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Fernando Gabriel da Silva Araújo

Bio: Fernando Gabriel da Silva Araújo is an academic researcher from Universidade Federal de Ouro Preto. The author has contributed to research in topics: Tailings & Iron ore. The author has an hindex of 7, co-authored 42 publications receiving 202 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the feasibility and sustainability of the use of iron ore tailings as additives in the ceramic industry was studied from the economic and technological points, and the results indicated that the addition of tailings from concentration of iron ores for the production of red ceramics was highly feasible both technically and environmentally.

64 citations

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TL;DR: This work focuses on the verification of the sustainability of reverse logistics suggested by the legislation and the mandatory points, evaluating its costs and the possible financial gain with recycling of the waste.
Abstract: The advancement of technology and development of new electronic and electrical equipment with a reduced life cycle has increased the need for the disposal of them (called Waste of Electric and Electronic Equipment or simply e-waste) due to defects presented during use, replacement of obsolete equipment, and ease of acquisition of new equipment. There is a lack of consumer awareness regarding the use, handling storage, and disposal of this equipment. In Brazil, the disposal of post-consumer waste is regulated by the National Solid Waste Policy, established by Law No. 12305 and regulated on the 23rd December 2010. Under this legislation, manufacturers and importers are required to perform a project for the Reverse Logistics of e-waste, though its implementation is not well defined. This work focuses on the verification of the sustainability of reverse logistics suggested by the legislation and the mandatory points, evaluating its costs and the possible financial gain with recycling of the waste. The management of reverse logistics and recycling of waste electrical and electronic equipment, or simply recycling of e-waste, as suggested by the government, will be the responsibility of the managing organization to be formed by the manufacturers/importers in Brazil.

27 citations

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TL;DR: In this article, 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.
Abstract: 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 dualphase 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 dualphase samples showed HVN from 362 to 429.

19 citations

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TL;DR: In this article, 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.
Abstract: 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 Mossbauer 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.

12 citations

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TL;DR: In this paper, the results showed that an increase in the heating rate had no influence on Ac1, but Ac3 increased 115oC, and the results proved to be of general use, as they also predicted the results of works on other steels with high values of correlation coefficients.
Abstract: 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.

12 citations


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Journal Article
TL;DR: In this article, a theory of the band strength based on the point-charge model and p-d mixing has been developed and applied to the data with results in fair agreement with experiment.
Abstract: The polarized optical spectra of the ions Ti3+, V3+, Cr3+, Mn3+, Co3+, and Ni3+ in corundum single crystals have been studied at temperatures from 4.2° to 1200°K. A theory of the band strength based on the point‐charge model and p‐d mixing has been developed and applied to the data with results in fair agreement with experiment. The effects of temperature show that the vibrational‐electronic contribution to band strength is quite small at low temperature but may be appreciable at high temperatures. The crystal‐field parameters have been calculated as convergent lattice sums. The observed trigonal‐field parameter has the opposite sign from that calculated by the point‐charge model if the impurity ion is assumed to occupy an Al3+ ion position in the lattice, but has the same sign as calculated for an ion 0.1 A displaced along the c3 axis toward the empty octahedral site. Details of the spectra have been interpreted as showing that the surroundings of an ion are distorted in some electronic states.

543 citations

Journal ArticleDOI
TL;DR: In this paper, the weld residual stresses (RS) in a 25mm thick ferrite steel plate with newly developed low-temperature transformation (LTT) welding wire were investigated by finite element method and neutron diffraction (ND) measurement.

127 citations

Journal ArticleDOI
TL;DR: In this article, the possibility of immobilizing several heavy metals from gold mine tailings by reactive geopolymerization technique has been investigated, and the results show that various elements (Cr, Cu, Ni, Zn and Mn) from goldmine tailings are able to immobilize almost completely by alkali activation with proper co-binder material.

126 citations

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TL;DR: Snyder and Bish as discussed by the authors discussed the Reference Intensity Ratio approach (also known as Chung method), the method of standard additions, and the full pattern-fitting approach using both the Rietveld method and the observed patterns method.
Abstract: It has been more than twenty years since the excellent volume of Reviews in Mineralogy dedicated to Modern Powder Diffraction was published (Bish and Post 1989). That volume contained a series of key articles ranging from the basic of powder diffraction to sample preparation and synchrotron and neutron powder diffraction. Within that volume, quantitative phase analysis was extensively discussed in a specific chapter (Snyder and Bish 1989). Snyder and Bish (1989) discussed the Reference Intensity Ratio approach (also known as Chung method), the method of standard additions (also known as spiking method) and the full pattern-fitting approach using both the Rietveld method and the observed patterns method. The reader is referred to that volume for the basics of powder diffraction, and to the specific chapter by Snyder and Bish (1989) for the history of quantitative phase analysis from powder diffraction and for a discussion or the early findings. Quantitative phase analysis by X-ray powder diffraction dates back to 1925 (Navias 1925). In this work, the amount of mullite obtained by firing selected clays (and a feldspar) was determined by the direct comparison of the intensities of two diffraction lines of the fired samples with those of pure mullite. The patterns were recorded on photographic negatives after an X-ray exposure of 165 hours (almost a week). Quantitative phase analysis (QPA) from diffraction data can be obtained from a number of methods explained in classical books (Klug and Alexander 1974; Cullity 1978; Snyder and Bish 1989; Zevin and Kimmel 1995; Jenkins and Snyder 1996). However, it is now safe to say that QPA from powder diffraction data is nowadays mainly based on the Rietveld methodology (Rietveld 1969; Hill and Howard 1987; Bish and Howard 1988; Bish and Post 1993; Madsen and Scarlett 2008). Hence, …

121 citations

Journal ArticleDOI
TL;DR: In this paper, the most appropriate preparation conditions of producing autoclaved aerated concrete (AAC) with iron tailing was studied based on the background that a large amount of iron tailings was stockpiled in China.

119 citations