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Joris Proost - One of the best experts on this subject based on the ideXlab platform.
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dislocation Hydrogen interaction mechanisms in hydrided nanocrystalline palladium films
Acta Materialia, 2016Co-Authors: Behnam Aminahmadi, Loic Malet, Renaud Delmelle, Marc Fivel, Stephane Godet, Stuart Turner, Thomas Pardoen, Damien Connetable, Doeme Tanguy, Joris ProostAbstract:The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of Hydrogen Loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of Hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of Hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.
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Dislocation/Hydrogen interaction mechanisms in hydrided nanocrystalline palladium films
Acta Materialia, 2016Co-Authors: Behnam Amin-ahmadi, Loic Malet, Renaud Delmelle, Döme Tanguy, Marc Fivel, Stephane Godet, Stuart Turner, Thomas Pardoen, Joris ProostAbstract:The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of Hydrogen Loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of Hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of Hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.
Ojumu Tunde - One of the best experts on this subject based on the ideXlab platform.
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The production of Hydrogen through the use of a 77 wt% Pd 23 wt% Ag membrane water gas shift reactor
South African Journal of Chemical Engineering, 2016Co-Authors: Aloyi, Liberty N, North, Bria C, Langmi, Henrietta W, Ladergroen, Bernard J, Ojumu TundeAbstract:Hydrogen as an energy carrier has the potential to decarbonize the energy sector. This work presents the application of a palladium-silver (PdeAg) membrane-based reactor. The membrane reactor which is made from PdeAg film supported by porous stainless steel (PSS) is evaluated for the production of Hydrogen and the potential replacement of the current two-stage Water-Gas Shift (WGS) reaction by a single stage reaction. The permeability of a 20 mm PdeAg membrane reactor was examined at 320 C, 380 C and 430 C. The effect of continuous Hydrogen exposure on the PdeAg membrane at high temperature and low temperature was examined to investigate the thermal stability and durability of the membrane. During continuous operation to determine thermal stability, the membrane reactor exhibited stable Hydrogen permeation at 320 C for 120 h and unstable Hydrogen permeation at 430 C was observed. For the WGS reaction, the reactor was loaded with Ferrochrome catalyst. The membrane showed the ability to produce high purity Hydrogen, with a CO conversion and an H2 recovery of 84% and 88%, respectively. The membrane suffered from Hydrogen embrittlement due to desorption and adsorption of Hydrogen on the membrane surface. SEM analysis revealed cracks that occurred on the surface of the membrane after Hydrogen exposure. XRD analysis revealed lattice expansion after Hydrogen Loading which suggests the occurrence of phase change from a-phase to the more brittle b-phase.South African Department of Science and Technology (DST) towards HySA Infrastructure KP4 (grant no: HTC004X
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The production of Hydrogen through the use of a 77 wt% Pd 23 wt% Ag membrane water gas shift reactor
Elsevier, 2016Co-Authors: Aloyi, Liberty N, Ernard J. Ladergroe, North, Bria C, Langmi, Henrietta W, Ojumu TundeAbstract:Hydrogen as an energy carrier has the potential to decarbonize the energy sector. This work presents the application of a palladium-silver (PdeAg) membrane-based reactor. The membrane reactor which is made from PdeAg film supported by porous stainless steel (PSS) is evaluated for the production of Hydrogen and the potential replacement of the current two-stage Water-Gas Shift (WGS) reaction by a single stage reaction. The permeability of a 20 mmPdeAg membrane reactor was examined at 320° C, 380° C and 430° C. The effect of continuous Hydrogen exposure on the PdeAg membrane at high temperature and low temperature was examined to investigate the thermal stability and durability of the membrane. During continuous operation to determine thermal stability, the membrane reactor exhibited stable Hydrogen permeation at 320° C for 120 h and unstable Hydrogen permeation at 430° C was observed. For the WGS reaction, the reactor was loaded with Ferrochrome catalyst. The membrane showed the ability to produce high purity Hydrogen, with a CO conversion and an H2 recovery of 84% and 88%, respectively. The membrane suffered from Hydrogen embrittlement due to desorption and adsorption of Hydrogen on the membrane surface. SEM analysis revealed cracks that occurred on the surface of the membrane after Hydrogen exposure. XRD analysis revealed lattice expansion after Hydrogen Loading which suggests the occurrence of phase change from a-phase to the more brittle b-phase.DHE
Hartmut Bartelt - One of the best experts on this subject based on the ideXlab platform.
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EFFECT OF OPTICAL FIBER Hydrogen Loading ON THE INSCRIPTION EFFICIENCY OF CHIRPED BRAGG GRATINGS BY MEANS OF KrF EXCIMER LASER RADIATION
Saint Petersburg National Research University of Information Technologies Mechanics and Optics (ITMO University), 2016Co-Authors: Sergey V. Varzhel, Manfred Rothhardt, Andrey V. Kulikov, Hartmut BarteltAbstract:Subject of Research.We present comparative results of the chirped Bragg gratings inscription efficiency in optical fiber of domestic production with and without low-temperature Hydrogen Loading. Method. Chirped fiber Bragg gratings inscription was made by the Talbot interferometer with chirped phase mask having a chirp rate of 2.3 nm/cm used for the laser beam amplitude separation. The excimer laser system Coherent COMPexPro 150T, working with the gas mixture KrF (248 nm), was used as the radiation source. In order to increase the UV photosensitivity, the optical fiber was placed in a chamber with Hydrogen under a pressure of 10 MPa and kept there for 14 days at 40 °C. Main Results. The usage of the chirped phase mask in a Talbot interferometer scheme has made it possible to get a full width at half-maximum of the fiber Bragg grating reflection spectrum of 3.5 nm with induced diffraction structure length of 5 mm. By preliminary Hydrogen Loading of optical fiber the broad reflection spectrum fiber Bragg gratings with a reflectivity close to 100% has been inscribed. Practical Relevance. The resulting chirped fiber Bragg gratings can be used as dispersion compensators in optical fiber communications, as well as the reflective elements of distributed fiber-optic phase interferometric sensors
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arrays of regenerated fiber bragg gratings in non Hydrogen loaded photosensitive fibers for high temperature sensor networks
Sensors, 2009Co-Authors: Eric Lindner, Christoph Chojetztki, Sven Brueckner, Martin Becker, Manfred Rothhardt, J Vlekken, Hartmut BarteltAbstract:We report about the possibility of using regenerated fiber Bragg gratings generated in photosensitive fibers without applying Hydrogen Loading for high temperature sensor networks. We use a thermally induced regenerative process which leads to a secondary increase in grating reflectivity. This refractive index modification has shown to become more stable after the regeneration up to temperatures of 600 °C. With the use of an interferometric writing technique, it is possible also to generate arrays of regenerated fiber Bragg gratings for sensor networks.
Marc Fivel - One of the best experts on this subject based on the ideXlab platform.
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dislocation Hydrogen interaction mechanisms in hydrided nanocrystalline palladium films
Acta Materialia, 2016Co-Authors: Behnam Aminahmadi, Loic Malet, Renaud Delmelle, Marc Fivel, Stephane Godet, Stuart Turner, Thomas Pardoen, Damien Connetable, Doeme Tanguy, Joris ProostAbstract:The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of Hydrogen Loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of Hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of Hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.
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Dislocation/Hydrogen interaction mechanisms in hydrided nanocrystalline palladium films
Acta Materialia, 2016Co-Authors: Behnam Amin-ahmadi, Loic Malet, Renaud Delmelle, Döme Tanguy, Marc Fivel, Stephane Godet, Stuart Turner, Thomas Pardoen, Joris ProostAbstract:The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of Hydrogen Loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of Hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of Hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.
Thomas Pardoen - One of the best experts on this subject based on the ideXlab platform.
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dislocation Hydrogen interaction mechanisms in hydrided nanocrystalline palladium films
Acta Materialia, 2016Co-Authors: Behnam Aminahmadi, Loic Malet, Renaud Delmelle, Marc Fivel, Stephane Godet, Stuart Turner, Thomas Pardoen, Damien Connetable, Doeme Tanguy, Joris ProostAbstract:The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of Hydrogen Loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of Hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of Hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.
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Dislocation/Hydrogen interaction mechanisms in hydrided nanocrystalline palladium films
Acta Materialia, 2016Co-Authors: Behnam Amin-ahmadi, Loic Malet, Renaud Delmelle, Döme Tanguy, Marc Fivel, Stephane Godet, Stuart Turner, Thomas Pardoen, Joris ProostAbstract:The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of Hydrogen Loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of Hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of Hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.
