فهرست مطالب kahrizsangi

In this work the effect of Nano-sized Fe2O3 on microstructure and hydration resistance of MgO-CaO refractories with 35 wt% CaO was investigated. MgO-CaO refractories with 35 wt% CaO content was prepared by using dolomite and magnesite calcined as starting materials and Nano-sized Fe2O3 (2,4, 6 and 8 wt%) as an additive. Samples were pressed into briquettes at a pressure of 90 MPa. Briquettes after drying at 110 oC for 24 hours were sintered at 1650 oC for 3 hours. Hydration resistance was measured at 25 oC in 95% relative humidity through the weight gain after 72 hours. According to the results, it is observed that when the amount of Nano-sizedFe2O3 added increased to 8 wt% the bulk density increased to 3.14 gr/cm3 and apparent porosity decreased to 8.20%. For the sample without addition, the mass gain after 72 hours was 1.76, which sharply decreased to 1.27 with increasing the amount of Nano-sized Fe2O3. With the addition of Nano-sized Fe2O3, bulk density and hydration resistance of the samples increased while apparent porosity decreased. Densification of MgO-CaO refractories was promoted to increase of Nano-sized Fe2O3 content. Nano-sized Fe2O3 addition led to formation of low melting phases such as C2F (2CaO.Fe2O3), CF (CaO.Fe2O3) and C3A (3CaO.Al2O3). The formation of this low melting point phases surrounding the CaO and MgO grain and grain boundaries and promoted densification of MgO-CaO refractories. The nature of Nano-sized Fe2O3 promoting densification is increasing the liquid phase sintering.

In this study, it was investigated the effect of modified carbon black Nanoparticles to improve anti-corrosion properties of epoxy-based coatings. SDS surfactant was used for decreasing Van Der Walls force between CB nanoparticles.TEM analysis showed CB nanoparticles were dispersed in epoxy matrix by lower than 50 nm. Coatings with 0.5, 1 and 1.75% CB nanoparticles were prepared and EIS technique was used for evaluating of coatings in 65°C. By adding CB nanoparticles, the resistance of coating to corrosive media increased and the capacitance of coating decreased. Diffusion coefficient of water decreased more than 107 times in 1% CB coating than to neat epoxy. It seems that CB nanoparticles fill micro pores in the coating and limit diffusion of corrosive ions and water.

There are various methods to produce iron based nano crystalline magnetic alloys. Among these methods, mechanical alloying is one of the most important. In this research, nano crystalline Fe85Si10Ni5 soft magnetic alloy was synthesized by mechanical alloying. The effect of alloying time on phase constituents and magnetic properties of the produced powders was investigated, by X-ray diffraction (XRD) and alternating gradient force magnetometer (AGFM). The XRD results showed that alloy formation started after 2 hours of milling. Further milling resulted in the reduction of the grain size and lattice parameter. After 60 hours of milling, the grain size was reduced to 8 nm. AGFM results showed that magnetic saturation and coercivity depends on the alloying time. Increasing the alloying time, causes the increase of magnetic saturation and decrease of coercivity.Abstract There are various methods to produce iron based nano crystalline magnetic alloys. Among these methods, mechanical alloying is one of the most important. In this research, nano crystalline Fe85Si10Ni5 soft magnetic alloy was synthesized by mechanical alloying. The effect of alloying time on phase constituents and magnetic properties of the produced powders was investigated, by X-ray diffraction (XRD) and alternating gradient force magnetometer (AGFM). The XRD results showed that alloy formation started after 2 hours of milling. Further milling resulted in the reduction of the grain size and lattice parameter. After 60 hours of milling, the grain size was reduced to 8 nm. AGFM results showed that magnetic saturation and coercivity depends on the alloying time.

In this research, the corrosion of API 5L 42X steel in contact with rock wool thermal insulation at four temperatures 20, 40, 60 and 80°C is investigated. For this purpose, the tafel polarization, cyclic polarization and weight loss examinations were used. Electrochemical and weight loss tests were conducted in insulation’s leachate and in contact with wet insulation, respectively. Furthermore, in order to confirm of corrosion tests results, the corrosion products that obtained from weight loss measurements at 20 and 80°C, were evaluated by X-ray diffraction (XRD) analysis. The results of tafel and weight loss examinations for 20°C showed that rock wool insulation alone had little talent in the corrosion creation on steel samples, which this outcome of the alkaline nature of it’s leachate and low chloride ion concentration in this insulation. In weight loss measurements due to formation of a close system, by the increase of temperature from 20 to 80°C, the corrosion rate continuously was increased, while such behavior because of formation of an open system was not observed for tafel tests in the temperature range of 60 to 80 ° C. Cyclic polarization tests and microscopic observations of samples surface after weight loss measurements have shown that the increasing of temperature is increased the tendency to localized corrosion.