Application of severe plastic deformation (SPD) to different materials usually leads to significa... more Application of severe plastic deformation (SPD) to different materials usually leads to significant grain refinement and accelerated phase transformations. This study reports the occurrence of grain growth in nanocrystalline Al 2 O 3 by SPD processing via high-pressure torsion (HPT) due to a phase transformation from γ with the cubic structure to α with the rhombohedral structure. This transformation was significantly enhanced by pressure and plastic strain and occurred at~650 K below the γ → α transition temperature. The γ phase after HPT processing could be detected only in nanograins or in the nano-sized laths with the (131)γ//(014)α and [001]γ//[100]α coherent orientation relationship.
High-pressure torsion of aluminum with ultrahigh purity (99.9999%) and occurrence of inverse Hall... more High-pressure torsion of aluminum with ultrahigh purity (99.9999%) and occurrence of inverse Hall-Petch relationship, Materials Science & Engineering A,
Excessive CO2 emission from fossil fuel usage has resulted in global warming and environmental cr... more Excessive CO2 emission from fossil fuel usage has resulted in global warming and environmental crises. To solve this problem, the photocatalytic conversion of CO2 to CO or useful components is a new strategy that has received significant attention. The main challenge in this regard is exploring photocatalysts with high efficiency for CO2 photoreduction. Severe plastic deformation (SPD) through the high-pressure torsion (HPT) process has been effectively used in recent years to develop novel active catalysts for CO2 conversion. These active photocatalysts have been designed based on four main strategies: (i) oxygen vacancy and strain engineering, (ii) stabilization of high-pressure phases, (iii) synthesis of defective high-entropy oxides, and (iv) synthesis of low-bandgap high-entropy oxynitrides. These strategies can enhance the photocatalytic efficiency compared with conventional and benchmark photocatalysts by improving CO2 adsorption, increasing light absorbance, aligning the ban...
Severe plastic deformation is known for its potential to obtain non-equilibrium solid solutions o... more Severe plastic deformation is known for its potential to obtain non-equilibrium solid solutions of metals, which under normal conditions are immiscible or have limited solubility. An important role in this process is played by the increased density of defects, which facilitates diffusion in the material during deformation. In particular, recently it was found that the application of ultra-severe plastic deformation can lead to dissolution of Zr atoms in aluminum, while the equilibrium phase diagram of these two metals shows that solid solution of Zr in Al is impossible. In the present work, we use molecular dynamics simulation to calculate the dependence of the lattice parameter of the Al-Zr solid solution as a function of the Zr concentration in the range from one to four atomic percent. It is found that our simulation results are in a reasonably good agreement with the experimental measurements of lattice parameter of Al-Zr solid solution obtained by ultra-severe plastic deformation.
Electrocatalysis using renewable energy sources provides a clean technology to produce hydrogen f... more Electrocatalysis using renewable energy sources provides a clean technology to produce hydrogen from water. Titanium oxide is considered as a potential electrocatalyst not only for hydrogen production but also for CO<sub>2</sub> conversion. In this study, to enhance the cathodic electrocatalytic activity of TiO<sub>2</sub>, the phase composition on TiO<sub>2</sub> surface is modified by inclusion of high-pressure TiO<sub>2</sub>-II phase using high-pressure torsion (HPT) straining. Detailed spectroscopic studies revealed that the energy band gap is reduced and the valence band energy increased with increasing the TiO<sub>2</sub>-II fraction. The highest electrocatalytic activity for hydrogen production was achieved on an anatase-rich nanocomposite containing TiO<sub>2</sub>-II nanograins. The first application of high-pressure TiO<sub>2</sub>-II phase for electrocatalysis confirm that the inclusion o...
A continuous high-pressure torsion (CHPT) developed recently was applied to high purity aluminum ... more A continuous high-pressure torsion (CHPT) developed recently was applied to high purity aluminum (99.99%) and an Al-3%Mg-0.2%Sc alloy. It is shown that CHPT can be used for straining under high pressures and producing ultrafine grained microstructure as the conventional high-pressure torsion using disc and ring samples. Furthermore, CHPT provides an opportunity to use sheets of the materials in a continuous way which is promising for industrial applications. Tensile tests show that the Al-3%Mg-0.2%Sc alloy after processing with CHPT is superplastic at 573 K.
Visible light active Bismuth doped NaTaO 3 powders were synthesized by the conventional solid sta... more Visible light active Bismuth doped NaTaO 3 powders were synthesized by the conventional solid state route for different Bi concentrations (2.5%, 5.0%, and 7.5% by moles). The optical properties of the doped samples were tuned by changing the molar ratio of Na and Ta in the initial reactants. The doped samples prepared with Na/Ta ratio close to unity (1.01e1.03) resulted in the highest band gap narrowing compared to the other synthesis conditions. It was shown that the photocatalytic hydrogen evolution occurred from these samples under the visible light irradiation (l > 390 nm) after loading of appropriate amount of platinum cocatalyst. The other synthesis conditions (Na/Ta ¼ 1/1Àx; x ¼ 0.025, 0.05, 0.075 and Ta/Na ¼ 1/ 1Àx; x ¼ 0.025, 0.05, 0.075; x is bismuth content) were not useful for the photocatalytic hydrogen evolution. The structural characterization suggested that the samples prepared with Na/Ta ratio close to unity, contain Bi ions located at both Na and Ta sites in the lattice. The MotteSchottky plots revealed that the flat band potential of the pristine NaTaO 3 is highly negative to the H 2 /H 2 O reduction potential (À1.19 eV vs. SCE, pH ¼ 7) and for all Bi doped NaTaO 3 samples, the flat band potential was sufficient for the hydrogen generation.
Au-nanoparticle-decorated ZnS nanoarchitectures were fabricated by a simple hydrothermal approach... more Au-nanoparticle-decorated ZnS nanoarchitectures were fabricated by a simple hydrothermal approach combined with a deposition-precipitation method. After the deposition-precipitation process, 5-nm Au nanoparticles were homogeneously dispersed on the ZnS surface. In addition, the band gap of ZnS was also narrowed by the incorporation of a small amount of Au(I) ions. The photocatalytic hydrogen production activities of all the samples were evaluated by using Na 2 S and Na 2 SO 3 as sacrificial reagents in water under a 350 W xenon arc lamp. The results show that the photocatalytic hydrogen production rate of ZnS nanoarchitectures can be significantly improved by loading Au cocatalysts and reaches an optimal value (3306 μmol h −1 g −1) at the Au content of 4% wt. Although strong surface plasmon resonance (SPR) absorption of the Au nanoparticles was found in the Au-loaded samples, all of these samples exhibit no activities in the visible light region (λ > 420 nm). On the basis of this Au/ZnS system, the possible roles of Au deposition in improving the photocatalytic hydrogen production activity, especially the necessary condition for SPR effect of metal nanostructures to function in the visible-light photocatalysis, are critically discussed.
Abstract In this work, a melt-spun amorphous Fe73.5Si13.5B9Cu1Nb3 alloy is subjected to high-pres... more Abstract In this work, a melt-spun amorphous Fe73.5Si13.5B9Cu1Nb3 alloy is subjected to high-pressure torsion (HPT) treatment under 6 GPa in order to enhance the alkaline hydrogen evolution reaction (HER) performance. Different HPT turns, including 1, 2, 5 and 10, are selected and the samples are marked as HPT-1N, HPT-2N, HPT-5N and HPT-10 N, respectively. The HPT treatment can lead to a significant structural change such as partial crystallization and defect generation on the Fe-based amorphous alloy with a considerable increase in the HER electrocatalytic activity. The HPT-5N sample shows the best catalytic performance, with an overpotential of only 174 mV at 10 mA cm−2 current density in 1 M KOH, which is 244 mV lower than that of the melt-spun alloy at the same condition. Moreover, it was established that the HPT-treated amorphous alloy shows good stability during the HER cycling process.
Abstract Inconel 718 was successfully processed by multi-pass high-pressure sliding (MP-HPS) for ... more Abstract Inconel 718 was successfully processed by multi-pass high-pressure sliding (MP-HPS) for production of ultrafine-grained structures in rods with upsized dimensions. An ultrafine-grained (UFG) structure with an average grain size of ~ 140 nm was developed through rotation of 45°. Tensile testing at 1073 K with an initial strain rate of 2x10-2 s−1 led to superplastic elongations more than 400%. A relation is established between hardness and elongation to failure so that it should be possible to predict the advent of superplasticity only from the hardness measurement.
The influence of the nanocrystalline structure produced by severe plastic deformation (SPD) on th... more The influence of the nanocrystalline structure produced by severe plastic deformation (SPD) on the corrosion behavior of CoCrFeMnNi alloys with Cr contents ranging from 0 to 20 at.% was investigated in aqueous 0.5 M H2SO4 and 3.5% NaCl solutions. The resistance to general corrosion and pitting became higher in both the solutions, with higher passivation capability observed with increasing Cr content, and it is believed that the high corrosion resistance of CoCrFeMnNi alloys can be attributed to the incorporation of the Cr element. However, the impact of the nanocrystalline structure produced by SPD on the corrosion behavior was negligibly small. This is inconsistent with reports on nanocrystalline binary Fe–Cr alloys and stainless steels processed by SPD, where grain refinement by SPD results in higher corrosion resistance. The small change in the corrosion behavior with respect to grain refinement is discussed, based on the passivation process of Fe–Cr alloys and on the influence o...
This special issue is edited to summarize recent research activity associated with severe plastic... more This special issue is edited to summarize recent research activity associated with severe plastic deformation (SPD). It is well known that significant refinement of microstructures is achieved in metallic materials using the SPD processes such as Equal-Channel Angular Pressing (ECAP), Accumulative Roll Bonding (ARB) and High-Pressure Torsion (HPT). High strength is attained without losing much of the ductility for the SPD-processed materials. Superplasticity may also appear because the grain size is reduced to the submicrometer range using the SPD processes. This special issue includes research results on such subjects. In this special issue, emphasis is placed on the role of lattice defects. It is well established that plastic deformation introduces varieties of lattice defects such as vacancies, dislocations and grain boundaries. Population of these defects increases as the magnitude of the plastic deformation is larger. However, it is not known what happens if an enormous amount ...
Abstract Mechanical properties of high-entropy alloys (HEAs) have received significant attention,... more Abstract Mechanical properties of high-entropy alloys (HEAs) have received significant attention, while there are still attempts to find new strategies to further improve their properties. In this study, to produce an ultrahard HEA, an FCC carbide was introduced in a BCC-based AlTiFeCoNi alloy by the assistance of CALPHAD thermodynamic calculations. The alloy was synthesized by arc melting and processed by severe plastic deformation via the high-pressure torsion (HPT) method to generate defects. The material showed nanograin formation, dislocation accumulation, carbide fragmentation, L21 → BCC ordered-to-disordered phase transformation, and accordingly an ultrahigh hardness of 950 Hv after HPT processing.
A new Fe78Si9B13 nanoglass covered by in situ formed FeOOH as an OER catalyst for water splitting... more A new Fe78Si9B13 nanoglass covered by in situ formed FeOOH as an OER catalyst for water splitting. Overpotential is only 240 mV at 10 mA cm−1 in 1 M KOH, and the Tafel slope is 42 mV dec−1.
Abstract High-entropy alloys (HEAs), a novel type of materials with high configurational entropy,... more Abstract High-entropy alloys (HEAs), a novel type of materials with high configurational entropy, have aroused a huge interest due to a promising range of functional properties including biocompatibility. In this study, the high-pressure torsion (HPT) method was implemented as a mechanical alloying route to synthesize biocompatible nanostructured HEAs with the bcc structure. An equiatomic quinary TiNbZrTaHf HEA was successfully synthesized via the HPT method and its characteristics were compared with the binary TiNb, ternary TiNbZr and quaternary TiNbZrTa alloys to have an insight into the effect of configurational entropy on microstructure and mechanical properties of these biomaterials. The grain size decreased, the strain-rate sensitivity reduced, and the hardness increased with increasing the number of principal elements from 2 to 3, but these variations became less significant with further increase in the configurational entropy. Small nanograins, solid solution hardening, dislocation activity together with high entropy effect in the HEA led to a high hardness of 564 Hv and a moderate elastic modulus of 79 GPa which are promising mechanical properties for biomedical applications.
Meridional overturning circulation (MOC) is an important aspect of Earth's climate due to its ass... more Meridional overturning circulation (MOC) is an important aspect of Earth's climate due to its associated heat flux and influence on atmospheric CO 2 (see for a review). Salinity is central to understanding the MOC as it influences circulation via density gradients and is used to characterize water-mass distributions. In the modern Atlantic, northern sourced deep waters are saltier than southern, with separate northern and southern MOC cells . The northern cell of Atlantic MOC extends south of the equator, resulting in northward heat transport across the equator from the Southern Hemisphere . The distribution and composition of Atlantic northern and southern sourced deep water-masses influence the global carbon inventory and can be constrained for the past ocean through historical reconstructions of water-mass geometry . Global climate has cycled between major glacial and interglacial modes over the past 33 Mya , with changes in atmospheric CO 2 concentrations highly correlated to climate variations over the past 730 ka . The Last Glacial Maximum (LGM), 19-26 ka, with atmospheric CO 2 concentrations 30% lower than preindustrial levels, is the most recent example in the geologic record of atmospheric CO 2 change similar in
Materials Science and Engineering: R: Reports, 2021
We record a new ichnosite bearing dinosaur tracks from the mid-Cretaceous (Aptian? -Cenomanian) o... more We record a new ichnosite bearing dinosaur tracks from the mid-Cretaceous (Aptian? -Cenomanian) of Brazil. The Fazenda dos Pingos ichnosite is situated within a sandstone pavement of the Açu Formation (Açu 3 unit) from the Potiguar Basin in the State of Rio Grande do Norte. This is a small ichnofauna, with only a few individual isolated tracks. One specimen is unequivocally attributed to a large sauropod and another to an ornithopod. Two other specimens represent poorly preserved tracks assigned to sauropods. This is the fi rst record of dinosaur tracks from the Potiguar Basin and from the Rio Grande do Norte State.
Application of severe plastic deformation (SPD) to different materials usually leads to significa... more Application of severe plastic deformation (SPD) to different materials usually leads to significant grain refinement and accelerated phase transformations. This study reports the occurrence of grain growth in nanocrystalline Al 2 O 3 by SPD processing via high-pressure torsion (HPT) due to a phase transformation from γ with the cubic structure to α with the rhombohedral structure. This transformation was significantly enhanced by pressure and plastic strain and occurred at~650 K below the γ → α transition temperature. The γ phase after HPT processing could be detected only in nanograins or in the nano-sized laths with the (131)γ//(014)α and [001]γ//[100]α coherent orientation relationship.
High-pressure torsion of aluminum with ultrahigh purity (99.9999%) and occurrence of inverse Hall... more High-pressure torsion of aluminum with ultrahigh purity (99.9999%) and occurrence of inverse Hall-Petch relationship, Materials Science & Engineering A,
Excessive CO2 emission from fossil fuel usage has resulted in global warming and environmental cr... more Excessive CO2 emission from fossil fuel usage has resulted in global warming and environmental crises. To solve this problem, the photocatalytic conversion of CO2 to CO or useful components is a new strategy that has received significant attention. The main challenge in this regard is exploring photocatalysts with high efficiency for CO2 photoreduction. Severe plastic deformation (SPD) through the high-pressure torsion (HPT) process has been effectively used in recent years to develop novel active catalysts for CO2 conversion. These active photocatalysts have been designed based on four main strategies: (i) oxygen vacancy and strain engineering, (ii) stabilization of high-pressure phases, (iii) synthesis of defective high-entropy oxides, and (iv) synthesis of low-bandgap high-entropy oxynitrides. These strategies can enhance the photocatalytic efficiency compared with conventional and benchmark photocatalysts by improving CO2 adsorption, increasing light absorbance, aligning the ban...
Severe plastic deformation is known for its potential to obtain non-equilibrium solid solutions o... more Severe plastic deformation is known for its potential to obtain non-equilibrium solid solutions of metals, which under normal conditions are immiscible or have limited solubility. An important role in this process is played by the increased density of defects, which facilitates diffusion in the material during deformation. In particular, recently it was found that the application of ultra-severe plastic deformation can lead to dissolution of Zr atoms in aluminum, while the equilibrium phase diagram of these two metals shows that solid solution of Zr in Al is impossible. In the present work, we use molecular dynamics simulation to calculate the dependence of the lattice parameter of the Al-Zr solid solution as a function of the Zr concentration in the range from one to four atomic percent. It is found that our simulation results are in a reasonably good agreement with the experimental measurements of lattice parameter of Al-Zr solid solution obtained by ultra-severe plastic deformation.
Electrocatalysis using renewable energy sources provides a clean technology to produce hydrogen f... more Electrocatalysis using renewable energy sources provides a clean technology to produce hydrogen from water. Titanium oxide is considered as a potential electrocatalyst not only for hydrogen production but also for CO<sub>2</sub> conversion. In this study, to enhance the cathodic electrocatalytic activity of TiO<sub>2</sub>, the phase composition on TiO<sub>2</sub> surface is modified by inclusion of high-pressure TiO<sub>2</sub>-II phase using high-pressure torsion (HPT) straining. Detailed spectroscopic studies revealed that the energy band gap is reduced and the valence band energy increased with increasing the TiO<sub>2</sub>-II fraction. The highest electrocatalytic activity for hydrogen production was achieved on an anatase-rich nanocomposite containing TiO<sub>2</sub>-II nanograins. The first application of high-pressure TiO<sub>2</sub>-II phase for electrocatalysis confirm that the inclusion o...
A continuous high-pressure torsion (CHPT) developed recently was applied to high purity aluminum ... more A continuous high-pressure torsion (CHPT) developed recently was applied to high purity aluminum (99.99%) and an Al-3%Mg-0.2%Sc alloy. It is shown that CHPT can be used for straining under high pressures and producing ultrafine grained microstructure as the conventional high-pressure torsion using disc and ring samples. Furthermore, CHPT provides an opportunity to use sheets of the materials in a continuous way which is promising for industrial applications. Tensile tests show that the Al-3%Mg-0.2%Sc alloy after processing with CHPT is superplastic at 573 K.
Visible light active Bismuth doped NaTaO 3 powders were synthesized by the conventional solid sta... more Visible light active Bismuth doped NaTaO 3 powders were synthesized by the conventional solid state route for different Bi concentrations (2.5%, 5.0%, and 7.5% by moles). The optical properties of the doped samples were tuned by changing the molar ratio of Na and Ta in the initial reactants. The doped samples prepared with Na/Ta ratio close to unity (1.01e1.03) resulted in the highest band gap narrowing compared to the other synthesis conditions. It was shown that the photocatalytic hydrogen evolution occurred from these samples under the visible light irradiation (l > 390 nm) after loading of appropriate amount of platinum cocatalyst. The other synthesis conditions (Na/Ta ¼ 1/1Àx; x ¼ 0.025, 0.05, 0.075 and Ta/Na ¼ 1/ 1Àx; x ¼ 0.025, 0.05, 0.075; x is bismuth content) were not useful for the photocatalytic hydrogen evolution. The structural characterization suggested that the samples prepared with Na/Ta ratio close to unity, contain Bi ions located at both Na and Ta sites in the lattice. The MotteSchottky plots revealed that the flat band potential of the pristine NaTaO 3 is highly negative to the H 2 /H 2 O reduction potential (À1.19 eV vs. SCE, pH ¼ 7) and for all Bi doped NaTaO 3 samples, the flat band potential was sufficient for the hydrogen generation.
Au-nanoparticle-decorated ZnS nanoarchitectures were fabricated by a simple hydrothermal approach... more Au-nanoparticle-decorated ZnS nanoarchitectures were fabricated by a simple hydrothermal approach combined with a deposition-precipitation method. After the deposition-precipitation process, 5-nm Au nanoparticles were homogeneously dispersed on the ZnS surface. In addition, the band gap of ZnS was also narrowed by the incorporation of a small amount of Au(I) ions. The photocatalytic hydrogen production activities of all the samples were evaluated by using Na 2 S and Na 2 SO 3 as sacrificial reagents in water under a 350 W xenon arc lamp. The results show that the photocatalytic hydrogen production rate of ZnS nanoarchitectures can be significantly improved by loading Au cocatalysts and reaches an optimal value (3306 μmol h −1 g −1) at the Au content of 4% wt. Although strong surface plasmon resonance (SPR) absorption of the Au nanoparticles was found in the Au-loaded samples, all of these samples exhibit no activities in the visible light region (λ > 420 nm). On the basis of this Au/ZnS system, the possible roles of Au deposition in improving the photocatalytic hydrogen production activity, especially the necessary condition for SPR effect of metal nanostructures to function in the visible-light photocatalysis, are critically discussed.
Abstract In this work, a melt-spun amorphous Fe73.5Si13.5B9Cu1Nb3 alloy is subjected to high-pres... more Abstract In this work, a melt-spun amorphous Fe73.5Si13.5B9Cu1Nb3 alloy is subjected to high-pressure torsion (HPT) treatment under 6 GPa in order to enhance the alkaline hydrogen evolution reaction (HER) performance. Different HPT turns, including 1, 2, 5 and 10, are selected and the samples are marked as HPT-1N, HPT-2N, HPT-5N and HPT-10 N, respectively. The HPT treatment can lead to a significant structural change such as partial crystallization and defect generation on the Fe-based amorphous alloy with a considerable increase in the HER electrocatalytic activity. The HPT-5N sample shows the best catalytic performance, with an overpotential of only 174 mV at 10 mA cm−2 current density in 1 M KOH, which is 244 mV lower than that of the melt-spun alloy at the same condition. Moreover, it was established that the HPT-treated amorphous alloy shows good stability during the HER cycling process.
Abstract Inconel 718 was successfully processed by multi-pass high-pressure sliding (MP-HPS) for ... more Abstract Inconel 718 was successfully processed by multi-pass high-pressure sliding (MP-HPS) for production of ultrafine-grained structures in rods with upsized dimensions. An ultrafine-grained (UFG) structure with an average grain size of ~ 140 nm was developed through rotation of 45°. Tensile testing at 1073 K with an initial strain rate of 2x10-2 s−1 led to superplastic elongations more than 400%. A relation is established between hardness and elongation to failure so that it should be possible to predict the advent of superplasticity only from the hardness measurement.
The influence of the nanocrystalline structure produced by severe plastic deformation (SPD) on th... more The influence of the nanocrystalline structure produced by severe plastic deformation (SPD) on the corrosion behavior of CoCrFeMnNi alloys with Cr contents ranging from 0 to 20 at.% was investigated in aqueous 0.5 M H2SO4 and 3.5% NaCl solutions. The resistance to general corrosion and pitting became higher in both the solutions, with higher passivation capability observed with increasing Cr content, and it is believed that the high corrosion resistance of CoCrFeMnNi alloys can be attributed to the incorporation of the Cr element. However, the impact of the nanocrystalline structure produced by SPD on the corrosion behavior was negligibly small. This is inconsistent with reports on nanocrystalline binary Fe–Cr alloys and stainless steels processed by SPD, where grain refinement by SPD results in higher corrosion resistance. The small change in the corrosion behavior with respect to grain refinement is discussed, based on the passivation process of Fe–Cr alloys and on the influence o...
This special issue is edited to summarize recent research activity associated with severe plastic... more This special issue is edited to summarize recent research activity associated with severe plastic deformation (SPD). It is well known that significant refinement of microstructures is achieved in metallic materials using the SPD processes such as Equal-Channel Angular Pressing (ECAP), Accumulative Roll Bonding (ARB) and High-Pressure Torsion (HPT). High strength is attained without losing much of the ductility for the SPD-processed materials. Superplasticity may also appear because the grain size is reduced to the submicrometer range using the SPD processes. This special issue includes research results on such subjects. In this special issue, emphasis is placed on the role of lattice defects. It is well established that plastic deformation introduces varieties of lattice defects such as vacancies, dislocations and grain boundaries. Population of these defects increases as the magnitude of the plastic deformation is larger. However, it is not known what happens if an enormous amount ...
Abstract Mechanical properties of high-entropy alloys (HEAs) have received significant attention,... more Abstract Mechanical properties of high-entropy alloys (HEAs) have received significant attention, while there are still attempts to find new strategies to further improve their properties. In this study, to produce an ultrahard HEA, an FCC carbide was introduced in a BCC-based AlTiFeCoNi alloy by the assistance of CALPHAD thermodynamic calculations. The alloy was synthesized by arc melting and processed by severe plastic deformation via the high-pressure torsion (HPT) method to generate defects. The material showed nanograin formation, dislocation accumulation, carbide fragmentation, L21 → BCC ordered-to-disordered phase transformation, and accordingly an ultrahigh hardness of 950 Hv after HPT processing.
A new Fe78Si9B13 nanoglass covered by in situ formed FeOOH as an OER catalyst for water splitting... more A new Fe78Si9B13 nanoglass covered by in situ formed FeOOH as an OER catalyst for water splitting. Overpotential is only 240 mV at 10 mA cm−1 in 1 M KOH, and the Tafel slope is 42 mV dec−1.
Abstract High-entropy alloys (HEAs), a novel type of materials with high configurational entropy,... more Abstract High-entropy alloys (HEAs), a novel type of materials with high configurational entropy, have aroused a huge interest due to a promising range of functional properties including biocompatibility. In this study, the high-pressure torsion (HPT) method was implemented as a mechanical alloying route to synthesize biocompatible nanostructured HEAs with the bcc structure. An equiatomic quinary TiNbZrTaHf HEA was successfully synthesized via the HPT method and its characteristics were compared with the binary TiNb, ternary TiNbZr and quaternary TiNbZrTa alloys to have an insight into the effect of configurational entropy on microstructure and mechanical properties of these biomaterials. The grain size decreased, the strain-rate sensitivity reduced, and the hardness increased with increasing the number of principal elements from 2 to 3, but these variations became less significant with further increase in the configurational entropy. Small nanograins, solid solution hardening, dislocation activity together with high entropy effect in the HEA led to a high hardness of 564 Hv and a moderate elastic modulus of 79 GPa which are promising mechanical properties for biomedical applications.
Meridional overturning circulation (MOC) is an important aspect of Earth's climate due to its ass... more Meridional overturning circulation (MOC) is an important aspect of Earth's climate due to its associated heat flux and influence on atmospheric CO 2 (see for a review). Salinity is central to understanding the MOC as it influences circulation via density gradients and is used to characterize water-mass distributions. In the modern Atlantic, northern sourced deep waters are saltier than southern, with separate northern and southern MOC cells . The northern cell of Atlantic MOC extends south of the equator, resulting in northward heat transport across the equator from the Southern Hemisphere . The distribution and composition of Atlantic northern and southern sourced deep water-masses influence the global carbon inventory and can be constrained for the past ocean through historical reconstructions of water-mass geometry . Global climate has cycled between major glacial and interglacial modes over the past 33 Mya , with changes in atmospheric CO 2 concentrations highly correlated to climate variations over the past 730 ka . The Last Glacial Maximum (LGM), 19-26 ka, with atmospheric CO 2 concentrations 30% lower than preindustrial levels, is the most recent example in the geologic record of atmospheric CO 2 change similar in
Materials Science and Engineering: R: Reports, 2021
We record a new ichnosite bearing dinosaur tracks from the mid-Cretaceous (Aptian? -Cenomanian) o... more We record a new ichnosite bearing dinosaur tracks from the mid-Cretaceous (Aptian? -Cenomanian) of Brazil. The Fazenda dos Pingos ichnosite is situated within a sandstone pavement of the Açu Formation (Açu 3 unit) from the Potiguar Basin in the State of Rio Grande do Norte. This is a small ichnofauna, with only a few individual isolated tracks. One specimen is unequivocally attributed to a large sauropod and another to an ornithopod. Two other specimens represent poorly preserved tracks assigned to sauropods. This is the fi rst record of dinosaur tracks from the Potiguar Basin and from the Rio Grande do Norte State.
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Papers by Kaveh Edalati