Defect and Diffusion Forum Vol. 406

Abstract: The present work aims at the study of the dry disc pion contact and the complex phenomenon of the wear as well as the sliding friction of our sample elaborated by a hot isotactic compression and the pion. This study consists in determining the coefficient of friction and the influence of the tribological parameters on this phenomenon as well as determining the loss of mass and the wear rate of study sample. In order to enhance the assurance of the validity of the results of tribological study of Ni-Cr-B-Si-C-W alloy in laboratories and compare that to the tribological conditions in reality and industries. This work presents the results of the new approach to compares the wear behavior of the sample between a theoretical study (tribometer)and another in service (a test bench) that reproduces approximately the same conditions as the tribometer (normal load, sliding speed and distance traveled) by measuring the loss of mass and wear rate.

Abstract: The effect of La substitution on the structure and its modulation in samples with a nominal composition of Bi₂Sr_2-xLa_xCaCu₂O_8+d where 0≤x≤0.3 superconducting phase was investigated. The X-ray powder diffraction (XRPD) results showed an almost pure Bi-2212 phase, confirmed by the estimated amount of element concentration using dispersive energy X-ray spectroscopy (EDX). Scanning electron microscopy (SEM) micrographs showed a decrease of both crystallite size and connectivity when Lanthanum concentration increases. Le Bail refinement using the Jana2006 program gives a very good value of goodness of fit (GOF) factor. Also, the refinement reveals that for x=0.3 the orthorhombic cell transforms to the tetragonal one and the modulation vector q increases when increasing La concentration.

Abstract: In the present contribution, structural, dynamic, and some thermodynamic properties of the III-Antimonides are studied using the density-functional perturbation theory (DFPT) within the local density approximation (LDA) in combination with the harmonic approximation Our results for the structural properties such as the lattice constant and the bulk modulus were found to agree well with the previous theoretical and experimental works. We have also calculated the phonon dispersion relation, and we found that our phonon calculations show that these compounds are dynamically stable in the zinc blende phase moreover our results of the optical and acoustic phonon frequencies at the high symmetry points Γ, X and L are in good agreement with the available theoretical and experimental data. In addition, the thermodynamic properties, including the free energy, internal energy, entropy, and the heat capacity at constant volume were predicted and discussed.

Abstract: First, the metallic oxides of PbO, TiO2 and ZrO2 were mixed following (2, 1, 1) molar mass respectively. Then 4 samples were separated (S1, S2, S3 and S4). the first one S1 was subjected to calcination treatments at 600, 700 and 800 °C however, the S2 was treated at 700 °C only, the S3 at 800 °C and S4 at 850 °C. The X ray diffraction of the samples reveals important difference in the phases obtained, at 600 °C the quadratic riche phase of PbTiO3 was mainly observed on sample S1, after the treatment at 700 °C and 800°C, the same XRD patterns were obtained with the same peaks positions and the relative intensity. However the S2 revels different pattern from S1 at 700 °C relative to the formation of the Pb(Zr0.75, Ti0.25)O3 Rhombohedral riche phase. The S3 XRD results reveal also different pattern from S1 at 800 °C relative to the formation of Pb (Zr0.58, Ti0.42) O3 near the Morphotropic phase boundary (MPB) and the S4 confirm these finding. Thin films grown from the S1 and S4 used as target in the RF sputtering system, show important difference in the PZT stoichiometry obtained which is relative to Pb (Zr0.44, Ti0.56) located in the quadratic riche phase and Pb (Zr0.52, Ti0.48) O3 near the MPB respectively.

Abstract: The behaviour of a corrosion inhibitor based on proplolis extract via an iron alloy immersed in an electrolyte containing ethylene glycol water in NaCl 0.1 M was evaluated by a stationary technique not destructive which is the technique of electrochemical impedance. The diameter of the Nyquist curves increases with the increase of the concentration of propolis extract and it reaches an optimum concentration at 1.25 g / L, the maximum surface coverage percent at this concentration is 71.98% .The activation parameters reveal that the inhibitor molecules on iron surface are absorbed by physisorption and a chimisorption and obey Langmuir isotherm adsorption. These results were supplemented by Scanning electron microscopy (SEM) and (EDX) spectrum of chemical composition. The metal solution interface is simulated as a physical model by using electrochemical impedance spectroscopy (EIS). Keywords: Iron Alloy, Propolis extract, ethylene glycol;, Lamgmuir isotherm, Electrochemical impedance Spectroscopy (EIS).

Abstract: ZnS nanocrystals were embedded in a KBr single crystal matrix using the Czochralski growth technique. The X-ray diffraction, FT-IR and optical spectroscopy revealed the incorporation of ZnS nanocrystals. A blue shift of the absorption edge of the obtained samples has been observed, indicating the quantum confinement effect. The optical band-gap is estimated to be about 4.67 eV. Two excitonic peaks appeared at 300.4 nm and 271 nm. The average nanocrystal size was derived from the optical spectra. Annealing led to a shift in the absorption edge towards longer wavelengths and an increasing of the emissions intensity. Raman lines of the nanoparticles are broader and frequency-shifted compared to those of the bulk crystals. These results show that KBr is a good matrix-host of ZnS nanocrystals, and that the elaborated samples can be used for important technological applications.

Abstract: Zinc oxide codoped with Fluorine and Cobalt thin films (FCZO) were successfully synthesized on heated glass substrate at 380 °C by spray pyrolysis technique. The influence of doping and codoping on the structural, optical and electrical properties were investigated. X-ray diffraction results showed that the undoped and FCZO films exhibit the hexagonal wurtzite crystal structure with a preferential orientation along [0 0 2] direction. No secondary phase is observed in FCZO films. The optical transmittance of Co doped ZnO thin films reduces up to 80 % as compared to undoped ZnO thin film in the visible region. We have observed three absorption bands at 568, 608 and 659 nm which can be attributed to the d-d transitions of tetrahedrally coordinated Co²⁺ ion in the high spin state. The band gap was found to be increasing in the range of 3.26-3.39 eV with Co doping whereas it decreases for higher doping of Co concentration.

Abstract: Ni-TiO₂ nanocomposite coatings were fabricated on mild steel surface by pulsed direct current (PC) electrodeposition. This process was carried out in pulsed current at (1, 10, 50) Hz and a duty cycle (25%, 50%, 75%) respectively, at a minimum current density of 0 & high current density of 4 A/dm². In this work the properties of nanocomposite films were investigated using scanning electron microscopy (SEM), Vickers microhardness measurements and Tafel polarization tests. The composition of the electrodeposits was analyzed by energy dispersive X-ray analysis (EDX). It was found that the coated surface contained at maximum 16.30 % Ti and 35.48 % O. XRD studies revealed [111] preferred orientation. Hardness increased from 560.4 Hv for Ni-TiO₂ (F=10 Hz, DC=75 %) nanocomposite coating to 645.7 Hv for Ni-TiO₂ (F=10 Hz, DC=25 %) nanocomposite coating. The corrosion resistance of Ni-TiO₂ coatings was evaluated by potentiodynamic polarization studies in 3.5 % NaCl solutions. The Pulsed current offer composite coatings with uniform surface, high microhardness and enhanced corrosion resistance significantly for F=10Hz and DC=25 %.

Abstract: The subject of this work is to evaluate the influence and adhesion degree of different coating layers deposited on a ductile cast iron substrate by two different methods, thermal spraying and welding with and without use of an interlayer. Microstructures of different zones and interfaces of coated specimens are investigated using optical microscope and scanning electron microscope SEM. Also, the mechanical behavior was evaluated by tensile test. It is found that when stainless steel thermal spraying coating onto the ductile cast iron substrate, the use of the nickel-based interlayer Ni allowed us to mitigate the disadvantages of cracking at the interface. This is due to the mechanical effect of nickel plasticity. In the case of coating by welding, the use of nickel-based buttering ENi-CI allowed us to reduce the diffusion of graphite to stainless steel, resulting in a reduction in the formation of harder alloy carbides. Finally, the mechanicals tests in particular the tensile test shows that the coating by welding is effective but causes a structural hardening; on the other hand the coating realized by thermal spraying does not really present sufficient adhesion.

Abstract: TiN coatings with a thickness of 2 μm were deposited using the magnetron sputtering has developed rapidly over the last decade in such a way that it has become an established process of choice for the deposition of a wide range in various applications for different domains as it gives excellent performance in many aspects. In view of this, we have deposited the TiN coatings by magnetron sputtering using Ti target at different nitrogen content to study the influence of the nitrogen content on the mechanical properties and tribological behaviors of the TiN coatings were systematically investigated using nanoindentation and a pin-on-disk tribometer. Nanoindentation results shows that the hardness and Young's modulus of the TiN coatings increase with increasing N content in the coatings.Wear test results indicate that the wear rate and friction coefficient of the XC100 steel substrate were significantly reduced by deposition of the TiN coatings, and the tribological behaviors of the TiN coatings are strongly dependent on the nitrogen content in the coatings.