cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.6857138.v1
title: Study of the antifungal activity of materials containing coal from disused batteries

description: ABSTRACT The large number of batteries that are discarded and the environmental impact that the inadequate disposition of the waste of the same produces impelled to its recycling. Both alkaline and zinc-carbon batteries have as their main components zinc and carbon mixed with other oxides, in their internal fill. In this work, the silica synthesis was carried out using the sol-gel method from the tetraethylorthosilicate precursor and the ammonium hydroxide catalyst, carbon from the recycling of disused batteries was added in 0.1, 1.0 and 10.0 C % (w/w), respectively. This support was functionalized by 3-aminopropyltriethoxysilane in a 1: 1 ratio and subsequently it was impregnated by the incipient wetness with silver nitrate, resulting in 1 and 2% Ag (w/v) adsorbed. These solids were characterized by SBET, DRX, potentiometric titration, SEM-EDX and TEM techniques. The antifungal activity of the solids was assessed against the fungi Chaetomium globosum, Aspergillus sp. and Cladosporium sp. by plaque inhibition test. The best results obtained showed a degree of inhibition close to 100% against Cladosporium sp. with samples impregnated at both Ag concentrations. In a next stage modifications will be made in the synthesis of the siliceous material to increase its antifungal effectiveness.
DOI: 10.6084/m9.figshare.6857129
title: Effect of heat treatment on the mechanical strength, intergranular and exfoliation corrosion of 7075 aluminum alloy

description: ABSTRACT In this study, the effects of heat treatments in the peak aged (T6), overaged (T73) and retrogression and reaging (RRA, retrogression at 200 °C for 10 min) on the microstructure, mechanical strength, exfoliation corrosion and intergranular corrosion of aluminum alloy 7075, has been investigated by optical microscope, scanning electron microscopy, tensile tests, ASTM G110 tests, ASTM G34 tests, polarization curve and electrochemical impedance spectroscopy (EIS). The results of intergranular corrosion tests (ASTM G110) and exfoliation corrosion tests (ASTM G34), applied to the three treatments defines an order of susceptibility to corrosion given by: T6 &gt; T73 &gt; RRA. The trends of the corrosion resistance were further confirmed by polarization curve and EIS test. The RRA heat treatment improved the intergranular-exfoliation corrosion resistance of aluminum alloy 7075 without sacrificing the mechanical strength compared to T6 temper. The effect of heat treatment on mechanical strength and corrosion resistance is explained based on the state of precipitation in the matrix and grain boundaries.
DOI: 10.6084/m9.figshare.6857132
title: Microstructural evolution of aluminum-A356 alloy with and without SiC reinforcement submitted to mechanical milling

description: ABSTRACT The effect of milling time on the crystallite size, microstrain and Vickers microhardness, of an aluminum alloy A356 (Al-7wt % Si) with and without SiC reinforcement (15 wt%) was studied. The metal alloy powders were obtained by the rotating electrode process (REP) from cylinders of the alloy, the obtained powders present spherical morphology with an average size of 150 µm and an average microhardness of 94 HV0,1. The alloy with and without reinforcement was subjected to mechanical milling in a high energy mill SPEX 8000D with effective milling times of 3, 6, 9 and 12 hours. The microstructural evolution of the obtained samples was evaluated by X-ray diffraction, Vickers microhardness and optical microscopy. It is noted that the values of microhardness of the alloy with and without reinforcement milling for 3 hours are very similar; for higher milling times, samples reinforced with SiC reach higher values than the samples without reinforcement. This increase in the microhardness is achieved thanks to the uniform distribution of reinforcement particles, the strain hardening of the metal matrix and microstructural refinement produced by mechanical milling. It is appreciated that the composite reaches a crystallite size somewhat smaller than the alloy, although both show similar behavior. The crystallite size presents a rapid decrease in the early hours of milling and then remains almost constant
DOI: 10.6084/m9.figshare.6857126
title: Manufacturing of Cu-Sn foams through SDP

description: ABSTRACT This work reports the processing of bronze foams manufactured by using the powder metallurgy method known as Sintering Dissolution Process. During the sintering step, a device with controlled atmosphere separated from the heating furnace was employed to avoid the quick oxidation of metal particles. The device allows to control its internal atmosphere with an inert gas avoiding the employment of a controlled atmosphere furnace (a furnace of this kind incorporates the heating and the control atmosphere systems itself). The metal used for the present study was bronze powders with a composition of 85%Cu–15%Sn, ~8.7g/cm3 in density, and particle size of 74µm. Spherical carbamide (CH4N2O) with particle size of ~1mm was chosen as Space Holder Particles (SHP). The maximum porosity Pf and minimum density ρf values were 42.8% and 3.61g/cm3, respectively. As the carbamide content is increased, the bronze powders content is diminished and consequently Pf is increased and ρf is diminished, as it would logically be expected. The minimum obtained ρf value corresponds only to 41.4 % of the bronze density (~8.7g/cm3). On the other hand, the plots of stress σ vs strain ε indicated σmax values between 26.86 and 8.45 MPa (20 and 35%vol. of carbamide, respectively). These obtained values indicate a good metallurgical bond among particles, caused by the uniaxial compression step and sintering at the correct Ts, previously determined (580ºC). The σmax decreases as the SHP content increases, which is due to a significant amount of porosity generated by the SHP dissolution and by the inclusion of void spaces among the metal particles; the both of them imply a lower area supporting the load, and consequently a reduction in σmax value for the samples. The results are interpreted in terms of increase and decrease of the carbamide and the bronze powder content in the sample, respectively.
DOI: 10.6084/m9.figshare.6857126.v1
title: Manufacturing of Cu-Sn foams through SDP

description: ABSTRACT This work reports the processing of bronze foams manufactured by using the powder metallurgy method known as Sintering Dissolution Process. During the sintering step, a device with controlled atmosphere separated from the heating furnace was employed to avoid the quick oxidation of metal particles. The device allows to control its internal atmosphere with an inert gas avoiding the employment of a controlled atmosphere furnace (a furnace of this kind incorporates the heating and the control atmosphere systems itself). The metal used for the present study was bronze powders with a composition of 85%Cu–15%Sn, ~8.7g/cm3 in density, and particle size of 74µm. Spherical carbamide (CH4N2O) with particle size of ~1mm was chosen as Space Holder Particles (SHP). The maximum porosity Pf and minimum density ρf values were 42.8% and 3.61g/cm3, respectively. As the carbamide content is increased, the bronze powders content is diminished and consequently Pf is increased and ρf is diminished, as it would logically be expected. The minimum obtained ρf value corresponds only to 41.4 % of the bronze density (~8.7g/cm3). On the other hand, the plots of stress σ vs strain ε indicated σmax values between 26.86 and 8.45 MPa (20 and 35%vol. of carbamide, respectively). These obtained values indicate a good metallurgical bond among particles, caused by the uniaxial compression step and sintering at the correct Ts, previously determined (580ºC). The σmax decreases as the SHP content increases, which is due to a significant amount of porosity generated by the SHP dissolution and by the inclusion of void spaces among the metal particles; the both of them imply a lower area supporting the load, and consequently a reduction in σmax value for the samples. The results are interpreted in terms of increase and decrease of the carbamide and the bronze powder content in the sample, respectively.
DOI: 10.6084/m9.figshare.6857123
title: Aspects concerning the formation of flue dust in the primary copper industry

description: ABSTRACT In addition to the production of primary copper and ferro silicate slag, the formation of significant amounts of flue dust plays an increasingly important role in today’s copper industry. While valuable elements such as copper and precious metals primarily remain in the heavier, denser products, others such as zinc and lead preferably accumulate in the lighter dust fraction. The deteriorating ore concentrate quality also leads to the introduction of new elements to the copper production system which can cause problems in the process control as well as in the handling of environmentally toxic compounds [1]. This paper explains the formation of flue dust and sets a focus on the differentiation between a physical and a chemical fraction. While mechanically carried along particles form the first section, latter one can be explained in a different way. Due to the high process temperature in primary copper smelting furnaces, certain compounds evaporate and recondense in the following off-gas system. As a result, the chemical analysis of the accumulating flue dust displays a broad variety of different elements [2,3]. In order to determine the behavior of the various elements that can be found among the ore concentrate, vapor pressure calculations help to obtain better knowledge and to draw conclusions. Sulfidic and oxidic compounds of the mentioned elements are also taken into account. Other factors such as the grain size of the dust particles and the potential formation of new phases in the off-gas system therefore help to improve the understanding of the flue dust topic in the primary copper production [1].
DOI: 10.6084/m9.figshare.6857123.v1
title: Aspects concerning the formation of flue dust in the primary copper industry

description: ABSTRACT In addition to the production of primary copper and ferro silicate slag, the formation of significant amounts of flue dust plays an increasingly important role in today’s copper industry. While valuable elements such as copper and precious metals primarily remain in the heavier, denser products, others such as zinc and lead preferably accumulate in the lighter dust fraction. The deteriorating ore concentrate quality also leads to the introduction of new elements to the copper production system which can cause problems in the process control as well as in the handling of environmentally toxic compounds [1]. This paper explains the formation of flue dust and sets a focus on the differentiation between a physical and a chemical fraction. While mechanically carried along particles form the first section, latter one can be explained in a different way. Due to the high process temperature in primary copper smelting furnaces, certain compounds evaporate and recondense in the following off-gas system. As a result, the chemical analysis of the accumulating flue dust displays a broad variety of different elements [2,3]. In order to determine the behavior of the various elements that can be found among the ore concentrate, vapor pressure calculations help to obtain better knowledge and to draw conclusions. Sulfidic and oxidic compounds of the mentioned elements are also taken into account. Other factors such as the grain size of the dust particles and the potential formation of new phases in the off-gas system therefore help to improve the understanding of the flue dust topic in the primary copper production [1].
DOI: 10.6084/m9.figshare.6857132.v1
title: Microstructural evolution of aluminum-A356 alloy with and without SiC reinforcement submitted to mechanical milling

description: ABSTRACT The effect of milling time on the crystallite size, microstrain and Vickers microhardness, of an aluminum alloy A356 (Al-7wt % Si) with and without SiC reinforcement (15 wt%) was studied. The metal alloy powders were obtained by the rotating electrode process (REP) from cylinders of the alloy, the obtained powders present spherical morphology with an average size of 150 µm and an average microhardness of 94 HV0,1. The alloy with and without reinforcement was subjected to mechanical milling in a high energy mill SPEX 8000D with effective milling times of 3, 6, 9 and 12 hours. The microstructural evolution of the obtained samples was evaluated by X-ray diffraction, Vickers microhardness and optical microscopy. It is noted that the values of microhardness of the alloy with and without reinforcement milling for 3 hours are very similar; for higher milling times, samples reinforced with SiC reach higher values than the samples without reinforcement. This increase in the microhardness is achieved thanks to the uniform distribution of reinforcement particles, the strain hardening of the metal matrix and microstructural refinement produced by mechanical milling. It is appreciated that the composite reaches a crystallite size somewhat smaller than the alloy, although both show similar behavior. The crystallite size presents a rapid decrease in the early hours of milling and then remains almost constant
DOI: 10.6084/m9.figshare.6857117
title: Controller for a SPS machine: a proposal PI control

description: ABSTRACT Temperature control is the key to effective sintering process for metal, ceramic and polymer powders. The original control temperature provides an irregular control operation process which affects the material properties due to the spacer involved in it. Furthermore, it is analyzed how the material responds to an electrical input determining a model system with the variables implicated during the process in order to propose an efficient controller. The electrical current passed through a graphite matrix, it contains a compressed powder, so Joule effect is used for resistive heating. This article investigates how temperature control may be improved by a PI feedback controller, it was applied and simulated to the process and control gains were calculated analytically. Finally, the implemented PI controller is compared with the original model to observe the system stability, so that the operational limits are not overtaken maintaining the temperature below the reference.
DOI: 10.6084/m9.figshare.6857120
title: Electrocatalytic effect of Ag and Cd bimetallic nanoparticles towards the reduction of nitrate and/or nitrite ions

description: ABSTRACT The electrocatalytic effect of Cd-Ag bimetallic nanoparticles supported on highly oriented pyrolytic graphite (HOPG) and vitreous carbon (VC) substrates was evaluated for the nitrate and/or nitrite ions reduction reaction. For this, in a first stage, the metallic and bimetallic deposits were obtained on the carbonaceous substrates (CS) using the electrochemical technique of the single potentiostatic pulse. In the case of the bimetallic pair, the amount of Cd was selectively deposited on the Ag nanoparticles previously supported on HOPG or CV, due to the strong interaction between the two metals, using different polarization times. Potentiodynamic studies of the system Cd-Ag/(CS) indicated that, for relatively large polarization times, it is feasible the formation of a surface alloy between Ag and Cd atoms, due to an interdiffusion process between them, which may affect its catalytic activity. The generated particles on HOPG, were characterized by ex-situ AFM and XPS analysis, corroborating the latter the formation of a Cd-Ag alloy. Subsequently, the electrodes modified with metallic and bimetallic nanoparticles, and also the substrates free of deposits, were analysed by cyclic voltammetry in solutions containing nitrate ions. It was found that the reduction of nitrate and/or nitrite ions processes begin at more positive potential values in the case of bimetallic deposits, corresponding to a more pronounced catalytic effect by the presence of Cd and Ag, which could be alloyed in the surface, producing a synergistic effect for the reduction of the anions. Even, a change in the catalytic performance by using longer polarization times for the deposition of Cd on supported Ag nanoparticles was verified, that could be related with that alloyed phase. The reaction products were analyzed by colorimetry and ion exchange chromatography for determining nitrate, nitrite and ammonium amounts in solution.
DOI: 10.6084/m9.figshare.6857114
title: Use of pyrometallurgical processes for obtaining rhenium

description: ABSTRACT Rhenium is a metal that has different obtainment methods. The most used comes from molybdenite roasting. Traditional pyrometallurgical methods like oxidizing roasting are applied, but there are also innovative pyrometallurgical methods as is roasting with carbothermic reduction. This paper presents the behavior of rhenium onto two different roasting processes: oxidizing roasting and toasting with carbothermic reduction. The purpose is to compare both treatments discussing rhenium recovery values. Oxidizing roasting generates several SO2 emissions towards the environment when it is applied to metal sulphides. The carbothermal reduction is a process that uses CaO as sulfur capturer and C as a reductant agent, and eliminates the atmosphere pollution that would have been caused by SO2. Thus the optimum molar ratio of CaO with respect to Re and C, required to accelerate the reduction rate and control S emission to the atmosphere was studied in order to determinate metal sulfide dependence to operational factors of reduction temperature, molar concentrations, roasting times. Furthermore, the oxidizing roasting was worked out with the operating variables of temperature and roasting time for certain ambient conditions. Based on the current results for both roasting processes, the optimal operating conditions for the greatest rhenium recover were obtained.
DOI: 10.6084/m9.figshare.6857117.v1
title: Controller for a SPS machine: a proposal PI control

description: ABSTRACT Temperature control is the key to effective sintering process for metal, ceramic and polymer powders. The original control temperature provides an irregular control operation process which affects the material properties due to the spacer involved in it. Furthermore, it is analyzed how the material responds to an electrical input determining a model system with the variables implicated during the process in order to propose an efficient controller. The electrical current passed through a graphite matrix, it contains a compressed powder, so Joule effect is used for resistive heating. This article investigates how temperature control may be improved by a PI feedback controller, it was applied and simulated to the process and control gains were calculated analytically. Finally, the implemented PI controller is compared with the original model to observe the system stability, so that the operational limits are not overtaken maintaining the temperature below the reference.
DOI: 10.6084/m9.figshare.6857114.v1
title: Use of pyrometallurgical processes for obtaining rhenium

description: ABSTRACT Rhenium is a metal that has different obtainment methods. The most used comes from molybdenite roasting. Traditional pyrometallurgical methods like oxidizing roasting are applied, but there are also innovative pyrometallurgical methods as is roasting with carbothermic reduction. This paper presents the behavior of rhenium onto two different roasting processes: oxidizing roasting and toasting with carbothermic reduction. The purpose is to compare both treatments discussing rhenium recovery values. Oxidizing roasting generates several SO2 emissions towards the environment when it is applied to metal sulphides. The carbothermal reduction is a process that uses CaO as sulfur capturer and C as a reductant agent, and eliminates the atmosphere pollution that would have been caused by SO2. Thus the optimum molar ratio of CaO with respect to Re and C, required to accelerate the reduction rate and control S emission to the atmosphere was studied in order to determinate metal sulfide dependence to operational factors of reduction temperature, molar concentrations, roasting times. Furthermore, the oxidizing roasting was worked out with the operating variables of temperature and roasting time for certain ambient conditions. Based on the current results for both roasting processes, the optimal operating conditions for the greatest rhenium recover were obtained.
DOI: 10.6084/m9.figshare.6857120.v1
title: Electrocatalytic effect of Ag and Cd bimetallic nanoparticles towards the reduction of nitrate and/or nitrite ions

description: ABSTRACT The electrocatalytic effect of Cd-Ag bimetallic nanoparticles supported on highly oriented pyrolytic graphite (HOPG) and vitreous carbon (VC) substrates was evaluated for the nitrate and/or nitrite ions reduction reaction. For this, in a first stage, the metallic and bimetallic deposits were obtained on the carbonaceous substrates (CS) using the electrochemical technique of the single potentiostatic pulse. In the case of the bimetallic pair, the amount of Cd was selectively deposited on the Ag nanoparticles previously supported on HOPG or CV, due to the strong interaction between the two metals, using different polarization times. Potentiodynamic studies of the system Cd-Ag/(CS) indicated that, for relatively large polarization times, it is feasible the formation of a surface alloy between Ag and Cd atoms, due to an interdiffusion process between them, which may affect its catalytic activity. The generated particles on HOPG, were characterized by ex-situ AFM and XPS analysis, corroborating the latter the formation of a Cd-Ag alloy. Subsequently, the electrodes modified with metallic and bimetallic nanoparticles, and also the substrates free of deposits, were analysed by cyclic voltammetry in solutions containing nitrate ions. It was found that the reduction of nitrate and/or nitrite ions processes begin at more positive potential values in the case of bimetallic deposits, corresponding to a more pronounced catalytic effect by the presence of Cd and Ag, which could be alloyed in the surface, producing a synergistic effect for the reduction of the anions. Even, a change in the catalytic performance by using longer polarization times for the deposition of Cd on supported Ag nanoparticles was verified, that could be related with that alloyed phase. The reaction products were analyzed by colorimetry and ion exchange chromatography for determining nitrate, nitrite and ammonium amounts in solution.