| 1. |
- Castellote, M, et al.
(författare)
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In situ accelerated leaching of cement paste by application of electrical fields monitored by synchrotron X-ray diffraction
- 2004
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Ingår i: Applied Physics A: Materials Science & Processing. - : Springer Science and Business Media LLC. - 1432-0630. ; 79:3, s. 661-669
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Tidskriftsartikel (refereegranskat)abstract
- An external dc voltage was applied to a cured cement paste to simulate its natural degradation as a function of time. The electrical treatment was monitored in situ by simultaneous acquisition of diffraction patterns every 10 min. The analysis of the diffraction patterns has confirmed that the microstructure of the whole paste changes during the treatment, with precipitation and dissolution of several phases. This work contributes to the understanding of the fundamentals of the microstructure alterations that take place upon application of an electrical field, allowing the establishment of a first approach to the understanding of the mechanism of these changes.
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| 2. |
- Celestian, A J, et al.
(författare)
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(K4Li4)Al8Ge8O32 8H(2)O, an Li+-exchanged potassium alumino-germanate with the zeolite gismondine (GIS) topology
- 2003
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Ingår i: Acta Crystallographica. Section C: Crystal Structure Communications. - 0108-2701. ; 59:8, s. 74-76
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Tidskriftsartikel (refereegranskat)abstract
- The title compound, lithium potassium dialuminium diger-manium octaoxide dihydrate, (K,Li)-(Al,Ge)-GIS (GIS is gismondine), is the result of a 50% Li+ exchange into the K-(Al,Ge)- GIS structure. The (K,Li)-(Al,Ge)-GIS structure was determined from a 4 x 4 x 2 m m octahedral single crystal at the ESRF synchrotron X-ray source. The ion exchange results in a symmetry transformation from I2/a for K-(Al,Ge)-GIS to C2/c for (K,Li)-(Al,Ge)-GIS. The structural change is due to disordering of K+ ions with Li+ ions along the [001] channel and ordering of water molecules in the [101] channels. The distance between sites partially occupied by K+ ions increases from 2.19 (3) Angstrom in K-(Al,Ge)-GIS to 2.94 (3) Angstrom in (K,Li)-(Al, Ge)-GIS. The Li+ ions occupy positions along the twofold axis at the intersection of the eight-membered-ring channels in a twofold coordination with water molecules. For the four closest framework O2- anions, the Li ... O distances are 3.87 (4) Angstrom.
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| 3. |
- Contreras, L, et al.
(författare)
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Time-resolved XRD study of TiC-TiB2 composites obtained by SHS
- 2004
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Ingår i: Acta Materialia. - : Elsevier BV. - 1873-2453 .- 1359-6454. ; 52:16, s. 4783-4790
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Tidskriftsartikel (refereegranskat)abstract
- Composites of TiC and TiB2 were prepared by self-propagating high-temperature synthesis (SHS). Two routes were attempted; from the elements and from a mixture of anatase, boron oxide, graphite and magnesium. The reactions were monitored in situ by synchrotron X-ray diffraction ( lambda = 0. 26102 Angstrom). The powder mixtures were compacted as cylindrical pellets and upon ignition diffraction patterns were collected every 65 ms with a CCD camera. TiC was the first phase to form, followed by TiB2. The reactions take place in time scales of 0.1 s. The temperature profile for the first route was established from the peak position and the known thermal expansion coefficients. The microstructure of the final products was different: particles of 10 mum for the first and submicron for the second. The viability of the second route to produce ceramic powders in a cheaper way was confirmed. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 4. |
- Duggan, P, et al.
(författare)
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Gamma-ray bursts and X-ray melting of material to form chondrules and planets
- 2003
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 409:2, s. 9-12
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Tidskriftsartikel (refereegranskat)abstract
- Chondrules are millimeter sized objects of spherical to irregular shape that constitute the major component of chondritic meteorites that originate in the region between Mars and Jupiter and which fall to Earth. They appear to have solidified rapidly from molten or partially molten drops. The heat source that melted the chondrules remains uncertain. The intense radiation from a gamma-ray burst (GRB) is capable of melting material at distances up to 300 light years. These conditions were created in the laboratory for the first time when millimeter sized pellets were placed in a vacuum chamber in the white synchrotron beam at the European Synchrotron Radiation Facility (ESRF). The pellets were rapidly heated in the X-ray and gamma-ray furnace to above 1400 degreesC melted and cooled. This process heats from the inside unlike normal furnaces. The melted spherical samples were examined with a range of techniques and found to have microstructural properties similar to the chondrules that come from meteorites. This experiment demonstrates that GRBs can melt precursor material to form chondrules that may subsequently influence the formation of planets. This work extends the field of laboratory astrophysics to include high power synchrotron sources.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Kvick, Åke
(författare)
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Materials science at the European Synchrotron Radiation Facility.
- 2003
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 199, s. 531-535
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Tidskriftsartikel (refereegranskat)abstract
- The Materials Science Beamline ID11 at the European Synchrotron Radiation Facility in Grenoble, France is dedicated to research in materials science notably employing diffraction and scattering techniques. Either an in-vacuum undulator with a minimum gap of 5 mm or a 10 kW wiggler giving high-flux monochromatic X-rays generates the synchrotron radiation in the energy range 5–100 keV. The dominant research is in the area of time-resolved diffraction, powder diffraction, stress/strain studies of bulk material, 3D mapping of grains and grain interfaces with a measuring gauge down ~5×5×50 m, and microcrystal diffraction. A variety of CCD detectors are used to give time-resolution down to the millisecond time regime.
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| 9. |
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| 10. |
- Spiers, H, et al.
(författare)
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Self propagating high temperature synthesis of magnesium zinc ferrites (MgxZn1-xFe2O3): thermal imaging and time resolved X-ray diffraction experiments
- 2004
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501. ; 14:7, s. 1104-1111
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Tidskriftsartikel (refereegranskat)abstract
- Spinel ferrites of the form MgxZn1-xFe2O4 ( x = 0. 0.25, 0.50, 0.75, 1.00) were prepared by self-propagating high-temperature synthesis (SHS) from reactions of iron(III), zinc and magnesium oxides, iron powder and sodium perchlorate. The driving force for the reactions is the oxidation of iron powder. Reactions were carried out in the presence of an external magnetic field of 0.2 or 1.1 T. Reaction velocity and temperatures were obtained by thermal imaging camera. The transformation of reactants to products was studied by time resolved X-ray diffraction using Rietveld refinement for determination of phase percentages. Reactions typically reached temperatures in excess of 1150 degreesC with a timescale of complete conversion of reactant to products of 20 s. All materials were characterised by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDXA), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Mossbauer spectroscopy and vibrating sample magnetometry (VSM).
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