Sciences des matériaux
SYNTHESE D'OXYDE CUPROUS CO DOPE PAR ELECTRODESPOSE SUR UN SUBSTRAT D'ARGENT POUR APPLICATION PHOTOVOLTAIQUE
Dans ce travail, des films minces d'oxyde cuivreux co dope ont été préparés en utilisant la technique d'électrodéposition à différents potentiels appliqués d'une solution aqueuse de sulfate cuivrique alcalin avec de l'acide lactique à 70 ° C sur des substrats d'argent. Les effets du potentiel de dépôt sur les propriétés électrochimiques, morphologiques de surface, structurelles et électriques des couches minces d'oxyde cuivreux ont été étudiés par spectroscopie à voltamogramme cyclique, DRX, MEB et UV-visible. Les mesures XRD ont indiqué que tous les films obtenus présentent une structure cubique en oxyde cuivreux avec une forte orientation préférentielle de la direction (111). Voir les détails
Mots clés : films minces, DRX, MEB
STUDY OF STRUCTURAL , OPTICAL AND ELECTRICAL PROPERTIES OF ZnO THIN FILMS PREPARED
ABSTRACTIn this work, we studied deposited Cobalt- doped ZnO thin films via dip-coatingtechnique onto glass substrate, Zinc acetate dehydrate, cobalt acetate, 2-methoxyethanol andmonoethanolamine were used as starting materials. The obtained thin films here characterizedby X-ray diffraction, UV- visible absorption, Atomic force microscopy (AFM). It is foundthat all the thin films have good crystallinity and a preferential orientation o f crystallitesalong [002] axis of ZnO with wurtzite structure. The AFM have provided the information onmorphology of this films where the size grain and average surface roughnes (Rms). Voir les détails
Mots clés : Thin films, ZnO, Cobalt, Dip-Coating, XRD, AFM, UV-Visible absorption.
TiO2 doped with nickel thin films Properties
Thin films of un-doped and Ni-doped TiO2 were synthesized by the sol–gel dip-coating technique and deposited on glass substrates, for different annealing temperatures (from 400 °C to 500 °C). The X-rays diffraction and Raman show the formation of anatase phase, we also notice that doping with Ni influence the intensity of anatase peaks and decreases of grain sizes (from 24.3 to 15.23 nm). The nanostructure Ni-doped TiO2 thin films was observed AFM, which shows that the elaborated films are smooth and dense with Rms values of about 3 nm. The calculate values of refractive index of thin films increases from 2.22 to 2.38, and reduction in transmittance and band gap with the increase in the nickel concentration. Vibrating sample magnetometer results of un-doped TiO2 thin films reveal a ferromagnetic behavior at room temperature with Ms = 0.67 10-4 emu and low content of nickel doping leads to an enhancement of the saturated magnetic moment Ms =1.11 10-3 emu. Voir les détails
Mots clés : Ni-doped TiO2, sol-gel, Thin films, TiO2 properties
Structural and magnetic properties of FeCuNi nanostructured produced by mechanical alloying
We investigated the magnetic, morphological, and structural properties of FeCuNi. The powder alloy iselaborated by mechanical alloying process for 10 h with varying the Cu content. The aims of this workare to study the effect of Ni/Cu ratio on the magnetic and microstructure properties. The crystallite sizedecreases with the increase of Ni. The reduction of crystallite size proceeds slowly until 17 nm for 30% ofNi. Coercivity and saturation magnetization increases from 105.4 Oe, 122.568 emu/g to 156.77 Oe,140.679 emu/g respectively caused by the increase of the concentration of Cu and dislocation densityas well as the decrease of the crystallite size Voir les détails
Mots clés : FeCuNi nanostructured, Mechanical Alloying, MEB, DRX, VSM
Investigation of microstructure and mechanical properties of phosphocalcic bonesubstitute using the chemical wet method
Selection of calcium phosphate base materials in reconstructive bone surgery is justified by the surprising similarities in chemical compositions with human bones. The closest to natural apatite material is the hydroxyapatite (HAp) which has a chemical composition based on calcium and pho sphate (Ca 10 (PO 4 )6 (OH)2 ). In this study, HAp is synthesized using the wet precipitation method from hydrated calcium chloride (CaCl 2 ,12H 2 O) and di-sodium hydrogen phosphate di-hydrate (HNa 2 PO4,2H 2 O). The powder is calcinated at 900°C and 1200°C in order to compare with sintered condition at 1150°C. Vickers microhardness tests and X-ray diffraction analyzes are used for the characterization of the crystalline material. Mechanical properties ( HV , σe, σ r , and K C ) and the degree of crystallinity (X c) are discussed according to heat treatment temperatures. Results indicate that heat trea ting the powder at 1200°C increased crystallinity up to 72%. At the same time, microhardness increased with temperature and even outmatched the sintered case at 1150°C. Fracture toughness is ameliorated with increasing heat treatment tempera ture by more than two folds. Voir les détails
Mots clés : Biomaterials, hydroxyapatite, chemical wet method, mechanical properties, heat treatment
Microstructure, Corrosion and Magnetic Behavior of an Aged Dual-Phase Stainless Steel
In the present work, the effect of the precipitation phenomena on corrosion and magnetic behavior of an aged dual-phase stainless steel was investigated. Aging treatment caused the precipitation of the σ phase, chromium carbides and secondary austenite, which was accompanied by the shifting of the δ/γ interfaces inside the δ ferrite grains. Aging between 700 and 850 °C strongly deteriorated the pitting corrosion resistance of the studied material. Magnetic investigation of the aged material using the vibration sample magnetic technique revealed the sensitivity of the intrinsic magnetic properties to the smallest microstructural change. This was confirmed by the Eddy current technique that led also to the evaluation of the aging-induced localized corrosion. Voir les détails
Mots clés : σ phase, aging treatment, DSS, Magnetic Properties, microstructure, Pitting corrosion
Structure, magnetic and microwave studies of mechanically alloyed powders Fe45Ni35Co20
Nanocrystalline Fe-35 wt%Ni-20 wt%Co has been prepared by using a high-energy planetary ball mill with increasing milling time from 4 to 36 h. Microstructural characterisations showed the development of an face-centred cubic nanostructured Fe-35 wt%Ni-20 wt%Co alloy with an average crystallite size of 8 nm. The magnetic investigation revealed that the nanostructures obtained from a milling time of 36 h have the highest magnetic saturation and the lowest coercive field. In addition, the hardness and the electromagnetic absorption of the Fe-35 wt%Ni-20 wt%Co alloy were found to increase with the milling time. These evolutions could be attributed to the crystallite size and the strain variations in the samples during milling. Voir les détails
Mots clés : nanostructure, magnetic, nanocristalline, Mechanical Alloying, Fe, Co
Electroless copper deposition on epoxy glass substrate for electrocatalysis of formaldehyde
In this paper, we investigated the characteristics of a structured copper (Cu) ?lm deposited on the surface of an insulating epoxy glass (EG) substrate via a facile electroless plating process. The ?lm produced by this method was found to be of high purity and has a homogeneous microstructure consisting of an assembly of numerous aggregates that vary in size from 1 to 5 mm depending on the electroless deposition time. The electrocatalytic activity of the prepared electrode was investigated for the electrooxidation of formaldehyde using cyclic voltammetry in 0.1 M NaOH solution. Results show that formaldehyde oxidation takes place at a low potential of -0.34 V with large anodic current densities. Voir les détails
Mots clés : copper, electroless plating, Formaldehyde, Oxidation, Thin films
Preparation and characterization of spinel type Zn2TiO4 nanocomposite.
Zinc orthotitanate Zn2TiO4 spinel structures have been prepared by solid state reaction in two stages. First, a mixture of ZnO and TiO2 (67% anatase+33% rutile) in a molar ratio of 2:1 was mechanically milled for 6 and 18 h, at room temperature, in a high energy planetary ball mill under argon atmosphere. Next, the ball milled powders were calcined at 900°C for 2 h, pressed into pellets and then sintered for 4 h at 1100°C in air. Phase formation, microstructure, surface morphology and optical properties were characterized by X-ray di?raction, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, atomic force microscopy and UV–visible spectro- photometery. The mechanical milling process for 6 h gives rise to the formation of nanocrystalline orthotitanate Zn2TiO4 (15.5%, =13.2 nm) in addition to unreacted rutile TiO2, anatase TiO2 and ZnO structures. As the milling process progresses up to 18 h, the volume fraction of Zn2TiO4 increases to about 44.5%. The sintered pellets exhibit a composite structure where about a small amount of rutile nanograins are dispersed into the Zn2TiO4 matrix. FT-IR and Raman results con?rm the biphasic character of the sintered pellets. The band gap energy is milling time dependent. It varies from 3.22 for pellet 6 h to 3.45 for pellet 18 h. Voir les détails
Mots clés : Mechanical Alloying, ZnO−TiO2 system, XRD, Raman spectroscopy, SEM
Dissimilar Welding between 2205 Duplex Stainless Steel and API X52High Strength Low Alloy Steel
This work purposes to investigate the microstructure and the mechanical behavior ofdissimilar metals weld between 2205 duplex stainless steel (UNS 31803) and high strength lowalloy steel API X52. The joining was produced by shielded metal arc welding process using twodifferent filler metals, the duplex E2209 and austenitic E309 grade.The microstructures of the dissimilar welded joints have been investigated by optical microscopy,scanning electron microscopy and energy-dispersive spectroscopy (EDS). The EDS analysisperformed at the API X52/weld metal interface showed an evident gradient of Cr and Ni betweenfusion and type II boundaries, where the highest hardness value was recorded. Voir les détails
Mots clés : Dissimilar metals welding; 2205 duplex stainless steel; API X52 HSLA steel; Heataffected zone