CaO SiO2 Research Articles

Solubility of Gold in FeO–SiO2–CaO–Al2O3–MgO Slag for Smelting of Gold-Containing Secondary Resources

Solubility of Gold in FeO–SiO2–CaO–Al2O3–MgO Slag for Smelting of Gold-Containing Secondary Resources

Optimization of the optical properties and γ-buildup factors of Na2O–CaO–SiO2 glasses reinforced with Cd2+ and Fe3+ ions: potential use in optical and radiation shielding applications

Optimization of the optical properties and γ-buildup factors of Na2O–CaO–SiO2 glasses reinforced with Cd2+ and Fe3+ ions: potential use in optical and radiation shielding applications

Influence of the substitution of CaO by SrO on the structure, degradation and in vitro apatite formation of sol–gel derived SiO2–CaO–SrO–P2O5system bioactive glasses

The present study investigates the influence of the substitution of CaO by SrO on the structure, degradation and in vitro apatite formation of sol–gel-derived bioactive glasses with composition of 58SiO2–(38-x)CaO–xSrO–4P2O5, where x varies between 0 and 10 mol.%. The IV-type nitrogen adsorption/desorption isotherms and pore size values (ranging from 5.41 to 12.56 nm) confirmed the mesoporous structure of the synthesized glasses. The detailed structural analysis was carried out by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). As network modifiers, the addition of Ca and Sr oxides disrupted the bonds of bridging oxygens (BOs) and resulted in the formation of non-bridging oxygens (NBOs), where the substitution of Ca with Sr led to an increase in Q1 units and a decrease in Q3 units. The effects of the addition of Sr on sample degradation and apatite formation were assessed using an assay in tris-(hydroxymethyl)-aminomethane and hydrochloric acid (Tris–HCl) and simulated body fluid (SBF). The results demonstrated that the substitution of CaO by SrO in the CaO–SiO2–P2O5 bioglass system altered the glass structure, resulting in reduced sample degradation and delayed apatite formation. This suggests that the incorporation of Sr into bioactive glasses may serve as a promising strategy to regulate the structure, dissolution behavior and apatite formation of silicate-based glasses, particularly concerning their long-term applications within the human body.

Characterization and 3D Reconstruction of the Crushing Behavior of SiO2–CaO–Al2O3–MgO Complex Inclusions in Spring Steel with High Basicity Slag Treatment

This article mainly studies the element content, phase composition, and fragmentation mechanism of SiO2–CaO–Al2O3–MgO composite inclusions that cause fatigue fracture of spring steel. The study found that the SiO2–CaO–Al2O3–MgO composite inclusions in the wire rod are not a homogeneous phase. According to the electron microscopy energy spectrum analysis results, although the SiO2–CaO–Al2O3–MgO composite inclusion is in the low‐melting‐point area of the phase diagram according to the component content ratio. However, field‐emission transmission electron microscopy analysis reveals that this type of composite inclusions includes MgAl2O4, CaAl2Si2O8, CaSiO3, MgSiO3, and a small amount of CaS. The Zeiss Crossbeam 550 electron microscope is used to conduct a three‐dimensional reconstruction analysis of this type of composite inclusions, which once again verified that the composition of this type of inclusions includes calcium silicate, MgAl2O4, MgO, and other phases. It is also found that there is a certain gap between the inclusions and the matrix, and the gap between the inclusions with high‐melting‐points such as MgAl2O4 and MgO and the matrix is more obvious. During the rolling process of SiO2–CaO–Al2O3–MgO composite inclusions, due to differences in hardness and deformation rate between different phases, the rolling process is deformed and fragmented for extended periods.

Crystallization Behavior and Structure of CaO–SiO2–Al2O3 Melts Representing the Oxide Inclusions in Si‐Mn Deoxidized Steel

For further optimization of the inclusion plasticization control process of Si‐Mn deoxidized steel, the crystallization behavior and structure of CaO–SiO2–Al2O3 system inclusions are investigated. The crystallization behavior of four typical low melting point CaO–SiO2–Al2O3 inclusions at 1000 to 1250 °C is studied by steel crucible isothermal heating experiment. The obtained results reveal that the glassy stability of the inclusions is high when the composition of low melting point inclusion is located in the eutectic region of tridymite, pseudowollastonite, and anorthite in the ternary phase diagram. However, when the composition of the inclusion is located in the eutectic region of melilite, pseudowollastonite, and anorthite, it is easy to undergo glass‐crystallization transformation and precipitate wollastonite and anorthite crystalline phases when isothermal heating at 1100 to 1200 °C. In addition, the crystallization mode of these inclusions is mainly surface crystallization, and the crystallization degree of inclusions increases with the increase of heat treatment temperature and time. The activation energy of crystallization and the content of nonbridging oxygen in the silicate structure NBO/T can be used to predict the crystallization ability of inclusions. The greater the activation energy of crystallization and the smaller the NBO/T value, the higher the glassy stability of the inclusions.

Structure and dynamic viscosity of CaO–SiO2 and CaO–SiO2–B2O3 model slag systems

Correlation dependencies between the dynamic viscosity of slag and its structural parameters were studied to determine an optimal basicity of silicon smelting slag under the addition of boron oxide to eliminate slagging of the bottom of ore-smelting furnaces. Experimental studies were conducted on CaO–SiO2 and CaO– SiO2–B2O3 model slags obtained at 1600°С. Raman spectroscopic analysis was carried out using a Horiba JobinYvon HR800UV analyzer (France). Theoretical calculations of slag viscosity were performed using Urbain and Mills models. During the experiments, the key structural parameters of slag systems varied within the following limits: the experimental Raman spectrum deconvolution function from 1.41 to 2.45 and optical basicity from 0.58 to 0.68. The obtained experimental and theoretical data were related by mathematical dependencies. It was found that the dynamic viscosity of slag can be promptly determined by Raman spectroscopy on the basis of mathematical models. The dependence obtained shows that slag viscosity decreases upon an increase in the number of bridging oxygen atoms in the silicate anion structure. Notably, this decrease in slag viscosity is observed up to the value of the experimental Raman spectrum deconvolution function of ~1.55-1.60 or slag optical basicity of 0.60–0.62. When B2O3 is added, the viscosity undergoes a further decrease. In practice, for CaO–SiO2 slag systems, the use of boroncontaining flux as a liquefying agent is reasonable at CaO/SiO2 = 0.61–0.63 while maintaining the content of B2O3 in the slag at a level of 1%. The two models (classical and modified) proposed by Urbain were established to be more suitable for theoretical calculation of viscosity in CaO–SiO2 and CaO–SiO2–B2O3 systems. Mills’ model is not suitable for these purposes, since the correlation coefficients in the corresponding mathematical model are not sufficiently large. Further research in this direction is required in order to establish appropriate dependencies of slag viscosity on its structural parameters at different temperatures.

An innovative approach towards decolorization of tint and enhancing the optical & physical properties of high iron Na2O–CaO–SiO2 glass by co-doping with Ce4+/Nd3+: An experimental and comparative study

The aim of the research is to manufacture the colourless high iron Na2O–CaO–SiO2 glass with natural local raw materials with high iron content. Chemical and physical decolorizer like CeO2 and Nd2O3 were used in oxidation conditions by maintaining the redox of the melt. The maximum transmittance of colourless glass obtained at 546–562 nm is 91 % with a thickness of 6.5 mm. The addition of polyvalent ions Nd2O3/CeO2 decreases the optical band gap (Eg) and Urbach energy (ΔE) which results in resistance against solarization. Additionally, it also decreases the structural disorder results in high young & shear modulus. Lack of O–H in glass facilitates to retain more Si–O–Si in the glass matrices which enhances the down conversion luminance intensity of Nd3+ from 4I9/2 to 4F5/2 and improves the Far-IR behavior of the glass. Chromaticity diagram revealed that the doped glass has CI value 5416K which is closes to white light emission 5500k. Due to the presences of the Nd2O3/CeO2 and antimony oxide the Refractive index (ng), density (ρ), molar volume (V) and molecular weight of the glass increases. Maintaining the redox of the glass melt and Fe2+/Fe3+ ratio with the chemical and physical decolorizer will help to decolourize the Na2O–CaO–SiO2 glasses with the Fe2O3 content up to 0.3 % with the same methodology.

Effects of CaF2 and La2O3 on the phase structure of rare earth in CaO–SiO2–La2O3–CaF2 slags

The rare earth in the rare earth slag can be separated and enriched by heating and melting the rare earth slag and then slowly cooling crystallisation. In this process, it is of great significance to study the effect of chemical composition on the crystallisation of rare earth phase in slag and the effect of slag viscosity on crystal growth. The rare earth slag melt samples were prepared according to the main chemical composition of rare earth slag by using an analytical pure reagent. The effects of CaF2 and La2O3 contents on the phase structure and morphology of rare earth phase in CaO–SiO2–La2O3–CaF2 slags were studied by SEM-EDS and XRD. The relationship between the viscosity of the slag and the crystal growth behaviour was studied by measuring the melt viscosity with the cylinder rotation method. The results show that the rare earth in CaO–SiO2–La2O3–CaF2 slags exists in the form of CaLa4(SiO4)3O. The change of CaF2 and La2O3 content has no effect on the structure of rare earth phase, but the size of rare earth crystal phase changes obviously. With the increase of CaF2 and La2O3 content, the size of rare earth crystal phase increases gradually. CaF2 and La2O3 can reduce the viscosity transition temperature of slag melt and increase the crystallisation temperature range of rare earth phase to promote crystal growth.

Experimental Determination of Slag Emissivities for Enhanced Slag Control by Infrared‐Based Systems

For today's high‐quality steel production, good control of slag composition is essential in secondary steelmaking. However, the conventional slag analysis practice, involving sampling, sample preparation, and analysis, is very time‐consuming. This work is the first step toward an investigation of infrared (IR)‐based systems and can be used for online slag composition monitoring using the principle that different slag compositions have different emissivities in the IR wavelength range. Therefore, this work experimentally determines emissivity values of slags as a function of composition at steelmaking temperature, since available data for slags are very limited in the literature. The emissivities of three different slag compositions belonging to the Al2O3–CaO–SiO2–MgO system are investigated at 1773 K. The investigated emissivities are in the range of 0.75–0.87, with the best repeatability seen in the slag which is fully liquid at 1773 K. Variations in emissivities are observed within the other slags due to the presence of solid phases. Although the data clearly indicate a difference of emissivities as a function of slag composition, further experiments must be performed to evaluate the emissivities of other characteristic slags at different temperatures in order to further assess the applicability of IR‐based systems for slag composition control.

Phase Equilibria Study of the MgO–CaO–SiO2 Slag System with Ferronickel Alloy, Solid Carbon, and Al2O3 Additions

Phase Equilibria Study of the MgO–CaO–SiO2 Slag System with Ferronickel Alloy, Solid Carbon, and Al2O3 Additions

Effect of MgO on Crystallization Behavior of CaO–SiO2–Al2O3 Inclusions in Si–Mn Deoxidized Steel During Solidification Stage

Effect of MgO on Crystallization Behavior of CaO–SiO2–Al2O3 Inclusions in Si–Mn Deoxidized Steel During Solidification Stage

Unveiling Droplet Zone Element Transfer Behaviors of CaO–SiO2–MnO Fluxes in the EH36 Shipbuilding Steel Subject to Submerged Arc Welding

Unveiling Droplet Zone Element Transfer Behaviors of CaO–SiO2–MnO Fluxes in the EH36 Shipbuilding Steel Subject to Submerged Arc Welding

Bentonite Clays Related to Volcanosedimentary Formations in Southeastern Spain: Mineralogical, Chemical and Pozzolanic Characteristics

The volcanism that took place during the Neogene in the southeastern Iberian Peninsula caused a large accumulation of volcanosedimentary materials, which were subsequently altered and transformed into bentonite deposits. The mineral composition and technical quality of these deposits have been demonstrated and established in this work. The main object of this research is the mineral, chemical and thermal characterization of the bentonites that lie in the southeastern region of Spain and to demonstrate their technical capabilities to be used as pozzolans. The first phase of characterization of the samples was carried out by X-ray diffraction (XRD), oriented aggregates (OAs), X-ray fluorescence (XRF) and thermogravimetric analysis (TGA). In the second phase, a chemical–technical quality test (CTQT) was carried out, aimed at determining reactive SiO2 and reactive CaO, whereas in the third phase, a chemical pozzolanicity test (CPT) was carried out to establish the pozzolanic behavior of the samples over two test periods: 8 and 15 days. The XRD and OA analyses showed that the bentonite samples are made up of a main phase formed by montmorillonite, quartz, plagioclase-albite and chabazite–Ca. The results obtained by XRF on the bentonite samples indicated that the SiO2 contents are high and vary between 43.33% and 64.71%, while Al2O3 ranges between 15.81% and 17.49%. The CTQT established that more than 80% of the SiO2 and CaO present in the samples are reactive, which was confirmed by the results of the chemical pozzolanicity test (CPT). The results obtained show that the bentonites in this study present technical qualities that are undoubtedly reinforced by their mineral constitution and chemical composition. These tests could become a practical guide for the selection of eco-efficient materials in the production of pozzolanic cements and environmentally friendly ceramic products.

Electrochemical Extraction of Fe–Si Alloy Form SiO2–CaO–CaF2–FeOx Slags by Molten Oxide Electrolysis

Electrochemical Extraction of Fe–Si Alloy Form SiO2–CaO–CaF2–FeOx Slags by Molten Oxide Electrolysis

Crystallization Behavior of the CaO–SiO2–Al2O3–MgO System Inclusions

The crystallization process of low melting point CaO–SiO2–Al2O3–MgO system inclusions during the continuous casting and hot rolling process greatly affects the deformability of inclusions. The effect of Al2O3 and MgO contents on the crystallization characteristics of CaO–SiO2–Al2O3–MgO system melts representing the typical oxide inclusions in Si–Mn deoxidized steels is systematically investigated. The continuous cooling transformation and time–temperature transformation experiments are carried out. The results reveal that the increase of Al2O3 contents restrains the crystallization process of the melt, whereas the crystallization tendency of the melt is promoted with the increase of MgO contents. The precipitated phases are predominately 2CaO·MgO·2SiO2 and 3CaO·MgO·2SiO2, and the primary crystalline phase is unaffected by the changes of Al2O3 and MgO contents. To obtain low melting point plasticized inclusions with limited crystallization ability, it is recommended to control the Al2O3 and MgO contents greater than 15 wt% and below 5 wt%, respectively. The isothermal treatment is suggested to be controlled within a proper temperature range (1175–1250 °C) to decrease the crystallization kinetics. The oxide system's viscosity change is the limiting kinetic factor in the crystallization process, and it can be utilized to predict the system's crystallization tendency.

Phase equilibria in the low-TiO2 part of the CaO–MgO–SiO2–Al2O3–TiO2 system at a fixed MgO/CaO mass ratio of 0.2 and Al2O3/SiO2 mass ratio of 0.4

Adding titanium oxide has become a common practice in modern blast furnace operating procedures. The blast furnace slag is based on the CaO–MgO–Al2O3–SiO2–TiO2 low titanium slag system rather than CaO–MgO–Al2O3–SiO2 system. Phase equilibria in the CaO–SiO2–Al2O3–MgO–TiO2 system in the low-TiO2 part have been experimentally determined by means of high temperature equilibration and quenching technique followed by electron probe X-ray microanalysis. Introducing a small quantity of titanium-bearing materials can lower the liquidus temperature. The TiO2 content in the slag should be controlled below 4.6 wt%, otherwise it will enter the perovskite phase region where the liquidus temperatures increases rapidly. The compositions of the solid solutions corresponding to the liquidus have been precisely measured and should be utilized for developing the thermodynamic database.

Effect of CaO–SiO2–MgO–CaF2 slags on deep deoxidation and desulphurisation of low-Ni 201 stainless steel by simultaneous consideration of multiple slag–steel reactions

Effect of CaO–SiO₂–MgO–CaF₂ slags on deep deoxidation and desulphurisation of low-Ni 201 stainless steel by simultaneous consideration of multiple slag–steel reactions

Effect of the Al2O3 Content and MgO/Al2O3 Ratio on the Viscosity and Structure of CaO–SiO2–MgO–Al2O3-Based Furnace Slag with CaO/SiO2 = 1.2

Effect of the Al2O3 Content and MgO/Al2O3 Ratio on the Viscosity and Structure of CaO–SiO2–MgO–Al2O3-Based Furnace Slag with CaO/SiO2 = 1.2

Thermophysical properties, crystallization behavior and structure of CaO–SiO2–MgO–Al2O3–TiO2–FeO slag with varying TiO2 contents

This study investigated the effect of TiO2 content on the viscosity, free running temperature, electrical conductivity, crystallization behavior, and structure of high-titanium CaO–SiO2-10 wt% MgO-13 wt%Al2O3–TiO2-4 wt.% FeO slag by experiments and molecular dynamics simulations. The results revealed that increasing TiO2 weakened the overall bonding energy and simplified the slag structure, leading to a decrease in viscosity and an increase in electrical conductivity. Thermodynamic calculations revealed a continuous enrichment of the slag towards the pseudobrookite region with increasing TiO2 content. The precipitation of pseudobrookite phase during cooling resulted in short-slag characteristics and a rising free running temperature. Additionally, the peak intensity of pseudobrookite phase gradually enhanced and its morphology changed from elongated strips to plates with higher TiO2 concentration. Structural analysis demonstrated that the poorly stabilized [TiO6] octahedron was the major form of Ti atoms in the slag, and its proportion progressively increased with increasing TiO2 content.

Superior comprehensive performance CaO‐based core achieved by optimizing particle gradation via orthogonal experiments

AbstractThe effect of CaCO3 particle size on the viscosity of slurry, phase formation, microstructural evolution, and performances of the water‐soluble CaO‐based ceramic core sintered at different temperatures was systematically investigated and discussed, and the particle gradation orthogonal experiments were used to adjust flexural strength, water‐soluble rate, shrinkage rate, apparent porosity, and hygroscopicity rate. The results showed that the finer particle size increased the effective contact area between CaO and SiO2, which promoted the generation of CaO–SiO2 system phase and the dense microstructure in the sintered CaO‐based cores. The higher sintering resulted in dense microstructure. The optimal gradation scheme included 28 wt.%, 56 wt.%, and 16 wt.% CaCO3 powder with D50 = 11.0 µm, 6.17 µm, and 4.62 µm, respectively, and the resulting flexural strength was 9.57 MPa, water‐soluble rate was 65.37 g/h in 60°C water, shrinkage rate was 8.62%, porosity rate was 38.85%, presenting a well‐balanced comprehensive performance, which is significant for the complex internal castings.