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| 2. |
- Borck, Øyvind, 1971, et al.
(författare)
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Adsorption of Methanol on Aluminum Oxide: A Density Functional Study
- 2003
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Ingår i: ATB-Metallurgie. - 0365-7302. ; 43, s. 342-
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Konferensbidrag (refereegranskat)abstract
- Theoretical calculations based on density functional theory have made significant contributions to our understanding of metal oxides, their surfaces, and the binding of molecules at these surfaces. In this paper we investigate the binding of methanol at the alpha-Al2O3(0001) surface using first-principles density functional theory. We calculate the molecular adsorption energy of methanol to be E^g_ads=1.03 eV/molecule. Taking the methanol-methanol interaction into account, we obtain the adsorption energy E_ads=1.01 eV/molecule. Our calculations indicate that methanol adsorbs chemically by donating electron charge from the methanol oxygen to the surface aluminum. We find that the surface atomic structure changes upon adsorption, most notably the spacing between the outermost Al and O layers changes from 0.11 Angstrom to 0.33 Angstrom.
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| 3. |
- Alexis, Jonas, et al.
(författare)
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Heating and electromagnetic stirring in a ladle furnace – a simulationmodel
- 2000
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 40:11, s. 1098-1104
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Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional simulation model coupling heating and induction stirring in an ASEA-SKF ladle furnace was developed. Data of the heat transfer from the area to the steel bath were predicted in a separate model and included as boundary conditions in a ladle model. The are model considers the contributions of heat transferred by of each of the following mechanisms: radiation, convection, condensation and energy transported by electrons. Predictions were made to simulate the change of temperature distribution in the ladle during simultaneous heating with electrodes and stirring by induction. A first attempt was made to compare the predictions with measured temperatures from a 100 t ASEA-SKF ladle. The agreement was found to be fairly good when heat-flux data for a 25 cm are length were used as input to the ladle model. This indicates that the model can be used for more in-depth studies of the effects of heating for ladles that are inductively stirred.
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| 4. |
- Andersson, Margareta A.T., et al.
(författare)
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Slag-metal reactions during ladle treatment with focus on desulphurisation
- 2002
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 29:3, s. 224-232
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Tidskriftsartikel (refereegranskat)abstract
- Within several cooperative projects, KTH (Royal Institute of Technology), Ovako Steel AB, and MEFOS have investigated the desulphurisation of bearing steel during vacuum degassing. The work includes thermodynamic calculations of the slag-metal equilibrium, CFD modelling of slag-metal reactions, and plant trials. Results from the various studies are presented and discussed in this paper. Models for predicting slag properties (sulphide capacity, viscosity, and oxide activities) in liquid slags as functions of slag composition and temperature have been used for the calculation of data which have been employed in static and dynamic modelling of sulphur refining. The results from static modelling show that the method allows fast and easy evaluation of the theoretical desulphurisation conditions during degassing at Ovako Steel AB, as well as theoretical determination of the parameters that have the greatest influence on the equilibrium sulphur distribution. The conclusion from dynamic modelling is that the vacuum degassing operation can be described dynamically with the present knowledge of sulphide capacity, sulphur distribution, viscosity, and oxide activities of ladle slags if this knowledge is combined with fluid flow modelling to derive the overall kinetics. The presented model approaches have been found useful in understanding the sulphur refining process at Ovako Steel AB. The dynamic modelling concept is also believed to have potential for dynamic descriptions of other slag-metal reactions in steelmaking.
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| 5. |
- Azad, Abul Kalam, 1966, et al.
(författare)
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Synthesis, structural and magnetic characterisation of the double perovskite A(2)MnMoO(6) (A = Ba, Sr)
- 2004
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Ingår i: Journal of Alloys and Compounds. - 0925-8388. ; 364:1-2, s. 77-82
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Tidskriftsartikel (refereegranskat)abstract
- A study of the crystallographic structure and magnetic properties of the double perovskites Ba2MnMoO6 and Sr2MnMoO6 in polycrystalline form has been carried out by means of neutron powder diffraction (NPD) and magnetization measurements. The Rietveld analysis of room temperature data shows that the Mn2+ and Mo6+ ions are B-site ordered, i.e. the structure is a NaCl-type ordered double perovskite. Ba2MnMoO6 crystallizes in the cubic space group Full-size image (<1 K) (a=8.1680(1)) and Sr2MnMoO6 crystallizes in the space group P42/n (a=7.9575(5), c=7.9583(9)). Bond valence sum (BVS) calculation revealed that these compounds have the valency pair of {Mn2+(3d5;t32ge2g), Mo6+(4d0)}. The magnetic measurements suggest that these compounds transform to an antiferromagnetic state below 10 K.
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| 10. |
- Fredriksson, Hasse, 1939-, et al.
(författare)
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Thoughts about the Initial Solidification Process during Continuous Casting of Steel
- 2002
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 31, s. 292-297
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The initial solidification during continuous casting is very important for the surface quality of the strand. Oscillation marks are formed by the movement of the mould. One mainly distinguishes between two different types of marks, namely folding marks and overflow marks. The formation of these can be described by the heat flow and the surface tension balance. A theoretical analysis outlining the most important parameters controlling the formation of these marks is presented. A metallographic analysis of the formation was also performed. The theory and observations have been used to analyse the effect of casting speed and oscillation frequency on the formation of different types of marks. It is shown that a meniscus is formed at the top of the growing shell. The maximum height of the meniscus determines the ideal distance between the marks. The mould frequency is related to this height. A frequency that is far from ideal causes overflow marks and folding marks with macrosegregation and cracks. The distance between the marks is, in such cases, not constant. The depth of the marks is calculated from the heat flow and the surface tension balance.
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