Materials and Technologies

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Authors: Traian Petrişor, Bogdan Viorel Neamţu, A. Rufoloni, M. Cristian Rauca, Liviu Brânduşan
Abstract: Silver free Ti-43at.%Cu (Ti-Cu) eutectic alloy have been developed for the brazing of Be and Cu99.32Cr0.6Zr0.08 (CuCrZr). The structural and microstructural properties of the as obtained alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS). The analysis have revealed that the Cu-Ti eutectic alloy have a fine and homogeneous eutectic structure with the phase composition corresponding to the Ti-Cu phase diagram. These observations are consistent with the thermal properties of the alloys determined by DTA-TG analysis. The role of Mn on the eutectic structure, as well on the wetability properties was also studied. The effect of Mn is to produce a less coarse eutectic structure and to decrease the wetability angle. The mechanical testing of CuCrZr/Ti-Cu/CuCrZr junctions have demonstrated that these alloys are suitable for the brazing of Be and CuCrZr. The shear strength of the CuCrZr/TiCuMn/ CuCrZr increases with Mn concentration reaching the value of about 280 MPa for 2at% Mn.
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Authors: Adem Kurt, Hakan Ates
Abstract: In this study, weldability of bronze parts produced by powder metallurgy has been investigated by using TIG welding technique. Bronze powders were pressed into 55x44x5 mm size specimens under pressure of 350 MPa. Then these specimens were sintered at 650, 750 and 870 °C for 45 minute under argon atmosphere. Finally, the parts were welded by TIG welding method. Hardness values of the welded joints were measured and microstructural features were investigated.
315
Authors: R. Yilmaz, Ali Türkyilmazoglu
Abstract: In this study, AISI 420 martensitic stainless steels were welded by GTAW (gas tungsten arc welding) using ER 316L consumables. Pure argon, argon + 25% He and argon + 5% N2 were used as shielding gases. The obtained results indicated that shielding gases have some effect on the properties of the martensitic stainless steel weldments. The use of argon+5%N2 provides the highest tensile strength values and higher microhardness profile compared to the other shielding gas composition used.
319
Authors: Luminita Andronic, Anca Duta
Abstract: The photocatalytic activity of the titanium dioxide thin film has been investigated towards the degradation of methyl orange in aqueous solutions. Porous TiO2 thin films were deposited on glass substrate by doctor blade technique. The thickness of the film prepared by doctor blade was also evaluated from de UV spectrum and the average value corresponds to 5 μm. The photocatalytic efficiency was evaluated as the percentage of pollutant bleaching, after 6h of UV illumination. The influence of the operational parameters (dye concentration, pH) on the degradation rate of the dye on TiO2 was examined. The catalytic activity of the films towards photodegradation of methyl orange pollutant was examined and their photocatalytic efficiency was calculated.
325
Authors: Erika Ardelean, T. Hepuţ, Marius Ardelean
Abstract: The paper presents research carried out in order to obtain thermo-isolating and covering powder used in the Tundish of the continuous casting installations. This powder is made by using different types of waste originating in the iron and steel industry and in the energy industry, such as: thermal power-station ashes, furnace slag, B.C.A. scraps, limestone, black ash, fluorine, raw dolomite, graphite powder. The powder thus obtained must have a faster melting speed and a lower melting temperature; it does not make the steel impure or diminish the heat losses through radiation. An effect of applying the experimental results in industry, besides financial economies, is to obtain an accelerated integration of a technological process in companies, according to European Union requirements regarding the preservation of the environment.
329
Authors: M.D. Zuga, Lucretia Miu, M. Crudu, V. Bratulescu, H. Iovu, E. Manaila
Abstract: In the research work some thermoplastic elastomers have been obtained by compounding the ethylene-propylene terpolymer (EPDM) rubber with melt platicized PVC. The influence of every constituent level on the polymer compound characteristics was measured. The two polymers are incompatible, for the improvement of the EPDM/ PVC blends two methods of compatibility improvement have been used: 1) using compatibilizing agents (CPE was the selected compatibilizing agent); 2) electron beam irradiation (the optimum irradiation dose determined was 5 Mrad). The resulted products showed specific elastomer characteristics and can be processed by commonly used techniques for thermoplastic materials like as injection and injection molding.
333
Authors: Tudor Prisecaru, D.C. Dinescu, L. Mihaescu, Malina Prisecaru, G. Darie, H. Necula
Abstract: This paper investigates the methods to stabilize a bio-gas flame inside a combustor. A procedure a modelling by dividing the combustor in 8 identical sections, each sections having 343,000 volume cells have been used. Bio-gas composition has been assumed to be 50% methane, 40% carbon dioxide and all the rest to be assimilated with hydrogen in volumetric participation. Due to the different values of ignition time delay, some gas flames already observed to be unstable can be transformed into stable ones by using by-product supplementary fuels
337
Authors: R. Ivănuş
Abstract: An experiment of lively biohydrometallurgical leaching of worn-out hydrogenation catalysts in an aerobic batch system with Thiobacillus ferrooxidans is carried out for process parameters optimization. The maximum bioleaching of worn-out catalysts is noticed at 74.85% (w/w) and 71.50% (w/w) for 25 kg Cu/m3 and 30 kg Cu/m3 initial concentration of 200 to 240 μm waste mesh size in 192 h with pH 2.5 and temperature 35°C, respectively. The optimum shaking speed is noticed as 60 rpm. All results are noted after subtraction of leaching in control conditions. Seven days age-old and 20% (v/v) innoculum culture is used in the present study. The dissolved copper was precipitated by the precipitation using metallic iron splinter. The copper powder obtained was characterized by chemical and physical methods.
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