The Experts below are selected from a list of 18237 Experts worldwide ranked by ideXlab platform
Akira Hasegawa - One of the best experts on this subject based on the ideXlab platform.
-
Seismic evidence for thermally‐controlled Dehydration Reaction in subducting oceanic crust
Geophysical Research Letters, 2009Co-Authors: Junichi Nakajima, Yusuke Tsuji, Akira HasegawaAbstract:[1] We perform travel-time tomography to estimate detailed seismic velocity structures in the crust of the Pacific slab from northeastern (NE) Japan to the Kanto district, Japan, and reveal that the depth extent of the low-velocity (hydrated) oceanic crust varies along the arc. The low-velocity oceanic crust is subducting to depths of 120–150 km beneath Kanto, which is 40–70 km deeper compared to NE Japan. Such deeper preservation of the low-velocity oceanic crust beneath Kanto can be explained by lower-temperature conditions in the Pacific slab as a result of the subduction of the Philippine Sea slab immediately above it. These observations suggest that Dehydration Reactions accompanied by large velocity changes are controlled principally by temperatures, not by pressures. We also find spatial correspondence between intensive seismicity in the oceanic crust and the disappearance depth of the low-velocity oceanic crust, suggesting that breakdown of hydrous minerals triggers earthquakes in the oceanic crust.
-
seismic evidence for thermally controlled Dehydration Reaction in subducting oceanic crust
Geophysical Research Letters, 2009Co-Authors: Junichi Nakajima, Yusuke Tsuji, Akira HasegawaAbstract:[1] We perform travel-time tomography to estimate detailed seismic velocity structures in the crust of the Pacific slab from northeastern (NE) Japan to the Kanto district, Japan, and reveal that the depth extent of the low-velocity (hydrated) oceanic crust varies along the arc. The low-velocity oceanic crust is subducting to depths of 120–150 km beneath Kanto, which is 40–70 km deeper compared to NE Japan. Such deeper preservation of the low-velocity oceanic crust beneath Kanto can be explained by lower-temperature conditions in the Pacific slab as a result of the subduction of the Philippine Sea slab immediately above it. These observations suggest that Dehydration Reactions accompanied by large velocity changes are controlled principally by temperatures, not by pressures. We also find spatial correspondence between intensive seismicity in the oceanic crust and the disappearance depth of the low-velocity oceanic crust, suggesting that breakdown of hydrous minerals triggers earthquakes in the oceanic crust.
Junichi Nakajima - One of the best experts on this subject based on the ideXlab platform.
-
Seismic evidence for thermally‐controlled Dehydration Reaction in subducting oceanic crust
Geophysical Research Letters, 2009Co-Authors: Junichi Nakajima, Yusuke Tsuji, Akira HasegawaAbstract:[1] We perform travel-time tomography to estimate detailed seismic velocity structures in the crust of the Pacific slab from northeastern (NE) Japan to the Kanto district, Japan, and reveal that the depth extent of the low-velocity (hydrated) oceanic crust varies along the arc. The low-velocity oceanic crust is subducting to depths of 120–150 km beneath Kanto, which is 40–70 km deeper compared to NE Japan. Such deeper preservation of the low-velocity oceanic crust beneath Kanto can be explained by lower-temperature conditions in the Pacific slab as a result of the subduction of the Philippine Sea slab immediately above it. These observations suggest that Dehydration Reactions accompanied by large velocity changes are controlled principally by temperatures, not by pressures. We also find spatial correspondence between intensive seismicity in the oceanic crust and the disappearance depth of the low-velocity oceanic crust, suggesting that breakdown of hydrous minerals triggers earthquakes in the oceanic crust.
-
seismic evidence for thermally controlled Dehydration Reaction in subducting oceanic crust
Geophysical Research Letters, 2009Co-Authors: Junichi Nakajima, Yusuke Tsuji, Akira HasegawaAbstract:[1] We perform travel-time tomography to estimate detailed seismic velocity structures in the crust of the Pacific slab from northeastern (NE) Japan to the Kanto district, Japan, and reveal that the depth extent of the low-velocity (hydrated) oceanic crust varies along the arc. The low-velocity oceanic crust is subducting to depths of 120–150 km beneath Kanto, which is 40–70 km deeper compared to NE Japan. Such deeper preservation of the low-velocity oceanic crust beneath Kanto can be explained by lower-temperature conditions in the Pacific slab as a result of the subduction of the Philippine Sea slab immediately above it. These observations suggest that Dehydration Reactions accompanied by large velocity changes are controlled principally by temperatures, not by pressures. We also find spatial correspondence between intensive seismicity in the oceanic crust and the disappearance depth of the low-velocity oceanic crust, suggesting that breakdown of hydrous minerals triggers earthquakes in the oceanic crust.
Ccm Camilo Rindt - One of the best experts on this subject based on the ideXlab platform.
-
Direct numerical simulation of the thermal Dehydration Reaction in a TGA experiment
Applied Thermal Engineering, 2018Co-Authors: S Shuiquan Lan, Ha Herbert Zondag, Aa Anton Van Steenhoven, M Mohammadreza Gaeini, Ccm Camilo RindtAbstract:Abstract This work presents a detailed mathematical model of the coupled mass and heat transfer processes in salt hydrate grains in a TGA experiment. The purpose of developing this numerical model is to get a more fundamental understanding of the influence of parameters like particle size, nucleation rate and vapor pressure on the Dehydration Reaction in a TGA experiment. Such a model needs a detailed description of the fluid flow and water vapor distribution between the particles. The Dehydration Reaction of grains of TCMs is described by the nucleation and nuclei growth model presented in our earlier work. The flow around grains is solved by means of the finite volume method using OpenFOAM including heat and mass transfer. Direct numerical simulations of TGA-experiments under various conditions are performed. Such simulations provide direct insight into the physics of mass and heat transport processes coupled with detailed Reaction kinetics at grain scale. The numerical results are compared to the experimental results. The developed CFD model can be a promising tool to calculate the overall kinetics for Dehydration Reactions under realistic heat storage conditions. To that end, the effect of buoyancy should also be included in the model to get a more accurate description of convection within the sample.
-
An experimentally validated numerical model of interface advance of the lithium sulfate monohydrate Dehydration Reaction
Journal of Thermal Analysis and Calorimetry, 2016Co-Authors: S Shuiquan Lan, Ha Herbert Zondag, Aa Anton Van Steenhoven, Ccm Camilo RindtAbstract:Interface advance plays an essential role in understanding the kinetics and mechanisms of thermal decomposition Reactions such as the Dehydration Reaction of lithium sulfate monocrystals. However, many fundamental processes including mass transfer during interface advance are still not clear. In this work, the dynamics of interface advance, involving interaction between interfacial Reaction and mass diffusion, is investigated numerically together with microscopy observations. A mathematical model is developed for interface advance with a moving boundary and then solved by using a conservative scheme. To examine the significance between the intrinsic chemical Reaction and mass diffusion, a Damkohler number is defined as \(Da=k_{{\rm r}}L/(D_{{\rm e}} c_{0})\). Numerical results at various Da values are discussed to distinguish the limiting step of the Dehydration Reaction of lithium sulfate monocrystals. Moreover, experiments are carried out with a hot-stage microscopy system where the propagation of the Reaction interface into the crystal bulk is followed in situ. By fitting the experimental results with the numerical results, the effective diffusivity of water through the dehydrated crystal is estimated to be in the order of \(10^{-8}\,\hbox {m}^2\,\hbox {s}^{-1}\). According to the corresponding Da values, it is found that, within the Reaction temperature ranging from 110 to 130 °C and a partial water vapor pressure of 13 mbar, the rate of Dehydration interface advance in the bulk of large crystals (typically in the order of millimeters) is not constant, but shows a small decrease over time due to the influence of mass diffusion.
-
Kinetic study of the Dehydration Reaction of lithium sulfate monohydrate crystals using microscopy and modeling
Thermochimica Acta, 2015Co-Authors: S Shuiquan Lan, Ha Herbert Zondag, Aa Anton Van Steenhoven, Ccm Camilo RindtAbstract:Simulation of gas–solid Reactions occurring in industrial processes requires a robust kinetic model to be applicable in a wide range of complicated Reaction conditions. However, in literature it is often seen that even the same Reaction under specific controlled conditions is interpreted with different kinetic models. In the present work, a phenomenological model based on nucleation and nuclei growth processes is presented to study the kinetics of the Dehydration Reaction of lithium sulfate monohydrate single crystals. The two elementary processes of the Reaction, nucleation and nuclei growth, are characterized and quantified as a function of temperature by using optical microscopy experiments. The in-situ measured characteristics of the Dehydration Reaction provided confirmatory evidence that the rate of nucleation obeys an exponential law and the rate of nuclei growth is approximately constant. With knowledge acquired from the optical observations as inputs of the kinetic model, the fractional conversion of the Dehydration Reaction was calculated and compared with experimental results from thermogravimetric analysis (TGA). A satisfactory comparison was found both in isothermal and non-isothermal conditions. It is demonstrated that this knowledge-based model has a great potential to represent the gas–solid Reaction kinetics in a wide range of process conditions regarding temperature, pressure and particle geometry.
Loïc Favergeon - One of the best experts on this subject based on the ideXlab platform.
-
Kinetics and mechanism of the Dehydration of calcium sulfate dehydrate: a comprehensive approach for the Dehydration of ionic hydrates under controlled temperature and water vapor pressure
Journal of Physical Chemistry C, 2020Co-Authors: João G. D. Preturlan, Laetitia Vieille, Sara Quiligotti, Loïc FavergeonAbstract:We studied the kinetics and mechanism of the Dehydration Reaction of calcium sulfate dihydrate to hemihydrate under controlled temperature and water vapor partial pressure. From kinetic and Reaction rate curves obtained using thermogravimetric analysis (TGA) under isothermal and isobaric conditions, we determined the overall behavior of this Dehydration Reaction and the effects of the system’s intensive variables on its kinetics. We observed that the Reactions take place with an initial induction period that decreases with increasing temperature, followed by a sigmoidal mass loss controlled by both nucleation and growth processes. Characterization of our samples at different points of the Reaction allowed us to observe and confirm a surface nucleation process followed by isotropic growth of the nuclei with inward development of the solid product. We then employed the Mampel kinetic model based on the observed experimental results considering the physical nature of the investigated transformation and the real geometry of the particles. From this model, we obtained sets of kinetic parameters for the nucleation and growth processes and their evolution with temperature. We then proposed physicochemical mechanisms for both processes, and they were considered to interpret the kinetic parameters obtained previously. The mechanistic analysis of the system allowed determination of the effects of both temperature and water vapor pressure on the kinetic behavior of the Reaction, which corresponds to a novel approach for the Dehydration Reaction of calcium sulfate dihydrate. The universal kinetic approach used to treat this chemical system in this work can be applied for studying the Dehydration of other ionic hydrates.
-
New kinetic model of the Dehydration Reaction of magnesium sulfate hexahydrate: Application for heat storage
Thermochimica Acta, 2020Co-Authors: Larysa Okhrimenko, Loïc Favergeon, Kevyn Johannes, Frédéric KuznikAbstract:Magnesium sulfate-water vapor is an interesting working pair of thermochemical materials for compact inter-seasonal heat storage at low temperature. Total Dehydration of magnesium sulfate heptahydrate shows a theoretical storage energy density of 2.8 GJ·m−3. However, kinetic data are poorly studied up to now making use of this material difficult for a practical storage application. In the present work, a kinetic study of the Dehydration of MgSO4·6H2O powder at low temperature (35 to 60°C) and at low water vapor pressure (2 to 21 hPa) is carried out using thermogravimetric analysis in isobaric-isothermal conditions. A mathematical model is developed for this bivariant system and validated representing the mechanism of Dehydration: water molecules diffusion in the solid solution followed by transfer of these molecules from the surface to the atmosphere. The transfer of water molecules at the surface during Dehydration is identified as rate-determining step. The fractional conversion and Reaction rate of the Dehydration Reaction are calculated and compared to the experimental data.
-
Thermodynamic study of MgSO4 − H2O system Dehydration at low pressure in view of heat storage Author links open overlay
Thermochimica Acta, 2017Co-Authors: Larysa Okhrimenko, Loïc Favergeon, Kevyn Johannes, Frédéric Kuznik, Michèle PijolatAbstract:Study about magnesium sulfate − water vapor equilibrium proved to be very interesting especially on the use of Dehydration-hydration Reactions for the heat storage application in recent research. Heat is realized by hydration of lower hydrates as this Reaction is exothermic. Therefore, reversible Reaction, endothermic thermal Dehydration of higher hydrates, is used for charging of system and in this state the energy can be stored over long time. Even if magnesium sulfate appears as promising candidate with high theoretical energy density of 2.8 GJ/m−3, technological process is rather complicated. The main problem that thermodynamic and kinetic data are poorly understood to present. In these study salt hydrates equilibrium of magnesium sulfate was investigated by new approach. It makes possible to understand the Dehydration Reaction of MgSO4·6H2O for heat storage application. Dehydration Reaction under various water vapor pressures and temperatures were investigated by thermogravimetric analysis. The result showed that water content in the solid phase is a function of temperature for given water vapor pressure. So, we can conclude that this magnesium sulfate − water vapor system is bivariant and some hydrates appear as the non-stoichiometric hydrates.
Yusuke Tsuji - One of the best experts on this subject based on the ideXlab platform.
-
Seismic evidence for thermally‐controlled Dehydration Reaction in subducting oceanic crust
Geophysical Research Letters, 2009Co-Authors: Junichi Nakajima, Yusuke Tsuji, Akira HasegawaAbstract:[1] We perform travel-time tomography to estimate detailed seismic velocity structures in the crust of the Pacific slab from northeastern (NE) Japan to the Kanto district, Japan, and reveal that the depth extent of the low-velocity (hydrated) oceanic crust varies along the arc. The low-velocity oceanic crust is subducting to depths of 120–150 km beneath Kanto, which is 40–70 km deeper compared to NE Japan. Such deeper preservation of the low-velocity oceanic crust beneath Kanto can be explained by lower-temperature conditions in the Pacific slab as a result of the subduction of the Philippine Sea slab immediately above it. These observations suggest that Dehydration Reactions accompanied by large velocity changes are controlled principally by temperatures, not by pressures. We also find spatial correspondence between intensive seismicity in the oceanic crust and the disappearance depth of the low-velocity oceanic crust, suggesting that breakdown of hydrous minerals triggers earthquakes in the oceanic crust.
-
seismic evidence for thermally controlled Dehydration Reaction in subducting oceanic crust
Geophysical Research Letters, 2009Co-Authors: Junichi Nakajima, Yusuke Tsuji, Akira HasegawaAbstract:[1] We perform travel-time tomography to estimate detailed seismic velocity structures in the crust of the Pacific slab from northeastern (NE) Japan to the Kanto district, Japan, and reveal that the depth extent of the low-velocity (hydrated) oceanic crust varies along the arc. The low-velocity oceanic crust is subducting to depths of 120–150 km beneath Kanto, which is 40–70 km deeper compared to NE Japan. Such deeper preservation of the low-velocity oceanic crust beneath Kanto can be explained by lower-temperature conditions in the Pacific slab as a result of the subduction of the Philippine Sea slab immediately above it. These observations suggest that Dehydration Reactions accompanied by large velocity changes are controlled principally by temperatures, not by pressures. We also find spatial correspondence between intensive seismicity in the oceanic crust and the disappearance depth of the low-velocity oceanic crust, suggesting that breakdown of hydrous minerals triggers earthquakes in the oceanic crust.