Comparative electrochemical study of 5832-9 stainless steel at different media of biological interest

The electrochemical behavior of ISO 5832-9 stainless steel at 37 degrees C in 0.9% NaCl, Ringer Lactate and minimum essential medium (MEM) has been studied, using linear voltammetry, and surface analysis by SEM and EDS. Mechanical and toxicity tests were made. ISO 5832-9 is passivated at corrosion potential (E) and it does not present pitting corrosion on the media studied from to 50 in V above the transpassivation potential (Ei). SEM and EDS analysis have shown that the sample previously immersed in MEM presents a diffirent behavior at 50 in V above El: the manganese oxide inclusions are absent in the surface. E. values and passivation current density values j(pass) changed according to the following. E(corr, RL) < E(corr,NaCl) < E(corr, MEM) and J (MEM) << j(RL) congruent to j(NaCl) The stainless steel was characterized as non toxic in the cytotoxicity assay

Study of electrochemical behavior of azoles for AISI 430 stainless steel in H(2)SO(4) 1 mol L(-1)

Corrosion is an undesirable process that occurs in metallic materials. Studied was the effect of inhibiting Benzotriazole (BTAH), Benzimidazole (BZM) and Indole in different concentrations-for the stainless steel (SS) AISI 430 in H(2)SO(4) mol The techniques employed this research were: anodic potenciostatic polarisation, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy The curves of anodic polarisation showed that BTAH, BZM and Indol act as corrosion inhibitors for 430 SS, at concentrations of 1x10(-3) and 5x10(-4) mol L(-1) but do not inhibit corrosion for concentrations equal to or less than 1x10(-4) mol L(-1). The in-crease of the efficiency in relation to the inhibitory substances studied followed this order: Indol

The corrosion of austenitic 304 stainless steel in biodiesel

Fuel distribution uses 304 stainless steel containers for the storage of biofuels, however there are few reports in the literature about the corrosive aspects this. steel in biodiesel. The objective of this research is to study the corrosive behavior of 304 austenitic stainless steel in the presence of biodiesel, unwashed and washed, with aqueous solutions of citric, oxalic, acetic and ascorbic acids 0,01 mol L(-1), and compare with results obtained for the copper (ASTM D130). The employedtechniques were: atomic absorption spectrometry (AAS) and optical microscopy (OM). The results of EA A showed a low rate of corrosion for the stainless steel, the alloys elements studied were Cr, Ni and Fe, the highest rate was observed for the chrome, 1.78 ppm / day in biodiesel with or without washing. The OM of the 304 steel, when compared with that of copper has a low corrosion rate in the 304 steel/biodiesel system. Not with standing, this demonstrates that not only the 304 steel, but also the copper corrodes in biodiesel

Electrochemical behavior of the cistein and diphosfonate for stainless steel in media of HCl 1 mol L(-1)

Amino acids and self assembled monolayers (SAM`s) have been studied as to their inhibiting action on the corrosion of metallic materials. The objective of work is to study the electrochemical behavior of the cisteincisteine, the diphosfonate and the mixture of both in inhibiting the action of corrosion on stainless steel 304 in HCl 1 molL(-1). As the following techniques were used: open circuit potential (OCP), potenciostatic anodic polarization (A P), chronoamperomeny (CA), electrochemical impedance spectroscopy (EIS) and optical microscopy (OM). The results of CA showed that cisteine has a double effect, catalytic and inhibiting, in function of the immersion time of the metallic part in the electrolytic solution. AP curves have shown lesser current density for the system containing cisteine diphosfonate suggesting an inhibiting synergic action. These results have been confirmed by EIS and OM.

Variações em trajetórias de acumulação de capacidades tecnológicas em nível intra-empresarial: uma análise empírica da VALE S.A.

Esta tese relaciona-se ao tema da acumulação de capacidades tecnológicas em nível de empresa, suas fontes (mecanismos de aprendizagem) e suas implicações para a performance competitiva empresarial, em indústrias relacionadas a recursos naturais no contexto de economias emergentes. Durante os últimos 40 anos muito se avançou no campo da pesquisa sobre acumulação de capacidades tecnológicas em nível de empresas em economias emergentes. Porém, ainda há importantes lacunas a serem exploradas particularmente em relação a natureza e dinâmica de trajetórias de acumulação de capacidades tecnológicas intra-empresariais, no contexto de indústrias relacionadas a recursos naturais, especialmente na mineração. O objetivo da pesquisa aqui reportada é contribuir para minimizar esta lacuna. Particularmente, esta tese explora variações intra-empresariais de trajetórias de acumulação de capacidades tecnológicas, suas fontes (mecanismos subjacentes de aprendizagem) e algumas implicações que são geradas para a performance competitiva da empresa, no âmbito da indústria de mineração no Brasil, especificamente na empresa mineradora Vale, no período entre 1942 e 2015. Para alcançar este objetivo, a pesquisa apoia-se na combinação das literaturas de acumulação de capacidade tecnológica, inovação, aprendizagem e desenvolvimento industrial para a construção da base conceitual. Em paralelo, a pesquisa vale-se de um desenho de pesquisa qualitativo e indutivo baseado em evidências primárias com base em extensivos trabalhos de campo. Esse desenho de pesquisa é operacionalizado a partir de um estudo de caso individual em profundidade na Vale, no âmbito de três grandes áreas tecnológicas: prospecção e pesquisa mineral, lavra, e processamento mineral. Por meio da implementação dessa estratégia, a pesquisa encontrou: (1) Trajetórias de acumulação de capacidades tecnológicas relativamente distintas entre as três áreas de análise. Especificamente: (i) na área de prospecção e pesquisa mineral observou-se uma trajetória de seguidora tecnológica que alcança posição de liderança mundial em inovação e produção; (ii) na área de lavra também evidenciou-se uma trajetória de seguidora tecnológica que alcança posição de liderança mundial em inovação e produção, porém, com acumulação tardia de capacidades tecnológicas; e (iii) na área de processamento mineral houve o alcance precoce de posição de liderança mundial em inovação e produção a partir da criação de uma trajetória distinta da já mapeada pelos líderes globais. As trajetórias de acumulação de capacidades tecnológicas convergem para uma situação similar a partir de 2011 quando as três áreas apresentaram posição de liderança mundial em inovação e ao mesmo tempo demonstraram indícios de entrada em um processo de estagnação, que restringe as oportunidades de entrada em novas trajetórias tecnológicas e de entrada em novos negócios. (2) As variações encontradas nas trajetórias de acumulação de capacidades tecnológicas são explicadas pela maneira pela qual diferentes mecanismos subjacentes de aprendizagem foram combinados e utilizados pela empresa. Foram encontradas quatro combinações de mecanismos de aprendizagem que contribuíram para explicar as diferentes direções das trajetórias de acumulação de capacidades tecnológicas. (3) As variações nas três trajetórias de acumulação de capacidades tecnológicas geraram implicações distintas para a performance competitiva, mais especificamente em termos de performance inovadora, operacional/ambiental e de novos negócios. Os resultados da pesquisa geram contribuições para o entendimento do relacionamento intra-empresarial entre acumulação de capacidades tecnológicas e os mecanismos de aprendizagem subjacentes. E contribuem para o entendimento da mineração como uma indústria que oferece oportunidades para inovações significativas que, inclusive podem implicar na diversificação do tecido industrial nacional. Portanto, tal indústria deve receber atenção especial por parte de decisores de políticas públicas e de ações empresariais para evitar que empresas com alto potencial inovativo desconstruam suas capacidades inovadoras e consequentemente limitem seus impactos para o desenvolvimento tecnológico e econômico no contexto de economias emergentes.

DESIGN AND TEST OF A 7-T SPLIT-PAIR MAGNET FOR MAGNETIC SEPARATION

A 160 mm bore, 7 T split-pair magnet was constructed and tested aiming to mineral processing through HGMS (high gradient magnetic separation) or HCMS (helical channel magnetic separation.) This work describes the design and test results of the pair of coils operating under current in parallel mode. In the case of antiparallel current mode large repulsive force between coils is generated and a strong magnetic field gradient outside the magnet is created. A continuous magnetic separation system made with a helical channel magnetic separator for application in TiO2 processing is analysed.

Estudo de genes envolvidos no processo de adesão do Acidithiobacillus ferrooxidans em calcopirita (CuFe'S.IND.2')

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Bacterial and chemical leaching of chalcopyrite concentrates as affected by the redox potential and ferric/ferrous iron ratio at 22 degrees C

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Determination of heavy metals and genotoxicity of water from an artesian well in the city of Vazante- MG, Brazil

The city of Vazante-MG is of great socioeconomic and environmental interest because it is the most important zinc producer district of Brazil. The mineral processing and geochemical processes may determine high concentrations of heavy metals in water intended for human consumption. Thus, the present study aimed to quantify and evaluate the heavy metal genotoxicity of artesian water in the city by Atomic absorption spectrophotometer analysis and testing with the Allium cepa test, respectively. This study reveals a chemical contamination in well water in the city, caused by the presence of heavy metals. Therefore, it can be considered that the high levels of heavy metals found in water samples are correlated with the genotoxic events observed in root cells of A. cepa.

Tipo de cimentação em materiais duros do perfil de alteração da mina de fosfato da Anglo American, Catalão-GO

One of the main challenges in the mining sector at present, related to the optimization of mineral assets, consists in to find the best proportion of each geological material to be mined and homogenized to ensure high productivity and stability in ore processing plants. The stability of a mineral processing plant is factor for achieving operational excellence, as a stable performance of the plants ensures economy and adherence to financial planning businesses. Is already well Know that the feed rate of the processing plants is dependent on the hardness and quality of the ore. Therefore, the ore behavior predictability is the solution to ensure the stability of mineral processing plants. This work was developed in Anglo American Phosphate Brazil Ltda., at the Fazenda Chapadão Phosphate Mine, located in the southeastern portion of the state of Goiás, in the municipalities of Catalão and Ouvidor. The phosphate ore is the result of supergene apatite concentration in the weathering profile of the alkaline ultramafic phlogopitized rocks, intruded by foscoritic and carbonatitic rocks series. The weathering profile has about 100 meters thick and is divided into three basic types, from top to bottom, coinciding with decreasing intensity of weathering: oxidized ore, micaceous ore and weathered rock. In each portion of this weathering profile, mainly near the contacts between these three divisions, are hard materials, cemented by minerals such as apatite, quartz, goethite, monazite and barite. The different features presented by these materials makes to be vital the correct identification, quantification and location of different hard materials in the mine area, to maximize its use. The main objective of this study was to define the type of cementation of hard materials which predominates in each portion of the weathering profile in the mine, as well as their relationship with the protolith. The work involved geological mapping, channel sampling...

Dimensionamento de espessadores: validação experimental de três técnicas convencionais

This work reviews the fundamentals of three important techniques currently used to dimension thickeners: Flux of Solids, Talmadge-Fitch, and Roberts. They were applied to validate the calculation of diameter (D) and sedimentation area (A) of a real thickener, which clarifies brine in a plant located at Cubatao-SP. The calculation of thickener dimension (A and D) was based on the sedimentation behavior of salt particles in brine on a laboratory scale. The values of D and A (D=13,9-14,1m; A=151,7-156,1m(2)), which were calculated by the three techniques, were compared with the diameter of the real equipment (D=20,0m). On the other hand, corrected values of D and A (D=18,1-18,3m; A=257, 0-263, 0m(2)) were obtained by using a scale factor (f=1,3). These results are 10% lower than the real equipment.

Experimento para quantificar a eficiência de aspersão de líquidos: aplicação em distribuidores espinha de peixe

This paper describes a device developed on the pilot scale and a simple approach to compare liquid distributor efficiencies. The technique consists basically of analyzing the mass of the liquid collected in 21 vertical pipes measuring 52 mm in internal diameter and 800 mm in length placed in a quadratic arrangement and positioned below the distributor A 50 mm thick acrylic blanket that does not disperse liquids was placed between the distributor and the pipe bank to avoid splashes. Assays were carried out with ladder-type distributors equipped with 4 parallel pipes each for a column measuring 400 nun in diameter as an example of the application. The number (n) of orifices (95, 127, and 159 orifices/m(2)), orifice diameter (d) (2, 3, and 4 mm) and the flowrate (q) (1.2; 1.4; and 1.6 m(3)/h) were varied. The best spread efficiency, which presented the lowest standard deviation, was achieved with 159 orifices, 2 mm and 1.4 m(3)/h. The pressure (p) at the distributor inlet for this condition was only 51000 Pa (0.51 kgf/cm(2)), while the average velocity (v) was 6.3 m/s in each orifice. These results show some limitations of the practical rules used in distributor designs.

Indicadores-chave de desempenho e a gestão integrada da mineração

The exceptional advance of information technology and computer application to the mineral sector has allowed the automation of several processes of the mineral value chain. ERP systems (Enterprise Resource Planning) provided the platform for the efficient integration of all support activities of the mineral value chain. Despite all advances gathered with the application of computers, it was not possible to date, to effectively integrate the primary activities of the mineral value chain. The main reason for that are the uncertainties present in the productive process, which are intrinsic to the business, and the difficulty to quantify and qualify the benefits obtained with this integration due to the lack of a clear definition of the key performance indicators (KPIs). This work presents an analysis of the ERP systems application in Brazilian mining, identifies the KPIs of some of the most important Brazilian mining companies, and discusses the importance of mapping and measuring these indicators for the effective. management of the mining business.

TDEM survey in an area of seismicity induced by water wells in Parana sedimentary basin, Northern Sao Paulo State, Brazil

This article presents TDEM results from an area with recent induced shallow seismicity. The purpose was to do a geoelectrical mapping of sedimentary and fractured basaltic aquifers for better understanding of the hydrogeologic setting. The study area is in the Parana basin where flood basalts are overlain by sedimentary units near the city of Bebedouro, northern Sao Paulo State, Brazil. 86 TDEM soundings were acquired in an area of 90 km(2) in the Andes and Botafogo study areas. The soundings were chosen next to wells for calibration, and also along profiles crossing the seismically active areas. 1-D interpretation results showed the general geoelectrical stratigraphy of this part of the Parana basin. The upper geoelectrical layer is the shallow sedimentary aquifer (Adamantina formation) with less than 80 m thickness. The second geoelectrical layer contains the upper basalts of the Serra Geral formation at about 60-80 m depths. A saturated fractured basalt zone between 100 and 300 m depths was identifiable on various TDEM soundings. This depth range corresponds to the range of hypocentral depths for more than 3000 micro-earthquakes in this area. The lower basalt layer was estimated to lie between 400 and 650 m depth. The deepest geoelectrical layer detected by various TDEM soundings corresponds to the Botucatu sandstone (Guarani aquifer). Results suggest that the high-discharge wells are located in the fractured zone in the middle basalt of the Serra Geral formation. There is a good correlation between seismically active areas, high discharge wells (>190 m(3)/h), and fracture zones in the middle basalt. The results reinforce the hypothesis that the shallow seismic activity in the Bebedouro region is being triggered by high rates of groundwater withdrawal. (C) 2012 Elsevier B.V. All rights reserved.

Nonoriented Electrical Steels

The physical origins of the magnetic properties of nonoriented electrical steels; its relations to microstructural features like grain size, nonmetallic inclusions, dislocation density distribution, crystallographic texture, and residual stresses; and its processing by cold rolling and annealing are overviewed, using quantitative relations whenever available.