The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Irene J Beyerlein - One of the best experts on this subject based on the ideXlab platform.
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generalized stacking fault energies and peierls stresses in Refractory body centered cubic Metals from machine learning based interatomic potentials
Computational Materials Science, 2021Co-Authors: Xiaowang Wang, Wurong Jian, Irene J BeyerleinAbstract:Abstract The generalized stacking fault energies (GSFE) and Peierls stresses are strongly related to the mechanical properties of Refractory Metals. In this work, the GSFE curves and Peierls stresses of screw and edge dislocations in four body-centered cubic Refractory Metals (Mo, Nb, Ta, and W) on the {110}, {112}, and {123} slip planes are calculated using molecular statics simulations. A recently developed machine learning (ML)-based interatomic potential, called the spectral neighbor analysis potential (SNAP), is employed in all simulations. The computed GSFE curves achieve reasonable agreement with those from ab initio calculations and predict the asymmetry with respect to sense of glide direction on the {112} and {123} planes better than non-ML interatomic potentials. In general, SNAP provides screw dislocation Peierls stresses close to those of density functional theory, closer than those achieved by non-ML potentials. The screw dislocation Peierls stress values confirm slip symmetry on the {110} plane and exhibit pronounced slip asymmetry on the {112} and {123} planes. For all Metals, the edge dislocation Peierls stress are the lowest on the {110} plane and the highest on the {112} plane. For screw dislocations, glide on either the {110} or the {123} plane is the easiest.
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frank read source operation in six body centered cubic Refractory Metals
Journal of The Mechanics and Physics of Solids, 2020Co-Authors: Lauren Smith, Irene J BeyerleinAbstract:Abstract The Frank-Read (FR) source is a well-known intragranular dislocation source that plays an important role in size-dependent dislocation multiplication in metallic crystals. In this work, we extend a phase-field dislocation dynamics (PFDD) technique to study FR source operation on the {110}, {112}, and {123} slip planes in body-centered cubic (BCC) crystals. Here, the periodic lattice potentials for shearing across these planes used in PFDD simulations are provided by density functional theory (DFT) calculations for six BCC Refractory Metals, Cr, Mo, Nb, Ta, V, and W. The DFT calculations show that the group 6 elements (Cr, Mo, and W) have higher generalized stacking fault energies than the group 5 elements (Nb, Ta, and V). With PFDD, we focus on the effects of the GSFE curve shape, initial character angle, slip plane crystallography, and elastic anisotropy (measured by the Zener ratio, Ac) on the critical stresses to activate the FR source. For the same FR source of any character angle in the same metal, the critical stress on the {123} plane is lower than those on the {110} and {112} planes. It is also shown that elastic anisotropy decreases the critical stress when Ac 1. We also find that in both Cr and Nb, which possess the lowest values of Ac among the six Metals, elastic anisotropy causes the critical stress on {110} planes to achieve a local maximum for the mixed 45∘ oriented FR source.
S. Kumar - One of the best experts on this subject based on the ideXlab platform.
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Influence of coating defects on the corrosion behavior of cold sprayed Refractory Metals
Applied Surface Science, 2017Co-Authors: S. KumarAbstract:Abstract The defects in the cold sprayed coatings are critical in the case of corrosion performances of the coatings in aggressive conditions. To understand the influence of coating defects on corrosion, immersion tests have been carried out in HF solution for the cold sprayed and heat treated Titanium, Tantalum and Niobium coatings. Long duration immersion tests reveal inhomogeneous weight losses of the samples prepared at different heat treatment conditions. The weight loss for different coatings has been well corroborated with the coating defects and microstructures. Chemical and micro structural analysis elucidates the reason behind the inhomogeneous performance of different type of cold sprayed coatings in corrosion medium. In the case of cold sprayed titanium, formation of stable oxide along the inter-splat boundary hinders the aggressive attack of the corrosion medium which is not so in other cases.
Takehiko Ishikawa - One of the best experts on this subject based on the ideXlab platform.
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viscosity measurements of molten Refractory Metals using an electrostatic levitator
Measurement Science and Technology, 2012Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Junpei T Okada, Yuki WatanabeAbstract:Viscosities of several Refractory Metals (titanium, nickel, zirconium, niobium, ruthenium, rhodium, hafnium, iridium and platinum) and terbium have been measured by the oscillation drop method with an improved procedure. The measured data were less scattered than our previous measurements. Viscosities at their melting temperatures showed good agreement with literature values and some predicted values.
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thermophysical properties of molten Refractory Metals measured by an electrostatic levitator
Journal of Electronic Materials, 2005Co-Authors: Takehiko Ishikawa, Paulfrancois ParadisAbstract:Thermophysical property measurements of molten Refractory Metals, which are very difficult and hardly conducted with conventional methods due to their high melting temperature and risk of reaction with container walls, have been conducted using noncontact diagnostic techniques in an electrostatic levitator. This paper first briefly summarizes the procedures and methods adopted by the Japan Aerospace Exploration Agency to enable the measurements of density, surface tension, and viscosity on molten Refractory Metals. Typical data of superheated and undercooled liquids that would have been impossible to obtain without the use of these techniques are then reported. Specifically, density, surface tension, and viscosity of Ti, Zr, Nb, Mo, Ta, and W were successfully measured over a wide temperature range, including the undercooled region.
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non contact thermophysical property measurements of Refractory Metals using an electrostatic levitator
Measurement Science and Technology, 2005Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Toshio Itami, Shinichi YodaAbstract:The electrostatic levitation system, including its history and development, and techniques for non-contact thermophysical property measurements (density, ratio of isobaric heat capacity to hemispherical total emissivity, surface tension and viscosity) are reviewed. Thermophysical properties of Refractory Metals whose melting temperatures are over 2000 K have been measured with an electrostatic levitator. The experimental results for vanadium, zirconium, niobium, molybdenum, rhodium, ruthenium, iridium, tantalum and rhenium are presented. Comparison between theoretical calculations based on hard sphere model and measured data, as well as the necessity of microgravity conditions for this research is also discussed.
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thermophysical properties of liquid Refractory Metals comparison between hard sphere model calculation and electrostatic levitation measurements
Journal of Chemical Physics, 2003Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Toshio Itami, Shinichi YodaAbstract:Thermophysical properties of molten Refractory Metals (titanium, zirconium, hafnium, and niobium) have been measured using a containerless method. Using an in-house developed electrostatic levitator, the density, the heat capacity, the entropy, the surface tension, and the viscosity of liquid phases have been measured over a wide temperature range. The measured data showed good agreement with theoretical calculations based on the hard sphere model.
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new sample levitation initiation and imaging techniques for the processing of Refractory Metals with an electrostatic levitator furnace
Review of Scientific Instruments, 2001Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Shinichi YodaAbstract:Two new methods that substantially ease the processing and study of Refractory Metals, when an electrostatic levitation furnace is used, are reported. The first technique is concerned with preheating the sample on a pedestal, prior to launch, to a temperature (∼1500 K) at which thermionic emission dominates all other charging/discharging mechanisms that may be going on simultaneously. Launched into levitation at that temperature, the sample can be quickly heated to its molten state without encountering further charge loss problems. This procedure thus shortens substantially the time it takes to bring the samples to their final high temperature states at which their thermophysical properties can be measured. This technique can be applied to most materials whose melting temperatures are higher than their thermionic temperatures. The second technique described is an ultraviolet-based sample imaging configuration. Due to the excellent sample–background contrast it continuously provides during all phases of pr...
Minoru Takahashi - One of the best experts on this subject based on the ideXlab platform.
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corrosion investigations of al fe coated steels high cr steels Refractory Metals and ceramics in lead alloys at 700 c
Journal of Nuclear Materials, 2010Co-Authors: Abu Khalid Rivai, Minoru TakahashiAbstract:Abstract Corrosion tests of several types materials were carried out in lead–bismuth eutectic and lead at 700 °C. Al–Fe-coated SUS316FR, and high Cr steels SUS430, Recloy10 and NTK04L were tested in molten lead–bismuth and Al–Fe-coated STBA26, high Cr steel STBA26, Refractory Metals tungsten and molybdenum and ceramics SiC and Ti 3 SiC 2 were tested in molten lead. Oxygen concentrations were 5 × 10 −6 and 4.5 × 10 −7 wt.% for the molten lead–bismuth and lead, respectively. The unbalanced magnetron sputtering (UBMS) technique was adopted for the coating with targets of Al and SUS304. The results showed that a very thin oxide layer was formed on the coating layer and protected the material from corrosion attack lead alloys. On the other hand, penetration attack of lead alloys into the base of the high Cr steels was observed. The Refractory Metals and the ceramics exhibit high corrosion resistance to high temperature lead at 700 °C.
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compatibility of surface coated steels Refractory Metals and ceramics to high temperature lead bismuth eutectic
Progress in Nuclear Energy, 2008Co-Authors: Abu Khalid Rivai, Minoru TakahashiAbstract:Compatibility of cladding material with lead-bismuth eutectic at temperature higher than 650 °C is one of the most crucial issues for feasibility of lead-bismuth-cooled fast reactors with cycle efficiency as high as 40%. In order to search for corrosion-resistant materials with lead-bismuth eutectic at temperature higher than 650 °C, surface-coated steels, some Refractory Metals and various ceramics were tested by means of stirred-type corrosion test. Lead-bismuth was heated up to 700 °C electrically in an alumina crucible, and oxygen concentration in the lead-bismuth was adequately controlled by injection of argon, steam and hydrogen gas mixture into the lead-bismuth. Specimens of aluminum-iron-alloy-surface-coated steels, Refractory Metals and ceramics including SiC/SiC composites were immersed in the stirred lead-bismuth for 1000 h. It was found that the surface-coated steels showed good compatibility with the lead-bismuth due to formation of a thin and stable protection layer on the surfaces. Tungsten and molybdenum exhibited high corrosion resistance. On the other hand, niobium is not a reliable material for the high temperature LBE. SiC and Ti 3 SiC 2 also exhibited high corrosion resistance. On the other hand, the physical performance of the SiC/SiC composite must be improved especially by minimizing the porosity.
Paulfrancois Paradis - One of the best experts on this subject based on the ideXlab platform.
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viscosity measurements of molten Refractory Metals using an electrostatic levitator
Measurement Science and Technology, 2012Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Junpei T Okada, Yuki WatanabeAbstract:Viscosities of several Refractory Metals (titanium, nickel, zirconium, niobium, ruthenium, rhodium, hafnium, iridium and platinum) and terbium have been measured by the oscillation drop method with an improved procedure. The measured data were less scattered than our previous measurements. Viscosities at their melting temperatures showed good agreement with literature values and some predicted values.
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thermophysical properties of molten Refractory Metals measured by an electrostatic levitator
Journal of Electronic Materials, 2005Co-Authors: Takehiko Ishikawa, Paulfrancois ParadisAbstract:Thermophysical property measurements of molten Refractory Metals, which are very difficult and hardly conducted with conventional methods due to their high melting temperature and risk of reaction with container walls, have been conducted using noncontact diagnostic techniques in an electrostatic levitator. This paper first briefly summarizes the procedures and methods adopted by the Japan Aerospace Exploration Agency to enable the measurements of density, surface tension, and viscosity on molten Refractory Metals. Typical data of superheated and undercooled liquids that would have been impossible to obtain without the use of these techniques are then reported. Specifically, density, surface tension, and viscosity of Ti, Zr, Nb, Mo, Ta, and W were successfully measured over a wide temperature range, including the undercooled region.
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non contact thermophysical property measurements of Refractory Metals using an electrostatic levitator
Measurement Science and Technology, 2005Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Toshio Itami, Shinichi YodaAbstract:The electrostatic levitation system, including its history and development, and techniques for non-contact thermophysical property measurements (density, ratio of isobaric heat capacity to hemispherical total emissivity, surface tension and viscosity) are reviewed. Thermophysical properties of Refractory Metals whose melting temperatures are over 2000 K have been measured with an electrostatic levitator. The experimental results for vanadium, zirconium, niobium, molybdenum, rhodium, ruthenium, iridium, tantalum and rhenium are presented. Comparison between theoretical calculations based on hard sphere model and measured data, as well as the necessity of microgravity conditions for this research is also discussed.
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thermophysical properties of liquid Refractory Metals comparison between hard sphere model calculation and electrostatic levitation measurements
Journal of Chemical Physics, 2003Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Toshio Itami, Shinichi YodaAbstract:Thermophysical properties of molten Refractory Metals (titanium, zirconium, hafnium, and niobium) have been measured using a containerless method. Using an in-house developed electrostatic levitator, the density, the heat capacity, the entropy, the surface tension, and the viscosity of liquid phases have been measured over a wide temperature range. The measured data showed good agreement with theoretical calculations based on the hard sphere model.
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new sample levitation initiation and imaging techniques for the processing of Refractory Metals with an electrostatic levitator furnace
Review of Scientific Instruments, 2001Co-Authors: Takehiko Ishikawa, Paulfrancois Paradis, Shinichi YodaAbstract:Two new methods that substantially ease the processing and study of Refractory Metals, when an electrostatic levitation furnace is used, are reported. The first technique is concerned with preheating the sample on a pedestal, prior to launch, to a temperature (∼1500 K) at which thermionic emission dominates all other charging/discharging mechanisms that may be going on simultaneously. Launched into levitation at that temperature, the sample can be quickly heated to its molten state without encountering further charge loss problems. This procedure thus shortens substantially the time it takes to bring the samples to their final high temperature states at which their thermophysical properties can be measured. This technique can be applied to most materials whose melting temperatures are higher than their thermionic temperatures. The second technique described is an ultraviolet-based sample imaging configuration. Due to the excellent sample–background contrast it continuously provides during all phases of pr...
