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| 2. |
- Carlsson, Ella, et al.
(författare)
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Mass composition of the escaping plasma at Mars
- 2006
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Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 182:2, s. 320-328
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Tidskriftsartikel (refereegranskat)abstract
- Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO2+/O+ and O-2(+)/O+. The following ratios averaged over all events and energies were identified: CO2+/O+ = 0.2 and O-2(+)/O+ = 0.9. The values measured are significantly higher, by a factor of 10 for O-2(+)/O+, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O+, followed by O-2(+) and CO2+. We estimate the loss of CO2+ to be 4.0 x 10(24) s(-1) (0.29 kg s(-1)) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.
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| 3. |
- Smith, A., et al.
(författare)
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LunarEX-a proposal to cosmic vision
- 2009
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 711-740
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Dahl, P., et al.
(författare)
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Densification and properties of zirconia prepared by three different sintering techniques
- 2007
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 33:8, s. 1603-1610
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Tidskriftsartikel (refereegranskat)abstract
- Densification of nanocrystalline yttria stabilized zirconia (YSZ) powder with 8 mol% Y2O3, prepared by a glycine/nitrate smoldering combustion method, was investigated by spark plasma sintering, hot pressing and conventional sintering. The spark plasma sintering technique was shown to be superior to the other methods giving dense materials (>= 96%) with uniform morphology at lower temperatures and shorter sintering time. The grain size of the materials was 0.21, 0.37 and 12 mu m after spark plasma sintering, hot pressing and conventional sintering, respectively. Total electrical conductivity of the materials showed no clear correlation with the grain size, but the activation energy for spark plasma sintered materials was slightly higher than for materials prepared by the two other densification methods. The hardness, measured by the Vickers indentation method, was found to be independent on grain size while fracture toughness, derived by the indentation method, was slightly decreasing with increasing grain size.
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| 7. |
- Nygren, Mats, et al.
(författare)
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Spark plasma sintering of Zr- and Hf-borides with decreasing amounts of MoSi2 as sintering aid.
- 2008
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Ingår i: Journal of European Ceramic Society. ; 28:1287-1296
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Tidskriftsartikel (refereegranskat)abstract
- ZrB2- and HfB2-based composites contg. 1, 3, and 9 vol.% MoSi2 as sintering aid were densified by spark plasma sintering at temps. ranging from 1700 to 1950, with an applied pressure of 100 MPa. As-received ZrB2 and HfB2 powders were also sintered at temps. in the range of 2100-2200. Fully dense samples were obtained between 1750 and 1850 when MoSi2 was added. As-received ZrB2 powder was sintered to 98% at 2100. The microstructural features were investigated by SEM-EDS technique. SciC was detected in all the doped compns. along with significant amts. of oxide species (Hf/ZrO2 and SiO2). Vickers hardness and fracture toughness were measured by indentation technique on polished sections. The effect of the MoSi2 content on densification, microstructure, and mech. properties is discussed.
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