IRANIAN JOURNAL OF SURFACE SCIENCE AND ENGINEERING
Year:2011 | Volume:- | Issue:11|Papers Count:11

In the present study, the effects of iron and manganese on the tribological behavior of F332 alloy were investigated. Alloys with addition of 0.7, 1.2 and 1.8wt% iron to the base alloy were prepared. The modification of the alloys was performed by proper additions of manganese. The pin-on-disk wear tests were carried out at room temperature under normal loads of 20, 30, 40, and 80 N, and sliding speed of 0.5 m/s for sliding distance of 1000m. The results showed that the size and morphology of the iron-rich compounds greatly influenced the tribological behavior of the alloy. In the case of un-modified alloys, the alloy containing 0.7wt% Fe, showed the best tribological and mechanical properties. Addition of higher amounts of Fe led to the formation of coarse, plate-like intermetallic compounds and, therefore, a considerable decrease in the wear resistance. The modification by manganese improved the tribological properties of the alloys and the highest wear resistance was obtained with the alloy containing 1.8 wt% Fe.

In this study, the effect of temperature of cryogenic treatment on hardness, microstructure, wear resistance and percentage of retained austenite of 1/2304 steel were investigated. For this purpose, two different cryogenic temperatures were used: -80oC as the shallow cryogenic temperature and -196oC as the deep cryogenic temperature. The results revealed that cryogenic treatment, caused an increase in hardness and a decrease in the percentage of the retained austenite compared to the conventionally treated specimen. Shallow cryogenic (SCT) and deep cryogenic (DCT) treatments increased the wear resistance of 5 -12 % and 37-52 %, respectively. Moreover, the wear debris and worn surfaces showed that the dominant mechanism in the wear test was adhesive. In the case of deep cryogenic treated specimen, the number of carbides increased while the carbides size was decreased. It was considered that the deep cryogenic treatment increased the driving force for the nucleation of carbides. The martensitic transformation start and finish temperatures were also studied using dilatometry tests. The results showed that the start and finish temperatures of the martensitic transformation were 254oC and - 87oC, respectively.

In this study, Ni-P coating on the surface of AZ31 Mg alloy was proposed by electroless plating due to improve in surface hardness and corrosion resistance. Electrochemical polarization test was done before and after coating on base alloy, with and without coating in 3/5wt%NaCl solution. The hardness of EN coating and base alloy also were evaluated before and after heat treatment, and surface morphology was studied by scanning electron microscopy (SEM). Also, microstructural changes were evaluated by X-ray diffraction (XRD) analysis. The results of this study showed that EN coatings with low phosphorus content were nano-crystalline and hard and the hardness of the coating could be increased with increasing temperature in heat treatment process, while the hardness of base alloy decreased due to grain growth and the rate of the corrosion increased. So the best range for Heat treatment of mg alloys was 230-270oc. heat treatment in this range would increased 110 HV hardness of the coating and decreased only 14BHN hardness of the base alloy.

In this research we have studied three samples of pure SnO2 thin films which are deposited by spray pyrolysis method on glass substrate. Oxygen and carbondioxide gas sensor were employed. The transmittance spectra of the samples showed that the thickness of the layers were within the nanometer scales (200-150 nm), and XRD spectra showed that as the samples become thiner the preference orientation varies from (200) to (110). The this variation of orientations was due to the variation of their thicknesses. Also crystallites sizes were decreased from 31 to 22.5 nm. The sensitivity of the samples to 2000 ppm of these gases showed that the optimum operational temperature in these samples was about 170oC and 180oC for oxygen and carbondioxide respectively. In addition we found that the sample with lowest thickness (150 nm) and crystallite sizes (~22.5 nm) with preferential orientation of (110) had more sensitivity to O2 compare to CO2 gas.

In this research we fabricated different Cu-Ni nanoparticles in order to investigate their catalytical, magnetic and sensitivity of properties. Cu-Ni core–shell nanoparticles on carbon thin films were prepared by co-deposition of RF-sputtering and RF-PECVD. Samples containing Cu nanoparticle were grown on carbon substrate in attendance acetylene and then Ni layers with different thicknesses were grown over these Cu nanoparticles. Topography and atomic structure were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. XRD showed that Cu core nanocrystal and Ni shell nanocrystal were formed on these films. Average particle size of Cu nanoparticles that was estimated by Scherre and Wiliam-son formola were compared. AFM image had a good agreement with William-son results.

One of the most popular and well-established techniques to fabricate low-loss optical waveguides is diffusing of metal ions into Lithium Niobate (LN) crystals. In this work we reported a 3-steps waveguide fabrication process, based on Zn diffusion into LN. First, a layer of Zn with the thickness of 150 nm was sputtered on a hot (127oC) LN substrate. Then the Zn atoms were oxidized by annealing the sample at 450°C for 10 min. Finally, thermal diffusion of Zn atoms into LN substrate took place in the different annealing temperatures and times. The aim of this work was to find an optimum diffusing temperature and time of Zn into the LN crystal. Structural and optical characterization of the prepared samples were carried out using XRD, RBS combined with channeling, SEM and double beam spectrophotometer.Our experimental results indicated that almost all of the Zn ions had been diffused into the LN crystal after annealing the sample at 750oC for 180min. The comparative analyses using XRD, RBS combined with channeling and spectrophotometry, revealed a good stability in optical and crystal structure of LN. Optical transmission and band gap energy of the samples were found to vary with the amount of the Zn content, while in the purchased LN crystal, the band gap was about 4eV, it was dropped to around 2.9eV after annealing the sample at 800oC because of diffusing the Zn atoms into the LN crystal. This result promises an improvement on the LN conductivity, therefore an enhancement in its waveguide characteristic.

Silicon nano particles were fabricated at angles, 0, 75 and 85 degrees on p-Si (111) wafer by evaporation method with electron beam. Sheet resistance of samples were measured by Van der Pauw method and compared with silicon wafer one’s. Results showed that by increasing angle from 75o to 85o silicon nano particles were formed by more porosity, therefore 85o sample can carry more current in similar voltages. Mean while surface area and sheet resistivity of 75o sample was more than 85o sample and also 85o sample was more than silicon wafer. Surface morphology and SEM surface picture were studied. Results showed that samples with more porosity had low sheet resistance. Also, I-V characteristic of nSi/p-Si (111) junction were reviewed. This junction had non linear electric and diode like behavior.

Electrodeposited Co-Cu/Cu multilayered films with nano scale bilayer under different growth parameters such as deposition potential, total thickness, and electrolyte temperature were prepared from a bath of CuSO4 and CoSO4 on Ti polycrystalline with (101), (103), and (001) strong texture substrates. Nanostructure and morphology of the deposits were respectively studied using X-ray diffractometer and scanning electron microscope. The XRD results showed that the multilayers have fcc structure with (111) strong texture. It was found that the growth of Cu is columnar and under more negative Co deposition potential their grain size and height of the Cu column tend to be decreased. It was observed that when total thickness increases the effect of lattice mismatch between the film and substrate decreases. Finally, the surface grain size and also concentration of impurity atoms such as S relatively increase with increasing electrolyte temperature.

A new design for magnetic structure of a circular planar magnetron sputtering cathode has been proposed through optimizing the configuration of its magnetic components by means of finite element software, “ANSYS”. In this design, magnetic flux lines were collimated in a wide region above the target surface by setting lateral magnet oblique with respect to target surface and by applying a shunt below the target. In addition, according to this design, a cathode was fabricated and its operational parameters were measured. At a pressure of 50 mTorr and a dc power of 1kw, we obtained 56% and 16 nm/s for target utilization and deposition rate respectively, as the most important parameters.

The Studies of the electrical properties for P-type thin films of CuInTe2 and CuInSe2 polycrystalline with the effect of excess Indium, Showed that conductivity and with the help of Hall coefficient RH and Hall mobility mH for different temperature at various gate field. It indicated that in P-CuInTe2, the variation of RH has been increased with temperature to grain boundary which started from 170 k by increasing few percent Indium to the stoichiometric charge. The value of Hall Co-efficient in the range of 77-200 k remained constant. By increasing few percent Indium to P-CuInSe2, the values of RH above 150 k due to increase of grain boundary distance. In this paper, Hall mobility values were studied.