| 1. |
- Arge, Tummas Napoleon, et al.
(författare)
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Measuring structural inhomogeneity of a helical conjugated polymer at high pressure and temperature
- 2019
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Ingår i: Journal of Polymer Science, Part B: Polymer Physics. - : Wiley. - 0887-6266. ; 57:7, s. 392-396
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Tidskriftsartikel (refereegranskat)abstract
- We report on X-ray scattering measurements of helical poly[9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl] by mapping the sample with 10 μm spatial resolution from 0.3 GPa to 36 GPa. We follow the strongest 00l reflection, which moves toward higher scattering angles with pressure indicating planarization of helical polyfluorene. Lateral inhomogeneity is increased for >10 GPa concomitant with the solidification of the pressure transmitting medium (a 4:1 mixture of methanol and ethanol). We also follow the 00l reflection with increasing temperature at the constant pressure of 4.3 GPa in neon. We observe a sharp shift toward higher scattering angles indicative of a phase transition at 167–176 °C.
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| 2. |
- Cerny, Radovan, et al.
(författare)
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NaSc(BH4)(4): A Novel Scandium-Based Borohydride
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:2, s. 1357-1364
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Tidskriftsartikel (refereegranskat)abstract
- A new alkaline transition-metal borohydride, NaSc(BH4)(4), is presented. The compound has been studied using a combination of in situ synchrotron radiation powder X-ray diffraction, thermal analysis, and vibrational and NMR spectroscopy. NaSc(BH4)(4) forms at ambient conditions in ball-milled mixtures of sodium borohydride and ScCl3. A new tertiary chloride Na3ScCl6 (P2(1)/n, a = 6.7375(3) angstrom, b = 7.1567(3) angstrom, c = 9,9316(5) angstrom, beta = 90.491(3)degrees, V = 478.87(4) angstrom(3)), isostructural to Na3TiCl6, was identified as an additional phase in all samples. This indicates that the formation of NaSc(BH4)(4) differs from a simple metathesis reaction, and the highest scandium borohydride yield (22 wt %) was obtained with a reactant ratio of ScCl3/NaBH4 of 1:2. NaSc(BH4)(4) crystallizes in the orthorhombic crystal system with the space group symmetry Cmcm (a = 8.170(2) angstrom, b = 11.875(3) angstrom, c = 9.018(2) angstrom, V = 874.9(3) angstrom(3)). The Structure of NaSc(BH4)(4) consists of isolated homoleptic scandium tetraborohydride anions, [Sc(BH4)(4)](-), located inside slightly distorted trigonal Na-6 prisms (each second prism is empty, triangular angles of 55.5 and 69.1 degrees). The experimental results show that each Sc3+ is tetrahedrally Surrounded by four BH4 tetrahedra with a 12-fold coordination of H to Sc, while Na+ is surrounded by six BH4 tetrahedra in a quite regular octahedral coordination with a (6 + 12)-fold coordination of H to Na. The packing of Na+ cations and [Sc(BH)(4))(4)](-) anions in NaSc(BH4)(4) is a deformation variant of the hexagonal NiAs structure type. NaSc(BH4)(4) is stable from RT up to similar to 410 K, Where the compound melts and then releases hydrogen in two rapidly occurring steps between 440 and 490 K and 495 and 540 K. Thermal expansion of NaSc(BH4)(4) between RT and 408 K is anisotropic, and lattice parameter b shows strong anomaly close to the melting temperature.
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| 3. |
- Cerny, Radovan, et al.
(författare)
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Structure and Characterization of KSc(BH4)(4)
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:45, s. 19540-19549
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Tidskriftsartikel (refereegranskat)abstract
- A new potassium scandium borohydride, KSc(BH4)(4), is presented and characterized by a combination of in situ synchrotron radiation powder X-ray diffraction, thermal analysis, and vibrational and NMR spectroscopy. The title compound, KSc(BH4)(4), forms at ambient conditions in ball milled mixtures of potassium borohydride and ScCl3 together with a new ternary chloride K3ScCl6, which is also structurally characterized. This indicates that the formation of KSc(BH4)(4) differs from a simple metathesis reaction, and the highest scandium borohydride yield (similar to 31 mol %) can be obtained with a reactant ratio KBH4:ScCl3 of 2:1. KSc(BH4)(4) crystallizes in the orthorhombic crystal system, a = 11.856(5), b = 7.800(3), c = 10.126(6) angstrom, v = 936.4(8) angstrom(3) at RT, with the space group symmetry Prima. KSc(BH4)(4) has a BaSO4 type structure where the BH4 tetrahedra take the oxygen positions. Regarding the packing of cations, K+, and complex anions, [Sc(BH4)(4)](-), the structure of KSc(BH4)(4) can be seen as a distorted variant of orthorhombic neptunium, Np, metal. Thermal expansion of KSc(BH4)(4) in the temperature range RT to 405 K is anisotropic, and the lattice parameter b shows strong nonlinearity upon approaching the melting temperature. The vibrational and NMR spectra are consistent with the structural model, and previous investigations of the related compounds ASc(BH4)(4) with A = Li, Na. KSc(BH4)(4) is stable from RT up to similar to 405 K, where the compound melts and then releases hydrogen in two rapid steps approximately at 460-500 K and 510-590 K. The hydrogen release involves the formation of KBH4, which reacts with K3ScCl6 and forms a solid solution, K(BH4)(1-x)Cl-x. The ternary potassium scandium chloride K3ScCl6 observed in all samples has a monoclinic structure at room temperature, P2(1)/a, a = 12.729(3), b = 7.367(2), c = 12.825(3) angstrom, beta = 109.22(2)degrees, V = 1135.6(4) angstrom(3), which is isostructural to K3MoCl6. The monoclinic polymorph transforms to cubic at 635 K, a = 10.694 angstrom (based on diffraction data measured at 769 K), which is isostructural to the high temperature phase of K3YCl6.
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| 4. |
- Fornell, Anna, et al.
(författare)
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A Microfluidic Platform for Synchrotron X-ray Studies of Proteins
- 2021
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Konferensbidrag (refereegranskat)abstract
- New tools are needed to allow for complex protein dynamics studies, especially to study proteins in their native states. In the AdaptoCell project a microfluidic platform for academic and industrial users at MAX IV Laboratory is being developed. MAX IV is a Swedish national laboratory providing brilliant synchrotron X-rays for research. Due to the high photon flux, sensitive samples such as proteins are prone to rapid radiation damage; thus, it is advantageous to have the liquid sample underflow to refresh the sample continuously. This, in combination with small volumes, makes microfluidics a highly suitable sample environment for protein studies at MAX IV. The AdaptoCell platform is being integrated at three beamlines:Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and Micromax (serial synchrotron crystallography). Currently, the platform is fully available atBalder, under commissioning at CoSAXS and being developed for MicroMAX.
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| 5. |
- Fornell, Anna, et al.
(författare)
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AdaptoCell – Microfluidic Platforms at MAX IV Laboratory
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the AdaptoCell project, we are developing microfluidic platforms for X-ray studies of liquid samples. Microfluidics is a suitable technology for samples that are prone to radiation damage, such as proteins. By having the sample underflow, the sample is continuously refreshed, and the risk of radiation damage is reduced. The technology is also suitable for investigating dynamic events such as in situ mixing. The microfluidic platforms are being integrated at three beamlines at MAX IV Laboratory: Balder (X-ray absorption/emission spectroscopy), CoSAXS (small angle x-ray scattering) and MicroMAX (serial synchrotron crystallography). Currently, the platforms are available for users at Balder and CoSAXS, which is under development at MicroMAX. In addition, we also provide a microfluidic offline test station where users can test their samples and optimise their devices before the beam time. The main components of the microfluidic setup are the pressure-driven flow controller and the microfluidic chip. We mainly use commercially available polymer microfluidic chips made of COC (cyclic olefin copolymer). COC is used as a chip material as it has high X-ray transmission and high resistance to radiation damage. There are several different chip designs available such as straight channel chips, droplet generator chips and mixing chips. We believe the AdaptoCell platforms will be useful and versatile sample environments for academic and industrial users at MAX IV Laboratory who want to perform experiments with liquid samples under flow.
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| 6. |
- Gajdek, Dorotea, et al.
(författare)
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Structural Changes in Monolayer Cobalt Oxides under Ambient Pressure CO and O 2 Studied by In Situ Grazing-Incidence X-ray Absorption Fine Structure Spectroscopy
- 2022
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:7, s. 3411-3418
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Tidskriftsartikel (refereegranskat)abstract
- We have used grazing incidence X-ray absorption fine structure spectroscopy at the cobalt K-edge to characterize monolayer CoO films on Pt(111) under ambient pressure exposure to CO and O2, with the aim of identifying the Co phases present and their transformations under oxidizing and reducing conditions. X-ray absorption near edge structure (XANES) spectra show clear changes in the chemical state of Co, with the 2+ state predominant under CO exposure and the 3+ state predominant under O2-rich conditions. Extended X-ray absorption fine structure spectroscopy (EXAFS) analysis shows that the CoO bilayer characterized in ultrahigh vacuum is not formed under the conditions used in this study. Instead, the spectra acquired at low temperatures suggest formation of cobalt hydroxide and oxyhydroxide. At higher temperatures, the spectra indicate dewetting of the film and suggest formation of bulklike Co3O4 under oxidizing conditions. The experiments demonstrate the power of hard X-ray spectroscopy to probe the structures of well-defined oxide monolayers on metal single crystals under realistic catalytic conditions.
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| 7. |
- Knaapila, Matti, et al.
(författare)
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Evidence for structural transition in hairy-rod poly[9,9-bis(2-ethylhexyl)fluorene] under high pressure conditions
- 2010
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 82:5
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Tidskriftsartikel (refereegranskat)abstract
- We report on an x-ray scattering experiment of bulk poly[9,9-bis(2-ethylhexyl)fluorene] under quasihydrostatic pressure from 1 to 11 GPa at room temperature. The scattering pattern of high molecular weight (HMW) polyfluorene (>10 kg/mol) 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 direction). 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 (<10 kg/mol), which is glassy nematic in ambient pressure, is reminiscent with that of HMW polymer above 2–4 GPa.
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| 8. |
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| 9. |
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| 10. |
- Knaapila, Matti, et al.
(författare)
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Measuring Structural Inhomogeneity of Conjugated Polymer at High Pressures up to 30 GPa
- 2013
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 46:20, s. 8284-8288
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Tidskriftsartikel (refereegranskat)abstract
- We present X-ray scattering data from helical poly[9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl] by mapping the sample with 10 mu m spatial resolution at pressures up to 31 GPa. Neon is used as pressure transmitting medium. Reduction of torsion angle between adjacent repeats is observed during compression and found to be reversible upon decompression. Chain conformation does not depend on lateral position of sample in the pressure range from 1 to 7 GPa but depends significantly when pressure is increased from 7 to 31 GPa. Crystallite orientation does not depend on pressure or lateral position. The radiation damage is studied optically ex situ and proved to be insignificant.
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| 11. |
- Knaapila, M., et al.
(författare)
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Structural study of helical polyfluorene under high quasihydrostatic pressure
- 2013
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 87:2
-
Tidskriftsartikel (refereegranskat)abstract
- We report on an x-ray diffraction (XRD) study of helical poly[9,9-bis(2-ethylhexyl)fluorene] (PF2/6) under high quasihydrostatic pressure and show an effect of pressure on the torsion angle (dihedral angle) between adjunct repeat units and on the hexagonal unit cell. A model for helical backbone conformation is constructed. The theoretical position for the most prominent 00l x-ray reflection is calculated as a function of torsion angle. The XRD of high molecular weight PF2/6 (M-n = 30 kg/mol) is measured through a diamond anvil cell upon pressure increase from 1 to 10 GPa. The theoretically considered 00l reflection is experimentally identified, and its shift with the increasing pressure is found to be consistent with the decreasing torsion angle between 2 and 6 GPa. This indicates partial backbone planarization towards a more open helical structure. The h00 peak is identified, and its shift together with the broadening of 00l implies impairment of the ambient hexagonal order, which begins at or below 2 GPa. Previously collected high-pressure photoluminescence data are reanalyzed and are found to be qualitatively consistent with the XRD data. This paper provides an example of how the helical pi-conjugated backbone structure can be controlled by applying high quasihydrostatic pressure without modifications in its chemical structure. Moreover, it paves the way for wider use of high-pressure x-ray scattering in the research of pi-conjugated polymers. DOI: 10.1103/PhysRevE.87.022602
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| 12. |
- Logan, Derek, et al.
(författare)
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Status of the crystallography beamlines at the MAX IV Laboratory
- 2015
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Ingår i: The European Physical Journal Plus. - : Springer Science and Business Media LLC. - 2190-5444. ; 130:3
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Forskningsöversikt (refereegranskat)abstract
- The MAX IV Laboratory in Lund is currently operating two storage rings, the 1.5 GeV MAX II and the 700MeV MAX III, as well as constructing the new facility MAX IV, which will house a 1.5 GeV and a 3 GeV ring. At the MAX II synchrotron there are three hard X-ray beamlines at which crystallography can be performed: I711, I811 and I911. Beamline I711 is mainly used for powder diffraction. I811 is an EXAFS station at which surface XRD can also be carried out. I911 is a beamline with five experimental stations on a single superconducting wiggler source, of which two are currently used for macromolecular crystallography, namely the monochromatic station I911-2 and the tuneable station I911-3, which is equipped with a state-of-the-art goniometer and robotic sample changer. We will give an overview of the capabilities of these beamlines, focusing particularly on the macromolecular crystallography beamline I911 and some recent scientific highlights produced there. We will also give a brief overview of new beamlines for crystallography that are under construction or planned for the MAX IV facility.
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| 13. |
- Micheal Raj, Pushparani, et al.
(författare)
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Fabrication and characterisation of a silicon-borosilicate glass microfluidic device for synchrotron-based hard X-ray spectroscopy studies
- 2021
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 11:47, s. 29859-29869
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Tidskriftsartikel (refereegranskat)abstract
- Some of the most fundamental chemical building blocks of life on Earth are the metal elements. X-ray absorption spectroscopy (XAS) is an element-specific technique that can analyse the local atomic and electronic structure of, for example, the active sites in catalysts and energy materials and allow the metal sites in biological samples to be identified and understood. A microfluidic device capable of withstanding the intense hard X-ray beams of a 4th generation synchrotron and harsh chemical sample conditions is presented in this work. The device is evaluated at the K-edges of iron and bromine and the L-3-edge of lead, in both transmission and fluorescence mode detection and in a wide range of sample concentrations, as low as 0.001 M. The device is fabricated in silicon and glass with plasma etched microchannels defined in the silicon wafer before anodic bonding of the glass wafer into a complete device. The device is supported with a well-designed printed chip holder that made the microfluidic device portable and easy to handle. The chip holder plays a pivotal role in mounting the delicate microfluidic device on the beamline stage. Testing validated that the device was sufficiently robust to contain and flow through harsh acids and toxic samples. There was also no significant radiation damage to the device observed, despite focusing with intense X-ray beams for multiple hours. The quality of X-ray spectra collected is comparable to that from standard methods; hence we present a robust microfluidic device to analyse liquid samples using synchrotron XAS.
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| 14. |
- Raj, Pushparani, et al.
(författare)
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Fabrication and characterisation of a silicon-borosilicate glass microfluidic device for synchrotron-based hard X-ray spectroscopy studies
- 2021
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Ingår i: RSC Advances. - Cambridge : RSC Publishing. - 2046-2069. ; 11:47, s. 29859-29869
-
Tidskriftsartikel (refereegranskat)abstract
- Some of the most fundamental chemical building blocks of life on Earth are the metal elements. X-ray absorption spectroscopy (XAS) is an element-specific technique that can analyse the local atomic and electronic structure of, for example, the active sites in catalysts and energy materials and allow the metal sites in biological samples to be identified and understood. A microfluidic device capable of withstanding the intense hard X-ray beams of a 4th generation synchrotron and harsh chemical sample conditions is presented in this work. The device is evaluated at the K-edges of iron and bromine and the L3-edge of lead, in both transmission and fluorescence mode detection and in a wide range of sample concentrations, as low as 0.001 M. The device is fabricated in silicon and glass with plasma etched microchannels defined in the silicon wafer before anodic bonding of the glass wafer into a complete device. The device is supported with a well-designed printed chip holder that made the microfluidic device portable and easy to handle. The chip holder plays a pivotal role in mounting the delicate microfluidic device on the beamline stage. Testing validated that the device was sufficiently robust to contain and flow through harsh acids and toxic samples. There was also no significant radiation damage to the device observed, despite focusing with intense X-ray beams for multiple hours. The quality of X-ray spectra collected is comparable to that from standard methods; hence we present a robust microfluidic device to analyse liquid samples using synchrotron XAS.
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| 15. |
- Ravnsbaek, Dorthe B., et al.
(författare)
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Thermal Polymorphism and Decomposition of Y(BH4)(3)
- 2010
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 49:8, s. 3801-3809
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Tidskriftsartikel (refereegranskat)abstract
- The structure and thermal decomposition of Y(BH4)(3) is studied by in situ synchrotron radiation powder X-ray diffraction (SR-PXD), B-11 MAS NMR spectroscopy, and thermal analysis (thermogravimetric analysis/differential scanning calorimetry). The samples were prepared via a metathesis reaction between LiBH4 and YCl3 in different molar ratios mediated by ball milling. A new high temperature polymorph of Y(BH4)(3), denoted beta-Y(BH4)(3), is discovered besides the Y(BH4)(3) polymorph previously reported, denoted alpha-Y(BH4)(3). beta-Y(BH4)(3) has a cubic crystal structure and crystallizes with the space group symmetry Pm (3) over barm and a bisected a-axis, a = 5.4547(8) angstrom, as compared to alpha-Y(BH4)(3), a = 10.7445(4) angstrom (Pa (3) over bar). beta-Y(BH4)(3) crystallizes with a regular ReO3-type structure, hence the Y3+ cations form cubes with BH4 anions located on the edges. This arrangement is a regular variant of (he distorted Y3+ cube observed in alpha-Y(BH4)(3), which is similar to the high pressure phase of ReO3. The new phase, beta-Y(BH4)(3) is formed in small amounts during ball milling; however, larger amounts are formed under moderate hydrogen pressure via a phase transition from alpha- to beta-Y(BH4)(3), at similar to 180 degrees C. Upon further heating, beta-Y(BH4)(3) decomposes at similar to 190 degrees C to YH3, which transforms to YH2 at 270 degrees C. An unidentified compound is observed in the temperature range 215-280 degrees C, which may be a new Y B H containing decomposition product. The final decomposition product is YB4. These results show that boron remains in the solid phase when Y(BH4)(3) decomposes in a hydrogen atmosphere and that Y(BH4)(3) may store hydrogen reversibly.
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| 16. |
- Saldan, Ivan, et al.
(författare)
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Hydrogen Sorption in the LiH-LiF-MgB2 System
- 2013
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:33, s. 17360-17366
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Tidskriftsartikel (refereegranskat)abstract
- A composite material in the LiH-LiF-MgB2 system has been synthesized by high-energy ball milling. Some peaks in addition to that of the binary 2LiH-MgB2 and 2LiF-MgB2 systems are observed for the composite material by high-pressure differential scanning calorimetry (HP-DSC), indicating the formation of intermediate phases. In situ synchrotron radiation powder X-ray diffraction (SR-PXD) performed at 60 bar of H-2 and 390 degrees C shows a superposition of both reaction pathways that are typical for 2LiH-MgB2 and 2LiF-MgB2. After hydrogen absorption of the LiH-LiF-MgB2 composite the vibrational modes of LiBH4 were observed by attenuated total reflection infrared (ATR-IR) spectroscopy. The F-19 MAS NMR spectrum of the LiF-LiBH4 sample after heat treatment in hydrogen is strongly dominated by the centerband and spinning sidebands from LiF; in addition, a low-intensity resonance, very similar to that of [BF4](-) ion, is identified.
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| 17. |
- Santoru, A, et al.
(författare)
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A new potassium-based intermediate and its role in the desorption properties of the K-Mg-N-H system.
- 2016
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Ingår i: Physical chemistry chemical physics : PCCP. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 18:5, s. 3910-3920
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Tidskriftsartikel (refereegranskat)abstract
- New insights into the reaction pathways of different potassium/magnesium amide-hydride based systems are discussed. In situ SR-PXD experiments were for the first time performed in order to reveal the evolution of the phases connected with the hydrogen releasing processes. Evidence of a new K-N-H intermediate is shown and discussed with particular focus on structural modification. Based on these results, a new reaction mechanism of amide-hydride anionic exchange is proposed.
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| 18. |
- Suarez Alcantara, Karina, et al.
(författare)
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SEM and XAS characterization at beginning of life of Pd-based cathode electrocatalysts in PEM fuel cells
- 2014
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 39:10, s. 5358-5370
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Tidskriftsartikel (refereegranskat)abstract
- The fuel cell performance of membrane electrode assemblies with a Pt anode and Pd, PdCu or Pd5Cu4Pt cathodes has been tested during 116 h (beginning of life). The incorporation of Cu to Pd increases the fuel cell performance. Incorporation of Pt leads to further improvement. SEM micrographs of the as-prepared and the fuel cell-tested assemblies show the effects of the 116 h of continuous operation. Nafion membranes were characterized by small angle X-ray scattering. The results show a reduction of the size of the lamellar domains in the perfluorinated matrix after fuel cell testing, but no correlation with the cathode electrocatalyst material. The cathode electrocatalysts were characterized by ex-situ synchrotron radiation X-ray diffraction and X-ray absorption spectroscopy at the Pd L-3, Cu K and Pt L-3 edges. Re-organization of Pd5Cu4Pt electrocatalyst after fuel cell testing was observed. The Cu in the electrocatalyst can be described as a nano-mixture of metallic Cu, alloyed Cu and CuO. The CuO acts as a promoter of the ORR. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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| 19. |
- Suarez Alcantara, Karina, et al.
(författare)
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Synchrotron-based structural and spectroscopic studies of ball milled RuSeMo and RuSnMo particles as oxygen reduction electrocatalyst for PEM fuel cells
- 2014
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 1879-3487 .- 0360-3199. ; 39:29, s. 16715-16721
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Tidskriftsartikel (refereegranskat)abstract
- Particles of RuSeMo and RuSnMo have been produced by ball milling; they present catalytic activity towards the oxygen reduction reaction (ORR) in acid media. A Tafel slope close to 120 mV/dec was found for both materials. Their morphology was first characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM images reveal particles in the sub-micrometer range. The structure of the materials was further probed with synchrotron radiation powder X-ray diffraction (SR-PXD) and X-ray absorption spectroscopy (XAS). SR-PXD reveals the existence of metallic Ru as the main phase and the formation of phases such as RuSe2 in RuSeMo and Ru3Sn7 in RuSnMo. Mo was found to form solid solution into the RuSe2 phase in ball milled RuSeMo. Finally, The Ru L-3-edge and Mo L-3-edge XAS fingerprints were correlated with the catalytic activity towards ORR. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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| 20. |
- Vallenhag, Linda, et al.
(författare)
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A combined small- and wide-angle x-ray scattering detector for measurements on reactive systems
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 82:8
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Tidskriftsartikel (refereegranskat)abstract
- A detector with high dynamic range designed for combined small-and wide-angle x-ray scattering experiments has been developed. It allows measurements on single events and reactive systems, such as particle formation in flames and evaporation of levitating drops. The detector consists of 26 channels covering a region from 0.5 degrees to 60 degrees and it provides continuous monitoring of the sampled signal without readout dead time. The time resolution for fast single events is about 40 mu s and for substances undergoing slower dynamics, the time resolution is set to 0.1 or 1 s with hours of continuous sampling. The detector has been used to measure soot particle formation in a flame, burning magnesium and evaporation of a toluene drop in a levitator. The results show that the detector can be used for many different applications with good outcomes and large potential. (C) 2011 American Institute of Physics. [doi:10.1063/1.3613958]
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| 21. |
- Zhu, Nan, et al.
(författare)
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Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production.
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 10(9) s(-1). Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications.
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| 22. |
- Zhu, Qiushi, et al.
(författare)
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Correlating structure and electronic band-edge properties in organolead halide perovskites nanoparticles
- 2016
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:22, s. 14933-14940
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Tidskriftsartikel (refereegranskat)abstract
- After having emerged as primary contenders in the race for highly efficient optoelectronics materials, organolead halide perovskites (OHLP) are now being investigated in the nanoscale regime as promising building blocks with unique properties. For example, unlike their bulk counterpart, quantum dots of OHLP are brightly luminescent, owing to large exciton binding energies that cannot be rationalized solely on the basis of quantum confinement. Here, we establish the direct correlation between the structure and the electronic band-edge properties of CH3NH3PbBr3 nanoparticles. Complementary structural and spectroscopic measurements probing long-range and local order reveal that lattice strain influences the nature of the valence band and modifies the subtle stereochemical activity of the Pb2+ lone-pair. More generally, this work demonstrates that the stereochemical activity of the lone-pair at the metal site is a specific physicochemical parameter coupled to composition, size and strain, which can be employed to engineer novel functionalities in OHLP nanomaterials.
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