Ni–Zn hydroxide-based bi-phase multiscale porous nanohybrids : physico-chemical properties

Please read abstract in the article.The Algerian minister programhttps://link.springer.com/journal/132042020-05-25hj2020Physic

Synthesis of high-purity polycrystalline MAX phases in Ti–Al–C system through Mechanically Activated Self-propagating High-temperature Synthesis

International audienceTernary MAX phase compounds were synthesized using an alternative route called MASHS (Mechanically Activated Self-propagating High-temperature Synthesis). This original process combines a short duration ball milling (MA) of reactants (Ti, Al, C) with a self-sustaining combustion (SHS). The particle size evolution of the powder mixture during Mechanical Activation was monitored using XRD profile analysis. The effect of Al-excess was also discussed. XRD and SEM analyses have proved that the activation of the reaction kinetics must be accompanied by a decrease in the overall exothermicity in order to synthesize pure Ti–Al–C MAX phases by MASHS

Lithography-free synthesis of nanostructured cobalt on Si (111) surfaces: structural and magnetic properties

We illustrate the concept of lithography-free synthesis and patterning of magnetic cobalt in the nanometric scale. Our elaboration method allows fabricating 2D architectures of cobalt and cobalt silicide onto silicon (111) surfaces. A continuous cobalt layer of 1, 3 and 10 nm thickness was first deposited by using thermoionic vacuum arc (TVA) technology and then, thermally annealed on vacuum at temperatures from 450° C to 800° C. Surface structure was analyzed by atomic force and field emission-scanning electron microscopies. Above 750° C, regular triangular shape cobalt nanostructures are formed with pattern dimensions varying between 10 and 200 nm. Good control of shape and packing density could be achieved by adjusting the initial thickness and the substrate temperature. Magnetic properties were investigated by means of vibrating sample magnetometer (VSM) technique. The evolution of the coercive field versus packing density and dimensions of the nanostructures was studied and compared to micromagnetic calculations. The observed nanostructures have been modelled by a series of shapes tending to a fractal curve

Synthesis and characterization of the bioactive ternary SiO2-CaO-P2O5 Bioglass

In this paper, we present our results on the synthesis and characterization of silicon dioxide or silica calcium oxide and phosphorus pentoxide (SiO2-CaO-P2O5) glass by means of the sol-gel method where previous works have used tetraethyl orthosilicate (TEOS) as SiO2 precursor, but here we are using the commercialized aerosol SiO2. Indeed, our synthesis of this gel-glass nanocomposite was carried out using the aerosol SiO2, calcium nitrate tetrahydrate (CaNO3.4H2O) and sodium hydrogenphosphate (Na2HPO4) as precursors of SiO2, CaO and P2O5 respectively. The characterization was carried out by infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM) to study their chemical bonding, structural and morphological properties of the resulting amorphous glass. These techniques conducted us to detect the chemical modifications induced by modifying the Ca/P molar ratio. In addition, the thermal properties of the synthesized gel-glass materials were studied using thermogravimetric and differential thermal analysis (TG/DTA). The results revealed that the glass transition temperature is around 600degC, with the aim to convert them into ceramic powders through calcinations treatment. The results gave us porous bioactive materials that can be suitable for many applications such as prolonged-release drug or bone tissue repairing.nbspnbs

CNTs’ array growth using the floating catalyst-CVD method over different substrates and varying hydrogen supply

International audienc

Study on the Synthesis and Structural Characterization of the Cermets TiC/Fe by Self-Propagating-High-Temperature and by Thermal Explosion

International audienceA study of the TiC/Fe cermets produced by self-propagating high-temperature synthesis and by thermal explosion with various quantities of added iron was performed. It was established that both experimental and calculated adiabatic temperature of combustion and the propagation velocity of the reaction front decrease with the addition of iron in the reactants. The addition of iron was optimized at 30 wt % to ensure the stability of the propagation. The products were characterized by X-ray diffraction (XRD); the reaction seems to start at the surface of the solid titanium particle and to proceed by solid-state diffusion of iron and carbon to form TiFe and TiC/Fe cermets composite. The evolutions of the phases, size, and density of TiC grains during both kinetics reactions were highlighted by X-rays diffraction, optical and scanning electronic microscopy equipped with microindentation and energy-dispersive X-ray spectroscopy, respectively

Properties of ZnO thin films deposited on (glass, ITO and ZnO:Al) substrates

International audienceZnO thin films were deposited on glass, ITO (In2O3; Sn) and on ZnO:Al coated glass by spray pyrolysis. The substrates were heated at 350 °C. Structural characterization by X-ray diffraction (XRD) measurements shows that films crystallize in hexagonal structure with a preferential orientation along (0 0 2) direction. XRD peak-shift analysis revealed that films deposited on glass substrate (-0.173) were compressive, however, films deposited onto ITO (0.691) and on ZnO:Al (0.345) were tensile. Scanning electron microscopies (SEM) show that the morphologies of surface are porous in the form of nanopillars. The transmittance spectra indicated that the films of ZnO/ITO/glass and ZnO/ZnO:Al/glass exhibit a transmittance around 80% in the visible region. An empirical relationship modeled by theoretical numerical models has been presented for estimating refractive indices (n) relative to energy gap. All models indicate that the refractive index deceases with increasing energy band gap (Eg)

Tartrazine removal from water using functionalized multiwall carbon nanotubes

This investigation presents the advantages and limitations of tartrazine azo dye sorption on oxygen functionalized multiwalled carbon nanotubes (O-MWCNTs) synthesized by catalytic-CVD technique in LEREC laboratory, Algeria. Our adsorbent was characterized by FESEM, HR-TEM micrographs, Raman spectroscopy, ATG, XPS and specific surface area measurements (SBET). The effects of different operational parameters like contact time, initial concentration of tartrazine, adsorbent amount, pH and temperature on the sorption processes were studied in batch mode. Experiments showed that the O-MWCNT was efficient for the removal of tartrazine and the equilibrium can be reached in 60 min. The removal efficiency was found to be dependent on the initial dye concentration and there is no sig-nificant effect of temperature on the adsorption process. Also, acidic pH was found to be favorable for dye removal, while the adsorption capacity decreases with the O-MWCNTs amount. For comparison, a similar study has been performed with a commercial activated carbon (CAC) and it was found out that the functionalized MWCNT has a shorter equilibrium time and higher dye adsorption capacity than CAC, so that O-MWCNTs can be considered as potential adsorbents for dye removal from wastewater. The models of Langmuir and Freundlich isotherms are applicable to describe the process of tartrazine adsorption on the O-MWCNTs and also on the CAC conventional adsorbent.The Algerian-MHESRhttp://www.deswater.com/home.phphj2017Physic

Combustion Synthesis of PrBa₂Cu₃O₇−δ and YBa₂Cu₃O₇−δ cuprate materials

International audiencePrBaCuO and YBaCuO cuprate materials were prepared from copper, barium peroxide, and yttrium/praseodymium oxide by SHS and standard solid-state synthesis. SHS reactions were carried out using relatively large copper particles (< 63 im) to obtain small product samples (13 mm in diameter). High ambient temperature was used to stabilize a combustion front in the ignited pellets. Explored was the effect of copper particles size, starting density, and ambient temperature on phase evolutions in synthesized materials