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De Almeida L.H.,Federal University of Rio de Janeiro | Bastos I.N.,State University of Rio de Janeiro | Santos I.D.,Instituto Tecnologico Vale Vale S.A. | Dutra A.J.B.,Federal University of Rio de Janeiro | And 3 more authors.
Journal of Alloys and Compounds | Year: 2014

Metastable β-Ti alloys combine low elastic modulus, excellent mechanical strength as well as good corrosion resistance. Wherever, the presence of nontoxic elements such as Nb, Ta, Mo, and Zr is an important advantage. With such properties this type alloy has been developed for orthopedic applications. Previous studies had shown that the Ti-12Mo-13Nb and Ti-10Mo-20Nb alloys aged at 500 °C presented higher hardness/elastic modulus ratio compared to commercially Ti-6Al-4V, indicating a great potential for biomedical application. However, additional studies are needed such as corrosion resistance. Therefore, the objective of this work was to analyze the electrochemical behavior of the Ti-12Mo-13Nb and Ti-10Mo-20Nb alloys aged at 500 °C/24 h and 500 °C/4 h, respectively. The electrochemical behavior was carried through by potentiodynamic polarization curves in Ringer's solutions to simulate the body fluid. The Ti-10Mo-20Nb alloy showed to be more resistant to corrosion when compared to Ti-12Mo-13Nb alloy and the commercially Ti-6Al-4V alloy. © 2014 Elsevier B.V. All rights reserved.

Gabriel S.B.,Federal University of Rio de Janeiro | Gabriel S.B.,Centro Universitario Of Volta Redonda | De Almeida L.H.,Federal University of Rio de Janeiro | Nunes C.A.,University of Sao Paulo | And 2 more authors.
Materials Science and Engineering C | Year: 2013

Alloys for orthopaedic and dentistry applications require high mechanical strength and a low Young's modulus to avoid stress shielding. Metastable β titanium alloys appear to fulfil these requirements. This study investigated the correlation of phases precipitated in a Ti-12Mo-13Nb alloy with changes in hardness and the Young's modulus. The alloy was produced by arc melting under an argon atmosphere, after which, it was heat treated and cold forged. Two different routes of heat treatment were employed. Phase transformations were studied by employing X-ray diffraction and transmission electron microscopy. Property characterisation was based on Vickers microhardness tests and Young's modulus measurements. The highest ratio of microhardness to the Young's modulus was obtained using thermomechanical treatment, which consists of heating at 1000 C for 24 h, water quenching, cold forging to reduce 80% of the area, and ageing at 500 C for 24 h, where the final microstructure consisted of an α phase dispersed in a β matrix. The α phase appeared in two different forms: as fine lamellas (with 240 ± 100 nm length) and massive particles of 200-500 nm size. © 2013 Elsevier B.V.

Senna A.R.,Centro Universitario Of Volta Redonda | Mugnai R.,Federal University of Rio de Janeiro | Reddy Y.R.,Acharya Nagarjuna University
Zoologia | Year: 2013

A new amphipod species of Bogidiellidae Hertzog, 1936 is described and illustrated based on specimens collected from bore wells in the state of Andhra Pradesh, Southern India. The new species is closely related to those belonging to a group of Bogidiella species with inner rami of pleopods reduced or absent. Bogidiella totakura sp. nov. differs from all the other species in the group mainly by the shape, size and ornamentation on gnathopods and telson. This is the second Indian species of Bogidiella.

Abrunhosa P.A.,Federal Rural University of Rio de Janeiro | Wogel H.,Centro Universitario Of Volta Redonda | Pombal Junior J.P.,Federal University of Rio de Janeiro
Journal of Natural History | Year: 2014

Coexistence of anuran species might lead to acoustic interference among communications, especially where species are closely related. This problem might be minimized through resource partitioning. To test this idea, we analysed calling with respect to temporal and physical space usage in three syntopic, closely related species (Scinax cuspidatus, Scinax aff. hayii and Scinax aff. x-signatus) in a temporary pond in the Atlantic rainforest. The chorus attendance of each species resulted from a different combination of factors in the rainy season. Although there was some temporal overlap of daily activity among species, peak activity time differed, particularly between the two species whose calls were most similar. Although all three species tend to aggregate in open microhabitats, their coexistence is apparently facilitated by differential use of vertical strata and organization of calling sites near the sites of conspecifics. Together, these factors apparently reduce acoustic interference among heterospecific calls. © 2014, © 2014 Taylor & Francis.

Azevedo e Silva P.R.S.,University of Sao Paulo | Baldan R.,University of Sao Paulo | Nunes C.A.,University of Sao Paulo | Coelho G.C.,University of Sao Paulo | And 2 more authors.
Materials Characterization | Year: 2012

MAR-M247 superalloy has excellent mechanical properties and good oxidation resistance at elevated temperatures. Niobium is an element known as γ' phase hardener in nickel-based superalloys, besides promoting homogeneous distribution of MC carbides. This work is inserted in a project that aims to evaluate the total replacement of tantalum by niobium atoms in MAR-M247 superalloy (10.2 Co, 10.2 W, 8.5Cr, 5.6 Al, 1.6 Nb, 1.4 Hf, 1.1 Ti, 0.7 Mo, 0.15 C, 0.06 Zr, 0.015 B, Ni balance-wt.%). Based on microstructural characterizations (SEM and FEG-SEM, both with EDS) of the as-cast material and heat-treated materials as well as utilizing Thermocalc simulations and experiments of differential thermal analysis (DTA), heat-treatment at 1260. °C for 8. h was chosen as an ideal condition for the solution of Nb-modified MAR-M247 superalloy. The hardness of as-cast and ideally solution treated materials was 390. ±. 14. HV and 415. ±. 6. HV, respectively. © 2012 Elsevier Inc.

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