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Florianópolis, Brazil

Lopes D.A.,LABMAT | Restivo T.A.G.,Uniso | Restivo T.A.G.,University of Sao Paulo | Padilha A.F.,University of Sao Paulo
Defect and Diffusion Forum

Metallic nuclear fuel plates are nowadays an alternative to the ceramic ones in the sense that the uranium density can be increased at lower enrichment. Higher thermal conductivity is also a key factor favouring such fuels for power reactors. Uranium reacts promptly with oxygen and nitrogen at high temperatures to catastrophic corrosion due to non-protective oxide layers, which imparts hot forming processes. The gamma phase body centred cubic structure can be retained at room temperature by annealing the U-7.5Nb-2.5Zr (wt.%) alloy followed by quenching, where the deformation can be extensive. The resulted highly deformed gamma supersaturated structure is subjected further to competitive recovery/recrystallization and phase precipitation phenomena whose are studied in the work. The U-7.5Nb-2.5Zr alloy was melted into plasma and induction furnaces and afterwards annealed to gamma phase. The normalized alloy was cold rolled and underwent isochronal and isothermal treatments. The microstructure evolution was monitored by optical microscopy, X-ray diffraction analysis and hardness measurements. The results show the precipitation events of α" and α+γ3 phases are dominant over recovery in the range 200°C < T < 500°C. Above 500°C the recrystallization is the main process leading to softening and initial Vickers hardness recovery. One refined gamma phase grain structure was obtained (∼8.0 μm) after annealing at 700°C for 2.5 hours. © (2014) Trans Tech Publications, Switzerland. Source

Muller D.,LABMAT | Garcia M.,LABMAT | Salmoria G.V.,LABMAT | Pires A.T.N.,Federal University of Santa Catarina | And 2 more authors.
Journal of Applied Polymer Science

In this study, the electromechanical and dynamic mechanical properties of electrically conducting polymer blends were investigated. The blends were comprised poly(styrene-b-butylene-ran-ethylene-b-styrene) (SEBS) containing polypyrrole doped with dodecylbenzenesulfonic acid (PPy.DBSA). The two types of PPy.DBSA (with and without an excess of DBSA) were blended with SEBS through the solution casting method at room temperature. The dynamic mechanical characterization of the SEBS/PPy.DBSA blends demonstrated that the use of PPy.DBSA with and without free DBSA molecules results in different degrees of interaction with the two phases of the SEBS copolymer matrix. The changes in the electrical conductivity of the blends during repeated pressure loading/unloading were investigated. The conducting SEBS/PPy.DBSA polymer blends exhibited an increase in the electrical conductivity on pressure loading and underwent a corresponding decrease on unloading. © 2010 Wiley Periodicals, Inc. Source

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