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- Bläckberg, Lisa, et al.
(författare)
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Investigations of surface coatings to reduce memory effect in plastic scintillator detectors used for radioxenon detection
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 656:1, s. 84-91
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Tidskriftsartikel (refereegranskat)abstract
- In this work Al(2)O(3) and SiO(2) coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta-gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900 nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425 nm Al(2)O(3) coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question.
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- Elihn, K, et al.
(författare)
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Nanoparticle formation by laser-assisted photolysis of ferrocene.
- 1999
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Ingår i: NANOSTRUCTURED MATERIALS. - 0965-9773. ; 12:1-4, s. 79-82
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Tidskriftsartikel (refereegranskat)abstract
- Laser-assisted formation of iron-containing nanoparticles has been performed by photolytic dissociation of ferrocene vapour by a pulsed ArF excimer laser at 193 nm. The process was carried out at atmospheric pressure, either in an inert atmosphere of argo
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- Heszler, P, et al.
(författare)
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Formation and emission spectroscopy of laser-generated nanoparticles
- 2002
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Ingår i: Smart materials and structures. - : IOP Publishing. - 0964-1726 .- 1361-665X. ; 11, s. 631-639
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Tidskriftsartikel (refereegranskat)abstract
- Fe nanoparticles, with both fcc and bcc structures and with a C shell that protects against oxidation, were generated by the laser-assisted photolytic chemical vapor decomposition of ferrocene (FeCp2). Amorphous W and WN0,3 nanoparticles were formed by laser ablation (LA) of solid W in Ar and in N2 ambient, respectively. Laser-assisted chemical vapor deposition of W yielded crystalline W nanoparticles (β phase) from a WF6/H2/Ar gas mixture. ArF excimer laser was used as the radiation source in all the experiments. Measurements and analysis of the emitted blackbody-like radiation from the laser heated particles were performed and dominant cooling processes such as evaporation and heat transfer by the ambient gases were identified. The particles could be heated up to the boiling and melting point of Fe and W, respectively. Lognormal particle size distributions were found for Fe/C and W nanoparticles generated by vapor decomposition or deposition processes respectively, and then modeled at low particle concentration (with no coagulation). The thickness of the C shell was practically independent of the laser fluence, while the size of the Fe core could be varied for the Fe/C particles. The LA yielded no lognormal-type distribution for the amorphous WN0,3 particles.
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- Heszler, Peter, et al.
(författare)
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Optical characterisation of the photolytic decomposition of ferrocene into nanoparticles
- 2000
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Ingår i: Applied Physics A. ; 70, s. 613-616
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Tidskriftsartikel (refereegranskat)abstract
- Abstract. Optical emission from the photolytic dissociation of ferrocene Fe(C5H5)2, often abbreviated as FeCp2, in argon atmosphere was studied. The dissociation was performed by using an ArF excimer laser, operating at a wavelength of 193 nm. Two pressure regions were examined. At low (0.1 mbar) pressure, several emission lines of Fe could be identified, however no C, C2, or CH emission lines/bands were found. At a higher (20 mbar) pressure of the FeCp2/Ar gas mixture, a broadband emission identified as blackbody radiation was observed. This blackbody radiation originates from nanoparticles with a mean size of 30 nm, which consist of both metallic iron and amorphous carbon. The initial colour temperature of the particles was 2600 K.
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- Karlsson, Martin, 1982-, et al.
(författare)
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Dye-sensitized solar cells employing a SnO2-TiO2 core-shell structure made by atomic layer deposition
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Ingår i: Advanced Energy Materials.
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the synthesis and characterization of core-shell structures, based on a SnO2 and TiO2 for use in dye-sensitized solar cells (DSC). Atomic layer deposition is employed to control and vary the thickness of the TiO2 shell. Increasing the TiO2 shell thickness to 2 nm improves the device performance of liquid electrolyte DSC from 0.7 % to 3.5 %. The increase in efficiency originates from a higher open-circuit potential and a higher short-circuit current as well as an improvement in the electron lifetime. SnO2-TiO2 core-shell DSC devices retain their photo-voltage in darkness for longer than 500 seconds showing that electrons are contained in the core material. Finally core-shell structures were used for solid-state DSC applications using the hole transporting material 2,2’,7,7’,-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9’,-spirofluorene. Similar increases in devices performance are seen for these solid-state DSC devices.
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- Karlsson, Martin, et al.
(författare)
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Dye-sensitized Solar Cells Employing a SnO2-TiO2 Core-shell Structure Made by Atomic Layer Deposition
- 2013
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Ingår i: CHIMIA. - : Swiss Chemical Society. - 0009-4293 .- 2673-2424. ; 67:3, s. 142-148
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the synthesis and characterization of core-shell structures, based on SnO2 and TiO2, for use in dye-sensitized solar cells (DSc). Atomic layer deposition is employed to control and vary the thickness of the TiO2 shell. Increasing the TiO2 shell thickness to 2 nm improved the device performance of liquid electrolyte-based DSC from 0.7% to 3.5%. The increase in efficiency originates from a higher open-circuit potential and a higher short-circuit current, as well as from an improvement in the electron. lifetime. SnO2-TiO2 core-shell DSC devices retain their photovoltage in darkness for longer than 500 seconds, demonstrating that the electrons are contained in the core material. Finally core-shell structures were used for solid-state DSC applications using the hole transporting material 2,2',7,7',-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9',-spirofluorene. Similar improvements in device performance were obtained for solid-state DSC devices.
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| 10. |
- Landström, Lars, et al.
(författare)
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Analysis of thermal radiation from laser-heated nanoparticles formed by laser-induced decomposition of ferrocene
- 2005
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 1432-0630 .- 0947-8396. ; 81, s. 827-833
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Tidskriftsartikel (refereegranskat)abstract
- Thermal radiation, originating from laser-heated gas-phase nanoparticles, was detected in the 400–700 nm wavelength range by means of optical emission spectroscopy. The particles were formed upon laser-induced photolytic decomposition of ferrocene (Fe(C5H5)2) and consisted of an iron core surrounded by a carbon shell. The laser-induced excitation was performed as the particles were still within the reactor zone, and the temperature of the particles could be determined from thermal emission. Both the temperature of the nanoparticles and the relative intensity changes of the emission were monitored as a function of time (with respect to the laser pulse), laser fluence and Ar ambient pressure. At high laser fluences, the particles reached high temperatures, and evidence was found for boiling of iron. Modeling of possible energy-releasing mechanisms such as black-body radiation, thermionic electron emission, evaporation and heat transfer by the ambient gas was also performed. The dominant cooling mechanisms at different ranges of temperature were clarified, together with a determination of the accommodation factor for the Ar–nanoparticle collisions. The strong evaporation at elevated temperatures also led to significant iron loss from the produced particles.
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