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In this study, the effect of the use of foundry sand as a filler on the formation of different layer configurations in polyester/fiber glass composites was investigated. The composites were produced by hand lay-up lamination and their physical, mechanical and morphological properties were investigated. In the samples containing sand as the filler, the configuration of the layers affected the interface region of the phases, thus significantly affecting the mechanical properties of the samples. The morphological analysis of the composites revealed the presence of regions with moderate interaction between the phases (polyester / glass fiber and polyester / foundry sand), which can cause delamination of the layers and consequently the deterioration of the mechanical properties of the composites when compared to the composite without the sand. [ABSTRACT FROM AUTHOR]

The microstructures of steels are altered when exposed to high working temperatures for long periods, which results in varied physical and chemical proprieties. This study evaluates the erosive wear behavior of ASTM A106 steel after it is exposed to high temperatures for long durations. Samples of normalized ASTM A106GrB steel were placed in a muffle furnace at 530 and 630 °C for 50, 100, and 200 h. The erosive wear test was conducted at a speed of 20 m/s for 30 min at 450 °C with an incidence angle of 30°. Irregular alumina was used as the erodent material. The surface characterization was performed using scanning electron microscopy to determine the distribution homogeneity, morphological conditions, quantity, and spheroidization degree of the carbides. The erosive wear test results indicated that there was no volume loss after 50 h of heat treatment at 530 °C. The maximum spheroidization degree was 0.71 after 200 h at 630 °C, which decreased the hardness from 220 to 140 HV. Additionally, the volume loss reached 2.52 cm?. Therefore, the use of the ASTM A106GrB steel at working temperatures higher than 530 °C for more than 50 h decreased the mechanical behavior and the wear resistance, thereby decreasing the lifetime of the system. [ABSTRACT FROM AUTHOR]

Civil construction is one of the largest activities for economic and social development, but also a major waste generator. In this way, the correct disposal of waste is essential for this segment. In this aspect, the work aimed to define the best location for the implantation of a transshipment and sorting area (ATT) and a recycling area (AR), in a city of the Amazon Region, using the Simple Multi-Attribute Rating Technique (SMART). The SMART method is a tool that supports the decision maker based on alternatives with multiple criteria, allowing efficiency in the evaluation and participation of the stakeholders in the development and decision phases, providing greater legitimacy of the process and commitment in the implementation of the results. A case study was developed for the metropolitan area of Belém-PA, and the São Brás neighborhood was investigated as the best site for implantation considering, mainly, the minimum area with vegetation and wells reached and facilitated logistics of the residues. [ABSTRACT FROM AUTHOR]

The large amount of dust generated in electric arc furnace aligned with its chemical composition makes this dust a potential source of iron in the direct reduction iron process. Thus, the aim of this research is to investigate the reduction of pellets produced with electric arc furnace dust using hydrogen as the reducing agent. The kinetic investigation was examined applying the differential method. In addition, the influence of reducing gas stream and temperature in the reduction process were investigated applying the Forced Stepwise Isothermal Analysis technique. The temperature studied varied from 500 to 1000°C with isothermals in each 50°C. The reducing gas was a mixture of 10% of hydrogen and 90% of argon. Then, the product characterization was carried out via scanning electron microscope and X-ray analysis. A thermogravimetric test showed a mass loss of 42 wt% due to the reduction of iron and zinc oxides. Besides this, the reduction occurred in three steps: 550-650°C, 700-800°C, 850-950°C. Between 550-650°C, the reduction was controlled by a nucleation mechanism with an Ea of 41.1 kJ/mol. In the second step (700-800°C), a mixed control between nucleation and diffusion was obtained with an Ea of 89.1 kJ/mol. Furthermore, a crust of iron was formed around the pellet, which hindered the reducing gas diffusion into the pellet. In the third stage (850-950°C), the formation of a sintered structure was noted, which decreased pore volume. The internal diffusion of reducing gases was determined as the controlling mechanism, with an Ea of 130.9 kJ/mol. [ABSTRACT FROM AUTHOR]

The incorporation of wastes to replace the aggregates into concrete has been an alternate to create new routes to disposal it. In this way, the aim of this paper is to study the incorporation of glass wool waste into concrete. The incorporation was performed in two routes. In the first, the waste was milled to be incorporated. The second, the waste was incorporated as-received into concrete. The characterization was performed in the milled waste by chemical analysis, X-ray diffraction, size analysis and scanning electrons microscopy coupled with EDS spectrum. The waste content into the concrete was 2.5, 5.0, 7.5 and 10 wt% in both tests. The results indicate that incorporation of 2.5% of waste decreased the strength resistance in around 3.1% at 28-days curing. Thus, incorporation of glass wool waste into concrete can be an alternative to its disposal. However, the waste content into concrete should be estimated according to the final strength resistance required by concrete. [ABSTRACT FROM AUTHOR]

Zinc ferrite is one of the main components present in the electric arc furnace dust. Furthermore, it is necessary to know the mechanisms involved on the zinc ferrite to determine a process for reusing the electric arc furnace dust. Thus, the aim of this paper is to evaluate the kinetic parameters of the reduction of synthetic zinc ferrite pellets by mixture containing hydrogen. The kinetic investigation was performed via Forced Stepwise Isothermal Analysis method in the temperature range of 500-950 °C. The reducing gas was a mixture of hydrogen (10%) and argon (90%). In addition, Thermo-cal software was used in order to support the reduction reaction behavior. The results indicated that between 550 and 750 °C only iron oxide was reduced. In this step, the nucleation was found to be the controlling mechanism, and an activation energy of 84.9 kJ mol was determined. In temperature >800 °C, it was noted an influence of diffusion on the reduction reaction. Images obtained from scanning electron microscope suggested a change in the pellets microstructure after this temperature presenting a sintered structure. The activation energy of 188 kJ mol was determined at this step. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to study the kinetic reaction of electric arc furnace dust pellets using a reducing gas simulating the reformed natural gas. The kinetic investigation was accomplished via forced stepwise isothermal analysis method. The tests were programmed in the range of 500-1000 °C. It was used a reducing gas contained 25 % of CO and 75 % of H. X-ray patterns were analyzed in order to understand the reduction process. The results show the reduction of electric arc furnace dust pellet occurs in three steps. At 550-650 °C, the zinc ferrite is reduced to magnetite and zinc oxide, followed by the reduction of magnetite to wustite. Carbon deposition on the pellet surface was detected in this step, which impairs the kinetic analysis. In the range of 700-800 °C, wustite is reduced to iron. It was determined a mixed control between nucleation and diffusion with E of 89.2 kJ mol. At 850-950 °C, the main reaction is zinc oxide reduction to gaseous zinc. However, wustite reduction is also observed. The E of 135.5 kJ mol with a mixed control between diffusion and chemical reaction was detected. [ABSTRACT FROM AUTHOR]

Solid waste generation is one of the main problems in the steelmaking process. One of the most problematic waste products is the electric arc furnace dust, which is a by-product rich in iron and zinc and is present as zincite (zinc oxide) or franklinite (zinc ferrite). This work focuses on the reduction kinetics of synthetic zinc ferrite by gases containing hydrogen and carbon monoxide. This process was examined via forced stepwise isothermal analysis. The test was conducted at temperatures ranging from 500 to 950 °C. Reduction of zinc was accomplished using a mixture of hydrogen and carbon monoxide in order to simulate reformed natural gas. The results indicated that reduction of zinc ferrite occurred in two stages (550-750 °C and 800-900 °C). The first stage was characterized by iron oxide reduction, where a mix control between nucleation and diffusion was determined. The apparent activation energy obtained was 71.5 kJ mol. The second stage was characterized by zinc oxide reduction, where the controlling mechanism was identified as a mixed control between diffusion and phase boundary reaction. The apparent activation energy was 135.5 kJ mol. The formation of a dense layer of metallic iron around the unreacted core may have caused the apparent activation energy to increase. [ABSTRACT FROM AUTHOR]

The study of pellets morphology is an important tool to understand possible mechanisms involved during its reduction reaction. Thus, the aim of this paper is characterize three different iron ores and correlate its morphology obtained after the complete reduction with its features. The reductions tests were accomplished in a horizontal tubular furnace at 850°C. Two reducing atmosphere were used. The first one contained hydrogen. The second one was a mixture between first gas + carbon monoxide. The iron ore characterization was carried out by size analysis, surface area and X-ray analysis. Scanning electron microscopy was used to obtain the morphology from the reduced pellets. The results showed a greater number of whisker were obtained with more fine ore. Furthermore, it was noted that carbon monoxide provided a lesser number of pores and greater number of whisker. [ABSTRACT FROM AUTHOR]

Basic oxygen furnace (BOF) dust is a by-product of steel plants that is rich in iron oxide. Reduction of this by-product may provide reutilization alternatives in steel industry. In this context, kinetic study was conducted using BOF dust pellets applying the forced stepwise isothermal analysis method. This work examines the reduction of BOF dust pellets using a mixture between hydrogen and carbon monoxide. Mass loss of 26 % was obtained after reduction of the BOF. Carbon oxide present in the reducing gas led to the formation of a carbon layer around the pellet between 550 and 650 °C. At higher temperatures, from 700 to 850 °C, it was observed that reduction was controlled by porous diffusion. In the range 900-1,000 °C, the control mechanism was determined as reactive species diffusion through metallic alloy lattice in individual particles. [ABSTRACT FROM AUTHOR]

The granite processing market is one of the most promising business areas of the mineral sector, with an average growth of the world production of about 6% per year. The granite extraction generates residues in the form of powder rock of 20-25 wt.% of the total benefited. The granite dust must be carefully managed since it can cause siltation of rivers and human health risks. This paper presents two routes for the final destination of this waste: the vitrification process aiming the production of fibers for thermo-acoustic insulation, and the magnetic separation in order to recover the steel grit. Results showed that the forms of treatments presented are economically and ecologically viable since they represent a cost reduction in the waste disposal, and also provide the production of new materials with commercial value. [ABSTRACT FROM AUTHOR]

The generation of basic oxygen furnace dust is a problem that companies found in the steel industry. In this way, studies are important to obtain, or at least indicate a way to recycle this waste. The direct reduction can be an alternative, once this method produces rich in iron. Thus, the goal of this paper is study the kinetic of reduction of basic oxygen furnace dust pellet using a mixture containing hydrogen and argon. Thereby, the mechanism and apparent activation energy that involve the reduction can be found out. The kinetic analysis was carried out applying the Forced Stepwise Isothermal Analysis method. The temperatures used in the test were between 500°C to 1,100°C. The results showed that reduction occurred in three steps. In the first step, nucleation was the control mechanism. It was found an apparent activation energy about 24kJ/mol in this step. In the second and third stage, the control mechanism was diffusion. In the second step, the apparent activation energy was 54.9 kJ/mol, while in the third step the apparent activation energy was 80.7 kJ/mol. [ABSTRACT FROM AUTHOR]

This paper presents the results obtained with the production of briquettes from the steel grit found in the residue of ornamental rocks. The grit recovered by magnetic separation was characterized by titrimetric analysis, EDS (Electron Dispersive Spectroscopy) and X-ray diffraction for the analysis of iron concentration in the residue. The size and distribution of particles were obtained by the granulometric analysis method and scanning electron microscopy (SEM). The process resulted in a concentrate containing 93% metallic iron. The maximum load before fracture of the green briquettes was 1.02kN and of the dry briquettes was 3.59kN. [ABSTRACT FROM AUTHOR]

Fluorspar (CaF2) is the most used flux in hot metal desulfurizing mixtures. However, its use can cause refractory wear and environmental contamination, prompting research efforts to develop alternative desulfurizing mixtures. This study aims to investigate the replacement desulfurizing mixtures containing fluorspar by other desulfurizing mixtures containing a new flux developed without fluorspar named MIX. The influence of varying the mass of these desulfurizing mixtures, temperature, and stirring of the system on the efficiency of hot metal desulfurization was also studied. The desulfurization experiments were carried out in an electric resistance furnace, at a temperature of 1370°C. Hot metal samples were taken to measure the change in sulfur content in the experiments. FactSage 8.0 software, was used to determine the phases present in the desulfurizing mixtures, and these phases were correlated with the hot metal desulfurization efficiency. The efficiency of the desulfurizing mixtures was also correlated with the Desulfurization Factor. The results showed that desulfurizing mixtures containing fluorspar are the most efficient mixtures. However, fluorspar-free desulfurizing mixtures containing MIX can achieve similar efficiencies with increases in mass, temperature, and system stirring. The results also showed that the most efficient desulfurizing mixtures are those with higher percentages of solid CaO and lower percentages of the solid phases 3CaO.SiO2 and CaS and, consequently, a higher Desulfurization Factor. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the replacement of Portland cement by ceramic plates waste into mortar. The ceramic plate waste was milled and characterized through chemical analysis and particle size analysis. Then, it was elaborated mixtures in order to replace 5, 12 and 20 wt.% of Portland cement by ceramic plates waste. In addition, the consistency indices, water absorption, void index, specific mass, tensile strength in flexion and axial compression were determined for each mixture. The results showed that the ceramic plates waste are composed by of SiO2 (69.09 wt.%) and Al2O3 (15.4 wt.%). The replacement of 5 and 12 wt.% decreased the mortar porosity. The tensile strength in flexion assays showed an increase on this property. However, the axial compression tests presented a decrease of 0.9% and 2.5% for replacement of 5 and 12 wt.%. [ABSTRACT FROM AUTHOR]

In this report, we evaluated the effects of selenylated indoles (3a–d) on lipid membranes and their capacity to interact with DNA. These selenylated indoles increased the motion rate of the polar region of lipids and compounds 3b–d ordered the non-polar region. The DNA cleavage ability was observed only for 3c. [ABSTRACT FROM AUTHOR]

The aim of this paper is to analyze mixtures of basic oxygen furnace slag and granite waste in order to produce Portland cement. X-ray patterns were carried out in both the basic oxygen furnace slag and granite waste. Then, mixtures were prepared to obtain the binary basicity of 0.5, 0.9 and 1.2. The mixtures were melted at 1500°C. Two cooling steps were performed. The first cooling step was accomplished inside the furnace in order to determine the phases formed during the melting step. The second cooling process was carried out in water in order to obtain an amorphous structure. Images via scanning electrons microscopy and EDS spectrum were obtained for the mixtures cooling in water. The results showed that basic oxygen furnace slag contains a higher percent of CaO. A binary basicity of 4.6 was determined. The granite waste appeared as mainly a quartz phase. During the slow cooling step, silicates (akermanite and gehlenite) were formed. On the fast cooling step, amorphous structures were obtained. In addition, images obtained via scanning electrons microscopy showed glass structures. EDS spectrum indicated that the glass structures were composed for calcium silicates. Thus, the results suggest that mixtures using basic oxygen furnace slag and granite waste presented characteristics desirable for Portland cement production. [ABSTRACT FROM AUTHOR]

The steel industry in Brazil is responsible for around 5% of total carbon dioxide emissions, releasing around 1.85 tons of CO 2 for every ton of steel produced. The use of charcoal in self-reducing iron ore briquettes can be an alternative to reduce fossil fuel consumption and reduce carbon emissions in the primary steelmaking industry, however, the particle size can affect the reduction process. This study aims to analyze the reduction kinetics of charcoal briquettes in three particle size ranges. To this end, the charcoal was characterized using thermogravimetric analysis to determine the contents of fixed carbon, ash and volatiles, analysis of sulphur in the charcoal by combustion in a tube furnace, determination of particle size by laser granulometer, elemental chemical analysis of the charcoal ash by X-ray fluorescence spectrometry. The briquettes were reduced in a thermogravimetric balance to 1100 °C with heating rates between 10 and 40 °C/min. They were characterized by X-ray diffraction. Finally, a kinetic study was carried out using the Coats-Redfern method. In all the briquettes, the controlling mechanism was diffusion. In the mixture with fines, the activation energy ranged from 31.95 to 33.72 kJ/mol and 120.29–137.17 kJ/mol. For the mixture with medium grain size, the activation energy ranged from 58.1 to 89.42 kJ/mol and 107.83–153.50 kJ/mol. X-ray diffraction revealed phases of hematite and magnetite at 800 °C, while at 900 °C phases of wustite and faialite and metallic iron were identified. • Particle size affects self-reducing briquette's reaction rate in iron ore reduction kinetics. • Charcoal-based briquettes offer a viable solution for sustainable steel production, reducing fossil fuel use. • The activation energy increases in the second stage of the briquette reduction process. [ABSTRACT FROM AUTHOR]

The aim of this paper is characterize printed circuit board of computers and propose a hydrometallurgical route for silver recovery present in its composition. Initially, the printed circuit board was comminuted in both knife and hammer mills. The comminuted material was characterized by sieve analysis, chemical analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) and loss on ignition. Leaching tests were conducted in sulfuric acid, sulfuric acid in an oxidizing medium and nitric acid. The results indicated that the printed circuit board is mainly composed of copper (19.42%). Silver content of 0.045% was found. The route for silver recovery was leaching in sulfuric acid at 75°C for 18 hours. Then, leaching in sulfuric acid at 75°C in an oxidizing medium for 6 hours and nitric acid leaching at room temperature for 2 hours. Through of this route, 96.6% of silver was recovered. [ABSTRACT FROM AUTHOR]

We report an efficient and practical procedure for the synthesis of cholesterol containing unsymmetrical liquid crystals dimers. Liquid crystalline and thermal properties were studied by POM, TGA, DSC, and SAXS analysis. All final products (3a-d) presented liquid crystal properties. The presence of smectic (compounds 3a, 3b, and 3d) and chiral nematic (3 c) mesophases evidenced by polarised optical microscopy (POM) and further confirmed by small-angle X-ray scattering (SAXS) analyses. The compound 3 c remains supercooled until room temperature and presented enantiotropic mesomorphism at a low temperature. This characteristic of organisation and mesomorphism at room temperature makes compound 3 c an ideal candidate for technological applications. The SAXS analyses further suggest possibly the presence of smectic clusters within the nematic liquid crystalline phase. All compounds presented high thermal stability at around 300°C when tested for their thermal properties. The highest occupied molecular orbital (HOMO) energies were estimated from cyclic voltammetry (CV) and used together with the optical absorption measurements to determine the band gap and lowest unoccupied molecular orbital (LUMO) energies. The values obtained were: HOMO (–5.81 to – 6.03 eV), LUMO (–1.53 to – 2.12 eV), and band gap (3.88 to 4.28 eV). [ABSTRACT FROM AUTHOR]

The effect of composition and firing temperature on porosity and bending strength of porous ceramic plates for using in ventilated façades were investigated. Two byproducts, basalt and lime mud, were used to obtain porous ceramic plates in accordance with the circular economy concept. Basalt, which is a fine powder‐based byproduct generated from the processing of basaltic rock, was used to replace feldspar as the flux mineral in a ceramic composition. Lime mud, a byproduct of the pulp and paper mill process and containing a high content of calcium carbonate (CaCO3), was incorporated in the ceramic composition to generate pores. The specimens were prepared using three different amounts of lime mud (20, 30, and 40 wt%) and three firing temperatures (900°C, 1000°C, and 1100°C), and their porosity and bending strength were determined. The highest performing specimen (5.1 ± 1.3 MPa bending strength and 42.6 ± 0.5% porosity) was obtained by using 40 wt% of lime mud and a firing temperature of 1100°C with potential for further thermal tests in a ventilated façade in comparison with a commercial porcelain ceramic tile as reference material. [ABSTRACT FROM AUTHOR]

The effects of porous ceramic plates on the thermal behavior of ventilated façades were evaluated, and the results are presented herein. Thermal behavior in a ventilated façade of specimens containing 40 wt% of lime mud and a firing temperature of 1100°C was evaluated and compared with a commercial porcelain ceramic tile, which was the reference material. An experimental apparatus was designed to evaluate the thermal performance of the studied ventilated façades. The results revealed that the ventilated façade composed of the studied porous ceramic tiles produced a greater reduction in temperature between the external environmental and the interior of a box representing a building (ΔT5) of 65.7°C, compared with the façade composed of the commercial porcelain ceramic tiles (ΔT5 = 56.0°C) and even the traditional façade (ΔT5 = 49.1°C). Thus, porous ceramic tiles based on byproducts are promising candidates for ventilated façade systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of benzazole-based pyromellitic diimide (PMDI) derivatives. • Fluorescence in the solution and the solid state. • Very large Stokes shift due to ESIPT process. • Photophysical properties are tailored by the pH. This study describes the synthesis of new pyromellitic diimide (PMDI) derivatives obtained in good yields from the reaction between pyromellitic dianhydride and aminobenzazoles reactive to proton-transfer in the excited state (ESIPT). In this investigation, a non-ESIPT PMDI was also prepared for comparison. These compounds presented absorption maxima in the ultraviolet region attributed to the allowed 1π-π* electronic transitions. Redshifted absorptions were observed for the ESIPT compounds (3b-3c) due to their π-extended conjugation if compared to the non-ESIPT dye (3a). The compounds presented fluorescence emissions between 300 and 600 nm, dependent on the solvent polarity and their chemical structures. While compound 3a presents a single emission, a dual fluorescence could be observed for compounds 3b-3c. As expected for ESIPT compounds, the emission at higher energies could be related to the excited enol conformer (E*), and the emission with a large Stokes shift was attributed to the keto tautomer (K*). All compounds presented fluorescence emission in the solid state, whereas the ESIPT derivatives presented redshifted emissions with a large Stokes shift, as expected. Cyclic voltammetry was employed to investigate the electrochemical properties of these compounds. The HOMO and LUMO energy levels were estimated at −5.40 to −5.00 eV and −2.84 to −2.62 eV, and good thermal stability (T d > 150 °C) was observed. Quantum chemical calculations using TD-DFT and DFT were performed to investigate the electronic and photophysical features of the molecules. [ABSTRACT FROM AUTHOR]