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

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