PV
P. Vermeulen
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3 records found
1
Journal article
(2007)
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D. M. Borsa, R. Gremaud, A. Baldi, H. Schreuders, J. H. Rector, B. Kooi, P. Vermeulen, P. H.L. Notten, B. Dam, R. Griessen
The structural, optical, and electrical transformations induced by hydrogen absorption and/or desorption in Mg-Ti thin films prepared by co-sputtering of Mg and Ti are investigated. Highly reflective in the metallic state, the films become highly absorbing upon H absorption. The reflector-to-absorber transition is fast, robust, and reversible over many cycles. Such a highly absorbing state hints at the coexistence of a metallic and a semiconducting phase. It is, however, not simply a composite material consisting of independent Mg H2 and Ti H2 grains. By continuously monitoring the structure during H uptake, we obtain data that are compatible with a coherent structure. The average structure resembles rutile Mg H2 at high Mg content and is fluorite otherwise. Of crucial importance in preserving the reversibility and the coherence of the system upon hydrogen cycling is the accidental equality of the molar volume of Mg and Ti H2. The present results point toward a rich and unexpected chemistry of Mg-Ti-H compounds.
...
The structural, optical, and electrical transformations induced by hydrogen absorption and/or desorption in Mg-Ti thin films prepared by co-sputtering of Mg and Ti are investigated. Highly reflective in the metallic state, the films become highly absorbing upon H absorption. The reflector-to-absorber transition is fast, robust, and reversible over many cycles. Such a highly absorbing state hints at the coexistence of a metallic and a semiconducting phase. It is, however, not simply a composite material consisting of independent Mg H2 and Ti H2 grains. By continuously monitoring the structure during H uptake, we obtain data that are compatible with a coherent structure. The average structure resembles rutile Mg H2 at high Mg content and is fluorite otherwise. Of crucial importance in preserving the reversibility and the coherence of the system upon hydrogen cycling is the accidental equality of the molar volume of Mg and Ti H2. The present results point toward a rich and unexpected chemistry of Mg-Ti-H compounds.
Journal article
(2006)
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D. M. Borsa, A. Baldi, M. Pasturel, H. Schreuders, B. Dam, R. Griessen, P. Vermeulen, P. H.L. Notten
Mg-Ti-H thin films are found to have very attractive optical properties: they absorb 87% of the solar radiation in the hydrogenated state and only 32% in the metallic state. Furthermore, in the absorbing state Mg-Ti-H has a low emissivity; at 400 K only 10% of blackbody radiation is emitted. The transition between both optical states is fast, robust, and reversible. The sum of these properties highlights the applicability of such materials as switchable smart coatings in solar collectors.
...
Mg-Ti-H thin films are found to have very attractive optical properties: they absorb 87% of the solar radiation in the hydrogenated state and only 32% in the metallic state. Furthermore, in the absorbing state Mg-Ti-H has a low emissivity; at 400 K only 10% of blackbody radiation is emitted. The transition between both optical states is fast, robust, and reversible. The sum of these properties highlights the applicability of such materials as switchable smart coatings in solar collectors.
Journal article
(2006)
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P. Vermeulen, R. A. H. Niessen, D. M. Borsa, B. Dam, R. Griessen, P. H. L. Notten
MgyTi 1−y alloys with 0.50 < y < 1.00 were prepared by electron beam deposition and magnetron co-sputter deposition. The effects of the deposition technique are discussed in two ways; the metallurgy of the as-deposited films and the hydrogen storage characteristics. In spite of the fact that for both preparation methods similar unit cell dimensions are found, the broader X-ray diffraction peaks of e-beam deposited alloys indicate a relatively small grain size. Electrochemical characterization of the compounds upon dehydrogenation shows that the deposition method does not significantly influence the hydrogen capacity and kinetics. Moreover, essentially the same cycle-life behavior is found for both types of alloys.
...
MgyTi 1−y alloys with 0.50 < y < 1.00 were prepared by electron beam deposition and magnetron co-sputter deposition. The effects of the deposition technique are discussed in two ways; the metallurgy of the as-deposited films and the hydrogen storage characteristics. In spite of the fact that for both preparation methods similar unit cell dimensions are found, the broader X-ray diffraction peaks of e-beam deposited alloys indicate a relatively small grain size. Electrochemical characterization of the compounds upon dehydrogenation shows that the deposition method does not significantly influence the hydrogen capacity and kinetics. Moreover, essentially the same cycle-life behavior is found for both types of alloys.