Atomic relaxation of Ag and Cu on fcc(100) and (110) surfaces

In this work we investigated the atomic relaxation in copper and silver substrates. The system surfaces are oriented following (100) and (110) directions. The  relaxation and the bond length variation are only by the mutual atomic interaction. The all calculations are made at zero Kelvin in order to neglect the thermic vibration of the substrate atoms. The (100) surfaces are more compact than (110) ones, which is clearly observed in the inter-layer relaxation rate. On the other hand, the investigation of the adatom relaxation in the case of eterosystems (Cu/Ag) reveals that Cu adatom tends to penetrate through the surface which corresponds to the exchange process. In contrast, the Ag adatom on Cu surface attempts to be far from the surface giving a preferential occurrence to the jump process on the surface. This finding is confirmed by the binding strength or binding energy calculations where we have found (for (100) surface as example) that Cu-Ag is 2.30 and 2.09 eV for Cu/Ag and Ag/Cu, respectively

Structure refinement, EPR, Specific magnetic heat and magnetic properties of ZnMnP2O7 diphosphate

The structure of the diphosphate ZnMnP2O7 is determined on powder by the Rietveld method. It is of monoclinic symmetry C2/m. The cell parameters are: a = 6.6141(3) Å, b = 8.4366 (3) Å, c = 4.5305(2) Å and b= 103.948(2) °. The structural framework is built by MO6 octahedron planes where M is a mixed site statistically occupied by Zn2+ and Mn2+ ions. These planes are parallel to the crystallographic plane (001) and are linked together by sheets of P2O74- groups.The value of the paramagnetic temperature Qp is -4 K, which proves that the interactions are antiferromagnetic . The magnetic specific heat of this compound has a symmetric maximum at T = 5.3 K less acute compared to that of Mn2P2O7 of isotypic structure which is of ltype. This behavior change  can be explained by the interruption of three-dimensional interactions between Mn2+ ions which become limited to  2D order when 50% of these ions are replaced by Zn2+ ions

Investigation of superfast deposition of metal oxide and Diamond-Like Carbon thin films by nanosecond Ytterbium (Yb+) fiber laser

Metal oxide (MOx, M: titanium, magnesium) and Diamond-Like Carbon (DLC) thin films were synthesized by Pulsed Laser Deposition (PLD) at room temperature and low vacuum of 2 Pa for MOx and vacuum of 4 x 10(-3) Pa for DLC films. A fiber based Ytterbium (Yb+) laser operating in the nanosecond regime at a repetition rate of 20 kHz was used as an ablation source. Dense and smooth thin films with a thickness from 120 to 360 nm and an area of up to 10 cm(2) were deposited on glass and stainless steel substrates at high growth rates up to 2 nm/s for a laser intensity of 10-12 J/cm(2). The thin films synthesis was compared for two fiber laser modes of operation, at a repetition rate of 20 kHz and with an additional modulation at 1 kHz. The morphology, chemical composition and structure of the obtained thin films were evaluated using optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Raman spectroscopy. The morphology of the MOx thin films and the deposition rate strongly depend on the fiber laser mode of operation. Very smooth surfaces were obtained for the metal oxide thin films deposited at lower deposition rates in the modulation mode at 1 kHz. The effect of the substrate on the DLC film structure was studied. The films deposited on dielectric substrates were identified as typical tetrahedral (ta-C) DLC with high sp(3) content. DLC films on metal substrates were found typical a-C amorphous carbon films with mixing sp(2)/sp(3) bonds

TiO₂ Nanoparticles Prepared by Sol-Gel Method for Anode Application in Lithium-Ion Batteries

TiO 2 nanoparticles are prepared via sol-gel method using titanium tetraisopropoxide (TTIP) as a precursor under refluxing and controlled pH. It is found that pure anatase phase is obtained with pH 10. Further characterization studies are carried out on pure nanoparticle anatase phase by XRD, SEM, and transmission electron microscope (TEM). Their electrochemical performances as anode material in lithium-ion batteries are investigated by cyclic voltammetry, galvanostatic cycling, and rate capability measurements. A high discharge capacity of 321 mAh/g (vs. 335 mAh/g theoretical) is achieved at 1C rate. After the first galvanostatic charge/discharge cycle, voltage profiles show plateaus at 1.75 and 1.95 V versus Li at discharge and charge, respectively. High Coulombic efficiency (>99%) is maintained after 300 cycles, which makes anatase TiO 2 nanoparticles prepared by sol-gel method, a very promising material for anode application in lithium rechargeable batteries

Wet synthesis of high purity crystalline urea phosphate from untreated Moroccan industrial phosphoric acid

The phosphorus-nitrogen fertilizer family improves the availability of phosphorus and nitrogen for efficient crop growth. Urea phosphate 17-44-0 (N-P2O5-K2O%) is considered as a binary fertilizer characterized by its high purity and it is easily soluble in water. In addition, urea phosphate can be used in other fields as a high-quality food additive, finishing agent for metals and fermentation food. As a fertilizer, it is suitable for alkaline soils.In this work, a new process for the synthesis of urea phosphate by the wet route is developed. It consists in directly producing crystalline urea phosphate by the chemical reaction between Moroccan industrial phosphoric acid (54 % P2O5) and solid urea (46 %). The synthesis is carried out by mixing the solid urea with a stoichiometric amount of untreated Moroccan industrial phosphoric acid. The chemical reaction is complete for optimal conditions which are a temperature of 50 °C and a duration of 90 min. After cooling, the urea phosphate crystals are formed without any additional treatment and are easily recovered. Analysis of the residual liquor after recovery of the urea phosphate crystals confirms that the majority of impurities which may be harmful to the environment pass into the liquid phas

Equilibrium and kinetics of nitrate removal by protonated cross-linked chitosan

Nitrate, contained in surface or groundwater, can be removed by sorption on protonated cross-linked chitosan gel beads. The sorption capacity is pH-dependent and large enough to meet the standard of drinkable water. The isothermal equilibrium curves are straight lines, which implies that the removal is independent of the initial concentration. The main reactive process, which probably depends on the secondary ammonium groups, involves the total bead volume and not only its surface. If required, the sorption capacity is easily recovered by increasing the pH to 12. The main competitor is fluoride but, even in its presence, the sorption capacity of nitrate remains significant. The sorption kinetics, which can be represented by a mass transfer equation, is not limited by pore or by film diffusion. WaterSA Vol.27(1) 2001: 9-1

Magnetic approach in some mixed Cobalt (II) hydroxynitrates compounds

Among layered compounds, the transition metal hydroxynitrates M(OH)$_{2\hbox{-}{\rm x}}$(NO$_{3})_{\rm x}$.nH$_{2}$O (with M= Co, Ni,Cu) are still currently investigated, since they are good precursors for the synthesis of simple or mixed metal oxides with interesting catalytic and electronic properties.From a structural point of view, the hydroxynitrates derive from the CdI$_{2}$ type stucture of M (OH)$_{2}$. They can be described as 2D triangular arrays of metal ions with large interplanar distances, and accordingly, they are good candidates for studying bidimensional magnetic systems. Knowing that from a magnetic point view, Co(OH)$_{2}$ and Co$_{2}$(OH)$_{3}$(NO$_{3})$ were shown to be a genuine examples of layered ferromagnetic systems, with the occurrence of 3d antiferromagnetic order at nearly the same temperature ; we report in this paper the preparation and magnetic properties of layered cobat mixed metal(II) hydroxynitrates CoM(OH)$_{3}$(NO$_{3})$ (M= Cu, Ba) hydrated or no which display, according to the metal ion, either ferro or antiferromagnetic interlayer interactions. We discuss the interest in these compounds named hybrid organic-inorganic compounds for the stabilizing ferromagnetic interactions

Effect of fillers size on the dielectric and piezoelectric characteristics of a piezoelectric composite

Recent trends in electromechanical conversion using alternative materials, have demonstrated the advantages of using piezoelectric composites for energy generation. There have been several papers on ceramic/polymer composites in which the fillers have high piezoelectric constant. Basically, the energy harvested depends on the proportion of the piezoelectric properties of composite. The fillers size within the composites is also an important criterion of the composites properties. Thus, in this paper 0–3 composites, made of lead zirconate titanate (PZT) ceramic powder and polyurethane (PU) were prepared. Different sizes of ceramic grains were used: grains with average size of 10 μm, size under 80 μm and size under 100 μm. Sizes of the PZT grains was determined according to the homogenization efficiency of the composite. Piezoelectric (piezoelectric coefficient d33) and dielectric properties (dielectric constant) were investigated. They have shown an interesting improvement with the increasing grains size up to 20 pC/N and 100, respectively. In order to understand the composite behavior on the microscopic scale, a simulation was carried out by mean of a finite element method (FEM) software. Finally, an estimation of the harvested voltage was modeled according to the grains size

Structure and conductivity of lithiated vanadates LiMVO4_{4} (M = Mn, Co, Ni)

The LiMVO$_{4}$(M = Mn, Co, Ni) vanadates have been synthetized and characterized by X-ray diffraction, Raman and FTIR spectroscopy. Conductivity measurements by impedance spectroscopy show the correlation between structure and transport mechanism