Yngve Cerenius - Academia.edu (original) (raw)
Papers by Yngve Cerenius
Acta Materialia, 2007
A detailed analysis of the reaction mechanism of the reactive hydride composite (RHC) MgH 2 + 2Li... more A detailed analysis of the reaction mechanism of the reactive hydride composite (RHC) MgH 2 + 2LiBH 4 M MgB 2 + 2LiH + 4H 2 was performed using high-pressure differential scanning calorimetry (HP-DSC) measurements and in situ synchrotron powder X-ray diffraction (XRD) measurements along with kinetic investigations using a Sievert-type apparatus. For the desorption the following two-step reaction has been observed: MgH 2 + 2LiBH 4 M Mg + 2LiBH 4 + H 2 M MgB 2 + 2LiH + 4H 2 . However, this reaction is kinetically restricted and proceeds only at elevated temperatures. In contrast to the desorption reaction, LiBH 4 and MgH 2 are found to form simultaneously under fairly moderate conditions of 50 bar hydrogen pressure in the temperature range of 250-300°C. As found in pure light metal hydrides, significant improvement of sorption kinetics is possible if suitable additives are used.
Angewandte Chemie-international Edition, 2009
The transition towards a sustainable and reliable energy system capable of meeting the increasing... more The transition towards a sustainable and reliable energy system capable of meeting the increasing energy demands is considered one of the greatest challenges in the 21st century. However, one of the major obstacles is that renewable energy sources are unevenly distributed both geographically and over time, and most countries need to integrate several different sources. Hydrogen is a potential, extremely interesting energy carrier system, [1] but a major challenge in a future "hydrogen economy" is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular for mobile applications. No single material has yet been identified that fulfills all the criteria for hydrogen storage, despite considerable research and technological efforts. Borohydride-based materials have recently received great attention owing to their high gravimetric hydrogen contents, but the utilization of this class of materials in real, practical technological applications is often hampered by unfavorable thermodynamic and kinetic properties. Much research has focused on improving the properties of known interesting hydrogen storage materials such as LiBH 4 , which possesses an extremely high hydrogen content (18.4 wt %) but unfortunately has a high enthalpy of decomposition (À67 kJ mol À1 ) and therefore a high decomposition temperature. Thus, researchers have tried to improve the thermodynamic properties by design of a reactive hydride composite 2 LiBH 4 /MgH 2 , which reduces the enthalpy of decomposition from À67 to À42 kJ mol À1 and which is still capable of reversibly storing 11.5 wt % H 2 . Recently, cation substitution in LiBH 4 has also been realized by, for example, the synthesis of LiK-(BH 4 ) 2 , which unfortunately possesses the same high thermodynamic stability as LiBH 4 and KBH 4 . The kinetic properties of alanates ([AlH 4 ] À ) and magnesium-based systems have been successfully improved by the exploitation of a variety of catalytic additives, but these materials appear less efficient than borohydride-based systems owing to their high chemical reactivity. Numerous other improvements of known materials have been explored, for example, incorporation of LiBH 4 into nanoporous scaffolds, but there has been no major breakthrough that allows the synthesis of ideal hydrogen storage materials with high hydrogen content, low hydrogen decomposition temperature (i.e. appropriate thermodynamic properties), and fast "refueling" of the material (i.e. good kinetic properties). Therefore, there is a great need for new types of compounds, such as ternary borohydrides involving a combination of very different elements, such as alkali metals and transition metals. Herein, we report the synthesis and detailed structural, physical, and chemical characterization of a new series of borohydride-based materials, LiZn 2 (BH 4 ) 5 , NaZn 2 (BH 4 ) 5 , and NaZn(BH 4 ) 3 . These materials have completely novel structures,
LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravi... more LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravimetric and volumetric hydrogen capacity. However, dehydrogenation of LiBH4 occurs above 400^oC, which limits its use in its pristine form. By mixing with Ca(BH4)2, we have tried to lower the dehydrogenation temperature. The underlying design principle of this composite system is the recently proven reversibility
Angewandte Chemie-international Edition, 2009
The transition towards a sustainable and reliable energy system capable of meeting the increasing... more The transition towards a sustainable and reliable energy system capable of meeting the increasing energy demands is considered one of the greatest challenges in the 21st century. However, one of the major obstacles is that renewable energy sources are unevenly distributed both geographically and over time, and most countries need to integrate several different sources. Hydrogen is a potential, extremely interesting energy carrier system, [1] but a major challenge in a future "hydrogen economy" is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular for mobile applications. No single material has yet been identified that fulfills all the criteria for hydrogen storage, despite considerable research and technological efforts. Borohydride-based materials have recently received great attention owing to their high gravimetric hydrogen contents, but the utilization of this class of materials in real, practical technological applications is often hampered by unfavorable thermodynamic and kinetic properties. Much research has focused on improving the properties of known interesting hydrogen storage materials such as LiBH 4 , which possesses an extremely high hydrogen content (18.4 wt %) but unfortunately has a high enthalpy of decomposition (À67 kJ mol À1 ) and therefore a high decomposition temperature. Thus, researchers have tried to improve the thermodynamic properties by design of a reactive hydride composite 2 LiBH 4 /MgH 2 , which reduces the enthalpy of decomposition from À67 to À42 kJ mol À1 and which is still capable of reversibly storing 11.5 wt % H 2 . Recently, cation substitution in LiBH 4 has also been realized by, for example, the synthesis of LiK-(BH 4 ) 2 , which unfortunately possesses the same high thermodynamic stability as LiBH 4 and KBH 4 . The kinetic properties of alanates ([AlH 4 ] À ) and magnesium-based systems have been successfully improved by the exploitation of a variety of catalytic additives, but these materials appear less efficient than borohydride-based systems owing to their high chemical reactivity. Numerous other improvements of known materials have been explored, for example, incorporation of LiBH 4 into nanoporous scaffolds, but there has been no major breakthrough that allows the synthesis of ideal hydrogen storage materials with high hydrogen content, low hydrogen decomposition temperature (i.e. appropriate thermodynamic properties), and fast "refueling" of the material (i.e. good kinetic properties). Therefore, there is a great need for new types of compounds, such as ternary borohydrides involving a combination of very different elements, such as alkali metals and transition metals. Herein, we report the synthesis and detailed structural, physical, and chemical characterization of a new series of borohydride-based materials, LiZn 2 (BH 4 ) 5 , NaZn 2 (BH 4 ) 5 , and NaZn(BH 4 ) 3 . These materials have completely novel structures,
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 Na3AlF6 and NaAlH4 via hydridofluoride phases of the form Na3AlH6−xFx. The analysis of thermodynamics based on literature standard enthalpies of formation yields the technically favourable enthalpy of reaction of roughly 35kJ/molH2 for a theoretical gravimetric hydrogen
Acta Physica Polonica A, 1999
A surprisingly high degree of structural and compositional dynamics is observed in the system LiB... more A surprisingly high degree of structural and compositional dynamics is observed in the system LiBH 4 -LiCl as a function of temperature and time. Rietveld refinement of synchrotron radiation powder X-ray diffraction (SR-PXD) data reveals that Clreadily substitutes for BH 4 in the structure of LiBH 4 . Prolonged heating a sample of LiBH 4 -LiCl (1:1 molar ratio) above the phase transition temperature and below the melting point (108 < T < 275°C) can produce highly chloride substituted hexagonal lithium borohydride, h-Li(BH 4 ) 1-x Cl x , e.g., x ∼ 0.42, after heating from room temperature (RT) to 224°C at 2.5°C/min. LiCl has a higher solubility in h-LiBH 4 as compared to orthorhombic lithium borohydride, o-LiBH 4 , which is illustrated by a LiBH 4 -LiCl (1:1) sample equilibrated at 245°C for 24 days and left at RT for another 13 months. Rietveld refinement reveals that this sample contains o-Li(BH 4 ) 0.91 Cl 0.09 and LiCl. This illustrates a significantly faster dissolution of LiCl in h-LiBH 4 as compared to a slower segregation of LiCl from o-LiBH 4 , which is also demonstrated by in situ SR-PXD from three cycles of heating and cooling of the same Li(BH 4 ) 0.91 Cl 0.09 sample. The substitution of the smaller Clfor the larger BH 4 ion is clearly observed as a reduction in the unit cell volume as a function of time and temperature. A significant stabilization of h-LiBH 4 is found to depend on the degree of anion substitution. Variable temperature solid-state magic-angle spinning (MAS) 7 Li and 11 B NMR experiments on pure LiBH 4 show an increase in full width at half maximum (fwhm) when approaching the phase transition from o-to h-LiBH 4 , which indicates an increase of the relaxation rate (i.e., T 2 decreases). A less pronounced effect is observed for ion-substituted Li(BH 4 ) 1-x Cl x , 0.09 < x < 0.42. The MAS NMR experiments also demonstrate a higher degree of motion in the hexagonal phase, i.e., fwhm is reduced by more than a factor of 10 at the o-to h-LiBH 4 phase transition.
Solid State Sciences, 2011
The thermal decomposition of BaC2O4·3.5H2O and BaC2O4·0.5H2O was investigated using in situ synch... more The thermal decomposition of BaC2O4·3.5H2O and BaC2O4·0.5H2O was investigated using in situ synchrotron X-ray and neutron powder diffraction. The decomposition routes for the barium oxalate hydrates were observed to depend on the applied heating rate. Thermal decomposition of BaC2O4·0.5H2O showed transformation to α-BaC2O4 and to β-BaC2O4 prior to the formation of BaCO3. The decomposition of BaC2O4·3.5H2O showed formation of BaC2O4·0.5H2O
ChemInform, 2010
A New Material for Hydrogen Storage; ScAl 0.8 Mg 0.2 . -The new title hydrogen storage material (... more A New Material for Hydrogen Storage; ScAl 0.8 Mg 0.2 . -The new title hydrogen storage material (obtained by heating appropriate amounts of the metals up to about 1000°C) crystallizes in the cubic space group Pm3m (powder XRD and neutron diffraction). It exhibits very promising properties regarding hydrogen storage capacity, kinetics, and stability towards air oxidation in comparison to hydrogen absorption in state-of-the-art intermetallic compounds. ScAl 0.8 Mg 0.2 absorbs hydrogen while decomposing to ScH2 and Al(Mg) at a hydrogen pressure of 10 MPa and a temperature close to 400°C. The maximum hydrogen storage capacity is 2.7 wt.%, and the hydrogen absorption is completely reversible. -(SAHLBERG, M.; BERAN, P.; NIELSEN, T. K.; CERENIUS, Y.; KADAS, K.; PUNKKINEN, M. P. J.; VITOS, L.; ERIKSSON, O.; JENSEN, T. R.; ANDERSSON*, Y.; J. Solid State Chem. 182 (2009) 11, 3113-3117; Dep. Inorg. Chem., Univ. Uppsala, S-751 21 Uppsala, Swed.; Eng.) -W. Pewestorf 06-010
Applied Physics A-materials Science & Processing, 2011
A new hydrogen absorbing material has been discovered, ScNiAl, which can store 1.5 wt.% hydrogen ... more A new hydrogen absorbing material has been discovered, ScNiAl, which can store 1.5 wt.% hydrogen reversibly. In this compound, hydrogen absorption is a two-step process; solid solution of hydrogen at temperatures below 180°C and decomposition into ScH2 and NiAl at higher temperatures. Detailed analysis of the hydrogen absorption/desorption has been performed using in situ synchrotron radiation powder X-ray diffraction and
Journal of Physical Chemistry C, 2009
LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravi... more LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravimetric and volumetric hydrogen capacity. However, its high dehydrogenation temperature and limited reversibility has been a hurdle for its use in real applications. In ...
Chemistry of Materials, 2008
At least five crystalline phases can be found in the CaSO 4 -H 2 O system, which are gypsum CaSO ... more At least five crystalline phases can be found in the CaSO 4 -H 2 O system, which are gypsum CaSO 4 · 2H 2 O, the subhydrates Rand -CaSO 4 · 0.5H 2 O, and the soluble and insoluble anhydrite CaSO 4 . The formation of these five phases in the CaSO 4 -H 2 O system and their transformations were investigated by in situ time-resolved synchrotron radiation powder X-ray diffraction (SR-PXD) in this study. Furthermore, revised structural models for -CaSO 4 · 0.5H 2 O and soluble anhydrite CaSO 4 are presented. The hydration of R-CaSO 4 · 0.5H 2 O was studied at 25°C and showed that the reaction with H 2 O started immediately after mixing the two reactants and that the formation of CaSO 4 · 2H 2 O was coupled to the depletion of R-CaSO 4 · 0.5H 2 O. The thermal decomposition of CaSO 4 · 2H 2 O was investigated in the temperature range of 25-500°C and showed the formation of R-CaSO 4 · 0.5H 2 O followed by the formation of soluble anhydrite AIII-CaSO 4 , which was gradually converted to insoluble anhydrite AII-CaSO 4 . The thermal decomposition of R-CaSO 4 · 0.5D 2 O was investigated in the temperature range of 25-500°C and showed successive phase transformations to -CaSO 4 · 0.5D 2 O, soluble anhydrite AIII-CaSO 4 , and insoluble anhydrite AII-CaSO 4 . The two polymorphs of anhydrite coexist in the investigated temperature range of 200-500°C. The hydrothermal decomposition of CaSO 4 · 2H 2 O was investigated in the temperature range of 25-200°C using a 1 M HNO 3 or a 1 M LiCl solution, and in both experiments, CaSO 4 · 2H 2 O was converted to R-CaSO 4 · 0.5H 2 O and further to insoluble anhydrite AII-CaSO 4 . A structural model for -CaSO 4 · 0.5H 2 O is proposed on the basis of SR-PXD data and a trigonal unit cell (in hexagonal setting) a ) 6.931 45(3), c ) 12.736 17(4) Å, Z ) 6, and space group P3 1 . A structural model for soluble anhydrite AIII-CaSO 4 is also proposed on the basis of powder neutron diffraction data, and a hexagonal unit cell parameters are a ) 6.9687(1), c ) 6.3004(1) Å, Z ) 3, and space group P6 2 22.
The Journal of Physical Chemistry C, 2010
LiF−MgB 2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH 4 , ... more LiF−MgB 2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH 4 , a significantly kinetic destabilization regarding hydrogenation and dehydrogenation is accomplished. The measured reversible hydrogen capacity amounts to 6.4 wt.%. The kinetic properties are improved significantly during cycling. The formation of a hydridofluoride phase (LiBH 4-y F y ) due to the fluorine anions substitution for hydrogen anions in [BH 4 ]is observed by synchrotron XRD and ATR-FTIR. Hydrogenation and dehydrogenation mechanisms are described based on the fluorine substitution in LiBH 4 .
Journal of Physical Chemistry C, 2008
Lithium tetrahydridoboranate (LiBH 4 ) may be a potentially interesting material for hydrogen sto... more Lithium tetrahydridoboranate (LiBH 4 ) may be a potentially interesting material for hydrogen storage, but in order to absorb and desorb hydrogen routinely and reversibly, the kinetics and thermodynamics need to be improved significantly. A priori, this material has one of the highest theoretical gravimetric hydrogen contents, 18.5 wt %, but unfortunately for practical applications, hydrogen release occurs at too high temperature in a non-reversible way. By means of in situ synchrotron radiation powder X-ray diffraction (SR-PXD), the interaction between LiBH 4 and different additivessSiO 2 , TiCl 3 , LiCl, and Ausis investigated. It is found that silicon dioxide reacts with molten LiBH 4 and forms Li 2 SiO 3 or Li 4 SiO 4 at relatively low amounts of SiO 2 , e.g., with 5.0 and 9.9 mol % SiO 2 in LiBH 4 , whereas, for higher amounts of SiO 2 (e.g., 25.5 mol %), only the Li 2 SiO 3 phase is observed. Furthermore, we demonstrate that a solid-state reaction occurs between LiBH 4 and TiCl 3 to form LiCl at room temperature. At elevated temperatures, more LiCl is formed simultaneously with a decrease in the diffracted intensity from TiCl 3 . Lithium chloride shows some solubility in solid LiBH 4 at T > 100°C. This is the first report of substituents that accommodate the structure of LiBH 4 by a solid/solid dissolution reaction. Gold is found to react with molten LiBH 4 forming a Li-Au alloy with CuAu 3 -type structure. These studies demonstrate that molten LiBH 4 has a high reactivity, and finding a catalyst for this H-rich system may be a challenge.
The Journal of Physical Chemistry C, 2011
Science, 1996
Available thermodynamic data and seismic models favor perovskite (MgSiO3) as the stable phase in ... more Available thermodynamic data and seismic models favor perovskite (MgSiO3) as the stable phase in the mantle. MgSiO3 was heated at temperatures from 1900 to 3200 kelvin with a Nd-YAG laser in diamond-anvil cells to study the phase relations at pressures from 45 to 100 gigapascals. The quenched products were studied with synchrotron x-ray radiation. The results show that MgSiO3 broke down to a mixture of MgO (periclase) and SiO2 (stishovite or an unquenchable polymorph) at pressures from 58 to 85 gigapascals. These results imply that perovskite may not be stable in the lower mantle and that it might be necessary to reconsider the compositional and density models of the mantle.
Radiation Physics and Chemistry, 2009
... (2000), Blanton et al. ... The pressure was determined using laser-excited ruby luminescence ... more ... (2000), Blanton et al. ... The pressure was determined using laser-excited ruby luminescence (Piermarini et al., 1975) in Run 1 and using gold (1 micron powder, ALDRICH) as an internal pressure standard according to the Anderson et al. (1989) equation of state in Run 2. ...
Radiation Physics and Chemistry, 2009
Experimental study of the phase transition in the lithium-excess lithium-manganese spinel over th... more Experimental study of the phase transition in the lithium-excess lithium-manganese spinel over the pressure range 0-13 GPa has shown its suppression. This observation implies that the Li/Mn ratio, associated with the manganese oxidation state, plays an important role in the high-pressure phase transformation of the lithium-manganese spinels. As indicated by the results, the occupation of the octahedral sites with Li + and Mn 4+ ions stabilizes the crystallographic structure of this cubic spinel even at a high pressure.
![Research paper thumbnail of Evidence for structural transition in hairy-rod poly[9,9-bis(2-ethylhexyl)fluorene] under high pressure conditions](https://attachments.academia-assets.com/44695916/thumbnails/1.jpg)
](Physical Review E, 2010
We report on an x-ray scattering experiment of bulk poly͓9,9-bis͑2-ethylhexyl͒fluorene͔ under qua... more We report on an x-ray scattering experiment of bulk poly͓9,9-bis͑2-ethylhexyl͒fluorene͔ under quasihydrostatic pressure from 1 to 11 GPa at room temperature. The scattering pattern of high molecular weight ͑HMW͒ polyfluorene ͑Ͼ10 kg/ mol͒ undergoes significant changes between 2 and 4 GPa in the bulk phase. The 110 reflection of the hexagonal unit cell disappears, indicating a change in equatorial intermolecular order. The intensity of the 00 21 reflection drops, with a sudden move toward higher scattering angles. Beyond these pressures, the diminished 00 21 reflection tends to return toward lower angles. These changes may be interpreted as a transition from crystalline hexagonal to glassy nematic phase ͑perceiving order only in one direc-tion͒. This transition may be rationalized by density arguments and the underlying theory of phase behavior of hairy-rod polyfluorene. Also the possible alteration of the 21-helical main chain toward more planar main chain conformation is discussed. The scattering of low molecular weight polyfluorene ͑Ͻ10 kg/ mol͒, which is glassy nematic in ambient pressure, is reminiscent with that of HMW polymer above 2-4 GPa.
Acta Materialia, 2007
A detailed analysis of the reaction mechanism of the reactive hydride composite (RHC) MgH 2 + 2Li... more A detailed analysis of the reaction mechanism of the reactive hydride composite (RHC) MgH 2 + 2LiBH 4 M MgB 2 + 2LiH + 4H 2 was performed using high-pressure differential scanning calorimetry (HP-DSC) measurements and in situ synchrotron powder X-ray diffraction (XRD) measurements along with kinetic investigations using a Sievert-type apparatus. For the desorption the following two-step reaction has been observed: MgH 2 + 2LiBH 4 M Mg + 2LiBH 4 + H 2 M MgB 2 + 2LiH + 4H 2 . However, this reaction is kinetically restricted and proceeds only at elevated temperatures. In contrast to the desorption reaction, LiBH 4 and MgH 2 are found to form simultaneously under fairly moderate conditions of 50 bar hydrogen pressure in the temperature range of 250-300°C. As found in pure light metal hydrides, significant improvement of sorption kinetics is possible if suitable additives are used.
Angewandte Chemie-international Edition, 2009
The transition towards a sustainable and reliable energy system capable of meeting the increasing... more The transition towards a sustainable and reliable energy system capable of meeting the increasing energy demands is considered one of the greatest challenges in the 21st century. However, one of the major obstacles is that renewable energy sources are unevenly distributed both geographically and over time, and most countries need to integrate several different sources. Hydrogen is a potential, extremely interesting energy carrier system, [1] but a major challenge in a future "hydrogen economy" is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular for mobile applications. No single material has yet been identified that fulfills all the criteria for hydrogen storage, despite considerable research and technological efforts. Borohydride-based materials have recently received great attention owing to their high gravimetric hydrogen contents, but the utilization of this class of materials in real, practical technological applications is often hampered by unfavorable thermodynamic and kinetic properties. Much research has focused on improving the properties of known interesting hydrogen storage materials such as LiBH 4 , which possesses an extremely high hydrogen content (18.4 wt %) but unfortunately has a high enthalpy of decomposition (À67 kJ mol À1 ) and therefore a high decomposition temperature. Thus, researchers have tried to improve the thermodynamic properties by design of a reactive hydride composite 2 LiBH 4 /MgH 2 , which reduces the enthalpy of decomposition from À67 to À42 kJ mol À1 and which is still capable of reversibly storing 11.5 wt % H 2 . Recently, cation substitution in LiBH 4 has also been realized by, for example, the synthesis of LiK-(BH 4 ) 2 , which unfortunately possesses the same high thermodynamic stability as LiBH 4 and KBH 4 . The kinetic properties of alanates ([AlH 4 ] À ) and magnesium-based systems have been successfully improved by the exploitation of a variety of catalytic additives, but these materials appear less efficient than borohydride-based systems owing to their high chemical reactivity. Numerous other improvements of known materials have been explored, for example, incorporation of LiBH 4 into nanoporous scaffolds, but there has been no major breakthrough that allows the synthesis of ideal hydrogen storage materials with high hydrogen content, low hydrogen decomposition temperature (i.e. appropriate thermodynamic properties), and fast "refueling" of the material (i.e. good kinetic properties). Therefore, there is a great need for new types of compounds, such as ternary borohydrides involving a combination of very different elements, such as alkali metals and transition metals. Herein, we report the synthesis and detailed structural, physical, and chemical characterization of a new series of borohydride-based materials, LiZn 2 (BH 4 ) 5 , NaZn 2 (BH 4 ) 5 , and NaZn(BH 4 ) 3 . These materials have completely novel structures,
LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravi... more LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravimetric and volumetric hydrogen capacity. However, dehydrogenation of LiBH4 occurs above 400^oC, which limits its use in its pristine form. By mixing with Ca(BH4)2, we have tried to lower the dehydrogenation temperature. The underlying design principle of this composite system is the recently proven reversibility
Angewandte Chemie-international Edition, 2009
The transition towards a sustainable and reliable energy system capable of meeting the increasing... more The transition towards a sustainable and reliable energy system capable of meeting the increasing energy demands is considered one of the greatest challenges in the 21st century. However, one of the major obstacles is that renewable energy sources are unevenly distributed both geographically and over time, and most countries need to integrate several different sources. Hydrogen is a potential, extremely interesting energy carrier system, [1] but a major challenge in a future "hydrogen economy" is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular for mobile applications. No single material has yet been identified that fulfills all the criteria for hydrogen storage, despite considerable research and technological efforts. Borohydride-based materials have recently received great attention owing to their high gravimetric hydrogen contents, but the utilization of this class of materials in real, practical technological applications is often hampered by unfavorable thermodynamic and kinetic properties. Much research has focused on improving the properties of known interesting hydrogen storage materials such as LiBH 4 , which possesses an extremely high hydrogen content (18.4 wt %) but unfortunately has a high enthalpy of decomposition (À67 kJ mol À1 ) and therefore a high decomposition temperature. Thus, researchers have tried to improve the thermodynamic properties by design of a reactive hydride composite 2 LiBH 4 /MgH 2 , which reduces the enthalpy of decomposition from À67 to À42 kJ mol À1 and which is still capable of reversibly storing 11.5 wt % H 2 . Recently, cation substitution in LiBH 4 has also been realized by, for example, the synthesis of LiK-(BH 4 ) 2 , which unfortunately possesses the same high thermodynamic stability as LiBH 4 and KBH 4 . The kinetic properties of alanates ([AlH 4 ] À ) and magnesium-based systems have been successfully improved by the exploitation of a variety of catalytic additives, but these materials appear less efficient than borohydride-based systems owing to their high chemical reactivity. Numerous other improvements of known materials have been explored, for example, incorporation of LiBH 4 into nanoporous scaffolds, but there has been no major breakthrough that allows the synthesis of ideal hydrogen storage materials with high hydrogen content, low hydrogen decomposition temperature (i.e. appropriate thermodynamic properties), and fast "refueling" of the material (i.e. good kinetic properties). Therefore, there is a great need for new types of compounds, such as ternary borohydrides involving a combination of very different elements, such as alkali metals and transition metals. Herein, we report the synthesis and detailed structural, physical, and chemical characterization of a new series of borohydride-based materials, LiZn 2 (BH 4 ) 5 , NaZn 2 (BH 4 ) 5 , and NaZn(BH 4 ) 3 . These materials have completely novel structures,
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 Na3AlF6 and NaAlH4 via hydridofluoride phases of the form Na3AlH6−xFx. The analysis of thermodynamics based on literature standard enthalpies of formation yields the technically favourable enthalpy of reaction of roughly 35kJ/molH2 for a theoretical gravimetric hydrogen
Acta Physica Polonica A, 1999
A surprisingly high degree of structural and compositional dynamics is observed in the system LiB... more A surprisingly high degree of structural and compositional dynamics is observed in the system LiBH 4 -LiCl as a function of temperature and time. Rietveld refinement of synchrotron radiation powder X-ray diffraction (SR-PXD) data reveals that Clreadily substitutes for BH 4 in the structure of LiBH 4 . Prolonged heating a sample of LiBH 4 -LiCl (1:1 molar ratio) above the phase transition temperature and below the melting point (108 < T < 275°C) can produce highly chloride substituted hexagonal lithium borohydride, h-Li(BH 4 ) 1-x Cl x , e.g., x ∼ 0.42, after heating from room temperature (RT) to 224°C at 2.5°C/min. LiCl has a higher solubility in h-LiBH 4 as compared to orthorhombic lithium borohydride, o-LiBH 4 , which is illustrated by a LiBH 4 -LiCl (1:1) sample equilibrated at 245°C for 24 days and left at RT for another 13 months. Rietveld refinement reveals that this sample contains o-Li(BH 4 ) 0.91 Cl 0.09 and LiCl. This illustrates a significantly faster dissolution of LiCl in h-LiBH 4 as compared to a slower segregation of LiCl from o-LiBH 4 , which is also demonstrated by in situ SR-PXD from three cycles of heating and cooling of the same Li(BH 4 ) 0.91 Cl 0.09 sample. The substitution of the smaller Clfor the larger BH 4 ion is clearly observed as a reduction in the unit cell volume as a function of time and temperature. A significant stabilization of h-LiBH 4 is found to depend on the degree of anion substitution. Variable temperature solid-state magic-angle spinning (MAS) 7 Li and 11 B NMR experiments on pure LiBH 4 show an increase in full width at half maximum (fwhm) when approaching the phase transition from o-to h-LiBH 4 , which indicates an increase of the relaxation rate (i.e., T 2 decreases). A less pronounced effect is observed for ion-substituted Li(BH 4 ) 1-x Cl x , 0.09 < x < 0.42. The MAS NMR experiments also demonstrate a higher degree of motion in the hexagonal phase, i.e., fwhm is reduced by more than a factor of 10 at the o-to h-LiBH 4 phase transition.
Solid State Sciences, 2011
The thermal decomposition of BaC2O4·3.5H2O and BaC2O4·0.5H2O was investigated using in situ synch... more The thermal decomposition of BaC2O4·3.5H2O and BaC2O4·0.5H2O was investigated using in situ synchrotron X-ray and neutron powder diffraction. The decomposition routes for the barium oxalate hydrates were observed to depend on the applied heating rate. Thermal decomposition of BaC2O4·0.5H2O showed transformation to α-BaC2O4 and to β-BaC2O4 prior to the formation of BaCO3. The decomposition of BaC2O4·3.5H2O showed formation of BaC2O4·0.5H2O
ChemInform, 2010
A New Material for Hydrogen Storage; ScAl 0.8 Mg 0.2 . -The new title hydrogen storage material (... more A New Material for Hydrogen Storage; ScAl 0.8 Mg 0.2 . -The new title hydrogen storage material (obtained by heating appropriate amounts of the metals up to about 1000°C) crystallizes in the cubic space group Pm3m (powder XRD and neutron diffraction). It exhibits very promising properties regarding hydrogen storage capacity, kinetics, and stability towards air oxidation in comparison to hydrogen absorption in state-of-the-art intermetallic compounds. ScAl 0.8 Mg 0.2 absorbs hydrogen while decomposing to ScH2 and Al(Mg) at a hydrogen pressure of 10 MPa and a temperature close to 400°C. The maximum hydrogen storage capacity is 2.7 wt.%, and the hydrogen absorption is completely reversible. -(SAHLBERG, M.; BERAN, P.; NIELSEN, T. K.; CERENIUS, Y.; KADAS, K.; PUNKKINEN, M. P. J.; VITOS, L.; ERIKSSON, O.; JENSEN, T. R.; ANDERSSON*, Y.; J. Solid State Chem. 182 (2009) 11, 3113-3117; Dep. Inorg. Chem., Univ. Uppsala, S-751 21 Uppsala, Swed.; Eng.) -W. Pewestorf 06-010
Applied Physics A-materials Science & Processing, 2011
A new hydrogen absorbing material has been discovered, ScNiAl, which can store 1.5 wt.% hydrogen ... more A new hydrogen absorbing material has been discovered, ScNiAl, which can store 1.5 wt.% hydrogen reversibly. In this compound, hydrogen absorption is a two-step process; solid solution of hydrogen at temperatures below 180°C and decomposition into ScH2 and NiAl at higher temperatures. Detailed analysis of the hydrogen absorption/desorption has been performed using in situ synchrotron radiation powder X-ray diffraction and
Journal of Physical Chemistry C, 2009
LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravi... more LiBH4 is one of the promising candidates for hydrogen storage materials because of its high gravimetric and volumetric hydrogen capacity. However, its high dehydrogenation temperature and limited reversibility has been a hurdle for its use in real applications. In ...
Chemistry of Materials, 2008
At least five crystalline phases can be found in the CaSO 4 -H 2 O system, which are gypsum CaSO ... more At least five crystalline phases can be found in the CaSO 4 -H 2 O system, which are gypsum CaSO 4 · 2H 2 O, the subhydrates Rand -CaSO 4 · 0.5H 2 O, and the soluble and insoluble anhydrite CaSO 4 . The formation of these five phases in the CaSO 4 -H 2 O system and their transformations were investigated by in situ time-resolved synchrotron radiation powder X-ray diffraction (SR-PXD) in this study. Furthermore, revised structural models for -CaSO 4 · 0.5H 2 O and soluble anhydrite CaSO 4 are presented. The hydration of R-CaSO 4 · 0.5H 2 O was studied at 25°C and showed that the reaction with H 2 O started immediately after mixing the two reactants and that the formation of CaSO 4 · 2H 2 O was coupled to the depletion of R-CaSO 4 · 0.5H 2 O. The thermal decomposition of CaSO 4 · 2H 2 O was investigated in the temperature range of 25-500°C and showed the formation of R-CaSO 4 · 0.5H 2 O followed by the formation of soluble anhydrite AIII-CaSO 4 , which was gradually converted to insoluble anhydrite AII-CaSO 4 . The thermal decomposition of R-CaSO 4 · 0.5D 2 O was investigated in the temperature range of 25-500°C and showed successive phase transformations to -CaSO 4 · 0.5D 2 O, soluble anhydrite AIII-CaSO 4 , and insoluble anhydrite AII-CaSO 4 . The two polymorphs of anhydrite coexist in the investigated temperature range of 200-500°C. The hydrothermal decomposition of CaSO 4 · 2H 2 O was investigated in the temperature range of 25-200°C using a 1 M HNO 3 or a 1 M LiCl solution, and in both experiments, CaSO 4 · 2H 2 O was converted to R-CaSO 4 · 0.5H 2 O and further to insoluble anhydrite AII-CaSO 4 . A structural model for -CaSO 4 · 0.5H 2 O is proposed on the basis of SR-PXD data and a trigonal unit cell (in hexagonal setting) a ) 6.931 45(3), c ) 12.736 17(4) Å, Z ) 6, and space group P3 1 . A structural model for soluble anhydrite AIII-CaSO 4 is also proposed on the basis of powder neutron diffraction data, and a hexagonal unit cell parameters are a ) 6.9687(1), c ) 6.3004(1) Å, Z ) 3, and space group P6 2 22.
The Journal of Physical Chemistry C, 2010
LiF−MgB 2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH 4 , ... more LiF−MgB 2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH 4 , a significantly kinetic destabilization regarding hydrogenation and dehydrogenation is accomplished. The measured reversible hydrogen capacity amounts to 6.4 wt.%. The kinetic properties are improved significantly during cycling. The formation of a hydridofluoride phase (LiBH 4-y F y ) due to the fluorine anions substitution for hydrogen anions in [BH 4 ]is observed by synchrotron XRD and ATR-FTIR. Hydrogenation and dehydrogenation mechanisms are described based on the fluorine substitution in LiBH 4 .
Journal of Physical Chemistry C, 2008
Lithium tetrahydridoboranate (LiBH 4 ) may be a potentially interesting material for hydrogen sto... more Lithium tetrahydridoboranate (LiBH 4 ) may be a potentially interesting material for hydrogen storage, but in order to absorb and desorb hydrogen routinely and reversibly, the kinetics and thermodynamics need to be improved significantly. A priori, this material has one of the highest theoretical gravimetric hydrogen contents, 18.5 wt %, but unfortunately for practical applications, hydrogen release occurs at too high temperature in a non-reversible way. By means of in situ synchrotron radiation powder X-ray diffraction (SR-PXD), the interaction between LiBH 4 and different additivessSiO 2 , TiCl 3 , LiCl, and Ausis investigated. It is found that silicon dioxide reacts with molten LiBH 4 and forms Li 2 SiO 3 or Li 4 SiO 4 at relatively low amounts of SiO 2 , e.g., with 5.0 and 9.9 mol % SiO 2 in LiBH 4 , whereas, for higher amounts of SiO 2 (e.g., 25.5 mol %), only the Li 2 SiO 3 phase is observed. Furthermore, we demonstrate that a solid-state reaction occurs between LiBH 4 and TiCl 3 to form LiCl at room temperature. At elevated temperatures, more LiCl is formed simultaneously with a decrease in the diffracted intensity from TiCl 3 . Lithium chloride shows some solubility in solid LiBH 4 at T > 100°C. This is the first report of substituents that accommodate the structure of LiBH 4 by a solid/solid dissolution reaction. Gold is found to react with molten LiBH 4 forming a Li-Au alloy with CuAu 3 -type structure. These studies demonstrate that molten LiBH 4 has a high reactivity, and finding a catalyst for this H-rich system may be a challenge.
The Journal of Physical Chemistry C, 2011
Science, 1996
Available thermodynamic data and seismic models favor perovskite (MgSiO3) as the stable phase in ... more Available thermodynamic data and seismic models favor perovskite (MgSiO3) as the stable phase in the mantle. MgSiO3 was heated at temperatures from 1900 to 3200 kelvin with a Nd-YAG laser in diamond-anvil cells to study the phase relations at pressures from 45 to 100 gigapascals. The quenched products were studied with synchrotron x-ray radiation. The results show that MgSiO3 broke down to a mixture of MgO (periclase) and SiO2 (stishovite or an unquenchable polymorph) at pressures from 58 to 85 gigapascals. These results imply that perovskite may not be stable in the lower mantle and that it might be necessary to reconsider the compositional and density models of the mantle.
Radiation Physics and Chemistry, 2009
... (2000), Blanton et al. ... The pressure was determined using laser-excited ruby luminescence ... more ... (2000), Blanton et al. ... The pressure was determined using laser-excited ruby luminescence (Piermarini et al., 1975) in Run 1 and using gold (1 micron powder, ALDRICH) as an internal pressure standard according to the Anderson et al. (1989) equation of state in Run 2. ...
Radiation Physics and Chemistry, 2009
Experimental study of the phase transition in the lithium-excess lithium-manganese spinel over th... more Experimental study of the phase transition in the lithium-excess lithium-manganese spinel over the pressure range 0-13 GPa has shown its suppression. This observation implies that the Li/Mn ratio, associated with the manganese oxidation state, plays an important role in the high-pressure phase transformation of the lithium-manganese spinels. As indicated by the results, the occupation of the octahedral sites with Li + and Mn 4+ ions stabilizes the crystallographic structure of this cubic spinel even at a high pressure.
Physical Review E, 2010
We report on an x-ray scattering experiment of bulk poly͓9,9-bis͑2-ethylhexyl͒fluorene͔ under qua... more We report on an x-ray scattering experiment of bulk poly͓9,9-bis͑2-ethylhexyl͒fluorene͔ under quasihydrostatic pressure from 1 to 11 GPa at room temperature. The scattering pattern of high molecular weight ͑HMW͒ polyfluorene ͑Ͼ10 kg/ mol͒ undergoes significant changes between 2 and 4 GPa in the bulk phase. The 110 reflection of the hexagonal unit cell disappears, indicating a change in equatorial intermolecular order. The intensity of the 00 21 reflection drops, with a sudden move toward higher scattering angles. Beyond these pressures, the diminished 00 21 reflection tends to return toward lower angles. These changes may be interpreted as a transition from crystalline hexagonal to glassy nematic phase ͑perceiving order only in one direc-tion͒. This transition may be rationalized by density arguments and the underlying theory of phase behavior of hairy-rod polyfluorene. Also the possible alteration of the 21-helical main chain toward more planar main chain conformation is discussed. The scattering of low molecular weight polyfluorene ͑Ͻ10 kg/ mol͒, which is glassy nematic in ambient pressure, is reminiscent with that of HMW polymer above 2-4 GPa.