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Excessive carbon dioxide (CO2) environmental emission can be partially solved using carbon geological storage technologies. Up-to-date materials in CO2 injection wells are strongly susceptible to acidic attacks causing their irreversible damage over a long time scale. This study investigates degradation by CO2 of epoxy resin-cement paste composites at elevated pressure (50 bar) and temperature (70°C) to mimic wellbore conditions. The effect of epoxy resins on cement carbonation was evaluated by phenolphthalein test, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and numerical simulations. According to electronic-structure-based molecular dynamics simulations, the epoxy resin forms a separate phase that blocks potential reaction sites between the cement and CO2. Thanks to CO2-phobic behavior, the resin repels CO2 and minimizes cement damage due to degradation process. The optimal content of epoxy resin in the cement paste was up to 30% w/w. The reported results provide clear guidelines for further evolution of reinforced cements for use in CO2 injection wellbores. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

The mixtures of aqueous amines and ionic liquids (ILs) are considered as potential solvents for CO2 capture. We report corrosion and CO2 absorption behavior of the mixed IL–amine solutions. The absorption tests were performed at 318.15 K under 0.1–2.7 MPa. The corrosion tests were carried out at 318.15 K under 2.7 MPa. Addition of [bmim][BF4] in aqueous alkanolamine solutions reduces corrosion rate for MEA by up to 72%. The CO2 absorption capacity in the mixtures falls between those of aqueous MDEA and pure IL. These results allow to choose the working pressure range as a function of other parameters, such as gas pressure and mixture viscosity. According to the simulations, [bmim][BF4] participates in the gas capture through H-bonding, although the number of amine molecules is enough to capture all supplied CO2 molecules. The equilibrium of the chemisorption reaction is, therefore, modified upon the stepwise IL addition. An ideal IL content for preventing corrosion is 10% w/w.

The performance of SAE 1010, API K55 and API N80 steels were evaluated in terms of resistance to corrosion with the use of two CO2-saturated saline solutions (NaCl and CaCl2, both at the concentration of 0.5 M) and wet supercritical CO2 at a temperature of 90°C under 15 MPa for 07 days. Mass loss tests were performed to determine corrosion rates and the films of corrosion product evaluated by scanning electron microscopy and potentiodynamic polarization technique. Lower corrosion rates were obtained in a wet supercritical CO2 medium. The degree of protection offered by corrosion products films depended not only on the steel but also on the corrosive medium and kind of salt present.

The aim of this study was to evaluate the chemical resistance and mechanical properties of cement class G with n-SiO2 addition after being exposed to CO2-saturated water at HPHT, simulating geological carbon storage condition. Four different amounts of n-SiO2 (0.5, 1, 1.5 and 3 wt%) and a standard cement (STD Cement) were tested with CO2-saturated water at 150 bar and 90 °C for 7 and 56 days. The workability of the slurries was evaluated by mini slump test and helium gas pycnometry was used to measure the specific density of unreacted hardened cement systems. Zones affected by CO2 reactions (bicarbonated, carbonated and portlandite depleted zones) and unreacted core were analyzed using optical and scanning electron microscopes, energy dispersive spectroscopy by line scan, X-ray microtomography and atomic force microscopy. Vickers microhardness and uniaxial compressive strength were used to obtain information about alteration in mechanical properties. The results showed that the addition of n-SiO2 reduced the workability of the slurries and had insignificant influence on specific density of the hardened cement. After 7 days of exposure to CO2 medium, the 1.5% n-SiO2 was the most effective cement system to reduce CO2 degradation, decreasing the chemical altered thickness to 2.63 mm when compared to STD Cement (3.06 mm). Results from 56 days of exposure to CO2 show that only 0.5% n-SiO2 cement system is similar in terms of carbonation to STD Cement. For other n-SiO2 amounts (1%, 1.5% and 3%) the thicknesses of chemically altered layer are bigger than STD Cement. However, changes in chemical composition, microstructure and density from periphery to the core of the cement system were less accentuated in the cement systems with n-SiO2 addition after 56 days of cement systems exposure to CO2. Furthermore, the n-SiO2 cement systems presented a lower loss in compressive strength values when compared to STD Cement after reaction with CO2.

From our work, significant progress has been made in understanding the degradation of cement-casing systems. The CO2 degradation process was evaluated in specimens with a large interfacial defect, such as large annular spaces, voids and/or channels, which may be the result of a poor cementing job. From the experiments showing no interfacial defect, no signs of degradation were observed, while from experiments showing interfacial defect, both the cement and steel undergo significant degradation. In the well casing, the CO2-rich brine affects the steel phase, leaching Fe2+ ions into solution and promoting FeCO3 precipitation on the material surface, while on the cement sheath, two processes are occurring: (i) the portlandite dissolution and (ii) the cement carbonation process. Then, iron (Fe2+) starts to migrate into the cement structure, compromising the material’s self-healing and pore-blocking features, while calcium (Ca2+) starts to compose the corrosion film from the formation of mixed carbonates (FexCayCO3) so reducing the corrosion layer’s protection. Finally, both ions (Ca2+ and Fe2+) become so abundant in the material vicinity that they may form calcium carbonate (CaCO3) on the corrosion layer and iron carbonate (FeCO3) in the cement matrix. Thus, from our results, the degradation mechanisms of the cement-casing system in CO2-rich brine was revised.

The performance of cement class G used in cementation of oilfield wellbores with addition of pozzolans was evaluated under geological carbon storage conditions. Two commercial synthetic zeolites types (4A-1 and 4A-2) and fly ash from a coal-fired plant were used as pozzolanic materials in amounts of 5 and 10% in weight replacing the cement. After curing, the cement samples were submitted to degradation tests in CO2-saturated water at 15 MPa and 90 °C for 7 and 14 days. The cement chemical degradation by CO2 was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and compressive strength tests. The chemically altered layer thickness was averaged 3.46 mm for standard cement after 14 days of exposure to CO2. On the other hand, cement systems with 10% wt. of pozzolanic material varied from 1.70 to 5.50 mm depending on the type of pozzolan and level of cementitious matrix porosity related to pozzolanic particle clustering. In general, 4A-1 zeolite presented better performance in terms of resistance to CO2 attack and higher compressive strength after 14 days when compared to 4A-2 zeolite. The results showed that the addition of fly ash improved the compressive strength of the samples but increased the chemically altered layer due to CO2 diffusion. SEM and XRD analyses showed that the portlandite was consumed and carbonation occurred in the chemical modified layer due to cement reaction with aqueous CO2. Most cement systems with and without pozzolanic material exhibited no expressive loss on compressive strength after being exposed to CO2-rich environment up to 14 days. On the contrary, some cement systems with 4-A1 zeolite and fly ash exhibited a mechanical resistance increase due to the carbonation process.

The CaCO3 influence on the corrosion properties of low carbon steel in aqueous solutions saturated with CO2 and NaCl at 80 °C and 15 MPa was investigated over time with respect to morphology, thickness, structure, chemical composition and corrosion rate. The corrosion product formed in CaCO3-based solution was a calcium-enriched siderite and the scales were thinner and more porous than the ones formed in solutions without CaCO3. The CaCO3 reduced the corrosion rate, but the scales produced in the presence of this compound presented depassivation followed by formation of pits during electrochemical measurements effectuated on corroded samples.

The aim of this work was to analyze the effect of biodiesel and diesel–biodiesel blends on the sliding wear behavior of AISI 440B martensitic stainless steel. Lubricated tests were performed on AISI 440B martensitic stainless steel samples using Brazilian commercial diesel (containing 7 vol.% biodiesel), pure biodiesel, and diesel–biodiesel blends with biodiesel additions of 20% v/v, 30% v/v, and 50% v/v. Non-lubricated tests were also performed. The stainless steel was analyzed in the as-received condition (annealed) and after heat treatments (quenched and tempered at different temperatures), using a pin-on-disk device with an alumina pin, at a 1.8 m/s sliding speed, 14.7 N load, and 4400 m sliding distance, following the ASTM G99-04 Standard. Wear track widths, wear coefficients, and wear track surfaces were analyzed by optical and scanning electron microscopy. The results showed that AISI 440B presented the worst wear behavior in the dry condition with a microstructure characterized by a ferritic matrix and dispersed carbides (annealed condition). The wear resistance increased with the increase in biodiesel content due to the matrix strengthening by the martensitic transformation (heat-treated condition). When the biodiesel content was superior to 50% v/v, a reverse result was found. The observed wear mechanism was abrasive in all conditions. A − 1.35 power law coefficient characterized the wear coefficient as a function of biodiesel content for the annealed condition and a − 0.95 power law coefficient for the heat-treated conditions.

Neste trabalho estuda-se a influência da adição de cobre e de tratamento térmico na microestrutura da liga Zamac 8 comercial (ZnAl4Cu2,6Mg0,5). Para tal, duas ligas foram fundidas, a liga zamac 8 e a liga zamac 8 com adição de 8% em peso de cobre, sendo que a solidificação foi acompanhada por análise térmica. O tratamento térmico foi realizado em duas condições: a 150 C 143 h e a 300 C por 94 h. A caracterização das ligas antes e após a realização do tratamento térmico foram realizadas por microscopia eletrônica de varredura e mapeamento por EDS (Energy Dispersive X-Ray Spectroscopy) e por medidas de dureza Brinell. A adição de cobre levou a um aumento no intervalo de solidificação da liga Zamac 8 comercial e alterou o tempo da formação de cada fase/microconstituinte, levando à variação entre as quantidades relativas de cada fase ou microconstituinte. Os tratamentos térmicos alteraram a microestrutura, tanto da liga comercial quanto da liga modificada pela adição de cobre. Para a liga Zamac 8 comercial o tratamento térmico realizado a 300 C por 94 h foi o que promoveu a diminuição partículas da fase presentes nas dendritas da fase, enquanto que para a liga Zamac 8 com adição de Cobre foi o tratamento térmico realizado a 150 C por 143 h. No entanto, o mapeamento por EDS mostra que há cobre em maior concentração na fase primária independente da temperatura e tempo de tratamento térmico, indicando que pode ter havido transformação da fase metaestável na fase estável , que também contém cobre. Não foi verificado alteração significativa na dureza do material após tratamento térmico, exceto na liga comercial Zamac 8 tratada termicamente a 150 C por 94 horas, esta alteração pode ser explicada pela microestrutura, onde o percentual da estrutura eutética presente é baixo.

The Organic Devices Optically Transparent (ODOTs) are the base Polyaniline (PANI) and were electrodeposited on substrates of the materials optically transparent covered with ITO and characterized by UV-Visible Spectroscopy (UV-Vis), Electrical Measurements (EM) and Scanning Electron Microscopy (SEM). The deposition of the PANI films was prepared in perchloric acid solution and identified by PANIX1. The results obtained by UV-Vis shows that the PANI-X1 does not have displacement of optical absorption for wavelengths greaters. The EM of PANI-X1 have stability after electrodeposition, because the thickness of the sample is equivalent conductive layer. After 466 hours of electrical tests, there was the appearance of nanoparticles visible for images by SEM due to the migration process of Organic Semiconductor Materials (OSM). Similar to the phenomenon of electromigration observed in connections and interconnections of microelectronic devices, the results reveal a new mechanism of migration that arises with the passage of electric current in ODOT.

Consolidação por Constrição Radial (CCR) é uma técnica de metalurgia do pó que possibilita a obtenção de peças metálicas próximas da forma final, com alta densidade e de formas complexas, com custos de produção mais baixos que as tecnologias convencionais. CCR assemelha-se, em alguns aspectos, ao processo de compactação isostática a quente, sendo que as principais diferenças referem-se ao fato de que o processo CCR utiliza moldes cerâmicos fabricados a partir do processo de microfusão e usa um meio compressor secundário na forma de pó, ambos confinados em um container metálico. Nesse trabalho, desenvolveu-se um sistema experimental de CCR, visando à produção de pré-formas de ferro de alta densidade. Como meio compressor secundário, foi utilizado pó de argila calcinada. As pré-formas produzidas foram caracterizadas quanto à densidade, microestrutura e dureza. Observou-se que a configuração do container metálico/meio compressor secundário/molde cerâmico tem grande influência nas características de densidade e dimensionais das pré-formas. As pré-formas obtidas apresentaram consolidação satisfatória do pó como indicado pela microestrutura apresentada, alta densidade, elevada dureza, pouca formação de óxido e uma correlação direta entre os valores de dureza e densidade. The Radial Constriction Consolidation (RCC) process can be considered a powder metallurgical technique that allows for the fabrication of components with complex geometries, near-net-shape and full density at low production costs when compared to the traditional process. In some aspects, the RCC process is similar to the hot isostatic pressing process, but it uses a ceramic mold confectioned by investment casting and a powder as a secondary pressing media, all of which are confined in a metallic container. In this paper, a RCC experimental system was developed aiming to produce iron billets with the characteristics of near-net-shape and high density. Clay powder was used as a secondary pressing media. The obtained billets were characterized in terms of density, microstructure and hardness. It was observed that the configuration of the metallic container/ secondary pressing media/ceramic mold has an important influence on the characteristic of density and near-netshape of the billets. The billets presented satisfactory powder consolidation as shown in their microstructure, high density, elevated hardness, little oxide formation and a direct correlation between the values of density and hardness.

In this paper the influence of copper and magnesium content in the microstructural evolution during the solidification of Zn–4 wt.% Al hypoeutectic alloys was investigated using the CA-CCA method (Computer-Aided Cooling Curve Analysis) and SEM (Scanning Electron Microscopy). The identification of chemical composition of the phases and microconstituents was done by SEM using the EDS (Energy Dispersive X-Ray Spectroscopy) operation mode. For that purpose, ternary and quaternary alloys were prepared with different amounts of copper and magnesium. The influence of both copper and magnesium amounts on the transformation temperatures of the Zn–Al based hypoeutectic alloys was evident in the distinct microstructures formed during solidification as well as in the cooling curves obtained by thermal analyses, promoting modifications in solid–liquid temperature range, in the kinetic and also in the chemical compositions of the phase transformation. The addition of extra copper promoted the formation of significant quantities of the copper-rich phase (CuZn 4 precipitate) in the interdendritic region, while the addition of extra magnesium promoted the formation of the magnesium-rich phase and changed not only the morphology of the primary dendrites but also its relative content. Besides, an increase in the relative primary eutectic structure and a decrease in the quantity of the lamellae eutectoid structure were observed. Additionally, the secondary lamellar eutectic became more refined in the presence of higher magnesium content. All the cooling curves are in agreement with the observed microstructure. Both elements, copper and magnesium, also promoted an increase in the hardness of the Zn–4Al hypoeutectic alloys due to the formation of CuZn 4 phase and to the secondary lamellae eutectic refinement, respectively.

We show the results of some test beams performed on a new monolithic strip silicon detector telescope developed in collaboration with the INFN and ST-microelectronics. Using an appropriate design, the induction on the ΔE stages, generated by the charge released in the E stage, was used to obtain the position of the detected particle. The position measurement, together with the low threshold for particle charge identification, allows the new detector to be used for a large variety of applications due to its sensitivity of only a few microns measured in both directions.

III–V ternary alloys semiconductor materials, in particular Ga1−xInxSb, are ideal candidates for device substrates because of the possibility to define the lattice constant as a function of the third element, indium. Aluminum, an isoelectric dopant for Ga and In, increases the carrier mobility in GaSb crystals and has influence over the concentration of native defects by passivating and/or compensating them. To understand the influence of Al on the distribution of indium in ternary alloys of Ga0.8In0.2Sb, pure and doped ingots were obtained with approximately 1020 atoms/cm3 of Al using a vertical Bridgman system. Analysis by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), particle induced X-ray emission (PIXE) and particle induced gamma ray emission (PIGE) were used to obtain information on the structure defects and chemical composition of the crystals. The doped ingots showed good structural homogeneity when compared with the undoped alloy, and they were free from cracks and micro cracks. All of the obtained ingots present precipitates, twins and grains with different concentrations of In. The small compositional variation observed in the doped ingots along the radial direction (measured by PIXE), may be related to the solid–liquid interface’s quasi-equilibrium behavior. Regarding to the growth direction, it was observed that the undoped ingots exhibit a higher segregation phenomenon of the third element than the doped ingots. The obtained results indicate that aluminum influences the indium distribution in the ingots, thus ternary ingots with more homogeneous composition can be obtained and consequently electrical properties improved.

A data acquisition system and the SAD2 software, that provide characteristic cooling curves, in combination with microstructure analysis were used to study precipitates formation in the AA380.0 aluminium alloys modified by adding extra magnesium. The samples were solidified with distinct cooling rates caused by carrying out the solidification in shell and permanent molds. The mathematics processing of the cooling curves in agreement with the microstructure analysis have confirmed the remarkable presence of both the Al–Si dendrite network and the Mg2Si interdendritic phase in the alloys with the addition of extra magnesium.

This paper reports results of an investigation of the behaviour of several etchants in revealing structural defects in Al-, Te-, Cd- and Te/Cd-doped GaSb. Etchants previously suggested for GaSb, as well as two etchants developed for GaAs and InP, were tested and modified in an attempt to establish the best conditions under which a given etchant may be used and what defects it is likely to reveal. Both the solutions consisting of H 2 O 2 -H 2 SO 4 and 3%Br-methanol provided reproducible etch figures on dislocations, the former on the (111)Ga, (111)Sb, (100) and (110) planes, and the latter only on the (111)Ga plane. In contrast, H 2 O 2 -HC1 and HC1-HNO 3 -H 2 O did not perform satisfactorily in revealing dislocations in the analyzed samples. Using permanganate etchant, it was possible to observe growth striations only in the n-type GaSb. The CrO 3 -HF solution revealed growth striations on both the p-type and the n-type GaSb as well as defects formed due to constitutional supercooling. A new etchant, based on ceric sulfate, was developed to delineate growth striations along the Te-doped GaSb crystals.

A liga Zn-22%Al apresenta uma microestrutura complexa, tanto no estado bruto de fusão, como após envelhecimento, devido à transformação eutetóide (β → α + η). O objetivo desse trabalho é relacionar a morfologia das fases presentes em lingotes brutos de fusão e após envelhecimento com a taxa de solidificação. Amostras dos lingotes da liga Zn-22%Al foram analisadas por microscopia eletrônica de varredura (MEV) e EDS (Energy Dispersive Spectroscopy). A estrutura α + η com morfologia lamelar em amostras brutas de fusão transforma-se em uma textura refinada tendendo a globular-equiaxial após o envelhecimento. Observou-se que a dureza das amostras está fortemente relacionada com a morfologia da estrutura α + η. Por outro lado, a composição e a morfologia das fases são conseqüências da taxa de solidificação e resfriamento.

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In this paper we present results related to the development of an alternative and non-destructive method for determining and mapping the etch pits density, in real time, by using digital imaging processing in association with an optical system. The density and distribution of the dislocation etch pits were obtained by the specular reflection produced by either a He-Ne laser or a white light on an etched semiconductor material surface. As the pits related to dislocations have a typical geometric form according to crystallographic plane of the surface they become more evident than other defects and, as a consequence this allows to reach selectivity for this specific defect by the system. The efficiency of the suggested method was accomplished by comparing the results obtained with conventional analysis done by optical microscopy. The proposed automated system demonstrated to be capable of covering large surface areas very rapidly, if compared to a traditional method in view of the fact that by using optical microscopy the density and distribution of defects can be determined only in the small regions which makes the mapping of the entire sample laborious. Furthermore, this system can be easily adapted to a line production providing direct qualitative and quantitative information on the substrate quality.