مجله مواد مهندسی
پیاپی 2 (2009)

In present work، sintering ability of LiF: Mg، Cu، P powders has been studied. At first، Samples were heat treated in different sintering temperatures and times. Then، bulk density and apparent porosity of specimens were measured by Archimedes'' method. Finally، Micro structural analysis of sintered LiF samples was carried out with scanning electron microscopy (SEM). The results show that sintering behavior of LiF is very sensitive to temperature changes. Moreover، optimum sintering time of samples was long، which can be getting to more than 50 hours for some samples.

Besides possessing proper technical properties, the materials used by modern technology should be economical and environment friendly. Human of the modern age is trying to find proper solutions to recycle a major part of he industrial wastes Instead of disposing them into rivers, seas and oceans or accumulating them on the uninhabited deserts of the third World countries. SAW wastes are also considered as a class of environmental pollutants. The present research aims at finding a method for recycling such wastes by making use of Phases assessment systems, such as XRD, XRF, SEM, and carbon-sulfur assessment system (Strolein system) and by using separation, formulation, and ceramic sintering. The results of the study show that the deformed powder from SAW process might be recycled and used as powder of SAW for welding of low-carbon steel (st37) by separating the iron particles and adding some additives to deformed waste powder.

Sarcheshmeh copper mine, is located in south-west of Kerman, is one of a large open mine in the world and is one the important mineral and industrial site of Iran. The soil of the area naturally contains some heavy metals. Mining activities has also caused accumulation of polluting metals into the soil. Different methods are applied to reduce water and soil pollutants. Most of the methods are expensive and time consuming. Using suitable plants for remediation of the polluted soils, which is because of low cost and minimum environmental hazardous effects has accelerated in recent years. In this study, plants Rumex pulcher and Verbascum songaricum were collected from three sites around the Sarcheshmeh copper mine, and plant roots, shoots and the soils of the rhizosphere were analyzed for Cu, Zn and Pb in spring and summer 2007. The plant and soil samples were sent to Amdel laboratory in Australia were analyses for their metals contents using ICP. The results showed higher ranges of metals in sites accumulated in plants. Accumulation of these metals of plants in summer was more than spring. According to results it is indicated that the plants have high potential of accumulating of these metals.

Effect of cryogenic treatment on microstructure, hardness, and wear resistance of high Cr-C tool (D6) steel has been studied, in comparison with effect of conventional quench-temper treatments on those properties. Cryotreatment includes austenitizing, quenching in hot oil, immediate cooling of steel down to -78 or -180˚C, and keeping the samples at one of those temperatures for 6 or 24 hours. The results show that retained austenite decreases in microstructure and submicron carbides precipitate in matrix of steel after cryotreated samples, in relative to those after conventional quench-temper treatment. Wear resistance in cryotreated samples significantly increases in comparison of conventialy treated samples, however, hardness variation is moderate. Hardness and wear resistance increases as time and/or cooling increases during cryotreatment. It is revealed that increasing holding time in cryogenic environment from 6 to 24 hours improves wear resistance by 23%, however decreasing temperature of cryogenic environment from -78 to -180˚C provides only 4% improvement in wear resistance. Increasing velocity of wear disk increases wear resistance, whereas, increasing applied load decreases wear resistance of steel. In general, wear resistance of D6 steel after cryotreatment is significantly superior to those properties in D6 steel after conventional quench-temper treatment.

In this paper we work on prototype survey of using iron and manganese compounds in production of catalyst converter with nano particles for ROA dual fuel system instead of a lot of cerium in (La،Ce) (Pd،Co) O3-Perovskite catalysts and its comparison with imported catalyst of Iran Khodro with noble metals. (La،Ce) (Pd،Co) O3 Perovskite catalyst was prepared by the citrate route without use of Pt and Rh. We used just Pd (1. 2 g) and it was deposited on ceramic monoliths according to a dip coating procedure. We used catalyst on RD car with XU7 motors model and measured the amount of emission with (AVL) test at Sapco Company and compared the catalyst with imported catalysts of Iran Khodro Company with noble metals such as Pd، Pt and Rh by Iran Khodro Company with Euro III standards. In conclusion Perovskite catalysts reduce emission better than imported catalysts، with lower emission and price. Monolite of catalysts were characterized by specific surface area measurements (BET) and X-ray diffraction (XRD) and X-ray fluorescence (XRF)، and coat characterized by scanning electron microscopy (SEM). Finally the illustration shows Nano Particles size on coat.

In this investigation a nanostructure titania membrane on an alumina support was prepared. The support was made via a single axis press. The titania colloidal sol was then prepared. To have a crack-free titania membrane، PVA and HPC additives were included in the sol in specific amounts. The support was dipped in the sol and the layer was dried and calcined in a proper manner. The average particle size of the titania sol was measured to be 55. 6 nm. X-ray diffraction technique was utilized to determine the titania phase transformation temperature. The burn out temperature of the volatile materials and the organic additives were determined via the TGA technique. Utilizing the XRD and TGA techniques the optimum calcinations temperature was determined to be 450˚C. Microstructure and the presence of any possible crack or defect were examined using Scanning Electron Microscopy. The final product was a crack-free titania membrane with no defect. Therefore، it can be concluded that the membrane preparation procedure is optimum.

Silicon nitride films were deposited on glass and polycrystalline silicon by RF sputtering using hot pressed ceramic Si3N4 target. Depositions were done in Argon and Nitrogen atmospheres. In order to optimize an antireflective coating for solar cells, sputtered silicon nitride thin films were grown with various RF power of deposition in two different atmospheres. The compositional, morphological and optical properties of film were investigated by RBS, SEM and UV/VIS/IR spectrophotometer analyses. Silicon nitride films (2000nm thickness) deposited with the RF power between 100-150W have exhibited high transparency≈92% for the spectral range between 300-1200nm. The silicon nitride antireflection coating deposited on the textured surface of multicrystalline silicon solar cells decreased the overall reflection of the cells from 12% to less than 2%.

In this paper, a low-cost Ni/Cu structure as an ohmic contact was fabricated on Polycrystalline n+Si Via electrochemical method by the application of an ultrasonic system and the electrical resistivity of the contact was optimized. After electroplating of Ni in watts bath for 10, 20 and 40 min, an electroplated copper layer was deppsited on Ni film in order to reduce the sheet and contact resistance by using an ultrasonic system one can obtain a film with the lower surface roughness and the higher quality. The electrical resistivity of the electroplated Ni/Cu was investigated for vacuum annealing at various temperatures. Post treatments of the coated Ni improved the crystalline structure of the electroplated layer. Contact resistance of the Ni/Cu structure on an n+Si was measured using the Transmission Line Model (TLM) Method. An optimum specific contact resistance of 2.2×10-5 Ωcm2 was obtained for layers annealed at 400°C for 10 min. SEM, XRD, and EDX analyses were used to investigate the surface morphology, structure and composition of deposited films.

Circular base plates are commonly used for pipe columns, such as pylons in cabled-stayed bridges, lighting poles and electric power line posts. Against rectangular base plates, an exact method has not been presented about design of circular base plates in the classified and well-documented form. Therefore, this paper by expression of mathematic formulas describes on exact method to design these plates which use of this method requires an iteration approach to solve the equilibrium moment equation. Then it compares by presented graphs obtained designing results from exact and existing method [1], in return for different design parameters and demonstrates safe limits to use of approximate method. The results show that approximate method commonly will not be safe and can demonstrate reasonable results under specified conditions. Whereas exact method has been presented in this paper is safe and replies reasonably under any conditions.

The Nd:YAG pulsed laser welded structure of Copper-Beryllium alloy were studied by varying laser parameters such as pulse energy, spot diameter, duration and frequency. The metallographic results showed that the pulse energy should be kept as low as possible in order to obtain the weld pool with the highest values of penetration and the least width. Low pulse energy decreases the time for segregation of impurities. The impurities are the main cause of hot cracking. In addition, the laser spot diameter should be kept as low as possible. Moreover, the microscopic investigations demonstrate that the dendrite structure prevails in weld pool near the weld centerline and the cellular structure forms in weld pool near the base meal.