The search for alternatives that minimize the generation of tailings and enable their reuse, leads to characterization studies with the objective of a better understanding of the physical, chemical and mineralogical properties of iron ore tailings. The increase in demand for high-quality ore overlapping ore extraction with increasingly lower iron concentration levels, is part of the challenge of mineral exploitation. In view of the aforementioned needs, a more detailed characterization of the tailings contributes to the improvement of the mineral processing stage and the reuse of the generated tailings. To this end, an analysis of the characteristics of the tailings was carried out through physical, chemical and mineralogical characterization, with emphasis on quantitative electron microscopy - QEM. The tests revealed that the predominant phases are hematite and quartz and, to a lesser extent, goethite, gibbsite and kaolinite. As for the degree of release, hematite/magnetite has 88.13% of its particles totally free, 0.53% associated with quartz and 6.77% associated with goethite. The chemical composition is 32.29% Fe, 47.92% SiO2, 2.76% Al2O3, and 2.14% PPI. In this scenario, mineralogical characterization, as a main component of geometallurgy, makes it possible to propose alternatives that improve the ore beneficiation process and the reuse of tailings.

Abstract: The study characterizes dental implant surfaces treated with phosphoric acid to assess the effects of acid treatment on blood cells and correlate them with cytokine levels. The implant surfaces examined were divided into untreated metal surface (US; n = 50), metal surface treated with phosphoric acid (ATS; n = 50) and cement surface (CS; n = 50) groups. The samples were characterized by scanning electron microscopy (SEM) and rheometry. The implants were incubated with human blood mononuclear cells for 24 h, with surface rinsing in the ATS treatment. Cell viability was determined by colorimetric methods and cytokines in the culture supernatant were quantified using flow cytometry. In the ATS group, the surface porosity and contact surface were increased and plaques were observed on the surface. The blood flow and viscosity curves were similar among the treatments, and the high cell viability rates indicate the biocompatibility of the materials used. An increase in the levels of IL-2, IL-4, IL-6, IL-10 and TNF-α was observed in the ATS and CS groups. There were positive correlations between IL-10 and IL-2 levels and between IL-10 and IL-4 levels in the culture supernatant of the ATS group. The results suggest that implant surface treatment with phosphoric acid activates the production of inflammatory cytokines. The increased cytokine levels can modulate the immune response, thereby improving biofunctional processes and promoting the success of dental implants.

The characterization of materials is an area of extreme importance for engineering, it uses a range of instrumental techniques to provide an information bank for material analysis and selection. In the treatment of iron ore the mineralogical characterization is done, almost exclusively, by optical microscopy. However, materials with very fine granulometry, below 4 µm, make their preparation and visualization restricted in this equipment. The present work aims to identify the minerals Hematite, Magnetite and Goethite in samples of tailings from the iron ore processing, employing a Bartington MS3 that evaluates the magnetic susceptibility as a function of the temperature. These measurements make it possible to identify Curie temperatures characteristic of Magnetite (580 °C) and Hematite (675 °C), as well as Goethite's Neel temperature (120 °C). The results showed that the application of the technique is of great value for the identification of the magnetic bearing minerals and the quantification of the magnetic potential of the sample.

O Produto Granulado de Morro da Mina é um minério de manganês silicatado carbonatado que apresenta grande potencial econômico para as empresas de ferro ligas instaladas em Minas Gerais. Entretanto o baixo teor de manganês e o pouco conhecimento a respeito de suas propriedades metalúrgicas dificultam a sua aplicação. Esse trabalho, pioneiramente, propõe um estudo a respeito da degradação granulométrica das suas partículas a frio e a quente. Uma tonelada do material foi recebida, homogeneizada e quarteada. Amostras representativas foram caracterizadas pelas técnicas de ICP-AES, DRX, MEV-EDS, BET e MO. Foram propostos três parâmetros para a caracterização da degradação: índice de desintegração granulométrica a frio (DGF), o índice de crepitação (IC) e o índice de desintegração granulométrica a quente (DGQ). Por meio deles, foi possível observar que o Granulado de Morro da Mina não apresenta significativa degradação granulométrica por crepitação, entretanto apresenta uma intensa degradação após ser submetido a ciclos térmicos de calcinação e de pré-redução, não existindo significativas diferenças entre os dois. A decomposição térmica dos carbonatos de manganês e o consequente aumento da porosidade são os principais fatores responsáveis pela desintegração do minério.

The manganese lump ore from Morro da Mina mine is typically silicate carbonated and presents a great economic potential for the ferroalloy companies installed in Minas Gerais. However, its low manganese content, associated with the lack of knowledge about its metallurgical properties makes it difficult for large scale application. This pioneering study aimed to amply investigate this lump ore's particle disintegration. One ton of ore from the mine was homogenized and quartered. Representative samples were characterized by different techniques, such as ICP-AES, XRD, SEM, BET and OM. Aiming to characterize particle disintegration, three parameters were proposed: Cold Disintegration Index (CDI), Decrepitation Index (DI) and Heating Disintegration Index (HDI). By using these indexes, it was possible to conclude that this manganese lump ore did not present significant disintegration at room temperature. At medium temperature test, slight decrepitation occurred, and at high temperatures, intense disintegration was detected. The carbonate decomposition and porosity growth were the main responsible factors for the ore hot particle disintegration.

Foi estudada por dilatometria a variação das temperaturas críticas para a formação de austenita, com o aumento da velocidade de aquecimento. A análise foi realizada a velocidades de aquecimento entre 10 e 90ºC/s. Foram propostas equações empíricas para o cálculo de Ac3, em função da velocidade de aquecimento. O aumento da velocidade de aquecimento não afetou Ac1, mas Ac3 aumentou em 115ºC. As equações propostas se revelaram de uso mais geral, uma vez que também previram os resultados obtidos em trabalhos para outros aços com altos coeficientes de correlação.

The variation in critical temperatures for the formation of austenite when increasing the heating rate was studied by dilatometry. The analysis was performed at heating rates between 10 and 90ºC/s. Empirical equations are herein proposed for calculating Ac3 with respect to the heating rate. The results showed that an increase in the heating rate had no influence on Ac1, but Ac3 increased 115ºC. The equations proved to be of a more general use, as they also predicted the results of works on other steels with high values of correlation coefficients.

Visando a melhorias no beneficiamento e no processo de fabricação de ferroligas de manganês, foi realizada a caracterização de uma tipologia predominante de minério de manganês, de ocorrência na região de Carajás, PA, BR. Obteve-se uma amostra representativa da tipologia e foram realizadas análise granulométrica por peneiramento e análise química, por ICP-AES. Foram identificadas por difratometria de raios X as fases minerais majoritárias. Um estudo termogravimétrico foi desenvolvido para verificar a estabilidade térmica, ao ar, das fases minerais majoritárias. Observou-se que 19,3% da amostra encontram-se abaixo de 6,3mm. O teor de manganês no minério foi de 52,63% em peso, com 1,92% de sílica, 0,17% de fósforo e 3,13% de ferro. Foram identificados, na amostra, os óxidos de manganês criptomelana, todorokita e pirolusita, com goethita, quartzo, gibbisita e caolinita compondo a ganga. Para a amostra estudada, observou-se a decomposição térmica dos óxidos criptomelana e pirolusita, em torno de 600ºC, ao ar. Em torno de 950ºC, teve início a transformação de Mn2O3 em Mn3O4.

In order to improve manganese-iron alloy production processes, an important Brazilian manganese ore typology, placed in Carajás, PA, was characterized. A representative sample was obtained from mine. The particle size determination was performed by screening, followed by chemical analysis using plasma spectrometry (ICP-AES). The physical properties studied included density, surface area and porosity measurements (BET). The mineral constituents was identified and quantified by X-ray diffraction. A termogravimetrical study was done in order to verify the thermal stability of major mineral constituents in the air. It was observed that 19.3% of studied typology was below 6.3mm. The manganese, silica and phosphorus contents were 52.63%, 1.92% and 0.17%, respectively. The oxides identified were cryptomelane, todorokite and pyrolusite. The other constituents were goethite, quartz, gibbsite, and kaolinite. According to the thermal study, the cryptomelane and pyrolusite start their decomposition in the air, at approximately 600ºC. At around 950ºC, Mn2O3 decomposition and Mn3O4 growth were observed.

The influence of processing parameters (slab thickness, water flow of interstand cooling and oil flow in roll gap lubrication system) on the thickness and composition of the tertiary scale formed during hot strip rolling, was studied in a low carbon steel in factory. The scale formed on the rolled surface was characterized by scanning electron microscopy and Mössbauer spectroscopy. It was observed that the combined effect of a greater rolling oil volume applied, larger bar thickness, and smaller amount of water flow during interstand cooling reduces the tertiary scale thickness. Besides, a smaller crack density in the samples is associated with greater rolling oil volume and smaller oxide scale thickness. The principal phase of the scale formed in hot-rolled steel strips is stoichiometric magnetite, without isomorphic substitutions.

Crushing residues of FeSiMn and high-carbon (HC) FeMn alloys were characterized in order to evaluate their recycling possibility. Particle size determination was performed by screening, followed by chemical analysis of each particle size range using plasma spectrometry (ICP-AES). The slag content was identified and quantified by optical microscopy. All of the fines with grain sizes above 1.18 mm presented alloy contents in excess of 99 wt. (%) and were determined to need no further concentration prior to recycling. However the contents of Mn, Fe, Si and P in the fraction below 1.18 mm did not meet the chemical specifications for commercial manganese alloys, except for phosphorous. Optical microscopy of the fraction below 1.18 mm, showed that 87.95% of the FeSiMn corresponded to the alloy and that the slag content was 12.05%. For the HC-FeMn sample, 95.07% corresponded to the alloy and only 4.93% to the slag. These results revealed potential for gravity concentration and recycling, reducing the residues in about 95% and improving the process productivity.

Pós de titanato de bário foram produzidos por síntese hidrotérmica, a 220°C, por 20h, na forma estequiométrica pura e dopada com concentrações de lantânio entre 0,2 e 1,0mol%. Os pós foram caracterizados por difração de raios X e, em seguida, prensados a 3000kgf, na forma de pastilhas. As pastilhas foram sinterizadas ao ar a 1250ºC por 5h e caracterizadas por difração de raios X, microscopia eletrônica de varredura e impedanciometria complexa

Barium titanate powders were produced by hydrothermal synthesis, at 220ºC, for 20 hours, in stoichiometric composition and doped with lantanum varying from 0.2 to 1.0mol%.The powders were characterized by x-ray diffraction and then pressed at 3,000 kgf to form discs. The discs were sinterized on air at 1250ºC for 5 hours and characterized by x-ray diffraction, scanning electron microscopy and complex impedanciometry

Estudou-se o efeito da rápida austenitização sobre as propriedades mecânicas de um aço SAE 1045, na condição de temperado e revenido a 600ºC. A microestrutura das amostras austenitizadas a 900 e 950ºC e temperadas imediatamente ao atingir essas temperaturas, têm a microestrutura constituída de martensita refinada, com pequena fração volumétrica de ferrita poligonal e ferrita acicular. Os valores dos limites de resistência e escoamento das amostras revenidas são fortemente dependentes do tempo de encharque. As transformações fases no revenimento têm efeitos similares sobre os limites de resistência e escoamento das amostras revenidas. Tais amostras têm altos valores da razão de escoamento (valor médio de 0,91). Os valores do produto do limite de resistência pelo alongamento percentual variaram de 32589MPa.% a 24150MPa.%. A otimização das propriedades mecânicas do aço SAE1045, com alta resistência mecânica e boa ductilidade, foi obtida com austenitização a 900ºC, têmpera imediatamente após atingir essa temperatura e revenimento a 600ºC por 100s.

This work studied the effect of fast austenitization on the mechanical properties of SAE1045 steel, as quenched and tempered. The samples austenitized at 900 and 950ºC, and immediately quenched after reaching these temperatures, showed microstructures of refined martensite, with small volume fractions of polygonal and acicular ferrites. The values of the tensile and yield strengths of the tempered samples are strongly dependent on the soaking time. The phase transformations during the tempering have similar effects on the tensile and yield strengths of the tempered samples. These samples have high yield ratio values (average of 0.91). The values of the product of the tensile strength for the percent elongation varied from 32589MPa% to 24150MPa%. The optimization of the mechanical properties of the SAE1045 steel, with high strength and ductility, was achieved for the austenitization at 900ºC, immediately quenched after reaching that temperature, and tempering at 600ºC for 100s.

Esse trabalho descreve o tratamento térmico por indução eletromagnética em tubos sem costura para a produção de hastes para sondagem geológica. São determinados, através de análises metalográficas e ensaios mecânicos, os parâmetros ideais para as etapas de têmpera e revenido, a fim de obter hastes nacionais tratadas com qualidade similar às disponíveis no mercado internacional. A determinação dos parâmetros operacionais do equipamento de indução eletromagnética, para têmpera e revenimento de tubos de aço SAE-1045, utilizados na confecção das hastes, permitiu obter um perfil de dureza sem grandes flutuações de valor, variando suavemente de um valor máximo próximo a 45HRc na extremidade externa da faixa tratada, para um valor mínimo próximo a 35HRc, no final da mesma.

This work describes the production of geological drill rods through electromagnetic induction thermal treatment of tubes. The research aims at determining, through metalography, mechanical tests and field tests, the ideal induction hardening and tempering parameters, to produce drill rods with qualities similar to the ones available in the international market. The determination of the induction hardening and tempering parameters of SAE-1045 steel tubes, for the production of geological drill rods, was capable of producing hardness profiles with low fluctuations in values, ranging from a maximum value of 45HRc close to the extremity, to minimum values close to 35HRc at the end of the treated region.

As propriedades do cimento Portland estão diretamente relacionadas às concentrações de suas fases constituintes, principalmente a alita, a belita, a fase ferrítica e o aluminato. A alita, de composição 3CaO.SiO2 e abreviada por C3S, deve ser o constituinte majoritário do clínquer após o processamento, pois é sua reação de hidratação que confere a resistência mecânica ao cimento curado. A belita, de composição 2CaO.SiO2 e abreviada por C2S, está presente como o primeiro complexo de cal e sílica formado no aquecimento e, sendo mais estável a baixas temperaturas que o C3S, volta a se formar no resfriamento. O aluminato está presente principalmente na forma de 3CaO.Al2O3, abreviado por C3A, enquanto a ferrita aparece como constituinte principalmente na forma 4CaO.Al2O3.Fe2O 3, abreviada por C4AF. Os teores de ferrita e alumina, no entanto, alteram a estabilidade da alita, com conseqüentes alterações na reatividade do cimento. O presente trabalho estuda os efeitos de adições de Fe2O3 e Al2O3 sobre a estabilidade da alita e apresenta diagramas CCT para a decomposição da alita na presença desses compostos.

The properties of Portland cement are directly related to the concentrations of its major phases, i.e., alite, belite, the ferritic phase and the aluminate phase. Alite, with the composition 3CaO.SiO2, known as C3S, should be the major component of the clinker after processing, once its hydration produces the high yield strengths of cured cement. Belite, with the composition 2CaO.SiO2, known as C2S, is the first lime and silica complex, formed during the heating process. It presents higher stability at low temperatures than C3S, so that it tends to be formed again during the cooling cycle, from the decomposition of alite. The aluminate phase appears mainly with the composition 3CaO.Al2O3, known as C3A, and the ferritic phase appears with the composition 4CaO.Al2O3.Fe2O 3, known as C4AF. However, the ferrite and alumina contents affect the alite stability, and consequently, its reactivity. This paper studies the effects of Fe2O3 and Al2O3 additions over the alite stability and presents CCT diagrams for the alite decomposition in the presence of these compounds.

As propriedades mecânicas do cimento Portland estão intrinsecamente relacionadas à composição química do clínquer, em especial à concentração de silicato tricálcico 3CaO.SiO2, ou C3S. No processo produtivo industrial, o clínquer deve ser resfriado rapidamente, para evitar a decomposição do silicato tricálcico em silicato dicálcico e cal. Esse trabalho estuda a cinética de decomposição térmica do C3S puro. A decomposição do C3S puro em resfriamento contínuo apresentou uma velocidade mais elevada do que a tradicionalmente aceita na literatura.

The mechanical properties of Portland cement are closely related to the chemical composition of the clinker, and particularly to the concentration of tricalcium silicate, 3CaO.SiO2, or C3S. In the industrial production process, the clinker must be rapidly quenched, to avoid its decomposition into dicalcium silicate and lime. This work studies the kinetics of thermal decomposition of pure C3S. The continuous cooling transformation of pure C3S showed a decomposition rate higher than the values traditionally accepted in the literature.

The properties of a microalloyed steel, with Nb and V in its composition, were studied, after different intercritical thermal treatments and at different austenitizing and tempering temperatures. The mechanical properties of the specimens were measured in a Vickers hardness tester, and their microstructures were analyzed by optical microscopy, with the aid of a digital image processor. After austenitizing at 1100 °C and tempering at 625 °C, the samples showed significantly higher tempering resistance, reflected by their retention of high hardness, which may be associated with a secondary hardening precipitation of Nb carbon nitrides. In the sample with dual-phase microstructure, the martensite volume fraction varied from 18.2 to 26.3% and the ferrite grain size remained unchanged, upon the variation of the time length of the intercritical treatments. Tempered samples showed Vickers hardness (HVN) varying from 327 to 399, and dual-phase samples showed HVN from 362 to 429.