Tratamento térmico em Zamac visando diminuir defeitos de porosidade

O Zamac tem sido utilizado na indústria galvânica, principalmente, devido ao seu baixo ponto de fusão, o que permite a obtenção de peças com riqueza de detalhes, tais como peças do setor moveleiro, moda e metais sanitários. No entanto, os processos de sua obtenção, por injeção sob pressão e injeção centrífuga, geram porosidade e, consequentemente, aumento de sucata. Por outro lado, estudos mostraram que fusão por gravidade não apresenta tais problemas. Nesse sentido, o objetivo deste artigo foi tratar termicamente peças de Zamac injetadas sob pressão, com a finalidade de obter comportamento semelhante às peças fundidas por gravidade. Para tanto, peças injetadas sob pressão foram tratadas termicamente, abaixo da temperatura de fusão. A caracterização morfológica dessas amostras foi obtida por MEV. Observou-se que o tratamento térmico acima da temperatura eutetoide apresentou melhor resultado com respeito à porosidade observada.The Zamac has been used in the galvanic industry mainly due its low fusing point properties, which allows obtaining very detailed parts, like parts for furniture industry, fashion and health metals. However, its production processes, like pressure injection and centrifugal injection, generate an increase in porosity as well as waste. On the other hand, studies show that die casting leaked Zamac doesn’t show the same problems. In this sense, the goal for this work is to perform heat treatment in Zamac parts produced by pressure injection in order to obtain similar properties as the ones produced by die casting leakage. For this, the parts injected under pressure were thermally treated under their fusion temperature. It was observed that thermic treatment over the eutectoid temperature showed the best result, regarding the observed porosity

Tratamento superficial de ligas de nitinol por anodização

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Tratamento superficial de ligas de nitinol por anodização

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A Model for the Formation of Niobium Structures by anodization

The fluoride use for anodizing electrolytes has been primarily responsible for the formation of nanoporous oxides at valve metals, except aluminum, since it causes a dissolution process. This study presents the formation of an oxide model according to the following anodizing parameters: 100 V, 12.73 mA/cm², room temperature and the niobium samples anodized in niobium oxalate and oxalic acid electrolytes without and with the addition of HF for 5, 30 and 60 min. The anodized samples were analyzed morphologically by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM) and the hydrophobicity of the samples was assessed by the sessile drop method. The presence of fluor in the niobium oxalate electrolyte formed oxides with lower a dissolution and a low hydrophobicity compared to the one formed in oxalic acid was attributed to the incorporation of niobium and oxalate ions. Thereby, the model proposed in this paper showed that during anodization the migration of the fluoride ion into the oxide occurs at high speed, which results in the formation of microcones, leading to the formation of discrete layers of porous oxide

The electrochemical behavior of the NiTi alloy in different simulated body fluids

In order to improve the NiTi alloy biocompatibility, surface treatments become very important. Nevertheless, researchers use different solutions to simulate the body fluids in electrochemical assays, and the correlation between the obtained results is difficult and might not even be possible. The present paper evaluated the electrochemical behavior of polished NiTi surfaces exposed to different simulated body fluid solutions: Hanks solution, Hanks’ balanced salt (HBSS) solution, saline body fluid (SBF) solution, and Ringer solution. The electrochemical behavior of NiTi was evaluated by open circuit potential (OCP) and cyclic voltammetry tests. The surfaces of the samples were also characterized by scanning electron microscopy, which was performed after the electrochemical tests. The results demonstrated that the NiTi alloy shows the same corrosion mechanism (pitting) in all simulated body fluids that were studied. However, the corrosion potential changes for each electrolyte, being HBSS, SBF and Ringer the most corrosive solutions. Furthermore, the Hanks and HBSS solutions demonstrated good reproducibility of the electochemical results. Considering that the HBSS represents an extreme environment, this solution seems to be the most indicated to study the corrosion behavior of NiTi treated surfaces

The electrochemical behavior of the NiTi alloy in different simulated body fluids

In order to improve the NiTi alloy biocompatibility, surface treatments become very important. Nevertheless, researchers use different solutions to simulate the body fluids in electrochemical assays, and the correlation between the obtained results is difficult and might not even be possible. The present paper evaluated the electrochemical behavior of polished NiTi surfaces exposed to different simulated body fluid solutions: Hanks solution, Hanks’ balanced salt (HBSS) solution, saline body fluid (SBF) solution, and Ringer solution. The electrochemical behavior of NiTi was evaluated by open circuit potential (OCP) and cyclic voltammetry tests. The surfaces of the samples were also characterized by scanning electron microscopy, which was performed after the electrochemical tests. The results demonstrated that the NiTi alloy shows the same corrosion mechanism (pitting) in all simulated body fluids that were studied. However, the corrosion potential changes for each electrolyte, being HBSS, SBF and Ringer the most corrosive solutions. Furthermore, the Hanks and HBSS solutions demonstrated good reproducibility of the electochemical results. Considering that the HBSS represents an extreme environment, this solution seems to be the most indicated to study the corrosion behavior of NiTi treated surfaces

Study of the effect of the current in the process in the obtaining nanostructured surface of titanium

O emprego do titânio e outras ligas como implantes e próteses têm tido grande repercussão clínica nos últimos anos. No entanto, apesar do êxito clínico, esses biomateriais têm apresentado problemas devido a falhas que podem ocorrer pelo desgaste, fratura ou por reações alérgicas ocasionadas pela presença de íons metálicos dissolvidos ou partículas sólidas desprendidas do implante por fenômeno mecânico. Há inúmeros relatos na literatura demonstrando que a rugosidade da superfície de implantes de titânio afeta a taxa de osseointegração e fixação biomecânica. Nesse contexto, o presente trabalho tem por objetivo estudar o efeito da densidade de corrente no processo de tratamento eletroquímico do Ti visando à obtenção de superfícies nanoestruturadas. Para isso as amostras de Ti foram lixadas mecanicamente e submetidas um processo de tratamento eletroquímico em solução ácida. Nessa etapa do estudo variou-se a densidade de corrente, mantendo fixos os demais parâmetros. Após o processo de tratamento eletroquímico as amostras foram caracterizadas por microscopia de força atômica, perfilometria e ensaios de molhabilidade. Resultados preliminares mostraram que é possível controlar a morfologia de superfícies nanoestruturadas a partir do controle da densidade de corrente.Titanium and its alloys have been widely used in implants and prostheses. However, the clinical success of these biomaterials can be compromised due to failures that can occurs by loss cohesion of tissue, fracture or allergic reactions caused by the presence of dissolved metallic ions or detached solid particles by mechanical factors. Some results presented on the literature have been showed that the surface roughness of the titanium implants affects the osseointegration rate and biomechanical fixation. The present work aims to study the current density effect on the electrochemical treatment of Ti to obtain nanostructured surfaces. The samples were mechanically sanded and electrochemical treatment on acid solution. After the electrochemical treatment the samples were characterized by atomic force microscopy, profilometry and wettability tests. Preliminary results showed that is possible to control the morphology of nanostructured surfaces by electrochemical treatment parameters control

Analysis of the effects of alumina (Al2 O3) addition in micrastructure and hardness in Zamac 5 by gravity

O objetivo deste trabalho foi verificar se é possível a incorporação Al2 O3 à liga de Zamac por meio do processo de fundição por gravidade. Para isto amostras de Zamac foram fundidas em triplicata, sem e com adições de 0,1%, 0,5% e 7% em massa de óxido de alumínio. Análises ao Microscópio Eletrônico de Varredura (MEV), medição dos tamanhos de grão e ensaio de dureza das amostras fundidas foram realizados para validação da incorporação da alumina à liga. Após analisar os resultados, verificou-se que a alumina foi satisfatoriamente incorporada à liga. No entanto, a incorporação de Al2 O3 foi baixa e em forma de clusters. Ainda foi verificado que a adição de alumina não causou alterações na microestrutura da nova liga, entretanto, quando comparada com a amostra sem adição de alumina, foi constatado um aumento de 4% na dureza da amostra fundida com 7% de Al2 O3.The objective of this work was to verify if it is possible to incorporate aluminum oxide into the Zamak alloy through the die casting process. For this purpose Zamak samples were melted in triplicates, without and with additions of 0.1%, 0.5% and 7% by mass of aluminum oxide. Scanning Electronic Microscopy (SEM) analysis, grain size measurements as well as hardness tests were performed in order to validate the incorporation of the alumina to the Zamak alloy. After analyzing the results, it was verified that the alumina was satisfactorily incorporated into the alloy. Besides that, there was a low oxide incorporation, and in the form of clusters. It was also verified that the alumina added did not cause changes in the new alloy’s microstructure, however, when compared with the pure sample, an increase of 4% in the hardness of sample casted with 7% of Al2 O3 was found