Papers by Keyword: Phase Equilibrium

Abstract: Thermodynamic equilibrium of Fe-36Ni-base Invar alloy containing C contents from 0.25 to 0.38 weight per cent during solidification has been investigated in this study. From the thermodynamic simulation using ThermoCalc®, it has been revealed that equilibrium phases which can be formed are two kinds of MC-type precipitates, i.e. (Nb, Mo, V)C and MoC, and M₂C carbides. The MoC carbide was expected to be formed at relatively lower temperature below 770^oC. Microstructure observation revealed the coarse precipitates in the as-cast ingots, which was Mo-rich non-equilibrium phase and could be resolved by the successive heat treatment. With increasing C contents from 0.25 to 0.38 wt.%, tensile strength of Invar alloy increased from 950 to 1100MPa after hot rolling and thermal expansion coefficient showed a trivial increase. Hot-rolled Invar alloy was successfully drawn at room temperature from 6 to 4 mm in diameter, which dramatically decreased thermal expansion coefficient.

Abstract: It is well known that the phase diagram plays an important role in exploitation and utilization of salt lake resources. To effectively employ the systems containing lithium and carbonate, the study on phase equilibrium is essential to the comprehensive utilization of the salt lake resources. In this paper, progresses on phase equilibria of salt-water systems containing lithium and carbonate were presented.

Abstract: It is well known that the comprehensive utilization of salt lake resources can not only create a good economic benefit, but also effectively protect ecological environment of salt lake and achieve sustainable development. After potassium separating for potassium fertilizer from salt lakes, the rest of mother liquor brines are rich resources of magnesium and boron. Research on phase equilibria of salt-water systems containing magnesium and borate can provide reference data for comprehensive development and utilization of salt lake resources.

Abstract: It is well known that phase equilibria and phase diagrams can successfully guide the comprehensive utilization of the salt lake resources. The researches on phase chemistry and thermal chemistry of the calcium-containing brine system are essential to promote the development of brines. In this paper, the progresses on the phase chemistry and thermal chemistry of the calcium-containing brine system around the world from 2007 up to now were summarized. The problems existed and the new trends in the future were also carried out.

Abstract: In this paper, phase equilibrium of Li⁺, Mg²⁺∥Cl^-, SiO₃^2--H₂O system at 220°C was researched. The solid phases were characterized by X-ray diffraction (XRD). Lithium silicate, hectorite, karpinskite and magnesium hydroxide were observed as solid phases. According to the analysis of XRD, the phase diagram was obtained. The phase diagram could be used as the theoretical principle for synthesis of hectorite.

Abstract: Inadequacy was discussed of using acid dew point temperature (ADT) as safe low limitation of exhaust gas temperature on the background of waste heat deep utilization of flue gases. Concept of limited corrosion dew point (LCT) was presented based on corrosion property of ordinary carbon steel and binary phase equilibrium of H₂SO₄-H₂O system,. Calculation formula of LCT was solved by establishing fugacity equation of H2O with a fixed concentration and constant pressure. The results show that LCT lies during 68-84°C when volume percentage of H₂O vapor varies from 6-12% which is in line with that of exhaust gas of boiler. The maximum relative error of the calculated data is 1.43% in contrast to reported data. Ordinary carbon steel in contact with flue gas with its surface temperature above LCT will not occur obvious corrosion and wet soot deposition through observation of experiment on site. It is available for exhaust gas temperature to decline below ADT but above LCT in process of deep utilization of waste heat of flue gas.

Abstract: In order to understand the composition of the Nb-Mo bcc phase suitable to introduce B2-NiAl phase for the improvement of oxidation resistance as an Al reservoir layer for maintaining Al₂O₃ surface layer, a NiAl-Nb-Mo section of the quaternary Al-Nb-Ni-Mo phase diagram is studied. It is found that the ternary τ₂ phase appears in wide composition range of alloys, both the hardness and cracking tendency decreases with increasing the Mo concentration of the alloys.

Abstract: The ternary system of solid-liquid phase equilibrium relation of KCl-NH₄Cl-H₂O was studied at 80 °C. The solubility data of KCl and NH₄Cl in water were obtained by isothermal equilibrium method, and the phase diagram of the system was plotted. The result showed that this system exist six phase regions: i.e. the unsaturated solution region, pure KCl , pure NH₄Cl, the solid solution base of KCl, the solid solution base of NH₄Cl and their common crystallization region with the solid solution base of KCl and the solid solution base of NH₄Cl crystallization regions. Some crystallization area will be changed with the various temperature, According to the phase diagram, it can be calculated the quantity of evaporated water in the crystallization process of KCl-NH₄Cl-H₂O and controlled the change of concentration in the evaporation process preferably.

Abstract: Citronellal, citronellol and geraniol are the main components of the natural plant citronella oil, and their vapor-liquid phase equilibrium relationship is the critical data to separate, purify the citronella oil and design rectifying column. Citronella oil is a thermo-sensitive material, so the separation under high vacuum conditions could lower its boiling point and maintain its quality. This paper adopts the precise vapor-liquid phase equilibrium instrument to collect the binary system of citronellal-citronellol, citronellal-geraniol and citronellol-geraniol with the absolute pressure of 1.2kPa. Meanwhile, the corresponding phase equilibrium diagrams are drawn, which provide data support for the distillation of citronella oil.

Abstract: Alloys with different compositions in Mg-rich corner of Mg-Zn-La system at 150°C were prepared, and the phase equilibrium in Mg-Zn-La alloys were determined by scanning electron microscopy (SEM), electron probe microanalysis based on energy dispersive X-ray spectroscopy (EPMA-EDS) and X-ray diffraction (XRD). The stability, compositions and lattice structures of the intermetallic compounds of Mg-Zn-La alloys were identified. The results show that, there exists a ternary compound (T-phase) with constant La (about 8at%) and the changed ratio of Mg/Zn in the Mg-rich corner of Mg-Zn-La system. Though the ratio of (Mg, Zn)/La of T-phase is close to that of Mg/La of Mg₁₂La, the T-phase was not the binary solid solution of Mg₁₂La because of the difference of the lattice structure. It also reveals that T-phase is a stable phase, and it is in two-phase equilibrium of T-phase+Mg at 150°C.