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The present study aims to establish a comparison of corrosion resistance between four (non-commercial) high manganese steel models in relation to 9% nickel steel in an aqueous solution of H2SO4. High manganese steels have emerged as an alternative material for the manufacture of equipment for the storage and transportation of liquefied petroleum gas due to their mechanical properties and mainly for the lower cost compared to 9% nickel steel. The electrochemical techniques used were open circuit potential, linear polarization and electrochemical impedance spectroscopy. The results obtained by these techniques have helped to understand the phenomena that produce a lower corrosion resistance of high manganese steels when compared to 9% nickel steel in aqueous solutions.

The effects of the prior austenite grain sizes in hydrogen embrittlement of Co-containing 18Ni 300 maraging steel were studied employing Slow Strain Rate Testing (SSRT) in 0.6 M NaCl electrolyte under simultaneuos cathodic polarization. The material was susceptible to hydrogen embrittlement in all investigated conditions. In addition, the examination of the fractured surface revealed that the presence of hydrogen in steel promotes the formation of quasi-cleavage regions and hydrogen-induced cracks along the grain boundaries. However, the refining of the prior austenite grain allowed an improvement in the HE resistance. Moreover, EBSD analysis showed that intergranular cracks propagated along to grain boundaries orientated to {001} planes parallel to normal direction, whereas they were deflected on {101} and {111} crystallographic planes.

The electrochemical behavior of solution-annealed grade 300 and grade 350 maraging steels subjected to two different aging temperatures in an aqueous hydrofluoric acid (HF) medium was evaluated. The microstructural and hardness studies showed the effects of the chemical composition and heat treatments on the material properties. Although it is not possible to observe them, the fine intermetallic composites deposited during aging allow a significant increase in the hardness of materials, which was reduced when aged at 560¿°C, where there was formation of reverted austenite. The results showed that, in both steels, solution-annealed samples that were not aged showed a better corrosion behavior than the aged samples. The reversion of austenite during aging at temperatures above 560¿°C increases the phase limits and its susceptibility to corrosion. The greater amount of cobalt and titanium in grade 350 maraging steel increases the amount of fine intermetallic precipitate rich in molybdenum and titanium during aging, therefore improving its mechanical properties, but also reducing its corrosion resistance.

Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows to induce a thin magnetic layer in a mixture of iron, nickel, and cobalt spinel ferrites. On the other hand, the oxide layer presents an adhesive force 99 mN value that shows the capability for being used for tribological applications under sliding contact tests.

We have studied the behavior of the Shubnikov-de Haas oscillations in magnetoresistance under applied magnetic fields with an arbitrary orientation. Different procedures to measure the Lande-g factor have been used in the literature. We propose four unambiguous methods and formulas for the evaluation of this quantity. The Lande-g factor obtained using these formulas compares within the 5% with the reported results of Brosig et al. [1] in InAs – AlSb quantum wells, Bompadre et al. [2] for Bismuth crystals, Kobayashi et al. [3] measuring magnetoresistance as a function of the gate Voltage and F. Fang et al. [4] for InAs – GaSb heterostructure. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:22:20Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:29:07Z : No. of bitstreams: 1 2-s2.0-47649099686.pdf: 693013 bytes, checksum: 28f67b7c41cd0e122b9c1f764aeb048b (MD5) Made available in DSpace on 2014-05-27T11:22:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-01 Hyperthyroidism can result in serious effects on the bone metabolism in humans as well as animals. For a better characterization of thyrotoxicosis effects, 16 cats were induced into thyrotoxicosis by intaking a dose of 150 μg/kg of sodium L-thyroxine every 24 hours during 42 days. The hormonal levels were evaluated by radioimmunoassay technique and the bone mineral density of the right distal radius extremity was measured through the radiographic optical densitometry. Was verified significant bone demineralization seven days of hormonal intake as weel as radius demineralization. Departamento de Zootecnia e Economia Rural Centro de Ciências Agrárias Universidade Federal do Espírito Santo, Alegre - ES Curso de Medicina Veterinária Faculdade Luiz Meneghel, Bandeirantes - PR Departamento de Reprodução Animal e Radiologia Veterinária Faculdade de Medicina Veterinária e Zootecnia Universidade Estadual Paulista, Botucatu - SP Departamento de Bioestatística Faculdade de Medicina Veterinária e Zootecnia Universidade Estadual Paulista, Botucatu - SP Departamento de Reprodução Animal e Radiologia Veterinária Faculdade de Medicina Veterinária e Zootecnia Universidade Estadual Paulista, Botucatu - SP Departamento de Bioestatística Faculdade de Medicina Veterinária e Zootecnia Universidade Estadual Paulista, Botucatu - SP

Aluminum-based composites prepared from pure Al powder and previously Cu metallized graphite are fabricated by a solid state route and are characterized by X-ray diffraction and scanning electron microscopy in order to follow their microstructural evolution. Composites are processed using powder metallurgy technique in order to obtain cylindrical samples to carry out mechanical testing. Microstructural and mechanical characterizations reveal that, by milling, a homogeneous dispersion of insoluble particles into the Al matrix is obtained; this produces an important improvement in hardness and strength with respect to an un-milled sample. Milling intensity and particle concentration have an important effect on the mechanical properties of the synthesized composites.