Research on Microstructure and Growth Mechanism of Different Primary Silicon in Hypereutectic Aluminum Alloy

The as-cast microstructure of a typical hypereutectic Al-25Si alloy was studied, and the growth mechanism of different primary silicon phases was analyzed. The results show that the as-cast microstructure phase composition of the alloy is mainly primary silicon and eutectic silicon. Primary silicon is mainly petal-like, massive and other complex polyhedrons, and there are a lot of cavities, cracks and other defects in the interior and boundary; Eutectic silicon is coarse and long needle-like, and the distribution is relatively messy, which seriously deteriorates the mechanical properties and cutting performance, and hinders the further application of the alloy in the field of lightweight pistons. Petal-shaped primary silicon is grown by combining five tetrahedral crystal nuclei in the melt into a decahedron, while bulk primary silicon is mainly caused by the unbalanced aggregation of impurity elements. And these two types of silicon phase growth methods are related to the twin groove growth mechanism, which is the result of a combination of multiple mechanisms.

Preparation of tetrahedral Ag3PO4 and mechanism of photocatalytic degradation of RB-42

In this study, silver nitrate and sodium phosphate were used as raw materials to prepare highly active Ag3PO4 photocatalyst with visible light response. The structure, morphology and composition of the samples of the obtained samples were characterized by XRD, SEM and XPS. Moreover, the photocatalytic activity was also investigated by means of degradation of reactive black-42(RB-42) in water. The effect of solution on photocatalytic degradation of RB-42 was investigated through the analysis of photocatalytic degradation kinetics. The results were showed that the nano Ag3PO4 is tetrahedral crystal. exhibit excellent efficient photocatalytic activity for the degradation of RB-42. when the addition of concentration of RB-42 was 10 mg·L, pH was 5.8 and the amount of catalyst was 50mg·L, the obtained sample removal efficiency was 80.7% under visible light irradiation. In addition, free radical capture experiments showed that •OH− was the main active substance in the reaction system.

Predicting the Number of Graphene-Like Layers on Surface for Commercial Fumed Nanodiamonds with Raman Spectra and Model Calculations

Nanoscale carbon materials have a broad range of applications in the field of surface and material sciences. Each vibration mode of a Raman and Fourier transform infrared (FT-IR) spectra corresponds to a specific frequency of a bond in the core and surface of the crystal, thus it is highly sensitive to morphology, implying that every band is sensitive to the orientation of the bonds and the atomic weight at either end of the bond. Accordingly, in this study we apply transmission electron microscope (TEM), Raman spectroscopies, and model calculations to study the relative content of carbon–carbon (C–C) bonds to the anhydrous and weakly aggregated elementary nanoscale carbon particles of detonation nanodiamonds. One point of the Raman bands at approximately 1300 cm−1 established that there are highly uniform C–C bonds in a tetrahedral crystal field environment not unlike that of diamonds. Another point at approximately 1600 cm−1 would be a hexagonal graphene-like sheet. By analyzing the relative content of carbon bonds using the area of intensity of the Raman peaks and a simulation of crystal morphology, we suggest that the number of graphene surface layers would be monolayers in nanodiamonds, comprising two kinds of C–C bonds, one being sp3 bonds of diamond in the core and the other being sp2 bonds of graphene on the surface.

Role of precursors mixing sequence on the properties of CoMn2O4 cathode materials and their application in pseudocapacitor

In this study, the effect of oxygen vacancy in the CoMn2O4 on pseudocapacitive characteristics was examined, and two tetragonal CoMn2O4 spinel compounds with different oxygen vacancy concentrations and morphologies were synthesized by controlling the mixing sequence of the Co and Mn precursors. The mixing sequence was changed; thus, morphologies were changed from spherical nanoparticles to nanoflakes and oxygen vacancies were increased. Electrochemical studies have revealed that tetragonal CoMn2O4 spinels with a higher number of oxygen vacancies exhibit a higher specific capacitance of 1709 F g−1 than those with a lower number of oxygen vacancies, which have a higher specific capacitance of 990 F g−1. Oxygen vacancies create an active site for oxygen ion intercalation. Therefore, oxidation–reduction reactions occur because of the diffusion of oxygen ions at octahedral/tetrahedral crystal edges. The solid-state asymmetric pseudocapacitor exhibits a maximum energy density of 32 Wh-kg−1 and an excellent cyclic stability of nearly 100%.

Modeling of Acoustic Processes in Solids Based on Particle Interaction

An algorithm for the numerical propagation of acoustic waves in solids has been developed. The algorithm is based on the particles interaction model of in a tetrahedral crystal lattice. Numerical integration of Newton's equations in the calculation of particle trajectories is applied. The possibility of numerical modeling of wave diffraction processes on heterogeneities is shown. The resonant phenomena are observed in simulation of acoustic oscillations for an ultrasonic waveguide by means of proposed algorithm.

Electronic structure and magnetic properties of Zn1−xTMxTe (TM = Fe, Co, Ni) for 0 ≤ x ≤ 1 alloys

In this study, we employed Wu–Cohen generalized gradient approximation (WC-GGA) to calculate the structural stability, whereas the modified Becke and Johnson local-density approximation (mBJLDA) functional has been used to determine the electronic and magnetic properties of [Formula: see text] [Formula: see text] alloys in the [Formula: see text] range 0–1. Structural optimization in paramagnetic (PM), ferromagnetic (FM) and anti-ferromagnetic (AFM) orders has been done to check the state stability of the doped alloys and then verified with the calculated values of enthalpy of formation [Formula: see text]. The erections of enthalpies were negative which gave the evidence of structural stability in FM phase for all three alloys. Our calculated values of equilibrium lattice constants decreased by increasing the TM concentration, in [Formula: see text] [Formula: see text] alloys. We found ferromagnetism caused by the spin polarization of electron in TM-[Formula: see text] states in the studied alloys by analyzing the calculated band structure (BS), density of state (DOS) and magnetic moments. The calculated ferromagnetism was also explained from the Zener model. Due to the tetrahedral crystal field, the [Formula: see text]-state of TM splits into double [Formula: see text] and triple degenerate [Formula: see text] states and our calculated results show the strong pd interaction is only due to [Formula: see text]. Furthermore, we predict exchange splitting energies [Formula: see text] and [Formula: see text] and exchange constants [Formula: see text] and [Formula: see text]. Their calculated values are consistent with typical magneto-optical experiment. The magnetic moments of TM ions were reduced by increasing TM concentration in [Formula: see text] [Formula: see text] alloys, while trivial local magnetic moments at Zn and Te sites were also found.

First-principles study on the electronic and magnetic properties of the Zn0.75Mo0.25M(M = S,Se,Te)

The geometrical, electronic and magnetic properties of the Zn[Formula: see text]Mo[Formula: see text]M (M[Formula: see text]=[Formula: see text]S, Se and Te) have been studied by spin-polarized first-principles calculation. The optimized lattice constants of 5.535, 5.836 and 6.274 Å for M[Formula: see text]=[Formula: see text]S, Se and Te are related to the atomic radius of 1.09, 1.22 and 1.42 Å for S, Se and Te atoms, respectively. The Zn[Formula: see text]Mo[Formula: see text]M are magnetic half-metallic (HM) with the spin-down conventional band gaps of 2.899, 2.126 and 1.840 eV, while the HM band gaps of 0.393, 0.016 and 0.294 eV for M[Formula: see text]=[Formula: see text]S, Se and Te, respectively. At the Fermi level, the less than half-filled Mo-[Formula: see text] orbital hybridizated with the less M-[Formula: see text] orbital contributes only spin-up channel leading Zn[Formula: see text]Mo[Formula: see text]M an HM ferromagnetism. The tetrahedral crystal field formed by adjacent three Zn atoms and one M atom splits the spin-up channel (majority spin) of Mo-[Formula: see text] orbital into three-fold degenerate [Formula: see text] states at the Fermi level and double degenerate [Formula: see text] [Formula: see text] states below the Fermi level. The exchange splitting energies of the Zn[Formula: see text]Mo[Formula: see text]M are −2.611, −2.231 and −1.717 eV for M[Formula: see text]=[Formula: see text]S, Se and Te, respectively. The results provide an useful theoretical guidance for Zn[Formula: see text]Mo[Formula: see text]M applications in spintronic devices.

Synthesis and Thermal Characterization of Co-Doped ZnO Nanocomposites Prepared by Sol-Gel Method

Polyparaphenylene/Zn0.925Co0.075O(PPP/Zn0.925Co0.075O) nanocomposites were synthesized by using a sol-gel method and their thermal conductivity properties were measured. The XRD pattern of Zn0.925Co0.075O shows the single phase wurtzite structure. The SEM images show that the lighter-contrast area is PPP and the dark-contrast area is the polycrystalline of Zn0.925Co0.075O. The increase in the band edge is a clear indication for the incorporation of Co inside the ZnO lattice. The observation of three additional absorption peaks provided evidence that the 3d7 high-spin configuration of Co2+ under the tetrahedral crystal field was probably formed by neighboring O2- ions. With the increase of the PPP content, the thermal conductivity of nanocomposite samples is smaller than those of pure Zn0.925Co0.075O. Due to the high density of interfaces and grain boundaries present in the nanocomposites, the scattering of phonon across a broad wavelength spectrum was enhanced. This suppressed the lattice thermal conductivity of the nanocomposites significantly.

Microstructure and IR Studies of Ag Ions-Zeolite

Ag-zeolite crystal have been obtained through immersing Na86–X (Na86[(AlO2)86(SiO2)106]46.2H2O) zeolite in 0.1 M AgNO3solution for 12 h. Information on the interaction of Ag+ cations with framework oxygens was obtained by analyzing of IR spectra. SEM and EDS reveal that the microstructure of zeolite is tetrahedral with some little cluster between tetrahedral crystal and Ag element exists in the crystal.