| 1. |
- Wang, Lijun, 1979-, et al.
(författare)
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A comparison of tradition geometrical models and mass triangle model in calculation the surface tensions of ternary sulphide melts
- 2008
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Ingår i: Calphad. - : Elsevier BV. - 0364-5916 .- 1873-2984. ; 32:1, s. 49-55
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Tidskriftsartikel (refereegranskat)abstract
- Surface tension of the Ni3S2-FeS-Cu2S ternary mattes has been calculated using a mass triangle model as well as six traditional geometrical models based on the same calculation data to investigate the difference between mass triangle model and other kinds of geometrical models. From the calculated results, it might be seen that, the mass triangle model, irrespective of the method of selection of the binary data, would give the best results compared with other traditional geometrical models. The mean square root errors of the mass triangle method only range from 1.09% to 2.8%, which are almost within the experimental error of 2.5%.
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| 2. |
- Wang, Lijun, 1979-, et al.
(författare)
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A new method for evaluating some thermophysical properties for ternary system
- 2008
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Ingår i: High Temperature Materials and Processes. - 0334-6455 .- 2191-0324. ; 27:2, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- In our earlier papers, we have presented a new method, named the mass triangle model, for calculating physicochemical properties in the ternary system within a limited solubility area. This model was shown to be superior to traditional geometrical models in the computation of ternary data from the known data for the corresponding binaries. In the present paper, the authors extend this method to a ternary system where the entire compositional area inside the ternary triangle is homogeneous. The successful application of this new method to the estimation of surface tension and density has been demonstrated in the case of the system Ni(3)S(2)-FeS-Cu(2)S at 1473K with mean square root error of +/- 1.83%, +/- 4.33% respectively, compared with the experimental results.
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| 3. |
- Sterneland, Therese, et al.
(författare)
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Solubility of Co in Cr7c3-Ab initio studies and experimental verification
- 2006
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Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 54:8, s. 1491-1495
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Tidskriftsartikel (refereegranskat)abstract
- Experimental determination of the cobalt solubility in the three-phase triangle face-centered cubic + Cr7C3 + graphite have been carried out. In the present work these results are compared with atomistic calculations of the solubility of Co in Cr7C3 phase based on ab initio cohesive energies and lattice inversion method. Comparisons are also made with the literature data reported earlier [Koster W, Sperner F. Arch Eisenhuttenwesen 1955;26:555; Thompson ER, Lemkey FD, Metall Trans 1970-1:2799; Sabin PR, Watts DJ. Metall Trans 1971;2:1260; Sahm PR, Lorenz M, Hugi W, Fruhauf V. Mettal Trans 19723:1022; Tuma H, Lobl K. Kovove Mater 1971;9:221; Fritscher K. Thermochim Acta 1979;29:357].
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| 4. |
- Sterneland, Therese, et al.
(författare)
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Investigation of (Cr,Co)(7)C-3-fcc-graphite equilibrium in the temperature interval 1373 to 1473 K
- 2006
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 37A:10, s. 3023-3028
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Tidskriftsartikel (refereegranskat)abstract
- In the current study, the phase equilibria between fee, graphite and M7C3 (M = Cr,Co) have been studied at 1373 degrees K, 1423 degrees K, and 1473 degrees K. The solubility of Co in the M7C3 phase and the solubility of Cr and C in the fee phase have been determined by the high-temperature equilibration and quenching technique. Appropriate mixtures of Cr7C3 + Co or Cr7C3 + Co + C were equilibrated and subsequently quenched in liquid nitrogen. The quenched samples were characterized by X-ray diffraction and by metallographic examination. The studies were carried out on the samples to determine the homogeneity of the sample as well as the phases and their composition. From the results, the compositional regions of the three-phase triangle M7C3 + fee + graphite could be accurately determined. The results show that the Co solubility in the Cr7C3 in the experimental temperature interval is higher than previous investigations performed at higher temperatures.
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| 5. |
- Wang, Lijun, 1979-
(författare)
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Experimental and modelling studies of the thermophysical and thermochemical properties of some slag systems
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to optimize the metallurgical processes it is necessary to improve the understandings of the industrial slag properties, which include thermophysical and thermochemical properties. In the present study Mass Triangle Model was applied to predict these properties. According to the model formula, a program was developed in Visual C++ environment to calculate different properties in limited solubility ternary system. Successful applications of this model in predicting viscosity, surface tension, and density have been demonstrated in the case of a number of ternary slags in liquid state, as for example, RExOy-CaF2-SiO2 (RE refer to rare earth metal), MnO-TiO2-SiO2, CaO-Al2O3-SiO2, BaO-FeO-Fe2O3, CaO-MnO-SiO2 etc. In addition, the method has also been extended to predict electrical conductivities and sulphide capacities, which is first attempt to compute properties. Furthermore, an extension of this model has also been performed in the present study to obtain the corresponding properties in a homogeneous ternary system. Good agreement between model calculation and literature values had demonstrated that mass triangle model offers a powerful and efficient tool for estimations of various properties of molten system only based on limited experimental information.Knowledge of the thermodynamic properties of chromium oxides-containing slags is of great importance to chromium retention in stainless steel production, in view of chromium impacts on economic costs and environmental protection. Thus, the oxidation states of chromium in slags as well as sulphide capacity of CrOx-containing slag have been studied. In the studies of oxidation state of chromium in slags, gas/slag equilibrium technique was used for CaO-SiO2-CrOx system and the ratio of Cr2+/Cr3+ in multicomponent slags was measured by X-ray absorption near edge spectra (XANES). High-temperature mass spectrometry method was also used to obtain the distribution of chromium oxides in CaO-MgO(-FeO)-Al2O3-SiO2-CrOx system. It is to be noted that the present work is probably the first to employ Knudsen cell-mass spectrometry as an effective way to estimate chromium valences through vapor species. Utilizing the data obtained in present study as well as those reported in literature, a mathematical correlation was established for estimating the ratio of Cr2+/Cr3+ as a function of temperature, partial pressure of oxygen and slag basicity. The comparison between experimental valence ratio values and estimated ones presents a satisfactory agreement.The sulphide capacities of CaO-SiO2-CrOx pseudo-ternary slags were measured using the gas-slag equilibration technique in the temperature range 1823–1923 K under two different oxygen partial pressures 9.80×10-3 and 9.88×10-4 Pa. The results showed that log10Cs varied linearly with the reciprocal temperature, and the slope was higher than the corresponding value reported in the case of the binary CaO-SiO2 of corresponding composition. By using the equation developed as part of this project relating Cr2+/Cr3+ with basicity, oxygen partial pressure and temperature, it was possible to understand the effect of CrO on the sulphide capacities; viz. the sulphide capacity shows a decreasing trend as Cr2+ replaces Ca2+ in the slag. With further increase of Cr2+ content, there are indications of the occurrence of a minimum point beyond which the sulphide capacities show a slight increasing trend. The latter is attributed to the increasing extent of the polymerization reaction releasing oxygen ions for sulphide reactions in the metasilicate region. The behavior of CrO in the slag was found to be analogous to FeO.Estimation of liquidus and solidus temperature of slag was also carried out in the present study. The results indicated that it is possible to get a reasonable idea of the solidus temperature from X-ray radiography while DSC would indicate the liquidus temperature of slag
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| 6. |
- Sterneland, Therese
(författare)
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Thermodynamic Study of Co-Cr and C-Co-Cr Systems
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An experimental investigation of the binary system Co-Cr and the ternary system C-Co-Cr has been carried out in the present thesis. The experimental strategy adopted for the binary system was to measure the thermodynamic activities of Cr, the molar heat capacity as function of time, the phase transformation temperatures with corresponding enthalpies, the Curie transition temperature as well as melting temperatures with corresponding enthalpies. In the ternary system the strategy was to determine the solubility of Co in the Cr7C3 phase as well as the C and Cr contents in the Co rich (fcc) binder phase. The experimental results were compared with atomistic simulations of the solubility of Co in the Cr7C3 phase. Solid state galvanic cell measurements were conducted with both ZrO2-7.5 mol % CaO and CaF2 as the solid electrolyte. In view of possible errors in the measurements with ZrO2-7.5 mol % CaO, as a result of electronic contributions to the conduction of the solid electrolyte, new measurements were conducted with CaF2 as the solid electrolyte. The results indicated that the measured EMF values showed trends which were contrary to the thermodynamic behaviour expected from phase diagram considerations. It was concluded that further detailed experimentation was necessary in order to throw more light on the thermodynamic behaviour of the Co-Cr system. Two different series of DSC measurements were conducted, i.e. one in an atmosphere of pure hydrogen and another in pure argon. In the first investigation, conducted in an atmosphere of pure hydrogen in the temperature interval 318-1660 K, evidence was obtained for the existence of a phase transformation around 900 K in the compositional range 20.7-67.1 wt.% Cr. No indications of such a phase transformation had earlier been seen. In the second investigation, conducted in an atmosphere of pure argon in the temperature interval 298-1823 K, special attention was given to alloys in the Co rich corner of the phase diagram, i.e. 0-10 wt.% Cr. This investigation verified earlier findings of a phase transformations around 900 K in the compositional range 20.7-67.4 wt.% Cr. The magnetic transition temperatures for alloys low in Cr content were also obtained. With the use of the DTA technique the melting temperatures with corresponding enthalpy values for alloys in the compositional range 0.9-7.7 wt.% Cr were obtained. The three-phase triangle fcc+Cr7C3+graphite was investigated at 1373 K, 1423 K and 1473 K. The obtained results showed that the solubility of cobalt in the Cr7C3 phase was significantly higher than previously predicted by thermodynamic calculations.
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