Papers by Keyword: Thermal Treatment

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Authors: Lei Yang, Hua Li, He Zhou Liu, Yang Yang Zhang
Abstract: Mixture powders with different ratio of Ag/γ-TiAl were deposited on titanium alloy by low presure plasma spray and thermal treatment was applied to convert the mixture coatings into Ti-Al-Ag ternary ones. The experimental results indicated that the oxidation resistance of ternary coatings was better than sheer γ-TiAl coating and increased with increasing Ag from 2at.% to 4at.% at 700 and 800°C. The outside oxide scale consisted of alumina and a small amount of rutile due to the insufficient diffusion of Ag in γ-TiAl.
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Authors: M. Federica de Riccardis, Virginia Martina, Daniela Carbone, Paolo Rotolo, Annapaola Caricato, Gilberto Leggieri, Luciano Pilloni, Leander Tapfer, Rossella Giorgi, Elena Salernitano
Abstract: Poly(etherether-ketone)-alumina coating were deposited by EPD. In order to densify the coatings, conventional thermal treatments were performed at a temperature equal or higher than the melting point of the polymer. The samples treated at the lower temperature showed an increase in the quality of crystallinity of the polymer. As an alternative method, an excimer laser was used to treat the surface of the composite coatings. The laser beam irradiation did not induce any modification in the crystalline structure of the polymer and at the same time did not produce strong degradation of the polymer molecule, also when the laser beam fluence was higher than the ablation limit. The most relevant modification induced by both the treatments was a change in the morphology and the porosity.
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Authors: Qing Shan Kong, Chun Xiang Guo, Bing Bing Wang, Quan Ji, Yan Zhi Xia
Abstract: In this paper, ferric alginate fibers was prepared by wet spinning of sodium alginate into a coagulating bath containing ferric chloride. The carbon-supported nanoscale zero-valent iron fibers (CSNZVIF) were obtained through thermal degradation of ferric alginate fiber at 900°Cunder N2 atmosphere. The product was characterized by field emission scanning electron microscopy (FESEM), X-ray power diffractometer (XRD), and Brunauer-Emmett-Teller (BET) surface area. It was found that zerovalent iron particles were well dispersed in the amorphous carbon fibers. CSNZVIF has high surface areas of 352 m2/g. The existence of carboxylic group and hydroxyl group in ferric alginate structure unit plays key role in the formation of carbon-supported nanoscale zero-valent iron fibers. Fe3+ was reduced to Fe0 by hydroxyl group and as-formed amorphous carbon during heating under N2. This thermal degradation and self-reduction reaction of ferric alginate fiber is potentially scalable to large production and continuous processing for preparing CSNZVIF.
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Authors: Wen Sheng Linghu, Chun Yan Sun
Abstract: In this work, the TG/DTA behavior of decabromodiphenyl ether (BDE-209) at nitrogen and air atmosphere by using a thermogravimetric analyzer was investigated. The results showed that both of TG and DTG curves at nitrogen atmosphere are very similarly with that at air atmosphere. About 75 wt% and 25 wt% of total mass loss were observed at the temperature range of about 300-430 °C and about 430-580°C, respectively. It is indicated that the mass loss of BDE-209 during the thermal treamtnet is mainly caused by the evaporation and thermal decomposition.
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Authors: Kumar S. Arun, A. Sekar, K.V. Govinda
Abstract: In general, aerostatic bearings are flat bearings and the stringent manufacturing tolerances in geometric dimensions and profile will make the bearing ideal for obtaining high stiffness during measurement. Aerostatic Spherical Bearing (ASB) on the contrary is a special bearing which provides a frictionless pivot and allows three degrees of rotational freedom. Methods involved in manufacturing and realizing a highly stiff ASB is discussed in this paper. ASB components viz. Stator and Rotor of hemi-spherical in geometry are the critical components to be machined, which are used in Mass properties and Dynamic Balancing Measurement machine (MaPDBM). MaPDBM is used to measure mass, center of gravity, moments of inertia and static & dynamic unbalance of spacecraft. An air film of 25-50 μm thickness separates the stator and rotor during measurement, thus forming an aerostatic bearing. Precise Machining, Thermal treatments to ensure crash-proof design, Special processes like lapping for profile correction, Geometrical and profile measurements during different stages in the sequence for controlling the bearing parameters using Coordinate Measurement Machine (CMM) are the challenges involved in the machining and realization of the ASB components and the same is discussed in this paper.
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Authors: E. Evangelista, Marcello Cabibbo, S. Spigarelli, C. Scalabroni, Luigi Balloni, R. Villa, G.L. Chiarmetta
Abstract: The tensile properties and the microstructure of an Al-7%Si-0.6%Mg-0.5%Cu rheo-cast component were investigated. The material underwent a T5 treatment, consisting in ageing at 160, 175 and 190°C for durations ranging from 0.5 to 48h. Tensile testing indicated that the T5 treatment resulted in a relatively good level of strength and in a comparatively low ductility. In order to improve ductility, maintaining as low as possible the cost of the final component, a single solution treatment at 500°C for 4h was subsequently applied. The tensile strength and ductility of the solution treated and aged material were higher than in the T5 condition. These differences were attributed to the microstructural evolution occurring during exposure at 500°C, in particular to the spheroidization of eutectic-Si and to a more homogeneous distribution of the precipitates.
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Authors: Satoshi Hayakawa, K. Shibata, Kanji Tsuru, Akiyoshi Osaka
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Authors: K. Shibata, Kanji Tsuru, Satoshi Hayakawa, Akiyoshi Osaka
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Authors: Fan Sun, D. Mantovani, Frédéric Prima
Abstract: L605 (ASTM F90), a cobalt-chromium-tungsten alloy with excellent mechanical properties and high radiopacity, has been widely accepted as a suitable alloy for stent applications. The presence of carbides in this alloy, primary carbides and secondary carbides, leads to difficulties in controlling mechanical performances and therefore in optimizing stent size and performances. This work is thus to investigate the carbides and their role in advanced mechanical properties of L605 alloy for stent fabrication. Herein, the nature, nucleation, distribution and dissolution of the carbides were investigated in a series of recrystallized L605 tubes from hard-drawn (HD) state. The mechanical properties corresponding to each carbide state were examined by tensile tests and microhardness measurements. The results indicate important relationships among carbide precipitation, grain size and mechanical behaviors, as a function of annealing temperature and duration. The intergranular secondary carbides, induced at the onset of the recrystallization of L605 matrix, were preferentially precipitated at grain boundaries. The nucleation of such particulate phase leads to a pinning effect on grain coarsening, resulting in a strengthening effect of the material. However, the further growth of the secondary carbides brings about considerable reduction of ductility, which is inacceptable for stent application. Therefore, an optimization protocol on carbides controlling was developed to maintain the strengthening effect without losing ductility and small grain size.
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Authors: Jan Spišák, Martin Truchlý, Ján Mikula, Vratislav Šindler
Abstract: During procedure and heat treatment of magnesite in shaft and rotary furnaces, a great number of fine fractions are generated. In terms of MgO content, the fractions comprises the highest quality raw material. However, the desired degrees of calcination or sintering have not been achieved. For direct heat treatment of fine particles the microfluidic furnace has been proposed. The microfluidic furnace consists of the fluidization chambers in which the technology operations are being carried out. The furnace operates on the counter-current principle. The experiments of dust magnesite and flue gas calcination from rotary and shaft furnaces were carried out in the furnaces.
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