A thermodynamic study of the system CaO + Al2O3 + FexO at 1673 K

Electrochemical measurements of the solid-oxide galvanic cell: Mo/Mo + MoO₂/ZrO₂(MgO)/(CaO + Al₂O₃ + Fe_xO) + Fe(s) + Ag/Fe have been conducted at 1673 K in order to obtain the activities of Fe_xO) in CaO + Al₂O₃ + Fe_xO slags. By using the activity data for Fe_xO, the isothermal section of the phase diagram for the system CaO + Al₂O₃ + Fe_xO was derived.     

A thermodynamic study of the system FexO + AI2O3 + SiO2 at 1673 K

Electrochemical measurements of the solid-oxide galvanic cell Mo/Mo + MoO₂/ZrO₂(MgO)/Fe + (Fe_xO + A1₂O₃ + SiO₂)_slag/Ag/Fe have been made at 1673 K in order to obtain the activities of Fe_xO in Fe_xO + A1₂O₃ + SiO₂ slags. Activities of A1₂O₃ and SiO₂ were also determined by virtue of Gibbs-Duhem integration. By using the activity data, the free energies of formation of hercynite and mullite were also obtained. Leave of absence from the Steelmaking Research Section, Iron and Steel Research Laboratories, Kobe Steel Ltd.     

Chemical potentials of oxygen for mixtures of CaO (s) + Ca4P2O9 (s) + {CaO + P2O5 + FexO} melts and Ca4P2O9 (s) + Ca3P2O8 (s) + {CaO + P2O5 + FexO} melts

Electrochemical measurements involving stabilized zirconia as solid electrode and Mo + MoO₂ as reference electrode were conducted in order to determine the chemical potentials of oxygen for threephase assemblages of CaO (s) + Ca₄P₂O₉ (s) + liquid and Ca₄P₂O₉ + Ca₃P₂O₈ + liquid within the system CaO + Fe_xO + P₂O₅. The results for the former are $$\log (P_{O_2 } /atm) = 6.22 - 27,900 (T/K)$$ while for the latter, $$\log (P_{O_2 } /atm) = 6.35 - 27,600 (T/K)$$      

Thermodynamics of iron oxide in FexO‐dilute CaO + Al2O3 + SiO2 + FexO slags at 1873 K

The ferrous and ferric ion capacities, and , for the slag of CaO + Al₂O₃ + SiO₂ are determined at 1873 K by means of the distribution equilibrium of iron between Fe_xO dilute slags of the system and Pt + Fe alloys under a controlled atmosphere. Compared with the values of for CaO + Al₂O₃ binary slag at a constant ratio of Al₂O₃ to decreases with an increase in SiO₂ content. Nearly linear relationships are observed between the logarithm of the ferrous and ferric ion capacities and the optical basicity. Applying these capacities, the relationship between (%Fe^T) and PO₂ under iron saturation, as well as the iron redox equilibrium in slag in relation to the optical basicity were discussed.     

Phase equilibrium in the system ZrO2 + MgO + P2O5 at 1573 K

Phase equilibrium in the system ZrO₂ + MgO + P₂O₅ near ZrO₂—MgO edge was established at 1 573 K. Within the composition range investigated pseudoternary compounds were not detected, while two compatibility triangles for ZrO₂ + MgO + 3MgO · P₂O₅ and ZrO₂ + 3 MgO · P₂O₅ + 2ZrO₂ · P₂O₅ were determined.     

Chemical potentials of oxygen for three-phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt

By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO₂ mixture as reference electrode, the equilibrium oxygen partial pressures for three-phase assemblages of CaSiO₃(s) + Ca₃Si₂O₇(s) + {CaO + SiO₂ + Fe_xO} melt and Ca₃Si₂O₇(s) + Ca₂SiO₄(s) + {CaO + SiO₂ + Fe_xO} melt were determined as: - log {P_O2 (CS + C₃S₂ + L)/bar} = - 3.22 13000/(T/K) ± 0.05 - log {P_O2 (C₃S₂ + C₂S + L)/bar} = - 0.92 16400/ (T/K) ± 0.04. respectively, where CS, C₃S₂ and C₂S indicate CaSiO₃(s), Ca₃Si₂O₇(s). and Ca₂SiO₄(s), respectively.     

Activities of FexO in CaO + CaF2 + SiO2 + FexO quaternary slags by disposable electrochemical oxygen probes

The activities of Fe_xO in CaO + CaF₂ + SiO₂ + Fe_xO quaternary slags were measured by means of solid-oxide galvanic cell. The Fe_xO activities in the slags are influenced by CaF₂ as well as SiO₂. At constant Fe_xO mole fractions, e.g., , at low SiO₂ mole fractions i.e., , the substitution of CaF₂ for CaO has an effect of raising the Fe_xO activity. At higher SiO₂ mole fractions, e.g., , however, such an effect becomes insignificant.     

A thermodynamic study of MgO—P2O5 slags by means of solid-oxide galvanic cell at 1673 K

An electrochemical method was tested in order to find a suitable experimental technique for the determinations of the activities of P₂O₅ in molten fluxes used for external dephosphorization of hot metal. This technique consists of equilibrating phosphorus-containing copper with molten slag and measuring the equilibrium oxygen partial pressure by means of solid state galvanic cells. The activities of P²O₅ in MgO—P₂O₅ were determined with this technique.     

Phase Equilibrium of the System CaO‐P2O5‐SiO2 between 1473 K and 1673 K

Phase equilibrium was investigated in the ternary system of CaO‐P₂O₅‐SiO₂ at 1473K, 1573K and 1673K.     

Existence of a solid solution between 3CaO·V2O5 and 3CaO·P2O5

In the present work, a solid solution of 3CaO · V₂O₅ and 3CaO·P2O5 was found below 1573 K. The solution could be described as 3CaO+xV₂O₅+(1−x) P₂O₅. The solid solutions at three compositions, namely, X=1/3, X=1/2, and X=2/3, were synthesized. X-ray diffraction (XRD) patterns revealed that the crystals exhibited a rhombohedra structure. X-ray indexes at these compositions were reported.     

Thermodynamics of iron oxide in Fe x O-dilute CaO+Al2O3+Fe x O fluxes at 1873 K

The distribution of iron between Fe _x O-dilute CaO+Al₂O₃+Fe _x O fluxes and Pt+Fe alloys, as well as the redox equilibrium of iron ions in these fluxes, was experimentally investigated in pressure-controlled CO₂/CO gas at 1873 K. Total iron content in flux (pct Fe ^T ) and the ratio of (pct Fe²⁺) to (pct Fe ^T ) in fluxes with constant can be related to the activity of iron, α _Fe, and the partial pressure of oxygen, a _Fe, using the following equation:

Thermodynamics of iron oxide in Fe x O-dilute CaO + Al2O3 + MgO + Fe x O slags at 1873 K

In order to determine the ferrous and ferric ion capacities: 3

固体CaO在3CaO·P2O5-2CaO·SiO2饱和熔渣中的溶解及反应机理

摘要：为了深入了解非均相脱磷剂中固体CaO在3CaO·P2O5-2CaO·SiO2（C2S-C3P）饱和熔渣中的溶解及反应机理，采用静态浸入法和旋转圆柱法研究固体CaO在C2S-C3P饱和CaO-SiO2-FetO-P2O5（10%）渣中的溶解行为，运用FESEM/BSED EDS对固体CaO和熔渣界面进行了观察，分析了固体CaO与C2S-C3P饱和熔渣间的反应机理。结果表明，加强对熔池的搅拌，能够加快固体CaO在熔渣中的侵蚀速度和溶解速度；发现了固体CaO在饱和熔渣中的溶解数量受熔渣中FeO通过边界层向固体内部渗透深度的影响，FeO渗透深度越深，溶解越多；固体CaO先与熔渣中的硅和磷反应生成磷含量低的C2S-C3P固溶体，待一段时间后，最终生成磷含量高的Ca5(PO4)2SiO4。     

The electrical conductivity of some liquids in the system CaF2+CaO+Al2O3

The conductivity of slags in the binary systems CaF₂+Al₂O₃, CaF₂+CaO and the ternary system CaF₂+CaO+Al₂O₃ has been measured, using a four-lead electrode technique at a frequency of 1 kHz. The cell design used ensured that only molybdenum metal was in contact with the slag at high temperature and that the slag was wholly contained in molybdenum. No frequency dispersion could be detected at frequencies between 0.8 to 10 kHz. It is suggested that the formation of complex ions (e.g. AlO₂F₂ ³⁻ and AlOF ₂ ⁻ ) might account for the observed effects in CaF₂+Al₂O₃, CaF₂+CaO+Al₂O₃ liquids as has been previously suggested. an oxide ion clustering mechanism may explain the conductivities found in CaF₂+CaO.     

Chemical Potentials of Oxygen in Four‐Phase Assemblages of the System CaO‐P2O5‐CaF2‐FexO

In steelmaking processes, because of environmental requirements and health considerations, there is a strong incentive to reduce slag volume. The key to meet this requirement is the better understanding of phosphorus removal, which relies on the knowledge of the thermodynamic properties of slags and fluxes used for dephosphorization. In this study, the liquidus compositions of the four‐phase assemblages in the quaternary system CaO‐P₂O₅‐CaF₂‐Fe_xO were determined at 1573K by employing electron probe microanalysis. Measurements were also made on the Fe_xO activities at temperatures between 1523K and 1673K by employing an electrochemical technique involving stabilized zirconia electrolyte.     

Electrochemical Measurements of Oxygen Potentials in the Slag System CaO‐P2O5‐SiO2‐FexO

The liquidus compositions of the four‐phase assemblages in the quaternary system of CaO‐P₂O₅‐SiO₂‐Fe_xO were determined at 1473 and 1573 K by employing electron probe microanalysis. Measurements were also made on the Fe_xO activities at temperatures between 1373K and 1699K by employing an electrochemical technique involving stabilized zirconia electrolyte.     

X射线荧光光谱法测定矾土中硅、铁、钾、钙、钛、锰、铝、镁、磷等氧化物含量

建立了X射线荧光光谱法测定矾土中硅、铁、钾、钙、钛、锰、铝、镁、磷等氧化物的方法。以四硼酸锂做熔剂、溴化锂做脱模剂制备玻璃熔片 ,以标准物质和高纯试剂制备标准片做校正曲线 ,并对吸收增强效应和光谱重叠做出校正。通过测定标准样品进行比较 ,本法没有显著性差异。回收率为 86.7%～ 10 6.2 %。     

The Activities of FexO in {CaO‐SiO2‐Al2O3‐MgO‐FexO} Slags at 1723 K

In Japanese steelworks, hot metal is now produced by scrap melting process. With this process removal of sulphur is very much handicapped because of very high sulphur levels (0.04 to 0.09 pct by weight) and relatively low tapping temperatures (1623 to 1723 K). In order to overcome such disadvantages, the authors explored on the phase diagrams of {CaO‐SiO₂‐Al₂O₃‐MgO} slags, and this research revealed that those slags at 35 wt%‐Al₂O₃ would be good candidates as reagents for the removal of sulphur from high sulphur hot metal at relatively low temperatures. For better understanding of the thermodynamic properties of the candidate slags, in this study, activities of Fe_xO were determined by using solid‐state electrochemical cells incorporating MgO‐stabilized zirconia and Mo + MoO₂ reference electrode.     

Activities of FexO in CaO‐(Na2O)0.1875(K2O)0.0625(Al2O3)0.25(SiO2)0.5‐FexO Pseudo‐Ternary Slags

Activities of Fe_xO in CaO‐(Na₂O)_0.1875(K₂O)_0.0625(Al₂O₃)_0.25(SiO₂)_0.5‐Fe_xO pseudo‐ternary slags were determined at 1673K by using a solid‐oxide galvanic cell; The substitution of (Na₂O)_0.1875(K₂O)_0.0625(Al₂O₃)_0.25(SiO₂)_0.5 for CaO has an effect of raising the Fe_xO activities.