Nico Eigen - Academia.edu (original) (raw)

Papers by Nico Eigen

Aluminiumverbundwerkstoff zur Verwendung in thermischen flussmittelfreien Fugeverfahren, umfassen... more Aluminiumverbundwerkstoff zur Verwendung in thermischen flussmittelfreien Fugeverfahren, umfassend mindestens eine Kernschicht bestehend aus einer Aluminiumkernlegierung und mindestens einer einseitig oder beidseitig auf der Kernschicht vorgesehenen, auseren Lotschicht bestehend aus einer Aluminiumlotlegierung. Die Aufgabe, einen Aluminiumverbundwerkstoff zur Verwendung in einem thermischen flussmittelfreien Fugeverfahren vorzuschlagen, mit welchem die Loteigenschaften sowohl im Vakuum als auch unter Schutzgas ohne die Verwendung von Flussmitteln unter Vermeidung der aus dem Stand der Technik bekannten Nachteile weiter optimiert werden konnen, wird dadurch gelost, dass die Aluminiumlotlegierung folgende Zusammensetzung in Gew.-% aufweist: 6,5 % ≤ Si ≤ 13 %, Fe ≤ 1 %, 230 ppm ≤ Mg ≤ 450 ppm, Bi < 500 ppm, Mn ≤ 0,15 %, Cu ≤ 0,3 %, Zn ≤ 3 %, Ti ≤ 0,30 %, Rest AI und unvermeidbare Verunreinigungen einzeln maximal 0,05 %, in Summe maximal 0,15 % und die Aluminiumlotschicht eine alkali...

Materiau composite d'aluminium trouvant application dans des procedes d'assemblage thermi... more Materiau composite d'aluminium trouvant application dans des procedes d'assemblage thermique sans flux, comprenant au moins une couche noyau constituee d'un alliage d'aluminium de noyau, et au moins une couche exterieure de brasage, appliquee sur une face ou sur les deux faces de la couche noyau, constituee d'un alliage d'aluminium de brasage. L'invention a pour but de fournir un materiau composite d'aluminium trouvant application dans un procede d'assemblage thermique sans flux, permettant d'ameliorer encore les caracteristiques de brasage, aussi bien sous vide que sous gaz inerte, sans utilisation de flux, tout en evitant les inconvenients connus de l'etat de la technique. A cet fin, l'alliage d'aluminium de brasage presente la composition suivante en % en poids: 6,5 % ≤ Si ≤ 13 %, Fe ≤ 1 %, 230 ppm ≤ Mg ≤ 450 ppm, Bi < 500 ppm, Mn ≤ 0,15 %, Cu ≤ 0,3 %, Zn ≤ 3 %, Ti ≤ 0,30 %, le reste etant compose d'AI, et d'impuretes...

The study shows the main properties of AA2195 in relation to the microstructure developing in the... more The study shows the main properties of AA2195 in relation to the microstructure developing in the friction stir weld process, which were comprehensively investigated in the ESA Technology and Research Programme Damage Tolerance of Cryogenic Pressure Vessels (TRP T401-02 MC). Friction Stir Welding (FSW) on 5 mm sheets of AA2195 in T8 condition was performed and process parameters were optimized. Non-destructive Inspection (NDI) methods were used to detect potential defects and metallographic investigations were applied in order to detect their origin. The properties on the friction stir joints were determined and the influence of temperature down to 20 K is shown. Particular attention is given to the microstructure and the fracture characteristics of the friction stir welds and base material. Optical and scanning electron microscopy investigations are used to determine the failure mode. Additionally, the influence of temperature is discussed on the basis of samples fractured at RT, 7...

Renewable Energy, 2012

The destabilizing effect of (X) group IV elements (C, Si, Sn and Ge) on NaH þ Al was investigated... more The destabilizing effect of (X) group IV elements (C, Si, Sn and Ge) on NaH þ Al was investigated. A significant decrease in the desorption temperature as well as the reaction enthalpy of NaH was achieved with additions of C, Si, Ge and Sn due to the formation of NaAlGe and NaAlSi ternary and NaSn binary compounds. Compared to a reaction enthalpy of 114 kJ mol À1 H 2 for NaH above 400 C, lower reaction enthalpies of 94 kJ mol À1 H 2 , 72 kJ mol À1 H 2 , 20 kJ mol À1 H 2 and 2 kJ mol À1 H 2 were obtained for the NaH þ Al þ C, NaH þ Al þ Si, NaH þ Al þ Ge and NaH þ Al þ Sn mixtures with onsets at 270 C, 220 C, 180 C, and 130 C respectively. Reversible hydrogenation was partly achieved in the NaHeAleSi system with the formation of NaAlH 4 þ Si.

GRASSIE:FUNCTIONAL MATER. O-BK, 2006

Surface and Coatings Technology, 2005

This study demonstrates the potential of high-energy milling to use nanostructured cermet powders... more This study demonstrates the potential of high-energy milling to use nanostructured cermet powders for thermal spraying utilizing a TiC-Ni-based composite as model material. The microstructure of coatings processed by VPS and HVOF spraying of nanostructured composite powders is characterized and compared to the initial microstructure of the feedstock. Thus, the effect of different microstructures, which can be produced by high-energy milling, on the microstructural evolution during spraying is evaluated. Results show that partial dissolution and reprecipitation of hard phase material as well coarsening of the binder phase crystallite size occur during the spraying process. However, a homogeneously dispersed hard phase distribution similar to that of the nanostructured precursor powder with hard phase sizes in the range of 100 nm is formed. Additionally, hard phase particles bigger than of 300 nm are retained during spraying. First results concerning hardness and wear resistance of respective coatings are shown and discussed.

Surface and Coatings Technology, 2006

In the present study, the wear behaviour of nanocrystalline coatings of the composition (Ti,Mo)(C... more In the present study, the wear behaviour of nanocrystalline coatings of the composition (Ti,Mo)(C,N)-45 vol. % NiCo, prepared by vacuum plasma spraying (VPS) and high-velocity oxy-fuel (HVOF) spraying of high-energy-milled powder, is characterized and compared to microcrystalline coatings of the same composition. Two-body abrasive wear tests, as well as scratch tests, are applied to produce wear traces on the surfaces of the nano-and microcrystalline coatings. While nanocrystalline HVOF coatings are weaker than their microcrystalline counterparts, nanocrystalline VPS coatings show superior wear resistance. The worn surface morphologies are investigated with optical microscopy, scanning electron microscopy and atomic force microscopy. The wear mechanisms and failure of nano-and microcrystalline coatings are distinctly different and are discussed in detail.

Physical Chemistry Chemical Physics, 2008

NaAlH(4) is the archetypical complex hydride for hydrogen storage. The extraordinary effect of do... more NaAlH(4) is the archetypical complex hydride for hydrogen storage. The extraordinary effect of dopants on the sorption kinetics triggered the investigation of this empirical finding. In this paper, a short review of the state of the art is given. To gain further understanding of the mechanisms involved we label the interacting species during the sorption process. This was experimentally realized by hydrogen-deuterium exchange measurements during the decomposition of NaAlH(4) followed by thermogravimetry, Raman spectroscopy and mass spectrometry. By these experiments we are able to obtain specific information on the diffusing species and formation of intermediates. The activation energy of tracer diffusion in NaAlH(4) is found to be 0.28 eV. The results are evidence for a vacancy-mediated desorption process of NaAlH(4).

Materialwissenschaft und Werkstofftechnik, 2004

Nanocrystalline coatings have a high potential for various engineering applications, e.g. against... more Nanocrystalline coatings have a high potential for various engineering applications, e.g. against wear of rolls in the paper fabrication and as corrosion protection. Using vacuum plasma spray (VPS) and high velocity oxy‐fuel (HVOF) spray techniques, coating materials are exposed to high flame temperatures only for less than a millisecond. Therefore, high‐energy milled powders can be used as feedstock material without losing its nanocrystalline microstructure during the thermal spray process. In this way, homogeneous, dense nanocrystalline coatings can be produced, which show enhanced hardness, thus obtaining promising superior wear resistance. In the present study, (Ti,Mo)(C,N)‐45vol.%NiCo nanocrystalline coatings were prepared by VPS‐ and HVOF‐spraying of high‐energy milled powders. Abrasive wear tests JIS H 8615 with varying number of strokes and scratch tests with a Vickers indenter were applied to produce wear traces on the polished surfaces of the nanocrystalline coatings. Abrasive wear behaviour was analyzed by investigating the surface morphologies with optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental results indicate that the VPS‐coating has higher abrasive wear resistance than the HVOF‐coating according to the JIS H8615 test. The abrasive wear mechanism of VPS‐sprayed nanocrystalline coatings can be delineated as cutting plus ploughing. For HVOF‐sprayed nanocrystalline coatings the abrasive wear mechanism can be described as cutting plus material delamination.

Materials Science and Engineering: A, 2003

TiC Á/Ni based nanocrystalline cermet powders for thermal spraying were produced by high-energy m... more TiC Á/Ni based nanocrystalline cermet powders for thermal spraying were produced by high-energy milling. Milling experiments were performed in an attrition mill and a vibration mill in kilogram scale, and powder morphologies and microstructures were characterized using scanning electron microscopy, X-ray diffraction, and laser scattering for particle size analysis. Milling time and powder input were optimized with respect to the desired microstructure and particle sizes, and the results using both types of mill were compared. Powders with homogeneously dispersed hard phase particles below 300 nm could be produced in both mills. Additional processes for the refinement of powder morphology and particle size distribution are discussed.

Journal of Alloys and Compounds, 2009

Screening experiments were performed in order to investigate the formation of Al-based quaternary... more Screening experiments were performed in order to investigate the formation of Al-based quaternary hydrides on the basis of multi-component mixtures treated by reactive ball milling under hydrogen pressure. The data indicated that the milling parameters and in particular the milling speed and milling time are of great importance to the formation of any new phase obtained by reactive ball milling. Indeed, a higher milling speed was shown to favour the formation of the new phases. In the case of (MgH 2 + Al + LiH) and (MgH 2 + LiAlH 4) mixtures, the formation of a new phase was observed, which exhibits relatively fast decomposition kinetics.

Journal of Alloys and Compounds, 2007

The present study highlights the advantages of milling NaH/Al under moderate hydrogen pressure as... more The present study highlights the advantages of milling NaH/Al under moderate hydrogen pressure as a favourable production step for NaAlH 4-based hydrogen storage materials. Firstly, it is demonstrated that NaAlH 4 can be obtained by applying a moderate hydrogen pressure (6-12 bars) during milling of NaH and Al with and without the presence of an inexpensive catalyst (TiCl 4). The yield of NaAlH 4 depends critically on process parameters, such as hydrogen pressure and milling time. A fully converted product is capable of reversible hydrogen storage without any activation procedure. Under optimized conditions, a capacity of 4.2 wt.% was achieved, and kinetics in the first desorption are comparable to NaAlH 4 doped with TiCl 3. Secondly, the synthesis has been optimized towards shorter milling times. By applying a few absorption/desorption cycles to material that was partially converted during milling, almost full reversible storage capacity can be reached. In addition, kinetics is extremely enhanced. For example, such material exhibits an optimum capacity already after two sorption cycles at 100 bar and 125 °C and allows to absorb 80% of the reversible hydrogen content within a few minutes.

Journal of Alloys and Compounds, 2009

This work demonstrates that hydrogen can be reversibly stored in a composite of NaF and Al. NaF a... more This work demonstrates that hydrogen can be reversibly stored in a composite of NaF and Al. NaF and Al reacts to a mixture of Na 3 AlF 6 and NaAlH 4 via hydridofluoride phases of the form Na 3 AlH 6−x F x. The analysis of thermodynamics based on literature standard enthalpies of formation yields the technically favourable enthalpy of reaction of roughly 35 kJ/mol H 2 for a theoretical gravimetric hydrogen storage capacity of 3.3 wt%. Reaction mechanisms are discussed with respect to substitution of hydrogen by fluorine in complex hydrides.

Journal of Alloys and Compounds, 2008

This work demonstrates that fast sorption kinetics in complex hydrides can be achieved by a simpl... more This work demonstrates that fast sorption kinetics in complex hydrides can be achieved by a simple synthesis method using cost-efficient initial components, if microstructure and powder morphology are optimized. NaH/Al precursors with TiCl4 catalyst were synthesised under varying conditions in argon atmosphere and cycled. The influence of powder morphology and microstructure resulting from different process conditions were studied in detail. It is shown that a homogeneous mixing of the phases and a high surface area of the material is essential for fast kinetics and high reversible capacity. The optimized process can be easily scaled up to a cost-efficient production process for large amounts of storage material and can also be applied for other complex hydrides.

Zeitschrift für Metallkunde, 2003

Abstract The high interface area in nanocrystalline materials leads to advanced structural and fu... more Abstract The high interface area in nanocrystalline materials leads to advanced structural and functional properties that are interesting for a variety of applications and products. Three distinct examples for potential applications are given: Nanocrystalline and submicron-sized light-weight intermetallics based on γ-TiAl exhibiting favourable deformation behaviour at reduced temperatures, nanocrystalline cermet coatings produced by thermal spray process exhibiting improved hardness and wear resistance, and nanocrystalline Mg hydride-based composites for hydrogen storage in future mobile applications exhibiting extremely high, reversible storage capacity and fast kinetics.

Aluminiumverbundwerkstoff zur Verwendung in thermischen flussmittelfreien Fugeverfahren, umfassen... more Aluminiumverbundwerkstoff zur Verwendung in thermischen flussmittelfreien Fugeverfahren, umfassend mindestens eine Kernschicht bestehend aus einer Aluminiumkernlegierung und mindestens einer einseitig oder beidseitig auf der Kernschicht vorgesehenen, auseren Lotschicht bestehend aus einer Aluminiumlotlegierung. Die Aufgabe, einen Aluminiumverbundwerkstoff zur Verwendung in einem thermischen flussmittelfreien Fugeverfahren vorzuschlagen, mit welchem die Loteigenschaften sowohl im Vakuum als auch unter Schutzgas ohne die Verwendung von Flussmitteln unter Vermeidung der aus dem Stand der Technik bekannten Nachteile weiter optimiert werden konnen, wird dadurch gelost, dass die Aluminiumlotlegierung folgende Zusammensetzung in Gew.-% aufweist: 6,5 % ≤ Si ≤ 13 %, Fe ≤ 1 %, 230 ppm ≤ Mg ≤ 450 ppm, Bi < 500 ppm, Mn ≤ 0,15 %, Cu ≤ 0,3 %, Zn ≤ 3 %, Ti ≤ 0,30 %, Rest AI und unvermeidbare Verunreinigungen einzeln maximal 0,05 %, in Summe maximal 0,15 % und die Aluminiumlotschicht eine alkali...

Materiau composite d'aluminium trouvant application dans des procedes d'assemblage thermi... more Materiau composite d'aluminium trouvant application dans des procedes d'assemblage thermique sans flux, comprenant au moins une couche noyau constituee d'un alliage d'aluminium de noyau, et au moins une couche exterieure de brasage, appliquee sur une face ou sur les deux faces de la couche noyau, constituee d'un alliage d'aluminium de brasage. L'invention a pour but de fournir un materiau composite d'aluminium trouvant application dans un procede d'assemblage thermique sans flux, permettant d'ameliorer encore les caracteristiques de brasage, aussi bien sous vide que sous gaz inerte, sans utilisation de flux, tout en evitant les inconvenients connus de l'etat de la technique. A cet fin, l'alliage d'aluminium de brasage presente la composition suivante en % en poids: 6,5 % ≤ Si ≤ 13 %, Fe ≤ 1 %, 230 ppm ≤ Mg ≤ 450 ppm, Bi < 500 ppm, Mn ≤ 0,15 %, Cu ≤ 0,3 %, Zn ≤ 3 %, Ti ≤ 0,30 %, le reste etant compose d'AI, et d'impuretes...

The study shows the main properties of AA2195 in relation to the microstructure developing in the... more The study shows the main properties of AA2195 in relation to the microstructure developing in the friction stir weld process, which were comprehensively investigated in the ESA Technology and Research Programme Damage Tolerance of Cryogenic Pressure Vessels (TRP T401-02 MC). Friction Stir Welding (FSW) on 5 mm sheets of AA2195 in T8 condition was performed and process parameters were optimized. Non-destructive Inspection (NDI) methods were used to detect potential defects and metallographic investigations were applied in order to detect their origin. The properties on the friction stir joints were determined and the influence of temperature down to 20 K is shown. Particular attention is given to the microstructure and the fracture characteristics of the friction stir welds and base material. Optical and scanning electron microscopy investigations are used to determine the failure mode. Additionally, the influence of temperature is discussed on the basis of samples fractured at RT, 7...

Renewable Energy, 2012

The destabilizing effect of (X) group IV elements (C, Si, Sn and Ge) on NaH þ Al was investigated... more The destabilizing effect of (X) group IV elements (C, Si, Sn and Ge) on NaH þ Al was investigated. A significant decrease in the desorption temperature as well as the reaction enthalpy of NaH was achieved with additions of C, Si, Ge and Sn due to the formation of NaAlGe and NaAlSi ternary and NaSn binary compounds. Compared to a reaction enthalpy of 114 kJ mol À1 H 2 for NaH above 400 C, lower reaction enthalpies of 94 kJ mol À1 H 2 , 72 kJ mol À1 H 2 , 20 kJ mol À1 H 2 and 2 kJ mol À1 H 2 were obtained for the NaH þ Al þ C, NaH þ Al þ Si, NaH þ Al þ Ge and NaH þ Al þ Sn mixtures with onsets at 270 C, 220 C, 180 C, and 130 C respectively. Reversible hydrogenation was partly achieved in the NaHeAleSi system with the formation of NaAlH 4 þ Si.

GRASSIE:FUNCTIONAL MATER. O-BK, 2006

Surface and Coatings Technology, 2005

This study demonstrates the potential of high-energy milling to use nanostructured cermet powders... more This study demonstrates the potential of high-energy milling to use nanostructured cermet powders for thermal spraying utilizing a TiC-Ni-based composite as model material. The microstructure of coatings processed by VPS and HVOF spraying of nanostructured composite powders is characterized and compared to the initial microstructure of the feedstock. Thus, the effect of different microstructures, which can be produced by high-energy milling, on the microstructural evolution during spraying is evaluated. Results show that partial dissolution and reprecipitation of hard phase material as well coarsening of the binder phase crystallite size occur during the spraying process. However, a homogeneously dispersed hard phase distribution similar to that of the nanostructured precursor powder with hard phase sizes in the range of 100 nm is formed. Additionally, hard phase particles bigger than of 300 nm are retained during spraying. First results concerning hardness and wear resistance of respective coatings are shown and discussed.

Surface and Coatings Technology, 2006

In the present study, the wear behaviour of nanocrystalline coatings of the composition (Ti,Mo)(C... more In the present study, the wear behaviour of nanocrystalline coatings of the composition (Ti,Mo)(C,N)-45 vol. % NiCo, prepared by vacuum plasma spraying (VPS) and high-velocity oxy-fuel (HVOF) spraying of high-energy-milled powder, is characterized and compared to microcrystalline coatings of the same composition. Two-body abrasive wear tests, as well as scratch tests, are applied to produce wear traces on the surfaces of the nano-and microcrystalline coatings. While nanocrystalline HVOF coatings are weaker than their microcrystalline counterparts, nanocrystalline VPS coatings show superior wear resistance. The worn surface morphologies are investigated with optical microscopy, scanning electron microscopy and atomic force microscopy. The wear mechanisms and failure of nano-and microcrystalline coatings are distinctly different and are discussed in detail.

Physical Chemistry Chemical Physics, 2008

NaAlH(4) is the archetypical complex hydride for hydrogen storage. The extraordinary effect of do... more NaAlH(4) is the archetypical complex hydride for hydrogen storage. The extraordinary effect of dopants on the sorption kinetics triggered the investigation of this empirical finding. In this paper, a short review of the state of the art is given. To gain further understanding of the mechanisms involved we label the interacting species during the sorption process. This was experimentally realized by hydrogen-deuterium exchange measurements during the decomposition of NaAlH(4) followed by thermogravimetry, Raman spectroscopy and mass spectrometry. By these experiments we are able to obtain specific information on the diffusing species and formation of intermediates. The activation energy of tracer diffusion in NaAlH(4) is found to be 0.28 eV. The results are evidence for a vacancy-mediated desorption process of NaAlH(4).

Materialwissenschaft und Werkstofftechnik, 2004

Nanocrystalline coatings have a high potential for various engineering applications, e.g. against... more Nanocrystalline coatings have a high potential for various engineering applications, e.g. against wear of rolls in the paper fabrication and as corrosion protection. Using vacuum plasma spray (VPS) and high velocity oxy‐fuel (HVOF) spray techniques, coating materials are exposed to high flame temperatures only for less than a millisecond. Therefore, high‐energy milled powders can be used as feedstock material without losing its nanocrystalline microstructure during the thermal spray process. In this way, homogeneous, dense nanocrystalline coatings can be produced, which show enhanced hardness, thus obtaining promising superior wear resistance. In the present study, (Ti,Mo)(C,N)‐45vol.%NiCo nanocrystalline coatings were prepared by VPS‐ and HVOF‐spraying of high‐energy milled powders. Abrasive wear tests JIS H 8615 with varying number of strokes and scratch tests with a Vickers indenter were applied to produce wear traces on the polished surfaces of the nanocrystalline coatings. Abrasive wear behaviour was analyzed by investigating the surface morphologies with optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental results indicate that the VPS‐coating has higher abrasive wear resistance than the HVOF‐coating according to the JIS H8615 test. The abrasive wear mechanism of VPS‐sprayed nanocrystalline coatings can be delineated as cutting plus ploughing. For HVOF‐sprayed nanocrystalline coatings the abrasive wear mechanism can be described as cutting plus material delamination.

Materials Science and Engineering: A, 2003

TiC Á/Ni based nanocrystalline cermet powders for thermal spraying were produced by high-energy m... more TiC Á/Ni based nanocrystalline cermet powders for thermal spraying were produced by high-energy milling. Milling experiments were performed in an attrition mill and a vibration mill in kilogram scale, and powder morphologies and microstructures were characterized using scanning electron microscopy, X-ray diffraction, and laser scattering for particle size analysis. Milling time and powder input were optimized with respect to the desired microstructure and particle sizes, and the results using both types of mill were compared. Powders with homogeneously dispersed hard phase particles below 300 nm could be produced in both mills. Additional processes for the refinement of powder morphology and particle size distribution are discussed.

Journal of Alloys and Compounds, 2009

Screening experiments were performed in order to investigate the formation of Al-based quaternary... more Screening experiments were performed in order to investigate the formation of Al-based quaternary hydrides on the basis of multi-component mixtures treated by reactive ball milling under hydrogen pressure. The data indicated that the milling parameters and in particular the milling speed and milling time are of great importance to the formation of any new phase obtained by reactive ball milling. Indeed, a higher milling speed was shown to favour the formation of the new phases. In the case of (MgH 2 + Al + LiH) and (MgH 2 + LiAlH 4) mixtures, the formation of a new phase was observed, which exhibits relatively fast decomposition kinetics.

Journal of Alloys and Compounds, 2007

The present study highlights the advantages of milling NaH/Al under moderate hydrogen pressure as... more The present study highlights the advantages of milling NaH/Al under moderate hydrogen pressure as a favourable production step for NaAlH 4-based hydrogen storage materials. Firstly, it is demonstrated that NaAlH 4 can be obtained by applying a moderate hydrogen pressure (6-12 bars) during milling of NaH and Al with and without the presence of an inexpensive catalyst (TiCl 4). The yield of NaAlH 4 depends critically on process parameters, such as hydrogen pressure and milling time. A fully converted product is capable of reversible hydrogen storage without any activation procedure. Under optimized conditions, a capacity of 4.2 wt.% was achieved, and kinetics in the first desorption are comparable to NaAlH 4 doped with TiCl 3. Secondly, the synthesis has been optimized towards shorter milling times. By applying a few absorption/desorption cycles to material that was partially converted during milling, almost full reversible storage capacity can be reached. In addition, kinetics is extremely enhanced. For example, such material exhibits an optimum capacity already after two sorption cycles at 100 bar and 125 °C and allows to absorb 80% of the reversible hydrogen content within a few minutes.

Journal of Alloys and Compounds, 2009

This work demonstrates that hydrogen can be reversibly stored in a composite of NaF and Al. NaF a... more This work demonstrates that hydrogen can be reversibly stored in a composite of NaF and Al. NaF and Al reacts to a mixture of Na 3 AlF 6 and NaAlH 4 via hydridofluoride phases of the form Na 3 AlH 6−x F x. The analysis of thermodynamics based on literature standard enthalpies of formation yields the technically favourable enthalpy of reaction of roughly 35 kJ/mol H 2 for a theoretical gravimetric hydrogen storage capacity of 3.3 wt%. Reaction mechanisms are discussed with respect to substitution of hydrogen by fluorine in complex hydrides.

Journal of Alloys and Compounds, 2008

This work demonstrates that fast sorption kinetics in complex hydrides can be achieved by a simpl... more This work demonstrates that fast sorption kinetics in complex hydrides can be achieved by a simple synthesis method using cost-efficient initial components, if microstructure and powder morphology are optimized. NaH/Al precursors with TiCl4 catalyst were synthesised under varying conditions in argon atmosphere and cycled. The influence of powder morphology and microstructure resulting from different process conditions were studied in detail. It is shown that a homogeneous mixing of the phases and a high surface area of the material is essential for fast kinetics and high reversible capacity. The optimized process can be easily scaled up to a cost-efficient production process for large amounts of storage material and can also be applied for other complex hydrides.

Zeitschrift für Metallkunde, 2003

Abstract The high interface area in nanocrystalline materials leads to advanced structural and fu... more Abstract The high interface area in nanocrystalline materials leads to advanced structural and functional properties that are interesting for a variety of applications and products. Three distinct examples for potential applications are given: Nanocrystalline and submicron-sized light-weight intermetallics based on γ-TiAl exhibiting favourable deformation behaviour at reduced temperatures, nanocrystalline cermet coatings produced by thermal spray process exhibiting improved hardness and wear resistance, and nanocrystalline Mg hydride-based composites for hydrogen storage in future mobile applications exhibiting extremely high, reversible storage capacity and fast kinetics.