated. For this purpose, electronic scraps were used as a consumable part to synthesize silver nanoparticles. The results revealed that by optimizing the time and temperature of the dissolution process using nitric acid solution up to 90%, silver can be extracted from these parts. The temperature of 60°C and the duration of one hour were determined as the optimum conditions for this phase. Afterward, the synthesis of silver nanoparticles was checked using silver nitrate solution. The results indicated that the concentration of initial silver nitrate had a significant impact on the quality of the final product so that the best conditions for the synthesis of silver nanoparticles with suitable properties were provided at 1 molar concentration. Phase studies indicated that the main phase of the synthesized silver particles had an FCC structure and no unwanted phase was observed. Ultraviolet-visible analysis of the synthesized powder revealed that the main peak for the silver nanoparticles appeared in the wavelength range of 400 to 450 nm. DLS analysis revealed that precursor's particles inside the sol were below 15 nm. Based on AFM and TEM investigations, the particles synthesized under these conditions had nanometric spherical morphology with uniform particle size distribution.

Corrosion Behavior of Cr19Fe22Co21Ni25Mo13 Alloy in 1M Nitric Acid and 1M Hydrochloric Acid Solutions

The present work studied the microstructures of Cr19Fe22Co21Ni25Mo13 alloy, and tested the polarization properties in deaerated 1M nitric acid and 1M hydrochloric solutions at different temperatures. The alloy was processed by an argon atmosphere arc-melting. Results indicated that the microstructure of Cr19Fe22Co21Ni25Mo13 alloy was a dendritic one. The dendrites of Cr19Fe22Co21Ni25Mo13 alloy were an FCC structure, and the interdendrites of Cr19Fe22Co21Ni25Mo13 alloy were a eutectic structure with two phases of FCC and simple cubic (SC). The Cr19Fe22Co21Ni25Mo13 alloy had better corrosion resistance compared with commercial 304 stainless steel in both deaerated 1M HNO3 and 1M HCl solutions. The corrosion types of Cr19Fe22Co21Ni25Mo13 alloy in both of 1M HNO3 and 1M HCl solutions were uniform corrosion.

Nitrogen under Super-Reducing Conditions: Ti Oxynitride Melts in Xenolithic Corundum Aggregates from Mt Carmel (N. Israel)

Titanium oxynitrides (Ti(N,O,C)) are abundant in xenolithic corundum aggregates in pyroclastic ejecta of Cretaceous volcanoes on Mount Carmel, northern Israel. Petrographic observations indicate that most of these nitrides existed as melts, immiscible with coexisting silicate and Fe-Ti-C silicide melts; some nitrides may also have crystallized directly from the silicide melts. The TiN phase shows a wide range of solid solution, taking up 0–10 wt% carbon and 1.7–17 wt% oxygen; these have crystallized in the halite (fcc) structure common to synthetic and natural TiN. Nitrides coexisting with silicide melts have higher C/O than those coexisting with silicate melts. Analyses with no carbon fall along the TiN–TiO join in the Ti–N–O phase space, implying that their Ti is a mixture of Ti3+ and Ti2+, while those with 1–3 at.% C appear to be solid solutions between TiN and Ti0.75O. Analyses with >10 at% C have higher Ti2+/Ti3+, reflecting a decrease in fO2. Oxygen fugacity was 6 to 8 log units below the iron–wüstite buffer, at or below the Ti2O3–TiO buffer. These relationships and coexisting silicide phases indicate temperatures of 1400–1100 °C. Ti oxynitrides are probably locally abundant in the upper mantle, especially in the presence of CH4–H2 fluids derived from the deeper metal-saturated mantle.

Particle size and convergent electron diffraction patterns of triangular prismatic gold nanoparticles

Convergent beam diffraction (CBED) patterns of nanoparticles are possible. CBED of triangular prismatic shaped Au nanoparticle with focus on diffraction pattern symmetry and forbidden reflections observed along [111] and [112] zone axes are reported in this work. It is well known that the CBED patterns of nanoparticles of 30 nm or less in size only show bright kinematical discs. The dynamic contrast with Kikuchi and sharp HOLZ lines within the bright discs, as observed in CBED of volumetric materials, is well observed in particles larger of 500 nm in size. In addition, it is shown that the 1/3[422] and 1/2[311] weak forbidden reflections observed in the [111] and [112] electron diffraction patterns of these particles do not modify the symmetry of the CBED patterns, but they disappear as the size of the particle increases. The symmetry of the CBED patterns are always observed in concordance with the space group Fm3m (No. 225) of the Au unit cell. The possible explanations for observing forbidden reflections are the incomplete ABC stacking due to surface termination and the stacking faults in the fcc structure.

Statistical Optimization of Co-stabilized Growth of Ag NPs by Liquid Plasma Interaction Method for Study of Antibacterial Activity

In this study, a plasma jet of argon gas was impinged with a solution of metal salt and stabilizers for production of silver NPs. To optimize the absorbance parameter, a simplex centroid design (SCD) was used to optimize the experiments. The combined and individual effect of stabilizers on the synthesis of Ag NPs was significant when P-value < 0.05. SCD optimization of UV results showed a sharp SPR band at 302 nm. In FTIR analysis, bond absorption at 1633 cm−1 attributed to C=O was shifted to higher wavelength due to saccharides addition. XRD analysis confirmed the FCC structure of Ag NPs having average size of 15 nm. SEM- EDX revealed the formation of spherical shaped Ag NPs with strong absorption at 3 keV confirming the presence of the Ag content. Antibacterial activity of Ag NPs was significant against both bacteria, with slightly stronger activity against Staph. aureus than Escherichia coli.

Combining the Mie-Lennard-Jones and the Morse Potentials in Studying the Elastic Deformation of Interstitial Alloy AGC with FCC Structure under Pressure

In this study, the mean nearest neighbor distance between two atoms, the Helmholtz free energy and characteristic quantities for elastic deformation such as elastic moduli E, G, K and elastic constants C11, C12, C44 for binary interstitial alloys with FCC structure under pressure are derived with the statistical moment method. The numerical calculations for interstitial alloy AGC were performed by combining the Mie-Lennard-Jones potential and the Morse potential. Our calculated results were compared with other calculations and the experimental data.

Molecular dynamics simulation of the effect of solute atoms on the compression of magnesium alloy

Magnesium alloys have a wide range of application values. To design and develop magnesium alloys with excellent mechanical properties, it is necessary to study the deformation process. In this paper, the uniaxial compression (UC) process of AZ31 magnesium alloy with different solute atom content is simulated by the molecular dynamics method. The effect of the solute atom on the uniaxial compression of magnesium alloy is investigated. It is found that solute atoms can inhibit the grain refinement of magnesium, can effectively improve the plastic strength of the alloy, can change the lattice distortion during uniaxial compression of magnesium alloy, can inhibit the generation of BCC structure, and can slow down the increase of FCC structure and dislocation density. The direction of the FCC structure diffusion is 90° to the grain boundary direction. Shockley partial dislocations are generated around the FCC structure. The direction in which the FCC structure spreads is consistent with the direction in which Shockley partial dislocations move.