Advanced Materials Research Vols. 622-623

Abstract: Today's, with the development of numerical analysis methods, simulation and analysis of processes of forging has witnessed a great deal of development and those methods one considered as one of the strongest ways of improving forge. In this research, the process of hub production with the finite volume method by means of superforge software is simulated and the required energy shaping of work piece was extracted. The considered work piece was produced in three stages by hot forging. The effect of coefficient of friction and temperature on process was examined. The result show that the effective stress will increase with rising of coefficient of friction and with increasing the temperature the press force decreases and effective plastic strain increases.

Abstract: A phthalocyanine derivative: 2,9,16,23-tetra-tert-butyl-29H,31H-copper(II) phthalocyanine (CuttbPc) was used as an optical gas sensor based on Langmuir-Blodgett (LB) films. Surface pressure-area per molecule (π–A) isotherms and Brewster Angle Microscopy (BAM) will show the process of the monolayer formation at the air-water interface. The responses of the thin films to various volatile organic compounds (VOCs) were recorded by UV-Vis absorption spectra and the morphological characterization was performed by Atomic Force Microscopy (AFM). The experimental results indicate that highly-ordered and uniform films can be prepared at about 33mN/m with the transfer ratio of 0.7. The results also demonstrated that CuttbPc LB films are promising to be applied into optical gas sensors for VOCs detection and recognition.

Abstract: In this paper are presented the results of researches, obtained during cast iron melting on basis of steel scrap and a carburizer (without pig iron in solid charge). In the process of carburization, there were used the carburizers such as anthracite, natural and synthetic graphite, petroleum and cupola coke, as well as charcoal. The grey cast iron was produced, for which quantitative analysis of graphite precipitations was performed. It was noticed that in case of using anthracite as carburizer, the smaller graphite precipitations were obtained. In authors’ opinion they are consequences of anthracite structure, consisted of fine graphite flakes and phenomenon of charge materials features’ transfer into melted alloys (structure heredity).

Abstract: In this paper, the thermal oxidation behavior, adhesion and tribological properties of TiAlON films coated on hastelloyX substrate, typically used for fuel nozzle in gas turbine engine application, have been studied. The uncoated and coated samples were heated to different temperatures, i.e. 950, 1050 and 1150 °C in the controlled atmosphere. The surface appearance, microstructure, chemical composition and adhesion of films were investigated. The thermal oxidations were observed in all testing conditions showing thicker oxide film at higher temperature. However, spalling of oxide scales was found in hastelloyX and TiAlON coated at 1150°C suggesting the maximum working temperature of < 1150 °C. The critical loads corresponding to the full delamination of the thermal oxidation coated specimens were found to be higher than the non-thermal oxidation specimens. The effect of thermal oxidation on damage patterns during scratch tests, i.e. less chipping and cracking for thermal oxidation specimen, were also observed. The tribological properties were also investigated under different load under room temperature and 600 and 1000°C. The results suggested significant improvement in wear resistance of coated sample especially at low load at all temperatures.

Abstract: The dependence of hysteretic properties of FeMn/CoFeB (AF/FM) thin bilayers on AF thickness and magnetic annealing temperature is systematically investigated for possible applications in spin-valve devices. Inducement of an easy axis after magnetic annealing is established. The anisotropy is studied by investigating the coercivity along and perpendicular to the induced easy axis using Magneto-Optic Kerr Effect (MOKE) and the AF texture is ascertained by XRD. The existence of an optimum annealing temperature, for which the maximum change in coercivity occurs for a particular AF thickness, is evidenced. The maxima in HC of the bilayer with thickness of AF layer were correlated with FCC FeMn (111) texture of the sample.

Abstract: The friction stir processing is a solid state processing technique. The present study investigates the effect of process parameters like tool rotational speed and tool feed on the mechanical and tribological properties of friction stir processed AZ31B magnesium alloy. The experiments were conducted with 3 level 2 factors full factorial design with two replications. The responses were tensile strength, microhardness and wear. The investigation reveals that both the tensile strength and microhardness values were decreasing with decreasing grain size. The minimum wear rates were observed at higher hardness values.

Abstract: Severe plastic deformation is one of the emerging and promising techniques applied to bulk materials to produce fine grain structure with attractive properties. This study aims to investigate the effect of extrusion parameters like extrusion temperature, number of passes on the equal channel angular pressing and twist extrusion forming behavior of AA7075-T6 Aluminum alloy by hot extrusion process. AA7075-T6 samples of 70x28x18 mm cross sections extruded by equal channel angular pressing and twist extrusion process was subjected to microstructure analysis, hardness and tensile tests in order to determine their mechanical properties. As a result of the experiments, it was determined that twist extrusion leads to more grain refinement at high temperatures with more number of passes compared to equal channel angular pressing. SEM micrographs show that there is severe orientation of the grains facilitated by the extrusion process which enhances the strength. The dense banding of the grains had effected in marginal hardness enhancement in the matrix of the specimens processed by twist extrusion and equal channel angular extrusion process.

Abstract: Ethylcellulose (EC) is a biocompatible cellulosic derivative widely used in the drug industry.In the present work, EC nanofibres were electrospunusingethanol: toluene(40:60-by wt.) mixture system by both single needle electrospinning (SNE) and bubble electrospinning (BE) methods. Comparisons of the effect of the various process parameters such as needle/solution surface to collector distance, app. volt. and feed rate on fibre characteristics were studied. The optimum SNE feed rate comparable to BE was decided 1.5ml/hrafter comparing fibre diameter. Comparisons of these parameters revealed that fibre morphologiesfollows different trendsin SNE and BE.Average (Avg.) fibre diameters increased with increase in feed rate in SNE.As needle to collectordistance (NTCD)increased, theavg.fibre diameter decreased in SNE. However, in BE, fibre diameter increased with increase in solution surface to collector distance (STCD).Fibre diameter decreased in SNE with increase in app. volt.. However, in BE; initially the fibre diameter decreased and then increased with increase in app. volt.. These different trends in diameter of BE and SNE electrospun fibres are explained and discussed in the present article.

Abstract: Al₂O₃ films were deposited onto Al₂O₃-TiC substrates by RF diode sputtering. The Al₂O₃ films were deposited at various substrate bias voltages from -80 to -180 V, sputtering powers from 4 to 8 kW and operating pressures from 20 to 30 mTorr. The stress induced in Al2O3 films was measured. The results show that the stress induced in all prepared Al₂O₃ films is tensile stress. The stress slightly increased with increasing substrate bias voltage whereas it increased linearly with increasing operating pressure. However, the stress was almost constant as the sputtering was increased from 5 to 8 kW and significantly decreased as the sputtering power was decreased below 5 kW.

Abstract: Hydrogen is an important utility in the production of clean fuels as low-sulfur gasoline and diesel. The combination of low-sulfur fuel specifications and reduced production of hydrogen in catalytic reformers make hydrogen management a critical issue. In this paper a systematic approach for the retrofit design of hydrogen networks in refineries was proposed. The methodology is based upon mathematical optimization of a superstructure and maximizing the amount of hydrogen recovered across a site. The techniques account fully for pressure constraints as well as the existing equipment. The optimum placement of new equipment such as compressors and purification units is also considered. Total annual cost and fresh hydrogen required by the refinery are employed as the optimizing objects. Equations obtained from superstructure method are solved with mixed-integer nonlinear programming of the general algebraic modeling system. In this work the Tehran refinery was considered as a case study. The results of optimization show that the 28% reduction was achieved in hydrogen production of north section and this is 35.7% for south section of refinery. Also adding the new hydrogen recovery unit in hydrogen network will cause 20% reduction in total costs of north and 31.2% in south sections.