Terlize Niemeyer - Academia.edu (original) (raw)

Papers by Terlize Niemeyer

As propriedades mecânicas de metais com estrutura cristalina cúbica de corpo centrado (CCC), tais... more As propriedades mecânicas de metais com estrutura cristalina cúbica de corpo centrado (CCC), tais como nióbio e suas ligas, são alteradas de forma bastante significativa com a adição de elementos intersticiais pesados. Estes elementos intersticiais (oxigênio, nitrogênio e carbono) presentes na matriz metálica ocupam sítios octaedrais e constituem um dipolo elástico de simetria tetragonal, podendo produzir relaxações anelásticas. As amostras utilizadas foram policristais da liga Nb-Ti, contendo 0,3% em peso de Ti. As medidas de espectroscopia anelástica foram efetuadas usando um pêndulo de torção invertido, operando com freqüência da ordem de hertz, em um intervalo de temperatura entre 300 e 700 K, com taxa de aquecimento de 1 K/min. Esta dissertação apresenta estruturas de relaxação termicamente ativadas observadas em amostras da liga Nb - 0,3%pTi, contendo diferentes concentrações de oxigênio em solução sólida. Estas estruturas de relaxação foram atribuídas à reorientação induzida ...

Palavras-chave: anelasticidade, atrito interno, efeito Snoek Resumo Átomos de impurezas interstic... more Palavras-chave: anelasticidade, atrito interno, efeito Snoek Resumo Átomos de impurezas intersticiais presentes em metais de transição causam alterações significativas no comportamento anelástico, que se manifestam sob a forma de picos nos espectros de atrito interno como função do inverso da temperatura, conhecidos como Picos de Snoek. Este trabalho apresenta o estudo do comportamento anelástico em amostras de metais de transição, como nióbio, tântalo e molibdênio contendo átomos de elementos intersticiais. As amostras utilizadas foram policristais produzidos através de fusão por feixe de elétrons na Rice University (USA). As medidas de atrito interno foram efetuadas utilizando-se um Pêndulo de Torção invertido operando com freqüência entre 0,1 e 10 Hz, num intervalo de temperatura compreendido entre 300 e 700 K, com taxa de aquecimento em torno de 1,0 K/min. Os resultados mostraram espectros contendo uma estrutura de relaxação que foi atribuída a um processo de relaxação devido a tensões internas provocadas por uma pequena deformação da amostra.

As propriedades mecânicas de metais com estrutura cristalina cúbica de corpo centrado (CCC), tais... more As propriedades mecânicas de metais com estrutura cristalina cúbica de corpo centrado (CCC), tais como nióbio e suas ligas, são alteradas de forma bastante significativa com a adição de elementos intersticiais pesados. Estes elementos intersticiais (oxigênio, por exemplo) presentes na matriz metálica ocupam sítios octaedrais e constituem um dipolo elástico de simetria tetragonal, podendo produzir relaxações anelásticas. Este trabalho apresenta estruturas de relaxação termicamente ativadas observadas em uma amostra da liga Nb-0,3%pTi, contendo 0,08 %p de oxigênio em solução sólida. As medidas de espectroscopia anelástica foram efetuadas usando um pêndulo de torção invertido, operando com freqüência da ordem de hertz, em um intervalo de temperatura entre 300 e 700 K, com taxa de aquecimento de 1 K/min. As estruturas de relaxação obtidas foram atribuídas à reorientação induzida por tensão de átomos intersticiais em torno de átomos da matriz metálica. Tais estruturas foram analisadas e foram encontrados os seguintes processos de relaxação: Nb-O, Ti-O e Nb-N.

The mechanical properties of metaIs with body centered cubic (BCC) crystalline structure such as ... more The mechanical properties of metaIs with body centered cubic (BCC) crystalline structure such as Nb and its alloys, are modified of sufficiently significant form with the addition of heavy interstitial elements. These interstitial elements (oxygen, for example) present in the metallic matrix occupy octahedral sites and constitute an elastic dipole of tetragonal symmetry, being able to produce anelastic relaxation. The used samples were polycrystals of the Nb-Ti alloy, having 0.3 % in weight ofTi. The anelastic spectroscopy measurements were taken using an inverted torsion pendulum, operating with frequency of the order of hertz, in a temperature range between 300 and 700 K, with heating rate of 1 K/min. This dissertation shows thermally activated relaxation structures observed in samples of the Nb-0.3wt.%Ti alloy, having different concentrations of oxygen in solid solution. These relaxation structures were attributed to stress induced ordering of interstitial atoms around the metallic matrix atoms. Such structures were analyzed and were found the following relaxation processes: Nb-O, Ti-O, Nb-N and Nb-C. The results had also shown a direct relation between the intensities of the relaxation structures and the concentration of interstitial elements in the samples.

Mater Res Ibero Am J Mater, 2003

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2016

Key Engineering Materials, 2006

Recent studies have been done to achieve biomedical alloys containing non-toxic elements and pres... more Recent studies have been done to achieve biomedical alloys containing non-toxic elements and presenting low elastic moduli. It has been reported that Ti-Nb-Zr alloys rich in beta phase, especially Ti-13Nb-13Zr, have potential characteristics for substituting conventional materials such as Ti-6Al-4V, stainless steel and Co alloys. The aim of this work is to study the internal friction (IF) of Ti-13Nb-13Zr (TNZ) alloy due to the importance of the absorption impacts in orthopedic applications. The internal friction of this alloy produced by arc melting was measured using an inverted torsion pendulum with the free decay method. The measurements were performed from 77 to 700 K with heating rate of 1 K/min, in a vacuum better than 10-5 mBar. The results show a relaxation structure at high temperature strongly dependent on microstructure of the material. Qualitative discussions are presented for the experimental results, and the possibility of using the TNZ as a high damping material is briefly mentioned.

Defect and Diffusion Forum, 2009

Titanium alloys are excellent implant materials for orthopedic applications due to their desirabl... more Titanium alloys are excellent implant materials for orthopedic applications due to their desirable properties, such as good corrosion resistance, low elasticity modulus, and excellent biocompatibility. The presence of interstitial elements (such as oxygen and nitrogen) causes strong changes in the material’s mechanical properties, mainly in its elastic properties. Study of the interaction among interstitial elements present in metals began with Snoek’s postulate, that a stress-induced ordering of interstitials gives rise to a peak in the mechanical relaxation (internal friction) spectra. In the mechanical relaxation spectra, each species of interstitial solute atom gives rise to a distinct Snoek’s peak, whose temperature and position depend on the measurement frequency. This effect is very interesting because its peculiar parameters are directly related to the diffusion coefficient (D) for the interstitial solute. This paper presents a study of diffusion of heavy interstitial elemen...

Materials Science and Engineering: A, 2005

The mechanical properties of metals with bcc structure, such as niobium and their alloys, are cha... more The mechanical properties of metals with bcc structure, such as niobium and their alloys, are changed of a significant way by the introduction of heavy interstitial elements. These interstitial elements (oxygen, for example) present in the metallic matrix occupy octahedral sites and constitute an elastic dipole of tetragonal symmetry and might produce anelastic relaxation. Polycrystalline samples of Nb-0.3 wt.% Ti (Nb-Ti) alloy with oxygen in solid solution were analysed. The anelastic spectroscopy measurements had been made in a torsion pendulum, with frequencies in the Hz range, in a temperature range between 300 and 700 K. The results showed thermally activated relaxation structures were identified four relaxation process attributed to stress-induced ordering of single oxygen, nitrogen and carbon atoms around niobium and stress-induced ordering of single oxygen atoms around titanium atoms.

Materials Research, 2003

Átomos de oxigênio, presentes em metais com estrutura cristalina cúbica de corpo centrado, são lo... more Átomos de oxigênio, presentes em metais com estrutura cristalina cúbica de corpo centrado, são localizados preferencialmente em sítios octaedrais. Na ausência de uma tensão mecânica externa, estes átomos são distribuídos aleatoriamente. Na presença de oscilações mecânicas, a redistribuição dos átomos nos diferentes sítios deve ocorrer pela interação com esta tensão, levando a perdas na energia elástica. Este trabalho mostra o estudo da interação de átomos de oxigênio presentes em amostras da liga Nb-16% p. Ti, utilizando um pêndulo de torção. Os resultados mostram espectros bastante complexos, que foram decompostos em seus picos constituintes, representando os processos de relaxação devido à reorientação induzida por tensão de átomos e pares de átomos de oxigênio em torno de átomos de nióbio da matriz metálica e átomos de oxigênio em torno de átomos de titânio (interação substitucional-intersticial).

Materials Research, 2002

Metals with bcc structure are able to dissolve large amounts of interstitial element atoms in the... more Metals with bcc structure are able to dissolve large amounts of interstitial element atoms in the form of oxygen. These atoms diffuse through the lattice by jumping into octahedral sites with equivalent symmetry, causing strong alterations in the anelastic behavior. This paper reports on a study of Snoek relaxation in Nb-Ti alloys with oxygen in solid solution, based on internal friction as a function of temperature. The internal friction measurements were taken in a torsion pendulum operating at temperatures in the range of 350 to 650 K, with frequencies varying from 6 to 36 Hz. The results show relaxation spectra in which thermally activated relaxation peaks produced by the stress-induced ordering of oxygen atoms around niobium atoms of the metallic matrix were identified.

Journal of Alloys and Compounds, 2009

Titanium alloys were developed as an alternative to stainless steels and have been extensively us... more Titanium alloys were developed as an alternative to stainless steels and have been extensively used as biomaterials ever since. One of these alloys is Ti-13Nb-13Zr (TNZ), a near-beta phase alloy containing elements with excellent biocompatibility. The main advantage of the TNZ alloy, compared to other titanium alloys, such as Ti-6Al-4V and Ti-6Al-7Nb, widely used as biomaterials, is its low elasticity modulus, closer to that of bone, and the absence of aluminum and vanadium, which have been reported to cause long-term adverse effects. In this paper, the corrosion and electrochemical behavior of TNZ alloy (as cast and after oxygen charge) was studied in a PBS solution. The results showed that, with the oxygen load, there is a significant reduction of the anodic current in almost the whole potential spam explored in this work, meaning that the corrosion rate decreases when the doping is performed.

Titanium is considered the ideal metal for applications in- vivo because of its excellent biocomp... more Titanium is considered the ideal metal for applications in- vivo because of its excellent biocompatibility, having low elasticity modulus and excellent corrosion resistance. As a result, titanium and its alloys have been used by some dec- ades as orthopaedical implants, dentistry implants and medical devices. The Ti-6Al-4V alloy still is the main tita- nium alloy used as biomaterial, but due

In the last 50 years several studies have been made to understand the relaxation mechanisms of th... more In the last 50 years several studies have been made to understand the relaxation mechanisms of the heavy interstitial atoms present in transition metals and their alloys. Internal friction measurements have been carried out in a Nb-Ti alloy containing 3.1 at.% of Ti produced by the Materials Department of Chemical Engineering Faculty of Lorena (Brazil), with several quantities of oxygen in solid solution using a torsion pendulum. These measurements have been performed by a torsion pendulum in the temperature range from 300 to 700 K with an oscillation frequency between 0.5 and 10 Hz. The experimental results show complex internal friction spectra that have been resolved, into a series of Debye peaks corresponding to different interactions. For each relaxation process it was possible to obtain the height and temperature of the peak, the activation energy and the relaxation time of the process.

Materials Science and …, 2009

An implanted material is considered biocompatible, if adverse and uncontrollable reactions don&am... more An implanted material is considered biocompatible, if adverse and uncontrollable reactions don&amp;amp;amp;amp;#x27;t exist in the biological system. In this sense, biocompatibility tests made in the constituent materials are very important so that the implants have success. The in vitro cytotoxicity tests represent the initial phase of the process, and could be considered as a pre-selection of those materials. In vitro

As propriedades mecânicas de metais com estrutura cristalina cúbica de corpo centrado (CCC), tais... more As propriedades mecânicas de metais com estrutura cristalina cúbica de corpo centrado (CCC), tais como nióbio e suas ligas, são alteradas de forma bastante significativa com a adição de elementos intersticiais pesados. Estes elementos intersticiais (oxigênio, por exemplo) presentes na matriz metálica ocupam sítios octaedrais e constituem um dipolo elástico de simetria tetragonal, podendo produzir relaxações anelásticas. Este trabalho apresenta estruturas de relaxação termicamente ativadas observadas em uma amostra da liga Nb-0,3%pTi, contendo 0,08 %p de oxigênio em solução sólida. As medidas de espectroscopia anelástica foram efetuadas usando um pêndulo de torção invertido, operando com freqüência da ordem de hertz, em um intervalo de temperatura entre 300 e 700 K, com taxa de aquecimento de 1 K/min. As estruturas de relaxação obtidas foram atribuídas à reorientação induzida por tensão de átomos intersticiais em torno de átomos da matriz metálica. Tais estruturas foram analisadas e foram encontrados os seguintes processos de relaxação: Nb-O, Ti-O e Nb-N.