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Fracture toughness of dense cordierite: sintering cycle effect
Oliveira, F. A. Costa; Fernandes, Jorge Cruz; Schmitt, Julien; Rosa, Luís Guerra; Dias, DiamantinoThe aim of this work was to analyse the fracture behaviour of commercial dense cordierite bodies sintered in an electrical furnace in static air at 1250ºC, 1275ºC and 1300ºC for 30 min using different cycling schedules in order to obtain tougher materials at minimum energy costs. Using a stereomicroscope and a scanning electron microscope, fracture surfaces of as-sintered bars tested under four-point bending at...
Synthesising carbo-nitrides of some d-group transition metals using a solar fur...
Shohoji, Nobumitsu; Oliveira, F. A. Costa; Rosa, Luís Guerra; Fernandes, Jorge Cruz; Magalhães, Teresa; Coelho, Manuel Caldeira; Rodriguez, JoséCarbo-nitride synthesis was undertaken using a solar furnace at PSA in flowing N2/Ar gas mixture under total pressure 1 atm and processing temperature T = 1600ºC for some d-group transition elements (Ti; Zr, V, Nb, Mo, W) starting from 1.5G/M (graphite/metal powder mixture with mole ratio 1.5:1) compact to ensure co-presence of free carbon with the reaction product. Clear X-ray diffraction (XRD) evidence of for...
Synthesizing higher nitride of molybdenum (Mo) and iron (Fe) in ammonia (NH3) g...
Shohoji, Nobumitsu; Oliveira, F. A. Costa; Fernandes, Jorge Cruz; Rosa, Luís Guerra; Rodriguez, José; Canadas, Immaculada; Ramos, CarlosFlowing gaseous ammonia NH3 with suppressed extent of dissociation (un-cracked NH3) is acknowledged to function as a powerful nitriding medium to realize formation of metal nitride MNx with considerably high N/M ratio x that cannot be achieved through reaction of M with N2 gas. For example, mono-nitride d-MoN of Mo and e-FeNx phase of Fe with x = 0.33 ˜ 0.50 (i. e. hypo-stoichiometric sub-nitride e-Fe2N) were r...
Heterogeneity along the Height in Disc Specimens of Graphite/Tungsten Powder Mi...
Shohoji, Nobumitsu; Magalhães, Teresa; Oliveira, F. A. Costa; Rosa, Luís Guerra; Fernandes, Jorge Cruz; Rodriguez, José; Canadas, ImmaculadaCompositional heterogeneity along the thickness of compacted disc specimens of graphite/tungsten powder mixtures with substoichiometric carbon atom ratios (0.35, 0.50 and 1.00) heated by concentrated solar beam to 1600 C was characterised by X-ray diffraction. Top surface of any examined test piece was consisted purely of mono-carbide WC while the bottom surface showed different constitution depending on the ne...
Mechanical properties of dense cordierite discs sintered by solar radiation hea...
Oliveira, F. A. Costa; Shohoji, Nobumitsu; Martinez, Diego; Fernandes, Jorge Cruz; Rodriguez, José; Rosa, Luís Guerra; Canadas, ImmaculadaConsolidation of cordierite disc specimens was undertaken under concentrated solar beam in a solar furnace at PSA (Plataforma Solar de Almerıá). Satisfactory extent of densification was achieved by the present solar-sintering experiment. The mechanical properties measured for the solar-sintered cordierite test pieces were; density ¼ 2:45 0:02 g/cm3, Vickers microhardness HV ¼ 7:31 0:29 GPa, Young’s modulu...
Carbide phases synthesised from C/Mo powder compacts at specified sub-stoichiom...
Granier, Bernard; Shohoji, Nobumitsu; Oliveira, F. A. Costa; Magalhães, Teresa; Fernandes, Jorge Cruz; Rosa, Luís GuerraThere are a number of distinguishable carbide phases in the binary Mo-C system depending on C/Mo ratio as well as on temperature. In a preceding work published in this journal, carbide formation performance for graphite/molybdenum powder mixtures at specified levels of substoichiometric C/Mo atom ratio (C/Mo = 1/1, 3/4, 2/3 and 1/2) by exposure to concentrated solar radiation in a solar furnace at PROMESCNRS in...
Fracture behaviour of a new submicron grained cemented carbide
Oliveira, F. A. Costa; Lopes, A. C.; Fernandes, Jorge Cruz; Sacramento, J.; Valente, M. A.In this work, the effect of increase argon pressure applied on a post-sintering treatment from MPa to MPa on the mechanical properties of a newly developed hardmetal grade, namely hardness, flexural strength and fracture toughness, is reported. The as-received material has been prviously sintered at 1460ºC under 2 MPa argon pressure from powder mixtures of WC and 3,5 wt% Co together with minor additions of VC, ...
Nano-meter size WC whiskers grown over a compacted pellet of praphite: tungsten...
Dias, Susana; Oliveira, F. A. Costa; Granier, Bernard; Badie, Jean Marie; Fernandes, Jorge Cruz; Rosa, Luís Guerra; Shohoji, NobumitsuIn equilibrium binary W-C system, mono-carbide WC is acknowledged as the stable phase under presence of excess free carbon up to temperature 2700 C whereas sub-carbideW2C would form between 1250 C and 2700 C under the carbon-deficiency condition. In unique setup of solar furnace at PROMES-CNRS in Odeillo (France), temperature of specimen is raised from the ambient temperature to target temperature up to 2000 C ...
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