| 1. |
- Wolff, Nicole, et al.
(författare)
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Temperature dependent cubic and hexagonal close packing in micellar structures
- 2014
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 10:42, s. 8420-8426
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial structure and phase diagram of a micellar solution formed by the three block copolymer ( EO20-PO70-EO20) also known as P123 solved in deuterated water close to a solid boundary is investigated with respect to temperature. We find a hysteretic behavior of the d-spacing of the micellar crystal and a spontaneous change in the lateral correlation length going hand in hand with a structural reorganization between cubic and hexagonal. The phase transitions may be initiated by a change in the shape of the micelles from spherical to elongated together with a minimization of the polymer water interface.
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| 2. |
- Adalsteinsson, Sigurbjörn Már, et al.
(författare)
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Correlating chemical composition and optical properties of photochromic rare-earth oxyhydrides using ion beam analysis
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : ELSEVIER. - 0168-583X .- 1872-9584. ; 485, s. 36-40
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Tidskriftsartikel (refereegranskat)abstract
- We relate the photochromic response of rare-earth oxyhydride thin films (YHO, NdHO, GdHO and DyHO) synthesized by reactive magnetron sputtering to chemical composition. Depth profiles of the sample composition are extracted by a multi-method ion beam analysis approach. The total areal density of the thin films is deduced from Rutherford Backscattering Spectrometry while coincidence Time-of-Flight/Energy Elastic Recoil Detection Analysis provides depth-profiles of the film constituents. High-resolution depth profiles of the concentration of light species, i.e. hydrogen and oxygen, are additionally extracted from Nuclear Reaction Analysis and Elastic Backscattering Spectrometry, respectively. The photochromic response of the films is measured by optical transmission spectroscopy before and after illumination. We report photochromic properties for YHO, NdHO, GdHO and DyHO for chemical compositions described by the formula REH2-delta O delta in the range of 0.45 < 6 < 1.5.
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| 3. |
- Adlmann, Franz A., et al.
(författare)
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Towards neutron scattering experiments with sub-millisecond time resolution
- 2015
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Ingår i: Journal of applied crystallography. - 0021-8898 .- 1600-5767. ; 48, s. 220-226
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Tidskriftsartikel (refereegranskat)abstract
- Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. It is demonstrated that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode at the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. The opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.
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| 4. |
- Adlmann, Franz A., et al.
(författare)
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Överlåtaren : a fast way to transfer and orthogonalize two-dimensional off-specular reflectivity data
- 2016
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Ingår i: Journal of applied crystallography. - 0021-8898 .- 1600-5767. ; 49, s. 2091-2099
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Tidskriftsartikel (refereegranskat)abstract
- Reflectivity measurements offer unique opportunities for the study of surfaces and interfaces, and specular reflectometry has become a standard tool in materials science to resolve structures normal to the surface of a thin film. Off-specular scattering, which probes lateral structures, is more difficult to analyse, because the Fourier space being probed is highly anisotropic and the scattering pattern is truncated by the interface. As a result, scattering patterns collected with (especially time-of-flight) neutron reflectometers are difficult to transform into reciprocal space for comparison with model calculations. A program package is presented for a generic two-dimensional transformation of reflectometry data into q space and back. The data are represented on an orthogonal grid, allowing cuts along directions relevant for theoretical modelling. This treatment includes background subtraction as well as a full characterization of the resolution function. The method is optimized for computational performance using repeatable operations and standardized instrument settings.
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| 5. |
- Adlmann, Franz, et al.
(författare)
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Depth resolved grazing incidence neutron scattering experiments from semi-infinite interfaces : a statistical analysis of the scattering contributions
- 2018
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 30
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Tidskriftsartikel (refereegranskat)abstract
- Grazing incidence neutron scattering experiments offer surface sensitivity by reflecting from an interface at momentum transfers close to total external reflection. Under these conditions the penetration depth is strongly non-linear and may change by many orders of magnitude. This fact imposes severe challenges for depth resolved experiments, since the brilliance of neutron beams is relatively low in comparison to e.g. synchrotron radiation. In this article we use probability density functions to calculate the contribution of scattering at different distances from an interface to the intensities registered on the detector. Our method has the particular advantage that the depth sensitivity is directly extracted from the scattering pattern itself. Hence for perfectly known samples exact resolution functions can be calculated and visa versa. We show that any tails in the resolution function, e.g. Gaussian shaped, hinders depth resolved experiments. More importantly we provide means for a descriptive statistical analysis of detector images with respect to the scattering contributions and show that even for perfect resolution near surface scattering is hardly accessible.
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| 6. |
- Adlmann, Franz, et al.
(författare)
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Normalization of stroboscopic neutron scattering experiments
- 2018
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 434, s. 61-65
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Tidskriftsartikel (refereegranskat)abstract
- Neutron scattering studies of kinetic processes are often flux limited. For processes which can be repeated many times, this can be mitigated by stroboscopic reintegration. The recorded scattering events are assigned to different time slices of the process and corresponding slices from all repetitions are summed up. The normalization of such data with respect to the incident beam spectrum can be challenging since the incident neutron flux may not necessarily be evenly distributed over all time slices. In this paper, we discuss how this can result in misleading information and we expand on a technique to amend these issues.
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| 7. |
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| 8. |
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| 9. |
- Baba, Elbruz Murat, et al.
(författare)
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Preferential Orientation of Photochromic Gadolinium Oxyhydride Films
- 2020
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Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 25:14
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Tidskriftsartikel (refereegranskat)abstract
- We report preferential orientation control in photochromic gadolinium oxyhydride (GdHO) thin films deposited by a two-step process. Gadolinium hydride (GdH2-x) films were grown by reactive magnetron sputtering, followed by oxidation in air. The preferential orientation, grain size, anion concentrations and photochromic response of the films were strongly dependent on the deposition pressure. The GdHO films showed a preferential orientation along the [100] direction and exhibited photochromism when synthesized at deposition pressures of up to 5.8 Pa. The photochromic contrast was larger than 20% when the films were deposited below 2.8 Pa with a 0.22 H-2/Ar flow ratio. We argue that the relation of preferential orientation and the post deposition oxidation since oxygen concentration is known to be a key parameter for photochromism in rare-earth oxyhydride thin films. The experimental observations described above were explained by the decrease of the grain size as a result of the increase of the deposition pressure of the sputtering gas, followed by a higher oxygen incorporation.
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| 10. |
- Bernal, Ximena E., et al.
(författare)
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Empowering Latina scientists
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 363:6429, s. 825-826
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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