cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.6857783.v1
title: Study of hot-workability of titanium alloys through hot-torsion testing and its application to the optimization of forging and extrusion processes

description: ABSTRACT In the development of hot metal forming, the metallic products must comply with the requirements imposed by current standards. In some cases, the required microstructure can only be obtained through thermomechanical processing. With titanium and its alloys, small ranges of good workability are an additional difficulty. In this work the hot-workability of aeronautical quality titanium alloys was studied through hot torsion and compression testing. The results were used to define the m teri l’s pl stic behaviour seeking to optimize forging and extrusion operating parameters, such as temperature, strain rate, area reduction, etc. Additionally, different processing routes were simulated through hot-torsion testing and the resulting microstructures were analysed and successfully compared to the current standards. At the same time, the minimum amount of area reduction required to obtain such microstructure was determined. The results of hot-workability testing plus the information registered in full-scale Grade 2 Ti extrusion tests were used to simulate different extrusion processes with FEA. To calibrate the FE model it was also necess ry to ev lu te the illet’s temper ture evolution through the press’s feeding system nd the behaviour of the available lubricants. The FE model proved to be accurate to predict the required extrusion force for the tested geometries. This way, the feasibility of extruding different sections was determined and the operating parameters were optimized to maintain the extrusion pressure within operative limits as well as to obtain the m teri l’s properties nd microstructures required in current st nd rds.
DOI: 10.6084/m9.figshare.6857777
title: Diagrama de fases experimental Fe-Sn-Zr. Nuevos resultados del corte isotérmico de 800 °C

description: ABSTRACT The Zr-based alloys are extensively applied in the field of nuclear technology. Alloyed with Sn and Fe, Zr is the main element in the zircaloy-type alloys, currently vastly used as structural elements and as containers of burnable elements in nuclear reactors. This ternary metallurgical system is also a component of more recently developed alloys such as Zirlo (USA). Although Zr is a major component in all of them, it is most important to know the phase diagrams of their components as best as possible. The Fe-Sn-Zr phase diagram has been systematically studied by our research team for many years. Considerable advancement has been made in the design of the phase diagram at 800°C, however, some regions in the Gibbs triangle are still unsolved. In order to evaluate these regions experimentally, a ternary alloy set was designed and prepared. These alloys were thermally treated at the chosen temperature for 2928 hours, and characterized by applying metallography techniques, X-ray diffraction and microanalysis. The presence of Y and Fe6Sn6Zr was confirmed, the presence of phase X” was verified, and 2- and 3-phase existence fields were determined. Finally, phase balance boundaries in the regions under study were traced, completing, to a great extent, the phase diagram for the isothermal cut analysed.
DOI: 10.6084/m9.figshare.6857774
title: Synthesis and properties of nickel/graphene electrodes for hydrogen generation

description: ABSTRACT The use of nanomaterials, such graphene oxide (GO), as blocks for the synthesis of hybrid materials has been extensively studied in recent years. In this paper a simple and reproducible method for the synthesis of hybrid nickel/graphene electrodes is presented. This method involves the modification of a conventional electroplating nickel bath by incorporating graphene oxide flakes, so the synthesis can be industrially scalable. The synthesized catalyst was structurally and electrochemically characterized. The XRD studies show no appreciable change in the lattice parameter, but a decrease is observed in the relationship between (200)/(111) planes related to an increase in catalyst stability. Raman spectra show the characteristic reduced GO bands on the catalyst matrix. Also, the formation of nickel hydrides in the nickel/graphene catalyst is not observed, unlike the pure nickel electrode. The kinetics of hydrogen evolution reaction (HER) was studied in both, conventional nickel and nickel/graphene catalysts, finding changes in activity. The hybrid catalyst has a higher catalytic activity towards the HER and the presence of GO in the Ni matrix inhibits the nickel hydride formation with the consequent loss of catalytic activity.
DOI: 10.6084/m9.figshare.6857777.v1
title: Diagrama de fases experimental Fe-Sn-Zr. Nuevos resultados del corte isotérmico de 800 °C

description: ABSTRACT The Zr-based alloys are extensively applied in the field of nuclear technology. Alloyed with Sn and Fe, Zr is the main element in the zircaloy-type alloys, currently vastly used as structural elements and as containers of burnable elements in nuclear reactors. This ternary metallurgical system is also a component of more recently developed alloys such as Zirlo (USA). Although Zr is a major component in all of them, it is most important to know the phase diagrams of their components as best as possible. The Fe-Sn-Zr phase diagram has been systematically studied by our research team for many years. Considerable advancement has been made in the design of the phase diagram at 800°C, however, some regions in the Gibbs triangle are still unsolved. In order to evaluate these regions experimentally, a ternary alloy set was designed and prepared. These alloys were thermally treated at the chosen temperature for 2928 hours, and characterized by applying metallography techniques, X-ray diffraction and microanalysis. The presence of Y and Fe6Sn6Zr was confirmed, the presence of phase X” was verified, and 2- and 3-phase existence fields were determined. Finally, phase balance boundaries in the regions under study were traced, completing, to a great extent, the phase diagram for the isothermal cut analysed.
DOI: 10.6084/m9.figshare.6857771
title: Estudio y caracterización del efecto de compuestos con titanio sobre el sistema hidruro Li-B-Mg-H con alta capacidad de almacenamiento de hidrógeno

description: ABSTRACT One of the main constraints for the implementation of hydrogen as energy carrier is the lack of an efficient and safe hydrogen storage system. Hydrogen storage in solid state through hydride compounds formation is a potential alternative to address this problem. In this work, it is studied the effect of different titanium based compounds (TiB2, LixTiO2) on the kinetic behavior of 2LiBH4+MgH2 reactive hydride composite. It is found that nanometric particles of titanates (LixTiO2) noticeably improve the first non-isothermal dehydrogenation behavior of the 2LiBH4+MgH2, reducing the complete H2 release time from 35 h to 2 h. Moreover, the LixTiO2 addition improves the isothermal hydrogenation/dehydrogenation kinetic behavior. The information gained by advanced techniques such as transmission electron microscopy and Raman spectroscopy, among others, help us to elucidate that the addition of LixTiO2 to 2LiBH4+MgH2 allows the hydrogen uptake/release via a novel and reversible mechanism.
DOI: 10.6084/m9.figshare.6857774.v1
title: Synthesis and properties of nickel/graphene electrodes for hydrogen generation

description: ABSTRACT The use of nanomaterials, such graphene oxide (GO), as blocks for the synthesis of hybrid materials has been extensively studied in recent years. In this paper a simple and reproducible method for the synthesis of hybrid nickel/graphene electrodes is presented. This method involves the modification of a conventional electroplating nickel bath by incorporating graphene oxide flakes, so the synthesis can be industrially scalable. The synthesized catalyst was structurally and electrochemically characterized. The XRD studies show no appreciable change in the lattice parameter, but a decrease is observed in the relationship between (200)/(111) planes related to an increase in catalyst stability. Raman spectra show the characteristic reduced GO bands on the catalyst matrix. Also, the formation of nickel hydrides in the nickel/graphene catalyst is not observed, unlike the pure nickel electrode. The kinetics of hydrogen evolution reaction (HER) was studied in both, conventional nickel and nickel/graphene catalysts, finding changes in activity. The hybrid catalyst has a higher catalytic activity towards the HER and the presence of GO in the Ni matrix inhibits the nickel hydride formation with the consequent loss of catalytic activity.
DOI: 10.6084/m9.figshare.6857768
title: Thermal stability of Friction-Stir Processed (FSP) magnesium alloys

description: ABSTRACT Superplasticity is defined by an extended plastic deformation previous to fracture, generally at high temperatures. In the mode of fine structures superplasticity, grain boundary sliding is the controlling mechanism. To achieve this fine grained structure it could be used any Severe Plastic Deformation (SPD) process like Friction Stir Processing (FSP). Nevertheless, it must be consider the thermal stability of the microstructure produced, which is related to its capacity to resist heating without experiment abnormal grain growth. The use of magnesium alloys has been promoted in the automotive industry in order to reduce weight of the structures. The aim of this work is to study the thermal stability of the AZ31 friction stir processed microstructure. Sheets of 3 mm thickness were obtained in as cast condition. These sheets were FSProcessed. Samples of AZ31 FSPed were heat treated to 300, 350, 400 and 450 ºC, during 10, 30 and 60 min. These 12 conditions plus the base material were microstructurally characterized. Vickers microhardness profiles were also measured. Grain growth kinetics was analyzed and related with time and temperature.
DOI: 10.6084/m9.figshare.6857768.v1
title: Thermal stability of Friction-Stir Processed (FSP) magnesium alloys

description: ABSTRACT Superplasticity is defined by an extended plastic deformation previous to fracture, generally at high temperatures. In the mode of fine structures superplasticity, grain boundary sliding is the controlling mechanism. To achieve this fine grained structure it could be used any Severe Plastic Deformation (SPD) process like Friction Stir Processing (FSP). Nevertheless, it must be consider the thermal stability of the microstructure produced, which is related to its capacity to resist heating without experiment abnormal grain growth. The use of magnesium alloys has been promoted in the automotive industry in order to reduce weight of the structures. The aim of this work is to study the thermal stability of the AZ31 friction stir processed microstructure. Sheets of 3 mm thickness were obtained in as cast condition. These sheets were FSProcessed. Samples of AZ31 FSPed were heat treated to 300, 350, 400 and 450 ºC, during 10, 30 and 60 min. These 12 conditions plus the base material were microstructurally characterized. Vickers microhardness profiles were also measured. Grain growth kinetics was analyzed and related with time and temperature.
DOI: 10.6084/m9.figshare.6857771.v1
title: Estudio y caracterización del efecto de compuestos con titanio sobre el sistema hidruro Li-B-Mg-H con alta capacidad de almacenamiento de hidrógeno

description: ABSTRACT One of the main constraints for the implementation of hydrogen as energy carrier is the lack of an efficient and safe hydrogen storage system. Hydrogen storage in solid state through hydride compounds formation is a potential alternative to address this problem. In this work, it is studied the effect of different titanium based compounds (TiB2, LixTiO2) on the kinetic behavior of 2LiBH4+MgH2 reactive hydride composite. It is found that nanometric particles of titanates (LixTiO2) noticeably improve the first non-isothermal dehydrogenation behavior of the 2LiBH4+MgH2, reducing the complete H2 release time from 35 h to 2 h. Moreover, the LixTiO2 addition improves the isothermal hydrogenation/dehydrogenation kinetic behavior. The information gained by advanced techniques such as transmission electron microscopy and Raman spectroscopy, among others, help us to elucidate that the addition of LixTiO2 to 2LiBH4+MgH2 allows the hydrogen uptake/release via a novel and reversible mechanism.
DOI: 10.6084/m9.figshare.6857762
title: Microscopía fototérmica para el estudio de transformaciones de fase

description: ABSTRACT A novel system allowing a high spatial resolution mapping of the thermal diffusivity as a function of temperature up to 1800 K is presented. The system is based on a photothermal technique recently developed by the group, consisting in measuring, with a probe laser beam, the curvature induced by local heating with a modulated pump laser. A microscope heating stage was added to perform temperature ramp and soak that can be used for phase transition and thermal diffusivity determinations as functions of temperature. Spatial scans with microscopic resolution can be performed to study phases evolution at constant temperature for in situ thermal treatments and subsequent study of the spatial phase distribution. In this work an example is presented where the signal at a fixed point and constant modulation frequency is collected as a function of the temperature of the sample. A focus correction device was added to compensate for the thermal drift due to the thermal expansion of the system. The lateral displacement was corrected using a cross correlation algorithm and the camera image. This device was used to determine phase transition temperature of a test sample. These capabilities are shown with the determination of the activation energy for the phase transformation glass-crystal of a Fe-B-Si alloy.
DOI: 10.6084/m9.figshare.6857762.v1
title: Microscopía fototérmica para el estudio de transformaciones de fase

description: ABSTRACT A novel system allowing a high spatial resolution mapping of the thermal diffusivity as a function of temperature up to 1800 K is presented. The system is based on a photothermal technique recently developed by the group, consisting in measuring, with a probe laser beam, the curvature induced by local heating with a modulated pump laser. A microscope heating stage was added to perform temperature ramp and soak that can be used for phase transition and thermal diffusivity determinations as functions of temperature. Spatial scans with microscopic resolution can be performed to study phases evolution at constant temperature for in situ thermal treatments and subsequent study of the spatial phase distribution. In this work an example is presented where the signal at a fixed point and constant modulation frequency is collected as a function of the temperature of the sample. A focus correction device was added to compensate for the thermal drift due to the thermal expansion of the system. The lateral displacement was corrected using a cross correlation algorithm and the camera image. This device was used to determine phase transition temperature of a test sample. These capabilities are shown with the determination of the activation energy for the phase transformation glass-crystal of a Fe-B-Si alloy.
DOI: 10.6084/m9.figshare.6857765
title: Characterization of fabrication process of micropores on silicon substrate by electrochemical method

description: ABSTRACT In the present work, the fabrication process of a set of micropores on crystalline silicon wafers manufactured through wet etching technique was studied. The influence of different control factors such as voltage, temperature and braking agent on the specific characteristics of formation was evaluated. An exhaustive analysis of the evolution of electric currents during the fabrication made possible to standardize the process and determine the pore-formation time, essential feature considering the exigent requirements of industry. Finally, it was concluded that optimum conditions for a controlled fabrication of pores correspond to a temperature of 84 ˚C, HCl as a braking agent and voltages of 0,1V, 0,5V and 1V respectively. The above results are of great importance in different fields, such as biology or medicine, in relation to the utility of pores as sensing devices.
DOI: 10.6084/m9.figshare.6857759
title: Checking of the uniformity of results of simultaneous creep testing equipment

description: ABSTRACT The phenomenon of creep occurs in materials that operate under high temperatures and mechanical stresses, causing changes in their structures; such changes are evidenced by a progressive loss of mechanical strength. The characterization of this phenomenon should be performed with appropriate test machines, which are usually dependent on expensive technology patents. The development of these own technologies, is very important to make experimental determinations that require materials. In this paper the description of the design and construction of equipment for simultaneous tensile creep tests, carried out at the Laboratory of Mechanical Engineering Bahia Blanca Regional Faculty of the National Technological University is presented. The system consists of three machines of the same design, which subject the material under test at constant tension and temperature, maintaining the independence of operation of each with the particularity of being controlled by a single acquisition system and software. To compare the results obtained on the same, simultaneous tests under identical conditions materials tension and temperature were performed and were compared to each test curves and characteristic parameters obtained. At the same time a contrast of measurement and control systems was performed, using equipment certified by accredited laboratories. Results indicating the uniformity of operation of the three machines and their concordance with data obtained in the current literature and presented by other authors were obtained.
DOI: 10.6084/m9.figshare.6857765.v1
title: Characterization of fabrication process of micropores on silicon substrate by electrochemical method

description: ABSTRACT In the present work, the fabrication process of a set of micropores on crystalline silicon wafers manufactured through wet etching technique was studied. The influence of different control factors such as voltage, temperature and braking agent on the specific characteristics of formation was evaluated. An exhaustive analysis of the evolution of electric currents during the fabrication made possible to standardize the process and determine the pore-formation time, essential feature considering the exigent requirements of industry. Finally, it was concluded that optimum conditions for a controlled fabrication of pores correspond to a temperature of 84 ˚C, HCl as a braking agent and voltages of 0,1V, 0,5V and 1V respectively. The above results are of great importance in different fields, such as biology or medicine, in relation to the utility of pores as sensing devices.
DOI: 10.6084/m9.figshare.6857756
title: Estimation of local mechanical properties in friction stir welded AA6061-T6 by Small Punch Test (SPT)

description: ABSTRACT Friction Stir Welding (FSW) is a solid state process that has reach a strong technological impact in welding of aluminum alloys. Among its advantages, it may include the ability of joining materials that are difficult to weld by fusion. In welding of heat treatable aluminum alloys, some degradation in metallurgical properties is observed, so welds show lower strength than base metal. Welding parameters define the mechanical properties of the welded joints. Small Punch Tests (SPT) allow the analysis of local properties in weld zones because small specimens are required. In this paper, two batches of samples were prepared with different welding parameters and local mechanical properties were studied by SPT tests. An AA6061-T6 sheet with thickness 3 mm was selected as base metal. Thermal cycle, axial load and another welding parameters were fully recorded. From samples taken from welded coupons, weldments were characterized mechanically and metallurgically by conventional tests for comparison with SPT results. SPT is a valuable tool to estimate local mechanical properties in FSW welds.
DOI: 10.6084/m9.figshare.6857759.v1
title: Checking of the uniformity of results of simultaneous creep testing equipment

description: ABSTRACT The phenomenon of creep occurs in materials that operate under high temperatures and mechanical stresses, causing changes in their structures; such changes are evidenced by a progressive loss of mechanical strength. The characterization of this phenomenon should be performed with appropriate test machines, which are usually dependent on expensive technology patents. The development of these own technologies, is very important to make experimental determinations that require materials. In this paper the description of the design and construction of equipment for simultaneous tensile creep tests, carried out at the Laboratory of Mechanical Engineering Bahia Blanca Regional Faculty of the National Technological University is presented. The system consists of three machines of the same design, which subject the material under test at constant tension and temperature, maintaining the independence of operation of each with the particularity of being controlled by a single acquisition system and software. To compare the results obtained on the same, simultaneous tests under identical conditions materials tension and temperature were performed and were compared to each test curves and characteristic parameters obtained. At the same time a contrast of measurement and control systems was performed, using equipment certified by accredited laboratories. Results indicating the uniformity of operation of the three machines and their concordance with data obtained in the current literature and presented by other authors were obtained.
DOI: 10.6084/m9.figshare.6857753
title: Design and analysis of different models of microfluidic devices evaluated in Enhanced Oil Recovery (EOR) assays

description: ABSTRACT Microfluidic devices are a new platform for Enhanced Oil Recovery (EOR) assays. The application of Colloidad Dispersion Gels (CDG) injection method has been proposed in recent years. However, the mechanism of oil recovery enhancement has not been completely elucidated. Its purpose is to mobilize oil by decreasing the permeability of channeled zones. The success of injection depends on the characteristics of water, the porous medium and the oil. Therefore, a successful injection in a reservoir can be different in another, hence the importance of a methodology for assessment prior to injection. This work applies micro and nanotechnology techniques to develop microfluidic chips used in EOR tests. EOR chips simulate the phenomena that occur in micro-nano scale reservoirs. Experiments analyzed multiphase flows in porous media inside chips. Generally, the first step of the experiments corresponds to fill the microchannels with water and then oil (1 poral volume 1PV). Second, water-injection takes place at constant flow rate until oil recovery ceases. Finally, either polymer or CDG is injected and their behavior is studied by digital image analysis. Results allowed obtaining graphs of oil residual saturation versus time for pore volumes of fluid used in EOR. The optimum configurations of the microchannels showed 80% of residual oil saturation after water injection.