| 1. |
- Biendicho, Jordi Jacas, et al.
(författare)
-
In situ investigation of commercial Ni(OH)(2) and LaNi5-based electrodes by neutron powder diffraction
- 2015
-
Ingår i: Journal of Materials Research. - : Springer Science and Business Media LLC. - 0884-2914 .- 2044-5326. ; 30:3, s. 407-416
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochemical reactions at both positive and negative electrodes in a nickel metal hydride (Ni-MH) battery during charge have been investigated by in situ neutron powder diffraction. Commercially available beta-Ni(OH)(2) and LaNi5-based powders were used in this experiment as positive and negative electrodes, respectively. Exchange of hydrogen by deuterium for the beta-Ni(OH)(2) electrode was achieved by ex situ cycling of the cell prior to in situ measurements. Neutron diffraction data collected in situ show that the largest amount of deuterium contained at the positive electrode is de-intercalated from the electrode with no phase transformation involved up to similar to 100 mA h/g and, in addition, the 110 peak width for the positive electrode increases on charge. The negative electrode of composition MmNi(3.6)Al(0.4)Mn(0.3)Co(0.7), where Mm = Mischmetal, exhibits a phase transformation to an intermediate hydride gamma phase first and then to the beta phase on charge. Unit cell dimensions and phase fractions have been investigated by Rietveld refinement of the crystal structure.
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| 2. |
- Biendicho, Jordi Jacas, et al.
(författare)
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New in-situ neutron diffraction cell for electrode materials
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 248, s. 900-904
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Tidskriftsartikel (refereegranskat)abstract
- A novel neutron diffraction cell has been constructed to allow in-situ studies of the structural changes in materials of relevance to battery applications during charge/discharge cycling. The new design is based on the coin cell geometry, but has larger dimensions compared to typical commercial batteries in order to maximize the amount of electrode material and thus, collect diffraction data of good statistical quality within the shortest possible time. An important aspect of the design is its modular nature, allowing flexibility in both the materials studied and the battery configuration. This paper reports electrochemical tests using a Nickel-metal-hydride battery (Ni-MH), which show that the cell is able to deliver 90% of its theoretical capacity when using deuterated components. Neutron diffraction studies performed on the Polaris diffractometer using nickel metal and a hydrogen-absorbing alloy (MH) clearly show observable changes in the neutron diffraction patterns as a function of the discharge state. Due to the high quality of the diffraction patterns collected in-situ (i.e. good peak-to-background ratio), phase analysis and peak indexing can be performed successfully using data collected in around 30 min. In addition to this, structural parameters for the beta-phase (charged) MH electrode obtained by Rietveld refinement are presented. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
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| 3. |
- Biendicho, Jordi Jacas, et al.
(författare)
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New Opportunities for Air Cathode Batteries; in-Situ Neutron Diffraction Measurements
- 2018
-
Ingår i: Frontiers in energy research. - : Frontiers Media SA. - 2296-598X. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Batteries with air electrodes are gaining interest as Energy Storage Systems (ESSs) for Electrical Vehicles (EVs) because of their high specific energy density. The electrochemical performance of these batteries is limited by the metallic electrode, which suffers structural transformations and corrosion during cycling that reduces the cycle life of the battery. In this context, relevant information on the discharge products may be obtained by in-situ neutron diffraction, a suitable technique to study electrodes that contain light elements or near neighbor elements in the periodic table. Case studies of MH-air and Fe-air batteries are highlighted.
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| 4. |
- Björling, Thomas, 1976-
(författare)
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Synthesis and characterisation of Zintl hydrides
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The synthesis, structural characterisation and the properties of the Zintl hydrides AeE2H2 and AeAlSiH (Ae = Ba, Ca, Sr; E = Al, Ga, In, Si, Zn) are reported. The first hydride in this class of compounds is SrAl2H2 which was discovered under an experiment by Gingl, who hydrogenated SrAl2 at various temperatures. (Gingl et al, Journal of Alloys and Compounds 306 (2000) 127-132). The intention was to form alanates, e.g. AlH4-, by terminating the three dimensional four connected aluminium network in SrAl2. The new hydride, SrAl2H2, has a partially conserved aluminium network. The three dimensional anionic network in SrAl2 is reduced to two dimensions in the hydride, with aluminium bonded to both aluminium and hydrogen. This type of bonding configuration has not been observed before.The hydrogenation of SrAl2 is straight forward, 190 oC and 50 bar, compared to the difficult synthesis of alanates and alane, AlH3. The latter synthesises uses aluminium in its zero oxidation state in contrast to the synthesis of SrAl2H2 from SrAl2. (In the SrAl2-precursor aluminium is reduced by the electropositive metal to -I.) Thus, the discovery shows a different route to alanates by using precursors with aluminium in a reduced state. If SrAl2H2 is further hydrogenated at 250 oC the two dimensional network breaks and Sr2AlH7 forms.We wanted to investigate if SrAl2H2 was a singularity or if other similar compounds exist. We wanted to study how hydrogenation of precursors similar to the aluminide result in 1) new routes to compounds with high hydrogen content, as alanates, 2) to investigate how the E-H bond is affected as function of the network composition among different ternary hydrides, in particular BaAlxSi2-xHx, and choice of active metal.BaGa2H2 and SrGa2H2, two hydrides isostructural with SrAl2H2, were synthesized from its precursors BaGa2 and SrGa2. In addition three ternary hydrides BaAlSiH, CaAlSiH and SrAlSiH were manufactured from their related AeAlSi precursors.All powders were characterized by neutron and x-ray diffraction methods.An increased stability towards water/moisture compared to ordinary saline hydrides was noticed, especially for the ternary hydrides. Heat stability was measured with DSC (differential scanning calorimetry). The hydrides BaGa2H2 and SrGa2H2 decompose around 300 oC at 1 atm. This is similar to isostructural SrAl2H2. The ternary hydrides BaAlSiH and SrAlSiH decompose at 600 oC, at 1 atm, which is the highest noticed temperature for compounds with Al-H bonds. Inelastic neutron scattering experiments showed that these hydrides Al-H and Sr-H bonds are really weak, even weaker then the Al-H interactions in alanates and alanes. These hydrides are probably stabilized be their lattices. The electric properties among the ternary hydrides were measured with IR-spectroscopy (diffuse reflectance). The ternary hydrides, AeAlSiH, are indirect semi conductors. BaGa2H2 and SrGa2H2 are conductors. The ternary hydrides, AeAlxSi2-xHx, may have adjustable band gaps, which we were not able to determine.This work is leading into a new research area within the field of metal hydrides.
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| 5. |
- Börjesson Axén, Jenny, 1986-, et al.
(författare)
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A Structural Investigation into the OCV Hysteresis of the Ni(OH)2 Electrode
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Powder X-ray diffraction (XRPD), X-ray absorption spectroscopy (EXAFS and XANES) and Raman spectroscopy were used to study chemical changes in the polycrystalline nickel hydroxide positive electrode material of a NiMH battery at four states of charge: 0%, 50% and 100% charged, and 50% discharged. The two 50% samples were at the same state of charge but in different hysteresis states, manifested by differences in the open circuit potential. The nickel hydroxide electrodes consist of particles in the µm size range, and all measurements were performed ex situ. The material studied was taken from commercial batteries and as such contained both metallic nickel particles, cobalt, and zinc dopants in the active Ni(OH)2 material as well as a cobalt oxide surface layer. Combining the results from all the characterization methods was necessary to better understand the chemistry behind the physio-chemical hysteresis behavior in this complex system. Our results show that there are structural differences between the two 50% samples. Comparison of the XRPD results and the EXAFS results on the nickel edge indicate a presence of the kinetically favored TP2-NiOOH phase in the transition between β-Ni(OH)2 and β-NiOOH and that the amount differs between the two hysteresis states. The measurements on the zinc edge using EXAFS and XANES suggest short range differences in the active material bulk that stems from disorder. Raman spectroscopy measurements show a difference in degree of lithium intercalation in the LiCoO2 surface layer between the hysteresis states. As electrochemistry takes place on the surface of the particles, it is likely that differences in the surface structure are responsible for the open circuit voltage hysteresis. However, due to the coherence of the structure differences detected, it is probable that they are all connected and have a part in the observed behavior.
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| 6. |
- Chamoun, Mylad, et al.
(författare)
-
Bifunctional Performance of Flow Assisted Rechargeable Iron-Air Alkaline Batteries
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Low cost rechargeable iron-air alkaline batteries have all essential attributes to adapt for large scale energy storage applications. To actualize this implementation needs to overcome the challenges including poor efficiency and short cycle lifetime. Herein, suitable synthesized catalysts for the air electrode were investigated prior to iron-air cell testing. NiCo2O4 as sole catalyst proved exceptional bifunctional OER/ORR activity and stability over 440 h operation in air. This catalyst fitted into an electrolyte and oxygen flow assisted rechargeable iron-air prototype and performed stable over 588 h and had an energy density of 377 Wh kg-1 Fe. Inadequate coulombic efficiencies of 75 – 85% and energy efficiencies around 50% hurt the performance of the cell though and needed further development. Nevertheless, the findings in this work reports the opportunities and obstacles of the rechargeable iron-air battery.
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| 7. |
- Chamoun, Mylad, et al.
(författare)
-
Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.
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| 8. |
- Chamoun, Mylad, et al.
(författare)
-
Rechargeability of aqueous sulfate Zn/MnO2 batteries enhanced by accessible Mn2+ ions
- 2018
-
Ingår i: Energy Storage Materials. - : Elsevier BV. - 2405-8289 .- 2405-8297. ; 15, s. 351-360
-
Tidskriftsartikel (refereegranskat)abstract
- The Zn/MnO2 battery is safe, low cost and comes with a high energy density comparable to Li-ion batteries. However, irreversible spinel phases formed at the MnO2 electrode limits its cyclability. A viable solution to overcome this inactive phase is to use an aqueous ZnSO4-based electrolyte, where pH is mildly acidic leading to a different reaction mechanism. Most importantly, the addition of MnSO4 achieves excellent cyclability. How accessible Mn2+ ions in the electrolyte enhances the reversibility is presented. With added Mn2+, the capacity retention is significantly improved over 100 cycles. Zn2+ insertion plays an important role on the reversibility and a hydrated layered Zn-buserite structure formed during charge is reported. Furthermore, Zn4SO4(OH)(6) center dot 5H(2)O precipitates during discharge but is not involved in the electrochemical reaction. This precipitate both buffers the pH and partly insulates the surface. Described in operando study show how the phase transformations and the failure mechanisms depend on the presence of Mn2+-ions in the electrolyte. These results give insight necessary to improve this battery further to make it a worthy contender to the Li-ion battery in large scale energy storage solutions.
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| 9. |
- Chamoun, Mylad, 1989-
(författare)
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Rechargeable Aqueous Batteries Based on Available Resources : Investigation and Development towards Efficient Battery Performance
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Batteries employing water based electrolytes enable extremely low manufacturing costs and are inherently safer than Li-ion batteries. Batteries based on zinc, manganese dioxide, iron, and air have high energy relevancy, are not resource restricted, and can contribute to large scale energy storage solutions. Zinc has a rich history as electrode material for primary alkaline Zn–MnO2 batteries. Historically, its use in secondary batteries has been limited because of morphological uncertainties and passivation effects that may lead to cell failure. Manganese dioxide electrodes are ineffective as rechargeable electrodes because of failure mechanisms associated with phase transformations during cycling. The irreversibility of manganese dioxide is strongly correlated to the formation of the electrochemically inactive spinel, Mn3O4/ZnMn2O4. The development of the iron electrode for Fe–air batteries was initiated in late the 1960s and these batteries still suffer from charging inefficiency, due to the unwanted hydrogen evolution reaction. Meanwhile, the air electrode is limited in long-term operation because of the sluggish oxygen evolution and reduction kinetics. These limitations of the Fe–air battery yield poor overall efficiencies, which bring vast energy losses upon cycling.Herein, the limitations described above were countered for rechargeable Zn–MnO2 and Fe–air batteries by synthesizing electrode materials and modifying electrolyte compositions. The electrolyte mixture of 1 M KOH + 3 M LiOH for rechargeable alkaline Zn–MnO2 batteries limited the formation of the inactive spinels and improved their cycle life significantly. Further, the formation of the inactive spinels was overcome in mildly acidic electrolytes containing 2 M ZnSO4, enabling the cells to cycle reversibly at lower pH via a distinctive reaction mechanism. The iron electrodes were improved with the addition of stannate, which suppressed hydrogen evolution. Furthermore, optimal charge protocols of the iron electrodes were identified to minimize the hydrogen evolution rate. On the air electrode, the synthesized NiCo2O4 showed excellent bifunctional catalytic activity for oxygen evolution and reduction, and was incorporated to a flow assisted rechargeable Fe–air battery, in order to prove the practicability of this technology. Studies of the electrode materials on the micro, macro, nano, and atomic scales were carried out to increase the understanding of the nature of and interactions between of these materials. This included both in operando and ex situ characterization. X-ray and neutron radiation, and analytical- and electrochemical methods provided insight to improve the performance and cycle life of the batteries.
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| 10. |
- Chamoun, Mylad, et al.
(författare)
-
Stannate Increases Hydrogen Evolution Overpotential on Rechargeable Alkaline Iron Electrodes
- 2017
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:6, s. A1251-A1257
-
Tidskriftsartikel (refereegranskat)abstract
- Alkaline iron electrodes present some challenges for use in secondary batteries that are associated with low coulombic efficiency and discharge utilization. Low coulombic efficiency is correlated to the hydrogen evolution reaction that takes place during charge. In this work, we demonstrate rechargeable alkaline iron electrodes with significant capacity retention over 150 cycles with high efficiency by suppressing the hydrogen evolution with stannate. Adding stannate to the alkaline electrolyte when cycling the iron electrode drastically changes the electrochemistry. The additive brings on two advantageous attributes for the iron electrode: increased hydrogen evolution overpotential, and a flat and prolonged discharge curve at typical battery operation. These attributes were provided by a novel intermediate phase that was detected from in situ neutron diffraction measurements. This phase was only detected in situ while it decomposed ex situ, and indicated a solid solution constituted by some of the elements present in the electrode.
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| 11. |
- Cuevas, Fermin, et al.
(författare)
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Metallic and complex hydride-based electrochemical storage of energy
- 2022
-
Ingår i: Progress in Energy. - : IOP Publishing. - 2516-1083. ; 4:3
-
Tidskriftsartikel (refereegranskat)abstract
- The development of efficient storage systems is one of the keys to the success of the energy transition. There are many ways to store energy, but among them, electrochemical storage is particularly valuable because it can store electrons produced by renewable energies with a very good efficiency. However, the solutions currently available on the market remain unsuitable in terms of storage capacity, recharging kinetics, durability, and cost. Technological breakthroughs are therefore expected to meet the growing need for energy storage. Within the framework of the Hydrogen Technology Collaboration Program - H2TCP Task-40, IEA's expert researchers have developed innovative materials based on hydrides (metallic or complex) offering new solutions in the field of solid electrolytes and anodes for alkaline and ionic batteries. This review presents the state of the art of research in this field, from the most fundamental aspects to the applications in battery prototypes.
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| 12. |
- Dong, Hanwu, et al.
(författare)
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An air-metal hydride battery using MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) in the anode and a perovskite in the cathode
- 2010
-
Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:9, s. 4336-4341
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen storage alloy MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) (MH) was tested as anode material in a metal hydride-air cell. The cathode was a non-noble metal air electrode based on a mixture of perovskite and pyrolyzed macrocycles on carbon. Polarization and discharge capacities of the electrodes were measured and compared at 22 degrees C and 40 degrees C using air or oxygen at the cathode. Discharge capacity reaching 330 mAh/g MH with pure oxygen at 40 degrees C and 305 mAh/g MH with air at 22 degrees C were obtained. Power densities and/or energy densities were found to significantly depend on the increase of the electrode kinetics on both the ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction). However, for air electrode, an increase of oxygen concentration by using pure oxygen gas plays a more important role than an 18 degrees C temperature increase. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
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| 13. |
- Dong, Hanwu, et al.
(författare)
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Structure and stability of high pressure synthesized MgTM2H6 (TM = Zr, Nb) hydrides
- 2015
-
Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 96, s. 237-248
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Tidskriftsartikel (refereegranskat)abstract
- The structure of two isomorphous high pressure synthesized metal hydrides MgZr2H6 and MgNb2H6 is described in the R-3m space group with the hexagonal unit cells a = 3.3592(2) angstrom, c = 25.131(3) angstrom and a = 3.2901(9) angstrom, c = 23.09(1) angstrom, respectively (Z = 3). The metal atom structures were refined from powder XRD data, with Mg in the 3a site (0, 0, 0,) and Zr and Nb in the 6c site (0, 0, z) with the only refineable atomic parameter z = 0.225 and z = 0.220, respectively. As only a minute sample could be produced in the anvil cell, a conventional structural determination with neutron diffraction on a deuterated sample could not be made. Instead formation energies of the all proposed structural models were calculated using density functional theory (DFT) for accessing the most stable structure of the lowest energy level. The measured lattice parameters and the refined atomic positional parameters from the powder X-ray diffraction pattern were reproduced well by the OFT calculation. The hydrogen atoms were found to fully occupy an octahedral site coordinated by 3Mg and 3Zr atoms, a tetrahedral site coordinated by 4Zr atoms and another tetrahedral site coordinated by 3Mg and 1Zr atoms. Chemical, mechanical and dynamical stabilities of the MgZr2H6 structure were further discussed based on a chemical potential equilibrium diagram constructed from the calculated formation energies, calculated elastic constants and phonon spectra respectively. It is also shown that a high pressure increases the stability of the new hydrides.
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| 14. |
- Fahlquist, Henrik, 1983-, et al.
(författare)
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Cs10H[Ga3H8]3 : A Hydrogenous Zintl Phase Containing Propane-Like Polyanions [Ga3H8]3- and Interstitial Hydrogen
- 2013
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 52:12, s. 7125-7129
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogenous Zintl-phase Cs10H[Ga3H8](3) containing propane-like polyanions [Ga3H(D)(8)](3-) was successfully synthesized by direct hydrogenation of a 1:1 Cs/Ga metal mixture and characterized by powder X-ray and neutron diffraction. The charge of the polyanions is balanced by two different species of cations, hydrogen-centered octahedra [H(D)Cs-6](5+) and isolated Cs+. The structure crystallizes in the hexagonal space group P6(3)/mcm (193) with the cell parameters a = 11.1108(3) angstrom, c = 18.2149(5) angstrom, Z = 2.
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| 15. |
- Fahlquist, Henrik, 1983-, et al.
(författare)
-
SrH2Mg2[Co(I)H5], BaH2Mg5[Co(-I)H4]2 and RbH2Mg5[Co(-I)H4 Ni(0)H4] illustrate how small variations in counter ions are important for the solid state stabilization of 3d-transition metal hydrido complexes as well as influencing electrical and magnetic properties
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Variations in the counter ion support to low valent 3d transition metal hydrido complexes in solids state hydrides influence formal oxidation states as well as their electrical properties. In a combined study using neutron scattering and first principle calculations a very low formal oxidation state of (-I) can be described for cobalt in a slightly distorted tetrahedral Co(-I)H4-complex in BaH2Mg5[Co(-I)H4]2 and in the structurally closely related RbH2Mg5[Co(-I)H4 Ni(0)H4]. This indicates that the electron “back donating” effect via the polarisable hydride ions to the counter ions in the solid state hydrides, can be compared to more conventional “back bonding” and reduce the oxidation state down to -I. The hydrides were synthesised by hot sintering of transition metal powders with the corresponding binary alkali- and alkaline earth hydrides. In the similarly synthesized SrH2Mg2[Co(I)H5] cobalt is formally +I-valent, showing a high sensitivity to subtle differences in the counter ion framework.
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| 16. |
- Fahlquist, Henrik, et al.
(författare)
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Stabilization of 3d Transition Metal Hydrido Complexes in SrH2Mg2[Co(I)H-5], BaH2Mg5[Co(-I)H-4](2), and RbH2Mg5[Co(-I)H4Ni(0)H-4] via Easily Polarizable Hydride Ligands
- 2016
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 55:7, s. 3576-3582
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Tidskriftsartikel (refereegranskat)abstract
- A combined study using neutron diffraction, inelastic neutron scattering, and first-principles calculations describe cobalt with a very low formal oxidation state of (-I) in a slightly distorted tetrahedral Co(-I)H-4-complex in BaH2Mg5[Co(-I)H-4](2) and in the structurally related RbH2Mg5[Co(-I)H4Ni(0)H-4]. This indicates that the electron back donating effect via the polarizable hydride ions to the counterions in the solid state hydrides, can be compared to more conventional back bonding able to reduce the oxidation state down to -I. The hydrides were synthesized by hot sintering of transition metal powders with corresponding binary alkali- and alkaline earth hydrides. In the similarly synthesized SrH2Mg2[Co(I)H-5], cobalt is formally + I-valent, showing a high sensitivity to differences in the counterion framework, which can also influence electrical properties.
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| 17. |
- Fahlquist, Henrik, et al.
(författare)
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Structural characterization of Sr4Mg4H4[CoH5](3) shows the importance of support from polarizing counter ions to 3d transition metal hydrido complexes
- 2013
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 579, s. 31-33
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Tidskriftsartikel (refereegranskat)abstract
- The structure of the title compound was refined from neutron powder diffraction data in the cubic space group P-43m (215). The unit cell contains one formula unit with 3 structurally equivalent [Co(I)H-5](4)-complexes as well as 4 interstitial hydride (H-) ions. The presence of the larger and less polarizing Sr2+ ions weakens the bond in the complexes and probably also the stability of the structure. Attempts to synthesize the corresponding Ba analogue failed in contrast to using smaller and more polarizing Ca2+ and Yb2+ counterions.
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| 18. |
- Fahlquist, Henrik, 1983-
(författare)
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Transition Metal Hydride Complexes and Hydrogenated Gallium Clusters : Synthesis and Structural Properties
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Synthesis and structural characterisation of metal hydrides in two important systems are presented. The first system presented is low valent cobalt and nickel complex hydrides with the compositions BaMg5Co2H10, RbMg5CoNiH10, SrMg2CoH7and Sr4Mg4Co3H19 featuring nickel with oxidation state of 0 and cobalt with oxidation state +I and -I. The second system presented is polyanionic gallium complex hydrides with the compositions RbGaH2, RbxK(1−x)GaH2 (0.5≤x≤1), CsxRb(8−x)Ga5H15 (0≤x≤8) and Cs10Ga9H25 featuring novel hydrogenous polyanionic gallium hydride clusters mimicking common hydrocarbons. The syntheses of the compounds were performed at elevated temperatures and at moderate hydrogen pressures (50-100 bar). The structural investigations were mainly done by X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD). The metal-hydrogen bond was investigated by vibrational spectroscopy using Fourier Transform IR-spectroscopy (FTIR) and Inelastic Neutron Scattering (INS).By subtle changes in the compositions of the hydrides it was possible to induce major changes in band gaps, oxidation states and structures.
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| 19. |
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| 20. |
- Fahlquist, Henrik, et al.
(författare)
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Varying the Alkali-Metal Radii in (KxRb1−x)n[GaH2]n (0 ≤ x ≤ 1)Reorients a Stable Polyethylene-Structured [GaH2]nn− Anionic Chain
- 2013
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 52:9, s. 4771-4773
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Tidskriftsartikel (refereegranskat)abstract
- The stability of a negatively chargedpolyethylene-structured [GaH2]nn−cluster ion was inves-tigated by varying the K+/Rb+ratio in (KxRb1−x)n[GaH2]n(0≤x≤1). Neutron, X-ray, and IR spectroscopies wereused to characterize the new phases. Between the limitingcompositions Kn[GaH2]nand Rbn[GaH2]n, the [GaH2]nn−chains remained almost identical, indicating a stable specie.For rubidium-rich samples up to a potassium contentcorresponding to (K0.5Rb0.5)n[GaH2]n, two phases coexistin the samples, RbGaH2and (K0.5Rb0.5)n[GaH2]n, with aratio mirroring the relative alkali-ion content. The twophases have a different alignment of the [GaH2]nn−chains.For potassium-rich samples beyond (K0.5Rb0.5)n[GaH2]n,the samples were single-phased. The unit cell volume ofthe new (K0.5Rb0.5)n[GaH2]nstructure type shrinksaccording to Vegard’s law as smaller K+ions substitutefor larger Rb+ions. The [GaH2]nn−chains remained,however, almost identical. IR spectra from the differentphases were very similar, exhibited stretching, scissoring,and rocking modes similar to those in ordinary poly-ethylene, but shifted to lower frequencies, reflectingweaker Ga−H bonds. The existence of stable Kn[GaH2]nand Rbn[GaH2]n, would help to dehydrogenate KGaH4and RbGaH4upon heating. If this could be transferred tolighter alanates and borohydrides, it could be possible todevelop more functional hydrogen-storage systems.
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| 21. |
- Hirscher, Michael, et al.
(författare)
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Materials for hydrogen-based energy storage - past, recent progress and future outlook
- 2020
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 827
-
Tidskriftsartikel (refereegranskat)abstract
- Globally, the accelerating use of renewable energy sources, enabled by increased efficiencies and reduced costs, and driven by the need to mitigate the effects of climate change, has significantly increased research in the areas of renewable energy production, storage, distribution and end-use. Central to this discussion is the use of hydrogen, as a clean, efficient energy vector for energy storage. This review, by experts of Task 32, Hydrogen-based Energy Storage of the International Energy Agency, Hydrogen TCP, reports on the development over the last 6 years of hydrogen storage materials, methods and techniques, including electrochemical and thermal storage systems. An overview is given on the background to the various methods, the current state of development and the future prospects. The following areas are covered; porous materials, liquid hydrogen carriers, complex hydrides, intermetallic hydrides, electrochemical storage of energy, thermal energy storage, hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage.
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| 22. |
- Hu, Weikang, et al.
(författare)
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Boosting the performance of Zn-air cells by spinel catalysts with bimodal pore structure and gill filament configuration
- 2023
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 936
-
Tidskriftsartikel (refereegranskat)abstract
- Spinel oxides with specific morphology are importantly multifunctional materials for various applications. Here we report various morphological spinel oxides with one and two-modal pore size structures. The surface microstructure, phase composition, specific surface areas and electrocatalytic OER/ORR activities are examined. The results reveal that the bicomponent (NiCo2O4 and Co3O4) spinel exhibits a bimodal pore size distribution, high specific surface area, good OER activity (an overpotential of 313 mV at 10 mA cm−2Geo) and low Tafel slope of 73.1 mV dec−1. The Co3O4 component presents a perforated sheet morphology similar to an ancient window configuration with regular hole patterns, which benefits for mass transfer and O2 bubble detachment. By comparison, the single-component NiCo2O4 spinel having the morphology of more open self-assembled nanoneedle spheres or nanorod clusters, similar to the configuration of fish gill filaments, shows better ORR activities. The morphology, similar to the fish gills, can readily capture dissolved oxygen molecules from the film electrolyte at the three-phase interface and improve ORR performance. In addition, calcination temperatures also significantly affect pore structure, surface areas, and electrocatalytic activities. Finally, small Lab size Zn-air cells are assembled using thin flexible air electrodes with the self-assembled nanoneedle NiCo2O4 catalysts. Electrochemical charging-discharging performance and cycling durability are evaluated.
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| 23. |
- Hu, Wei-Kang, et al.
(författare)
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Lab-size rechargeable metal hydride-air cells
- 2010
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 195:17, s. 5810-5813
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Tidskriftsartikel (refereegranskat)abstract
- Lab-size rechargeable metal hydride-air (MH-air) cells with a gas management device were designed in order to minimize the loss of electrolyte. An AB(5)-type hydrogen storage alloy was used as anode materials of the MH-air. The thickness of the metal hydride electrodes was in the range of 3.0-3.4 mm. Porous carbon-based air electrodes with Ag2O catalysts were used as bi-functional electrodes for oxygen reduction and generation. The electrodes were first examined in half-cells to evaluate their performance and then assembled into one MH-air cell. The results showed the good cycling stability of the rechargeable MH-air cell with a capacity of 1990 mAh. The discharge voltage was 0.69 V at 0.05-0.1 C. The charge efficiency was about 90%. The specific and volumetric energy densities were about 95 Wh kg(-1) and 140 Wh L-1, respectively.
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| 24. |
- Hu, Wei-kang, et al.
(författare)
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Metal hydrides as bi-functional catalysts for hydrogen generation and oxidation in reversible MH-air fuel cells.
- 2009
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Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 11:11, s. 2212-
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Tidskriftsartikel (refereegranskat)abstract
- Two kinds of metal hydride alloys as the bi-functional catalyst concept for hydrogen generation and oxidation in hydrogen-diffusion electrodes were investigated. The AB5-type hydride electrode shows much higher catalytic activities than the Zr-based AB2-type hydride electrode. However, the activity of Zr-based hydride electrodes can be improved only after removal of zirconium oxides on surface by a 1.0 M HF solution. The experiments demonstrated that the both metal-hydride hydrogen-diffusion electrodes for cycles of hydrogen generation (12 h) and oxidation (12 h) had good stability under the current densities of 100 and 50 mA/cm2, respectively. The results also showed that small amounts of oxygen below 500 ppm and moisture up to 145,000 ppm in the hydrogen gas have little effect on the activity. It indicated that the hydride alloys as the non-noble-metal bi-functional catalysts in a reversible MH-air fuel cell have potential applications.
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| 25. |
- Jensen, Emil H., et al.
(författare)
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The Effect of Y Content on Structural and Sorption Properties of A2B7-Type Phase in the La–Y–Ni–Al–Mn System
- 2023
-
Ingår i: Molecules. - 1431-5157 .- 1420-3049. ; 28:9
-
Tidskriftsartikel (refereegranskat)abstract
- Metal hydrides are an interesting group of chemical compounds, able to store hydrogen in a reversible, compact and safe manner. Among them, A2B7-type intermetallic alloys based on La-Mg-Ni have attracted particular attention due to their high electrochemical hydrogen storage capacity (∼400 mAh/g) and extended cycle life. However, the presence of Mg makes their synthesis via conventional metallurgical routes challenging. Replacing Mg with Y is a viable approach. Herein, we present a systematic study for a series of compounds with a nominal composition of La2-xYxNi6.50Mn0.33Al0.17, x = 0.33, 0.67, 1.00, 1.33, 1.67, focusing on the relationship between the material structural properties and hydrogen sorption performances. The results show that while the hydrogen-induced phase amorphization occurs in the Y-poor samples (x < 1.00) already during the first hydrogen absorption, a higher Y content helps to maintain the material crystallinity during the hydrogenation cycles and increases its H-storage capacity (1.37 wt.% for x = 1.00 vs. 1.60 wt.% for x = 1.67 at 50 °C). Thermal conductivity experiments on the studied compositions indicate the importance of thermal transfer between powder individual particles and/or a measuring instrument.
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| 26. |
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| 27. |
- Kadir, Abdulkarim, et al.
(författare)
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Investigation of Counterion Influence on an Octahedral IrH(6)-Complex in the Solid State Hydrides AAeIrH(6) (A = Na, K and Ae = Ca, Sr, Ba, and Eu) with a New Structure Type
- 2011
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 50:23, s. 11890-11895
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Tidskriftsartikel (refereegranskat)abstract
- A number of new quaternary iridium based hydrides and deuterides AAeIrH/D(6) (where A = Na and K; Ae = Ca, Ba, Sr, and Eu) have been synthesized by direct combination of the alkali, alkaline earth or europium binary hydrides/deuterides and iridium powder. The crystal structures were determined by Guinier-Hagg X-ray and neutron powder diffraction and a new cubic structure type was found. The structure is described in space group F (4) over bar 3m, but related to the K(2)PtCl(6) type structure. The new structure can be described as consisting of cubes of A(+) and Ae(2+) ions, where the A(+) and Ae(2+) ions alternates so that they occupy opposite corners in the cube. Every second cube contains a regular octahedral [Ir(III)H(6)](-3)-complex and the adjacent is empty. Solid-state IR spectroscopy was used to determine the Ir-allowed stretching and bending frequencies for the [Ir(III)H(6)](-3) complex with different counterions. These were also compared with the corresponding stretching frequencies for Fe(II)H(6), Ru(II)H(6), Os(II)H(6), and Ir(II)H(5) complexes in similar solid state hydrides, which increased when going from Fe through Ru, Os to Ir. The frequencies scaled almost linearly with the inverse of size of the cube surrounding the complexes but showed no significant dependence of the formal oxidation state or the experimentally obtained Ir-D distances. However, this was mainly because of difficulties in obtaining enough accurate atomic positions. The ab initio DFT calculations could reproduce the stretching frequencies within a few 10 cm(-1), indicating that experimental vibrational frequencies offer a sensitive test of DFT results.
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| 28. |
- Kadir, Abdulkarim, et al.
(författare)
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Structural determination of NaAl2Ga2 intermetallic compound having the ThCr2Si2 type structure.
- 2009
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 477:1-2, s. 149-151
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Tidskriftsartikel (refereegranskat)abstract
- NaAl2Ga2 intermetallic compound has been synthesized by direct combination of the elements in the atomic ratio Na:Ga:Al = 1:2:2. Guinier–Hägg X-ray and neutron powder diffraction determined a ThCr2Si2 type structure for the new compound with tetragonal unit cell axis a = 4.1817(5) and c = 11.388(2) Å.
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| 29. |
- Lee, Myeong H., et al.
(författare)
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Crystal structure, electronic structure, and vibrational properties of MAlSiH (M=Ca,Sr,Ba) : Hydrogenation-induced semiconductors from the AlB2-type alloys MAlSi
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78:19, s. 195209-
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Tidskriftsartikel (refereegranskat)abstract
- Superconducting AlB2-type silicides CaAlSi, SrAlSi, and BaAlSi (MAlSi) absorb hydrogen and form semiconducting monohydrides where hydrogen is exclusively attached to Al. This induces a metal-nonmetal transition which is accompanied with only a minor rearrangement of the metal atoms. We report the synthesis and structure determination of CaAlSiH and BaAlSiH as well as a first-principles study of the electronic structure and vibrational property changes associated with the metal-nonmetal transition. We find that incorporation of H in MAlSi removes the partly occupied antibonding pi(*) band responsible for metallic behavior and turns it into an energetically low-lying Al-H bonding band. The fully occupied bonding pi band in MAlSi changes to a weakly dispersed band with Si p(z) (lone-pair) character in the hydrides, which becomes located below the Fermi level. The soft phonon mode in MAlSi pivotal for the superconducting properties stiffens considerably in the hydride. This mode is associated with the out-of-plane Al-Si vibration and is most affected by the formation of the Al-H bond. The mode of the Al-Si in-plane vibration, however, is unaffected, indicating that the Al-Si bond is equally strong in the metallic precursor and the semiconducting hydride. Al-H modes for MAlSiH are weakly dispersed. The frequencies of the stretching mode are around 1200 cm(-1) and virtually invariant to the M environment, indicating a covalent but weak Al-H interaction, which is interpreted as a dative bond from hydridic hydrogen to Al [Al <- H1-].
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| 30. |
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| 31. |
- Lelis, Martynas, et al.
(författare)
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A mechanically switchable metal-insulator transition in Mg2NiH4 discovers a strain sensitive, nanoscale modulated resistivity connected to a stacking fault
- 2010
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 496:02-jan, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- The band gap in semiconducting Mg2NiH4 was found to be dependent on subtle structural differences. This was discovered when investigating if thin film samples of Mg2NiH4 could be used in a switchable mirror or window device by utilizing a high to low temperature transition at about 510K. In powder samples; this transition between an FCC high temperature phase, with dynamically disordered NiH4-complexes, and a monoclinic distorted low temperature phase, with ordered Mg2NiH4-complexes, has been demonstrated in a mechanical reversible conductor-insulator transition (Blomqvist and Noreus (2002) [7]). Black monoclinic Mg2NiH4 powders were found to have a band gap of 1.1 eV. Pressed tablets of black monoclinic Mg2NiH4 powders are conductive, probably from doping by impurities or non-stoichiometry. Thin film Mg2NiH4 samples were produced by reacting hydrogen with magnetron sputtered Mg2Ni films on quartz glass or CaF2 substrates. The Mg2NiH4 films on the other hand were orange, transparent with a band gap of 2.2 eV and a cubic unit cell parameter almost identical to the disorder HT phase but with lower symmetry. If black Mg2NiH4 powder is heated above the phase transition at 510K and subsequently cooled down, the conductivity is lost and the powder turns brown. After this heat treatment TEM pictures revealed a multiple stacking fault having a local pseudo-cubic arrangement separating regions of monoclinic symmetry. The loss of conductivity and colour change is attributed to a higher band gap in the strained areas. The structure on each side of the stacking fault is related by a mirror plane as a consequence of the possibility for the NiH4-complexes to order with different orientations. This leads to a mismatch in the long range ordering and strain is probably creating the stacking faults. Strain is important for forming the cubic modification. A severely strained film was revealed with optical microscopy in reflected light, indicating that strain prevents it from relaxing back into the monoclinic structure. This was supported by multiple twinned red translucent Mg2NiH4 crystals grown with cubic symmetry at elevated temperatures in a LiH flux. When cooled to ambient conditions, the ""crystals"" had the same cubic symmetry as the films, probably held together by their neighbours. When they were ground to a fine powder to prepare TEM samples, they relaxed and reverted back to the conventional monoclinic unit cell. This interesting nanoscale modulated resistance could possibly be developed into novel memory devices if properly controllable.
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| 32. |
- Lelis, Martynas, et al.
(författare)
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Substrate effects on formation and hydrogenation of Mg-Ni films
- 2012
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 263, s. 202-209
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Tidskriftsartikel (refereegranskat)abstract
- Usually metallic films for metal hydrides research applications are deposited on hard and flat substrates such as silicon, magnesium oxide, fused silica or quartz glass. With the film thickness increases all films during hydrogenation deals with typical problems such as film brittleness and cracking. In this paper we demonstrate that metal Mg-Ni films for hydrogen storage can be successfully deposited on to the flexible low surface energy expanded PTFE substrates. The received results for soft substrates (expanded PTFE) are compared to films being deposited on crystalline silicon substrate with and without plasma pretreatment. It is observed that different interface zone between substrate and film has great affect on both film crystallinity and its reaction with hydrogen. It is also demonstrated that modifying surface of the substrate might have affect on film microstructure before and after hydrogenation.
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| 33. |
- Ma, Honglei, et al.
(författare)
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Synchrotron X-ray diffraction and infrared spectroscopy studies of C60H18 under high pressure
- 2010
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society. - 1948-7185. ; 1:4, s. 714-719
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Tidskriftsartikel (refereegranskat)abstract
- In situ high-pressure angle-dispersive synchrotron X-ray diffraction and high-pressure mid-infrared (IR) spectrum measurements of C60H18 were carried out up to 32 and 10.2 GPa, respectively. Our diffraction data indicated that the fcc structure of C60H18 was stable up to 32 GPa. The bulk modulus B0 was determined to be 21 ± 1.16 GPa, about 40% higher than that of C60. The C−H vibrations still existed up to 10.2 GPa, and the vibrational frequencies decreased with increasing pressure. IR-active vibrational frequencies and their corresponding eigenvectors of C60H18 were simulated by DMOL3. The effects of the hydrogen atoms attached to the fullerene molecular cage on the stability of the structure under high pressure are discussed.
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| 34. |
- Moser, D., et al.
(författare)
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An in situ neutron diffraction measurement of the pressure-temperature evolution of a MgD2:TiD2 mixture
- 2010
-
Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 30:4, s. 643-652
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen storage capacity of Mg-Ti-H films is approximately five times that of conventional metal hydride electrodes in NiMH-batteries. Mg and Ti are considered to be immiscible in the bulk and the ambient pressure phase diagram of Mg and Ti indicates that no binary stable bulk compounds are formed. However, in the presence of hydrogen, an Mg-Ti-H phase has been obtained by Kyoi et al. using a high pressure synthesis - where magnesium hydride is compacted with different TM-hydrides in an anvil cell at pressures of the order several GPa (4-8GPa) and at a temperature of 873K. In this work, we have proved the feasibility of in situ powder diffraction using the Paris-Edinburgh high pressure cell for the observation of structural changes on this system and we propose modifications to improve the output of the experiment.
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| 35. |
- Moser, D., et al.
(författare)
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The pressure-temperature phase diagram of MgH(2) and isotopic substitution
- 2011
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 23:30, s. 305403-
-
Tidskriftsartikel (refereegranskat)abstract
- Computational thermodynamics using density functional theory ab initio codes is a powerful tool for calculating phase diagrams. The method is usually applied at the standard pressure of p = 1 bar and where the Gibbs energy is assumed to be equal to the Helmholtz energy. In this work, we have calculated the Gibbs energy in order to study the release temperature and phase modifications of MgH(2) at high pressures up to 10 GPa (100 kbar). The isotopic substitution of hydrogen with deuterium (or tritium) does not bring about any strong effects on the phase diagram. These considerations are of extreme importance for (i) the synthesis of novel substitutional magnesium based materials at high pressure and (ii) the determination of the correct reference states for the calculation of phase diagrams at high pressure. The calculated results are compared with experimental data obtained with an in situ neutron diffraction measurement.
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| 36. |
- Parker, Stewart F., et al.
(författare)
-
Preface
- 2011
-
Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 151, s. 9-9
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Tidskriftsartikel (refereegranskat)
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| 37. |
- Paulraj, Alagar Raj, et al.
(författare)
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Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
- 2019
-
Ingår i: Batteries. - : MDPI. - 2313-0105. ; :1
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.
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| 38. |
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| 39. |
- Sato, Toyoto, 1978-
(författare)
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Novel Interstitial Mg–TM (TM = Ti, Zr, Hf, V, Nb and Ta) Hydrides with an FCC Structure and CaNiH3 with a Perovskite Structure
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is focused on structural investigations of novel interstitial ternary alkaline-earth–transition metal hydrides formed by immiscible metals that are held together by the presence of hydrogen atoms. The contents are divided in two parts: Metastable Mg-based hydrides, in which transition-metal additives improve hydrogen storage properties; and a new Ca–Ni hydride, CaNiH3, with a perovskite structure, in which hydrogen enables a Ca:Ni =1:1 ratio although no such alloy composition exists.New ternary Mg-based hydride with an additive of either Ti, Zr, Hf, V, Nb or Ta were synthesized in a high-pressure anvil cell at 4–8 GPa and 600 ºC. All hydrides had an FCC metal atom structure with an axis of about 4.8 Å. This corresponds to an assumed high-pressure MgH2 phase that is stable at a pressure above 3.6 GPa (P. Vajeeston, P. Ravindran, A. Kjekshus, H. Fjellvåg, Phys. Rev. Lett. 89 (2002) 175506). Ordering of the metal atoms in the lattice leads to a doubling of the FCC unit cell all axis, and the metal atom structure of the hydrides (excluding Zr doped hydride) can be described by the Ca7Ge-type structure. Hydrogen atom arrangements at two tetrahedral sites were found from a powder X-ray diffraction pattern obtained with synchrotron radiation. One of the tetrahedral sites coordinates one TM atom and three Mg atoms, and the other coordinates four Mg atoms.CaNiH3 crystallizes with a cubic unit cell: a = 3.544(1) Å, V = 44.51(4) Å3 and Z = 1 in space group Pm-3m (No. 221). The hydrogen positions were determined from CaNiD3, using powder neutron diffraction, and the hydride was of an ideal perovskite ABH3 type. It was stabilized by a polyanionic framework of [NiH3]2- counterbalanced by Ca2+ cations. Total-energy calculations of the electronic structure showed that the hydride was a metallic conductor due to a half-filled Ni-H antibonding eg band.
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| 40. |
- Sato, Toyoto, et al.
(författare)
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Structural investigations of two new ternary magnesium–niobium hydrides, Mg6.5NbH~14 and MgNb2H~4
- 2006
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 417:1-2, s. 230-234
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Tidskriftsartikel (refereegranskat)abstract
- Two new magnesium–niobium hydrides, Mg6.5NbH14 with a face centred cubic unit cell a = 9.548(1) Å (space group (No. 225), Z = 4, V = 870.49 Å3) and MgNb2H4 with a C-centred monoclinic unit cell a = 5.685 (4) Å, b = 3.2914(6) Å, c = 7.924(2) Å and β = 103.82(3)° (space group C2/m (No. 12), Z = 2, V = 143.98 Å3), were synthesized by reacting MgH2 and Nb in a high-pressure anvil cell at 8 GPa and 600 °C. The structures of the new hydrides were refined from synchrotron radiation data. Mg6.5NbH14 has a structure related to Mg7TiH16 (a = 9.532(2) Å space group (No. 225)) (D. Kyoi, T. Sato, E. Rönnebro, N. Kitamura, A. Ueda, M. Ito, S. Katsuyama, S. Hara, D. Noréus, T. Sakai, J. Alloys Compd. 372 (2004) 213). Where the metal atom structure is of the Ca7Ge type. Mg6.5NbH14, however, has some vacancies on one of the magnesium sites similar to the recently discovered Mg6VH14 (D. Kyoi, T. Sato, E. Rönnebro, Y. Tsuji, N. Kitamura, A. Ueda, M. Ito, S. Katsuyama, S. Hara, D. Noréus, T. Sakai, J. Alloys Compd. 375 (2004) 253). The metal atoms in MgNb2H4 have the AuTe2 type structure.
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| 41. |
- Shen, Yang, 1988-
(författare)
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Development of metal hydride surface structures for high power NiMH batteries : Also extended cycle-life and lead to more effective recycling methods
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- By combining alkaline etching of hydrogen storage alloys or their hydrides with a controlled oxidation, it was possible to improve reaction kinetics and accelerate activation of MH-electrodes. Both AB5 and AB2 alloys were studied where A is mixtures of rare earth elements for AB5 alloys and titanium and/or vanadium, zirconium for AB2 alloys; nickel contributes the major part of B. With SEM and TEM studies the surface could be described as consisting of several phases where an interphase with active Ni-containing cluster protected the inner metallic hydrogen storage part of the powder particles. These catalytic Ni-clusters presumably lead to the fast activation and high discharge capacity of alloy.This interphase was observed to be stable enough to allow us to develop a method, where we could add pure oxygen to a NiMH battery pack in order to regenerate the amount of electrolyte that was lost during long time cycling of the battery. Meanwhile, the method will rebalance the electrodes mitigating excessive pressures during over charge. Therefore, the internal resistance of cells can be reduced and cycle life will increase.It was also shown that the stable interphase could survive a mild ball milling or sonication which enabled us to upcycle material from spent NiMH batteries into a better working MH-electrodes with improved kinetics and activation properties. Reuse of ball-milled or sonicated material could serve as a simple recycling alternative to energy-demanding metallurgical smelting methods and chemical consuming hydrometallurgical recycling processes, where the possibilities of up-scaling further favour the less complex mechanical treatments. The stable but catalytic interphase protecting the inner particles indicates that the MH-electrode material may perform better in its second life in a new NiMH battery.
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| 42. |
- Shen, Yang, et al.
(författare)
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Improved NiMH performance by a surface treatment that creates magnetic Ni-clusters
- 2016
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 41:23, s. 9933-9938
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Tidskriftsartikel (refereegranskat)abstract
- A surface treatment method has been developed to activate the surface of an AB(5) type (La-20 Ce-7 Pr-1 Nd-4 Al-2 Mn-5 Co-6 Ni-55) alloy. In the process the surface is covered with a porous surface layer containing needle shaped rare earth hydroxides after etching by a potassium hydroxide solution. TEM studies show in addition the presence of a denser surface oxide layer with embedded Ni containing clusters covering the bulk alloy. The magnetic properties of the alloy powders change with the surface treatment. In addition to a paramagnetic component of the bulk alloy, surface treated alloy also displays superparamagnetic and ferromagnetic properties. In electrochemical half-cell tests, the alloy shows better high-rate dischargeability with increasing presence of magnetic clusters in the metal hydride particles surface.
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| 43. |
- Shen, Yang, et al.
(författare)
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Increasing NiMH battery cycle life with oxygen
- 2018
-
Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 43:40, s. 18626-18631
-
Tidskriftsartikel (refereegranskat)abstract
- Nickel-Metal Hydride batteries (NiMH) have long cycle life. But in the end corrosion of the metal hydride is detrimental for life expectancy. Corrosion reduces the metal hydride capacity, but more severely it consumes water in the electrolyte resulting in increased internal resistance, which is the main cause for cell failure.The corrosion, further, evolves hydrogen, causing an unbalance between anode and cathode, leading to premature internal pressure increase when the cells are approaching end of charge. This accelerates the drying out, if the cells vent through the safety valve.In this study, a controlled addition of oxygen was used to rebalance the electrodes and replenish the electrolyte – as the added oxygen reacts with hydrogen that was formed during the corrosion process. Thus, the two most detrimental factors in cell ageing can be mitigated. To fully restore the electrolyte content as well as electrode balance, both oxygen and hydrogen are needed to compensate for the loss to hydroxide ions OH− formed in the corrosion process. A proper optimization of the gas additions combined with a cell design including an excess amount of MH-alloy to compensate for the corrosion can substantially increase the cycle life of NiMH batteries.
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| 44. |
- Shen, Yang, et al.
(författare)
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Upcycling of Spent NiMH Battery Material-Reconditioned Battery Alloys Show Faster Activation and Reaction Kinetics than Pristine Alloys
- 2020
-
Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 25:10
-
Tidskriftsartikel (refereegranskat)abstract
- During formation and cycling of nickel-metal hydride (NiMH cells), surface corrosion on the metal hydride particles forms a porous outer layer of needle-shaped rare-earth hydroxide crystals. Under this layer, a denser but thinner oxidized layer protects the inner metallic part of the MH electrode powder particles. Nano-sized nickel-containing clusters that are assumed to promote the charge and discharge reaction kinetics are also formed here. In this study, mechanical treatments are tested to recycle hydrogen storage alloys from spent NiMH batteries. This removes the outer corroded surface of the alloy particles, while maintaining the catalytic properties of the surface. Scanning electron microscopy images and powder X-ray diffraction measurements show that the corrosion layer can be partly removed by ball milling or sonication, combined with a simple washing procedure. The reconditioned alloy powders exhibit improved high rate properties and activate more quickly than the pristine alloy. This indicates that the protective interphase layer created on the alloy particle during their earlier cycling is rather stable. The larger active surface that is created by the mechanical impact on the surface by the treatments also improves the kinetic properties. Similarly, the mechanical strain during cycling cracks the alloy particles into finer fragments. However, some of these particles form agglomerates, reducing the accessibility for the electrolyte and rendering them inactive. The mechanical treatment also separates the agglomerates and thus further promotes reaction kinetics in the upcycled material. Altogether, this suggests that the MH electrode material can perform better in its second life in a new battery.
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| 45. |
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| 46. |
- Talyzin, Alexandr, 1969-, et al.
(författare)
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Hydrogenation, Purification, and Unzipping of Carbon Nanotubes by Reaction with Molecular Hydrogen : Road to Graphane Nanoribbons
- 2011
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 5:6, s. 5132-5140
-
Tidskriftsartikel (refereegranskat)abstract
- Reaction of single-walled carbon nanotubes (SWNTs) with hydrogen gas was studied in a temperature interval of 400-550 degrees C and at hydrogen pressure of 50 bar. Hydrogenation of nanotubes was observed for samples treated at 400-450 degrees C with about 1/3 of carbon atoms forming covalent C-H bonds, whereas hydrogen treatment at higher temperatures (550 degrees C) occurs as an etching. Unzipping of some SWNTs Into graphene nanoribbons is observed as a result of hydrogenation at 400-550 degrees C Annealing in hydrogen gas at elevated conditions for prolonged periods of time (72 h) is demonstrated to result also in nanotube opening, purification of nanotubes from amorphous carbon, and removal of carbon coatings from Fe catalyst particles, which allows their complete elimination by acid treatment.
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| 47. |
- Talyzin, Alexandr, et al.
(författare)
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Reaction of hydrogen gas with C60 at elevated pressure and temperature: Hydrogenation and cage fragmentation.
- 2006
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 110:27, s. 8528-34
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Tidskriftsartikel (refereegranskat)abstract
- Products of the reaction of C60 with H2 gas have been monitored by high-resolution atmospheric pressurephotoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS), X-raydiffraction, and IR spectroscopy as a function of hydrogenation period. Samples were synthesized at 673 Kand 120 bar hydrogen pressure for hydrogenation periods between 300 and 5000 min, resulting in the formationof hydrofullerene mixtures with hydrogen content ranging from 1.6 to 5.3 wt %. Highly reduced C60Hx (x >36-40) and products of their fragmentation were identified in these samples by APPI FT-ICR MS. A sharpchange in structure was observed for samples with at least 5.0 wt % of hydrogen. Low-mass (300-500 Da)hydrogenation products not observed by prior field desorption (FD) FT-ICR MS were detected by APPIFT-ICR MS and their elemental compositions obtained for the first time. Synthetic and analytical fragmentationpathways are discussed.
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| 48. |
- Tan, Semra, et al.
(författare)
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Activation behavior of an AB(2) type metal hydride alloy for NiMH batteries
- 2016
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 41:23, s. 9948-9953
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Tidskriftsartikel (refereegranskat)abstract
- Activation behavior of an AB(2), namely (Ti0.36Zr0.64) (V0.15Ni0.58Mn0.20Cr0.07)(2) Laves phase alloy, was investigated with regards to; particle size, ball milling and hot alkaline treatments. Galvanostatic cycling in open cells showed that an untreated alloy initially had almost no capacity, but reached a value of 220 mAh/g after 14 cycles. Experiments with different particle sizes showed that coarse particles activate faster yielding an improved capacity. In terms of activation more pronounced effect was obtained with boiling the alloy powder in a hot KOH solution. A capacity in excess of 300 mAh/g is reached in the first cycle after a 20 min treatment. The capacity was highest after 80 min, yielding a value of 390 mAh/g well above that expected from the gas-phase storage in the alloy. This was attributed to the formation of rough surface in the powder, which may stabilize hydrogen bubbles allowing pressures above 1 atm to be reached locally in the surface.
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| 49. |
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| 50. |
- Wågberg, Thomas, et al.
(författare)
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Selective synthesis of the C3v-isomer of C60H18
- 2005
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 7:25, s. 5557-60
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Tidskriftsartikel (refereegranskat)abstract
- C60H18 has been produced by hydrogenation of C-60 at 100 bar H-2 pressure and 673 K for 10 h. We have investigated the crude material without any purification by use of H-1 NMR, C-13 NMR, and IR spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry. We show that the crude material consists of 95% of the C-3v isomer of C60H18.
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