Display omitted
•A new structure model was established through ring statistics by MD simulation.•The influence by Na2O/CaO on structure and viscosity was quantified by ring distribution.•Na2O and CaO ...change the diffusivity in structure to lower liquidus temperature.•Ca2+ has a better ability to destroy Si-O, while Na+ has a higher diffusivity than Ca2+.
Molecular dynamics simulation was applied to investigate the microstructure of slag in SiO2-Al2O3-CaO-Na2O system. A new structure model for slag was established through ring-statistics by MD simulation. The network structure was simplified into crosslinked rings divided into three types based on the ring size. The change of amorphous structure was well described by ring distribution. The destruction of slag structure by Ca2+ is more significant than Na+, and high CaO/Na2O resulted in low content of medium and large rings and low viscosity. The ring distribution coefficient (Rdc) was defined to establish the relationship between structure and viscosity: ŋ=26.7Rdc-10.2. When CaO/Na2O ratio increases, the ring distribution transforms from medium or high-order to low-order, leading to the decreasing of Rdc and slag viscosity. Moreover, CaO/Na2O ratio also changes the diffusivity of slag and thus the melting behavior. Finally, a linear relationship between the empirical liquidus temperature (Tliq) and atomic diffusivity from the MD simulations was obtained.
•Liquidus temperatures of CaO-SiO2-TiO2 based blast furnace slags with different MnO content were determined.•The influences of superheat degree and MnO content on structure of quenched ...CaO-SiO2-TiO2-MnO slags were clarified.•The relationship between slag viscosity and structure was discussed.
High-temperature equilibration experiments were carried out to investigate the liquidus temperature of CaO-SiO2-TiO2-MnO slags, and the addition of MnO into the slag could decrease the liquidus temperature. Furthermore, Raman spectra of CaO-SiO2-TiO2–1wt%MnO quenched slags under various superheat degrees and slags with different MnO content were also studied to uncover the slag structure characteristics. Higher superheat degree mainly simplified the complicated structural units of CaO-SiO2-TiO2–1wt%MnO slags by promoting to form simpler silicate units. Increasing the MnO content in the slag could provide more free oxygen ions to break the Si-O bond of polymerized silicate units and weaken the silicate network stability. The relationship between slag viscosity and nBO was fitted, and the viscosity (lnη) linearly increased with increasing the nBO. To some extent, the fitted expression could reflect the relationships of the slag viscosity and structure.
The electrical conductivity of LiCl?GdCl3 molten systems with the gadolinium chloride additions ranging from 0 to 23 mol % was measured depending on both the temperature and concentration of GdCl3. ...The molar conductivity of the molten GdCl3?LiCl system is calculated taking into account the assumption of additivity of the molar volume of the mixture. The obtained temperature dependencies can be approximated by Arrhenius-type equation. The effective activation energy, Ea, increased with the GdCl3 content. The liquidus temperatures of the studied systems were determined by differential scanning calorimetry. The high-temperature Raman spectra of LiCl?GdCl3 chloride melts were recorded. In addition, the conductivity of 0.77LiCl?0.23GdCl3 molten system with 1 mol % of Gd2O3 was measured. The investigation demonstrates that the addition of gadolinium oxide results in a decrease of the conductivity of the chloride molten system and growth of its liquidus temperature
Segregation in the solidification process and discontinuous precipitation during aging cause the service and processing performance of Cu–Ni–Sn alloys deteriorating severely. In this work, Si is ...added as a fourth element for the design of Cu80Ni15Sn5−xSix (x = 0, 0.625, 1.25, 1.875, 2.5) series alloys using cluster-plus-glue-atom model to solve these issues from the point of composition design. The results suggest that the introduction of Si leads to the disappearance of the lamellar structure formed in the as-cast alloys while also inhibiting discontinuous precipitation during aging. The solidus–liquidus temperature range is reduced with the addition of Si, and this strategy is most effective when the Si is in the solution state. With increasing Si content, the high-temperature conductive stability of the alloys is improved. Moreover, the hardness and conductivity of the Cu80Ni15Sn5 alloy designed by cluster-plus-glue-atom model are improved compared with those of C72900 (Cu78.96Ni16.65Sn4.39) commercial alloy, and the properties of Cu80Ni15Sn4.375Si0.625 alloy are basically equivalent to those of C72900 alloy. These findings indicate that alloys with excellent synthetic properties can be produced as long as the content and existential state of Si are reasonably controlled.
Display omitted
•The precipitate clusters of Cu-Ni-Sn alloy are interpreted for the first time.•A series of Cu-Ni-Sn (Si) alloys are designed by the cluster-plus-glue-atom model.•The existential state of Si in the alloy is confirmed.•The new Cu80Ni15Sn4.375Si0.625 alloy with excellent synthetic properties is obtained.
Fluidity is one of the important properties of bonding phase in sintering process, because better fluidity is beneficial for improving the strength of sinter. In this work, the effects of liquidus ...temperature and liquid amount on the fluidity of bonding phase and the strength of sinter were investigated. The experimental results in SiO2–Fe2O3–CaO system indicated that, for both SiO2=5% and SiO2=10%, with increasing Fe2O3 content (decreasing CaO content), the fluidity indices of samples first increased and then decreased. When the liquidus temperature was lower and the liquid amount was more, the fluidity index of SFC sample was higher, and vice versa. The sinter pot experimental results showed that, (1) for the iron ore with SiO2=4.30%, the major phases in the sinter were hematite and SFCA, and the liquid SFCA phase was evenly distributed in sinter. The tumble strength of sinter was higher than 60% in a wider basicity range of 1.8–2.2. (2) For the iron ore with SiO2=12.42%, the olivine was another major phase, and was unevenly distributed in part of sinter. There was a peak value for tumble strength of sinter when the basicity was 2.0. The basicity was higher or lower, the tumble strength sharply decreased. The reasonable basicity of sinter with high-SiO2 content was difficult to determine, and was not proposed to be used in an actual sintering production. The outcomes of the present work may provide guidelines for better understanding the properties of bonding phase and improving the strength of sinter.
Fluidity is one of the important properties of bonding phase in sintering process, because better fluidity is beneficial for improving the strength of sinter. In this work, the effects of liquidus ...temperature and liquid amount on the fluidity of bonding phase and the strength of sinter were investigated. The experimental results in SiO2–Fe2O3–CaO system indicated that, for both SiO2=5% and SiO2=10%, with increasing Fe2O3 content (decreasing CaO content), the fluidity indices of samples first increased and then decreased. When the liquidus temperature was lower and the liquid amount was more, the fluidity index of SFC sample was higher, and vice versa. The sinter pot experimental results showed that, (1) for the iron ore with SiO2=4.30%, the major phases in the sinter were hematite and SFCA, and the liquid SFCA phase was evenly distributed in sinter. The tumble strength of sinter was higher than 60% in a wider basicity range of 1.8–2.2. (2) For the iron ore with SiO2=12.42%, the olivine was another major phase, and was unevenly distributed in part of sinter. There was a peak value for tumble strength of sinter when the basicity was 2.0. The basicity was higher or lower, the tumble strength sharply decreased. The reasonable basicity of sinter with high-SiO2 content was difficult to determine, and was not proposed to be used in an actual sintering production. The outcomes of the present work may provide guidelines for better understanding the properties of bonding phase and improving the strength of sinter.
The equilibrium phase relations of the CaO–SiO2–TiO2–Al2O3–MgO system were investigated experimentally in air at 1250–1400 °C using a high-temperature equilibration/quenching technique, followed by ...direct phase analysis by scanning electron microscopy equipped with X-ray energy dispersive spectroscopy. The equilibrium solid phases of silica, rutile, and pseudobrookite solid solution were found to coexist with the liquid phase. The 1300–1400 °C isothermal sections were constructed based on the experimentally measured liquid compositions. The experimental results were compared with simulations using MTDATA and FactSage thermodynamic software and their databases. This study provides guidelines for the selective crystallization of pseudobrookite from titania-bearing slag.
Modeling statistical relationships between the network structural groups (S) derived from Fourier transform infrared (FTIR) spectroscopic analysis and various properties (P) is discussed in this ...article, focusing on a wide range of K2O, MgO, and Al2O3 in a single baseline Nd: phosphate glass composition (C). Properties covered by this study are emission cross-section, effective linewidth, fluorescence lifetime, liquidus temperature, coefficient of thermal expansion, and nonlinear refractive index. Both S-P models and C-S models were established; the former demonstrated sufficiently high predictability (R2>0.97 and Radj2>0.96) for all cases. In designing a new glass composition that simultaneously meets multiple target properties, especially for dealing with nonlinear property responses to composition variations, the final C-S-P database is constructed by combining S-P and C-S models. Moreover, the C-S-P validation tests were performed by using “bi-directional” modeling steps, P→S→C and C→S→P.
•Liquidus temperatures of CaO-SiO2-Fe2O3-TiO2 slags with different TiO2 content were measured.•The effects of TiO2 and superheat degree on Raman spectra of the quenched CaO-SiO2-Fe2O3-TiO2 slags were ...discussed.•The influence mechanism of TiO2 and superheat degree on the slag network structure was clarified.
The liquidus temperature of CaO-SiO2-Fe2O3-TiO2 slags was studied using the HTCLSM and high temperature equilibration and quenching method in this work. Furthermore, Raman and XPS spectra of quenched slags with various TiO2 content under the same superheat degree and the CaO-SiO2-Fe2O3-5wt%TiO2 slag at different quenched temperatures were studied to reveal the structure characteristics of the slags. From the HTCLSM and quenched experiment, the slag liquidus temperature decreased with adding TiO2. The analysis results of Raman and XPS spectra indicated that TiO2 could depolymerize the slag network structure under the same superheat degree by increasing the fraction of free oxygen, forming new weaker Ti-O bonds and reducing the quantity of complex silicate units. The increase of the superheat degree could also decrease the polymerization degree and simplify the structure of CaO-SiO2-Fe2O3-5wt%TiO2 slags, which could decline the complexity of structural units and promote the transformation of polymerized units from complex to simple.
PDF
