JOURNAL OF NEW MATERIALS
Year:2012 | Volume:2 | Issue:3 (7)|Papers Count:9

Micro alloyed steels are widely used in several industries including crude oil and natural gas for which they called API steels. These steels are produced using hot rolling after steel making and continuous casting and impact resistance is one of the main mechanical properties that are measured in the final products. Impact resistance is affected by several processing parameters. In the present study, the effect of 33 processing parameters such as chemical composition, strain, strain rate and temperature of hot rolling were studied using a neural network model for 122 independent samples. Two model were studied to investigate the error range and increasing the accuracy based on the difference between neural network and experimental results. Two neural network models with one and two hidden layers were used to train the system. It has been shown that two hidden layer model is more accurate with less errors. The results showed that the model can be used as a quantitative guide to control the final impact properties of API steels. According to the prediction by the neural network, the maximum values of impact properties were affected by Carbon and Niobium content of the billet, billet temperature in the final rolling stage, final rolling temperature and Coiling temperature.

SnO2 nanoparticles were synthesized by thermal decomposition. Taguchi analysis, a statistical experimental design method was also used to find the effects of three parameters, molar concentration ratio [nitrate solution/SnCl4 solution], temperature and time of calcination, on the size of SnO2 particles. The nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy techniques. Taguchi analysis showed that the molar concentration ratio of [nitrate solution]/ [SnCl4 solution] was the most effective parameter on the particle size. The optimal conditions were determined by using Taguchi robust design method and nanosized SnO2 particles (2 nm) were obtained.

In this study V doped TiO2 thin film deposited on glass substrate using a sol-gel dip coating method was investigated. X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectrophotometer were used to investigate the film properties. In addition, the photo-catalytic properties of films were evaluated with methylene blue degradation under UV irradiation. The results indicated that V doping has a significant effect on the absorption edge and photo-catalytic properties of TiO2 thin film.

Zircon and alumina were mixed in accordance with the atoichiometry ratio and activated in a planetary ball mill from 1 to 10 hours. After finishing mechanical activation processes and removal the iron impurities, each mixture was isothermally heated for one hour in a tube furnace at different temperatures. XRD results showed the decomposition of zircon reduced to about 1300oC in a one-hour-milled sample. The amount of retained tetragonal zirconia in the one-hour-milled sample was higher than the un-milled samples after isothermal heat treatment. With increasing temperature up to 1450oC, the amount of tetragonal zirconia some how decreased in the activated samples, whilst the increasing in amount of tetragonal phase was observed in the un-milled samples.

In the current research the scratch behavior of poly methyl methacrylate (PMMA) and its nanocomposites has been investigated. For this purpose PMMA matrix nanocomposites reinforced with different weight percent of nano sized alumina (0, 5, 10 and 15) were fabricated using compression molding technique. The scratch test was followed the ASTM G171 standard and the test was done using scratch apparatus at room temperature, 5 mm/s scratch rate and different load (10 and 15N). To clarify the scratch mechanism of PMMA and its nanocomposites, microscopic evaluation was performed using scaning electron microscope (SEM). The results show that the scratch hardness of the fabricated nanocomposites depends on the alumina content. While nanoparticles increase from 0 to 15 weigth percent the width of scratch, changes from 274 to 210 µm. Also the results of microscopic evolutions showed that the dominant mechanism in the scratched pure PMMA is mar damage. Beside, an increase in weigth percent of nano particles up to 5% causes a change in the scratch mechanism from mar damage to craze.An increase in weigth percent of alumina content improves the scratch resistant and eliminates the effects of scratch pattern gradually.

In this paper the smelting conditions of different concentrate and the effects of them on the concentrate reactivity were investigated. Different phases associated with chalcositic and chalcopyrite concentrates identified by using of XRD and SEM methods. The effect of three kind of concentrate with different compositions on the operational conditions of flash furnace such as burning atmosphere, excess air and equilibrium furnace temperature were investigated. The results showed that chalcopyrite concentrate has the better reactivity, higher matte production and better burning in normal atmosphere.

GTD-111 superalloys are of the newest Ni-based superalloys which due to of having good stability and strength at high temperatures are used in manufacturing of hot-gas-path parts of the gas turbines. Because of severe working conditions, application of these superalloys without coating isn't recommended. For this purpose, the superalloy is coated and then is used. In this paper, the effect of Aluminide coating on rapture behavior of the GTD-111 superalloy is investigated. For this purpose, a number of samples made from GTD-111 superalloy have been coated by powder cementation method and have been subjected to rapture test and have been compared to uncoated samples. The results suggest that the presence of coating causes increase in Al content in the surface and contributes in stability of g’ which is the most important factor of superalloy strength and also causes increase in life cycle of this superalloy with respect to similar uncoated samples.

One of the most effective methods to remove inclusions and impurities in metals foundry are the use of porous ceramic filters. In the gating system these filters can remove slags and other types of inclusions and contaminants from melt. In order to make silicon carbide-based ceramic foam filters SiC-(CFF) in the research, we used Polyurethane sponge in ceramic slurry by replica method. Ceramic slurry contain silicon carbide, alumina, ball clay and zircon fine particles in the micron and sub-micron size. To increase the adhesive properties and create thixotropic behavior, other additives such as colloidal silica and carboxymethyl cellulose (CMC) were added to slurry. After making the filters, mechanical and microstructure properties of them were studied. Mullite phase along silicon carbide phase formation in microstructure of filters, is one of the reasons that causes increasing in compressive strength and refractoriness. Existence of, these phases was proved by XRD analysis. Finally to compare the performance of these filters with the imported one, molten ductile iron passed through them and the density of the castings was studied. Results showed that disperse and completely homogenized that these filters performances are as good as the imported ones. Microstructure studies by SEM showed silicon carbide and mullite ceramic phases formed in microstructures of the filters.