Estudio de los procesos de corrosion de una aleacion metalica de cobre usada en odontologia

Corrosion phenomena in a dental copper-based alloy are experimentally studied using electrochemical techniques. Two heating sources, torch and induction, were used in the casting experiments. In the corrosion essays, the optimum casting cycle and the polarization curves were obtained. It was found that the heating sources have little influence on the corrosion processes of the metallic alloys studied.

Borohidreto complexos de cobre (I) contendo difosfinas. Caracterização espectroscópica e comportamento térmico

Tetrahydroborate complexes of copper (I) with bidentate phosphines, [Cu(η 2-BH 4)(dppm)] (1), [Cu(η 2-BH 4)(dppe)] (2), [Cu(η 2-BH 4)(cis-dppet)] (3) and [Cu(η 2-BH 4)(dppb)] (4) (dppm = bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino) ethane; cis-dppet = 1,2-cis(diphenylphosphino)ethene; dppb = 1,4-bis(diphenylphosphino)butane) were prepared and characterized by elemental analysis, infrared spectroscopy, NMR and thermogravimetric analysis. The IR data for 1-4 showed bands typical of a bidentate coordination of BH 4 group to the copper atom and the 31P{ 1H} NMR spectra indicated that the phosphorous atoms are chelating the metal centre. The thermal behavior of the compounds was investigated and suggested that their thermal stability is influenced by the phosphines. Their thermal stability decreased as follows: [Cu(η 2-BH 4)(dppe)] (2) > [Cu(η 2-BH 4)(dppm)] (1) > [Cu(η 2-BH 4)(dppb)] (4) > [Cu(η 2-BH 4)(cis-dppet)] (3). According to thermal analysis and X-ray diffraction patterns all compounds decomposed giving Cu(BO 2) 2, CuO, CuO 2 and Cu as final products.

Alterações hematológicas e histopatológicas em pacu, Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes, Characidae), tratado com sulfato de cobre (CuSo4)

This paper evaluated the haematological and glycaemic parameters in Piaractus mesopotamicus (Osteichthyes, Characidae) infected with Monogenea Anacanthorus penilabiatus Boeger, Husak & Martins, 1995 (Dactylogyridae) after treatment with 0.50 mg/L and 1.00 mg/L of copper sulphate (CuSO4). The efficacy of the CuSO4 was observed in the first day after administration but not after eight, fifteen or thirty days. The histopathological analyses showed hyperplasia of the epithelium and circulatory changes in the gills. In the first day after treatment significant changes (P<0.05) in the total count of erythrocyte, leucocyte, mean corpuscular haemoglobin concentration (MCHC) were observed. The fishes treated with 0.50 mg/L showed decrease in the haemoglobin levels and in the percentage of neutrophils (P<0.05). The dose of 1.00 mg/L provoked increase of glycaemia but reduction in the lymphocytes percentage when compared with 0.50 mg/L in the 8th day. Fifteen days after 1.00 mg/L treatment, values of mean corpuscular volume (MCV) and special granulocitic cells (S.G.C.) percentage decreased. Nevertheless, increase of total leucocyte number was observed. Thirty days after treatment with 0.50 mg/L showed increased S.G.C. and treatment with 1.00 mg/L showed increased lymphocyte.

Desenvolvimento de um dispositivo para obtenção de monocristais de ligas à base de cobre

This paper describes the drawing, construction and optimization of a device, which can be used to obtain single crystals of different metallic materials with melting point from 550 to 1050°C. Components of ease obtaining and of low cost were used. The device was based on the modified Bridgman technique and it was used to obtain single crystals of copper-based alloys. The temperature axial profiles and a difference less then 1% in the temperature between the wall and the center of the ceramic tube in the critical region for obtaining single crystals of good quality indicated that the oven presents a good thermal stability. Single crystals of CuZnAl and CuAlAg alloys of good quality were growth and characterized using optical microscopy and Laüe X-ray back reflection.

Toxicidade aguda do sulfato de cobre e do extrato aquoso de folhas secas de nim para o caramujo (Pomacea canaliculata)

Snails can become an environmental and economic problem, causing substantial losses. The objective of this work was to estimate the acute toxicity of copper sulfate pentahydrate (CuSO4.5H2O) and the aqueous extract of dried neem leaves on snails (P. canaliculata) under laboratory conditions. In order to estimate the lethal concentration 50% (LC (I)50;96h), snails were exposed to six increasing copper sulfate concentrations (0.0; 0.01; 0.03; 0.05; 0.07 and 0.1 mg L-1) and six increasing concentrations of aqueous extract of dried neem leaves 0.0; 100; 125; 150; 175 and 200 mL aqueous extract of dried neem leaves L-1 water, equivalent to (0.0; 1.18; 1.47; 1.77; 2.06 and 2.36 mg azadirachtin L -1), in triplicate and one control treatment in an entirely random delineation. Estimated LC (I)50;96h, of copper sulfate was 0.02 mg copper sulfate L-1, with a 0.01 mg L-1 lower limit and a 0.03 mg L-1 upper limit. Estimated lethal concentration 50% of the aqueous extract of dried neem leaves was 142.75 mL L-1, equivalent to 1.68 mg L-1 of azadirachtine, with a 130.89 mL L-1 (1.54 mg L-1) low limit and 155.69 mL L-1 (1.83 mg L -1) as the upper limit.

El complejo de cobre de la Southern Perú

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Aplicação da metodologia de superfície de resposta na remediação de um solo arenoso contaminado artificialmente com cobre

Soil flushing is an alternative remediation technology for soils contaminated with heavy metals, which the main contaminant removing process consists in percolating an extraction solution. This work aimed to use the response surface methodology to point out combinations among the parameters of the extraction solution (Na2EDTA concentration, volume e pH) in order to reduce the concentration of copper in a sandy soil to risk levels lower than the intervention levels for exposure scenarios adopted by the Environmental Company of Sao Paulo State. Thus, a series of tests in leaching columns were carried out using a Fluvisol artificially contaminated (1257,3 mg kg-1). The tests were conducted in triplicate and setup a central composite rotatable design with 15 different parameters combinations of the extraction solution and one replicate in the center point. Using 5% significance level, the adjusted model (R2 = 0,98) indicated combinations of Na2EDTA concentration, pH and volume of the extraction solution which allow reduction of copper concentration below levels reported by environmental agency of Sao Paulo State for industrial, residential, agricultural or maximum exposure scenarios.

Una estrategia de desarrollo basada en recursos naturales: análisis 'cluster' del complejo de cobre de la Southern Perú

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Mapeamento de Paleosuperfícies associadas a identificação de depósitos supérgenos de cobre como ferramenta de exploração mineral na região de Itapeva e Ribeirão Branco- Vale do Ribeira, estado de São Paulo, Brasil

A few examples of supergene ore formation and their interaction with morphogenesis (palaeosurfaces) and weathering mineralogy are discussed. Geomorphological and mineralogical records to characterize palaeosurfaces associate the weathering of primary minerals and their relationship with concentrations of cooper and iron ore deposits in southeastern state of São Paulo, Brazil. We have distinguished two palaeosurfaces generated by several weathering phases and controlled by the geological framework. The first and oldest upper palaeosurfaces (900 - 1000 m a.s.l.), situated in Riberão Branco (Alto do Brancal), were developed on silico-limestones. It is formed by typical iron laterites enriched by secondary products of cooper. The second and younger level palaeosurfaces located in Itapeva (Santa Blandina and Bairro do Sambra). This palaeosurface is formed by copper percolating through the weathered rock (saprolite). Other features can be observed like neo-formed products in laterites. They are classified into two types: clay like silico- cupriferous products (with noticeable amounts of iron) and copper minerals (crysocolla, in their flat slopes). These features allowed the presence of copper ores and their morphogenesis control will help in the exploration and prospecting of supergene ore mineral.

Síndrome holandés, regalías mineras y políticas de gobierno para un país dependiente de recursos naturales: el cobre en Chile

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El impacto del programa de estabilización y las reformas estructurales sobre el desempeño ambiental de la minería de cobre en el Perú: 1990-1997

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El desarrollo de la minería del cobre en la segunda mitad del siglo XX

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Situación y tendencias recientes del mercado del cobre

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Determinantes del precio spot del cobre en las bolsas de metales

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Alimentação de leitões com dietas contendo soro de leite fermentado mais zinco e cobre orgânico

An experiment was carried out to evaluate the performance of piglets fed rations containing fermented milk and zinc and copper amino acid complex. Sixty four piglets, littermates, were used. The experimental design was based on random block with two dietary treatments. One of these contained a basal diet (DB) with ZnO e CuSO 4 and the other one with the DB, but without CuSO 4 and with the addition of fermented milk and zinc and copper amino acid complex (SLF Lact +ZnCuAA). There were eight replicate pens per treatment, and pigs were grouped at 4 per pen. The SLF Lact + ZnCuAA didn't not affect (p>0.05) final live weight of the piglets. However, live weight was different (p<0.01) between males and females (24.3 vs. 24.0 kg) at end of experiment. The feed intake of animals feed with SLF Lact+ZnCuAA was higher (p<0.01) in 8% in the first 14 days (0.261 vs. 0.239 kg/d), 15% from 15 to 28 days (0.756 vs. 0.675 kg/ d) and 12% from 29 to 42 days (1.091 vs. 0.962 kg/ d) compared to control group. Daily average feed intake in the experimental period was 11% higher (p<0.01) for the animals fed with the diet contained SLF Lact+ZnCuAA. Weight gain of the treatment with SLFL act+ZnCuAA was higher (p<0.01) by 14% from 0 to 14 days (0.176 vs. 0.152 kg/d), 11% from 15 to 28 days (0.564 vs. 0.500 kg/d) and 12% from 29 to 42 days (0,572 vs. 0,501 kg/d). Average daily weight gain of 42 days of trial of treatment with SLF Lact +ZnCuAA was 12% higher (p<0.01) compared to control group (0.437 vs. 0.384 kg/d). Feed conversion ratio was 8% lower (p<0.01) for treatment with SLF Lact+ZnCuAA in the first 14 days (1.487 vs. 1.614). Supplementation with fermented milk and zinc and copper amino acid complex in diets containing zinc oxide improved growth performance of weanling piglets.