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A P Voyt - One of the best experts on this subject based on the ideXlab platform.
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influence of uniaxial pressing and nickel catalytic additive on activation of magnesium Hydride thermal Decomposition
International Journal of Hydrogen Energy, 2017Co-Authors: D. I. Elets, A P Voyt, I. V. Shikin, I A Chernov, M Dobrotvorskii, I. E. GabisAbstract:Abstract Speed-up of thermal Decomposition of magnesium Hydride due to uniaxial pressing, including pressing in presence of nickel catalyst, was studied by barometry, SEM, DSC, XRD methods, and using mathematical modeling. Pressing even with no catalyst is shown to hasten the hydrogen desorption. The most probable reason for this is the formation of multiple defects in crystal lattice. They can serve as nucleation centers: metal nuclei significantly hasten hydrogen desorption. Besides, metal magnesium not converted to the Hydride during the synthesis stage can possibly appear at surface. Adding nickel powder before pressing hastens dehydriding process even more. Comparing hydrogen evolution curves for samples with different amount of nickel allowed to propose the probable mechanism of hydrogen evolution. It is based on description of reactions of hydrogen desorption and Hydride Decomposition and of the metal-Hydride phase morphology change due to these reactions. We develop a mathematical model in form of ordinary differential equations that fits the experimental data well. The model is based on conservation and symmetry assumptions. The fitting allowed to evaluate rate parameters of Hydride phase Decomposition.
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Activation of magnesium Hydride by pressing with catalytic additives
Technical Physics Letters, 2017Co-Authors: I. V. Shikin, A P Voyt, D. I. Elets, I. E. GabisAbstract:We have studied the activation of magnesium Hydride Decomposition by means of its pressing with a catalyst. It is established that pressing leads to the formation of metal nuclei, which favor a decrease in the temperature threshold of magnesium Hydride Decomposition. The introduction of catalytic additives also reduces the temperature of dehydrogenation. The most effective in this respect was found to be the addition of nickel powder.
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Decomposition kinetics of metal Hydrides: Experiments and modeling
Journal of Alloys and Compounds, 2013Co-Authors: I. E. Gabis, I A Chernov, A P VoytAbstract:Abstract The aim of the research was to understand Decomposition of Hydrides of metals and determine the most significant limiting reactions. We used functions that describe real physical processes, such as Decomposition of Hydride phase, desorption and diffusion of hydrogen, and morphology of phases. Dividing Hydride materials to two classes depending on the type of bonding (metallic or non-metallic) allowed to explain details of kinetics of dehydriding. We show that for Decomposition of non-metallic Hydrides morphology of “nucleation and growth” is typical; while for metallic ones the “shrinking core” morphology is more common. In both cases hydrogen diffuses from the Hydride-metal boundary to the outer surface through the metal phase rather quickly, so diffusion does not influence on the Decomposition kinetics. The most probable limiting factor is the rate of hydrogen desorption from the metal phase. For the “shrinking core” morphology rate of Hydride Decomposition can also influence on the kinetics during the final stages of the process.
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Hydride Decomposition characterization by means of morphological trajectory method applied to alh3
Journal of Alloys and Compounds, 2011Co-Authors: E A Evard, A P VoytAbstract:Abstract New approach to analyse Hydride Decomposition kinetics operating with integral morphological parameters as well as kinetic parameters of possible rate-limiting reactions (nucleation, desorption and reaction at interface) is proposed. Morphology of new phase growth in powder particle is described in terms of specific values of new phase volume, outer surface occupied by new phase, interface area and their interrelations (“morphological trajectories”). The approach describes H-release kinetics for free-form shape of particles and growing nuclei. The applicability of the approach is limited by the requirements of fast enough H-diffusivity in metal areas of powder particles and of nucleation at the outer surface of particles. Alane powder completely meets these requirements. It was found that the rate-limiting step is the reaction at the interface with activation energy 104 kJ/mol. Morphology of the transformation depends on experiment conditions: the higher is reaction temperature, the smaller is quantity of new phase nuclei.
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Hydride Decomposition characterization by means of “morphological trajectory” method—Applied to AlH3
Journal of Alloys and Compounds, 2011Co-Authors: E A Evard, A P VoytAbstract:Abstract New approach to analyse Hydride Decomposition kinetics operating with integral morphological parameters as well as kinetic parameters of possible rate-limiting reactions (nucleation, desorption and reaction at interface) is proposed. Morphology of new phase growth in powder particle is described in terms of specific values of new phase volume, outer surface occupied by new phase, interface area and their interrelations (“morphological trajectories”). The approach describes H-release kinetics for free-form shape of particles and growing nuclei. The applicability of the approach is limited by the requirements of fast enough H-diffusivity in metal areas of powder particles and of nucleation at the outer surface of particles. Alane powder completely meets these requirements. It was found that the rate-limiting step is the reaction at the interface with activation energy 104 kJ/mol. Morphology of the transformation depends on experiment conditions: the higher is reaction temperature, the smaller is quantity of new phase nuclei.
Vladimir P. Zhdanov - One of the best experts on this subject based on the ideXlab platform.
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Grain boundary mediated hydriding phase transformations in individual polycrystalline metal nanoparticles
Nature Communications, 2017Co-Authors: Svetlana Alekseeva, Alice Bastos Da Silva Fanta, Beniamino Iandolo, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Jakob Birkedal Wagner, Andrew Burrows, Vladimir P. Zhdanov, Christoph LanghammerAbstract:Grain boundaries separate crystallites in solids and influence material properties, as widely documented for bulk materials. In nanomaterials, however, investigations of grain boundaries are very challenging and just beginning. Here, we report the systematic mapping of the role of grain boundaries in the hydrogenation phase transformation in individual Pd nanoparticles. Employing multichannel single-particle plasmonic nanospectroscopy, we observe large variation in particle-specific Hydride-formation pressure, which is absent in Hydride Decomposition. Transmission Kikuchi diffraction suggests direct correlation between length and type of grain boundaries and Hydride-formation pressure. This correlation is consistent with tensile lattice strain induced by hydrogen localized near grain boundaries as the dominant factor controlling the phase transition during hydrogen absorption. In contrast, such correlation is absent for Hydride Decomposition, suggesting a different phase-transition pathway. In a wider context, our experimental setup represents a powerful platform to unravel microstructure-function correlations at the individual-nanoparticle level.
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Grain boundary mediated hydriding phase transformations in individual polycrystalline metal nanoparticles
Nature Communications, 2017Co-Authors: Svetlana Alekseeva, Beniamino Iandolo, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Jakob Birkedal Wagner, Andrew Burrows, Vladimir P. Zhdanov, Alice Bastos Da Silva Fanta, Christoph LanghammerAbstract:Grain boundaries separate crystallites in solids and influence material properties, as widely documented for bulk materials. In nanomaterials, however, investigations of grain boundaries are very challenging and just beginning. Here, we report the systematic mapping of the role of grain boundaries in the hydrogenation phase transformation in individual Pd nanoparticles. Employing multichannel single-particle plasmonic nanospectroscopy, we observe large variation in particle-specific Hydride-formation pressure, which is absent in Hydride Decomposition. Transmission Kikuchi diffraction suggests direct correlation between length and type of grain boundaries and Hydride-formation pressure. This correlation is consistent with tensile lattice strain induced by hydrogen localized near grain boundaries as the dominant factor controlling the phase transition during hydrogen absorption. In contrast, such correlation is absent for Hydride Decomposition, suggesting a different phase-transition pathway. In a wider context, our experimental setup represents a powerful platform to unravel microstructure–function correlations at the individual-nanoparticle level. Grain boundaries are thought to significantly mediate phase transformations in nanoparticles. Here, the authors combine multichannel plasmonic nanospectroscopy and transmission Kikuchi diffraction to study the role of grain boundaries in hydriding reactions of Pd nanoparticles on a single-particle level.
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Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape
Nature Materials, 2015Co-Authors: Svetlana Syrenova, Tomasz J. Antosiewicz, Carl Wadell, Tina Gschneidtner, Giammarco Nalin, Dominika Świtlik, Fredrik Westerlund, Ferry A. A. Nugroho, Yuri A. Diaz Fernandez, Vladimir P. ZhdanovAbstract:Physicochemical properties of nanoparticles may depend on their size and shape and are traditionally assessed in ensemble-level experiments, which accordingly may be plagued by averaging effects. These effects can be eliminated in single-nanoparticle experiments. Using plasmonic nanospectroscopy, we present a comprehensive study of Hydride formation thermodynamics in individual Pd nanocrystals of different size and shape, and find corresponding enthalpies and entropies to be nearly size- and shape-independent. The hysteresis observed is significantly wider than in bulk, with details depending on the specifics of individual nanoparticles. Generally, the absorption branch of the hysteresis loop is size-dependent in the sub-30 nm regime, whereas desorption is size- and shape-independent. The former is consistent with a coherent phase transition during Hydride formation, influenced kinetically by the specifics of nucleation, whereas the latter implies that Hydride Decomposition either occurs incoherently or via different kinetic pathways. The physicochemical properties of nanoparticles can sometimes prove difficult to characterize. Using plasmonic nanospectroscopy, Hydride formation thermodynamics in individual Pd nanocrystals are found to be nearly size- and shape-independent.
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Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape
Nature Materials, 2015Co-Authors: Svetlana Syrenova, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Carl Wadell, Tina Gschneidtner, Yuri Diaz Fernandez, Giammarco Nalin, Dominika Świtlik, Fredrik Westerlund, Vladimir P. ZhdanovAbstract:Physicochemical properties of nanoparticles may depend on their size and shape and are traditionally assessed in ensemble-level experiments, which accordingly may be plagued by averaging effects. These effects can be eliminated in single-nanoparticle experiments. Using plasmonic nanospectroscopy, we present a comprehensive study of Hydride formation thermodynamics in individual Pd nanocrystals of different size and shape, and find corresponding enthalpies and entropies to be nearly size- and shape-independent. The hysteresis observed is significantly wider than in bulk, with details depending on the specifics of individual nanoparticles. Generally, the absorption branch of the hysteresis loop is size-dependent in the sub-30 nm regime, whereas desorption is size- and shape-independent. The former is consistent with a coherent phase transition during Hydride formation, influenced kinetically by the specifics of nucleation, whereas the latter implies that Hydride Decomposition either occurs incoherently or via different kinetic pathways.
Christoph Langhammer - One of the best experts on this subject based on the ideXlab platform.
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Grain boundary mediated hydriding phase transformations in individual polycrystalline metal nanoparticles
Nature Communications, 2017Co-Authors: Svetlana Alekseeva, Alice Bastos Da Silva Fanta, Beniamino Iandolo, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Jakob Birkedal Wagner, Andrew Burrows, Vladimir P. Zhdanov, Christoph LanghammerAbstract:Grain boundaries separate crystallites in solids and influence material properties, as widely documented for bulk materials. In nanomaterials, however, investigations of grain boundaries are very challenging and just beginning. Here, we report the systematic mapping of the role of grain boundaries in the hydrogenation phase transformation in individual Pd nanoparticles. Employing multichannel single-particle plasmonic nanospectroscopy, we observe large variation in particle-specific Hydride-formation pressure, which is absent in Hydride Decomposition. Transmission Kikuchi diffraction suggests direct correlation between length and type of grain boundaries and Hydride-formation pressure. This correlation is consistent with tensile lattice strain induced by hydrogen localized near grain boundaries as the dominant factor controlling the phase transition during hydrogen absorption. In contrast, such correlation is absent for Hydride Decomposition, suggesting a different phase-transition pathway. In a wider context, our experimental setup represents a powerful platform to unravel microstructure-function correlations at the individual-nanoparticle level.
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Grain boundary mediated hydriding phase transformations in individual polycrystalline metal nanoparticles
Nature Communications, 2017Co-Authors: Svetlana Alekseeva, Beniamino Iandolo, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Jakob Birkedal Wagner, Andrew Burrows, Vladimir P. Zhdanov, Alice Bastos Da Silva Fanta, Christoph LanghammerAbstract:Grain boundaries separate crystallites in solids and influence material properties, as widely documented for bulk materials. In nanomaterials, however, investigations of grain boundaries are very challenging and just beginning. Here, we report the systematic mapping of the role of grain boundaries in the hydrogenation phase transformation in individual Pd nanoparticles. Employing multichannel single-particle plasmonic nanospectroscopy, we observe large variation in particle-specific Hydride-formation pressure, which is absent in Hydride Decomposition. Transmission Kikuchi diffraction suggests direct correlation between length and type of grain boundaries and Hydride-formation pressure. This correlation is consistent with tensile lattice strain induced by hydrogen localized near grain boundaries as the dominant factor controlling the phase transition during hydrogen absorption. In contrast, such correlation is absent for Hydride Decomposition, suggesting a different phase-transition pathway. In a wider context, our experimental setup represents a powerful platform to unravel microstructure–function correlations at the individual-nanoparticle level. Grain boundaries are thought to significantly mediate phase transformations in nanoparticles. Here, the authors combine multichannel plasmonic nanospectroscopy and transmission Kikuchi diffraction to study the role of grain boundaries in hydriding reactions of Pd nanoparticles on a single-particle level.
I. E. Gabis - One of the best experts on this subject based on the ideXlab platform.
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influence of uniaxial pressing and nickel catalytic additive on activation of magnesium Hydride thermal Decomposition
International Journal of Hydrogen Energy, 2017Co-Authors: D. I. Elets, A P Voyt, I. V. Shikin, I A Chernov, M Dobrotvorskii, I. E. GabisAbstract:Abstract Speed-up of thermal Decomposition of magnesium Hydride due to uniaxial pressing, including pressing in presence of nickel catalyst, was studied by barometry, SEM, DSC, XRD methods, and using mathematical modeling. Pressing even with no catalyst is shown to hasten the hydrogen desorption. The most probable reason for this is the formation of multiple defects in crystal lattice. They can serve as nucleation centers: metal nuclei significantly hasten hydrogen desorption. Besides, metal magnesium not converted to the Hydride during the synthesis stage can possibly appear at surface. Adding nickel powder before pressing hastens dehydriding process even more. Comparing hydrogen evolution curves for samples with different amount of nickel allowed to propose the probable mechanism of hydrogen evolution. It is based on description of reactions of hydrogen desorption and Hydride Decomposition and of the metal-Hydride phase morphology change due to these reactions. We develop a mathematical model in form of ordinary differential equations that fits the experimental data well. The model is based on conservation and symmetry assumptions. The fitting allowed to evaluate rate parameters of Hydride phase Decomposition.
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Activation of magnesium Hydride by pressing with catalytic additives
Technical Physics Letters, 2017Co-Authors: I. V. Shikin, A P Voyt, D. I. Elets, I. E. GabisAbstract:We have studied the activation of magnesium Hydride Decomposition by means of its pressing with a catalyst. It is established that pressing leads to the formation of metal nuclei, which favor a decrease in the temperature threshold of magnesium Hydride Decomposition. The introduction of catalytic additives also reduces the temperature of dehydrogenation. The most effective in this respect was found to be the addition of nickel powder.
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Decomposition kinetics of metal Hydrides: Experiments and modeling
Journal of Alloys and Compounds, 2013Co-Authors: I. E. Gabis, I A Chernov, A P VoytAbstract:Abstract The aim of the research was to understand Decomposition of Hydrides of metals and determine the most significant limiting reactions. We used functions that describe real physical processes, such as Decomposition of Hydride phase, desorption and diffusion of hydrogen, and morphology of phases. Dividing Hydride materials to two classes depending on the type of bonding (metallic or non-metallic) allowed to explain details of kinetics of dehydriding. We show that for Decomposition of non-metallic Hydrides morphology of “nucleation and growth” is typical; while for metallic ones the “shrinking core” morphology is more common. In both cases hydrogen diffuses from the Hydride-metal boundary to the outer surface through the metal phase rather quickly, so diffusion does not influence on the Decomposition kinetics. The most probable limiting factor is the rate of hydrogen desorption from the metal phase. For the “shrinking core” morphology rate of Hydride Decomposition can also influence on the kinetics during the final stages of the process.
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Thermal- and photoactivation of aluminum Hydride Decomposition
Russian Journal of Physical Chemistry A, 2012Co-Authors: I. E. Gabis, D. I. Elets, V. G. Kuznetsov, A. P. Baraban, M. A. Dobrotvorskii, A. M. DobrotvorskiiAbstract:Processes occurring in the phase of AlH_3 dehydrogenation incubation that precedes the active Decomposition of the Hydride and is evidently accompanied by a change in its material properties are investigated by thermal desorption spectroscopy and barometry. The electronic structures of α-AlH_3 and α-AlH_3:V(H0) (i.e., aluminum Hydride with a neutral hydrogen atom removed) are calculated by the density functional method. It is shown that hydrogen vacancies are the source of nuclei for the metallic phase, and their emergence could be thermally activated. It is established that UV irradiation also leads to the formation of hydrogen vacancies in α-AlH_3. A description of the probable mechanism for the accumulation of hydrogen vacancies at elevated temperatures and finally to the appearance of metallic phase nuclei is offered. It is shown that UV irradiation allows us to lower the temperature of the dehydrogenation of α-AlH_3 crystals.
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kinetics of Decomposition of erbium Hydride
Journal of Alloys and Compounds, 2003Co-Authors: I. E. Gabis, E A Evard, A P Voyt, I A Chernov, Yu V ZaikaAbstract:Erbium was used as a model Hydride-forming metal to study the possibility of applying thermal desorption spectroscopy (TDS) to research into Hydride Decomposition. The possibility of varying heating rates and final temperatures makes TDS acceptable for providing experimental information about the kinetics of Decomposition. Discrimination of models and evaluation of rate constants were performed by fitting computer-simulation derived curves to experimental ones. The most probable models have boundary-value problems in which the rates of Decomposition, desorption and migration of hydrogen are taken into account. The movement of an interface between Hydride and solid solution of hydrogen is determined by all these reactions.
Tomasz J. Antosiewicz - One of the best experts on this subject based on the ideXlab platform.
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Grain boundary mediated hydriding phase transformations in individual polycrystalline metal nanoparticles
Nature Communications, 2017Co-Authors: Svetlana Alekseeva, Alice Bastos Da Silva Fanta, Beniamino Iandolo, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Jakob Birkedal Wagner, Andrew Burrows, Vladimir P. Zhdanov, Christoph LanghammerAbstract:Grain boundaries separate crystallites in solids and influence material properties, as widely documented for bulk materials. In nanomaterials, however, investigations of grain boundaries are very challenging and just beginning. Here, we report the systematic mapping of the role of grain boundaries in the hydrogenation phase transformation in individual Pd nanoparticles. Employing multichannel single-particle plasmonic nanospectroscopy, we observe large variation in particle-specific Hydride-formation pressure, which is absent in Hydride Decomposition. Transmission Kikuchi diffraction suggests direct correlation between length and type of grain boundaries and Hydride-formation pressure. This correlation is consistent with tensile lattice strain induced by hydrogen localized near grain boundaries as the dominant factor controlling the phase transition during hydrogen absorption. In contrast, such correlation is absent for Hydride Decomposition, suggesting a different phase-transition pathway. In a wider context, our experimental setup represents a powerful platform to unravel microstructure-function correlations at the individual-nanoparticle level.
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Grain boundary mediated hydriding phase transformations in individual polycrystalline metal nanoparticles
Nature Communications, 2017Co-Authors: Svetlana Alekseeva, Beniamino Iandolo, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Jakob Birkedal Wagner, Andrew Burrows, Vladimir P. Zhdanov, Alice Bastos Da Silva Fanta, Christoph LanghammerAbstract:Grain boundaries separate crystallites in solids and influence material properties, as widely documented for bulk materials. In nanomaterials, however, investigations of grain boundaries are very challenging and just beginning. Here, we report the systematic mapping of the role of grain boundaries in the hydrogenation phase transformation in individual Pd nanoparticles. Employing multichannel single-particle plasmonic nanospectroscopy, we observe large variation in particle-specific Hydride-formation pressure, which is absent in Hydride Decomposition. Transmission Kikuchi diffraction suggests direct correlation between length and type of grain boundaries and Hydride-formation pressure. This correlation is consistent with tensile lattice strain induced by hydrogen localized near grain boundaries as the dominant factor controlling the phase transition during hydrogen absorption. In contrast, such correlation is absent for Hydride Decomposition, suggesting a different phase-transition pathway. In a wider context, our experimental setup represents a powerful platform to unravel microstructure–function correlations at the individual-nanoparticle level. Grain boundaries are thought to significantly mediate phase transformations in nanoparticles. Here, the authors combine multichannel plasmonic nanospectroscopy and transmission Kikuchi diffraction to study the role of grain boundaries in hydriding reactions of Pd nanoparticles on a single-particle level.
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Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape
Nature Materials, 2015Co-Authors: Svetlana Syrenova, Tomasz J. Antosiewicz, Carl Wadell, Tina Gschneidtner, Giammarco Nalin, Dominika Świtlik, Fredrik Westerlund, Ferry A. A. Nugroho, Yuri A. Diaz Fernandez, Vladimir P. ZhdanovAbstract:Physicochemical properties of nanoparticles may depend on their size and shape and are traditionally assessed in ensemble-level experiments, which accordingly may be plagued by averaging effects. These effects can be eliminated in single-nanoparticle experiments. Using plasmonic nanospectroscopy, we present a comprehensive study of Hydride formation thermodynamics in individual Pd nanocrystals of different size and shape, and find corresponding enthalpies and entropies to be nearly size- and shape-independent. The hysteresis observed is significantly wider than in bulk, with details depending on the specifics of individual nanoparticles. Generally, the absorption branch of the hysteresis loop is size-dependent in the sub-30 nm regime, whereas desorption is size- and shape-independent. The former is consistent with a coherent phase transition during Hydride formation, influenced kinetically by the specifics of nucleation, whereas the latter implies that Hydride Decomposition either occurs incoherently or via different kinetic pathways. The physicochemical properties of nanoparticles can sometimes prove difficult to characterize. Using plasmonic nanospectroscopy, Hydride formation thermodynamics in individual Pd nanocrystals are found to be nearly size- and shape-independent.
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Hydride formation thermodynamics and hysteresis in individual Pd nanocrystals with different size and shape
Nature Materials, 2015Co-Authors: Svetlana Syrenova, Tomasz J. Antosiewicz, Ferry Anggoro Ardy Nugroho, Carl Wadell, Tina Gschneidtner, Yuri Diaz Fernandez, Giammarco Nalin, Dominika Świtlik, Fredrik Westerlund, Vladimir P. ZhdanovAbstract:Physicochemical properties of nanoparticles may depend on their size and shape and are traditionally assessed in ensemble-level experiments, which accordingly may be plagued by averaging effects. These effects can be eliminated in single-nanoparticle experiments. Using plasmonic nanospectroscopy, we present a comprehensive study of Hydride formation thermodynamics in individual Pd nanocrystals of different size and shape, and find corresponding enthalpies and entropies to be nearly size- and shape-independent. The hysteresis observed is significantly wider than in bulk, with details depending on the specifics of individual nanoparticles. Generally, the absorption branch of the hysteresis loop is size-dependent in the sub-30 nm regime, whereas desorption is size- and shape-independent. The former is consistent with a coherent phase transition during Hydride formation, influenced kinetically by the specifics of nucleation, whereas the latter implies that Hydride Decomposition either occurs incoherently or via different kinetic pathways.