| 1. |
- Pei, Benyan, et al.
(författare)
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A thermodynamic assessment of the iron - Antimony system
- 1995
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Ingår i: Calphad. - 0364-5916 .- 1873-2984. ; 19:1, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- A critical assessment of the Fe-Sb system was carried out by using a computerized technique. Both the liquid and solid solution phases were described by regular solution models. Nonstoichiometric phase, ε-FeSb, was modeled as (Fe)(Fe,Sb), and FeSb2 was treated as a stoichiometric compound. A set of parameters describing the Gibbs energies of the different phases was optimized by using the existing phase diagram information and thermodynamic properties under one atmosphere. Assessed phase diagram and thermodynamic data are presented and compared with experimental data.
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| 2. |
- Pei, Benyan
(författare)
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Assessment of arsenic activity in molten copper
- 1993
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Ingår i: Scandinavian journal of metallurgy. - 0371-0459 .- 1600-0692. ; 22:1, s. 24-29
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Tidskriftsartikel (refereegranskat)abstract
- The literature on the experimentally measured arsenic activities in molten copper alloys was reviewed. It was found that the arsenic activity coefficients at infinite dilution in molten copper, γAs0, differ by one to three orders of magnitude in the temperature range 1273 to 1423 K. Such discrepancies may be due to different arsenic thermodynamic and vapor pressure data used by different authors. Based on more accurate data for arsenic vapour species, vapour phase equilibria at various temperatures have been calculated. Tetramer As4 is the predominant species in the vapour phase saturated with solid or liquid arsenic. When arsenic vapour, saturated previously with solid arsenic, is heated to temperatures above 1273 K, As2 becomes the predominant species. Recalculation of the arsenic activities in molten copper from literature data shows that RTlnγAs0 is fairly constant and has an average value of -69 229 J/mol in the temperature range 1273 to 1423 K.
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| 3. |
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| 4. |
- Pei, Benyan, et al.
(författare)
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Thermodynamic assessment of the Cu-As system using an ionic two-sublattice model for the liquid phase
- 1994
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Ingår i: Zeitschrift für Metallkunde. - 0044-3093. ; 85:3, s. 178-184
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Tidskriftsartikel (refereegranskat)abstract
- The thermodynamic properties and phase relations in the system Cu-As were assessed. The liquid phase was described using an ionic two-sublattice model. The terminal FCC copper solution was represented by a substitutional regular solution model. The nonstoichiometric phase, γ (Cu3As), was treated by a two-sublattice model, (Cu, Va)3As, with vacancies on the Cu sublattice. The other two intermetallic compounds, β (Cu 8As) and δ (Cu12As5), were treated as stoichiometric phases. A consistent set of thermodynamic parameters was derived using activity data and phase diagram information from the literature. Various thermodynamic properties and the phase diagram were calculated from the parameters. The calculated phase equilibria and activities of arsenic and copper in the liquid phase agree very well with the literature data.
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| 5. |
- Pei, Benyan, et al.
(författare)
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Thermodynamic assessment of the Fe-As system using an ionic two-sublattice model for the liquid phase
- 1994
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Ingår i: Zeitschrift für Metallkunde. - 0044-3093. ; 85:3, s. 171-177
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Tidskriftsartikel (refereegranskat)abstract
- The phase diagram and thermodynamic data of the Fe-As system were critically assessed. Activities in the liquid phase and phase diagram information were used in the assessment. The liquid phase was represented by an ionic two-sublattice model. The terminal BCC and FCC solid solutions of arsenic in iron were described by a substitutional regular solution model. The nonstoichiometric compound, Fe3As2, was treated by a two-sublattice model, Fe(As, Va)0.75, with vacancies on the As sublattice. The other intermetallic compounds, Fe2As, FeAs, and FeAs2 were all considered as stoichiometric. Based on the assessed thermodynamic model parameters, the thermodynamic properties and the phase diagram were calculated and discussed. The calculated phase equilibria and component activities of the liquid phase agree very well with literature data.
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| 6. |
- 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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| 7. |
- Pei, Benyan, et al.
(författare)
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Thermodynamics of oxide-sulphide equilibria for chromium, vanadium and titanium
- 1991
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Ingår i: Scandinavian journal of metallurgy. - 0371-0459 .- 1600-0692. ; 20:6, s. 331-340
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium between oxides and sulphides of chromium, vanadium, and titanium was studied at 1000-1400°C by means of a H2-H2S-H2O gas mixture according to the reaction: MeOy + x H2S + (y - x) H2 = MeSx + y H2O, where Me denotes one of the three metals. Measurements were made in the range of log (H2S/H2) between about -2 and -1. Of the three oxides, chromium oxide is sulphided most easily and titanium oxide least easily. The stoichiometric coefficients x and y were derived from the (H2S/H2) and (H2O/H2) ratios and their interrelation. The results were combined with known Gibbs energy data for MeOy, H2S and H2O to give ΔGxο for the reaction: Me + (x/2) S2 = MeSx. The stability of the sulphides relative to the elements increases in the sequence chromium to titanium. Results were combined with literature data for the sulphur potentials in the solid solution range MeSx to give ΔGxο as function of x. For each of the three metals ΔGxο decreases with increasing x value to a minimum where the S2 potential reaches 1 atm. This minimum occurs at about 59 atom % S for chromium, about 60 atom % S for vanadium and about 62 atom % S for titanium
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| 8. |
- Wang, G.X., et al.
(författare)
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Oxidation mechanism of Si3N4-bonded SiC ceramics by CO, CO2 and steam
- 1998
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Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 33:5, s. 1309-1317
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a theoretical and experimental investigation into the oxidation reactions of Si3N4-bonded SiC ceramics. Such ceramics which contain a small amount of silicon offer increased oxidation and wear resistance and are widely used as lining refractories in blast furnaces. The thermodynamics of oxidation reactions were studied using the JANAF tables. The weight gain was measured using a thermogravimetric analysis technique to study the kinetics. The temperature range of oxidation measurements is from 1073 to 1573 K and the oxidation atmosphere is water vapour, pure CO and CO-CO2 gas mixtures with various CO-to-CO2 ratios. Thermodynamic simulations showed that the oxidation mechanism of Si3N4-bonded SiC ceramics is passive oxidation and all components contribute to the formation of a silica film. The activated energies of the reactions follow the sequence Si3N4 > SiC > Si. The kinetic study revealed that the oxidation of Si3N4-bonded SiC ceramics occurred in a mixed regime controlled by both interface reaction and diffusion through the silica film. Under the atmosphere conditions prevailing in the blast furnace, this ceramic is predicted to be passively oxidized with the chemical reaction rate becoming more dominant as the CO concentration increases
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