Thermodynamic analysis of strontium deoxidizing ability in liquid iron at presence of aluminum

Phase diagram of the ternary oxide system FeO - SrO -Al2O3 was constructed for the first time. In this system, the following compounds can be formed: hercynite FeAl2O4 and five strontium aluminates - Sr4Al2O7 , Sr3Al2O6 , SrAl2O4 , SrAl4O7 , SrAl12O19 . According to the calculations performed, solid solutions of oxides are not formed in the system, as it is confirmed by the literature data. In the course of modeling, the optimal energy parameters of the theory of subregular ionic solutions were selected for the components of the oxide melt (FeO, SrO, Al2O3 ). Thermodynamic analysis of strontium deoxidizing ability in liquid iron at presence of aluminum was carried out using the technique for constructing the surface of solubility of strontium and aluminum in metal for steelmaking temperatures (1550 and 1600 °C) and carbon concentrations of 0.1 and 0.4 %. The equilibrium constants of the reactions of formation of strontium aluminates Sr3Al2O6 and SrAl2O4 from the components of the metal melt were calculated for the temperature range of 1550 - 1650 °C. It was found that the rest of strontium aluminates can be formed in liquid metal only at temperatures above 1750 °C. The base of thermodynamic data for the studied systems is given: temperature dependences of equilibrium constants for reactions occurring between components; values of interaction parameters of the first order (according to Wagner) for elements in liquid iron; values of energy parameters of the theory of subregular ionic solutions (for oxide melt). It follows from the calculations that the formation of strontium monoaluminate SrAl2O4 and corundum Al2O3 is most probable as the interaction products in Fe -Al - Sr - O and Fe -Al - Sr - C - O systems.

Measurement of Solubility of CO2 in NaCl, CaCl2, MgCl2 and MgCl2 + CaCl2 Brines at Temperatures from 298 to 373 K and Pressures up to 20 MPa Using the Potentiometric Titration Method

Understanding the carbon dioxide (CO2) solubility in formation brines is of great importance to several industrial applications, including CO2 sequestration and some CO2 capture technologies, as well as CO2-based enhanced hydrocarbon recovery methods. Despite years of study, there are few literature data on CO2 solubility for the low salinity range. Thus, in this study, the solubility of CO2 in distilled water and aqueous ionic solutions of NaCl, MgCl2, CaCl2 and MgCl2 + CaCl2 were obtained in a low salinity range (0–15,000 ppm) at temperatures from 298–373 K and pressures up to 20 MPa using an accurate and unconventional method called potentiometric titration. An experimental data set of 553 data points was collected using this method. The results of the experiments demonstrate that increasing pressure increases the solubility of CO2 in various brines, whereas increasing temperature and salinity reduces the solubility. The role of different ions in changing the solubility is elaborated through a detailed discussion on the salting-out effect of different ionic solutions. To verify the experimental results of this research, the solubility points obtained by the potentiometric titration method were compared to some of the well-established experimental and analytical data from the literature and a very good agreement with those was obtained.

Thermodynamic Assessment of Phase Equilibria in the SrO-Al2O3 System

Thermodynamic modeling of phase equilibria with the subsequent construction of the phase diagram of the SrO–Al2O3 system has been carried out. To calculate the activities of the oxide melt in the course of this work, we used the approximation of the theory of subregular ionic solutions, with the most optimal values of the energy parameters Q1112 = –104 349: Q1122 = –217 689; Q1222 = –104 436 J/mole. The results obtained for the liquidus line in this work are in good agreement with the literature experimental data. In the course of the calculation, the values of the equilibrium constants for the formation of strontium aluminates from the components of the oxide melt were estimated.

Effect of PCE on Properties of MMA-Based Repair Material for Concrete

Methyl methacrylate (MMA)-based repair material for concrete has the characteristics of low viscosity, excellent mechanical properties, and good durability. However, its application is limited due to its large shrinkage. Existing studies have shown that adding perchloroethylene can reduce the shrinkage. On this basis, other properties of modified MMA-based repair materials were tested and analyzed in the present study. The results revealed that the addition of perchloroethylene (PCE) can hinder the polymerization reaction of the system. When CaCO3 with a mass fraction of 30% was added, the viscosity of the material was within the range of 450–500 mPa·s, and the shrinkage decreased to approximately 10%. The bending strength of MMA, and MMA modified by PCE, repair materials at 28 days could reach up to 28.38 MPa and 29.15 MPa, respectively. After the addition of HS-770 light stabilizer with a mass fraction of 0.4%, the retention ratios of the bending strength of materials with ratios of P0 and P3 could reach 91.11% and 89.94%, respectively, after 1440 h of ultraviolet radiation. The retention ratio of the bending strength of the material could reach more than 95% after immersion in different ionic solutions for 90 days.