| 1. |
- Dou, S.X., et al.
(författare)
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Microstructure and flux pinning in superconducting Bi-Pb-Sr-Ca-Cu-O wires
- 1990
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Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 172:1-2, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- The critical current density (Jc) of Ag-clad Bi-Pb-Sr-Ca-Cu-O wire has been measured to be 1.2×104 A/cm2 at 77 K in zero field. The high Jc is attributed to a combination of elimination of the poisoning effect of Ag on superconductivity, grain alignment, and enhancement of flux pinning. Jc-H dependence was significantly improved in the Ag-clad tape, which has a Jc of 1.0×103 A /cm2 at 77 K and 4000 Oe, while the Jc of the sintered pellet drops two orders of magnitude at only 100 Oe. A pronounced anisotropy in Jc under high magnetic field is attributed to the grain alignment. Planar defects, such as heavy stacking faults parallel to the a-b plane in the rolled tape, are considered to be effective pinning centres.
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| 2. |
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| 3. |
- Pei, Benyan, et al.
(författare)
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Thermodynamics and kinetics of passive oxidation of Si3N4-bonded sic ceramics
- 1994
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Ingår i: Ceramic Transactions. - 1042-1122. ; 44, s. 253-263
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation reactions of Si3N4-bonded SiC ceramics are more complicated than a single component like SiC or Si3N4. The thermodynamics and kinetics of air oxidation of such ceramics in the temperature range of 900-1300 C are studied. The active to passive transition of oxidation was analysed by thermodynamic calculations using the JANAF table. The weight gain was measured using a TGA technique to study the kinetics. It is shown that all components contribute to the formation of a silica film. The kinetic results indicate that the oxidation reactions of Si3N4-bonded SiC ceramics are controlled by both an interface reaction and diffusion through the product layer. The activation energy obtained for the specimen studied is found to be comparable with that for SiC oxidation as reported in the literature
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| 4. |
- Wang, X-H, et al.
(författare)
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Electrochemical study of surface oxidation and collectorless flotation of arsenopyrite
- 1992
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Ingår i: Journal of Applied Electrochemistry. - 0021-891X .- 1572-8838. ; 22:11, s. 1095-1103
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Tidskriftsartikel (refereegranskat)abstract
- The surface oxidation of arsenopyrite in alkaline solutions has been studied by cyclic voltammetry. The initial oxidation of arsenopyrite surface produces ferric hydroxide and a realgar-like compound according to the following rection:[Figure not available: see fulltext.] At higher potentials, the oxidation of arsenopyrite results in elemental sulphur and arsenate according to the following overall reaction: {Mathematical expression} Ferric hydroxide is precipitated and arsenate stays on the surface. Both elemental sulphur and realgar (AsS) are retained on the arsenopyrite substrate. Oxidation of arsenopyrite surfaces is not affected by potential cycling or by the presence of arsenic or sulphide species. The oxidation of hydroxyl ions takes place simultaneously with the arsenopyrite oxidation. Flotation tests demonstrated that freshly ground arsenopyrite is non-floatable in the absence of xanthate as collector. Good flotation was obtained for both freshly ground and aged arsenopyrite in the presence of EDTA. The flotation results support the reactions for arsenopyrite oxidation drawn from the electrochemical studies
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