Influence of aged Ti-15V-3Cr-3Sn-3Al alloy microstructure on chemical and electrochemical behavior in the Kroll reagent for metallographic etching

The chemical and electrochemical behaviour of the Ti-1 5V-3Cr-3Sn-3Al alloy in Kroll reagent has been studied after ageing at 350-600degreesC, to optimise metallographic etching. Etching tests and polarisation curves showed that samples aged at higher temperatures have been more susceptible to corrosion. It has been attributed to the formation of intra- and intergranular alpha-phase precipitates during ageing.

Conventional and microwave sintering of CaCu(3)Ti(4)O(12)/CaTiO(3) ceramic composites: non-ohmic and dielectric properties

The non-ohmic and dielectric properties as well as the dependence on the microstructural features of CaCu(3)Ti(4)O(12)/CaTiO(3) ceramic composites obtained by conventional and microwave sintering were investigated. It was demonstrated that the non-ohmic and dielectric properties depend strongly on the sintering conditions. It was found that the non-linear coefficient reaches values of 65 for microwave-sintered samples and 42 for samples sintered in a conventional furnace when a current density interval of 1-10 mA cm(-2) is considered. The non-linear coefficient value of 65 is equivalent to 1500 for samples sintered in the microwave if a current interval of 5-30 mA is considered as is shortly discussed by Chung et al (2004 Nature Mater. 3 774). Due to a high non-linear coefficient and a low leakage current (90 mu A) under both processing conditions, these samples are promising for varistor applications. The conventionally sintered samples exhibit a higher relative dielectric constant at 1 kHz (2960) compared with the samples sintered in the microwave furnace (2100). At high frequencies, the dielectric constant is also larger in the samples sintered in the conventional furnace. Depending on the application, one or another synthesis methodology is recommended, that is, for varistor applications sintered in a microwave furnace and for dielectric application sintered in a conventional furnace.

Preparation of Ni-Ti-Mo and Ni-Ti-Mo-Zr Alloys by High-Energy Ball Milling and Subsequent Hot Pressing

This work discusses on the preparation of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr (at-%) alloys by high-energy ball milling and hot pressing, which are potentially attractive for dental and medical applications. The milling process was performed in stainless steel balls (19mm diameter) and vials (225 mL) using a rotary speed of 300rpm and a ball-to-powder weight ratio of 10:1. Hot pressing under vacuum was performed in a BN-coated graphite crucible at 900 degrees C for 1 h using a load of 20 MPa. The milled and hot-pressed materials were characterized by X-ray diffraction, electron scanning microscopy, and electron dispersive spectrometry. Peaks of B2-NiTi and Ni4Ti3 were identified in XRD patterns of Ni-45Ti-5Mo, Ni-40Ti-10Mo and Ni-46Ti-2Mo-2Zr powders milled for 1h. The NiTi compound dissolved small Mo amounts lower than 4 at%, which were measured by EDS analysis. Moreover, it was identified the existence of an unknown Mo-rich phase in microstructures of the hot-pressed Ni-Ti-Mo alloys.

Structural Evaluation of Mechanically Alloyed and Heat-Treated Ti-25at-%Si Powders

This work discusses on the structural evaluation of mechanically alloyed and heat-treated Ti-25at%Si powders. The milling process was conducted in a planetary ball mill using stainless steel balls/vials, 200 rpm and ball-to-powder weight ratio of 5:1, whereas the heat treatment was conducted under Ar atmosphere at 1100 C for 4 h. Samples were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy and energy dispersive spectrometry. The Si peaks disappeared after milling for 30h, indicating that the Si atoms were dissolved into the Ti lattice in order to form an extended solid solution. The Ti peaks were broadened and their intensities reduced for longer milling times whereas a halo was formed in Ti-25Si powders milled for 200h suggesting that an amorphous structure was achieved. The crystallite size was decreased with increasing milling times. A large Ti3Si amount was found in mechanically alloyed Ti-25at%Si powders after heating at 1100 degrees C for 4h.

Surface characterization of Ti-7.5Mo alloy modified by biomimetic method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of the microwave oven on structural, morphological and electrical properties of SrBi4Ti4O15 thin films grown on Pt/Ti/SiO2/Si substrates by a soft chemical method

Thin films of SrBi4Ti4O15 (SBTi), a prototype of the Bi-layered-ferroelectric oxide family, were obtained by a soft chemical method and crystallized in a domestic microwave oven. For comparison, films were also crystallized in a conventional method at 700 degrees C for 2 h. Structural and morphological characterization of the SBTi thin films were investigated by Xray diffraction (XRD) and atomic force microscopy (AFM), respectively. Using platinum coated silicon substrates, the ferroelectric properties of the films were determined. Remanent polarization P-r and a coercive field E-c values of 5.1 mu C/cm(2) and 135 kV/cm for the film thermally treated in the microwave oven and 5.4 mu C/cm(2) and 85 kv/cm for the film thermally treated in conventional furnace were found. The films thermally treated in the conventional furnace exhibited excellent fatigue-free characteristics up to 10(10) switching cycles indicating that SBTi thin films are a promising material for use in non-volatile memories. (C) 2007 Elsevier B.V. All rights reserved.

Effect of WC-10%Co-4%Cr coating on the Ti-6Al-4V alloy fatigue strength

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fibroblast functionality on novel Ti-30Ta nanotube array

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Three-Dimensional Characterization of Pores in Ti-6Al-4V Alloy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural Evaluation of Mechanically Alloyed (67-x)Ti-xZr-22Si-11B Powders

The present work reports on the structural evaluation of mechanically alloyed Ti-xZr-22Si-11B (x = 5, 7, 10, 15 and 20 at-%) powders. Milled powders and hot-pressed alloys were characterized by X-ray diffraction, electron scanning microscopy, and electron dispersive spectrometry. The Si and B atoms were preferentially dissolved into the Ti and Zr lattices during ball milling of Ti-xZr-22Si-11B (x = 7, 10, 15 and 20 at-%) powders, and extended solid solutions were achieved. The displacement of Ti peaks was more pronounced to the direction of lower diffraction angles with increasing Zr amounts in mechanically alloyed Ti-Zr-Si-B powders, indicating that the Zr atoms were also dissolved into the Ti lattice.

Surface Corrosion of Ti-16Si-4B Powder Alloy Implanted With Nitrogen by Plasma-Based Technique

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fatigue fracture behavior of Ti-6Al-4V PVD coated

Fatigue, corrosion and wear resistance are important parameters in aircraft components development as landing gear. High strength/weight ratio and effective corrosion resistance make of titanium alloys an alternative choice to replace steel and aluminum alloys. However, titanium alloys have poor tribological properties, which reduce devices performance under friction. PVD coatings tribological systems has been increased due to their attractive mechanical properties as low environmental impact, low friction coefficient, low wear rate and hardness up to 2000 HV.In this study the influence of TiN deposited by PVD on the fatigue strength of Ti-6Al-4V alloy was evaluated. Comparison of fatigue strength of coated specimens and base material shows also a decrease when parts are coated. It was observed that the influence is more significant in high cycle fatigue tests. Scanning electron microscopy technique (SEM) was used to observe crack origin sites and fracture features. (C) 2010 Published by Elsevier Ltd.

Fatigue behavior of PVD coated Ti-6Al-4V alloy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Motivações para adoção: uma perspectiva da Psicologia Evolucionista

Parental investment increases the offspring s survival, though it decreases the opportunities for the parents to invest in a future progeny. In a broad sense, this investment is directed to one s own descendant, but in some cases, such as in adoption, resources are directed to non-relatives even in the absence of fitness benefits. Once there are many factors involved in adoption, this study investigated adopters candidates, aiming to analyze aspects considered by them for adopting, based on the Evolutionary Psychology s perspective. We analyzed the judicial proceedings´ files people who had been inlisted for adoption at the 2ª Childhood and Adolescence Law Court, Natal-RN. The adopter s motivations were classified into biological or social reasons. A relationship between adopters´ age and kind of motivation was found: requirements of young people were related to biological reasons while requirements of the old ones were related to social reasons. Fertility, mainly female requirer´s fertility, underlie this relationship, considering that women fertility is strongly influenced by age. The reasons to adopt were also related to the age of the desired child, once that people who wanted children older than 25 months alleged social reasons while those that wanted younger babies alleged biological reasons. There are lots of motives to adopt a child, but the phenomenon of adoption is broadly acknowledged by society as an act of love and the adoptive parents are often regarded as kind and generous people. It was observed, instead, that the reasons to adopt comes from the adopters themselves, related to the fulfillment of personal needs, such as increasing the family, carrying out mother/father role or having a company or someone to care form them in elderly age

Do útero à adoção: a experiência de mulheres férteis que adotaram uma criança

Even with all changes and ruptures related to the social roles that woman had performed, the literature had confirmed that the motherhood still configures it like one of the main roles that she hopes to play in some moment of her life. When the woman did not get pregnant or take ahead a pregnancy, some women find in adoption an alternative to play this role. This research aimed to understand the experience of being mother for adoption in the case of fertile women, but whose partner is infertile. Supported by existential-phenomenological theory, used it the narrative, how methodological instrument. Participated five women, whose adoption process followed the legal ways in the Youngness and Infancy Judgeship of Natal/RN. The results showed that in the selfish training, the woman to see herself how whose role principal is to generate children, although, she think that is natural her participation in others activities go out home too. In male infertile case is a tendency that the woman strikes the infertile status too. The adoption is an alternative to fulfill her desire of being a mother and, meanwhile, please her husband and guarantee the continuity of her love relationship. Through motherly care, the woman discover herself as a mother, what brings a new meaning for her live, independent of to generate a child. Though, exit frustration, sometimes, in association with suffering, on account of the pregnancy and childbirth absence. The end of the research suggests reflections that to become fulfilled herself as mother, the woman does not need, necessarily, to generate a child, being the maternity one of the uncountable possibilities that are shown, and that she can choose, or not, accomplish it