Global warming is an increasing concern worldwide. Assessing the contribution of CO2 to this phenomenon is an important issue. This project's goal is to improve understanding of CO2 and H2O transport ...in a mountainous terrain that confound current efforts to resolve CO2 budgets at regional and global scales.
Solid state phase transformations in metals, and more precisely the science of transformation interfaces, is a key point to understand the formation of nano/microstructure, and thus, as a result, ...many physical properties such as mechanical properties, conductivity, thermoelectric and magnetic properties of materials.
Steels are by far the most widely used metallic alloys, and a deep understanding of their microstructure is essential to tailor their service properties. The transformation of high temperature parent austenite to ferrite is one of the main issues controlling the final microstructures, and for more than a century, this has driven metallurgists to investigate in detail this solid state transformation, and, particularly, the details of austenite to ferrite interface migration.
In this paper, we review the evolution of the different concepts and experiments developed in the last century to investigate this transformation mechanism.
After a brief introduction, most of the physical models developed, which reduce the α/γ interface into a mathematical body with its own properties, are reviewed and discussed with regard to experimental data. The increased availability of highly sophisticated experimental and modelling tools in recent decades has considerably clarified the perceptions of transformation interfaces. These recent advances are presented, and their contribution to the field of migrating austenite–ferrite interfaces are highlighted in a third section. In the fourth section, the latest developments in experimental methods, which now allow the quasi atomistic direct characterization of the interface chemistry, are presented. The observed conditions at the interfaces can be compared with model predictions, which is believed to be a critical step for the refinement of the theoretical concepts guiding the understanding of the interface migration. Finally, in the concluding section, the present situation of the field is summarized, and some perspectives regarding the expected future developments are sketched.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
The Juno spacecraft measured Jupiter’s gravity field and determined the even and odd zonal harmonics,
J
n
, with unprecedented precision. However, interpreting these observations has been a ...challenge because it is difficult to reconcile the unexpectedly small magnitudes of the moments
J
4
and
J
6
with conventional interior models that assume a large, distinct core of rock and ice. Here we show that the entire set of gravity harmonics can be matched with models that assume an ab initio equation of state, wind profiles, and a dilute core of heavy elements that are distributed as far out as 63% of the planet’s radius. In the core region, heavy elements are predicted to be distributed uniformly and make up only 18% by mass because of dilution with hydrogen and helium. Our models are consistent with the existence of primary and secondary dynamo layers that will help explain the complexity of the observed magnetic field.
ALEMI is concerned with the interactions between Alloying Elements and Migrating Interfaces. A first meeting was held in conjunction with the 2000 TMS Fall Meeting in St. Louis, MO. About 22 ...attendees endorsed the principles contained in the invitation, which envisaged a more collaborative approach to the study of alloying element interactions with transformation interfaces, especially in alloy steels. The meetings were intended to be informal workshops emphasizing the sharing of ideas and plans for research. The development of a shared stock of alloys for research was planned, as well as the publication of summaries of discussions in an open, preferably archival, forum. Eight further meetings were held, often in conjunction with major conferences. An approximate equilibrium developed between discussions of theoretical matters and experimental results and methods. A remarkable number of those who attended the first meeting in St. Louis continued to participate. Research ideas were put forward, issues debated, collaborations fostered, and the science of transformation interfaces advanced.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental ...investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ), activity expansion (ACTEX), and all-electron Green's function Korringa-Kohn-Rostoker (MECCA), and compute the pressure and internal energy of BN over a broad range of densities and temperatures. Our experiments were conducted at the Omega laser facility and the Hugoniot response of BN to unprecedented pressures (1200–2650 GPa). The EOSs computed using different methods cross validate one another in the warm-dense matter regime, and the experimental Hugoniot data are in good agreement with our theoretical predictions. By comparing the EOS results from different methods, we assess that the largest discrepancies between theoretical predictions are ≲4% in pressure and ≲3% in energy and occur at 106K, slightly below the peak compression that corresponds to the K-shell ionization regime. At these conditions, we find remarkable consistency between the EOS from DFT calculations performed on different platforms and using different exchange-correlation functionals and those from PIMC using free-particle nodes. This provides strong evidence for the accuracy of both PIMC and DFT in the high-pressure, high-temperature regime. Moreover, the recently developed SQ and FOE methods produce EOS data that have significantly smaller statistical error bars than PIMC, and so represent significant advances for efficient computation at high temperatures. The shock Hugoniot predicted by PIMC, ACTEX, and MECCA shows a maximum compression ratio of 4.55±0.05 for an initial density of 2.26g/cm3, higher than the Thomas-Fermi predictions by about 5%. In addition, we construct tabular EOS models that are consistent with the first-principles simulations and the experimental data. Our findings clarify the ionic and electronic structure of BN over a broad range of temperatures and densities and quantify their roles in the EOS and properties of this material. The tabular models may be utilized for future simulations of laser-driven experiments that include BN as a candidate ablator material.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
We examine the performance of pure boron, boron carbide, high density carbon, and boron nitride ablators in the polar direct drive exploding pusher (PDXP) platform. The platform uses the polar direct ...drive configuration at the National Ignition Facility to drive high ion temperatures in a room temperature capsule and has potential applications for plasma physics studies and as a neutron source. The higher tensile strength of these materials compared to plastic enables a thinner ablator to support higher gas pressures, which could help optimize its performance for plasma physics experiments, while ablators containing boron enable the possibility of collecting additional data to constrain models of the platform. Applying recently developed and experimentally validated equation of state models for the boron materials, we examine the performance of these materials as ablators in 2D simulations, with particular focus on changes to the ablator and gas areal density, as well as the predicted symmetry of the inherently 2D implosion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, we examine the performance of pure boron, boron carbide, high density carbon, and boron nitride ablators in the polar direct drive exploding pusher (PDXP) platform. The platform uses ...the polar direct drive configuration at the National Ignition Facility to drive high ion temperatures in a room temperature capsule and has potential applications for plasma physics studies and as a neutron source. The higher tensile strength of these materials compared to plastic enables a thinner ablator to support higher gas pressures, which could help optimize its performance for plasma physics experiments, while ablators containing boron enable the possibility of collecting additional data to constrain models of the platform. Applying recently developed and experimentally validated equation of state models for the boron materials, we examine the performance of these materials as ablators in 2D simulations, with particular focus on changes to the ablator and gas areal density, as well as the predicted symmetry of the inherently 2D implosion.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
ALEMI is concerned with the interactions between Alloying Elements and Migrating Interfaces. A first meeting was held in conjunction with the 2000 TMS Fall Meeting in St. Louis, MO. About 22 ...attendees endorsed the principles contained in the invitation, which envisaged a more collaborative approach to the study of alloying element interactions with transformation interfaces, especially in alloy steels. The meetings were intended to be informal workshops emphasizing the sharing of ideas and plans for research. The development of a shared stock of alloys for research was planned, as well as the publication of summaries of discussions in an open, preferably archival, forum. Eight further meetings were held, often in conjunction with major conferences. An approximate equilibrium developed between discussions of theoretical matters and experimental results and methods. A remarkable number of those who attended the first meeting in St. Louis continued to participate. Research ideas were put forward, issues debated, collaborations fostered, and the science of transformation interfaces advanced.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We examine the performance of pure boron, boron carbide, high density carbon, and boron nitride ablators in the polar direct drive exploding pusher (PDXP) platform. The platform uses the polar direct ...drive configuration at the National Ignition Facility to drive high ion temperatures in a room temperature capsule and has potential applications for plasma physics studies and as a neutron source. The higher tensile strength of these materials compared to plastic enables a thinner ablator to support higher gas pressures, which could help optimize its performance for plasma physics experiments, while ablators containing boron enable the possiblity of collecting addtional data to constrain models of the platform. Applying recently developed and experimentally validated equation of state models for the boron materials, we examine the performance of these materials as ablators in 2D simulations, with particular focus on changes to the ablator and gas areal density, as well as the predicted symmetry of the inherently 2D implosion.
The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental ...investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ), activity expansion (ACTEX), and all-electron Green's function Korringa-Kohn-Rostoker (MECCA), and compute the pressure and internal energy of BN over a broad range of densities (\(\rho\)) and temperatures (\(T\)). Our experiments were conducted at the Omega laser facility and measured the Hugoniot of BN to unprecedented pressures (12--30 Mbar). The EOSs computed using different methods cross validate one another, and the experimental Hugoniot are in good agreement with our theoretical predictions. We assess that the largest discrepancies between theoretical predictions are \(<\)4% in pressure and \(<\)3% in energy and occur at \(10^6\) K. We find remarkable consistency between the EOS from DFT calculations performed on different platforms and using different exchange-correlation functionals and those from PIMC using free-particle nodes. This provides strong evidence for the accuracy of both PIMC and DFT in the warm-dense regime. Moreover, SQ and FOE data have significantly smaller error bars than PIMC, and so represent significant advances for efficient computation at high \(T\). We also construct tabular EOS models and clarify the ionic and electronic structure of BN over a broad \(T-\rho\) range and quantify their roles in the EOS. The tabular models may be utilized for future simulations of laser-driven experiments that include BN as a candidate ablator material.
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