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AVALIA O DA INTEGRIDADE ESTRUTURAL DO CRAVAMENTO EM COLUNAS DE DIRE O
Alexandre Santos Francisco,Ivan Napole？o Bastos
Engevista , 2008,
Abstract: Several parts of automotive steering columns are fixed by both dimensional interference and mechanical-plastic sticking of one part to another. To determine the effect of these fixing procedures on the joints of steering columns, pull-out tests were performed. Samples with and without sticking were tested. The influence of the sticking and interference procedures on the integrity of the steering columns was experimentally determined by force-distance curves. The results suggested that the sticking increases more than twice the pull-out force and augments about 24% the absorbed energy in the whole pull-out process. Statistical fitting tests show that pull-out forces obey a log-normal distribution. From these data were possible to estimate the structural reliability of joints of steering columns, which results indicate that the fail probability is close to zero for a minimum pull-out force of 2000 N. This work allows for knowing the importance of the sticking procedure in the fixation of automotive pieces, and establishing new standards for the assembly of steering columns in mechanical and statistical basis.
Rotas de obten？？o de ceramica de niobatos de potássio
Andrade, M？nica Calixto de;Bastos, Ivan Napole？o;Ogasawara, Tsuneharu;
Rem: Revista Escola de Minas , 2003, DOI: 10.1590/S0370-44672003000400009
Abstract: this work presents a thermodynamic analysis from ceramic processing point of view to obtain photoluminescent potassium niobate ceramic. the analysis carried out indicated the conditions of ph which the route of processing by chemical precipitation would be done. therefore, the presence of chemical elements ca, la, k, nb and eu in aqueous medium was considered on potential and solubility parameters at room temperature.
Rotas de obten o de ceramica de niobatos de potássio
Andrade M？nica Calixto de,Bastos Ivan Napole？o,Ogasawara Tsuneharu
Rem: Revista Escola de Minas , 2003,
Abstract: Esse artigo apresenta a análise termodinamica do ponto de vista do processamento ceramico para a obten o de niobatos de potássio. A análise realizada indicou as condi es de pH em que seria possível produzir insumos ceramicos fotoluminescentes por rotas de precipita o química. Para tanto foram consideradas as presen as dos elementos químicos Ca, La, K, Nb e Eu em meio aquoso à temperatura ambiente, que foram estudados considerando os parametros potencial e a solubilidade.
Theoretical and Experimental Aspects of the Corrosivity of Simulated Soil Solutions
Rodrigo Antunes de Sena,Ivan Napoleão Bastos,Gustavo Mendes Platt
ISRN Chemical Engineering , 2012, DOI: 10.5402/2012/103715
Abstract:
DETERMINA O ESTRUTURAL DA HIDROXIAPATITA POR SíNTESES DE FOURIER E MéTODO DE RIETVELD
Jorge Correa de Araújo,Ivan Napole？o Bastos,Glória Dulce Almeida Soares
Engevista , 2010,
Abstract: The calcium hydroxyapatite is an inorganic material present in bone tissue and widely used as biomaterial. A sample of hydroxyapatite was synthesized by using solutions containing calcium and phosphate ions and its crystalline structure was analyzed by X-ray diffraction by means of Rietveld′s method. A Pearson VII function was used to fit the peak profiles of X-ray diffraction. The structural model obtained by the refinement of individual isotropic thermal factor by atom show a good agreement between the employed model and the observed crystalline structure when evaluated by the reliable index and the D-Fourier synthesis, with . The D-Fourier synthesis seems to confirm the absence of stranger atoms in the arrangement of the hydroxyapatite crystals.
Theoretical and Experimental Aspects of the Corrosivity of Simulated Soil Solutions
Rodrigo Antunes de Sena,Ivan Napole？o Bastos,Gustavo Mendes Platt
ISRN Chemical Engineering , 2012, DOI: 10.5402/2012/103715
Abstract: Corrosion of buried steel pipe is a permanent engineering problem and, albeit the counter measures against degradation, when the corrosion process takes place, the damage has costly impact. In order to study the corrosion behavior of pipelines, it is possible to use actual soil extracts or simulated soil solutions. The extract is much related to specific sites and consequently too strict to permit a general understanding. The simulated soil presents, as advantage, its inorganic characteristic and easy preparation. In this paper, we present some theoretical results concerning the chemical equilibria of NS1, NS2, NS3, and NS4 simulated soil solutions. Besides, we have studied the effect of the above four media in corrosion behavior and polarization curves were performed for an API 5L X65 steel. The theoretical findings show that each ionic concentration varies for a 6–12 pH range. The experimental data suggested that the corrosion currents decrease as high is the pH and increase as high is the chloride content. Notwithstanding these facts, for multielectrolyte solutions, a simple correlation with a given ion is not straightforward but the complementary approaches used here give useful insights. 1. Introduction Carbon steels of buried pipelines are susceptible to degradation by soil corrosivity. Therefore, this situation causes worldwide safety and economy concerns. The uses of coating and cathodic protection are the standard procedures. However, during in-service period, this coating can suffer localized failures and the steel is exposed to a corrosive environment. Generally, the degradation occurs as transgranular or intergranular stress corrosion cracking or even as hydrogen embrittlement in carbon dioxide environment because of mechanical stress. Few works are devoted to investigate corrosion processes caused by aqueous solutions without carbon dioxide. In this sense, marked reductions in area were observed near corrosion potentials of API 5L X65 when performed in slow strain rate test [1]. This fact shows that, even without CO2, the corrosion behavior close to free potential is related to stress corrosion cracking. To study the corrosivity of soil environments by ordinary electrochemical methods, two media are frequently used—extract solution from soil samples and simulated ones. The first option is very complex because it can contain, besides inorganic species, organic chemicals and even bacteria. Albeit their high correlation with the site where the pipe is buried, its use is not applied everywhere precisely because of inherent local
Visualization of EIS at large potential range - new insights
Ivan Napole？o Bastos,Marcos Paulo Moura Carvalho,Ricardo Fabbri,Ricardo Pereira Nogueira
Physics , 2013,
Abstract: Electrochemical Impedance Spectroscopy (EIS) is an experimental technique largely used in electrochemistry and corrosion studies. However, almost all published papers have just measured the EIS at the corrosion potential, especially for corrosion purposes. This fact limits the capability of the technique. In this paper, a Scilab software was developed which allows the visualization of multiple EIS diagrams regarding the potential, exposure time or experiment run. This procedure was applied to austenitic stainless steels in two electrolytes from cathodic to anodic potentials. The EIS maps with two- or three- dimensions were very useful to depict the evolution of the surface with respect to the large range of applied potential. Some results are shown to highlight the usefulness of this approach as a complementary technique to the DC test performed at a given potential range.
Development and characterization of 5% mol Zn bioceramic in granular form
Lima, Ingrid Russoni de;Costa, Andrea Machado;Bastos, Ivan Napole？o;Granjeiro, José Mauro;Soares, Gloria de Almeida;
Materials Research , 2006, DOI: 10.1590/S1516-14392006000400010
Abstract: hydroxyapatite (ha) is capable of accepting substitute ions within its lattice, including zinc ions. zinc is a trace element that activates the osteogenesis of osteoblastic cells and therefore plays an important role in the activity of alkaline phosphatase enzyme. the purpose of this work was to produce and characterize 5% mol zn bioceramic in granular form (zn-granules) for clinical applications and compare it with granules made from ha by using the same production route. granules with addition of porogen agents were produced from powders of ha and zinc-containing ha by uniaxial pressing and heat treatment. the granules were subsequently ground and sieved. the results indicated that zinc contributed to the reduction of sample crystallinity and formed a biphasic structure after calcination at 1200 °c. additionally, zinc release from granular material may have clinical applications as bone graft.
Síntese da hidroxiapatita e refinamento estrutural por difra？？o de raios-x
Araújo, Jorge Correa de;Sena, Lídia;Bastos, Ivan Napole？o;Soares, Glória Dulce de Almeida;
Química Nova , 2007, DOI: 10.1590/S0100-40422007000800011
Abstract: a sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by x-ray diffraction by means of the rietveld method. two functions were used to fit the peak profiles, modified voigt (tchz) and pearson vii. the occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. the interatomic distances from ca1 to oxygens o1, o2 and o3 were adequate for a pure hydroxyapatite without defect at site ca1. besides, the use of multiple lines in planes (300) and (002) associated with the model pearson vii resulted in good agreement with the tchz model with respect to the size-strain effectswith an ellipsoidal shape of crystallites. in conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. the experimental results of transmission electron microscopy confirmed the predicted shape of crystals.
Influence of siderurgical slag on productivity and crop growth of irrigated sugarcane
Lúcio Bastos Madeiros,Andréia de Oliveira Vieira,José Dantas Neto,Napole？o Esberard de Macêdo Beltr？o
Engenharia Ambiental : Pesquisa e Tecnologia , 2008,
Abstract: The main goal of this research was to evaluate the influence of siderurgical slag and irrigation depth on the growth and productivity of sugarcane. The experiment was installed at county of Sao Sebastiao, state of Alagoas, Brazil, on the soil Dystrophic Agrey Argissoil cropped to sugarcane (Saccharum officinarum). The experimental design was bend in randomized blocks in 5x2 factorial scheme with five siderurgical slag doses: 0, 2.5, 5.0, 10.0 and 15.0 t ha-1, five irrigation depth 14.1; 9.5; 5.2; 2.3 e 0.0 mm h-1 and four replications. It was evaluated length, diameter mean, stem number and sugarcane weight. The application 15.92 e 9.84 mm irrigation water for hectare results increasing of length, diameter and stem number. Applications of 2.12; 3.17 e 2.78 t ha-1 of siderurgical slag result increasing of length, diameter mean and stem numbers of sugarcane raising values of 154.29 cm, 22.97 cm e 266 stem, respectively. The sugarcane yield raised 89 t ha-1 with 1,233 mm ha-1 of water apllied, so, the application of this waste on the soil increased the growth and productivity of the irrigated sugarcane.
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