JOURNAL OF ADVANCED MATERIALS AND TECHNOLOGIES
Year:2015 | Volume:3 | Issue:4|Papers Count:9

In this paper, a low-cost Ni/Cu structure as an ohmic contact was fabricated on multicrystalline n+-Si by using electrochemical method and the electrical resistivity of the contact was optimized. Ni was deposited on substrates by two methods: electroless plating and electroplating. After Ni electroplating, samples were annealed at various temperature and then an electroplated copper layer was formed on Ni film in order to reduce the sheet and contact resistance with using an ultrasonic system one can obtain a film with the lower surface roughness and the higher quality. Post treatments of the coated Ni improved the crystalline structure of the electroplated layer. SEM, XRD, and EDX analyses were used to investigate the surface morphology, structure and composition of deposited films. The surface roughness was investigated by profile stylus DEKTAK. Contact resistance of the Si/Ni/Cu structure was measured using the Transmission Line Model (TLM) method. Results demonstrate that specific contact resistance for the electroless plated Ni/Cu structure is 8.9×10-5 Wcm2, while an optimum specific contact resistance of 2.2×10-5 Wcm2 is obtained for structure with electroplated Ni layers.

Recently, composite scaffolds prepared by electrospinning have shown desirable properties for tissue engineering applications. In this study, first the nBGs were prepared via the sol-gel technique, then, the electrospun PHB/nBG nanocomposite scaffolds (with 7.5, 10 and 15 wt% of nBGs) were fabricated. The nanoparticles and scaffolds were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction spectrometer (XRD), X-rayfluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FTIR). Results showed that nanoparticles with an amorphous structure mainly had a particle size of less than 70 nm. All the nano-fibrous scaffolds had a uniform distribution of interconnected porosities with fiber diameters ranging from 326.1 nm to 1.276 micrometer. Composite scaffolds having nanoparticle concentrations higher than 7.5 wt%, tend to agglomerate. In addition, the FTIR results showed a favorable interaction between the polymer and nBGs. Therefore, the proposed PHB/nBG scaffolds prepared in this study can be considered as good candidates for bone tissue engineering applications.

In this study the healing performance of micro-cracks by microcapsules containing linseed oil in the coating of polyaniline as conducting polymer were investigated. The In situ polymerization in the urea - formaldehyde resin was done to produce linseed oil capsules. The synthesized capsules were studied by Scanning Electron Microscope and contents were determined 75% of their oil. The (FTIR) test was performed to verify the success of being microcapsule. The process of Polyaniline coating was performed by using the electrochemical galvanostatic method in 0.7, 0.9, 1, 2 and 3 A/dm2 current densities. The performance of corrosion resistance of the composite coating containing microcapsules was studied by potentiodynamic polarization test in the 3.5 percent solution and immersion in the 5 percent sodium chloride corrosive solution. The results showed that sample coated with a current density of 1 A/dm2 composite with 0.01 weight of microcapsules had very good self-healing and corrosion resistance properties and Efficiency of 95% was determined to protect it.

Carbothermal reduction process has been regarded as an industrial method for extraction of zinc metal since a long time ago. Moreover, recently recovery of zinc from electric arc furnace dust, by carbothermal process, has been considered by many researchers. Since this process involves a solid state boundary reaction (direct reduction) between zinc oxide and carbon particles, the reduction rate is very sensitive to the particle size of reactants. In this study, the effect of zinc oxide particle size on kinetics of process has been studied by isothermal gravimetric analysis technique. Furthermore, in order to interpret the obtained data, a mathematical model has been developed which is acceptably fitted to the experimental results.

 Nowadays, there is considerable attention to use of Ni-base coatings on steel because of its high corrosion resistance in various corrosive environments; there is still a considerable void in our knowledge of the influences of additives on corrosion and microstructure of these coatings. Besides, using of Ni-base pack cementation method has been very attractive because of its low-cost and ability to coat complex shapes and even the internal surfaces of the samples. For these purposes various amounts of CeO2 (1wt%, 3wt% and 5wt%) was added to the Ni-base (NiCrBSi)(56% Ni, 24% Cr, 7.5% C, 4.5% Fe, 4.5% Si, 3.5% B) raw materials. The pack cementation coating method were used on a mild steel substrate. SEM, XRD, optical microscopy and X-ray diffraction analysis methods were used to characterize the coats. Moreover polarization dynamics corrosion test was also used to study of corrosion in a 3.5%t NaCl solution. The results showed that Ni-base pack cementation coats are more corrosion resistance. Besides, the corrosion rates were decreased with increasing the CeO2 contents in the coat. By comparing the percent inhibition of samples coat a sample of 5% cerium cementation found that the criterion of 86% is the maximum percent inhibition.

Nowadays, nano composite coatings have created many applications in different industries with due to uniqe properties such as hardness, good wear resistance and high corrosion resistance. B4C particles are hard substance that they are used as a reinforced particle in electrodeposition process. The aim of this research is, investigation of various parameters on morphology, and corrosion resistance of Ni-B4C nano composite coatings. In this study, Ni-B4C nanocomposite coating was formed on copper substrate by direct current (DC) at Watts bath contained nickel sulfat (NiSO4.6H2O), Nickel Chloride (NiCl2.6H2O), Boric Acid (H3BO3) with Poly Vinyl Pirrolidone (PVP) and Sodium Dodecyl Sulfate (SDS) surfactants. The morphology of nanocomposite coatings were analyzed by scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM). Also, corrosion resistance was measured by polarization test. The hardness of coatings were measured by micro hardness test. According to the results obtaining in this study, beyond of optimum condition, the concentration of B4C is 10 g/l, current density is 5A/dm2 and the electrodeposition time is 30 minute.

In this work, WO3 thin films have been deposited on optical glass and transparent conducting oxide substrates using aqueous and organic sols by means of dip coating followed by post annealing at 400oC. The wetting of applied substrates by the prepared sol has been simply studied by observation and photography. The prepared thin films were also studied by various techniques including scanning electron microscopy, X-ray diffraction, and cyclic voltammetry in H2SO4 solution. The results showed that aqueous sols showed undesired wetting while aqueousalcoholic sols could splendidly wet both glass and TCO substrates. However, the use of ethyl alcohol resulted in the degradation of the films during the drying process whereas this problem could be overcome by the introduction of heavy alcohols. Aqueous-alcoholic sols prepared from Lauryl Alcohol and peroxytungstic acid which was previously synthesized from sodium tungstate precursors were optimized as the dipping sol. Results showed that the presence of Lauryl alcohol reduces the size of the crystallites and grains in the prepared thin films. The monoclinic phase of WO3 was transformed to triclinic phase by the addition of Lauryl alcohol to the prepared sol. The cyclic voltametery analyses also verified the improved electrochromic properties of the prepared layers in the presence of Lauryl alcohol.

 in this work tribological characteristic of engine oil 20w50 mixed with 0.1% by weight of spherical nano particles of copper oxide of 20 nm and also spherical nano particles of titanium oxide of 21 nm has been investigated. Wear and friction are the two important factors of tribological characteristics. In this work after preparation of the nano fluids, two factors of wear and friction factor, using pin and plate tribometer, under constant load and at room temperature, once with pure engine oil and also with each nano fluids were measured and the results were compared to each other. The results indicated that presence of spherical nano particles of 20 nm copper oxide and 21 nm titanium oxide in lubricating oil, reduced the wear by 76.72% and 50% respectively and friction factor by 17.84% and 9.48% respectively, in comparison with engine oil without any nano particles. Therefore it can be predicted that spherical nano particles of copper oxide and titanium oxide, as an additive to engine oil, can play an effective role in increasing engine power and reduce engine exhaust emissions and fuel consumption.

The inhibition effect of synthesized Schiff base-chromium Complex, namely Bis (N-(2, 2-aminoethylamino) ethanol) salicylaldehyde) chromium (III) chloride on the corrosion of mild steel in 0.5 M HCl was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The experimental results suggest that the complex is a good corrosion inhibitor at different concentrations and its adsorption was described by the Langmuir adsorption isotherm. The adsorption isotherm parameters such as ΔG0ads ads and Kads were determined at room temperature. Polarization curves indicated that this Schiff base acts as a mixed (anodic) type inhibitor. Polarization results revealed that the inhibitor showing a maximum efficiency 79% at concentration of 100 ppm. The scanning electron micrographs (SEM) images showed significant effect of the inhibitor.